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/signalvar.h> 67 #include <sys/socket.h> 68 #include <sys/socketvar.h> 69 #include <sys/sysctl.h> 70 #include <sys/syslog.h> 71 #include <sys/systm.h> 72 73 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 74 75 #include <vm/uma.h> 76 77 #include <net/if.h> 78 #include <net/route.h> 79 #include <net/vnet.h> 80 81 #define TCPSTATES /* for logging */ 82 83 #include <netinet/cc.h> 84 #include <netinet/in.h> 85 #include <netinet/in_pcb.h> 86 #include <netinet/in_systm.h> 87 #include <netinet/in_var.h> 88 #include <netinet/ip.h> 89 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 90 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 91 #include <netinet/ip_var.h> 92 #include <netinet/ip_options.h> 93 #include <netinet/ip6.h> 94 #include <netinet/icmp6.h> 95 #include <netinet6/in6_pcb.h> 96 #include <netinet6/ip6_var.h> 97 #include <netinet6/nd6.h> 98 #include <netinet/tcp_fsm.h> 99 #include <netinet/tcp_seq.h> 100 #include <netinet/tcp_timer.h> 101 #include <netinet/tcp_var.h> 102 #include <netinet6/tcp6_var.h> 103 #include <netinet/tcpip.h> 104 #include <netinet/tcp_syncache.h> 105 #ifdef TCPDEBUG 106 #include <netinet/tcp_debug.h> 107 #endif /* TCPDEBUG */ 108 #ifdef TCP_OFFLOAD 109 #include <netinet/tcp_offload.h> 110 #endif 111 112 #ifdef IPSEC 113 #include <netipsec/ipsec.h> 114 #include <netipsec/ipsec6.h> 115 #endif /*IPSEC*/ 116 117 #include <machine/in_cksum.h> 118 119 #include <security/mac/mac_framework.h> 120 121 const int tcprexmtthresh = 3; 122 123 VNET_DEFINE(struct tcpstat, tcpstat); 124 SYSCTL_VNET_STRUCT(_net_inet_tcp, TCPCTL_STATS, stats, CTLFLAG_RW, 125 &VNET_NAME(tcpstat), tcpstat, 126 "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 127 128 int tcp_log_in_vain = 0; 129 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 130 &tcp_log_in_vain, 0, 131 "Log all incoming TCP segments to closed ports"); 132 133 VNET_DEFINE(int, blackhole) = 0; 134 #define V_blackhole VNET(blackhole) 135 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_RW, 136 &VNET_NAME(blackhole), 0, 137 "Do not send RST on segments to closed ports"); 138 139 VNET_DEFINE(int, tcp_delack_enabled) = 1; 140 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_RW, 141 &VNET_NAME(tcp_delack_enabled), 0, 142 "Delay ACK to try and piggyback it onto a data packet"); 143 144 VNET_DEFINE(int, drop_synfin) = 0; 145 #define V_drop_synfin VNET(drop_synfin) 146 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_RW, 147 &VNET_NAME(drop_synfin), 0, 148 "Drop TCP packets with SYN+FIN set"); 149 150 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 151 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 152 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_RW, 153 &VNET_NAME(tcp_do_rfc3042), 0, 154 "Enable RFC 3042 (Limited Transmit)"); 155 156 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 157 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_RW, 158 &VNET_NAME(tcp_do_rfc3390), 0, 159 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 160 161 SYSCTL_NODE(_net_inet_tcp, OID_AUTO, experimental, CTLFLAG_RW, 0, 162 "Experimental TCP extensions"); 163 164 VNET_DEFINE(int, tcp_do_initcwnd10) = 1; 165 SYSCTL_VNET_INT(_net_inet_tcp_experimental, OID_AUTO, initcwnd10, CTLFLAG_RW, 166 &VNET_NAME(tcp_do_initcwnd10), 0, 167 "Enable draft-ietf-tcpm-initcwnd-05 (Increasing initial CWND to 10)"); 168 169 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 170 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_RW, 171 &VNET_NAME(tcp_do_rfc3465), 0, 172 "Enable RFC 3465 (Appropriate Byte Counting)"); 173 174 VNET_DEFINE(int, tcp_abc_l_var) = 2; 175 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_RW, 176 &VNET_NAME(tcp_abc_l_var), 2, 177 "Cap the max cwnd increment during slow-start to this number of segments"); 178 179 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 180 181 VNET_DEFINE(int, tcp_do_ecn) = 0; 182 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_RW, 183 &VNET_NAME(tcp_do_ecn), 0, 184 "TCP ECN support"); 185 186 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 187 SYSCTL_VNET_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_RW, 188 &VNET_NAME(tcp_ecn_maxretries), 0, 189 "Max retries before giving up on ECN"); 190 191 VNET_DEFINE(int, tcp_insecure_rst) = 0; 192 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 193 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_RW, 194 &VNET_NAME(tcp_insecure_rst), 0, 195 "Follow the old (insecure) criteria for accepting RST packets"); 196 197 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 198 #define V_tcp_recvspace VNET(tcp_recvspace) 199 SYSCTL_VNET_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_RW, 200 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 201 202 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 203 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 204 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_RW, 205 &VNET_NAME(tcp_do_autorcvbuf), 0, 206 "Enable automatic receive buffer sizing"); 207 208 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 209 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 210 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_RW, 211 &VNET_NAME(tcp_autorcvbuf_inc), 0, 212 "Incrementor step size of automatic receive buffer"); 213 214 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 215 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 216 SYSCTL_VNET_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_RW, 217 &VNET_NAME(tcp_autorcvbuf_max), 0, 218 "Max size of automatic receive buffer"); 219 220 VNET_DEFINE(struct inpcbhead, tcb); 221 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 222 VNET_DEFINE(struct inpcbinfo, tcbinfo); 223 224 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 225 static void tcp_do_segment(struct mbuf *, struct tcphdr *, 226 struct socket *, struct tcpcb *, int, int, uint8_t, 227 int); 228 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 229 struct tcpcb *, int, int); 230 static void tcp_pulloutofband(struct socket *, 231 struct tcphdr *, struct mbuf *, int); 232 static void tcp_xmit_timer(struct tcpcb *, int); 233 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 234 static void inline tcp_fields_to_host(struct tcphdr *); 235 #ifdef TCP_SIGNATURE 236 static void inline tcp_fields_to_net(struct tcphdr *); 237 static int inline tcp_signature_verify_input(struct mbuf *, int, int, 238 int, struct tcpopt *, struct tcphdr *, u_int); 239 #endif 240 static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th, 241 uint16_t type); 242 static void inline cc_conn_init(struct tcpcb *tp); 243 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th); 244 static void inline hhook_run_tcp_est_in(struct tcpcb *tp, 245 struct tcphdr *th, struct tcpopt *to); 246 247 /* 248 * Kernel module interface for updating tcpstat. The argument is an index 249 * into tcpstat treated as an array of u_long. While this encodes the 250 * general layout of tcpstat into the caller, it doesn't encode its location, 251 * so that future changes to add, for example, per-CPU stats support won't 252 * cause binary compatibility problems for kernel modules. 253 */ 254 void 255 kmod_tcpstat_inc(int statnum) 256 { 257 258 (*((u_long *)&V_tcpstat + statnum))++; 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 == min(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 * Draft-ietf-tcpm-initcwnd-05 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 static inline void 453 tcp_fields_to_host(struct tcphdr *th) 454 { 455 456 th->th_seq = ntohl(th->th_seq); 457 th->th_ack = ntohl(th->th_ack); 458 th->th_win = ntohs(th->th_win); 459 th->th_urp = ntohs(th->th_urp); 460 } 461 462 #ifdef TCP_SIGNATURE 463 static inline void 464 tcp_fields_to_net(struct tcphdr *th) 465 { 466 467 th->th_seq = htonl(th->th_seq); 468 th->th_ack = htonl(th->th_ack); 469 th->th_win = htons(th->th_win); 470 th->th_urp = htons(th->th_urp); 471 } 472 473 static inline int 474 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 475 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 476 { 477 int ret; 478 479 tcp_fields_to_net(th); 480 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 481 tcp_fields_to_host(th); 482 return (ret); 483 } 484 #endif 485 486 /* Neighbor Discovery, Neighbor Unreachability Detection Upper layer hint. */ 487 #ifdef INET6 488 #define ND6_HINT(tp) \ 489 do { \ 490 if ((tp) && (tp)->t_inpcb && \ 491 ((tp)->t_inpcb->inp_vflag & INP_IPV6) != 0) \ 492 nd6_nud_hint(NULL, NULL, 0); \ 493 } while (0) 494 #else 495 #define ND6_HINT(tp) 496 #endif 497 498 /* 499 * Indicate whether this ack should be delayed. We can delay the ack if 500 * - there is no delayed ack timer in progress and 501 * - our last ack wasn't a 0-sized window. We never want to delay 502 * the ack that opens up a 0-sized window and 503 * - delayed acks are enabled or 504 * - this is a half-synchronized T/TCP connection. 505 */ 506 #define DELAY_ACK(tp) \ 507 ((!tcp_timer_active(tp, TT_DELACK) && \ 508 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 509 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 510 511 /* 512 * TCP input handling is split into multiple parts: 513 * tcp6_input is a thin wrapper around tcp_input for the extended 514 * ip6_protox[] call format in ip6_input 515 * tcp_input handles primary segment validation, inpcb lookup and 516 * SYN processing on listen sockets 517 * tcp_do_segment processes the ACK and text of the segment for 518 * establishing, established and closing connections 519 */ 520 #ifdef INET6 521 int 522 tcp6_input(struct mbuf **mp, int *offp, int proto) 523 { 524 struct mbuf *m = *mp; 525 struct in6_ifaddr *ia6; 526 527 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 528 529 /* 530 * draft-itojun-ipv6-tcp-to-anycast 531 * better place to put this in? 532 */ 533 ia6 = ip6_getdstifaddr(m); 534 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 535 struct ip6_hdr *ip6; 536 537 ifa_free(&ia6->ia_ifa); 538 ip6 = mtod(m, struct ip6_hdr *); 539 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 540 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 541 return IPPROTO_DONE; 542 } 543 if (ia6) 544 ifa_free(&ia6->ia_ifa); 545 546 tcp_input(m, *offp); 547 return IPPROTO_DONE; 548 } 549 #endif /* INET6 */ 550 551 void 552 tcp_input(struct mbuf *m, int off0) 553 { 554 struct tcphdr *th = NULL; 555 struct ip *ip = NULL; 556 struct inpcb *inp = NULL; 557 struct tcpcb *tp = NULL; 558 struct socket *so = NULL; 559 u_char *optp = NULL; 560 int optlen = 0; 561 #ifdef INET 562 int len; 563 #endif 564 int tlen = 0, off; 565 int drop_hdrlen; 566 int thflags; 567 int rstreason = 0; /* For badport_bandlim accounting purposes */ 568 #ifdef TCP_SIGNATURE 569 uint8_t sig_checked = 0; 570 #endif 571 uint8_t iptos = 0; 572 struct m_tag *fwd_tag = NULL; 573 #ifdef INET6 574 struct ip6_hdr *ip6 = NULL; 575 int isipv6; 576 #else 577 const void *ip6 = NULL; 578 #endif /* INET6 */ 579 struct tcpopt to; /* options in this segment */ 580 char *s = NULL; /* address and port logging */ 581 int ti_locked; 582 #define TI_UNLOCKED 1 583 #define TI_WLOCKED 2 584 585 #ifdef TCPDEBUG 586 /* 587 * The size of tcp_saveipgen must be the size of the max ip header, 588 * now IPv6. 589 */ 590 u_char tcp_saveipgen[IP6_HDR_LEN]; 591 struct tcphdr tcp_savetcp; 592 short ostate = 0; 593 #endif 594 595 #ifdef INET6 596 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 597 #endif 598 599 to.to_flags = 0; 600 TCPSTAT_INC(tcps_rcvtotal); 601 602 #ifdef INET6 603 if (isipv6) { 604 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 605 606 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 607 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 608 if (m == NULL) { 609 TCPSTAT_INC(tcps_rcvshort); 610 return; 611 } 612 } 613 614 ip6 = mtod(m, struct ip6_hdr *); 615 th = (struct tcphdr *)((caddr_t)ip6 + off0); 616 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 617 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 618 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 619 th->th_sum = m->m_pkthdr.csum_data; 620 else 621 th->th_sum = in6_cksum_pseudo(ip6, tlen, 622 IPPROTO_TCP, m->m_pkthdr.csum_data); 623 th->th_sum ^= 0xffff; 624 } else 625 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 626 if (th->th_sum) { 627 TCPSTAT_INC(tcps_rcvbadsum); 628 goto drop; 629 } 630 631 /* 632 * Be proactive about unspecified IPv6 address in source. 633 * As we use all-zero to indicate unbounded/unconnected pcb, 634 * unspecified IPv6 address can be used to confuse us. 635 * 636 * Note that packets with unspecified IPv6 destination is 637 * already dropped in ip6_input. 638 */ 639 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 640 /* XXX stat */ 641 goto drop; 642 } 643 } 644 #endif 645 #if defined(INET) && defined(INET6) 646 else 647 #endif 648 #ifdef INET 649 { 650 /* 651 * Get IP and TCP header together in first mbuf. 652 * Note: IP leaves IP header in first mbuf. 653 */ 654 if (off0 > sizeof (struct ip)) { 655 ip_stripoptions(m); 656 off0 = sizeof(struct ip); 657 } 658 if (m->m_len < sizeof (struct tcpiphdr)) { 659 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 660 == NULL) { 661 TCPSTAT_INC(tcps_rcvshort); 662 return; 663 } 664 } 665 ip = mtod(m, struct ip *); 666 th = (struct tcphdr *)((caddr_t)ip + off0); 667 tlen = ntohs(ip->ip_len) - off0; 668 669 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 670 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 671 th->th_sum = m->m_pkthdr.csum_data; 672 else 673 th->th_sum = in_pseudo(ip->ip_src.s_addr, 674 ip->ip_dst.s_addr, 675 htonl(m->m_pkthdr.csum_data + tlen + 676 IPPROTO_TCP)); 677 th->th_sum ^= 0xffff; 678 } else { 679 struct ipovly *ipov = (struct ipovly *)ip; 680 681 /* 682 * Checksum extended TCP header and data. 683 */ 684 len = off0 + tlen; 685 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 686 ipov->ih_len = htons(tlen); 687 th->th_sum = in_cksum(m, len); 688 } 689 if (th->th_sum) { 690 TCPSTAT_INC(tcps_rcvbadsum); 691 goto drop; 692 } 693 /* Re-initialization for later version check */ 694 ip->ip_v = IPVERSION; 695 } 696 #endif /* INET */ 697 698 #ifdef INET6 699 if (isipv6) 700 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 701 #endif 702 #if defined(INET) && defined(INET6) 703 else 704 #endif 705 #ifdef INET 706 iptos = ip->ip_tos; 707 #endif 708 709 /* 710 * Check that TCP offset makes sense, 711 * pull out TCP options and adjust length. XXX 712 */ 713 off = th->th_off << 2; 714 if (off < sizeof (struct tcphdr) || off > tlen) { 715 TCPSTAT_INC(tcps_rcvbadoff); 716 goto drop; 717 } 718 tlen -= off; /* tlen is used instead of ti->ti_len */ 719 if (off > sizeof (struct tcphdr)) { 720 #ifdef INET6 721 if (isipv6) { 722 IP6_EXTHDR_CHECK(m, off0, off, ); 723 ip6 = mtod(m, struct ip6_hdr *); 724 th = (struct tcphdr *)((caddr_t)ip6 + off0); 725 } 726 #endif 727 #if defined(INET) && defined(INET6) 728 else 729 #endif 730 #ifdef INET 731 { 732 if (m->m_len < sizeof(struct ip) + off) { 733 if ((m = m_pullup(m, sizeof (struct ip) + off)) 734 == NULL) { 735 TCPSTAT_INC(tcps_rcvshort); 736 return; 737 } 738 ip = mtod(m, struct ip *); 739 th = (struct tcphdr *)((caddr_t)ip + off0); 740 } 741 } 742 #endif 743 optlen = off - sizeof (struct tcphdr); 744 optp = (u_char *)(th + 1); 745 } 746 thflags = th->th_flags; 747 748 /* 749 * Convert TCP protocol specific fields to host format. 750 */ 751 tcp_fields_to_host(th); 752 753 /* 754 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 755 */ 756 drop_hdrlen = off0 + off; 757 758 /* 759 * Locate pcb for segment; if we're likely to add or remove a 760 * connection then first acquire pcbinfo lock. There are two cases 761 * where we might discover later we need a write lock despite the 762 * flags: ACKs moving a connection out of the syncache, and ACKs for 763 * a connection in TIMEWAIT. 764 */ 765 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) { 766 INP_INFO_WLOCK(&V_tcbinfo); 767 ti_locked = TI_WLOCKED; 768 } else 769 ti_locked = TI_UNLOCKED; 770 771 findpcb: 772 #ifdef INVARIANTS 773 if (ti_locked == TI_WLOCKED) { 774 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 775 } else { 776 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 777 } 778 #endif 779 780 /* 781 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 782 */ 783 if ( 784 #ifdef INET6 785 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 786 #ifdef INET 787 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 788 #endif 789 #endif 790 #if defined(INET) && !defined(INET6) 791 (m->m_flags & M_IP_NEXTHOP) 792 #endif 793 ) 794 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 795 796 #ifdef INET6 797 if (isipv6 && fwd_tag != NULL) { 798 struct sockaddr_in6 *next_hop6; 799 800 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 801 /* 802 * Transparently forwarded. Pretend to be the destination. 803 * Already got one like this? 804 */ 805 inp = in6_pcblookup_mbuf(&V_tcbinfo, 806 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 807 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 808 if (!inp) { 809 /* 810 * It's new. Try to find the ambushing socket. 811 * Because we've rewritten the destination address, 812 * any hardware-generated hash is ignored. 813 */ 814 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 815 th->th_sport, &next_hop6->sin6_addr, 816 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 817 th->th_dport, INPLOOKUP_WILDCARD | 818 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 819 } 820 /* Remove the tag from the packet. We don't need it anymore. */ 821 m_tag_delete(m, fwd_tag); 822 m->m_flags &= ~M_IP6_NEXTHOP; 823 fwd_tag = NULL; 824 } else if (isipv6) { 825 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 826 th->th_sport, &ip6->ip6_dst, th->th_dport, 827 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 828 m->m_pkthdr.rcvif, m); 829 } 830 #endif /* INET6 */ 831 #if defined(INET6) && defined(INET) 832 else 833 #endif 834 #ifdef INET 835 if (fwd_tag != NULL) { 836 struct sockaddr_in *next_hop; 837 838 next_hop = (struct sockaddr_in *)(fwd_tag+1); 839 /* 840 * Transparently forwarded. Pretend to be the destination. 841 * already got one like this? 842 */ 843 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 844 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 845 m->m_pkthdr.rcvif, m); 846 if (!inp) { 847 /* 848 * It's new. Try to find the ambushing socket. 849 * Because we've rewritten the destination address, 850 * any hardware-generated hash is ignored. 851 */ 852 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 853 th->th_sport, next_hop->sin_addr, 854 next_hop->sin_port ? ntohs(next_hop->sin_port) : 855 th->th_dport, INPLOOKUP_WILDCARD | 856 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 857 } 858 /* Remove the tag from the packet. We don't need it anymore. */ 859 m_tag_delete(m, fwd_tag); 860 m->m_flags &= ~M_IP_NEXTHOP; 861 fwd_tag = NULL; 862 } else 863 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 864 th->th_sport, ip->ip_dst, th->th_dport, 865 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 866 m->m_pkthdr.rcvif, m); 867 #endif /* INET */ 868 869 /* 870 * If the INPCB does not exist then all data in the incoming 871 * segment is discarded and an appropriate RST is sent back. 872 * XXX MRT Send RST using which routing table? 873 */ 874 if (inp == NULL) { 875 /* 876 * Log communication attempts to ports that are not 877 * in use. 878 */ 879 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 880 tcp_log_in_vain == 2) { 881 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 882 log(LOG_INFO, "%s; %s: Connection attempt " 883 "to closed port\n", s, __func__); 884 } 885 /* 886 * When blackholing do not respond with a RST but 887 * completely ignore the segment and drop it. 888 */ 889 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 890 V_blackhole == 2) 891 goto dropunlock; 892 893 rstreason = BANDLIM_RST_CLOSEDPORT; 894 goto dropwithreset; 895 } 896 INP_WLOCK_ASSERT(inp); 897 if (!(inp->inp_flags & INP_HW_FLOWID) 898 && (m->m_flags & M_FLOWID) 899 && ((inp->inp_socket == NULL) 900 || !(inp->inp_socket->so_options & SO_ACCEPTCONN))) { 901 inp->inp_flags |= INP_HW_FLOWID; 902 inp->inp_flags &= ~INP_SW_FLOWID; 903 inp->inp_flowid = m->m_pkthdr.flowid; 904 } 905 #ifdef IPSEC 906 #ifdef INET6 907 if (isipv6 && ipsec6_in_reject(m, inp)) { 908 V_ipsec6stat.in_polvio++; 909 goto dropunlock; 910 } else 911 #endif /* INET6 */ 912 if (ipsec4_in_reject(m, inp) != 0) { 913 V_ipsec4stat.in_polvio++; 914 goto dropunlock; 915 } 916 #endif /* IPSEC */ 917 918 /* 919 * Check the minimum TTL for socket. 920 */ 921 if (inp->inp_ip_minttl != 0) { 922 #ifdef INET6 923 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 924 goto dropunlock; 925 else 926 #endif 927 if (inp->inp_ip_minttl > ip->ip_ttl) 928 goto dropunlock; 929 } 930 931 /* 932 * A previous connection in TIMEWAIT state is supposed to catch stray 933 * or duplicate segments arriving late. If this segment was a 934 * legitimate new connection attempt, the old INPCB gets removed and 935 * we can try again to find a listening socket. 936 * 937 * At this point, due to earlier optimism, we may hold only an inpcb 938 * lock, and not the inpcbinfo write lock. If so, we need to try to 939 * acquire it, or if that fails, acquire a reference on the inpcb, 940 * drop all locks, acquire a global write lock, and then re-acquire 941 * the inpcb lock. We may at that point discover that another thread 942 * has tried to free the inpcb, in which case we need to loop back 943 * and try to find a new inpcb to deliver to. 944 * 945 * XXXRW: It may be time to rethink timewait locking. 946 */ 947 relocked: 948 if (inp->inp_flags & INP_TIMEWAIT) { 949 if (ti_locked == TI_UNLOCKED) { 950 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { 951 in_pcbref(inp); 952 INP_WUNLOCK(inp); 953 INP_INFO_WLOCK(&V_tcbinfo); 954 ti_locked = TI_WLOCKED; 955 INP_WLOCK(inp); 956 if (in_pcbrele_wlocked(inp)) { 957 inp = NULL; 958 goto findpcb; 959 } 960 } else 961 ti_locked = TI_WLOCKED; 962 } 963 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 964 965 if (thflags & TH_SYN) 966 tcp_dooptions(&to, optp, optlen, TO_SYN); 967 /* 968 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 969 */ 970 if (tcp_twcheck(inp, &to, th, m, tlen)) 971 goto findpcb; 972 INP_INFO_WUNLOCK(&V_tcbinfo); 973 return; 974 } 975 /* 976 * The TCPCB may no longer exist if the connection is winding 977 * down or it is in the CLOSED state. Either way we drop the 978 * segment and send an appropriate response. 979 */ 980 tp = intotcpcb(inp); 981 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 982 rstreason = BANDLIM_RST_CLOSEDPORT; 983 goto dropwithreset; 984 } 985 986 #ifdef TCP_OFFLOAD 987 if (tp->t_flags & TF_TOE) { 988 tcp_offload_input(tp, m); 989 m = NULL; /* consumed by the TOE driver */ 990 goto dropunlock; 991 } 992 #endif 993 994 /* 995 * We've identified a valid inpcb, but it could be that we need an 996 * inpcbinfo write lock but don't hold it. In this case, attempt to 997 * acquire using the same strategy as the TIMEWAIT case above. If we 998 * relock, we have to jump back to 'relocked' as the connection might 999 * now be in TIMEWAIT. 1000 */ 1001 #ifdef INVARIANTS 1002 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0) 1003 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1004 #endif 1005 if (tp->t_state != TCPS_ESTABLISHED) { 1006 if (ti_locked == TI_UNLOCKED) { 1007 if (INP_INFO_TRY_WLOCK(&V_tcbinfo) == 0) { 1008 in_pcbref(inp); 1009 INP_WUNLOCK(inp); 1010 INP_INFO_WLOCK(&V_tcbinfo); 1011 ti_locked = TI_WLOCKED; 1012 INP_WLOCK(inp); 1013 if (in_pcbrele_wlocked(inp)) { 1014 inp = NULL; 1015 goto findpcb; 1016 } 1017 goto relocked; 1018 } else 1019 ti_locked = TI_WLOCKED; 1020 } 1021 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1022 } 1023 1024 #ifdef MAC 1025 INP_WLOCK_ASSERT(inp); 1026 if (mac_inpcb_check_deliver(inp, m)) 1027 goto dropunlock; 1028 #endif 1029 so = inp->inp_socket; 1030 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1031 #ifdef TCPDEBUG 1032 if (so->so_options & SO_DEBUG) { 1033 ostate = tp->t_state; 1034 #ifdef INET6 1035 if (isipv6) { 1036 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1037 } else 1038 #endif 1039 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1040 tcp_savetcp = *th; 1041 } 1042 #endif /* TCPDEBUG */ 1043 /* 1044 * When the socket is accepting connections (the INPCB is in LISTEN 1045 * state) we look into the SYN cache if this is a new connection 1046 * attempt or the completion of a previous one. Because listen 1047 * sockets are never in TCPS_ESTABLISHED, the V_tcbinfo lock will be 1048 * held in this case. 1049 */ 1050 if (so->so_options & SO_ACCEPTCONN) { 1051 struct in_conninfo inc; 1052 1053 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 1054 "tp not listening", __func__)); 1055 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1056 1057 bzero(&inc, sizeof(inc)); 1058 #ifdef INET6 1059 if (isipv6) { 1060 inc.inc_flags |= INC_ISIPV6; 1061 inc.inc6_faddr = ip6->ip6_src; 1062 inc.inc6_laddr = ip6->ip6_dst; 1063 } else 1064 #endif 1065 { 1066 inc.inc_faddr = ip->ip_src; 1067 inc.inc_laddr = ip->ip_dst; 1068 } 1069 inc.inc_fport = th->th_sport; 1070 inc.inc_lport = th->th_dport; 1071 inc.inc_fibnum = so->so_fibnum; 1072 1073 /* 1074 * Check for an existing connection attempt in syncache if 1075 * the flag is only ACK. A successful lookup creates a new 1076 * socket appended to the listen queue in SYN_RECEIVED state. 1077 */ 1078 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1079 /* 1080 * Parse the TCP options here because 1081 * syncookies need access to the reflected 1082 * timestamp. 1083 */ 1084 tcp_dooptions(&to, optp, optlen, 0); 1085 /* 1086 * NB: syncache_expand() doesn't unlock 1087 * inp and tcpinfo locks. 1088 */ 1089 if (!syncache_expand(&inc, &to, th, &so, m)) { 1090 /* 1091 * No syncache entry or ACK was not 1092 * for our SYN/ACK. Send a RST. 1093 * NB: syncache did its own logging 1094 * of the failure cause. 1095 */ 1096 rstreason = BANDLIM_RST_OPENPORT; 1097 goto dropwithreset; 1098 } 1099 if (so == NULL) { 1100 /* 1101 * We completed the 3-way handshake 1102 * but could not allocate a socket 1103 * either due to memory shortage, 1104 * listen queue length limits or 1105 * global socket limits. Send RST 1106 * or wait and have the remote end 1107 * retransmit the ACK for another 1108 * try. 1109 */ 1110 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1111 log(LOG_DEBUG, "%s; %s: Listen socket: " 1112 "Socket allocation failed due to " 1113 "limits or memory shortage, %s\n", 1114 s, __func__, 1115 V_tcp_sc_rst_sock_fail ? 1116 "sending RST" : "try again"); 1117 if (V_tcp_sc_rst_sock_fail) { 1118 rstreason = BANDLIM_UNLIMITED; 1119 goto dropwithreset; 1120 } else 1121 goto dropunlock; 1122 } 1123 /* 1124 * Socket is created in state SYN_RECEIVED. 1125 * Unlock the listen socket, lock the newly 1126 * created socket and update the tp variable. 1127 */ 1128 INP_WUNLOCK(inp); /* listen socket */ 1129 inp = sotoinpcb(so); 1130 INP_WLOCK(inp); /* new connection */ 1131 tp = intotcpcb(inp); 1132 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1133 ("%s: ", __func__)); 1134 #ifdef TCP_SIGNATURE 1135 if (sig_checked == 0) { 1136 tcp_dooptions(&to, optp, optlen, 1137 (thflags & TH_SYN) ? TO_SYN : 0); 1138 if (!tcp_signature_verify_input(m, off0, tlen, 1139 optlen, &to, th, tp->t_flags)) { 1140 1141 /* 1142 * In SYN_SENT state if it receives an 1143 * RST, it is allowed for further 1144 * processing. 1145 */ 1146 if ((thflags & TH_RST) == 0 || 1147 (tp->t_state == TCPS_SYN_SENT) == 0) 1148 goto dropunlock; 1149 } 1150 sig_checked = 1; 1151 } 1152 #endif 1153 1154 /* 1155 * Process the segment and the data it 1156 * contains. tcp_do_segment() consumes 1157 * the mbuf chain and unlocks the inpcb. 1158 */ 1159 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1160 iptos, ti_locked); 1161 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1162 return; 1163 } 1164 /* 1165 * Segment flag validation for new connection attempts: 1166 * 1167 * Our (SYN|ACK) response was rejected. 1168 * Check with syncache and remove entry to prevent 1169 * retransmits. 1170 * 1171 * NB: syncache_chkrst does its own logging of failure 1172 * causes. 1173 */ 1174 if (thflags & TH_RST) { 1175 syncache_chkrst(&inc, th); 1176 goto dropunlock; 1177 } 1178 /* 1179 * We can't do anything without SYN. 1180 */ 1181 if ((thflags & TH_SYN) == 0) { 1182 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1183 log(LOG_DEBUG, "%s; %s: Listen socket: " 1184 "SYN is missing, segment ignored\n", 1185 s, __func__); 1186 TCPSTAT_INC(tcps_badsyn); 1187 goto dropunlock; 1188 } 1189 /* 1190 * (SYN|ACK) is bogus on a listen socket. 1191 */ 1192 if (thflags & TH_ACK) { 1193 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1194 log(LOG_DEBUG, "%s; %s: Listen socket: " 1195 "SYN|ACK invalid, segment rejected\n", 1196 s, __func__); 1197 syncache_badack(&inc); /* XXX: Not needed! */ 1198 TCPSTAT_INC(tcps_badsyn); 1199 rstreason = BANDLIM_RST_OPENPORT; 1200 goto dropwithreset; 1201 } 1202 /* 1203 * If the drop_synfin option is enabled, drop all 1204 * segments with both the SYN and FIN bits set. 1205 * This prevents e.g. nmap from identifying the 1206 * TCP/IP stack. 1207 * XXX: Poor reasoning. nmap has other methods 1208 * and is constantly refining its stack detection 1209 * strategies. 1210 * XXX: This is a violation of the TCP specification 1211 * and was used by RFC1644. 1212 */ 1213 if ((thflags & TH_FIN) && V_drop_synfin) { 1214 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1215 log(LOG_DEBUG, "%s; %s: Listen socket: " 1216 "SYN|FIN segment ignored (based on " 1217 "sysctl setting)\n", s, __func__); 1218 TCPSTAT_INC(tcps_badsyn); 1219 goto dropunlock; 1220 } 1221 /* 1222 * Segment's flags are (SYN) or (SYN|FIN). 1223 * 1224 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1225 * as they do not affect the state of the TCP FSM. 1226 * The data pointed to by TH_URG and th_urp is ignored. 1227 */ 1228 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1229 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1230 KASSERT(thflags & (TH_SYN), 1231 ("%s: Listen socket: TH_SYN not set", __func__)); 1232 #ifdef INET6 1233 /* 1234 * If deprecated address is forbidden, 1235 * we do not accept SYN to deprecated interface 1236 * address to prevent any new inbound connection from 1237 * getting established. 1238 * When we do not accept SYN, we send a TCP RST, 1239 * with deprecated source address (instead of dropping 1240 * it). We compromise it as it is much better for peer 1241 * to send a RST, and RST will be the final packet 1242 * for the exchange. 1243 * 1244 * If we do not forbid deprecated addresses, we accept 1245 * the SYN packet. RFC2462 does not suggest dropping 1246 * SYN in this case. 1247 * If we decipher RFC2462 5.5.4, it says like this: 1248 * 1. use of deprecated addr with existing 1249 * communication is okay - "SHOULD continue to be 1250 * used" 1251 * 2. use of it with new communication: 1252 * (2a) "SHOULD NOT be used if alternate address 1253 * with sufficient scope is available" 1254 * (2b) nothing mentioned otherwise. 1255 * Here we fall into (2b) case as we have no choice in 1256 * our source address selection - we must obey the peer. 1257 * 1258 * The wording in RFC2462 is confusing, and there are 1259 * multiple description text for deprecated address 1260 * handling - worse, they are not exactly the same. 1261 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1262 */ 1263 if (isipv6 && !V_ip6_use_deprecated) { 1264 struct in6_ifaddr *ia6; 1265 1266 ia6 = ip6_getdstifaddr(m); 1267 if (ia6 != NULL && 1268 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1269 ifa_free(&ia6->ia_ifa); 1270 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1271 log(LOG_DEBUG, "%s; %s: Listen socket: " 1272 "Connection attempt to deprecated " 1273 "IPv6 address rejected\n", 1274 s, __func__); 1275 rstreason = BANDLIM_RST_OPENPORT; 1276 goto dropwithreset; 1277 } 1278 if (ia6) 1279 ifa_free(&ia6->ia_ifa); 1280 } 1281 #endif /* INET6 */ 1282 /* 1283 * Basic sanity checks on incoming SYN requests: 1284 * Don't respond if the destination is a link layer 1285 * broadcast according to RFC1122 4.2.3.10, p. 104. 1286 * If it is from this socket it must be forged. 1287 * Don't respond if the source or destination is a 1288 * global or subnet broad- or multicast address. 1289 * Note that it is quite possible to receive unicast 1290 * link-layer packets with a broadcast IP address. Use 1291 * in_broadcast() to find them. 1292 */ 1293 if (m->m_flags & (M_BCAST|M_MCAST)) { 1294 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1295 log(LOG_DEBUG, "%s; %s: Listen socket: " 1296 "Connection attempt from broad- or multicast " 1297 "link layer address ignored\n", s, __func__); 1298 goto dropunlock; 1299 } 1300 #ifdef INET6 1301 if (isipv6) { 1302 if (th->th_dport == th->th_sport && 1303 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1304 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1305 log(LOG_DEBUG, "%s; %s: Listen socket: " 1306 "Connection attempt to/from self " 1307 "ignored\n", s, __func__); 1308 goto dropunlock; 1309 } 1310 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1311 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1312 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1313 log(LOG_DEBUG, "%s; %s: Listen socket: " 1314 "Connection attempt from/to multicast " 1315 "address ignored\n", s, __func__); 1316 goto dropunlock; 1317 } 1318 } 1319 #endif 1320 #if defined(INET) && defined(INET6) 1321 else 1322 #endif 1323 #ifdef INET 1324 { 1325 if (th->th_dport == th->th_sport && 1326 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1327 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1328 log(LOG_DEBUG, "%s; %s: Listen socket: " 1329 "Connection attempt from/to self " 1330 "ignored\n", s, __func__); 1331 goto dropunlock; 1332 } 1333 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1334 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1335 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1336 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1337 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1338 log(LOG_DEBUG, "%s; %s: Listen socket: " 1339 "Connection attempt from/to broad- " 1340 "or multicast address ignored\n", 1341 s, __func__); 1342 goto dropunlock; 1343 } 1344 } 1345 #endif 1346 /* 1347 * SYN appears to be valid. Create compressed TCP state 1348 * for syncache. 1349 */ 1350 #ifdef TCPDEBUG 1351 if (so->so_options & SO_DEBUG) 1352 tcp_trace(TA_INPUT, ostate, tp, 1353 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1354 #endif 1355 tcp_dooptions(&to, optp, optlen, TO_SYN); 1356 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1357 /* 1358 * Entry added to syncache and mbuf consumed. 1359 * Everything already unlocked by syncache_add(). 1360 */ 1361 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1362 return; 1363 } 1364 1365 #ifdef TCP_SIGNATURE 1366 if (sig_checked == 0) { 1367 tcp_dooptions(&to, optp, optlen, 1368 (thflags & TH_SYN) ? TO_SYN : 0); 1369 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1370 th, tp->t_flags)) { 1371 1372 /* 1373 * In SYN_SENT state if it receives an RST, it is 1374 * allowed for further processing. 1375 */ 1376 if ((thflags & TH_RST) == 0 || 1377 (tp->t_state == TCPS_SYN_SENT) == 0) 1378 goto dropunlock; 1379 } 1380 sig_checked = 1; 1381 } 1382 #endif 1383 1384 /* 1385 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1386 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1387 * the inpcb, and unlocks pcbinfo. 1388 */ 1389 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1390 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1391 return; 1392 1393 dropwithreset: 1394 if (ti_locked == TI_WLOCKED) { 1395 INP_INFO_WUNLOCK(&V_tcbinfo); 1396 ti_locked = TI_UNLOCKED; 1397 } 1398 #ifdef INVARIANTS 1399 else { 1400 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1401 "ti_locked: %d", __func__, ti_locked)); 1402 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1403 } 1404 #endif 1405 1406 if (inp != NULL) { 1407 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1408 INP_WUNLOCK(inp); 1409 } else 1410 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1411 m = NULL; /* mbuf chain got consumed. */ 1412 goto drop; 1413 1414 dropunlock: 1415 if (ti_locked == TI_WLOCKED) { 1416 INP_INFO_WUNLOCK(&V_tcbinfo); 1417 ti_locked = TI_UNLOCKED; 1418 } 1419 #ifdef INVARIANTS 1420 else { 1421 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1422 "ti_locked: %d", __func__, ti_locked)); 1423 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1424 } 1425 #endif 1426 1427 if (inp != NULL) 1428 INP_WUNLOCK(inp); 1429 1430 drop: 1431 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1432 if (s != NULL) 1433 free(s, M_TCPLOG); 1434 if (m != NULL) 1435 m_freem(m); 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 struct tcpopt to; 1447 1448 #ifdef TCPDEBUG 1449 /* 1450 * The size of tcp_saveipgen must be the size of the max ip header, 1451 * now IPv6. 1452 */ 1453 u_char tcp_saveipgen[IP6_HDR_LEN]; 1454 struct tcphdr tcp_savetcp; 1455 short ostate = 0; 1456 #endif 1457 thflags = th->th_flags; 1458 tp->sackhint.last_sack_ack = 0; 1459 1460 /* 1461 * If this is either a state-changing packet or current state isn't 1462 * established, we require a write lock on tcbinfo. Otherwise, we 1463 * allow the tcbinfo to be in either alocked or unlocked, as the 1464 * caller may have unnecessarily acquired a write lock due to a race. 1465 */ 1466 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1467 tp->t_state != TCPS_ESTABLISHED) { 1468 KASSERT(ti_locked == TI_WLOCKED, ("%s ti_locked %d for " 1469 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1470 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1471 } else { 1472 #ifdef INVARIANTS 1473 if (ti_locked == TI_WLOCKED) 1474 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1475 else { 1476 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1477 "ti_locked: %d", __func__, ti_locked)); 1478 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1479 } 1480 #endif 1481 } 1482 INP_WLOCK_ASSERT(tp->t_inpcb); 1483 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1484 __func__)); 1485 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1486 __func__)); 1487 1488 /* 1489 * Segment received on connection. 1490 * Reset idle time and keep-alive timer. 1491 * XXX: This should be done after segment 1492 * validation to ignore broken/spoofed segs. 1493 */ 1494 tp->t_rcvtime = ticks; 1495 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1496 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 1497 1498 /* 1499 * Unscale the window into a 32-bit value. 1500 * For the SYN_SENT state the scale is zero. 1501 */ 1502 tiwin = th->th_win << tp->snd_scale; 1503 1504 /* 1505 * TCP ECN processing. 1506 */ 1507 if (tp->t_flags & TF_ECN_PERMIT) { 1508 if (thflags & TH_CWR) 1509 tp->t_flags &= ~TF_ECN_SND_ECE; 1510 switch (iptos & IPTOS_ECN_MASK) { 1511 case IPTOS_ECN_CE: 1512 tp->t_flags |= TF_ECN_SND_ECE; 1513 TCPSTAT_INC(tcps_ecn_ce); 1514 break; 1515 case IPTOS_ECN_ECT0: 1516 TCPSTAT_INC(tcps_ecn_ect0); 1517 break; 1518 case IPTOS_ECN_ECT1: 1519 TCPSTAT_INC(tcps_ecn_ect1); 1520 break; 1521 } 1522 /* Congestion experienced. */ 1523 if (thflags & TH_ECE) { 1524 cc_cong_signal(tp, th, CC_ECN); 1525 } 1526 } 1527 1528 /* 1529 * Parse options on any incoming segment. 1530 */ 1531 tcp_dooptions(&to, (u_char *)(th + 1), 1532 (th->th_off << 2) - sizeof(struct tcphdr), 1533 (thflags & TH_SYN) ? TO_SYN : 0); 1534 1535 /* 1536 * If echoed timestamp is later than the current time, 1537 * fall back to non RFC1323 RTT calculation. Normalize 1538 * timestamp if syncookies were used when this connection 1539 * was established. 1540 */ 1541 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1542 to.to_tsecr -= tp->ts_offset; 1543 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1544 to.to_tsecr = 0; 1545 } 1546 1547 /* 1548 * Process options only when we get SYN/ACK back. The SYN case 1549 * for incoming connections is handled in tcp_syncache. 1550 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1551 * or <SYN,ACK>) segment itself is never scaled. 1552 * XXX this is traditional behavior, may need to be cleaned up. 1553 */ 1554 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1555 if ((to.to_flags & TOF_SCALE) && 1556 (tp->t_flags & TF_REQ_SCALE)) { 1557 tp->t_flags |= TF_RCVD_SCALE; 1558 tp->snd_scale = to.to_wscale; 1559 } 1560 /* 1561 * Initial send window. It will be updated with 1562 * the next incoming segment to the scaled value. 1563 */ 1564 tp->snd_wnd = th->th_win; 1565 if (to.to_flags & TOF_TS) { 1566 tp->t_flags |= TF_RCVD_TSTMP; 1567 tp->ts_recent = to.to_tsval; 1568 tp->ts_recent_age = tcp_ts_getticks(); 1569 } 1570 if (to.to_flags & TOF_MSS) 1571 tcp_mss(tp, to.to_mss); 1572 if ((tp->t_flags & TF_SACK_PERMIT) && 1573 (to.to_flags & TOF_SACKPERM) == 0) 1574 tp->t_flags &= ~TF_SACK_PERMIT; 1575 } 1576 1577 /* 1578 * Header prediction: check for the two common cases 1579 * of a uni-directional data xfer. If the packet has 1580 * no control flags, is in-sequence, the window didn't 1581 * change and we're not retransmitting, it's a 1582 * candidate. If the length is zero and the ack moved 1583 * forward, we're the sender side of the xfer. Just 1584 * free the data acked & wake any higher level process 1585 * that was blocked waiting for space. If the length 1586 * is non-zero and the ack didn't move, we're the 1587 * receiver side. If we're getting packets in-order 1588 * (the reassembly queue is empty), add the data to 1589 * the socket buffer and note that we need a delayed ack. 1590 * Make sure that the hidden state-flags are also off. 1591 * Since we check for TCPS_ESTABLISHED first, it can only 1592 * be TH_NEEDSYN. 1593 */ 1594 if (tp->t_state == TCPS_ESTABLISHED && 1595 th->th_seq == tp->rcv_nxt && 1596 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1597 tp->snd_nxt == tp->snd_max && 1598 tiwin && tiwin == tp->snd_wnd && 1599 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1600 LIST_EMPTY(&tp->t_segq) && 1601 ((to.to_flags & TOF_TS) == 0 || 1602 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1603 1604 /* 1605 * If last ACK falls within this segment's sequence numbers, 1606 * record the timestamp. 1607 * NOTE that the test is modified according to the latest 1608 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1609 */ 1610 if ((to.to_flags & TOF_TS) != 0 && 1611 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1612 tp->ts_recent_age = tcp_ts_getticks(); 1613 tp->ts_recent = to.to_tsval; 1614 } 1615 1616 if (tlen == 0) { 1617 if (SEQ_GT(th->th_ack, tp->snd_una) && 1618 SEQ_LEQ(th->th_ack, tp->snd_max) && 1619 !IN_RECOVERY(tp->t_flags) && 1620 (to.to_flags & TOF_SACK) == 0 && 1621 TAILQ_EMPTY(&tp->snd_holes)) { 1622 /* 1623 * This is a pure ack for outstanding data. 1624 */ 1625 if (ti_locked == TI_WLOCKED) 1626 INP_INFO_WUNLOCK(&V_tcbinfo); 1627 ti_locked = TI_UNLOCKED; 1628 1629 TCPSTAT_INC(tcps_predack); 1630 1631 /* 1632 * "bad retransmit" recovery. 1633 */ 1634 if (tp->t_rxtshift == 1 && 1635 tp->t_flags & TF_PREVVALID && 1636 (int)(ticks - tp->t_badrxtwin) < 0) { 1637 cc_cong_signal(tp, th, CC_RTO_ERR); 1638 } 1639 1640 /* 1641 * Recalculate the transmit timer / rtt. 1642 * 1643 * Some boxes send broken timestamp replies 1644 * during the SYN+ACK phase, ignore 1645 * timestamps of 0 or we could calculate a 1646 * huge RTT and blow up the retransmit timer. 1647 */ 1648 if ((to.to_flags & TOF_TS) != 0 && 1649 to.to_tsecr) { 1650 u_int t; 1651 1652 t = tcp_ts_getticks() - to.to_tsecr; 1653 if (!tp->t_rttlow || tp->t_rttlow > t) 1654 tp->t_rttlow = t; 1655 tcp_xmit_timer(tp, 1656 TCP_TS_TO_TICKS(t) + 1); 1657 } else if (tp->t_rtttime && 1658 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1659 if (!tp->t_rttlow || 1660 tp->t_rttlow > ticks - tp->t_rtttime) 1661 tp->t_rttlow = ticks - tp->t_rtttime; 1662 tcp_xmit_timer(tp, 1663 ticks - tp->t_rtttime); 1664 } 1665 acked = BYTES_THIS_ACK(tp, th); 1666 1667 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1668 hhook_run_tcp_est_in(tp, th, &to); 1669 1670 TCPSTAT_INC(tcps_rcvackpack); 1671 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1672 sbdrop(&so->so_snd, acked); 1673 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1674 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1675 tp->snd_recover = th->th_ack - 1; 1676 1677 /* 1678 * Let the congestion control algorithm update 1679 * congestion control related information. This 1680 * typically means increasing the congestion 1681 * window. 1682 */ 1683 cc_ack_received(tp, th, CC_ACK); 1684 1685 tp->snd_una = th->th_ack; 1686 /* 1687 * Pull snd_wl2 up to prevent seq wrap relative 1688 * to th_ack. 1689 */ 1690 tp->snd_wl2 = th->th_ack; 1691 tp->t_dupacks = 0; 1692 m_freem(m); 1693 ND6_HINT(tp); /* Some progress has been made. */ 1694 1695 /* 1696 * If all outstanding data are acked, stop 1697 * retransmit timer, otherwise restart timer 1698 * using current (possibly backed-off) value. 1699 * If process is waiting for space, 1700 * wakeup/selwakeup/signal. If data 1701 * are ready to send, let tcp_output 1702 * decide between more output or persist. 1703 */ 1704 #ifdef TCPDEBUG 1705 if (so->so_options & SO_DEBUG) 1706 tcp_trace(TA_INPUT, ostate, tp, 1707 (void *)tcp_saveipgen, 1708 &tcp_savetcp, 0); 1709 #endif 1710 if (tp->snd_una == tp->snd_max) 1711 tcp_timer_activate(tp, TT_REXMT, 0); 1712 else if (!tcp_timer_active(tp, TT_PERSIST)) 1713 tcp_timer_activate(tp, TT_REXMT, 1714 tp->t_rxtcur); 1715 sowwakeup(so); 1716 if (so->so_snd.sb_cc) 1717 (void) tcp_output(tp); 1718 goto check_delack; 1719 } 1720 } else if (th->th_ack == tp->snd_una && 1721 tlen <= sbspace(&so->so_rcv)) { 1722 int newsize = 0; /* automatic sockbuf scaling */ 1723 1724 /* 1725 * This is a pure, in-sequence data packet with 1726 * nothing on the reassembly queue and we have enough 1727 * buffer space to take it. 1728 */ 1729 if (ti_locked == TI_WLOCKED) 1730 INP_INFO_WUNLOCK(&V_tcbinfo); 1731 ti_locked = TI_UNLOCKED; 1732 1733 /* Clean receiver SACK report if present */ 1734 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1735 tcp_clean_sackreport(tp); 1736 TCPSTAT_INC(tcps_preddat); 1737 tp->rcv_nxt += tlen; 1738 /* 1739 * Pull snd_wl1 up to prevent seq wrap relative to 1740 * th_seq. 1741 */ 1742 tp->snd_wl1 = th->th_seq; 1743 /* 1744 * Pull rcv_up up to prevent seq wrap relative to 1745 * rcv_nxt. 1746 */ 1747 tp->rcv_up = tp->rcv_nxt; 1748 TCPSTAT_INC(tcps_rcvpack); 1749 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1750 ND6_HINT(tp); /* Some progress has been made */ 1751 #ifdef TCPDEBUG 1752 if (so->so_options & SO_DEBUG) 1753 tcp_trace(TA_INPUT, ostate, tp, 1754 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1755 #endif 1756 /* 1757 * Automatic sizing of receive socket buffer. Often the send 1758 * buffer size is not optimally adjusted to the actual network 1759 * conditions at hand (delay bandwidth product). Setting the 1760 * buffer size too small limits throughput on links with high 1761 * bandwidth and high delay (eg. trans-continental/oceanic links). 1762 * 1763 * On the receive side the socket buffer memory is only rarely 1764 * used to any significant extent. This allows us to be much 1765 * more aggressive in scaling the receive socket buffer. For 1766 * the case that the buffer space is actually used to a large 1767 * extent and we run out of kernel memory we can simply drop 1768 * the new segments; TCP on the sender will just retransmit it 1769 * later. Setting the buffer size too big may only consume too 1770 * much kernel memory if the application doesn't read() from 1771 * the socket or packet loss or reordering makes use of the 1772 * reassembly queue. 1773 * 1774 * The criteria to step up the receive buffer one notch are: 1775 * 1. the number of bytes received during the time it takes 1776 * one timestamp to be reflected back to us (the RTT); 1777 * 2. received bytes per RTT is within seven eighth of the 1778 * current socket buffer size; 1779 * 3. receive buffer size has not hit maximal automatic size; 1780 * 1781 * This algorithm does one step per RTT at most and only if 1782 * we receive a bulk stream w/o packet losses or reorderings. 1783 * Shrinking the buffer during idle times is not necessary as 1784 * it doesn't consume any memory when idle. 1785 * 1786 * TODO: Only step up if the application is actually serving 1787 * the buffer to better manage the socket buffer resources. 1788 */ 1789 if (V_tcp_do_autorcvbuf && 1790 to.to_tsecr && 1791 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1792 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1793 to.to_tsecr - tp->rfbuf_ts < hz) { 1794 if (tp->rfbuf_cnt > 1795 (so->so_rcv.sb_hiwat / 8 * 7) && 1796 so->so_rcv.sb_hiwat < 1797 V_tcp_autorcvbuf_max) { 1798 newsize = 1799 min(so->so_rcv.sb_hiwat + 1800 V_tcp_autorcvbuf_inc, 1801 V_tcp_autorcvbuf_max); 1802 } 1803 /* Start over with next RTT. */ 1804 tp->rfbuf_ts = 0; 1805 tp->rfbuf_cnt = 0; 1806 } else 1807 tp->rfbuf_cnt += tlen; /* add up */ 1808 } 1809 1810 /* Add data to socket buffer. */ 1811 SOCKBUF_LOCK(&so->so_rcv); 1812 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1813 m_freem(m); 1814 } else { 1815 /* 1816 * Set new socket buffer size. 1817 * Give up when limit is reached. 1818 */ 1819 if (newsize) 1820 if (!sbreserve_locked(&so->so_rcv, 1821 newsize, so, NULL)) 1822 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1823 m_adj(m, drop_hdrlen); /* delayed header drop */ 1824 sbappendstream_locked(&so->so_rcv, m); 1825 } 1826 /* NB: sorwakeup_locked() does an implicit unlock. */ 1827 sorwakeup_locked(so); 1828 if (DELAY_ACK(tp)) { 1829 tp->t_flags |= TF_DELACK; 1830 } else { 1831 tp->t_flags |= TF_ACKNOW; 1832 tcp_output(tp); 1833 } 1834 goto check_delack; 1835 } 1836 } 1837 1838 /* 1839 * Calculate amount of space in receive window, 1840 * and then do TCP input processing. 1841 * Receive window is amount of space in rcv queue, 1842 * but not less than advertised window. 1843 */ 1844 win = sbspace(&so->so_rcv); 1845 if (win < 0) 1846 win = 0; 1847 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1848 1849 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1850 tp->rfbuf_ts = 0; 1851 tp->rfbuf_cnt = 0; 1852 1853 switch (tp->t_state) { 1854 1855 /* 1856 * If the state is SYN_RECEIVED: 1857 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1858 */ 1859 case TCPS_SYN_RECEIVED: 1860 if ((thflags & TH_ACK) && 1861 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1862 SEQ_GT(th->th_ack, tp->snd_max))) { 1863 rstreason = BANDLIM_RST_OPENPORT; 1864 goto dropwithreset; 1865 } 1866 break; 1867 1868 /* 1869 * If the state is SYN_SENT: 1870 * if seg contains an ACK, but not for our SYN, drop the input. 1871 * if seg contains a RST, then drop the connection. 1872 * if seg does not contain SYN, then drop it. 1873 * Otherwise this is an acceptable SYN segment 1874 * initialize tp->rcv_nxt and tp->irs 1875 * if seg contains ack then advance tp->snd_una 1876 * if seg contains an ECE and ECN support is enabled, the stream 1877 * is ECN capable. 1878 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1879 * arrange for segment to be acked (eventually) 1880 * continue processing rest of data/controls, beginning with URG 1881 */ 1882 case TCPS_SYN_SENT: 1883 if ((thflags & TH_ACK) && 1884 (SEQ_LEQ(th->th_ack, tp->iss) || 1885 SEQ_GT(th->th_ack, tp->snd_max))) { 1886 rstreason = BANDLIM_UNLIMITED; 1887 goto dropwithreset; 1888 } 1889 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) 1890 tp = tcp_drop(tp, ECONNREFUSED); 1891 if (thflags & TH_RST) 1892 goto drop; 1893 if (!(thflags & TH_SYN)) 1894 goto drop; 1895 1896 tp->irs = th->th_seq; 1897 tcp_rcvseqinit(tp); 1898 if (thflags & TH_ACK) { 1899 TCPSTAT_INC(tcps_connects); 1900 soisconnected(so); 1901 #ifdef MAC 1902 mac_socketpeer_set_from_mbuf(m, so); 1903 #endif 1904 /* Do window scaling on this connection? */ 1905 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1906 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1907 tp->rcv_scale = tp->request_r_scale; 1908 } 1909 tp->rcv_adv += imin(tp->rcv_wnd, 1910 TCP_MAXWIN << tp->rcv_scale); 1911 tp->snd_una++; /* SYN is acked */ 1912 /* 1913 * If there's data, delay ACK; if there's also a FIN 1914 * ACKNOW will be turned on later. 1915 */ 1916 if (DELAY_ACK(tp) && tlen != 0) 1917 tcp_timer_activate(tp, TT_DELACK, 1918 tcp_delacktime); 1919 else 1920 tp->t_flags |= TF_ACKNOW; 1921 1922 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 1923 tp->t_flags |= TF_ECN_PERMIT; 1924 TCPSTAT_INC(tcps_ecn_shs); 1925 } 1926 1927 /* 1928 * Received <SYN,ACK> in SYN_SENT[*] state. 1929 * Transitions: 1930 * SYN_SENT --> ESTABLISHED 1931 * SYN_SENT* --> FIN_WAIT_1 1932 */ 1933 tp->t_starttime = ticks; 1934 if (tp->t_flags & TF_NEEDFIN) { 1935 tp->t_state = TCPS_FIN_WAIT_1; 1936 tp->t_flags &= ~TF_NEEDFIN; 1937 thflags &= ~TH_SYN; 1938 } else { 1939 tp->t_state = TCPS_ESTABLISHED; 1940 cc_conn_init(tp); 1941 tcp_timer_activate(tp, TT_KEEP, 1942 TP_KEEPIDLE(tp)); 1943 } 1944 } else { 1945 /* 1946 * Received initial SYN in SYN-SENT[*] state => 1947 * simultaneous open. If segment contains CC option 1948 * and there is a cached CC, apply TAO test. 1949 * If it succeeds, connection is * half-synchronized. 1950 * Otherwise, do 3-way handshake: 1951 * SYN-SENT -> SYN-RECEIVED 1952 * SYN-SENT* -> SYN-RECEIVED* 1953 * If there was no CC option, clear cached CC value. 1954 */ 1955 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 1956 tcp_timer_activate(tp, TT_REXMT, 0); 1957 tp->t_state = TCPS_SYN_RECEIVED; 1958 } 1959 1960 KASSERT(ti_locked == TI_WLOCKED, ("%s: trimthenstep6: " 1961 "ti_locked %d", __func__, ti_locked)); 1962 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 1963 INP_WLOCK_ASSERT(tp->t_inpcb); 1964 1965 /* 1966 * Advance th->th_seq to correspond to first data byte. 1967 * If data, trim to stay within window, 1968 * dropping FIN if necessary. 1969 */ 1970 th->th_seq++; 1971 if (tlen > tp->rcv_wnd) { 1972 todrop = tlen - tp->rcv_wnd; 1973 m_adj(m, -todrop); 1974 tlen = tp->rcv_wnd; 1975 thflags &= ~TH_FIN; 1976 TCPSTAT_INC(tcps_rcvpackafterwin); 1977 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 1978 } 1979 tp->snd_wl1 = th->th_seq - 1; 1980 tp->rcv_up = th->th_seq; 1981 /* 1982 * Client side of transaction: already sent SYN and data. 1983 * If the remote host used T/TCP to validate the SYN, 1984 * our data will be ACK'd; if so, enter normal data segment 1985 * processing in the middle of step 5, ack processing. 1986 * Otherwise, goto step 6. 1987 */ 1988 if (thflags & TH_ACK) 1989 goto process_ACK; 1990 1991 goto step6; 1992 1993 /* 1994 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 1995 * do normal processing. 1996 * 1997 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 1998 */ 1999 case TCPS_LAST_ACK: 2000 case TCPS_CLOSING: 2001 break; /* continue normal processing */ 2002 } 2003 2004 /* 2005 * States other than LISTEN or SYN_SENT. 2006 * First check the RST flag and sequence number since reset segments 2007 * are exempt from the timestamp and connection count tests. This 2008 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2009 * below which allowed reset segments in half the sequence space 2010 * to fall though and be processed (which gives forged reset 2011 * segments with a random sequence number a 50 percent chance of 2012 * killing a connection). 2013 * Then check timestamp, if present. 2014 * Then check the connection count, if present. 2015 * Then check that at least some bytes of segment are within 2016 * receive window. If segment begins before rcv_nxt, 2017 * drop leading data (and SYN); if nothing left, just ack. 2018 * 2019 * 2020 * If the RST bit is set, check the sequence number to see 2021 * if this is a valid reset segment. 2022 * RFC 793 page 37: 2023 * In all states except SYN-SENT, all reset (RST) segments 2024 * are validated by checking their SEQ-fields. A reset is 2025 * valid if its sequence number is in the window. 2026 * Note: this does not take into account delayed ACKs, so 2027 * we should test against last_ack_sent instead of rcv_nxt. 2028 * The sequence number in the reset segment is normally an 2029 * echo of our outgoing acknowlegement numbers, but some hosts 2030 * send a reset with the sequence number at the rightmost edge 2031 * of our receive window, and we have to handle this case. 2032 * Note 2: Paul Watson's paper "Slipping in the Window" has shown 2033 * that brute force RST attacks are possible. To combat this, 2034 * we use a much stricter check while in the ESTABLISHED state, 2035 * only accepting RSTs where the sequence number is equal to 2036 * last_ack_sent. In all other states (the states in which a 2037 * RST is more likely), the more permissive check is used. 2038 * If we have multiple segments in flight, the initial reset 2039 * segment sequence numbers will be to the left of last_ack_sent, 2040 * but they will eventually catch up. 2041 * In any case, it never made sense to trim reset segments to 2042 * fit the receive window since RFC 1122 says: 2043 * 4.2.2.12 RST Segment: RFC-793 Section 3.4 2044 * 2045 * A TCP SHOULD allow a received RST segment to include data. 2046 * 2047 * DISCUSSION 2048 * It has been suggested that a RST segment could contain 2049 * ASCII text that encoded and explained the cause of the 2050 * RST. No standard has yet been established for such 2051 * data. 2052 * 2053 * If the reset segment passes the sequence number test examine 2054 * the state: 2055 * SYN_RECEIVED STATE: 2056 * If passive open, return to LISTEN state. 2057 * If active open, inform user that connection was refused. 2058 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT_2, CLOSE_WAIT STATES: 2059 * Inform user that connection was reset, and close tcb. 2060 * CLOSING, LAST_ACK STATES: 2061 * Close the tcb. 2062 * TIME_WAIT STATE: 2063 * Drop the segment - see Stevens, vol. 2, p. 964 and 2064 * RFC 1337. 2065 */ 2066 if (thflags & TH_RST) { 2067 if (SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 2068 SEQ_LEQ(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2069 switch (tp->t_state) { 2070 2071 case TCPS_SYN_RECEIVED: 2072 so->so_error = ECONNREFUSED; 2073 goto close; 2074 2075 case TCPS_ESTABLISHED: 2076 if (V_tcp_insecure_rst == 0 && 2077 !(SEQ_GEQ(th->th_seq, tp->rcv_nxt - 1) && 2078 SEQ_LEQ(th->th_seq, tp->rcv_nxt + 1)) && 2079 !(SEQ_GEQ(th->th_seq, tp->last_ack_sent - 1) && 2080 SEQ_LEQ(th->th_seq, tp->last_ack_sent + 1))) { 2081 TCPSTAT_INC(tcps_badrst); 2082 goto drop; 2083 } 2084 /* FALLTHROUGH */ 2085 case TCPS_FIN_WAIT_1: 2086 case TCPS_FIN_WAIT_2: 2087 case TCPS_CLOSE_WAIT: 2088 so->so_error = ECONNRESET; 2089 close: 2090 KASSERT(ti_locked == TI_WLOCKED, 2091 ("tcp_do_segment: TH_RST 1 ti_locked %d", 2092 ti_locked)); 2093 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2094 2095 tp->t_state = TCPS_CLOSED; 2096 TCPSTAT_INC(tcps_drops); 2097 tp = tcp_close(tp); 2098 break; 2099 2100 case TCPS_CLOSING: 2101 case TCPS_LAST_ACK: 2102 KASSERT(ti_locked == TI_WLOCKED, 2103 ("tcp_do_segment: TH_RST 2 ti_locked %d", 2104 ti_locked)); 2105 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2106 2107 tp = tcp_close(tp); 2108 break; 2109 } 2110 } 2111 goto drop; 2112 } 2113 2114 /* 2115 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2116 * and it's less than ts_recent, drop it. 2117 */ 2118 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2119 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2120 2121 /* Check to see if ts_recent is over 24 days old. */ 2122 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2123 /* 2124 * Invalidate ts_recent. If this segment updates 2125 * ts_recent, the age will be reset later and ts_recent 2126 * will get a valid value. If it does not, setting 2127 * ts_recent to zero will at least satisfy the 2128 * requirement that zero be placed in the timestamp 2129 * echo reply when ts_recent isn't valid. The 2130 * age isn't reset until we get a valid ts_recent 2131 * because we don't want out-of-order segments to be 2132 * dropped when ts_recent is old. 2133 */ 2134 tp->ts_recent = 0; 2135 } else { 2136 TCPSTAT_INC(tcps_rcvduppack); 2137 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2138 TCPSTAT_INC(tcps_pawsdrop); 2139 if (tlen) 2140 goto dropafterack; 2141 goto drop; 2142 } 2143 } 2144 2145 /* 2146 * In the SYN-RECEIVED state, validate that the packet belongs to 2147 * this connection before trimming the data to fit the receive 2148 * window. Check the sequence number versus IRS since we know 2149 * the sequence numbers haven't wrapped. This is a partial fix 2150 * for the "LAND" DoS attack. 2151 */ 2152 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2153 rstreason = BANDLIM_RST_OPENPORT; 2154 goto dropwithreset; 2155 } 2156 2157 todrop = tp->rcv_nxt - th->th_seq; 2158 if (todrop > 0) { 2159 /* 2160 * If this is a duplicate SYN for our current connection, 2161 * advance over it and pretend and it's not a SYN. 2162 */ 2163 if (thflags & TH_SYN && th->th_seq == tp->irs) { 2164 thflags &= ~TH_SYN; 2165 th->th_seq++; 2166 if (th->th_urp > 1) 2167 th->th_urp--; 2168 else 2169 thflags &= ~TH_URG; 2170 todrop--; 2171 } 2172 /* 2173 * Following if statement from Stevens, vol. 2, p. 960. 2174 */ 2175 if (todrop > tlen 2176 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2177 /* 2178 * Any valid FIN must be to the left of the window. 2179 * At this point the FIN must be a duplicate or out 2180 * of sequence; drop it. 2181 */ 2182 thflags &= ~TH_FIN; 2183 2184 /* 2185 * Send an ACK to resynchronize and drop any data. 2186 * But keep on processing for RST or ACK. 2187 */ 2188 tp->t_flags |= TF_ACKNOW; 2189 todrop = tlen; 2190 TCPSTAT_INC(tcps_rcvduppack); 2191 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2192 } else { 2193 TCPSTAT_INC(tcps_rcvpartduppack); 2194 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2195 } 2196 drop_hdrlen += todrop; /* drop from the top afterwards */ 2197 th->th_seq += todrop; 2198 tlen -= todrop; 2199 if (th->th_urp > todrop) 2200 th->th_urp -= todrop; 2201 else { 2202 thflags &= ~TH_URG; 2203 th->th_urp = 0; 2204 } 2205 } 2206 2207 /* 2208 * If new data are received on a connection after the 2209 * user processes are gone, then RST the other end. 2210 */ 2211 if ((so->so_state & SS_NOFDREF) && 2212 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2213 char *s; 2214 2215 KASSERT(ti_locked == TI_WLOCKED, ("%s: SS_NOFDEREF && " 2216 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2217 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2218 2219 if ((s = tcp_log_addrs(&tp->t_inpcb->inp_inc, th, NULL, NULL))) { 2220 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data after socket " 2221 "was closed, sending RST and removing tcpcb\n", 2222 s, __func__, tcpstates[tp->t_state], tlen); 2223 free(s, M_TCPLOG); 2224 } 2225 tp = tcp_close(tp); 2226 TCPSTAT_INC(tcps_rcvafterclose); 2227 rstreason = BANDLIM_UNLIMITED; 2228 goto dropwithreset; 2229 } 2230 2231 /* 2232 * If segment ends after window, drop trailing data 2233 * (and PUSH and FIN); if nothing left, just ACK. 2234 */ 2235 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2236 if (todrop > 0) { 2237 TCPSTAT_INC(tcps_rcvpackafterwin); 2238 if (todrop >= tlen) { 2239 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2240 /* 2241 * If window is closed can only take segments at 2242 * window edge, and have to drop data and PUSH from 2243 * incoming segments. Continue processing, but 2244 * remember to ack. Otherwise, drop segment 2245 * and ack. 2246 */ 2247 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2248 tp->t_flags |= TF_ACKNOW; 2249 TCPSTAT_INC(tcps_rcvwinprobe); 2250 } else 2251 goto dropafterack; 2252 } else 2253 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2254 m_adj(m, -todrop); 2255 tlen -= todrop; 2256 thflags &= ~(TH_PUSH|TH_FIN); 2257 } 2258 2259 /* 2260 * If last ACK falls within this segment's sequence numbers, 2261 * record its timestamp. 2262 * NOTE: 2263 * 1) That the test incorporates suggestions from the latest 2264 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2265 * 2) That updating only on newer timestamps interferes with 2266 * our earlier PAWS tests, so this check should be solely 2267 * predicated on the sequence space of this segment. 2268 * 3) That we modify the segment boundary check to be 2269 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2270 * instead of RFC1323's 2271 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2272 * This modified check allows us to overcome RFC1323's 2273 * limitations as described in Stevens TCP/IP Illustrated 2274 * Vol. 2 p.869. In such cases, we can still calculate the 2275 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2276 */ 2277 if ((to.to_flags & TOF_TS) != 0 && 2278 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2279 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2280 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2281 tp->ts_recent_age = tcp_ts_getticks(); 2282 tp->ts_recent = to.to_tsval; 2283 } 2284 2285 /* 2286 * If a SYN is in the window, then this is an 2287 * error and we send an RST and drop the connection. 2288 */ 2289 if (thflags & TH_SYN) { 2290 KASSERT(ti_locked == TI_WLOCKED, 2291 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2292 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2293 2294 tp = tcp_drop(tp, ECONNRESET); 2295 rstreason = BANDLIM_UNLIMITED; 2296 goto drop; 2297 } 2298 2299 /* 2300 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2301 * flag is on (half-synchronized state), then queue data for 2302 * later processing; else drop segment and return. 2303 */ 2304 if ((thflags & TH_ACK) == 0) { 2305 if (tp->t_state == TCPS_SYN_RECEIVED || 2306 (tp->t_flags & TF_NEEDSYN)) 2307 goto step6; 2308 else if (tp->t_flags & TF_ACKNOW) 2309 goto dropafterack; 2310 else 2311 goto drop; 2312 } 2313 2314 /* 2315 * Ack processing. 2316 */ 2317 switch (tp->t_state) { 2318 2319 /* 2320 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2321 * ESTABLISHED state and continue processing. 2322 * The ACK was checked above. 2323 */ 2324 case TCPS_SYN_RECEIVED: 2325 2326 TCPSTAT_INC(tcps_connects); 2327 soisconnected(so); 2328 /* Do window scaling? */ 2329 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2330 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2331 tp->rcv_scale = tp->request_r_scale; 2332 tp->snd_wnd = tiwin; 2333 } 2334 /* 2335 * Make transitions: 2336 * SYN-RECEIVED -> ESTABLISHED 2337 * SYN-RECEIVED* -> FIN-WAIT-1 2338 */ 2339 tp->t_starttime = ticks; 2340 if (tp->t_flags & TF_NEEDFIN) { 2341 tp->t_state = TCPS_FIN_WAIT_1; 2342 tp->t_flags &= ~TF_NEEDFIN; 2343 } else { 2344 tp->t_state = TCPS_ESTABLISHED; 2345 cc_conn_init(tp); 2346 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2347 } 2348 /* 2349 * If segment contains data or ACK, will call tcp_reass() 2350 * later; if not, do so now to pass queued data to user. 2351 */ 2352 if (tlen == 0 && (thflags & TH_FIN) == 0) 2353 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2354 (struct mbuf *)0); 2355 tp->snd_wl1 = th->th_seq - 1; 2356 /* FALLTHROUGH */ 2357 2358 /* 2359 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2360 * ACKs. If the ack is in the range 2361 * tp->snd_una < th->th_ack <= tp->snd_max 2362 * then advance tp->snd_una to th->th_ack and drop 2363 * data from the retransmission queue. If this ACK reflects 2364 * more up to date window information we update our window information. 2365 */ 2366 case TCPS_ESTABLISHED: 2367 case TCPS_FIN_WAIT_1: 2368 case TCPS_FIN_WAIT_2: 2369 case TCPS_CLOSE_WAIT: 2370 case TCPS_CLOSING: 2371 case TCPS_LAST_ACK: 2372 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2373 TCPSTAT_INC(tcps_rcvacktoomuch); 2374 goto dropafterack; 2375 } 2376 if ((tp->t_flags & TF_SACK_PERMIT) && 2377 ((to.to_flags & TOF_SACK) || 2378 !TAILQ_EMPTY(&tp->snd_holes))) 2379 tcp_sack_doack(tp, &to, th->th_ack); 2380 2381 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2382 hhook_run_tcp_est_in(tp, th, &to); 2383 2384 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2385 if (tlen == 0 && tiwin == tp->snd_wnd) { 2386 TCPSTAT_INC(tcps_rcvdupack); 2387 /* 2388 * If we have outstanding data (other than 2389 * a window probe), this is a completely 2390 * duplicate ack (ie, window info didn't 2391 * change), the ack is the biggest we've 2392 * seen and we've seen exactly our rexmt 2393 * threshhold of them, assume a packet 2394 * has been dropped and retransmit it. 2395 * Kludge snd_nxt & the congestion 2396 * window so we send only this one 2397 * packet. 2398 * 2399 * We know we're losing at the current 2400 * window size so do congestion avoidance 2401 * (set ssthresh to half the current window 2402 * and pull our congestion window back to 2403 * the new ssthresh). 2404 * 2405 * Dup acks mean that packets have left the 2406 * network (they're now cached at the receiver) 2407 * so bump cwnd by the amount in the receiver 2408 * to keep a constant cwnd packets in the 2409 * network. 2410 * 2411 * When using TCP ECN, notify the peer that 2412 * we reduced the cwnd. 2413 */ 2414 if (!tcp_timer_active(tp, TT_REXMT) || 2415 th->th_ack != tp->snd_una) 2416 tp->t_dupacks = 0; 2417 else if (++tp->t_dupacks > tcprexmtthresh || 2418 IN_FASTRECOVERY(tp->t_flags)) { 2419 cc_ack_received(tp, th, CC_DUPACK); 2420 if ((tp->t_flags & TF_SACK_PERMIT) && 2421 IN_FASTRECOVERY(tp->t_flags)) { 2422 int awnd; 2423 2424 /* 2425 * Compute the amount of data in flight first. 2426 * We can inject new data into the pipe iff 2427 * we have less than 1/2 the original window's 2428 * worth of data in flight. 2429 */ 2430 awnd = (tp->snd_nxt - tp->snd_fack) + 2431 tp->sackhint.sack_bytes_rexmit; 2432 if (awnd < tp->snd_ssthresh) { 2433 tp->snd_cwnd += tp->t_maxseg; 2434 if (tp->snd_cwnd > tp->snd_ssthresh) 2435 tp->snd_cwnd = tp->snd_ssthresh; 2436 } 2437 } else 2438 tp->snd_cwnd += tp->t_maxseg; 2439 if ((thflags & TH_FIN) && 2440 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2441 /* 2442 * If its a fin we need to process 2443 * it to avoid a race where both 2444 * sides enter FIN-WAIT and send FIN|ACK 2445 * at the same time. 2446 */ 2447 break; 2448 } 2449 (void) tcp_output(tp); 2450 goto drop; 2451 } else if (tp->t_dupacks == tcprexmtthresh) { 2452 tcp_seq onxt = tp->snd_nxt; 2453 2454 /* 2455 * If we're doing sack, check to 2456 * see if we're already in sack 2457 * recovery. If we're not doing sack, 2458 * check to see if we're in newreno 2459 * recovery. 2460 */ 2461 if (tp->t_flags & TF_SACK_PERMIT) { 2462 if (IN_FASTRECOVERY(tp->t_flags)) { 2463 tp->t_dupacks = 0; 2464 break; 2465 } 2466 } else { 2467 if (SEQ_LEQ(th->th_ack, 2468 tp->snd_recover)) { 2469 tp->t_dupacks = 0; 2470 break; 2471 } 2472 } 2473 /* Congestion signal before ack. */ 2474 cc_cong_signal(tp, th, CC_NDUPACK); 2475 cc_ack_received(tp, th, CC_DUPACK); 2476 tcp_timer_activate(tp, TT_REXMT, 0); 2477 tp->t_rtttime = 0; 2478 if (tp->t_flags & TF_SACK_PERMIT) { 2479 TCPSTAT_INC( 2480 tcps_sack_recovery_episode); 2481 tp->sack_newdata = tp->snd_nxt; 2482 tp->snd_cwnd = tp->t_maxseg; 2483 (void) tcp_output(tp); 2484 goto drop; 2485 } 2486 tp->snd_nxt = th->th_ack; 2487 tp->snd_cwnd = tp->t_maxseg; 2488 if ((thflags & TH_FIN) && 2489 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2490 /* 2491 * If its a fin we need to process 2492 * it to avoid a race where both 2493 * sides enter FIN-WAIT and send FIN|ACK 2494 * at the same time. 2495 */ 2496 break; 2497 } 2498 (void) tcp_output(tp); 2499 KASSERT(tp->snd_limited <= 2, 2500 ("%s: tp->snd_limited too big", 2501 __func__)); 2502 tp->snd_cwnd = tp->snd_ssthresh + 2503 tp->t_maxseg * 2504 (tp->t_dupacks - tp->snd_limited); 2505 if (SEQ_GT(onxt, tp->snd_nxt)) 2506 tp->snd_nxt = onxt; 2507 goto drop; 2508 } else if (V_tcp_do_rfc3042) { 2509 cc_ack_received(tp, th, CC_DUPACK); 2510 u_long oldcwnd = tp->snd_cwnd; 2511 tcp_seq oldsndmax = tp->snd_max; 2512 u_int sent; 2513 2514 KASSERT(tp->t_dupacks == 1 || 2515 tp->t_dupacks == 2, 2516 ("%s: dupacks not 1 or 2", 2517 __func__)); 2518 if (tp->t_dupacks == 1) 2519 tp->snd_limited = 0; 2520 tp->snd_cwnd = 2521 (tp->snd_nxt - tp->snd_una) + 2522 (tp->t_dupacks - tp->snd_limited) * 2523 tp->t_maxseg; 2524 if ((thflags & TH_FIN) && 2525 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2526 /* 2527 * If its a fin we need to process 2528 * it to avoid a race where both 2529 * sides enter FIN-WAIT and send FIN|ACK 2530 * at the same time. 2531 */ 2532 break; 2533 } 2534 (void) tcp_output(tp); 2535 sent = tp->snd_max - oldsndmax; 2536 if (sent > tp->t_maxseg) { 2537 KASSERT((tp->t_dupacks == 2 && 2538 tp->snd_limited == 0) || 2539 (sent == tp->t_maxseg + 1 && 2540 tp->t_flags & TF_SENTFIN), 2541 ("%s: sent too much", 2542 __func__)); 2543 tp->snd_limited = 2; 2544 } else if (sent > 0) 2545 ++tp->snd_limited; 2546 tp->snd_cwnd = oldcwnd; 2547 goto drop; 2548 } 2549 } else 2550 tp->t_dupacks = 0; 2551 break; 2552 } 2553 2554 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2555 ("%s: th_ack <= snd_una", __func__)); 2556 2557 /* 2558 * If the congestion window was inflated to account 2559 * for the other side's cached packets, retract it. 2560 */ 2561 if (IN_FASTRECOVERY(tp->t_flags)) { 2562 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2563 if (tp->t_flags & TF_SACK_PERMIT) 2564 tcp_sack_partialack(tp, th); 2565 else 2566 tcp_newreno_partial_ack(tp, th); 2567 } else 2568 cc_post_recovery(tp, th); 2569 } 2570 tp->t_dupacks = 0; 2571 /* 2572 * If we reach this point, ACK is not a duplicate, 2573 * i.e., it ACKs something we sent. 2574 */ 2575 if (tp->t_flags & TF_NEEDSYN) { 2576 /* 2577 * T/TCP: Connection was half-synchronized, and our 2578 * SYN has been ACK'd (so connection is now fully 2579 * synchronized). Go to non-starred state, 2580 * increment snd_una for ACK of SYN, and check if 2581 * we can do window scaling. 2582 */ 2583 tp->t_flags &= ~TF_NEEDSYN; 2584 tp->snd_una++; 2585 /* Do window scaling? */ 2586 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2587 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2588 tp->rcv_scale = tp->request_r_scale; 2589 /* Send window already scaled. */ 2590 } 2591 } 2592 2593 process_ACK: 2594 INP_WLOCK_ASSERT(tp->t_inpcb); 2595 2596 acked = BYTES_THIS_ACK(tp, th); 2597 TCPSTAT_INC(tcps_rcvackpack); 2598 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2599 2600 /* 2601 * If we just performed our first retransmit, and the ACK 2602 * arrives within our recovery window, then it was a mistake 2603 * to do the retransmit in the first place. Recover our 2604 * original cwnd and ssthresh, and proceed to transmit where 2605 * we left off. 2606 */ 2607 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2608 (int)(ticks - tp->t_badrxtwin) < 0) 2609 cc_cong_signal(tp, th, CC_RTO_ERR); 2610 2611 /* 2612 * If we have a timestamp reply, update smoothed 2613 * round trip time. If no timestamp is present but 2614 * transmit timer is running and timed sequence 2615 * number was acked, update smoothed round trip time. 2616 * Since we now have an rtt measurement, cancel the 2617 * timer backoff (cf., Phil Karn's retransmit alg.). 2618 * Recompute the initial retransmit timer. 2619 * 2620 * Some boxes send broken timestamp replies 2621 * during the SYN+ACK phase, ignore 2622 * timestamps of 0 or we could calculate a 2623 * huge RTT and blow up the retransmit timer. 2624 */ 2625 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2626 u_int t; 2627 2628 t = tcp_ts_getticks() - to.to_tsecr; 2629 if (!tp->t_rttlow || tp->t_rttlow > t) 2630 tp->t_rttlow = t; 2631 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2632 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2633 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2634 tp->t_rttlow = ticks - tp->t_rtttime; 2635 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2636 } 2637 2638 /* 2639 * If all outstanding data is acked, stop retransmit 2640 * timer and remember to restart (more output or persist). 2641 * If there is more data to be acked, restart retransmit 2642 * timer, using current (possibly backed-off) value. 2643 */ 2644 if (th->th_ack == tp->snd_max) { 2645 tcp_timer_activate(tp, TT_REXMT, 0); 2646 needoutput = 1; 2647 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2648 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2649 2650 /* 2651 * If no data (only SYN) was ACK'd, 2652 * skip rest of ACK processing. 2653 */ 2654 if (acked == 0) 2655 goto step6; 2656 2657 /* 2658 * Let the congestion control algorithm update congestion 2659 * control related information. This typically means increasing 2660 * the congestion window. 2661 */ 2662 cc_ack_received(tp, th, CC_ACK); 2663 2664 SOCKBUF_LOCK(&so->so_snd); 2665 if (acked > so->so_snd.sb_cc) { 2666 tp->snd_wnd -= so->so_snd.sb_cc; 2667 sbdrop_locked(&so->so_snd, (int)so->so_snd.sb_cc); 2668 ourfinisacked = 1; 2669 } else { 2670 sbdrop_locked(&so->so_snd, acked); 2671 tp->snd_wnd -= acked; 2672 ourfinisacked = 0; 2673 } 2674 /* NB: sowwakeup_locked() does an implicit unlock. */ 2675 sowwakeup_locked(so); 2676 /* Detect una wraparound. */ 2677 if (!IN_RECOVERY(tp->t_flags) && 2678 SEQ_GT(tp->snd_una, tp->snd_recover) && 2679 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2680 tp->snd_recover = th->th_ack - 1; 2681 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2682 if (IN_RECOVERY(tp->t_flags) && 2683 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2684 EXIT_RECOVERY(tp->t_flags); 2685 } 2686 tp->snd_una = th->th_ack; 2687 if (tp->t_flags & TF_SACK_PERMIT) { 2688 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2689 tp->snd_recover = tp->snd_una; 2690 } 2691 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2692 tp->snd_nxt = tp->snd_una; 2693 2694 switch (tp->t_state) { 2695 2696 /* 2697 * In FIN_WAIT_1 STATE in addition to the processing 2698 * for the ESTABLISHED state if our FIN is now acknowledged 2699 * then enter FIN_WAIT_2. 2700 */ 2701 case TCPS_FIN_WAIT_1: 2702 if (ourfinisacked) { 2703 /* 2704 * If we can't receive any more 2705 * data, then closing user can proceed. 2706 * Starting the timer is contrary to the 2707 * specification, but if we don't get a FIN 2708 * we'll hang forever. 2709 * 2710 * XXXjl: 2711 * we should release the tp also, and use a 2712 * compressed state. 2713 */ 2714 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2715 soisdisconnected(so); 2716 tcp_timer_activate(tp, TT_2MSL, 2717 (tcp_fast_finwait2_recycle ? 2718 tcp_finwait2_timeout : 2719 TP_MAXIDLE(tp))); 2720 } 2721 tp->t_state = TCPS_FIN_WAIT_2; 2722 } 2723 break; 2724 2725 /* 2726 * In CLOSING STATE in addition to the processing for 2727 * the ESTABLISHED state if the ACK acknowledges our FIN 2728 * then enter the TIME-WAIT state, otherwise ignore 2729 * the segment. 2730 */ 2731 case TCPS_CLOSING: 2732 if (ourfinisacked) { 2733 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2734 tcp_twstart(tp); 2735 INP_INFO_WUNLOCK(&V_tcbinfo); 2736 m_freem(m); 2737 return; 2738 } 2739 break; 2740 2741 /* 2742 * In LAST_ACK, we may still be waiting for data to drain 2743 * and/or to be acked, as well as for the ack of our FIN. 2744 * If our FIN is now acknowledged, delete the TCB, 2745 * enter the closed state and return. 2746 */ 2747 case TCPS_LAST_ACK: 2748 if (ourfinisacked) { 2749 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2750 tp = tcp_close(tp); 2751 goto drop; 2752 } 2753 break; 2754 } 2755 } 2756 2757 step6: 2758 INP_WLOCK_ASSERT(tp->t_inpcb); 2759 2760 /* 2761 * Update window information. 2762 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2763 */ 2764 if ((thflags & TH_ACK) && 2765 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2766 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2767 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2768 /* keep track of pure window updates */ 2769 if (tlen == 0 && 2770 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2771 TCPSTAT_INC(tcps_rcvwinupd); 2772 tp->snd_wnd = tiwin; 2773 tp->snd_wl1 = th->th_seq; 2774 tp->snd_wl2 = th->th_ack; 2775 if (tp->snd_wnd > tp->max_sndwnd) 2776 tp->max_sndwnd = tp->snd_wnd; 2777 needoutput = 1; 2778 } 2779 2780 /* 2781 * Process segments with URG. 2782 */ 2783 if ((thflags & TH_URG) && th->th_urp && 2784 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2785 /* 2786 * This is a kludge, but if we receive and accept 2787 * random urgent pointers, we'll crash in 2788 * soreceive. It's hard to imagine someone 2789 * actually wanting to send this much urgent data. 2790 */ 2791 SOCKBUF_LOCK(&so->so_rcv); 2792 if (th->th_urp + so->so_rcv.sb_cc > sb_max) { 2793 th->th_urp = 0; /* XXX */ 2794 thflags &= ~TH_URG; /* XXX */ 2795 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2796 goto dodata; /* XXX */ 2797 } 2798 /* 2799 * If this segment advances the known urgent pointer, 2800 * then mark the data stream. This should not happen 2801 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2802 * a FIN has been received from the remote side. 2803 * In these states we ignore the URG. 2804 * 2805 * According to RFC961 (Assigned Protocols), 2806 * the urgent pointer points to the last octet 2807 * of urgent data. We continue, however, 2808 * to consider it to indicate the first octet 2809 * of data past the urgent section as the original 2810 * spec states (in one of two places). 2811 */ 2812 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2813 tp->rcv_up = th->th_seq + th->th_urp; 2814 so->so_oobmark = so->so_rcv.sb_cc + 2815 (tp->rcv_up - tp->rcv_nxt) - 1; 2816 if (so->so_oobmark == 0) 2817 so->so_rcv.sb_state |= SBS_RCVATMARK; 2818 sohasoutofband(so); 2819 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2820 } 2821 SOCKBUF_UNLOCK(&so->so_rcv); 2822 /* 2823 * Remove out of band data so doesn't get presented to user. 2824 * This can happen independent of advancing the URG pointer, 2825 * but if two URG's are pending at once, some out-of-band 2826 * data may creep in... ick. 2827 */ 2828 if (th->th_urp <= (u_long)tlen && 2829 !(so->so_options & SO_OOBINLINE)) { 2830 /* hdr drop is delayed */ 2831 tcp_pulloutofband(so, th, m, drop_hdrlen); 2832 } 2833 } else { 2834 /* 2835 * If no out of band data is expected, 2836 * pull receive urgent pointer along 2837 * with the receive window. 2838 */ 2839 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2840 tp->rcv_up = tp->rcv_nxt; 2841 } 2842 dodata: /* XXX */ 2843 INP_WLOCK_ASSERT(tp->t_inpcb); 2844 2845 /* 2846 * Process the segment text, merging it into the TCP sequencing queue, 2847 * and arranging for acknowledgment of receipt if necessary. 2848 * This process logically involves adjusting tp->rcv_wnd as data 2849 * is presented to the user (this happens in tcp_usrreq.c, 2850 * case PRU_RCVD). If a FIN has already been received on this 2851 * connection then we just ignore the text. 2852 */ 2853 if ((tlen || (thflags & TH_FIN)) && 2854 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2855 tcp_seq save_start = th->th_seq; 2856 m_adj(m, drop_hdrlen); /* delayed header drop */ 2857 /* 2858 * Insert segment which includes th into TCP reassembly queue 2859 * with control block tp. Set thflags to whether reassembly now 2860 * includes a segment with FIN. This handles the common case 2861 * inline (segment is the next to be received on an established 2862 * connection, and the queue is empty), avoiding linkage into 2863 * and removal from the queue and repetition of various 2864 * conversions. 2865 * Set DELACK for segments received in order, but ack 2866 * immediately when segments are out of order (so 2867 * fast retransmit can work). 2868 */ 2869 if (th->th_seq == tp->rcv_nxt && 2870 LIST_EMPTY(&tp->t_segq) && 2871 TCPS_HAVEESTABLISHED(tp->t_state)) { 2872 if (DELAY_ACK(tp)) 2873 tp->t_flags |= TF_DELACK; 2874 else 2875 tp->t_flags |= TF_ACKNOW; 2876 tp->rcv_nxt += tlen; 2877 thflags = th->th_flags & TH_FIN; 2878 TCPSTAT_INC(tcps_rcvpack); 2879 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2880 ND6_HINT(tp); 2881 SOCKBUF_LOCK(&so->so_rcv); 2882 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2883 m_freem(m); 2884 else 2885 sbappendstream_locked(&so->so_rcv, m); 2886 /* NB: sorwakeup_locked() does an implicit unlock. */ 2887 sorwakeup_locked(so); 2888 } else { 2889 /* 2890 * XXX: Due to the header drop above "th" is 2891 * theoretically invalid by now. Fortunately 2892 * m_adj() doesn't actually frees any mbufs 2893 * when trimming from the head. 2894 */ 2895 thflags = tcp_reass(tp, th, &tlen, m); 2896 tp->t_flags |= TF_ACKNOW; 2897 } 2898 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2899 tcp_update_sack_list(tp, save_start, save_start + tlen); 2900 #if 0 2901 /* 2902 * Note the amount of data that peer has sent into 2903 * our window, in order to estimate the sender's 2904 * buffer size. 2905 * XXX: Unused. 2906 */ 2907 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 2908 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2909 else 2910 len = so->so_rcv.sb_hiwat; 2911 #endif 2912 } else { 2913 m_freem(m); 2914 thflags &= ~TH_FIN; 2915 } 2916 2917 /* 2918 * If FIN is received ACK the FIN and let the user know 2919 * that the connection is closing. 2920 */ 2921 if (thflags & TH_FIN) { 2922 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2923 socantrcvmore(so); 2924 /* 2925 * If connection is half-synchronized 2926 * (ie NEEDSYN flag on) then delay ACK, 2927 * so it may be piggybacked when SYN is sent. 2928 * Otherwise, since we received a FIN then no 2929 * more input can be expected, send ACK now. 2930 */ 2931 if (tp->t_flags & TF_NEEDSYN) 2932 tp->t_flags |= TF_DELACK; 2933 else 2934 tp->t_flags |= TF_ACKNOW; 2935 tp->rcv_nxt++; 2936 } 2937 switch (tp->t_state) { 2938 2939 /* 2940 * In SYN_RECEIVED and ESTABLISHED STATES 2941 * enter the CLOSE_WAIT state. 2942 */ 2943 case TCPS_SYN_RECEIVED: 2944 tp->t_starttime = ticks; 2945 /* FALLTHROUGH */ 2946 case TCPS_ESTABLISHED: 2947 tp->t_state = TCPS_CLOSE_WAIT; 2948 break; 2949 2950 /* 2951 * If still in FIN_WAIT_1 STATE FIN has not been acked so 2952 * enter the CLOSING state. 2953 */ 2954 case TCPS_FIN_WAIT_1: 2955 tp->t_state = TCPS_CLOSING; 2956 break; 2957 2958 /* 2959 * In FIN_WAIT_2 state enter the TIME_WAIT state, 2960 * starting the time-wait timer, turning off the other 2961 * standard timers. 2962 */ 2963 case TCPS_FIN_WAIT_2: 2964 INP_INFO_WLOCK_ASSERT(&V_tcbinfo); 2965 KASSERT(ti_locked == TI_WLOCKED, ("%s: dodata " 2966 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 2967 ti_locked)); 2968 2969 tcp_twstart(tp); 2970 INP_INFO_WUNLOCK(&V_tcbinfo); 2971 return; 2972 } 2973 } 2974 if (ti_locked == TI_WLOCKED) 2975 INP_INFO_WUNLOCK(&V_tcbinfo); 2976 ti_locked = TI_UNLOCKED; 2977 2978 #ifdef TCPDEBUG 2979 if (so->so_options & SO_DEBUG) 2980 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 2981 &tcp_savetcp, 0); 2982 #endif 2983 2984 /* 2985 * Return any desired output. 2986 */ 2987 if (needoutput || (tp->t_flags & TF_ACKNOW)) 2988 (void) tcp_output(tp); 2989 2990 check_delack: 2991 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 2992 __func__, ti_locked)); 2993 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 2994 INP_WLOCK_ASSERT(tp->t_inpcb); 2995 2996 if (tp->t_flags & TF_DELACK) { 2997 tp->t_flags &= ~TF_DELACK; 2998 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 2999 } 3000 INP_WUNLOCK(tp->t_inpcb); 3001 return; 3002 3003 dropafterack: 3004 /* 3005 * Generate an ACK dropping incoming segment if it occupies 3006 * sequence space, where the ACK reflects our state. 3007 * 3008 * We can now skip the test for the RST flag since all 3009 * paths to this code happen after packets containing 3010 * RST have been dropped. 3011 * 3012 * In the SYN-RECEIVED state, don't send an ACK unless the 3013 * segment we received passes the SYN-RECEIVED ACK test. 3014 * If it fails send a RST. This breaks the loop in the 3015 * "LAND" DoS attack, and also prevents an ACK storm 3016 * between two listening ports that have been sent forged 3017 * SYN segments, each with the source address of the other. 3018 */ 3019 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3020 (SEQ_GT(tp->snd_una, th->th_ack) || 3021 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3022 rstreason = BANDLIM_RST_OPENPORT; 3023 goto dropwithreset; 3024 } 3025 #ifdef TCPDEBUG 3026 if (so->so_options & SO_DEBUG) 3027 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3028 &tcp_savetcp, 0); 3029 #endif 3030 if (ti_locked == TI_WLOCKED) 3031 INP_INFO_WUNLOCK(&V_tcbinfo); 3032 ti_locked = TI_UNLOCKED; 3033 3034 tp->t_flags |= TF_ACKNOW; 3035 (void) tcp_output(tp); 3036 INP_WUNLOCK(tp->t_inpcb); 3037 m_freem(m); 3038 return; 3039 3040 dropwithreset: 3041 if (ti_locked == TI_WLOCKED) 3042 INP_INFO_WUNLOCK(&V_tcbinfo); 3043 ti_locked = TI_UNLOCKED; 3044 3045 if (tp != NULL) { 3046 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3047 INP_WUNLOCK(tp->t_inpcb); 3048 } else 3049 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3050 return; 3051 3052 drop: 3053 if (ti_locked == TI_WLOCKED) { 3054 INP_INFO_WUNLOCK(&V_tcbinfo); 3055 ti_locked = TI_UNLOCKED; 3056 } 3057 #ifdef INVARIANTS 3058 else 3059 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3060 #endif 3061 3062 /* 3063 * Drop space held by incoming segment and return. 3064 */ 3065 #ifdef TCPDEBUG 3066 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3067 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3068 &tcp_savetcp, 0); 3069 #endif 3070 if (tp != NULL) 3071 INP_WUNLOCK(tp->t_inpcb); 3072 m_freem(m); 3073 } 3074 3075 /* 3076 * Issue RST and make ACK acceptable to originator of segment. 3077 * The mbuf must still include the original packet header. 3078 * tp may be NULL. 3079 */ 3080 static void 3081 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3082 int tlen, int rstreason) 3083 { 3084 #ifdef INET 3085 struct ip *ip; 3086 #endif 3087 #ifdef INET6 3088 struct ip6_hdr *ip6; 3089 #endif 3090 3091 if (tp != NULL) { 3092 INP_WLOCK_ASSERT(tp->t_inpcb); 3093 } 3094 3095 /* Don't bother if destination was broadcast/multicast. */ 3096 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3097 goto drop; 3098 #ifdef INET6 3099 if (mtod(m, struct ip *)->ip_v == 6) { 3100 ip6 = mtod(m, struct ip6_hdr *); 3101 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3102 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3103 goto drop; 3104 /* IPv6 anycast check is done at tcp6_input() */ 3105 } 3106 #endif 3107 #if defined(INET) && defined(INET6) 3108 else 3109 #endif 3110 #ifdef INET 3111 { 3112 ip = mtod(m, struct ip *); 3113 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3114 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3115 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3116 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3117 goto drop; 3118 } 3119 #endif 3120 3121 /* Perform bandwidth limiting. */ 3122 if (badport_bandlim(rstreason) < 0) 3123 goto drop; 3124 3125 /* tcp_respond consumes the mbuf chain. */ 3126 if (th->th_flags & TH_ACK) { 3127 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3128 th->th_ack, TH_RST); 3129 } else { 3130 if (th->th_flags & TH_SYN) 3131 tlen++; 3132 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3133 (tcp_seq)0, TH_RST|TH_ACK); 3134 } 3135 return; 3136 drop: 3137 m_freem(m); 3138 } 3139 3140 /* 3141 * Parse TCP options and place in tcpopt. 3142 */ 3143 static void 3144 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3145 { 3146 int opt, optlen; 3147 3148 to->to_flags = 0; 3149 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3150 opt = cp[0]; 3151 if (opt == TCPOPT_EOL) 3152 break; 3153 if (opt == TCPOPT_NOP) 3154 optlen = 1; 3155 else { 3156 if (cnt < 2) 3157 break; 3158 optlen = cp[1]; 3159 if (optlen < 2 || optlen > cnt) 3160 break; 3161 } 3162 switch (opt) { 3163 case TCPOPT_MAXSEG: 3164 if (optlen != TCPOLEN_MAXSEG) 3165 continue; 3166 if (!(flags & TO_SYN)) 3167 continue; 3168 to->to_flags |= TOF_MSS; 3169 bcopy((char *)cp + 2, 3170 (char *)&to->to_mss, sizeof(to->to_mss)); 3171 to->to_mss = ntohs(to->to_mss); 3172 break; 3173 case TCPOPT_WINDOW: 3174 if (optlen != TCPOLEN_WINDOW) 3175 continue; 3176 if (!(flags & TO_SYN)) 3177 continue; 3178 to->to_flags |= TOF_SCALE; 3179 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3180 break; 3181 case TCPOPT_TIMESTAMP: 3182 if (optlen != TCPOLEN_TIMESTAMP) 3183 continue; 3184 to->to_flags |= TOF_TS; 3185 bcopy((char *)cp + 2, 3186 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3187 to->to_tsval = ntohl(to->to_tsval); 3188 bcopy((char *)cp + 6, 3189 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3190 to->to_tsecr = ntohl(to->to_tsecr); 3191 break; 3192 #ifdef TCP_SIGNATURE 3193 /* 3194 * XXX In order to reply to a host which has set the 3195 * TCP_SIGNATURE option in its initial SYN, we have to 3196 * record the fact that the option was observed here 3197 * for the syncache code to perform the correct response. 3198 */ 3199 case TCPOPT_SIGNATURE: 3200 if (optlen != TCPOLEN_SIGNATURE) 3201 continue; 3202 to->to_flags |= TOF_SIGNATURE; 3203 to->to_signature = cp + 2; 3204 break; 3205 #endif 3206 case TCPOPT_SACK_PERMITTED: 3207 if (optlen != TCPOLEN_SACK_PERMITTED) 3208 continue; 3209 if (!(flags & TO_SYN)) 3210 continue; 3211 if (!V_tcp_do_sack) 3212 continue; 3213 to->to_flags |= TOF_SACKPERM; 3214 break; 3215 case TCPOPT_SACK: 3216 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3217 continue; 3218 if (flags & TO_SYN) 3219 continue; 3220 to->to_flags |= TOF_SACK; 3221 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3222 to->to_sacks = cp + 2; 3223 TCPSTAT_INC(tcps_sack_rcv_blocks); 3224 break; 3225 default: 3226 continue; 3227 } 3228 } 3229 } 3230 3231 /* 3232 * Pull out of band byte out of a segment so 3233 * it doesn't appear in the user's data queue. 3234 * It is still reflected in the segment length for 3235 * sequencing purposes. 3236 */ 3237 static void 3238 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3239 int off) 3240 { 3241 int cnt = off + th->th_urp - 1; 3242 3243 while (cnt >= 0) { 3244 if (m->m_len > cnt) { 3245 char *cp = mtod(m, caddr_t) + cnt; 3246 struct tcpcb *tp = sototcpcb(so); 3247 3248 INP_WLOCK_ASSERT(tp->t_inpcb); 3249 3250 tp->t_iobc = *cp; 3251 tp->t_oobflags |= TCPOOB_HAVEDATA; 3252 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3253 m->m_len--; 3254 if (m->m_flags & M_PKTHDR) 3255 m->m_pkthdr.len--; 3256 return; 3257 } 3258 cnt -= m->m_len; 3259 m = m->m_next; 3260 if (m == NULL) 3261 break; 3262 } 3263 panic("tcp_pulloutofband"); 3264 } 3265 3266 /* 3267 * Collect new round-trip time estimate 3268 * and update averages and current timeout. 3269 */ 3270 static void 3271 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3272 { 3273 int delta; 3274 3275 INP_WLOCK_ASSERT(tp->t_inpcb); 3276 3277 TCPSTAT_INC(tcps_rttupdated); 3278 tp->t_rttupdated++; 3279 if (tp->t_srtt != 0) { 3280 /* 3281 * srtt is stored as fixed point with 5 bits after the 3282 * binary point (i.e., scaled by 8). The following magic 3283 * is equivalent to the smoothing algorithm in rfc793 with 3284 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3285 * point). Adjust rtt to origin 0. 3286 */ 3287 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3288 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3289 3290 if ((tp->t_srtt += delta) <= 0) 3291 tp->t_srtt = 1; 3292 3293 /* 3294 * We accumulate a smoothed rtt variance (actually, a 3295 * smoothed mean difference), then set the retransmit 3296 * timer to smoothed rtt + 4 times the smoothed variance. 3297 * rttvar is stored as fixed point with 4 bits after the 3298 * binary point (scaled by 16). The following is 3299 * equivalent to rfc793 smoothing with an alpha of .75 3300 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3301 * rfc793's wired-in beta. 3302 */ 3303 if (delta < 0) 3304 delta = -delta; 3305 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3306 if ((tp->t_rttvar += delta) <= 0) 3307 tp->t_rttvar = 1; 3308 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3309 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3310 } else { 3311 /* 3312 * No rtt measurement yet - use the unsmoothed rtt. 3313 * Set the variance to half the rtt (so our first 3314 * retransmit happens at 3*rtt). 3315 */ 3316 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3317 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3318 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3319 } 3320 tp->t_rtttime = 0; 3321 tp->t_rxtshift = 0; 3322 3323 /* 3324 * the retransmit should happen at rtt + 4 * rttvar. 3325 * Because of the way we do the smoothing, srtt and rttvar 3326 * will each average +1/2 tick of bias. When we compute 3327 * the retransmit timer, we want 1/2 tick of rounding and 3328 * 1 extra tick because of +-1/2 tick uncertainty in the 3329 * firing of the timer. The bias will give us exactly the 3330 * 1.5 tick we need. But, because the bias is 3331 * statistical, we have to test that we don't drop below 3332 * the minimum feasible timer (which is 2 ticks). 3333 */ 3334 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3335 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3336 3337 /* 3338 * We received an ack for a packet that wasn't retransmitted; 3339 * it is probably safe to discard any error indications we've 3340 * received recently. This isn't quite right, but close enough 3341 * for now (a route might have failed after we sent a segment, 3342 * and the return path might not be symmetrical). 3343 */ 3344 tp->t_softerror = 0; 3345 } 3346 3347 /* 3348 * Determine a reasonable value for maxseg size. 3349 * If the route is known, check route for mtu. 3350 * If none, use an mss that can be handled on the outgoing interface 3351 * without forcing IP to fragment. If no route is found, route has no mtu, 3352 * or the destination isn't local, use a default, hopefully conservative 3353 * size (usually 512 or the default IP max size, but no more than the mtu 3354 * of the interface), as we can't discover anything about intervening 3355 * gateways or networks. We also initialize the congestion/slow start 3356 * window to be a single segment if the destination isn't local. 3357 * While looking at the routing entry, we also initialize other path-dependent 3358 * parameters from pre-set or cached values in the routing entry. 3359 * 3360 * Also take into account the space needed for options that we 3361 * send regularly. Make maxseg shorter by that amount to assure 3362 * that we can send maxseg amount of data even when the options 3363 * are present. Store the upper limit of the length of options plus 3364 * data in maxopd. 3365 * 3366 * NOTE that this routine is only called when we process an incoming 3367 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3368 * settings are handled in tcp_mssopt(). 3369 */ 3370 void 3371 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3372 struct hc_metrics_lite *metricptr, int *mtuflags) 3373 { 3374 int mss = 0; 3375 u_long maxmtu = 0; 3376 struct inpcb *inp = tp->t_inpcb; 3377 struct hc_metrics_lite metrics; 3378 int origoffer; 3379 #ifdef INET6 3380 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3381 size_t min_protoh = isipv6 ? 3382 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3383 sizeof (struct tcpiphdr); 3384 #else 3385 const size_t min_protoh = sizeof(struct tcpiphdr); 3386 #endif 3387 3388 INP_WLOCK_ASSERT(tp->t_inpcb); 3389 3390 if (mtuoffer != -1) { 3391 KASSERT(offer == -1, ("%s: conflict", __func__)); 3392 offer = mtuoffer - min_protoh; 3393 } 3394 origoffer = offer; 3395 3396 /* Initialize. */ 3397 #ifdef INET6 3398 if (isipv6) { 3399 maxmtu = tcp_maxmtu6(&inp->inp_inc, mtuflags); 3400 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; 3401 } 3402 #endif 3403 #if defined(INET) && defined(INET6) 3404 else 3405 #endif 3406 #ifdef INET 3407 { 3408 maxmtu = tcp_maxmtu(&inp->inp_inc, mtuflags); 3409 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; 3410 } 3411 #endif 3412 3413 /* 3414 * No route to sender, stay with default mss and return. 3415 */ 3416 if (maxmtu == 0) { 3417 /* 3418 * In case we return early we need to initialize metrics 3419 * to a defined state as tcp_hc_get() would do for us 3420 * if there was no cache hit. 3421 */ 3422 if (metricptr != NULL) 3423 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3424 return; 3425 } 3426 3427 /* What have we got? */ 3428 switch (offer) { 3429 case 0: 3430 /* 3431 * Offer == 0 means that there was no MSS on the SYN 3432 * segment, in this case we use tcp_mssdflt as 3433 * already assigned to t_maxopd above. 3434 */ 3435 offer = tp->t_maxopd; 3436 break; 3437 3438 case -1: 3439 /* 3440 * Offer == -1 means that we didn't receive SYN yet. 3441 */ 3442 /* FALLTHROUGH */ 3443 3444 default: 3445 /* 3446 * Prevent DoS attack with too small MSS. Round up 3447 * to at least minmss. 3448 */ 3449 offer = max(offer, V_tcp_minmss); 3450 } 3451 3452 /* 3453 * rmx information is now retrieved from tcp_hostcache. 3454 */ 3455 tcp_hc_get(&inp->inp_inc, &metrics); 3456 if (metricptr != NULL) 3457 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3458 3459 /* 3460 * If there's a discovered mtu int tcp hostcache, use it 3461 * else, use the link mtu. 3462 */ 3463 if (metrics.rmx_mtu) 3464 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3465 else { 3466 #ifdef INET6 3467 if (isipv6) { 3468 mss = maxmtu - min_protoh; 3469 if (!V_path_mtu_discovery && 3470 !in6_localaddr(&inp->in6p_faddr)) 3471 mss = min(mss, V_tcp_v6mssdflt); 3472 } 3473 #endif 3474 #if defined(INET) && defined(INET6) 3475 else 3476 #endif 3477 #ifdef INET 3478 { 3479 mss = maxmtu - min_protoh; 3480 if (!V_path_mtu_discovery && 3481 !in_localaddr(inp->inp_faddr)) 3482 mss = min(mss, V_tcp_mssdflt); 3483 } 3484 #endif 3485 /* 3486 * XXX - The above conditional (mss = maxmtu - min_protoh) 3487 * probably violates the TCP spec. 3488 * The problem is that, since we don't know the 3489 * other end's MSS, we are supposed to use a conservative 3490 * default. But, if we do that, then MTU discovery will 3491 * never actually take place, because the conservative 3492 * default is much less than the MTUs typically seen 3493 * on the Internet today. For the moment, we'll sweep 3494 * this under the carpet. 3495 * 3496 * The conservative default might not actually be a problem 3497 * if the only case this occurs is when sending an initial 3498 * SYN with options and data to a host we've never talked 3499 * to before. Then, they will reply with an MSS value which 3500 * will get recorded and the new parameters should get 3501 * recomputed. For Further Study. 3502 */ 3503 } 3504 mss = min(mss, offer); 3505 3506 /* 3507 * Sanity check: make sure that maxopd will be large 3508 * enough to allow some data on segments even if the 3509 * all the option space is used (40bytes). Otherwise 3510 * funny things may happen in tcp_output. 3511 */ 3512 mss = max(mss, 64); 3513 3514 /* 3515 * maxopd stores the maximum length of data AND options 3516 * in a segment; maxseg is the amount of data in a normal 3517 * segment. We need to store this value (maxopd) apart 3518 * from maxseg, because now every segment carries options 3519 * and thus we normally have somewhat less data in segments. 3520 */ 3521 tp->t_maxopd = mss; 3522 3523 /* 3524 * origoffer==-1 indicates that no segments were received yet. 3525 * In this case we just guess. 3526 */ 3527 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3528 (origoffer == -1 || 3529 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3530 mss -= TCPOLEN_TSTAMP_APPA; 3531 3532 tp->t_maxseg = mss; 3533 } 3534 3535 void 3536 tcp_mss(struct tcpcb *tp, int offer) 3537 { 3538 int mss; 3539 u_long bufsize; 3540 struct inpcb *inp; 3541 struct socket *so; 3542 struct hc_metrics_lite metrics; 3543 int mtuflags = 0; 3544 3545 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3546 3547 tcp_mss_update(tp, offer, -1, &metrics, &mtuflags); 3548 3549 mss = tp->t_maxseg; 3550 inp = tp->t_inpcb; 3551 3552 /* 3553 * If there's a pipesize, change the socket buffer to that size, 3554 * don't change if sb_hiwat is different than default (then it 3555 * has been changed on purpose with setsockopt). 3556 * Make the socket buffers an integral number of mss units; 3557 * if the mss is larger than the socket buffer, decrease the mss. 3558 */ 3559 so = inp->inp_socket; 3560 SOCKBUF_LOCK(&so->so_snd); 3561 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3562 bufsize = metrics.rmx_sendpipe; 3563 else 3564 bufsize = so->so_snd.sb_hiwat; 3565 if (bufsize < mss) 3566 mss = bufsize; 3567 else { 3568 bufsize = roundup(bufsize, mss); 3569 if (bufsize > sb_max) 3570 bufsize = sb_max; 3571 if (bufsize > so->so_snd.sb_hiwat) 3572 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3573 } 3574 SOCKBUF_UNLOCK(&so->so_snd); 3575 tp->t_maxseg = mss; 3576 3577 SOCKBUF_LOCK(&so->so_rcv); 3578 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3579 bufsize = metrics.rmx_recvpipe; 3580 else 3581 bufsize = so->so_rcv.sb_hiwat; 3582 if (bufsize > mss) { 3583 bufsize = roundup(bufsize, mss); 3584 if (bufsize > sb_max) 3585 bufsize = sb_max; 3586 if (bufsize > so->so_rcv.sb_hiwat) 3587 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3588 } 3589 SOCKBUF_UNLOCK(&so->so_rcv); 3590 3591 /* Check the interface for TSO capabilities. */ 3592 if (mtuflags & CSUM_TSO) 3593 tp->t_flags |= TF_TSO; 3594 } 3595 3596 /* 3597 * Determine the MSS option to send on an outgoing SYN. 3598 */ 3599 int 3600 tcp_mssopt(struct in_conninfo *inc) 3601 { 3602 int mss = 0; 3603 u_long maxmtu = 0; 3604 u_long thcmtu = 0; 3605 size_t min_protoh; 3606 3607 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3608 3609 #ifdef INET6 3610 if (inc->inc_flags & INC_ISIPV6) { 3611 mss = V_tcp_v6mssdflt; 3612 maxmtu = tcp_maxmtu6(inc, NULL); 3613 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3614 } 3615 #endif 3616 #if defined(INET) && defined(INET6) 3617 else 3618 #endif 3619 #ifdef INET 3620 { 3621 mss = V_tcp_mssdflt; 3622 maxmtu = tcp_maxmtu(inc, NULL); 3623 min_protoh = sizeof(struct tcpiphdr); 3624 } 3625 #endif 3626 #if defined(INET6) || defined(INET) 3627 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3628 #endif 3629 3630 if (maxmtu && thcmtu) 3631 mss = min(maxmtu, thcmtu) - min_protoh; 3632 else if (maxmtu || thcmtu) 3633 mss = max(maxmtu, thcmtu) - min_protoh; 3634 3635 return (mss); 3636 } 3637 3638 3639 /* 3640 * On a partial ack arrives, force the retransmission of the 3641 * next unacknowledged segment. Do not clear tp->t_dupacks. 3642 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3643 * be started again. 3644 */ 3645 static void 3646 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3647 { 3648 tcp_seq onxt = tp->snd_nxt; 3649 u_long ocwnd = tp->snd_cwnd; 3650 3651 INP_WLOCK_ASSERT(tp->t_inpcb); 3652 3653 tcp_timer_activate(tp, TT_REXMT, 0); 3654 tp->t_rtttime = 0; 3655 tp->snd_nxt = th->th_ack; 3656 /* 3657 * Set snd_cwnd to one segment beyond acknowledged offset. 3658 * (tp->snd_una has not yet been updated when this function is called.) 3659 */ 3660 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th); 3661 tp->t_flags |= TF_ACKNOW; 3662 (void) tcp_output(tp); 3663 tp->snd_cwnd = ocwnd; 3664 if (SEQ_GT(onxt, tp->snd_nxt)) 3665 tp->snd_nxt = onxt; 3666 /* 3667 * Partial window deflation. Relies on fact that tp->snd_una 3668 * not updated yet. 3669 */ 3670 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3671 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3672 else 3673 tp->snd_cwnd = 0; 3674 tp->snd_cwnd += tp->t_maxseg; 3675 } 3676