1 /*- 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 3 * The Regents of the University of California. All rights reserved. 4 * Copyright (c) 2007-2008,2010 5 * Swinburne University of Technology, Melbourne, Australia. 6 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 7 * Copyright (c) 2010 The FreeBSD Foundation 8 * Copyright (c) 2010-2011 Juniper Networks, Inc. 9 * All rights reserved. 10 * 11 * Portions of this software were developed at the Centre for Advanced Internet 12 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 13 * James Healy and David Hayes, made possible in part by a grant from the Cisco 14 * University Research Program Fund at Community Foundation Silicon Valley. 15 * 16 * Portions of this software were developed at the Centre for Advanced 17 * Internet Architectures, Swinburne University of Technology, Melbourne, 18 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 19 * 20 * Portions of this software were developed by Robert N. M. Watson under 21 * contract to Juniper Networks, Inc. 22 * 23 * Redistribution and use in source and binary forms, with or without 24 * modification, are permitted provided that the following conditions 25 * are met: 26 * 1. Redistributions of source code must retain the above copyright 27 * notice, this list of conditions and the following disclaimer. 28 * 2. Redistributions in binary form must reproduce the above copyright 29 * notice, this list of conditions and the following disclaimer in the 30 * documentation and/or other materials provided with the distribution. 31 * 4. Neither the name of the University nor the names of its contributors 32 * may be used to endorse or promote products derived from this software 33 * without specific prior written permission. 34 * 35 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 36 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 37 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 38 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 39 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 40 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 41 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 42 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 43 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 44 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 45 * SUCH DAMAGE. 46 * 47 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 48 */ 49 50 #include <sys/cdefs.h> 51 __FBSDID("$FreeBSD$"); 52 53 #include "opt_ipfw.h" /* for ipfw_fwd */ 54 #include "opt_inet.h" 55 #include "opt_inet6.h" 56 #include "opt_ipsec.h" 57 #include "opt_tcpdebug.h" 58 59 #include <sys/param.h> 60 #include <sys/kernel.h> 61 #include <sys/hhook.h> 62 #include <sys/malloc.h> 63 #include <sys/mbuf.h> 64 #include <sys/proc.h> /* for proc0 declaration */ 65 #include <sys/protosw.h> 66 #include <sys/sdt.h> 67 #include <sys/signalvar.h> 68 #include <sys/socket.h> 69 #include <sys/socketvar.h> 70 #include <sys/sysctl.h> 71 #include <sys/syslog.h> 72 #include <sys/systm.h> 73 74 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 75 76 #include <vm/uma.h> 77 78 #include <net/if.h> 79 #include <net/if_var.h> 80 #include <net/route.h> 81 #include <net/vnet.h> 82 83 #define TCPSTATES /* for logging */ 84 85 #include <netinet/cc.h> 86 #include <netinet/in.h> 87 #include <netinet/in_kdtrace.h> 88 #include <netinet/in_pcb.h> 89 #include <netinet/in_systm.h> 90 #include <netinet/in_var.h> 91 #include <netinet/ip.h> 92 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 93 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 94 #include <netinet/ip_var.h> 95 #include <netinet/ip_options.h> 96 #include <netinet/ip6.h> 97 #include <netinet/icmp6.h> 98 #include <netinet6/in6_pcb.h> 99 #include <netinet6/ip6_var.h> 100 #include <netinet6/nd6.h> 101 #include <netinet/tcp_fsm.h> 102 #include <netinet/tcp_seq.h> 103 #include <netinet/tcp_timer.h> 104 #include <netinet/tcp_var.h> 105 #include <netinet6/tcp6_var.h> 106 #include <netinet/tcpip.h> 107 #ifdef TCPPCAP 108 #include <netinet/tcp_pcap.h> 109 #endif 110 #include <netinet/tcp_syncache.h> 111 #ifdef TCPDEBUG 112 #include <netinet/tcp_debug.h> 113 #endif /* TCPDEBUG */ 114 #ifdef TCP_OFFLOAD 115 #include <netinet/tcp_offload.h> 116 #endif 117 118 #ifdef IPSEC 119 #include <netipsec/ipsec.h> 120 #include <netipsec/ipsec6.h> 121 #endif /*IPSEC*/ 122 123 #include <machine/in_cksum.h> 124 125 #include <security/mac/mac_framework.h> 126 127 const int tcprexmtthresh = 3; 128 129 int tcp_log_in_vain = 0; 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 131 &tcp_log_in_vain, 0, 132 "Log all incoming TCP segments to closed ports"); 133 134 VNET_DEFINE(int, blackhole) = 0; 135 #define V_blackhole VNET(blackhole) 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 137 &VNET_NAME(blackhole), 0, 138 "Do not send RST on segments to closed ports"); 139 140 VNET_DEFINE(int, tcp_delack_enabled) = 1; 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 142 &VNET_NAME(tcp_delack_enabled), 0, 143 "Delay ACK to try and piggyback it onto a data packet"); 144 145 VNET_DEFINE(int, drop_synfin) = 0; 146 #define V_drop_synfin VNET(drop_synfin) 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 148 &VNET_NAME(drop_synfin), 0, 149 "Drop TCP packets with SYN+FIN set"); 150 151 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 152 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 153 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 154 &VNET_NAME(tcp_do_rfc3042), 0, 155 "Enable RFC 3042 (Limited Transmit)"); 156 157 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 158 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 159 &VNET_NAME(tcp_do_rfc3390), 0, 160 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 161 162 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 164 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 165 "Slow-start flight size (initial congestion window) in number of segments"); 166 167 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 168 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 169 &VNET_NAME(tcp_do_rfc3465), 0, 170 "Enable RFC 3465 (Appropriate Byte Counting)"); 171 172 VNET_DEFINE(int, tcp_abc_l_var) = 2; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 174 &VNET_NAME(tcp_abc_l_var), 2, 175 "Cap the max cwnd increment during slow-start to this number of segments"); 176 177 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 178 179 VNET_DEFINE(int, tcp_do_ecn) = 0; 180 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 181 &VNET_NAME(tcp_do_ecn), 0, 182 "TCP ECN support"); 183 184 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 185 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 186 &VNET_NAME(tcp_ecn_maxretries), 0, 187 "Max retries before giving up on ECN"); 188 189 VNET_DEFINE(int, tcp_insecure_syn) = 0; 190 #define V_tcp_insecure_syn VNET(tcp_insecure_syn) 191 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 192 &VNET_NAME(tcp_insecure_syn), 0, 193 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 194 195 VNET_DEFINE(int, tcp_insecure_rst) = 0; 196 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 197 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 198 &VNET_NAME(tcp_insecure_rst), 0, 199 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 200 201 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 202 #define V_tcp_recvspace VNET(tcp_recvspace) 203 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 204 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 205 206 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 207 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 208 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 209 &VNET_NAME(tcp_do_autorcvbuf), 0, 210 "Enable automatic receive buffer sizing"); 211 212 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 213 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 214 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 215 &VNET_NAME(tcp_autorcvbuf_inc), 0, 216 "Incrementor step size of automatic receive buffer"); 217 218 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 219 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 220 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 221 &VNET_NAME(tcp_autorcvbuf_max), 0, 222 "Max size of automatic receive buffer"); 223 224 VNET_DEFINE(struct inpcbhead, tcb); 225 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 226 VNET_DEFINE(struct inpcbinfo, tcbinfo); 227 228 static void tcp_dooptions(struct tcpopt *, u_char *, int, int); 229 static void tcp_do_segment(struct mbuf *, struct tcphdr *, 230 struct socket *, struct tcpcb *, int, int, uint8_t, 231 int); 232 static void tcp_dropwithreset(struct mbuf *, struct tcphdr *, 233 struct tcpcb *, int, int); 234 static void tcp_pulloutofband(struct socket *, 235 struct tcphdr *, struct mbuf *, int); 236 static void tcp_xmit_timer(struct tcpcb *, int); 237 static void tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *); 238 static void inline cc_ack_received(struct tcpcb *tp, struct tcphdr *th, 239 uint16_t type); 240 static void inline cc_conn_init(struct tcpcb *tp); 241 static void inline cc_post_recovery(struct tcpcb *tp, struct tcphdr *th); 242 static void inline hhook_run_tcp_est_in(struct tcpcb *tp, 243 struct tcphdr *th, struct tcpopt *to); 244 245 /* 246 * TCP statistics are stored in an "array" of counter(9)s. 247 */ 248 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 249 VNET_PCPUSTAT_SYSINIT(tcpstat); 250 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 251 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 252 253 #ifdef VIMAGE 254 VNET_PCPUSTAT_SYSUNINIT(tcpstat); 255 #endif /* VIMAGE */ 256 /* 257 * Kernel module interface for updating tcpstat. The argument is an index 258 * into tcpstat treated as an array. 259 */ 260 void 261 kmod_tcpstat_inc(int statnum) 262 { 263 264 counter_u64_add(VNET(tcpstat)[statnum], 1); 265 } 266 267 /* 268 * Wrapper for the TCP established input helper hook. 269 */ 270 static void inline 271 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 272 { 273 struct tcp_hhook_data hhook_data; 274 275 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 276 hhook_data.tp = tp; 277 hhook_data.th = th; 278 hhook_data.to = to; 279 280 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 281 tp->osd); 282 } 283 } 284 285 /* 286 * CC wrapper hook functions 287 */ 288 static void inline 289 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) 290 { 291 INP_WLOCK_ASSERT(tp->t_inpcb); 292 293 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 294 if (tp->snd_cwnd <= tp->snd_wnd) 295 tp->ccv->flags |= CCF_CWND_LIMITED; 296 else 297 tp->ccv->flags &= ~CCF_CWND_LIMITED; 298 299 if (type == CC_ACK) { 300 if (tp->snd_cwnd > tp->snd_ssthresh) { 301 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 302 V_tcp_abc_l_var * tp->t_maxseg); 303 if (tp->t_bytes_acked >= tp->snd_cwnd) { 304 tp->t_bytes_acked -= tp->snd_cwnd; 305 tp->ccv->flags |= CCF_ABC_SENTAWND; 306 } 307 } else { 308 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 309 tp->t_bytes_acked = 0; 310 } 311 } 312 313 if (CC_ALGO(tp)->ack_received != NULL) { 314 /* XXXLAS: Find a way to live without this */ 315 tp->ccv->curack = th->th_ack; 316 CC_ALGO(tp)->ack_received(tp->ccv, type); 317 } 318 } 319 320 static void inline 321 cc_conn_init(struct tcpcb *tp) 322 { 323 struct hc_metrics_lite metrics; 324 struct inpcb *inp = tp->t_inpcb; 325 int rtt; 326 327 INP_WLOCK_ASSERT(tp->t_inpcb); 328 329 tcp_hc_get(&inp->inp_inc, &metrics); 330 331 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 332 tp->t_srtt = rtt; 333 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 334 TCPSTAT_INC(tcps_usedrtt); 335 if (metrics.rmx_rttvar) { 336 tp->t_rttvar = metrics.rmx_rttvar; 337 TCPSTAT_INC(tcps_usedrttvar); 338 } else { 339 /* default variation is +- 1 rtt */ 340 tp->t_rttvar = 341 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 342 } 343 TCPT_RANGESET(tp->t_rxtcur, 344 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 345 tp->t_rttmin, TCPTV_REXMTMAX); 346 } 347 if (metrics.rmx_ssthresh) { 348 /* 349 * There's some sort of gateway or interface 350 * buffer limit on the path. Use this to set 351 * the slow start threshhold, but set the 352 * threshold to no less than 2*mss. 353 */ 354 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh); 355 TCPSTAT_INC(tcps_usedssthresh); 356 } 357 358 /* 359 * Set the initial slow-start flight size. 360 * 361 * RFC5681 Section 3.1 specifies the default conservative values. 362 * RFC3390 specifies slightly more aggressive values. 363 * RFC6928 increases it to ten segments. 364 * Support for user specified value for initial flight size. 365 * 366 * If a SYN or SYN/ACK was lost and retransmitted, we have to 367 * reduce the initial CWND to one segment as congestion is likely 368 * requiring us to be cautious. 369 */ 370 if (tp->snd_cwnd == 1) 371 tp->snd_cwnd = tp->t_maxseg; /* SYN(-ACK) lost */ 372 else if (V_tcp_initcwnd_segments) 373 tp->snd_cwnd = min(V_tcp_initcwnd_segments * tp->t_maxseg, 374 max(2 * tp->t_maxseg, V_tcp_initcwnd_segments * 1460)); 375 else if (V_tcp_do_rfc3390) 376 tp->snd_cwnd = min(4 * tp->t_maxseg, 377 max(2 * tp->t_maxseg, 4380)); 378 else { 379 /* Per RFC5681 Section 3.1 */ 380 if (tp->t_maxseg > 2190) 381 tp->snd_cwnd = 2 * tp->t_maxseg; 382 else if (tp->t_maxseg > 1095) 383 tp->snd_cwnd = 3 * tp->t_maxseg; 384 else 385 tp->snd_cwnd = 4 * tp->t_maxseg; 386 } 387 388 if (CC_ALGO(tp)->conn_init != NULL) 389 CC_ALGO(tp)->conn_init(tp->ccv); 390 } 391 392 void inline 393 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 394 { 395 INP_WLOCK_ASSERT(tp->t_inpcb); 396 397 switch(type) { 398 case CC_NDUPACK: 399 if (!IN_FASTRECOVERY(tp->t_flags)) { 400 tp->snd_recover = tp->snd_max; 401 if (tp->t_flags & TF_ECN_PERMIT) 402 tp->t_flags |= TF_ECN_SND_CWR; 403 } 404 break; 405 case CC_ECN: 406 if (!IN_CONGRECOVERY(tp->t_flags)) { 407 TCPSTAT_INC(tcps_ecn_rcwnd); 408 tp->snd_recover = tp->snd_max; 409 if (tp->t_flags & TF_ECN_PERMIT) 410 tp->t_flags |= TF_ECN_SND_CWR; 411 } 412 break; 413 case CC_RTO: 414 tp->t_dupacks = 0; 415 tp->t_bytes_acked = 0; 416 EXIT_RECOVERY(tp->t_flags); 417 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 418 tp->t_maxseg) * tp->t_maxseg; 419 tp->snd_cwnd = tp->t_maxseg; 420 break; 421 case CC_RTO_ERR: 422 TCPSTAT_INC(tcps_sndrexmitbad); 423 /* RTO was unnecessary, so reset everything. */ 424 tp->snd_cwnd = tp->snd_cwnd_prev; 425 tp->snd_ssthresh = tp->snd_ssthresh_prev; 426 tp->snd_recover = tp->snd_recover_prev; 427 if (tp->t_flags & TF_WASFRECOVERY) 428 ENTER_FASTRECOVERY(tp->t_flags); 429 if (tp->t_flags & TF_WASCRECOVERY) 430 ENTER_CONGRECOVERY(tp->t_flags); 431 tp->snd_nxt = tp->snd_max; 432 tp->t_flags &= ~TF_PREVVALID; 433 tp->t_badrxtwin = 0; 434 break; 435 } 436 437 if (CC_ALGO(tp)->cong_signal != NULL) { 438 if (th != NULL) 439 tp->ccv->curack = th->th_ack; 440 CC_ALGO(tp)->cong_signal(tp->ccv, type); 441 } 442 } 443 444 static void inline 445 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 446 { 447 INP_WLOCK_ASSERT(tp->t_inpcb); 448 449 /* XXXLAS: KASSERT that we're in recovery? */ 450 451 if (CC_ALGO(tp)->post_recovery != NULL) { 452 tp->ccv->curack = th->th_ack; 453 CC_ALGO(tp)->post_recovery(tp->ccv); 454 } 455 /* XXXLAS: EXIT_RECOVERY ? */ 456 tp->t_bytes_acked = 0; 457 } 458 459 #ifdef TCP_SIGNATURE 460 static inline int 461 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 462 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 463 { 464 int ret; 465 466 tcp_fields_to_net(th); 467 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 468 tcp_fields_to_host(th); 469 return (ret); 470 } 471 #endif 472 473 /* 474 * Indicate whether this ack should be delayed. We can delay the ack if 475 * following conditions are met: 476 * - There is no delayed ack timer in progress. 477 * - Our last ack wasn't a 0-sized window. We never want to delay 478 * the ack that opens up a 0-sized window. 479 * - LRO wasn't used for this segment. We make sure by checking that the 480 * segment size is not larger than the MSS. 481 * - Delayed acks are enabled or this is a half-synchronized T/TCP 482 * connection. 483 */ 484 #define DELAY_ACK(tp, tlen) \ 485 ((!tcp_timer_active(tp, TT_DELACK) && \ 486 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 487 (tlen <= tp->t_maxopd) && \ 488 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 489 490 static void inline 491 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 492 { 493 INP_WLOCK_ASSERT(tp->t_inpcb); 494 495 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 496 switch (iptos & IPTOS_ECN_MASK) { 497 case IPTOS_ECN_CE: 498 tp->ccv->flags |= CCF_IPHDR_CE; 499 break; 500 case IPTOS_ECN_ECT0: 501 tp->ccv->flags &= ~CCF_IPHDR_CE; 502 break; 503 case IPTOS_ECN_ECT1: 504 tp->ccv->flags &= ~CCF_IPHDR_CE; 505 break; 506 } 507 508 if (th->th_flags & TH_CWR) 509 tp->ccv->flags |= CCF_TCPHDR_CWR; 510 else 511 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 512 513 if (tp->t_flags & TF_DELACK) 514 tp->ccv->flags |= CCF_DELACK; 515 else 516 tp->ccv->flags &= ~CCF_DELACK; 517 518 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 519 520 if (tp->ccv->flags & CCF_ACKNOW) 521 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 522 } 523 } 524 525 /* 526 * TCP input handling is split into multiple parts: 527 * tcp6_input is a thin wrapper around tcp_input for the extended 528 * ip6_protox[] call format in ip6_input 529 * tcp_input handles primary segment validation, inpcb lookup and 530 * SYN processing on listen sockets 531 * tcp_do_segment processes the ACK and text of the segment for 532 * establishing, established and closing connections 533 */ 534 #ifdef INET6 535 int 536 tcp6_input(struct mbuf **mp, int *offp, int proto) 537 { 538 struct mbuf *m = *mp; 539 struct in6_ifaddr *ia6; 540 struct ip6_hdr *ip6; 541 542 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 543 544 /* 545 * draft-itojun-ipv6-tcp-to-anycast 546 * better place to put this in? 547 */ 548 ip6 = mtod(m, struct ip6_hdr *); 549 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 550 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 551 struct ip6_hdr *ip6; 552 553 ifa_free(&ia6->ia_ifa); 554 ip6 = mtod(m, struct ip6_hdr *); 555 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 556 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 557 return (IPPROTO_DONE); 558 } 559 if (ia6) 560 ifa_free(&ia6->ia_ifa); 561 562 return (tcp_input(mp, offp, proto)); 563 } 564 #endif /* INET6 */ 565 566 int 567 tcp_input(struct mbuf **mp, int *offp, int proto) 568 { 569 struct mbuf *m = *mp; 570 struct tcphdr *th = NULL; 571 struct ip *ip = NULL; 572 struct inpcb *inp = NULL; 573 struct tcpcb *tp = NULL; 574 struct socket *so = NULL; 575 u_char *optp = NULL; 576 int off0; 577 int optlen = 0; 578 #ifdef INET 579 int len; 580 #endif 581 int tlen = 0, off; 582 int drop_hdrlen; 583 int thflags; 584 int rstreason = 0; /* For badport_bandlim accounting purposes */ 585 #ifdef TCP_SIGNATURE 586 uint8_t sig_checked = 0; 587 #endif 588 uint8_t iptos = 0; 589 struct m_tag *fwd_tag = NULL; 590 #ifdef INET6 591 struct ip6_hdr *ip6 = NULL; 592 int isipv6; 593 #else 594 const void *ip6 = NULL; 595 #endif /* INET6 */ 596 struct tcpopt to; /* options in this segment */ 597 char *s = NULL; /* address and port logging */ 598 int ti_locked; 599 #define TI_UNLOCKED 1 600 #define TI_RLOCKED 2 601 602 #ifdef TCPDEBUG 603 /* 604 * The size of tcp_saveipgen must be the size of the max ip header, 605 * now IPv6. 606 */ 607 u_char tcp_saveipgen[IP6_HDR_LEN]; 608 struct tcphdr tcp_savetcp; 609 short ostate = 0; 610 #endif 611 612 #ifdef INET6 613 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 614 #endif 615 616 off0 = *offp; 617 m = *mp; 618 *mp = NULL; 619 to.to_flags = 0; 620 TCPSTAT_INC(tcps_rcvtotal); 621 622 #ifdef INET6 623 if (isipv6) { 624 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 625 626 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 627 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 628 if (m == NULL) { 629 TCPSTAT_INC(tcps_rcvshort); 630 return (IPPROTO_DONE); 631 } 632 } 633 634 ip6 = mtod(m, struct ip6_hdr *); 635 th = (struct tcphdr *)((caddr_t)ip6 + off0); 636 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 637 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 638 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 639 th->th_sum = m->m_pkthdr.csum_data; 640 else 641 th->th_sum = in6_cksum_pseudo(ip6, tlen, 642 IPPROTO_TCP, m->m_pkthdr.csum_data); 643 th->th_sum ^= 0xffff; 644 } else 645 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 646 if (th->th_sum) { 647 TCPSTAT_INC(tcps_rcvbadsum); 648 goto drop; 649 } 650 651 /* 652 * Be proactive about unspecified IPv6 address in source. 653 * As we use all-zero to indicate unbounded/unconnected pcb, 654 * unspecified IPv6 address can be used to confuse us. 655 * 656 * Note that packets with unspecified IPv6 destination is 657 * already dropped in ip6_input. 658 */ 659 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 660 /* XXX stat */ 661 goto drop; 662 } 663 } 664 #endif 665 #if defined(INET) && defined(INET6) 666 else 667 #endif 668 #ifdef INET 669 { 670 /* 671 * Get IP and TCP header together in first mbuf. 672 * Note: IP leaves IP header in first mbuf. 673 */ 674 if (off0 > sizeof (struct ip)) { 675 ip_stripoptions(m); 676 off0 = sizeof(struct ip); 677 } 678 if (m->m_len < sizeof (struct tcpiphdr)) { 679 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 680 == NULL) { 681 TCPSTAT_INC(tcps_rcvshort); 682 return (IPPROTO_DONE); 683 } 684 } 685 ip = mtod(m, struct ip *); 686 th = (struct tcphdr *)((caddr_t)ip + off0); 687 tlen = ntohs(ip->ip_len) - off0; 688 689 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 690 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 691 th->th_sum = m->m_pkthdr.csum_data; 692 else 693 th->th_sum = in_pseudo(ip->ip_src.s_addr, 694 ip->ip_dst.s_addr, 695 htonl(m->m_pkthdr.csum_data + tlen + 696 IPPROTO_TCP)); 697 th->th_sum ^= 0xffff; 698 } else { 699 struct ipovly *ipov = (struct ipovly *)ip; 700 701 /* 702 * Checksum extended TCP header and data. 703 */ 704 len = off0 + tlen; 705 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 706 ipov->ih_len = htons(tlen); 707 th->th_sum = in_cksum(m, len); 708 /* Reset length for SDT probes. */ 709 ip->ip_len = htons(tlen + off0); 710 } 711 712 if (th->th_sum) { 713 TCPSTAT_INC(tcps_rcvbadsum); 714 goto drop; 715 } 716 /* Re-initialization for later version check */ 717 ip->ip_v = IPVERSION; 718 } 719 #endif /* INET */ 720 721 #ifdef INET6 722 if (isipv6) 723 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 724 #endif 725 #if defined(INET) && defined(INET6) 726 else 727 #endif 728 #ifdef INET 729 iptos = ip->ip_tos; 730 #endif 731 732 /* 733 * Check that TCP offset makes sense, 734 * pull out TCP options and adjust length. XXX 735 */ 736 off = th->th_off << 2; 737 if (off < sizeof (struct tcphdr) || off > tlen) { 738 TCPSTAT_INC(tcps_rcvbadoff); 739 goto drop; 740 } 741 tlen -= off; /* tlen is used instead of ti->ti_len */ 742 if (off > sizeof (struct tcphdr)) { 743 #ifdef INET6 744 if (isipv6) { 745 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 746 ip6 = mtod(m, struct ip6_hdr *); 747 th = (struct tcphdr *)((caddr_t)ip6 + off0); 748 } 749 #endif 750 #if defined(INET) && defined(INET6) 751 else 752 #endif 753 #ifdef INET 754 { 755 if (m->m_len < sizeof(struct ip) + off) { 756 if ((m = m_pullup(m, sizeof (struct ip) + off)) 757 == NULL) { 758 TCPSTAT_INC(tcps_rcvshort); 759 return (IPPROTO_DONE); 760 } 761 ip = mtod(m, struct ip *); 762 th = (struct tcphdr *)((caddr_t)ip + off0); 763 } 764 } 765 #endif 766 optlen = off - sizeof (struct tcphdr); 767 optp = (u_char *)(th + 1); 768 } 769 thflags = th->th_flags; 770 771 /* 772 * Convert TCP protocol specific fields to host format. 773 */ 774 tcp_fields_to_host(th); 775 776 /* 777 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 778 */ 779 drop_hdrlen = off0 + off; 780 781 /* 782 * Locate pcb for segment; if we're likely to add or remove a 783 * connection then first acquire pcbinfo lock. There are three cases 784 * where we might discover later we need a write lock despite the 785 * flags: ACKs moving a connection out of the syncache, ACKs for a 786 * connection in TIMEWAIT and SYNs not targeting a listening socket. 787 */ 788 if ((thflags & (TH_FIN | TH_RST)) != 0) { 789 INP_INFO_RLOCK(&V_tcbinfo); 790 ti_locked = TI_RLOCKED; 791 } else 792 ti_locked = TI_UNLOCKED; 793 794 /* 795 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 796 */ 797 if ( 798 #ifdef INET6 799 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 800 #ifdef INET 801 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 802 #endif 803 #endif 804 #if defined(INET) && !defined(INET6) 805 (m->m_flags & M_IP_NEXTHOP) 806 #endif 807 ) 808 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 809 810 findpcb: 811 #ifdef INVARIANTS 812 if (ti_locked == TI_RLOCKED) { 813 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 814 } else { 815 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 816 } 817 #endif 818 #ifdef INET6 819 if (isipv6 && fwd_tag != NULL) { 820 struct sockaddr_in6 *next_hop6; 821 822 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 823 /* 824 * Transparently forwarded. Pretend to be the destination. 825 * Already got one like this? 826 */ 827 inp = in6_pcblookup_mbuf(&V_tcbinfo, 828 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 829 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 830 if (!inp) { 831 /* 832 * It's new. Try to find the ambushing socket. 833 * Because we've rewritten the destination address, 834 * any hardware-generated hash is ignored. 835 */ 836 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 837 th->th_sport, &next_hop6->sin6_addr, 838 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 839 th->th_dport, INPLOOKUP_WILDCARD | 840 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 841 } 842 } else if (isipv6) { 843 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 844 th->th_sport, &ip6->ip6_dst, th->th_dport, 845 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 846 m->m_pkthdr.rcvif, m); 847 } 848 #endif /* INET6 */ 849 #if defined(INET6) && defined(INET) 850 else 851 #endif 852 #ifdef INET 853 if (fwd_tag != NULL) { 854 struct sockaddr_in *next_hop; 855 856 next_hop = (struct sockaddr_in *)(fwd_tag+1); 857 /* 858 * Transparently forwarded. Pretend to be the destination. 859 * already got one like this? 860 */ 861 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 862 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 863 m->m_pkthdr.rcvif, m); 864 if (!inp) { 865 /* 866 * It's new. Try to find the ambushing socket. 867 * Because we've rewritten the destination address, 868 * any hardware-generated hash is ignored. 869 */ 870 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 871 th->th_sport, next_hop->sin_addr, 872 next_hop->sin_port ? ntohs(next_hop->sin_port) : 873 th->th_dport, INPLOOKUP_WILDCARD | 874 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 875 } 876 } else 877 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 878 th->th_sport, ip->ip_dst, th->th_dport, 879 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 880 m->m_pkthdr.rcvif, m); 881 #endif /* INET */ 882 883 /* 884 * If the INPCB does not exist then all data in the incoming 885 * segment is discarded and an appropriate RST is sent back. 886 * XXX MRT Send RST using which routing table? 887 */ 888 if (inp == NULL) { 889 /* 890 * Log communication attempts to ports that are not 891 * in use. 892 */ 893 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 894 tcp_log_in_vain == 2) { 895 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 896 log(LOG_INFO, "%s; %s: Connection attempt " 897 "to closed port\n", s, __func__); 898 } 899 /* 900 * When blackholing do not respond with a RST but 901 * completely ignore the segment and drop it. 902 */ 903 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 904 V_blackhole == 2) 905 goto dropunlock; 906 907 rstreason = BANDLIM_RST_CLOSEDPORT; 908 goto dropwithreset; 909 } 910 INP_WLOCK_ASSERT(inp); 911 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 912 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 913 ((inp->inp_socket == NULL) || 914 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 915 inp->inp_flowid = m->m_pkthdr.flowid; 916 inp->inp_flowtype = M_HASHTYPE_GET(m); 917 } 918 #ifdef IPSEC 919 #ifdef INET6 920 if (isipv6 && ipsec6_in_reject(m, inp)) { 921 goto dropunlock; 922 } else 923 #endif /* INET6 */ 924 if (ipsec4_in_reject(m, inp) != 0) { 925 goto dropunlock; 926 } 927 #endif /* IPSEC */ 928 929 /* 930 * Check the minimum TTL for socket. 931 */ 932 if (inp->inp_ip_minttl != 0) { 933 #ifdef INET6 934 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim) 935 goto dropunlock; 936 else 937 #endif 938 if (inp->inp_ip_minttl > ip->ip_ttl) 939 goto dropunlock; 940 } 941 942 /* 943 * A previous connection in TIMEWAIT state is supposed to catch stray 944 * or duplicate segments arriving late. If this segment was a 945 * legitimate new connection attempt, the old INPCB gets removed and 946 * we can try again to find a listening socket. 947 * 948 * At this point, due to earlier optimism, we may hold only an inpcb 949 * lock, and not the inpcbinfo write lock. If so, we need to try to 950 * acquire it, or if that fails, acquire a reference on the inpcb, 951 * drop all locks, acquire a global write lock, and then re-acquire 952 * the inpcb lock. We may at that point discover that another thread 953 * has tried to free the inpcb, in which case we need to loop back 954 * and try to find a new inpcb to deliver to. 955 * 956 * XXXRW: It may be time to rethink timewait locking. 957 */ 958 relocked: 959 if (inp->inp_flags & INP_TIMEWAIT) { 960 if (ti_locked == TI_UNLOCKED) { 961 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 962 in_pcbref(inp); 963 INP_WUNLOCK(inp); 964 INP_INFO_RLOCK(&V_tcbinfo); 965 ti_locked = TI_RLOCKED; 966 INP_WLOCK(inp); 967 if (in_pcbrele_wlocked(inp)) { 968 inp = NULL; 969 goto findpcb; 970 } 971 } else 972 ti_locked = TI_RLOCKED; 973 } 974 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 975 976 if (thflags & TH_SYN) 977 tcp_dooptions(&to, optp, optlen, TO_SYN); 978 /* 979 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 980 */ 981 if (tcp_twcheck(inp, &to, th, m, tlen)) 982 goto findpcb; 983 INP_INFO_RUNLOCK(&V_tcbinfo); 984 return (IPPROTO_DONE); 985 } 986 /* 987 * The TCPCB may no longer exist if the connection is winding 988 * down or it is in the CLOSED state. Either way we drop the 989 * segment and send an appropriate response. 990 */ 991 tp = intotcpcb(inp); 992 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 993 rstreason = BANDLIM_RST_CLOSEDPORT; 994 goto dropwithreset; 995 } 996 997 #ifdef TCP_OFFLOAD 998 if (tp->t_flags & TF_TOE) { 999 tcp_offload_input(tp, m); 1000 m = NULL; /* consumed by the TOE driver */ 1001 goto dropunlock; 1002 } 1003 #endif 1004 1005 /* 1006 * We've identified a valid inpcb, but it could be that we need an 1007 * inpcbinfo write lock but don't hold it. In this case, attempt to 1008 * acquire using the same strategy as the TIMEWAIT case above. If we 1009 * relock, we have to jump back to 'relocked' as the connection might 1010 * now be in TIMEWAIT. 1011 */ 1012 #ifdef INVARIANTS 1013 if ((thflags & (TH_FIN | TH_RST)) != 0) 1014 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1015 #endif 1016 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) || 1017 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN)))) { 1018 if (ti_locked == TI_UNLOCKED) { 1019 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 1020 in_pcbref(inp); 1021 INP_WUNLOCK(inp); 1022 INP_INFO_RLOCK(&V_tcbinfo); 1023 ti_locked = TI_RLOCKED; 1024 INP_WLOCK(inp); 1025 if (in_pcbrele_wlocked(inp)) { 1026 inp = NULL; 1027 goto findpcb; 1028 } 1029 goto relocked; 1030 } else 1031 ti_locked = TI_RLOCKED; 1032 } 1033 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1034 } 1035 1036 #ifdef MAC 1037 INP_WLOCK_ASSERT(inp); 1038 if (mac_inpcb_check_deliver(inp, m)) 1039 goto dropunlock; 1040 #endif 1041 so = inp->inp_socket; 1042 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1043 #ifdef TCPDEBUG 1044 if (so->so_options & SO_DEBUG) { 1045 ostate = tp->t_state; 1046 #ifdef INET6 1047 if (isipv6) { 1048 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1049 } else 1050 #endif 1051 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1052 tcp_savetcp = *th; 1053 } 1054 #endif /* TCPDEBUG */ 1055 /* 1056 * When the socket is accepting connections (the INPCB is in LISTEN 1057 * state) we look into the SYN cache if this is a new connection 1058 * attempt or the completion of a previous one. 1059 */ 1060 if (so->so_options & SO_ACCEPTCONN) { 1061 struct in_conninfo inc; 1062 1063 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 1064 "tp not listening", __func__)); 1065 bzero(&inc, sizeof(inc)); 1066 #ifdef INET6 1067 if (isipv6) { 1068 inc.inc_flags |= INC_ISIPV6; 1069 inc.inc6_faddr = ip6->ip6_src; 1070 inc.inc6_laddr = ip6->ip6_dst; 1071 } else 1072 #endif 1073 { 1074 inc.inc_faddr = ip->ip_src; 1075 inc.inc_laddr = ip->ip_dst; 1076 } 1077 inc.inc_fport = th->th_sport; 1078 inc.inc_lport = th->th_dport; 1079 inc.inc_fibnum = so->so_fibnum; 1080 1081 /* 1082 * Check for an existing connection attempt in syncache if 1083 * the flag is only ACK. A successful lookup creates a new 1084 * socket appended to the listen queue in SYN_RECEIVED state. 1085 */ 1086 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1087 1088 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1089 /* 1090 * Parse the TCP options here because 1091 * syncookies need access to the reflected 1092 * timestamp. 1093 */ 1094 tcp_dooptions(&to, optp, optlen, 0); 1095 /* 1096 * NB: syncache_expand() doesn't unlock 1097 * inp and tcpinfo locks. 1098 */ 1099 if (!syncache_expand(&inc, &to, th, &so, m)) { 1100 /* 1101 * No syncache entry or ACK was not 1102 * for our SYN/ACK. Send a RST. 1103 * NB: syncache did its own logging 1104 * of the failure cause. 1105 */ 1106 rstreason = BANDLIM_RST_OPENPORT; 1107 goto dropwithreset; 1108 } 1109 if (so == NULL) { 1110 /* 1111 * We completed the 3-way handshake 1112 * but could not allocate a socket 1113 * either due to memory shortage, 1114 * listen queue length limits or 1115 * global socket limits. Send RST 1116 * or wait and have the remote end 1117 * retransmit the ACK for another 1118 * try. 1119 */ 1120 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1121 log(LOG_DEBUG, "%s; %s: Listen socket: " 1122 "Socket allocation failed due to " 1123 "limits or memory shortage, %s\n", 1124 s, __func__, 1125 V_tcp_sc_rst_sock_fail ? 1126 "sending RST" : "try again"); 1127 if (V_tcp_sc_rst_sock_fail) { 1128 rstreason = BANDLIM_UNLIMITED; 1129 goto dropwithreset; 1130 } else 1131 goto dropunlock; 1132 } 1133 /* 1134 * Socket is created in state SYN_RECEIVED. 1135 * Unlock the listen socket, lock the newly 1136 * created socket and update the tp variable. 1137 */ 1138 INP_WUNLOCK(inp); /* listen socket */ 1139 inp = sotoinpcb(so); 1140 /* 1141 * New connection inpcb is already locked by 1142 * syncache_expand(). 1143 */ 1144 INP_WLOCK_ASSERT(inp); 1145 tp = intotcpcb(inp); 1146 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1147 ("%s: ", __func__)); 1148 #ifdef TCP_SIGNATURE 1149 if (sig_checked == 0) { 1150 tcp_dooptions(&to, optp, optlen, 1151 (thflags & TH_SYN) ? TO_SYN : 0); 1152 if (!tcp_signature_verify_input(m, off0, tlen, 1153 optlen, &to, th, tp->t_flags)) { 1154 1155 /* 1156 * In SYN_SENT state if it receives an 1157 * RST, it is allowed for further 1158 * processing. 1159 */ 1160 if ((thflags & TH_RST) == 0 || 1161 (tp->t_state == TCPS_SYN_SENT) == 0) 1162 goto dropunlock; 1163 } 1164 sig_checked = 1; 1165 } 1166 #endif 1167 1168 /* 1169 * Process the segment and the data it 1170 * contains. tcp_do_segment() consumes 1171 * the mbuf chain and unlocks the inpcb. 1172 */ 1173 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1174 iptos, ti_locked); 1175 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1176 return (IPPROTO_DONE); 1177 } 1178 /* 1179 * Segment flag validation for new connection attempts: 1180 * 1181 * Our (SYN|ACK) response was rejected. 1182 * Check with syncache and remove entry to prevent 1183 * retransmits. 1184 * 1185 * NB: syncache_chkrst does its own logging of failure 1186 * causes. 1187 */ 1188 if (thflags & TH_RST) { 1189 syncache_chkrst(&inc, th); 1190 goto dropunlock; 1191 } 1192 /* 1193 * We can't do anything without SYN. 1194 */ 1195 if ((thflags & TH_SYN) == 0) { 1196 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1197 log(LOG_DEBUG, "%s; %s: Listen socket: " 1198 "SYN is missing, segment ignored\n", 1199 s, __func__); 1200 TCPSTAT_INC(tcps_badsyn); 1201 goto dropunlock; 1202 } 1203 /* 1204 * (SYN|ACK) is bogus on a listen socket. 1205 */ 1206 if (thflags & TH_ACK) { 1207 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1208 log(LOG_DEBUG, "%s; %s: Listen socket: " 1209 "SYN|ACK invalid, segment rejected\n", 1210 s, __func__); 1211 syncache_badack(&inc); /* XXX: Not needed! */ 1212 TCPSTAT_INC(tcps_badsyn); 1213 rstreason = BANDLIM_RST_OPENPORT; 1214 goto dropwithreset; 1215 } 1216 /* 1217 * If the drop_synfin option is enabled, drop all 1218 * segments with both the SYN and FIN bits set. 1219 * This prevents e.g. nmap from identifying the 1220 * TCP/IP stack. 1221 * XXX: Poor reasoning. nmap has other methods 1222 * and is constantly refining its stack detection 1223 * strategies. 1224 * XXX: This is a violation of the TCP specification 1225 * and was used by RFC1644. 1226 */ 1227 if ((thflags & TH_FIN) && V_drop_synfin) { 1228 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1229 log(LOG_DEBUG, "%s; %s: Listen socket: " 1230 "SYN|FIN segment ignored (based on " 1231 "sysctl setting)\n", s, __func__); 1232 TCPSTAT_INC(tcps_badsyn); 1233 goto dropunlock; 1234 } 1235 /* 1236 * Segment's flags are (SYN) or (SYN|FIN). 1237 * 1238 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1239 * as they do not affect the state of the TCP FSM. 1240 * The data pointed to by TH_URG and th_urp is ignored. 1241 */ 1242 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1243 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1244 KASSERT(thflags & (TH_SYN), 1245 ("%s: Listen socket: TH_SYN not set", __func__)); 1246 #ifdef INET6 1247 /* 1248 * If deprecated address is forbidden, 1249 * we do not accept SYN to deprecated interface 1250 * address to prevent any new inbound connection from 1251 * getting established. 1252 * When we do not accept SYN, we send a TCP RST, 1253 * with deprecated source address (instead of dropping 1254 * it). We compromise it as it is much better for peer 1255 * to send a RST, and RST will be the final packet 1256 * for the exchange. 1257 * 1258 * If we do not forbid deprecated addresses, we accept 1259 * the SYN packet. RFC2462 does not suggest dropping 1260 * SYN in this case. 1261 * If we decipher RFC2462 5.5.4, it says like this: 1262 * 1. use of deprecated addr with existing 1263 * communication is okay - "SHOULD continue to be 1264 * used" 1265 * 2. use of it with new communication: 1266 * (2a) "SHOULD NOT be used if alternate address 1267 * with sufficient scope is available" 1268 * (2b) nothing mentioned otherwise. 1269 * Here we fall into (2b) case as we have no choice in 1270 * our source address selection - we must obey the peer. 1271 * 1272 * The wording in RFC2462 is confusing, and there are 1273 * multiple description text for deprecated address 1274 * handling - worse, they are not exactly the same. 1275 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1276 */ 1277 if (isipv6 && !V_ip6_use_deprecated) { 1278 struct in6_ifaddr *ia6; 1279 1280 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1281 if (ia6 != NULL && 1282 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1283 ifa_free(&ia6->ia_ifa); 1284 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1285 log(LOG_DEBUG, "%s; %s: Listen socket: " 1286 "Connection attempt to deprecated " 1287 "IPv6 address rejected\n", 1288 s, __func__); 1289 rstreason = BANDLIM_RST_OPENPORT; 1290 goto dropwithreset; 1291 } 1292 if (ia6) 1293 ifa_free(&ia6->ia_ifa); 1294 } 1295 #endif /* INET6 */ 1296 /* 1297 * Basic sanity checks on incoming SYN requests: 1298 * Don't respond if the destination is a link layer 1299 * broadcast according to RFC1122 4.2.3.10, p. 104. 1300 * If it is from this socket it must be forged. 1301 * Don't respond if the source or destination is a 1302 * global or subnet broad- or multicast address. 1303 * Note that it is quite possible to receive unicast 1304 * link-layer packets with a broadcast IP address. Use 1305 * in_broadcast() to find them. 1306 */ 1307 if (m->m_flags & (M_BCAST|M_MCAST)) { 1308 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1309 log(LOG_DEBUG, "%s; %s: Listen socket: " 1310 "Connection attempt from broad- or multicast " 1311 "link layer address ignored\n", s, __func__); 1312 goto dropunlock; 1313 } 1314 #ifdef INET6 1315 if (isipv6) { 1316 if (th->th_dport == th->th_sport && 1317 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1318 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1319 log(LOG_DEBUG, "%s; %s: Listen socket: " 1320 "Connection attempt to/from self " 1321 "ignored\n", s, __func__); 1322 goto dropunlock; 1323 } 1324 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1325 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1326 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1327 log(LOG_DEBUG, "%s; %s: Listen socket: " 1328 "Connection attempt from/to multicast " 1329 "address ignored\n", s, __func__); 1330 goto dropunlock; 1331 } 1332 } 1333 #endif 1334 #if defined(INET) && defined(INET6) 1335 else 1336 #endif 1337 #ifdef INET 1338 { 1339 if (th->th_dport == th->th_sport && 1340 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1341 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1342 log(LOG_DEBUG, "%s; %s: Listen socket: " 1343 "Connection attempt from/to self " 1344 "ignored\n", s, __func__); 1345 goto dropunlock; 1346 } 1347 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1348 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1349 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1350 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1351 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1352 log(LOG_DEBUG, "%s; %s: Listen socket: " 1353 "Connection attempt from/to broad- " 1354 "or multicast address ignored\n", 1355 s, __func__); 1356 goto dropunlock; 1357 } 1358 } 1359 #endif 1360 /* 1361 * SYN appears to be valid. Create compressed TCP state 1362 * for syncache. 1363 */ 1364 #ifdef TCPDEBUG 1365 if (so->so_options & SO_DEBUG) 1366 tcp_trace(TA_INPUT, ostate, tp, 1367 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1368 #endif 1369 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1370 tcp_dooptions(&to, optp, optlen, TO_SYN); 1371 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1372 /* 1373 * Entry added to syncache and mbuf consumed. 1374 * Only the listen socket is unlocked by syncache_add(). 1375 */ 1376 if (ti_locked == TI_RLOCKED) { 1377 INP_INFO_RUNLOCK(&V_tcbinfo); 1378 ti_locked = TI_UNLOCKED; 1379 } 1380 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1381 return (IPPROTO_DONE); 1382 } else if (tp->t_state == TCPS_LISTEN) { 1383 /* 1384 * When a listen socket is torn down the SO_ACCEPTCONN 1385 * flag is removed first while connections are drained 1386 * from the accept queue in a unlock/lock cycle of the 1387 * ACCEPT_LOCK, opening a race condition allowing a SYN 1388 * attempt go through unhandled. 1389 */ 1390 goto dropunlock; 1391 } 1392 1393 #ifdef TCP_SIGNATURE 1394 if (sig_checked == 0) { 1395 tcp_dooptions(&to, optp, optlen, 1396 (thflags & TH_SYN) ? TO_SYN : 0); 1397 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1398 th, tp->t_flags)) { 1399 1400 /* 1401 * In SYN_SENT state if it receives an RST, it is 1402 * allowed for further processing. 1403 */ 1404 if ((thflags & TH_RST) == 0 || 1405 (tp->t_state == TCPS_SYN_SENT) == 0) 1406 goto dropunlock; 1407 } 1408 sig_checked = 1; 1409 } 1410 #endif 1411 1412 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1413 1414 /* 1415 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1416 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1417 * the inpcb, and unlocks pcbinfo. 1418 */ 1419 tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1420 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1421 return (IPPROTO_DONE); 1422 1423 dropwithreset: 1424 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1425 1426 if (ti_locked == TI_RLOCKED) { 1427 INP_INFO_RUNLOCK(&V_tcbinfo); 1428 ti_locked = TI_UNLOCKED; 1429 } 1430 #ifdef INVARIANTS 1431 else { 1432 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1433 "ti_locked: %d", __func__, ti_locked)); 1434 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1435 } 1436 #endif 1437 1438 if (inp != NULL) { 1439 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1440 INP_WUNLOCK(inp); 1441 } else 1442 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1443 m = NULL; /* mbuf chain got consumed. */ 1444 goto drop; 1445 1446 dropunlock: 1447 if (m != NULL) 1448 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1449 1450 if (ti_locked == TI_RLOCKED) { 1451 INP_INFO_RUNLOCK(&V_tcbinfo); 1452 ti_locked = TI_UNLOCKED; 1453 } 1454 #ifdef INVARIANTS 1455 else { 1456 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1457 "ti_locked: %d", __func__, ti_locked)); 1458 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1459 } 1460 #endif 1461 1462 if (inp != NULL) 1463 INP_WUNLOCK(inp); 1464 1465 drop: 1466 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1467 if (s != NULL) 1468 free(s, M_TCPLOG); 1469 if (m != NULL) 1470 m_freem(m); 1471 return (IPPROTO_DONE); 1472 } 1473 1474 static void 1475 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1476 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1477 int ti_locked) 1478 { 1479 int thflags, acked, ourfinisacked, needoutput = 0; 1480 int rstreason, todrop, win; 1481 u_long tiwin; 1482 char *s; 1483 struct in_conninfo *inc; 1484 struct mbuf *mfree; 1485 struct tcpopt to; 1486 1487 #ifdef TCPDEBUG 1488 /* 1489 * The size of tcp_saveipgen must be the size of the max ip header, 1490 * now IPv6. 1491 */ 1492 u_char tcp_saveipgen[IP6_HDR_LEN]; 1493 struct tcphdr tcp_savetcp; 1494 short ostate = 0; 1495 #endif 1496 thflags = th->th_flags; 1497 inc = &tp->t_inpcb->inp_inc; 1498 tp->sackhint.last_sack_ack = 0; 1499 1500 /* 1501 * If this is either a state-changing packet or current state isn't 1502 * established, we require a write lock on tcbinfo. Otherwise, we 1503 * allow the tcbinfo to be in either alocked or unlocked, as the 1504 * caller may have unnecessarily acquired a write lock due to a race. 1505 */ 1506 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1507 tp->t_state != TCPS_ESTABLISHED) { 1508 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for " 1509 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1510 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1511 } else { 1512 #ifdef INVARIANTS 1513 if (ti_locked == TI_RLOCKED) 1514 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1515 else { 1516 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1517 "ti_locked: %d", __func__, ti_locked)); 1518 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1519 } 1520 #endif 1521 } 1522 INP_WLOCK_ASSERT(tp->t_inpcb); 1523 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1524 __func__)); 1525 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1526 __func__)); 1527 1528 #ifdef TCPPCAP 1529 /* Save segment, if requested. */ 1530 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1531 #endif 1532 1533 /* 1534 * Segment received on connection. 1535 * Reset idle time and keep-alive timer. 1536 * XXX: This should be done after segment 1537 * validation to ignore broken/spoofed segs. 1538 */ 1539 tp->t_rcvtime = ticks; 1540 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1541 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 1542 1543 /* 1544 * Scale up the window into a 32-bit value. 1545 * For the SYN_SENT state the scale is zero. 1546 */ 1547 tiwin = th->th_win << tp->snd_scale; 1548 1549 /* 1550 * TCP ECN processing. 1551 */ 1552 if (tp->t_flags & TF_ECN_PERMIT) { 1553 if (thflags & TH_CWR) 1554 tp->t_flags &= ~TF_ECN_SND_ECE; 1555 switch (iptos & IPTOS_ECN_MASK) { 1556 case IPTOS_ECN_CE: 1557 tp->t_flags |= TF_ECN_SND_ECE; 1558 TCPSTAT_INC(tcps_ecn_ce); 1559 break; 1560 case IPTOS_ECN_ECT0: 1561 TCPSTAT_INC(tcps_ecn_ect0); 1562 break; 1563 case IPTOS_ECN_ECT1: 1564 TCPSTAT_INC(tcps_ecn_ect1); 1565 break; 1566 } 1567 1568 /* Process a packet differently from RFC3168. */ 1569 cc_ecnpkt_handler(tp, th, iptos); 1570 1571 /* Congestion experienced. */ 1572 if (thflags & TH_ECE) { 1573 cc_cong_signal(tp, th, CC_ECN); 1574 } 1575 } 1576 1577 /* 1578 * Parse options on any incoming segment. 1579 */ 1580 tcp_dooptions(&to, (u_char *)(th + 1), 1581 (th->th_off << 2) - sizeof(struct tcphdr), 1582 (thflags & TH_SYN) ? TO_SYN : 0); 1583 1584 /* 1585 * If echoed timestamp is later than the current time, 1586 * fall back to non RFC1323 RTT calculation. Normalize 1587 * timestamp if syncookies were used when this connection 1588 * was established. 1589 */ 1590 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1591 to.to_tsecr -= tp->ts_offset; 1592 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1593 to.to_tsecr = 0; 1594 } 1595 /* 1596 * If timestamps were negotiated during SYN/ACK they should 1597 * appear on every segment during this session and vice versa. 1598 */ 1599 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1600 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1601 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1602 "no action\n", s, __func__); 1603 free(s, M_TCPLOG); 1604 } 1605 } 1606 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1607 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1608 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1609 "no action\n", s, __func__); 1610 free(s, M_TCPLOG); 1611 } 1612 } 1613 1614 /* 1615 * Process options only when we get SYN/ACK back. The SYN case 1616 * for incoming connections is handled in tcp_syncache. 1617 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1618 * or <SYN,ACK>) segment itself is never scaled. 1619 * XXX this is traditional behavior, may need to be cleaned up. 1620 */ 1621 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1622 if ((to.to_flags & TOF_SCALE) && 1623 (tp->t_flags & TF_REQ_SCALE)) { 1624 tp->t_flags |= TF_RCVD_SCALE; 1625 tp->snd_scale = to.to_wscale; 1626 } 1627 /* 1628 * Initial send window. It will be updated with 1629 * the next incoming segment to the scaled value. 1630 */ 1631 tp->snd_wnd = th->th_win; 1632 if (to.to_flags & TOF_TS) { 1633 tp->t_flags |= TF_RCVD_TSTMP; 1634 tp->ts_recent = to.to_tsval; 1635 tp->ts_recent_age = tcp_ts_getticks(); 1636 } 1637 if (to.to_flags & TOF_MSS) 1638 tcp_mss(tp, to.to_mss); 1639 if ((tp->t_flags & TF_SACK_PERMIT) && 1640 (to.to_flags & TOF_SACKPERM) == 0) 1641 tp->t_flags &= ~TF_SACK_PERMIT; 1642 } 1643 1644 /* 1645 * Header prediction: check for the two common cases 1646 * of a uni-directional data xfer. If the packet has 1647 * no control flags, is in-sequence, the window didn't 1648 * change and we're not retransmitting, it's a 1649 * candidate. If the length is zero and the ack moved 1650 * forward, we're the sender side of the xfer. Just 1651 * free the data acked & wake any higher level process 1652 * that was blocked waiting for space. If the length 1653 * is non-zero and the ack didn't move, we're the 1654 * receiver side. If we're getting packets in-order 1655 * (the reassembly queue is empty), add the data to 1656 * the socket buffer and note that we need a delayed ack. 1657 * Make sure that the hidden state-flags are also off. 1658 * Since we check for TCPS_ESTABLISHED first, it can only 1659 * be TH_NEEDSYN. 1660 */ 1661 if (tp->t_state == TCPS_ESTABLISHED && 1662 th->th_seq == tp->rcv_nxt && 1663 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1664 tp->snd_nxt == tp->snd_max && 1665 tiwin && tiwin == tp->snd_wnd && 1666 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1667 LIST_EMPTY(&tp->t_segq) && 1668 ((to.to_flags & TOF_TS) == 0 || 1669 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1670 1671 /* 1672 * If last ACK falls within this segment's sequence numbers, 1673 * record the timestamp. 1674 * NOTE that the test is modified according to the latest 1675 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1676 */ 1677 if ((to.to_flags & TOF_TS) != 0 && 1678 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1679 tp->ts_recent_age = tcp_ts_getticks(); 1680 tp->ts_recent = to.to_tsval; 1681 } 1682 1683 if (tlen == 0) { 1684 if (SEQ_GT(th->th_ack, tp->snd_una) && 1685 SEQ_LEQ(th->th_ack, tp->snd_max) && 1686 !IN_RECOVERY(tp->t_flags) && 1687 (to.to_flags & TOF_SACK) == 0 && 1688 TAILQ_EMPTY(&tp->snd_holes)) { 1689 /* 1690 * This is a pure ack for outstanding data. 1691 */ 1692 if (ti_locked == TI_RLOCKED) 1693 INP_INFO_RUNLOCK(&V_tcbinfo); 1694 ti_locked = TI_UNLOCKED; 1695 1696 TCPSTAT_INC(tcps_predack); 1697 1698 /* 1699 * "bad retransmit" recovery. 1700 */ 1701 if (tp->t_rxtshift == 1 && 1702 tp->t_flags & TF_PREVVALID && 1703 (int)(ticks - tp->t_badrxtwin) < 0) { 1704 cc_cong_signal(tp, th, CC_RTO_ERR); 1705 } 1706 1707 /* 1708 * Recalculate the transmit timer / rtt. 1709 * 1710 * Some boxes send broken timestamp replies 1711 * during the SYN+ACK phase, ignore 1712 * timestamps of 0 or we could calculate a 1713 * huge RTT and blow up the retransmit timer. 1714 */ 1715 if ((to.to_flags & TOF_TS) != 0 && 1716 to.to_tsecr) { 1717 u_int t; 1718 1719 t = tcp_ts_getticks() - to.to_tsecr; 1720 if (!tp->t_rttlow || tp->t_rttlow > t) 1721 tp->t_rttlow = t; 1722 tcp_xmit_timer(tp, 1723 TCP_TS_TO_TICKS(t) + 1); 1724 } else if (tp->t_rtttime && 1725 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1726 if (!tp->t_rttlow || 1727 tp->t_rttlow > ticks - tp->t_rtttime) 1728 tp->t_rttlow = ticks - tp->t_rtttime; 1729 tcp_xmit_timer(tp, 1730 ticks - tp->t_rtttime); 1731 } 1732 acked = BYTES_THIS_ACK(tp, th); 1733 1734 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1735 hhook_run_tcp_est_in(tp, th, &to); 1736 1737 TCPSTAT_INC(tcps_rcvackpack); 1738 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1739 sbdrop(&so->so_snd, acked); 1740 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1741 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1742 tp->snd_recover = th->th_ack - 1; 1743 1744 /* 1745 * Let the congestion control algorithm update 1746 * congestion control related information. This 1747 * typically means increasing the congestion 1748 * window. 1749 */ 1750 cc_ack_received(tp, th, CC_ACK); 1751 1752 tp->snd_una = th->th_ack; 1753 /* 1754 * Pull snd_wl2 up to prevent seq wrap relative 1755 * to th_ack. 1756 */ 1757 tp->snd_wl2 = th->th_ack; 1758 tp->t_dupacks = 0; 1759 m_freem(m); 1760 1761 /* 1762 * If all outstanding data are acked, stop 1763 * retransmit timer, otherwise restart timer 1764 * using current (possibly backed-off) value. 1765 * If process is waiting for space, 1766 * wakeup/selwakeup/signal. If data 1767 * are ready to send, let tcp_output 1768 * decide between more output or persist. 1769 */ 1770 #ifdef TCPDEBUG 1771 if (so->so_options & SO_DEBUG) 1772 tcp_trace(TA_INPUT, ostate, tp, 1773 (void *)tcp_saveipgen, 1774 &tcp_savetcp, 0); 1775 #endif 1776 TCP_PROBE3(debug__input, tp, th, 1777 mtod(m, const char *)); 1778 if (tp->snd_una == tp->snd_max) 1779 tcp_timer_activate(tp, TT_REXMT, 0); 1780 else if (!tcp_timer_active(tp, TT_PERSIST)) 1781 tcp_timer_activate(tp, TT_REXMT, 1782 tp->t_rxtcur); 1783 sowwakeup(so); 1784 if (sbavail(&so->so_snd)) 1785 (void) tcp_output(tp); 1786 goto check_delack; 1787 } 1788 } else if (th->th_ack == tp->snd_una && 1789 tlen <= sbspace(&so->so_rcv)) { 1790 int newsize = 0; /* automatic sockbuf scaling */ 1791 1792 /* 1793 * This is a pure, in-sequence data packet with 1794 * nothing on the reassembly queue and we have enough 1795 * buffer space to take it. 1796 */ 1797 if (ti_locked == TI_RLOCKED) 1798 INP_INFO_RUNLOCK(&V_tcbinfo); 1799 ti_locked = TI_UNLOCKED; 1800 1801 /* Clean receiver SACK report if present */ 1802 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1803 tcp_clean_sackreport(tp); 1804 TCPSTAT_INC(tcps_preddat); 1805 tp->rcv_nxt += tlen; 1806 /* 1807 * Pull snd_wl1 up to prevent seq wrap relative to 1808 * th_seq. 1809 */ 1810 tp->snd_wl1 = th->th_seq; 1811 /* 1812 * Pull rcv_up up to prevent seq wrap relative to 1813 * rcv_nxt. 1814 */ 1815 tp->rcv_up = tp->rcv_nxt; 1816 TCPSTAT_INC(tcps_rcvpack); 1817 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1818 #ifdef TCPDEBUG 1819 if (so->so_options & SO_DEBUG) 1820 tcp_trace(TA_INPUT, ostate, tp, 1821 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1822 #endif 1823 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1824 1825 /* 1826 * Automatic sizing of receive socket buffer. Often the send 1827 * buffer size is not optimally adjusted to the actual network 1828 * conditions at hand (delay bandwidth product). Setting the 1829 * buffer size too small limits throughput on links with high 1830 * bandwidth and high delay (eg. trans-continental/oceanic links). 1831 * 1832 * On the receive side the socket buffer memory is only rarely 1833 * used to any significant extent. This allows us to be much 1834 * more aggressive in scaling the receive socket buffer. For 1835 * the case that the buffer space is actually used to a large 1836 * extent and we run out of kernel memory we can simply drop 1837 * the new segments; TCP on the sender will just retransmit it 1838 * later. Setting the buffer size too big may only consume too 1839 * much kernel memory if the application doesn't read() from 1840 * the socket or packet loss or reordering makes use of the 1841 * reassembly queue. 1842 * 1843 * The criteria to step up the receive buffer one notch are: 1844 * 1. Application has not set receive buffer size with 1845 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1846 * 2. the number of bytes received during the time it takes 1847 * one timestamp to be reflected back to us (the RTT); 1848 * 3. received bytes per RTT is within seven eighth of the 1849 * current socket buffer size; 1850 * 4. receive buffer size has not hit maximal automatic size; 1851 * 1852 * This algorithm does one step per RTT at most and only if 1853 * we receive a bulk stream w/o packet losses or reorderings. 1854 * Shrinking the buffer during idle times is not necessary as 1855 * it doesn't consume any memory when idle. 1856 * 1857 * TODO: Only step up if the application is actually serving 1858 * the buffer to better manage the socket buffer resources. 1859 */ 1860 if (V_tcp_do_autorcvbuf && 1861 (to.to_flags & TOF_TS) && 1862 to.to_tsecr && 1863 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1864 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1865 to.to_tsecr - tp->rfbuf_ts < hz) { 1866 if (tp->rfbuf_cnt > 1867 (so->so_rcv.sb_hiwat / 8 * 7) && 1868 so->so_rcv.sb_hiwat < 1869 V_tcp_autorcvbuf_max) { 1870 newsize = 1871 min(so->so_rcv.sb_hiwat + 1872 V_tcp_autorcvbuf_inc, 1873 V_tcp_autorcvbuf_max); 1874 } 1875 /* Start over with next RTT. */ 1876 tp->rfbuf_ts = 0; 1877 tp->rfbuf_cnt = 0; 1878 } else 1879 tp->rfbuf_cnt += tlen; /* add up */ 1880 } 1881 1882 /* Add data to socket buffer. */ 1883 SOCKBUF_LOCK(&so->so_rcv); 1884 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1885 m_freem(m); 1886 } else { 1887 /* 1888 * Set new socket buffer size. 1889 * Give up when limit is reached. 1890 */ 1891 if (newsize) 1892 if (!sbreserve_locked(&so->so_rcv, 1893 newsize, so, NULL)) 1894 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1895 m_adj(m, drop_hdrlen); /* delayed header drop */ 1896 sbappendstream_locked(&so->so_rcv, m, 0); 1897 } 1898 /* NB: sorwakeup_locked() does an implicit unlock. */ 1899 sorwakeup_locked(so); 1900 if (DELAY_ACK(tp, tlen)) { 1901 tp->t_flags |= TF_DELACK; 1902 } else { 1903 tp->t_flags |= TF_ACKNOW; 1904 tcp_output(tp); 1905 } 1906 goto check_delack; 1907 } 1908 } 1909 1910 /* 1911 * Calculate amount of space in receive window, 1912 * and then do TCP input processing. 1913 * Receive window is amount of space in rcv queue, 1914 * but not less than advertised window. 1915 */ 1916 win = sbspace(&so->so_rcv); 1917 if (win < 0) 1918 win = 0; 1919 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1920 1921 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1922 tp->rfbuf_ts = 0; 1923 tp->rfbuf_cnt = 0; 1924 1925 switch (tp->t_state) { 1926 1927 /* 1928 * If the state is SYN_RECEIVED: 1929 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1930 */ 1931 case TCPS_SYN_RECEIVED: 1932 if ((thflags & TH_ACK) && 1933 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1934 SEQ_GT(th->th_ack, tp->snd_max))) { 1935 rstreason = BANDLIM_RST_OPENPORT; 1936 goto dropwithreset; 1937 } 1938 break; 1939 1940 /* 1941 * If the state is SYN_SENT: 1942 * if seg contains an ACK, but not for our SYN, drop the input. 1943 * if seg contains a RST, then drop the connection. 1944 * if seg does not contain SYN, then drop it. 1945 * Otherwise this is an acceptable SYN segment 1946 * initialize tp->rcv_nxt and tp->irs 1947 * if seg contains ack then advance tp->snd_una 1948 * if seg contains an ECE and ECN support is enabled, the stream 1949 * is ECN capable. 1950 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1951 * arrange for segment to be acked (eventually) 1952 * continue processing rest of data/controls, beginning with URG 1953 */ 1954 case TCPS_SYN_SENT: 1955 if ((thflags & TH_ACK) && 1956 (SEQ_LEQ(th->th_ack, tp->iss) || 1957 SEQ_GT(th->th_ack, tp->snd_max))) { 1958 rstreason = BANDLIM_UNLIMITED; 1959 goto dropwithreset; 1960 } 1961 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1962 TCP_PROBE5(connect__refused, NULL, tp, 1963 mtod(m, const char *), tp, th); 1964 tp = tcp_drop(tp, ECONNREFUSED); 1965 } 1966 if (thflags & TH_RST) 1967 goto drop; 1968 if (!(thflags & TH_SYN)) 1969 goto drop; 1970 1971 tp->irs = th->th_seq; 1972 tcp_rcvseqinit(tp); 1973 if (thflags & TH_ACK) { 1974 TCPSTAT_INC(tcps_connects); 1975 soisconnected(so); 1976 #ifdef MAC 1977 mac_socketpeer_set_from_mbuf(m, so); 1978 #endif 1979 /* Do window scaling on this connection? */ 1980 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1981 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1982 tp->rcv_scale = tp->request_r_scale; 1983 } 1984 tp->rcv_adv += imin(tp->rcv_wnd, 1985 TCP_MAXWIN << tp->rcv_scale); 1986 tp->snd_una++; /* SYN is acked */ 1987 /* 1988 * If there's data, delay ACK; if there's also a FIN 1989 * ACKNOW will be turned on later. 1990 */ 1991 if (DELAY_ACK(tp, tlen) && tlen != 0) 1992 tcp_timer_activate(tp, TT_DELACK, 1993 tcp_delacktime); 1994 else 1995 tp->t_flags |= TF_ACKNOW; 1996 1997 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 1998 tp->t_flags |= TF_ECN_PERMIT; 1999 TCPSTAT_INC(tcps_ecn_shs); 2000 } 2001 2002 /* 2003 * Received <SYN,ACK> in SYN_SENT[*] state. 2004 * Transitions: 2005 * SYN_SENT --> ESTABLISHED 2006 * SYN_SENT* --> FIN_WAIT_1 2007 */ 2008 tp->t_starttime = ticks; 2009 if (tp->t_flags & TF_NEEDFIN) { 2010 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2011 tp->t_flags &= ~TF_NEEDFIN; 2012 thflags &= ~TH_SYN; 2013 } else { 2014 tcp_state_change(tp, TCPS_ESTABLISHED); 2015 TCP_PROBE5(connect__established, NULL, tp, 2016 mtod(m, const char *), tp, th); 2017 cc_conn_init(tp); 2018 tcp_timer_activate(tp, TT_KEEP, 2019 TP_KEEPIDLE(tp)); 2020 } 2021 } else { 2022 /* 2023 * Received initial SYN in SYN-SENT[*] state => 2024 * simultaneous open. 2025 * If it succeeds, connection is * half-synchronized. 2026 * Otherwise, do 3-way handshake: 2027 * SYN-SENT -> SYN-RECEIVED 2028 * SYN-SENT* -> SYN-RECEIVED* 2029 */ 2030 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2031 tcp_timer_activate(tp, TT_REXMT, 0); 2032 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2033 } 2034 2035 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: " 2036 "ti_locked %d", __func__, ti_locked)); 2037 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2038 INP_WLOCK_ASSERT(tp->t_inpcb); 2039 2040 /* 2041 * Advance th->th_seq to correspond to first data byte. 2042 * If data, trim to stay within window, 2043 * dropping FIN if necessary. 2044 */ 2045 th->th_seq++; 2046 if (tlen > tp->rcv_wnd) { 2047 todrop = tlen - tp->rcv_wnd; 2048 m_adj(m, -todrop); 2049 tlen = tp->rcv_wnd; 2050 thflags &= ~TH_FIN; 2051 TCPSTAT_INC(tcps_rcvpackafterwin); 2052 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2053 } 2054 tp->snd_wl1 = th->th_seq - 1; 2055 tp->rcv_up = th->th_seq; 2056 /* 2057 * Client side of transaction: already sent SYN and data. 2058 * If the remote host used T/TCP to validate the SYN, 2059 * our data will be ACK'd; if so, enter normal data segment 2060 * processing in the middle of step 5, ack processing. 2061 * Otherwise, goto step 6. 2062 */ 2063 if (thflags & TH_ACK) 2064 goto process_ACK; 2065 2066 goto step6; 2067 2068 /* 2069 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2070 * do normal processing. 2071 * 2072 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2073 */ 2074 case TCPS_LAST_ACK: 2075 case TCPS_CLOSING: 2076 break; /* continue normal processing */ 2077 } 2078 2079 /* 2080 * States other than LISTEN or SYN_SENT. 2081 * First check the RST flag and sequence number since reset segments 2082 * are exempt from the timestamp and connection count tests. This 2083 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2084 * below which allowed reset segments in half the sequence space 2085 * to fall though and be processed (which gives forged reset 2086 * segments with a random sequence number a 50 percent chance of 2087 * killing a connection). 2088 * Then check timestamp, if present. 2089 * Then check the connection count, if present. 2090 * Then check that at least some bytes of segment are within 2091 * receive window. If segment begins before rcv_nxt, 2092 * drop leading data (and SYN); if nothing left, just ack. 2093 */ 2094 if (thflags & TH_RST) { 2095 /* 2096 * RFC5961 Section 3.2 2097 * 2098 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2099 * - If RST is in window, we send challenge ACK. 2100 * 2101 * Note: to take into account delayed ACKs, we should 2102 * test against last_ack_sent instead of rcv_nxt. 2103 * Note 2: we handle special case of closed window, not 2104 * covered by the RFC. 2105 */ 2106 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2107 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2108 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2109 2110 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2111 KASSERT(ti_locked == TI_RLOCKED, 2112 ("%s: TH_RST ti_locked %d, th %p tp %p", 2113 __func__, ti_locked, th, tp)); 2114 KASSERT(tp->t_state != TCPS_SYN_SENT, 2115 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2116 __func__, th, tp)); 2117 2118 if (V_tcp_insecure_rst || 2119 tp->last_ack_sent == th->th_seq) { 2120 TCPSTAT_INC(tcps_drops); 2121 /* Drop the connection. */ 2122 switch (tp->t_state) { 2123 case TCPS_SYN_RECEIVED: 2124 so->so_error = ECONNREFUSED; 2125 goto close; 2126 case TCPS_ESTABLISHED: 2127 case TCPS_FIN_WAIT_1: 2128 case TCPS_FIN_WAIT_2: 2129 case TCPS_CLOSE_WAIT: 2130 so->so_error = ECONNRESET; 2131 close: 2132 tcp_state_change(tp, TCPS_CLOSED); 2133 /* FALLTHROUGH */ 2134 default: 2135 tp = tcp_close(tp); 2136 } 2137 } else { 2138 TCPSTAT_INC(tcps_badrst); 2139 /* Send challenge ACK. */ 2140 tcp_respond(tp, mtod(m, void *), th, m, 2141 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2142 tp->last_ack_sent = tp->rcv_nxt; 2143 m = NULL; 2144 } 2145 } 2146 goto drop; 2147 } 2148 2149 /* 2150 * RFC5961 Section 4.2 2151 * Send challenge ACK for any SYN in synchronized state. 2152 */ 2153 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT) { 2154 KASSERT(ti_locked == TI_RLOCKED, 2155 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2156 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2157 2158 TCPSTAT_INC(tcps_badsyn); 2159 if (V_tcp_insecure_syn && 2160 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2161 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2162 tp = tcp_drop(tp, ECONNRESET); 2163 rstreason = BANDLIM_UNLIMITED; 2164 } else { 2165 /* Send challenge ACK. */ 2166 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2167 tp->snd_nxt, TH_ACK); 2168 tp->last_ack_sent = tp->rcv_nxt; 2169 m = NULL; 2170 } 2171 goto drop; 2172 } 2173 2174 /* 2175 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2176 * and it's less than ts_recent, drop it. 2177 */ 2178 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2179 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2180 2181 /* Check to see if ts_recent is over 24 days old. */ 2182 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2183 /* 2184 * Invalidate ts_recent. If this segment updates 2185 * ts_recent, the age will be reset later and ts_recent 2186 * will get a valid value. If it does not, setting 2187 * ts_recent to zero will at least satisfy the 2188 * requirement that zero be placed in the timestamp 2189 * echo reply when ts_recent isn't valid. The 2190 * age isn't reset until we get a valid ts_recent 2191 * because we don't want out-of-order segments to be 2192 * dropped when ts_recent is old. 2193 */ 2194 tp->ts_recent = 0; 2195 } else { 2196 TCPSTAT_INC(tcps_rcvduppack); 2197 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2198 TCPSTAT_INC(tcps_pawsdrop); 2199 if (tlen) 2200 goto dropafterack; 2201 goto drop; 2202 } 2203 } 2204 2205 /* 2206 * In the SYN-RECEIVED state, validate that the packet belongs to 2207 * this connection before trimming the data to fit the receive 2208 * window. Check the sequence number versus IRS since we know 2209 * the sequence numbers haven't wrapped. This is a partial fix 2210 * for the "LAND" DoS attack. 2211 */ 2212 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2213 rstreason = BANDLIM_RST_OPENPORT; 2214 goto dropwithreset; 2215 } 2216 2217 todrop = tp->rcv_nxt - th->th_seq; 2218 if (todrop > 0) { 2219 if (thflags & TH_SYN) { 2220 thflags &= ~TH_SYN; 2221 th->th_seq++; 2222 if (th->th_urp > 1) 2223 th->th_urp--; 2224 else 2225 thflags &= ~TH_URG; 2226 todrop--; 2227 } 2228 /* 2229 * Following if statement from Stevens, vol. 2, p. 960. 2230 */ 2231 if (todrop > tlen 2232 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2233 /* 2234 * Any valid FIN must be to the left of the window. 2235 * At this point the FIN must be a duplicate or out 2236 * of sequence; drop it. 2237 */ 2238 thflags &= ~TH_FIN; 2239 2240 /* 2241 * Send an ACK to resynchronize and drop any data. 2242 * But keep on processing for RST or ACK. 2243 */ 2244 tp->t_flags |= TF_ACKNOW; 2245 todrop = tlen; 2246 TCPSTAT_INC(tcps_rcvduppack); 2247 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2248 } else { 2249 TCPSTAT_INC(tcps_rcvpartduppack); 2250 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2251 } 2252 drop_hdrlen += todrop; /* drop from the top afterwards */ 2253 th->th_seq += todrop; 2254 tlen -= todrop; 2255 if (th->th_urp > todrop) 2256 th->th_urp -= todrop; 2257 else { 2258 thflags &= ~TH_URG; 2259 th->th_urp = 0; 2260 } 2261 } 2262 2263 /* 2264 * If new data are received on a connection after the 2265 * user processes are gone, then RST the other end. 2266 */ 2267 if ((so->so_state & SS_NOFDREF) && 2268 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2269 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && " 2270 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2271 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2272 2273 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2274 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2275 "after socket was closed, " 2276 "sending RST and removing tcpcb\n", 2277 s, __func__, tcpstates[tp->t_state], tlen); 2278 free(s, M_TCPLOG); 2279 } 2280 tp = tcp_close(tp); 2281 TCPSTAT_INC(tcps_rcvafterclose); 2282 rstreason = BANDLIM_UNLIMITED; 2283 goto dropwithreset; 2284 } 2285 2286 /* 2287 * If segment ends after window, drop trailing data 2288 * (and PUSH and FIN); if nothing left, just ACK. 2289 */ 2290 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2291 if (todrop > 0) { 2292 TCPSTAT_INC(tcps_rcvpackafterwin); 2293 if (todrop >= tlen) { 2294 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2295 /* 2296 * If window is closed can only take segments at 2297 * window edge, and have to drop data and PUSH from 2298 * incoming segments. Continue processing, but 2299 * remember to ack. Otherwise, drop segment 2300 * and ack. 2301 */ 2302 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2303 tp->t_flags |= TF_ACKNOW; 2304 TCPSTAT_INC(tcps_rcvwinprobe); 2305 } else 2306 goto dropafterack; 2307 } else 2308 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2309 m_adj(m, -todrop); 2310 tlen -= todrop; 2311 thflags &= ~(TH_PUSH|TH_FIN); 2312 } 2313 2314 /* 2315 * If last ACK falls within this segment's sequence numbers, 2316 * record its timestamp. 2317 * NOTE: 2318 * 1) That the test incorporates suggestions from the latest 2319 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2320 * 2) That updating only on newer timestamps interferes with 2321 * our earlier PAWS tests, so this check should be solely 2322 * predicated on the sequence space of this segment. 2323 * 3) That we modify the segment boundary check to be 2324 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2325 * instead of RFC1323's 2326 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2327 * This modified check allows us to overcome RFC1323's 2328 * limitations as described in Stevens TCP/IP Illustrated 2329 * Vol. 2 p.869. In such cases, we can still calculate the 2330 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2331 */ 2332 if ((to.to_flags & TOF_TS) != 0 && 2333 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2334 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2335 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2336 tp->ts_recent_age = tcp_ts_getticks(); 2337 tp->ts_recent = to.to_tsval; 2338 } 2339 2340 /* 2341 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2342 * flag is on (half-synchronized state), then queue data for 2343 * later processing; else drop segment and return. 2344 */ 2345 if ((thflags & TH_ACK) == 0) { 2346 if (tp->t_state == TCPS_SYN_RECEIVED || 2347 (tp->t_flags & TF_NEEDSYN)) 2348 goto step6; 2349 else if (tp->t_flags & TF_ACKNOW) 2350 goto dropafterack; 2351 else 2352 goto drop; 2353 } 2354 2355 /* 2356 * Ack processing. 2357 */ 2358 switch (tp->t_state) { 2359 2360 /* 2361 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2362 * ESTABLISHED state and continue processing. 2363 * The ACK was checked above. 2364 */ 2365 case TCPS_SYN_RECEIVED: 2366 2367 TCPSTAT_INC(tcps_connects); 2368 soisconnected(so); 2369 /* Do window scaling? */ 2370 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2371 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2372 tp->rcv_scale = tp->request_r_scale; 2373 tp->snd_wnd = tiwin; 2374 } 2375 /* 2376 * Make transitions: 2377 * SYN-RECEIVED -> ESTABLISHED 2378 * SYN-RECEIVED* -> FIN-WAIT-1 2379 */ 2380 tp->t_starttime = ticks; 2381 if (tp->t_flags & TF_NEEDFIN) { 2382 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2383 tp->t_flags &= ~TF_NEEDFIN; 2384 } else { 2385 tcp_state_change(tp, TCPS_ESTABLISHED); 2386 TCP_PROBE5(accept__established, NULL, tp, 2387 mtod(m, const char *), tp, th); 2388 cc_conn_init(tp); 2389 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2390 } 2391 /* 2392 * If segment contains data or ACK, will call tcp_reass() 2393 * later; if not, do so now to pass queued data to user. 2394 */ 2395 if (tlen == 0 && (thflags & TH_FIN) == 0) 2396 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2397 (struct mbuf *)0); 2398 tp->snd_wl1 = th->th_seq - 1; 2399 /* FALLTHROUGH */ 2400 2401 /* 2402 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2403 * ACKs. If the ack is in the range 2404 * tp->snd_una < th->th_ack <= tp->snd_max 2405 * then advance tp->snd_una to th->th_ack and drop 2406 * data from the retransmission queue. If this ACK reflects 2407 * more up to date window information we update our window information. 2408 */ 2409 case TCPS_ESTABLISHED: 2410 case TCPS_FIN_WAIT_1: 2411 case TCPS_FIN_WAIT_2: 2412 case TCPS_CLOSE_WAIT: 2413 case TCPS_CLOSING: 2414 case TCPS_LAST_ACK: 2415 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2416 TCPSTAT_INC(tcps_rcvacktoomuch); 2417 goto dropafterack; 2418 } 2419 if ((tp->t_flags & TF_SACK_PERMIT) && 2420 ((to.to_flags & TOF_SACK) || 2421 !TAILQ_EMPTY(&tp->snd_holes))) 2422 tcp_sack_doack(tp, &to, th->th_ack); 2423 2424 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2425 hhook_run_tcp_est_in(tp, th, &to); 2426 2427 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2428 if (tlen == 0 && tiwin == tp->snd_wnd) { 2429 /* 2430 * If this is the first time we've seen a 2431 * FIN from the remote, this is not a 2432 * duplicate and it needs to be processed 2433 * normally. This happens during a 2434 * simultaneous close. 2435 */ 2436 if ((thflags & TH_FIN) && 2437 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2438 tp->t_dupacks = 0; 2439 break; 2440 } 2441 TCPSTAT_INC(tcps_rcvdupack); 2442 /* 2443 * If we have outstanding data (other than 2444 * a window probe), this is a completely 2445 * duplicate ack (ie, window info didn't 2446 * change and FIN isn't set), 2447 * the ack is the biggest we've 2448 * seen and we've seen exactly our rexmt 2449 * threshhold of them, assume a packet 2450 * has been dropped and retransmit it. 2451 * Kludge snd_nxt & the congestion 2452 * window so we send only this one 2453 * packet. 2454 * 2455 * We know we're losing at the current 2456 * window size so do congestion avoidance 2457 * (set ssthresh to half the current window 2458 * and pull our congestion window back to 2459 * the new ssthresh). 2460 * 2461 * Dup acks mean that packets have left the 2462 * network (they're now cached at the receiver) 2463 * so bump cwnd by the amount in the receiver 2464 * to keep a constant cwnd packets in the 2465 * network. 2466 * 2467 * When using TCP ECN, notify the peer that 2468 * we reduced the cwnd. 2469 */ 2470 if (!tcp_timer_active(tp, TT_REXMT) || 2471 th->th_ack != tp->snd_una) 2472 tp->t_dupacks = 0; 2473 else if (++tp->t_dupacks > tcprexmtthresh || 2474 IN_FASTRECOVERY(tp->t_flags)) { 2475 cc_ack_received(tp, th, CC_DUPACK); 2476 if ((tp->t_flags & TF_SACK_PERMIT) && 2477 IN_FASTRECOVERY(tp->t_flags)) { 2478 int awnd; 2479 2480 /* 2481 * Compute the amount of data in flight first. 2482 * We can inject new data into the pipe iff 2483 * we have less than 1/2 the original window's 2484 * worth of data in flight. 2485 */ 2486 awnd = (tp->snd_nxt - tp->snd_fack) + 2487 tp->sackhint.sack_bytes_rexmit; 2488 if (awnd < tp->snd_ssthresh) { 2489 tp->snd_cwnd += tp->t_maxseg; 2490 if (tp->snd_cwnd > tp->snd_ssthresh) 2491 tp->snd_cwnd = tp->snd_ssthresh; 2492 } 2493 } else 2494 tp->snd_cwnd += tp->t_maxseg; 2495 (void) tcp_output(tp); 2496 goto drop; 2497 } else if (tp->t_dupacks == tcprexmtthresh) { 2498 tcp_seq onxt = tp->snd_nxt; 2499 2500 /* 2501 * If we're doing sack, check to 2502 * see if we're already in sack 2503 * recovery. If we're not doing sack, 2504 * check to see if we're in newreno 2505 * recovery. 2506 */ 2507 if (tp->t_flags & TF_SACK_PERMIT) { 2508 if (IN_FASTRECOVERY(tp->t_flags)) { 2509 tp->t_dupacks = 0; 2510 break; 2511 } 2512 } else { 2513 if (SEQ_LEQ(th->th_ack, 2514 tp->snd_recover)) { 2515 tp->t_dupacks = 0; 2516 break; 2517 } 2518 } 2519 /* Congestion signal before ack. */ 2520 cc_cong_signal(tp, th, CC_NDUPACK); 2521 cc_ack_received(tp, th, CC_DUPACK); 2522 tcp_timer_activate(tp, TT_REXMT, 0); 2523 tp->t_rtttime = 0; 2524 if (tp->t_flags & TF_SACK_PERMIT) { 2525 TCPSTAT_INC( 2526 tcps_sack_recovery_episode); 2527 tp->sack_newdata = tp->snd_nxt; 2528 tp->snd_cwnd = tp->t_maxseg; 2529 (void) tcp_output(tp); 2530 goto drop; 2531 } 2532 tp->snd_nxt = th->th_ack; 2533 tp->snd_cwnd = tp->t_maxseg; 2534 (void) tcp_output(tp); 2535 KASSERT(tp->snd_limited <= 2, 2536 ("%s: tp->snd_limited too big", 2537 __func__)); 2538 tp->snd_cwnd = tp->snd_ssthresh + 2539 tp->t_maxseg * 2540 (tp->t_dupacks - tp->snd_limited); 2541 if (SEQ_GT(onxt, tp->snd_nxt)) 2542 tp->snd_nxt = onxt; 2543 goto drop; 2544 } else if (V_tcp_do_rfc3042) { 2545 /* 2546 * Process first and second duplicate 2547 * ACKs. Each indicates a segment 2548 * leaving the network, creating room 2549 * for more. Make sure we can send a 2550 * packet on reception of each duplicate 2551 * ACK by increasing snd_cwnd by one 2552 * segment. Restore the original 2553 * snd_cwnd after packet transmission. 2554 */ 2555 cc_ack_received(tp, th, CC_DUPACK); 2556 u_long oldcwnd = tp->snd_cwnd; 2557 tcp_seq oldsndmax = tp->snd_max; 2558 u_int sent; 2559 int avail; 2560 2561 KASSERT(tp->t_dupacks == 1 || 2562 tp->t_dupacks == 2, 2563 ("%s: dupacks not 1 or 2", 2564 __func__)); 2565 if (tp->t_dupacks == 1) 2566 tp->snd_limited = 0; 2567 tp->snd_cwnd = 2568 (tp->snd_nxt - tp->snd_una) + 2569 (tp->t_dupacks - tp->snd_limited) * 2570 tp->t_maxseg; 2571 /* 2572 * Only call tcp_output when there 2573 * is new data available to be sent. 2574 * Otherwise we would send pure ACKs. 2575 */ 2576 SOCKBUF_LOCK(&so->so_snd); 2577 avail = sbavail(&so->so_snd) - 2578 (tp->snd_nxt - tp->snd_una); 2579 SOCKBUF_UNLOCK(&so->so_snd); 2580 if (avail > 0) 2581 (void) tcp_output(tp); 2582 sent = tp->snd_max - oldsndmax; 2583 if (sent > tp->t_maxseg) { 2584 KASSERT((tp->t_dupacks == 2 && 2585 tp->snd_limited == 0) || 2586 (sent == tp->t_maxseg + 1 && 2587 tp->t_flags & TF_SENTFIN), 2588 ("%s: sent too much", 2589 __func__)); 2590 tp->snd_limited = 2; 2591 } else if (sent > 0) 2592 ++tp->snd_limited; 2593 tp->snd_cwnd = oldcwnd; 2594 goto drop; 2595 } 2596 } else 2597 tp->t_dupacks = 0; 2598 break; 2599 } 2600 2601 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2602 ("%s: th_ack <= snd_una", __func__)); 2603 2604 /* 2605 * If the congestion window was inflated to account 2606 * for the other side's cached packets, retract it. 2607 */ 2608 if (IN_FASTRECOVERY(tp->t_flags)) { 2609 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2610 if (tp->t_flags & TF_SACK_PERMIT) 2611 tcp_sack_partialack(tp, th); 2612 else 2613 tcp_newreno_partial_ack(tp, th); 2614 } else 2615 cc_post_recovery(tp, th); 2616 } 2617 tp->t_dupacks = 0; 2618 /* 2619 * If we reach this point, ACK is not a duplicate, 2620 * i.e., it ACKs something we sent. 2621 */ 2622 if (tp->t_flags & TF_NEEDSYN) { 2623 /* 2624 * T/TCP: Connection was half-synchronized, and our 2625 * SYN has been ACK'd (so connection is now fully 2626 * synchronized). Go to non-starred state, 2627 * increment snd_una for ACK of SYN, and check if 2628 * we can do window scaling. 2629 */ 2630 tp->t_flags &= ~TF_NEEDSYN; 2631 tp->snd_una++; 2632 /* Do window scaling? */ 2633 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2634 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2635 tp->rcv_scale = tp->request_r_scale; 2636 /* Send window already scaled. */ 2637 } 2638 } 2639 2640 process_ACK: 2641 INP_WLOCK_ASSERT(tp->t_inpcb); 2642 2643 acked = BYTES_THIS_ACK(tp, th); 2644 TCPSTAT_INC(tcps_rcvackpack); 2645 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2646 2647 /* 2648 * If we just performed our first retransmit, and the ACK 2649 * arrives within our recovery window, then it was a mistake 2650 * to do the retransmit in the first place. Recover our 2651 * original cwnd and ssthresh, and proceed to transmit where 2652 * we left off. 2653 */ 2654 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2655 (int)(ticks - tp->t_badrxtwin) < 0) 2656 cc_cong_signal(tp, th, CC_RTO_ERR); 2657 2658 /* 2659 * If we have a timestamp reply, update smoothed 2660 * round trip time. If no timestamp is present but 2661 * transmit timer is running and timed sequence 2662 * number was acked, update smoothed round trip time. 2663 * Since we now have an rtt measurement, cancel the 2664 * timer backoff (cf., Phil Karn's retransmit alg.). 2665 * Recompute the initial retransmit timer. 2666 * 2667 * Some boxes send broken timestamp replies 2668 * during the SYN+ACK phase, ignore 2669 * timestamps of 0 or we could calculate a 2670 * huge RTT and blow up the retransmit timer. 2671 */ 2672 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2673 u_int t; 2674 2675 t = tcp_ts_getticks() - to.to_tsecr; 2676 if (!tp->t_rttlow || tp->t_rttlow > t) 2677 tp->t_rttlow = t; 2678 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2679 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2680 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2681 tp->t_rttlow = ticks - tp->t_rtttime; 2682 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2683 } 2684 2685 /* 2686 * If all outstanding data is acked, stop retransmit 2687 * timer and remember to restart (more output or persist). 2688 * If there is more data to be acked, restart retransmit 2689 * timer, using current (possibly backed-off) value. 2690 */ 2691 if (th->th_ack == tp->snd_max) { 2692 tcp_timer_activate(tp, TT_REXMT, 0); 2693 needoutput = 1; 2694 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2695 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2696 2697 /* 2698 * If no data (only SYN) was ACK'd, 2699 * skip rest of ACK processing. 2700 */ 2701 if (acked == 0) 2702 goto step6; 2703 2704 /* 2705 * Let the congestion control algorithm update congestion 2706 * control related information. This typically means increasing 2707 * the congestion window. 2708 */ 2709 cc_ack_received(tp, th, CC_ACK); 2710 2711 SOCKBUF_LOCK(&so->so_snd); 2712 if (acked > sbavail(&so->so_snd)) { 2713 tp->snd_wnd -= sbavail(&so->so_snd); 2714 mfree = sbcut_locked(&so->so_snd, 2715 (int)sbavail(&so->so_snd)); 2716 ourfinisacked = 1; 2717 } else { 2718 mfree = sbcut_locked(&so->so_snd, acked); 2719 tp->snd_wnd -= acked; 2720 ourfinisacked = 0; 2721 } 2722 /* NB: sowwakeup_locked() does an implicit unlock. */ 2723 sowwakeup_locked(so); 2724 m_freem(mfree); 2725 /* Detect una wraparound. */ 2726 if (!IN_RECOVERY(tp->t_flags) && 2727 SEQ_GT(tp->snd_una, tp->snd_recover) && 2728 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2729 tp->snd_recover = th->th_ack - 1; 2730 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2731 if (IN_RECOVERY(tp->t_flags) && 2732 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2733 EXIT_RECOVERY(tp->t_flags); 2734 } 2735 tp->snd_una = th->th_ack; 2736 if (tp->t_flags & TF_SACK_PERMIT) { 2737 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2738 tp->snd_recover = tp->snd_una; 2739 } 2740 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2741 tp->snd_nxt = tp->snd_una; 2742 2743 switch (tp->t_state) { 2744 2745 /* 2746 * In FIN_WAIT_1 STATE in addition to the processing 2747 * for the ESTABLISHED state if our FIN is now acknowledged 2748 * then enter FIN_WAIT_2. 2749 */ 2750 case TCPS_FIN_WAIT_1: 2751 if (ourfinisacked) { 2752 /* 2753 * If we can't receive any more 2754 * data, then closing user can proceed. 2755 * Starting the timer is contrary to the 2756 * specification, but if we don't get a FIN 2757 * we'll hang forever. 2758 * 2759 * XXXjl: 2760 * we should release the tp also, and use a 2761 * compressed state. 2762 */ 2763 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2764 soisdisconnected(so); 2765 tcp_timer_activate(tp, TT_2MSL, 2766 (tcp_fast_finwait2_recycle ? 2767 tcp_finwait2_timeout : 2768 TP_MAXIDLE(tp))); 2769 } 2770 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2771 } 2772 break; 2773 2774 /* 2775 * In CLOSING STATE in addition to the processing for 2776 * the ESTABLISHED state if the ACK acknowledges our FIN 2777 * then enter the TIME-WAIT state, otherwise ignore 2778 * the segment. 2779 */ 2780 case TCPS_CLOSING: 2781 if (ourfinisacked) { 2782 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2783 tcp_twstart(tp); 2784 INP_INFO_RUNLOCK(&V_tcbinfo); 2785 m_freem(m); 2786 return; 2787 } 2788 break; 2789 2790 /* 2791 * In LAST_ACK, we may still be waiting for data to drain 2792 * and/or to be acked, as well as for the ack of our FIN. 2793 * If our FIN is now acknowledged, delete the TCB, 2794 * enter the closed state and return. 2795 */ 2796 case TCPS_LAST_ACK: 2797 if (ourfinisacked) { 2798 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2799 tp = tcp_close(tp); 2800 goto drop; 2801 } 2802 break; 2803 } 2804 } 2805 2806 step6: 2807 INP_WLOCK_ASSERT(tp->t_inpcb); 2808 2809 /* 2810 * Update window information. 2811 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2812 */ 2813 if ((thflags & TH_ACK) && 2814 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2815 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2816 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2817 /* keep track of pure window updates */ 2818 if (tlen == 0 && 2819 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2820 TCPSTAT_INC(tcps_rcvwinupd); 2821 tp->snd_wnd = tiwin; 2822 tp->snd_wl1 = th->th_seq; 2823 tp->snd_wl2 = th->th_ack; 2824 if (tp->snd_wnd > tp->max_sndwnd) 2825 tp->max_sndwnd = tp->snd_wnd; 2826 needoutput = 1; 2827 } 2828 2829 /* 2830 * Process segments with URG. 2831 */ 2832 if ((thflags & TH_URG) && th->th_urp && 2833 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2834 /* 2835 * This is a kludge, but if we receive and accept 2836 * random urgent pointers, we'll crash in 2837 * soreceive. It's hard to imagine someone 2838 * actually wanting to send this much urgent data. 2839 */ 2840 SOCKBUF_LOCK(&so->so_rcv); 2841 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2842 th->th_urp = 0; /* XXX */ 2843 thflags &= ~TH_URG; /* XXX */ 2844 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2845 goto dodata; /* XXX */ 2846 } 2847 /* 2848 * If this segment advances the known urgent pointer, 2849 * then mark the data stream. This should not happen 2850 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2851 * a FIN has been received from the remote side. 2852 * In these states we ignore the URG. 2853 * 2854 * According to RFC961 (Assigned Protocols), 2855 * the urgent pointer points to the last octet 2856 * of urgent data. We continue, however, 2857 * to consider it to indicate the first octet 2858 * of data past the urgent section as the original 2859 * spec states (in one of two places). 2860 */ 2861 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2862 tp->rcv_up = th->th_seq + th->th_urp; 2863 so->so_oobmark = sbavail(&so->so_rcv) + 2864 (tp->rcv_up - tp->rcv_nxt) - 1; 2865 if (so->so_oobmark == 0) 2866 so->so_rcv.sb_state |= SBS_RCVATMARK; 2867 sohasoutofband(so); 2868 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2869 } 2870 SOCKBUF_UNLOCK(&so->so_rcv); 2871 /* 2872 * Remove out of band data so doesn't get presented to user. 2873 * This can happen independent of advancing the URG pointer, 2874 * but if two URG's are pending at once, some out-of-band 2875 * data may creep in... ick. 2876 */ 2877 if (th->th_urp <= (u_long)tlen && 2878 !(so->so_options & SO_OOBINLINE)) { 2879 /* hdr drop is delayed */ 2880 tcp_pulloutofband(so, th, m, drop_hdrlen); 2881 } 2882 } else { 2883 /* 2884 * If no out of band data is expected, 2885 * pull receive urgent pointer along 2886 * with the receive window. 2887 */ 2888 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2889 tp->rcv_up = tp->rcv_nxt; 2890 } 2891 dodata: /* XXX */ 2892 INP_WLOCK_ASSERT(tp->t_inpcb); 2893 2894 /* 2895 * Process the segment text, merging it into the TCP sequencing queue, 2896 * and arranging for acknowledgment of receipt if necessary. 2897 * This process logically involves adjusting tp->rcv_wnd as data 2898 * is presented to the user (this happens in tcp_usrreq.c, 2899 * case PRU_RCVD). If a FIN has already been received on this 2900 * connection then we just ignore the text. 2901 */ 2902 if ((tlen || (thflags & TH_FIN)) && 2903 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2904 tcp_seq save_start = th->th_seq; 2905 m_adj(m, drop_hdrlen); /* delayed header drop */ 2906 /* 2907 * Insert segment which includes th into TCP reassembly queue 2908 * with control block tp. Set thflags to whether reassembly now 2909 * includes a segment with FIN. This handles the common case 2910 * inline (segment is the next to be received on an established 2911 * connection, and the queue is empty), avoiding linkage into 2912 * and removal from the queue and repetition of various 2913 * conversions. 2914 * Set DELACK for segments received in order, but ack 2915 * immediately when segments are out of order (so 2916 * fast retransmit can work). 2917 */ 2918 if (th->th_seq == tp->rcv_nxt && 2919 LIST_EMPTY(&tp->t_segq) && 2920 TCPS_HAVEESTABLISHED(tp->t_state)) { 2921 if (DELAY_ACK(tp, tlen)) 2922 tp->t_flags |= TF_DELACK; 2923 else 2924 tp->t_flags |= TF_ACKNOW; 2925 tp->rcv_nxt += tlen; 2926 thflags = th->th_flags & TH_FIN; 2927 TCPSTAT_INC(tcps_rcvpack); 2928 TCPSTAT_ADD(tcps_rcvbyte, tlen); 2929 SOCKBUF_LOCK(&so->so_rcv); 2930 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 2931 m_freem(m); 2932 else 2933 sbappendstream_locked(&so->so_rcv, m, 0); 2934 /* NB: sorwakeup_locked() does an implicit unlock. */ 2935 sorwakeup_locked(so); 2936 } else { 2937 /* 2938 * XXX: Due to the header drop above "th" is 2939 * theoretically invalid by now. Fortunately 2940 * m_adj() doesn't actually frees any mbufs 2941 * when trimming from the head. 2942 */ 2943 thflags = tcp_reass(tp, th, &tlen, m); 2944 tp->t_flags |= TF_ACKNOW; 2945 } 2946 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 2947 tcp_update_sack_list(tp, save_start, save_start + tlen); 2948 #if 0 2949 /* 2950 * Note the amount of data that peer has sent into 2951 * our window, in order to estimate the sender's 2952 * buffer size. 2953 * XXX: Unused. 2954 */ 2955 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 2956 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 2957 else 2958 len = so->so_rcv.sb_hiwat; 2959 #endif 2960 } else { 2961 m_freem(m); 2962 thflags &= ~TH_FIN; 2963 } 2964 2965 /* 2966 * If FIN is received ACK the FIN and let the user know 2967 * that the connection is closing. 2968 */ 2969 if (thflags & TH_FIN) { 2970 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2971 socantrcvmore(so); 2972 /* 2973 * If connection is half-synchronized 2974 * (ie NEEDSYN flag on) then delay ACK, 2975 * so it may be piggybacked when SYN is sent. 2976 * Otherwise, since we received a FIN then no 2977 * more input can be expected, send ACK now. 2978 */ 2979 if (tp->t_flags & TF_NEEDSYN) 2980 tp->t_flags |= TF_DELACK; 2981 else 2982 tp->t_flags |= TF_ACKNOW; 2983 tp->rcv_nxt++; 2984 } 2985 switch (tp->t_state) { 2986 2987 /* 2988 * In SYN_RECEIVED and ESTABLISHED STATES 2989 * enter the CLOSE_WAIT state. 2990 */ 2991 case TCPS_SYN_RECEIVED: 2992 tp->t_starttime = ticks; 2993 /* FALLTHROUGH */ 2994 case TCPS_ESTABLISHED: 2995 tcp_state_change(tp, TCPS_CLOSE_WAIT); 2996 break; 2997 2998 /* 2999 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3000 * enter the CLOSING state. 3001 */ 3002 case TCPS_FIN_WAIT_1: 3003 tcp_state_change(tp, TCPS_CLOSING); 3004 break; 3005 3006 /* 3007 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3008 * starting the time-wait timer, turning off the other 3009 * standard timers. 3010 */ 3011 case TCPS_FIN_WAIT_2: 3012 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 3013 KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata " 3014 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 3015 ti_locked)); 3016 3017 tcp_twstart(tp); 3018 INP_INFO_RUNLOCK(&V_tcbinfo); 3019 return; 3020 } 3021 } 3022 if (ti_locked == TI_RLOCKED) 3023 INP_INFO_RUNLOCK(&V_tcbinfo); 3024 ti_locked = TI_UNLOCKED; 3025 3026 #ifdef TCPDEBUG 3027 if (so->so_options & SO_DEBUG) 3028 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3029 &tcp_savetcp, 0); 3030 #endif 3031 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3032 3033 /* 3034 * Return any desired output. 3035 */ 3036 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3037 (void) tcp_output(tp); 3038 3039 check_delack: 3040 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3041 __func__, ti_locked)); 3042 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3043 INP_WLOCK_ASSERT(tp->t_inpcb); 3044 3045 if (tp->t_flags & TF_DELACK) { 3046 tp->t_flags &= ~TF_DELACK; 3047 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3048 } 3049 INP_WUNLOCK(tp->t_inpcb); 3050 return; 3051 3052 dropafterack: 3053 /* 3054 * Generate an ACK dropping incoming segment if it occupies 3055 * sequence space, where the ACK reflects our state. 3056 * 3057 * We can now skip the test for the RST flag since all 3058 * paths to this code happen after packets containing 3059 * RST have been dropped. 3060 * 3061 * In the SYN-RECEIVED state, don't send an ACK unless the 3062 * segment we received passes the SYN-RECEIVED ACK test. 3063 * If it fails send a RST. This breaks the loop in the 3064 * "LAND" DoS attack, and also prevents an ACK storm 3065 * between two listening ports that have been sent forged 3066 * SYN segments, each with the source address of the other. 3067 */ 3068 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3069 (SEQ_GT(tp->snd_una, th->th_ack) || 3070 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3071 rstreason = BANDLIM_RST_OPENPORT; 3072 goto dropwithreset; 3073 } 3074 #ifdef TCPDEBUG 3075 if (so->so_options & SO_DEBUG) 3076 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3077 &tcp_savetcp, 0); 3078 #endif 3079 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3080 if (ti_locked == TI_RLOCKED) 3081 INP_INFO_RUNLOCK(&V_tcbinfo); 3082 ti_locked = TI_UNLOCKED; 3083 3084 tp->t_flags |= TF_ACKNOW; 3085 (void) tcp_output(tp); 3086 INP_WUNLOCK(tp->t_inpcb); 3087 m_freem(m); 3088 return; 3089 3090 dropwithreset: 3091 if (ti_locked == TI_RLOCKED) 3092 INP_INFO_RUNLOCK(&V_tcbinfo); 3093 ti_locked = TI_UNLOCKED; 3094 3095 if (tp != NULL) { 3096 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3097 INP_WUNLOCK(tp->t_inpcb); 3098 } else 3099 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3100 return; 3101 3102 drop: 3103 if (ti_locked == TI_RLOCKED) { 3104 INP_INFO_RUNLOCK(&V_tcbinfo); 3105 ti_locked = TI_UNLOCKED; 3106 } 3107 #ifdef INVARIANTS 3108 else 3109 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3110 #endif 3111 3112 /* 3113 * Drop space held by incoming segment and return. 3114 */ 3115 #ifdef TCPDEBUG 3116 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3117 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3118 &tcp_savetcp, 0); 3119 #endif 3120 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3121 if (tp != NULL) 3122 INP_WUNLOCK(tp->t_inpcb); 3123 m_freem(m); 3124 } 3125 3126 /* 3127 * Issue RST and make ACK acceptable to originator of segment. 3128 * The mbuf must still include the original packet header. 3129 * tp may be NULL. 3130 */ 3131 static void 3132 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3133 int tlen, int rstreason) 3134 { 3135 #ifdef INET 3136 struct ip *ip; 3137 #endif 3138 #ifdef INET6 3139 struct ip6_hdr *ip6; 3140 #endif 3141 3142 if (tp != NULL) { 3143 INP_WLOCK_ASSERT(tp->t_inpcb); 3144 } 3145 3146 /* Don't bother if destination was broadcast/multicast. */ 3147 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3148 goto drop; 3149 #ifdef INET6 3150 if (mtod(m, struct ip *)->ip_v == 6) { 3151 ip6 = mtod(m, struct ip6_hdr *); 3152 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3153 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3154 goto drop; 3155 /* IPv6 anycast check is done at tcp6_input() */ 3156 } 3157 #endif 3158 #if defined(INET) && defined(INET6) 3159 else 3160 #endif 3161 #ifdef INET 3162 { 3163 ip = mtod(m, struct ip *); 3164 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3165 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3166 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3167 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3168 goto drop; 3169 } 3170 #endif 3171 3172 /* Perform bandwidth limiting. */ 3173 if (badport_bandlim(rstreason) < 0) 3174 goto drop; 3175 3176 /* tcp_respond consumes the mbuf chain. */ 3177 if (th->th_flags & TH_ACK) { 3178 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3179 th->th_ack, TH_RST); 3180 } else { 3181 if (th->th_flags & TH_SYN) 3182 tlen++; 3183 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3184 (tcp_seq)0, TH_RST|TH_ACK); 3185 } 3186 return; 3187 drop: 3188 m_freem(m); 3189 } 3190 3191 /* 3192 * Parse TCP options and place in tcpopt. 3193 */ 3194 static void 3195 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3196 { 3197 int opt, optlen; 3198 3199 to->to_flags = 0; 3200 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3201 opt = cp[0]; 3202 if (opt == TCPOPT_EOL) 3203 break; 3204 if (opt == TCPOPT_NOP) 3205 optlen = 1; 3206 else { 3207 if (cnt < 2) 3208 break; 3209 optlen = cp[1]; 3210 if (optlen < 2 || optlen > cnt) 3211 break; 3212 } 3213 switch (opt) { 3214 case TCPOPT_MAXSEG: 3215 if (optlen != TCPOLEN_MAXSEG) 3216 continue; 3217 if (!(flags & TO_SYN)) 3218 continue; 3219 to->to_flags |= TOF_MSS; 3220 bcopy((char *)cp + 2, 3221 (char *)&to->to_mss, sizeof(to->to_mss)); 3222 to->to_mss = ntohs(to->to_mss); 3223 break; 3224 case TCPOPT_WINDOW: 3225 if (optlen != TCPOLEN_WINDOW) 3226 continue; 3227 if (!(flags & TO_SYN)) 3228 continue; 3229 to->to_flags |= TOF_SCALE; 3230 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3231 break; 3232 case TCPOPT_TIMESTAMP: 3233 if (optlen != TCPOLEN_TIMESTAMP) 3234 continue; 3235 to->to_flags |= TOF_TS; 3236 bcopy((char *)cp + 2, 3237 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3238 to->to_tsval = ntohl(to->to_tsval); 3239 bcopy((char *)cp + 6, 3240 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3241 to->to_tsecr = ntohl(to->to_tsecr); 3242 break; 3243 #ifdef TCP_SIGNATURE 3244 /* 3245 * XXX In order to reply to a host which has set the 3246 * TCP_SIGNATURE option in its initial SYN, we have to 3247 * record the fact that the option was observed here 3248 * for the syncache code to perform the correct response. 3249 */ 3250 case TCPOPT_SIGNATURE: 3251 if (optlen != TCPOLEN_SIGNATURE) 3252 continue; 3253 to->to_flags |= TOF_SIGNATURE; 3254 to->to_signature = cp + 2; 3255 break; 3256 #endif 3257 case TCPOPT_SACK_PERMITTED: 3258 if (optlen != TCPOLEN_SACK_PERMITTED) 3259 continue; 3260 if (!(flags & TO_SYN)) 3261 continue; 3262 if (!V_tcp_do_sack) 3263 continue; 3264 to->to_flags |= TOF_SACKPERM; 3265 break; 3266 case TCPOPT_SACK: 3267 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3268 continue; 3269 if (flags & TO_SYN) 3270 continue; 3271 to->to_flags |= TOF_SACK; 3272 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3273 to->to_sacks = cp + 2; 3274 TCPSTAT_INC(tcps_sack_rcv_blocks); 3275 break; 3276 default: 3277 continue; 3278 } 3279 } 3280 } 3281 3282 /* 3283 * Pull out of band byte out of a segment so 3284 * it doesn't appear in the user's data queue. 3285 * It is still reflected in the segment length for 3286 * sequencing purposes. 3287 */ 3288 static void 3289 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3290 int off) 3291 { 3292 int cnt = off + th->th_urp - 1; 3293 3294 while (cnt >= 0) { 3295 if (m->m_len > cnt) { 3296 char *cp = mtod(m, caddr_t) + cnt; 3297 struct tcpcb *tp = sototcpcb(so); 3298 3299 INP_WLOCK_ASSERT(tp->t_inpcb); 3300 3301 tp->t_iobc = *cp; 3302 tp->t_oobflags |= TCPOOB_HAVEDATA; 3303 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3304 m->m_len--; 3305 if (m->m_flags & M_PKTHDR) 3306 m->m_pkthdr.len--; 3307 return; 3308 } 3309 cnt -= m->m_len; 3310 m = m->m_next; 3311 if (m == NULL) 3312 break; 3313 } 3314 panic("tcp_pulloutofband"); 3315 } 3316 3317 /* 3318 * Collect new round-trip time estimate 3319 * and update averages and current timeout. 3320 */ 3321 static void 3322 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3323 { 3324 int delta; 3325 3326 INP_WLOCK_ASSERT(tp->t_inpcb); 3327 3328 TCPSTAT_INC(tcps_rttupdated); 3329 tp->t_rttupdated++; 3330 if (tp->t_srtt != 0) { 3331 /* 3332 * srtt is stored as fixed point with 5 bits after the 3333 * binary point (i.e., scaled by 8). The following magic 3334 * is equivalent to the smoothing algorithm in rfc793 with 3335 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3336 * point). Adjust rtt to origin 0. 3337 */ 3338 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3339 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3340 3341 if ((tp->t_srtt += delta) <= 0) 3342 tp->t_srtt = 1; 3343 3344 /* 3345 * We accumulate a smoothed rtt variance (actually, a 3346 * smoothed mean difference), then set the retransmit 3347 * timer to smoothed rtt + 4 times the smoothed variance. 3348 * rttvar is stored as fixed point with 4 bits after the 3349 * binary point (scaled by 16). The following is 3350 * equivalent to rfc793 smoothing with an alpha of .75 3351 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3352 * rfc793's wired-in beta. 3353 */ 3354 if (delta < 0) 3355 delta = -delta; 3356 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3357 if ((tp->t_rttvar += delta) <= 0) 3358 tp->t_rttvar = 1; 3359 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3360 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3361 } else { 3362 /* 3363 * No rtt measurement yet - use the unsmoothed rtt. 3364 * Set the variance to half the rtt (so our first 3365 * retransmit happens at 3*rtt). 3366 */ 3367 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3368 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3369 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3370 } 3371 tp->t_rtttime = 0; 3372 tp->t_rxtshift = 0; 3373 3374 /* 3375 * the retransmit should happen at rtt + 4 * rttvar. 3376 * Because of the way we do the smoothing, srtt and rttvar 3377 * will each average +1/2 tick of bias. When we compute 3378 * the retransmit timer, we want 1/2 tick of rounding and 3379 * 1 extra tick because of +-1/2 tick uncertainty in the 3380 * firing of the timer. The bias will give us exactly the 3381 * 1.5 tick we need. But, because the bias is 3382 * statistical, we have to test that we don't drop below 3383 * the minimum feasible timer (which is 2 ticks). 3384 */ 3385 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3386 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3387 3388 /* 3389 * We received an ack for a packet that wasn't retransmitted; 3390 * it is probably safe to discard any error indications we've 3391 * received recently. This isn't quite right, but close enough 3392 * for now (a route might have failed after we sent a segment, 3393 * and the return path might not be symmetrical). 3394 */ 3395 tp->t_softerror = 0; 3396 } 3397 3398 /* 3399 * Determine a reasonable value for maxseg size. 3400 * If the route is known, check route for mtu. 3401 * If none, use an mss that can be handled on the outgoing interface 3402 * without forcing IP to fragment. If no route is found, route has no mtu, 3403 * or the destination isn't local, use a default, hopefully conservative 3404 * size (usually 512 or the default IP max size, but no more than the mtu 3405 * of the interface), as we can't discover anything about intervening 3406 * gateways or networks. We also initialize the congestion/slow start 3407 * window to be a single segment if the destination isn't local. 3408 * While looking at the routing entry, we also initialize other path-dependent 3409 * parameters from pre-set or cached values in the routing entry. 3410 * 3411 * Also take into account the space needed for options that we 3412 * send regularly. Make maxseg shorter by that amount to assure 3413 * that we can send maxseg amount of data even when the options 3414 * are present. Store the upper limit of the length of options plus 3415 * data in maxopd. 3416 * 3417 * NOTE that this routine is only called when we process an incoming 3418 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3419 * settings are handled in tcp_mssopt(). 3420 */ 3421 void 3422 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3423 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3424 { 3425 int mss = 0; 3426 u_long maxmtu = 0; 3427 struct inpcb *inp = tp->t_inpcb; 3428 struct hc_metrics_lite metrics; 3429 int origoffer; 3430 #ifdef INET6 3431 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3432 size_t min_protoh = isipv6 ? 3433 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3434 sizeof (struct tcpiphdr); 3435 #else 3436 const size_t min_protoh = sizeof(struct tcpiphdr); 3437 #endif 3438 3439 INP_WLOCK_ASSERT(tp->t_inpcb); 3440 3441 if (mtuoffer != -1) { 3442 KASSERT(offer == -1, ("%s: conflict", __func__)); 3443 offer = mtuoffer - min_protoh; 3444 } 3445 origoffer = offer; 3446 3447 /* Initialize. */ 3448 #ifdef INET6 3449 if (isipv6) { 3450 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3451 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt; 3452 } 3453 #endif 3454 #if defined(INET) && defined(INET6) 3455 else 3456 #endif 3457 #ifdef INET 3458 { 3459 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3460 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt; 3461 } 3462 #endif 3463 3464 /* 3465 * No route to sender, stay with default mss and return. 3466 */ 3467 if (maxmtu == 0) { 3468 /* 3469 * In case we return early we need to initialize metrics 3470 * to a defined state as tcp_hc_get() would do for us 3471 * if there was no cache hit. 3472 */ 3473 if (metricptr != NULL) 3474 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3475 return; 3476 } 3477 3478 /* What have we got? */ 3479 switch (offer) { 3480 case 0: 3481 /* 3482 * Offer == 0 means that there was no MSS on the SYN 3483 * segment, in this case we use tcp_mssdflt as 3484 * already assigned to t_maxopd above. 3485 */ 3486 offer = tp->t_maxopd; 3487 break; 3488 3489 case -1: 3490 /* 3491 * Offer == -1 means that we didn't receive SYN yet. 3492 */ 3493 /* FALLTHROUGH */ 3494 3495 default: 3496 /* 3497 * Prevent DoS attack with too small MSS. Round up 3498 * to at least minmss. 3499 */ 3500 offer = max(offer, V_tcp_minmss); 3501 } 3502 3503 /* 3504 * rmx information is now retrieved from tcp_hostcache. 3505 */ 3506 tcp_hc_get(&inp->inp_inc, &metrics); 3507 if (metricptr != NULL) 3508 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3509 3510 /* 3511 * If there's a discovered mtu in tcp hostcache, use it. 3512 * Else, use the link mtu. 3513 */ 3514 if (metrics.rmx_mtu) 3515 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3516 else { 3517 #ifdef INET6 3518 if (isipv6) { 3519 mss = maxmtu - min_protoh; 3520 if (!V_path_mtu_discovery && 3521 !in6_localaddr(&inp->in6p_faddr)) 3522 mss = min(mss, V_tcp_v6mssdflt); 3523 } 3524 #endif 3525 #if defined(INET) && defined(INET6) 3526 else 3527 #endif 3528 #ifdef INET 3529 { 3530 mss = maxmtu - min_protoh; 3531 if (!V_path_mtu_discovery && 3532 !in_localaddr(inp->inp_faddr)) 3533 mss = min(mss, V_tcp_mssdflt); 3534 } 3535 #endif 3536 /* 3537 * XXX - The above conditional (mss = maxmtu - min_protoh) 3538 * probably violates the TCP spec. 3539 * The problem is that, since we don't know the 3540 * other end's MSS, we are supposed to use a conservative 3541 * default. But, if we do that, then MTU discovery will 3542 * never actually take place, because the conservative 3543 * default is much less than the MTUs typically seen 3544 * on the Internet today. For the moment, we'll sweep 3545 * this under the carpet. 3546 * 3547 * The conservative default might not actually be a problem 3548 * if the only case this occurs is when sending an initial 3549 * SYN with options and data to a host we've never talked 3550 * to before. Then, they will reply with an MSS value which 3551 * will get recorded and the new parameters should get 3552 * recomputed. For Further Study. 3553 */ 3554 } 3555 mss = min(mss, offer); 3556 3557 /* 3558 * Sanity check: make sure that maxopd will be large 3559 * enough to allow some data on segments even if the 3560 * all the option space is used (40bytes). Otherwise 3561 * funny things may happen in tcp_output. 3562 */ 3563 mss = max(mss, 64); 3564 3565 /* 3566 * maxopd stores the maximum length of data AND options 3567 * in a segment; maxseg is the amount of data in a normal 3568 * segment. We need to store this value (maxopd) apart 3569 * from maxseg, because now every segment carries options 3570 * and thus we normally have somewhat less data in segments. 3571 */ 3572 tp->t_maxopd = mss; 3573 3574 /* 3575 * origoffer==-1 indicates that no segments were received yet. 3576 * In this case we just guess. 3577 */ 3578 if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP && 3579 (origoffer == -1 || 3580 (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP)) 3581 mss -= TCPOLEN_TSTAMP_APPA; 3582 3583 tp->t_maxseg = mss; 3584 } 3585 3586 void 3587 tcp_mss(struct tcpcb *tp, int offer) 3588 { 3589 int mss; 3590 u_long bufsize; 3591 struct inpcb *inp; 3592 struct socket *so; 3593 struct hc_metrics_lite metrics; 3594 struct tcp_ifcap cap; 3595 3596 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3597 3598 bzero(&cap, sizeof(cap)); 3599 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3600 3601 mss = tp->t_maxseg; 3602 inp = tp->t_inpcb; 3603 3604 /* 3605 * If there's a pipesize, change the socket buffer to that size, 3606 * don't change if sb_hiwat is different than default (then it 3607 * has been changed on purpose with setsockopt). 3608 * Make the socket buffers an integral number of mss units; 3609 * if the mss is larger than the socket buffer, decrease the mss. 3610 */ 3611 so = inp->inp_socket; 3612 SOCKBUF_LOCK(&so->so_snd); 3613 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3614 bufsize = metrics.rmx_sendpipe; 3615 else 3616 bufsize = so->so_snd.sb_hiwat; 3617 if (bufsize < mss) 3618 mss = bufsize; 3619 else { 3620 bufsize = roundup(bufsize, mss); 3621 if (bufsize > sb_max) 3622 bufsize = sb_max; 3623 if (bufsize > so->so_snd.sb_hiwat) 3624 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3625 } 3626 SOCKBUF_UNLOCK(&so->so_snd); 3627 tp->t_maxseg = mss; 3628 3629 SOCKBUF_LOCK(&so->so_rcv); 3630 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3631 bufsize = metrics.rmx_recvpipe; 3632 else 3633 bufsize = so->so_rcv.sb_hiwat; 3634 if (bufsize > mss) { 3635 bufsize = roundup(bufsize, mss); 3636 if (bufsize > sb_max) 3637 bufsize = sb_max; 3638 if (bufsize > so->so_rcv.sb_hiwat) 3639 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3640 } 3641 SOCKBUF_UNLOCK(&so->so_rcv); 3642 3643 /* Check the interface for TSO capabilities. */ 3644 if (cap.ifcap & CSUM_TSO) { 3645 tp->t_flags |= TF_TSO; 3646 tp->t_tsomax = cap.tsomax; 3647 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3648 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3649 } 3650 } 3651 3652 /* 3653 * Determine the MSS option to send on an outgoing SYN. 3654 */ 3655 int 3656 tcp_mssopt(struct in_conninfo *inc) 3657 { 3658 int mss = 0; 3659 u_long maxmtu = 0; 3660 u_long thcmtu = 0; 3661 size_t min_protoh; 3662 3663 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3664 3665 #ifdef INET6 3666 if (inc->inc_flags & INC_ISIPV6) { 3667 mss = V_tcp_v6mssdflt; 3668 maxmtu = tcp_maxmtu6(inc, NULL); 3669 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3670 } 3671 #endif 3672 #if defined(INET) && defined(INET6) 3673 else 3674 #endif 3675 #ifdef INET 3676 { 3677 mss = V_tcp_mssdflt; 3678 maxmtu = tcp_maxmtu(inc, NULL); 3679 min_protoh = sizeof(struct tcpiphdr); 3680 } 3681 #endif 3682 #if defined(INET6) || defined(INET) 3683 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3684 #endif 3685 3686 if (maxmtu && thcmtu) 3687 mss = min(maxmtu, thcmtu) - min_protoh; 3688 else if (maxmtu || thcmtu) 3689 mss = max(maxmtu, thcmtu) - min_protoh; 3690 3691 return (mss); 3692 } 3693 3694 3695 /* 3696 * On a partial ack arrives, force the retransmission of the 3697 * next unacknowledged segment. Do not clear tp->t_dupacks. 3698 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3699 * be started again. 3700 */ 3701 static void 3702 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3703 { 3704 tcp_seq onxt = tp->snd_nxt; 3705 u_long ocwnd = tp->snd_cwnd; 3706 3707 INP_WLOCK_ASSERT(tp->t_inpcb); 3708 3709 tcp_timer_activate(tp, TT_REXMT, 0); 3710 tp->t_rtttime = 0; 3711 tp->snd_nxt = th->th_ack; 3712 /* 3713 * Set snd_cwnd to one segment beyond acknowledged offset. 3714 * (tp->snd_una has not yet been updated when this function is called.) 3715 */ 3716 tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th); 3717 tp->t_flags |= TF_ACKNOW; 3718 (void) tcp_output(tp); 3719 tp->snd_cwnd = ocwnd; 3720 if (SEQ_GT(onxt, tp->snd_nxt)) 3721 tp->snd_nxt = onxt; 3722 /* 3723 * Partial window deflation. Relies on fact that tp->snd_una 3724 * not updated yet. 3725 */ 3726 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3727 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3728 else 3729 tp->snd_cwnd = 0; 3730 tp->snd_cwnd += tp->t_maxseg; 3731 } 3732