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_inet.h" 54 #include "opt_inet6.h" 55 #include "opt_ipsec.h" 56 #include "opt_tcpdebug.h" 57 58 #include <sys/param.h> 59 #include <sys/kernel.h> 60 #ifdef TCP_HHOOK 61 #include <sys/hhook.h> 62 #endif 63 #include <sys/malloc.h> 64 #include <sys/mbuf.h> 65 #include <sys/proc.h> /* for proc0 declaration */ 66 #include <sys/protosw.h> 67 #include <sys/sdt.h> 68 #include <sys/signalvar.h> 69 #include <sys/socket.h> 70 #include <sys/socketvar.h> 71 #include <sys/sysctl.h> 72 #include <sys/syslog.h> 73 #include <sys/systm.h> 74 75 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 76 77 #include <vm/uma.h> 78 79 #include <net/if.h> 80 #include <net/if_var.h> 81 #include <net/route.h> 82 #include <net/vnet.h> 83 84 #define TCPSTATES /* for logging */ 85 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/ip.h> 91 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 92 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 93 #include <netinet/ip_var.h> 94 #include <netinet/ip_options.h> 95 #include <netinet/ip6.h> 96 #include <netinet/icmp6.h> 97 #include <netinet6/in6_pcb.h> 98 #include <netinet6/in6_var.h> 99 #include <netinet6/ip6_var.h> 100 #include <netinet6/nd6.h> 101 #ifdef TCP_RFC7413 102 #include <netinet/tcp_fastopen.h> 103 #endif 104 #include <netinet/tcp.h> 105 #include <netinet/tcp_fsm.h> 106 #include <netinet/tcp_seq.h> 107 #include <netinet/tcp_timer.h> 108 #include <netinet/tcp_var.h> 109 #include <netinet6/tcp6_var.h> 110 #include <netinet/tcpip.h> 111 #include <netinet/cc/cc.h> 112 #ifdef TCPPCAP 113 #include <netinet/tcp_pcap.h> 114 #endif 115 #include <netinet/tcp_syncache.h> 116 #ifdef TCPDEBUG 117 #include <netinet/tcp_debug.h> 118 #endif /* TCPDEBUG */ 119 #ifdef TCP_OFFLOAD 120 #include <netinet/tcp_offload.h> 121 #endif 122 123 #ifdef IPSEC 124 #include <netipsec/ipsec.h> 125 #include <netipsec/ipsec6.h> 126 #endif /*IPSEC*/ 127 128 #include <machine/in_cksum.h> 129 130 #include <security/mac/mac_framework.h> 131 132 const int tcprexmtthresh = 3; 133 134 int tcp_log_in_vain = 0; 135 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 136 &tcp_log_in_vain, 0, 137 "Log all incoming TCP segments to closed ports"); 138 139 VNET_DEFINE(int, blackhole) = 0; 140 #define V_blackhole VNET(blackhole) 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 142 &VNET_NAME(blackhole), 0, 143 "Do not send RST on segments to closed ports"); 144 145 VNET_DEFINE(int, tcp_delack_enabled) = 1; 146 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 147 &VNET_NAME(tcp_delack_enabled), 0, 148 "Delay ACK to try and piggyback it onto a data packet"); 149 150 VNET_DEFINE(int, drop_synfin) = 0; 151 #define V_drop_synfin VNET(drop_synfin) 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 153 &VNET_NAME(drop_synfin), 0, 154 "Drop TCP packets with SYN+FIN set"); 155 156 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 158 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 159 "Use calculated pipe/in-flight bytes per RFC 6675"); 160 161 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 162 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 164 &VNET_NAME(tcp_do_rfc3042), 0, 165 "Enable RFC 3042 (Limited Transmit)"); 166 167 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 168 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 169 &VNET_NAME(tcp_do_rfc3390), 0, 170 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 171 172 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 174 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 175 "Slow-start flight size (initial congestion window) in number of segments"); 176 177 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 179 &VNET_NAME(tcp_do_rfc3465), 0, 180 "Enable RFC 3465 (Appropriate Byte Counting)"); 181 182 VNET_DEFINE(int, tcp_abc_l_var) = 2; 183 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 184 &VNET_NAME(tcp_abc_l_var), 2, 185 "Cap the max cwnd increment during slow-start to this number of segments"); 186 187 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 188 189 VNET_DEFINE(int, tcp_do_ecn) = 2; 190 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 191 &VNET_NAME(tcp_do_ecn), 0, 192 "TCP ECN support"); 193 194 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 195 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 196 &VNET_NAME(tcp_ecn_maxretries), 0, 197 "Max retries before giving up on ECN"); 198 199 VNET_DEFINE(int, tcp_insecure_syn) = 0; 200 #define V_tcp_insecure_syn VNET(tcp_insecure_syn) 201 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 202 &VNET_NAME(tcp_insecure_syn), 0, 203 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 204 205 VNET_DEFINE(int, tcp_insecure_rst) = 0; 206 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 207 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 208 &VNET_NAME(tcp_insecure_rst), 0, 209 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 210 211 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 212 #define V_tcp_recvspace VNET(tcp_recvspace) 213 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 214 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 215 216 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 217 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 218 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 219 &VNET_NAME(tcp_do_autorcvbuf), 0, 220 "Enable automatic receive buffer sizing"); 221 222 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 223 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 224 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 225 &VNET_NAME(tcp_autorcvbuf_inc), 0, 226 "Incrementor step size of automatic receive buffer"); 227 228 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 229 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 230 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 231 &VNET_NAME(tcp_autorcvbuf_max), 0, 232 "Max size of automatic receive buffer"); 233 234 VNET_DEFINE(struct inpcbhead, tcb); 235 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 236 VNET_DEFINE(struct inpcbinfo, tcbinfo); 237 238 /* 239 * TCP statistics are stored in an array of counter(9)s, which size matches 240 * size of struct tcpstat. TCP running connection count is a regular array. 241 */ 242 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 243 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 244 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 245 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 246 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 247 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 248 "TCP connection counts by TCP state"); 249 250 static void 251 tcp_vnet_init(const void *unused) 252 { 253 254 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 255 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 256 } 257 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 258 tcp_vnet_init, NULL); 259 260 #ifdef VIMAGE 261 static void 262 tcp_vnet_uninit(const void *unused) 263 { 264 265 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 266 VNET_PCPUSTAT_FREE(tcpstat); 267 } 268 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 269 tcp_vnet_uninit, NULL); 270 #endif /* VIMAGE */ 271 272 /* 273 * Kernel module interface for updating tcpstat. The argument is an index 274 * into tcpstat treated as an array. 275 */ 276 void 277 kmod_tcpstat_inc(int statnum) 278 { 279 280 counter_u64_add(VNET(tcpstat)[statnum], 1); 281 } 282 283 #ifdef TCP_HHOOK 284 /* 285 * Wrapper for the TCP established input helper hook. 286 */ 287 void 288 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 289 { 290 struct tcp_hhook_data hhook_data; 291 292 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 293 hhook_data.tp = tp; 294 hhook_data.th = th; 295 hhook_data.to = to; 296 297 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 298 tp->osd); 299 } 300 } 301 #endif 302 303 /* 304 * CC wrapper hook functions 305 */ 306 void 307 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 308 uint16_t type) 309 { 310 INP_WLOCK_ASSERT(tp->t_inpcb); 311 312 tp->ccv->nsegs = nsegs; 313 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 314 if (tp->snd_cwnd <= tp->snd_wnd) 315 tp->ccv->flags |= CCF_CWND_LIMITED; 316 else 317 tp->ccv->flags &= ~CCF_CWND_LIMITED; 318 319 if (type == CC_ACK) { 320 if (tp->snd_cwnd > tp->snd_ssthresh) { 321 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 322 nsegs * V_tcp_abc_l_var * tcp_maxseg(tp)); 323 if (tp->t_bytes_acked >= tp->snd_cwnd) { 324 tp->t_bytes_acked -= tp->snd_cwnd; 325 tp->ccv->flags |= CCF_ABC_SENTAWND; 326 } 327 } else { 328 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 329 tp->t_bytes_acked = 0; 330 } 331 } 332 333 if (CC_ALGO(tp)->ack_received != NULL) { 334 /* XXXLAS: Find a way to live without this */ 335 tp->ccv->curack = th->th_ack; 336 CC_ALGO(tp)->ack_received(tp->ccv, type); 337 } 338 } 339 340 void 341 cc_conn_init(struct tcpcb *tp) 342 { 343 struct hc_metrics_lite metrics; 344 struct inpcb *inp = tp->t_inpcb; 345 u_int maxseg; 346 int rtt; 347 348 INP_WLOCK_ASSERT(tp->t_inpcb); 349 350 tcp_hc_get(&inp->inp_inc, &metrics); 351 maxseg = tcp_maxseg(tp); 352 353 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 354 tp->t_srtt = rtt; 355 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 356 TCPSTAT_INC(tcps_usedrtt); 357 if (metrics.rmx_rttvar) { 358 tp->t_rttvar = metrics.rmx_rttvar; 359 TCPSTAT_INC(tcps_usedrttvar); 360 } else { 361 /* default variation is +- 1 rtt */ 362 tp->t_rttvar = 363 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 364 } 365 TCPT_RANGESET(tp->t_rxtcur, 366 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 367 tp->t_rttmin, TCPTV_REXMTMAX); 368 } 369 if (metrics.rmx_ssthresh) { 370 /* 371 * There's some sort of gateway or interface 372 * buffer limit on the path. Use this to set 373 * the slow start threshold, but set the 374 * threshold to no less than 2*mss. 375 */ 376 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 377 TCPSTAT_INC(tcps_usedssthresh); 378 } 379 380 /* 381 * Set the initial slow-start flight size. 382 * 383 * RFC5681 Section 3.1 specifies the default conservative values. 384 * RFC3390 specifies slightly more aggressive values. 385 * RFC6928 increases it to ten segments. 386 * Support for user specified value for initial flight size. 387 * 388 * If a SYN or SYN/ACK was lost and retransmitted, we have to 389 * reduce the initial CWND to one segment as congestion is likely 390 * requiring us to be cautious. 391 */ 392 if (tp->snd_cwnd == 1) 393 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 394 else if (V_tcp_initcwnd_segments) 395 tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg, 396 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 397 else if (V_tcp_do_rfc3390) 398 tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380)); 399 else { 400 /* Per RFC5681 Section 3.1 */ 401 if (maxseg > 2190) 402 tp->snd_cwnd = 2 * maxseg; 403 else if (maxseg > 1095) 404 tp->snd_cwnd = 3 * maxseg; 405 else 406 tp->snd_cwnd = 4 * maxseg; 407 } 408 409 if (CC_ALGO(tp)->conn_init != NULL) 410 CC_ALGO(tp)->conn_init(tp->ccv); 411 } 412 413 void inline 414 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 415 { 416 u_int maxseg; 417 418 INP_WLOCK_ASSERT(tp->t_inpcb); 419 420 switch(type) { 421 case CC_NDUPACK: 422 if (!IN_FASTRECOVERY(tp->t_flags)) { 423 tp->snd_recover = tp->snd_max; 424 if (tp->t_flags & TF_ECN_PERMIT) 425 tp->t_flags |= TF_ECN_SND_CWR; 426 } 427 break; 428 case CC_ECN: 429 if (!IN_CONGRECOVERY(tp->t_flags)) { 430 TCPSTAT_INC(tcps_ecn_rcwnd); 431 tp->snd_recover = tp->snd_max; 432 if (tp->t_flags & TF_ECN_PERMIT) 433 tp->t_flags |= TF_ECN_SND_CWR; 434 } 435 break; 436 case CC_RTO: 437 maxseg = tcp_maxseg(tp); 438 tp->t_dupacks = 0; 439 tp->t_bytes_acked = 0; 440 EXIT_RECOVERY(tp->t_flags); 441 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 442 maxseg) * maxseg; 443 tp->snd_cwnd = maxseg; 444 break; 445 case CC_RTO_ERR: 446 TCPSTAT_INC(tcps_sndrexmitbad); 447 /* RTO was unnecessary, so reset everything. */ 448 tp->snd_cwnd = tp->snd_cwnd_prev; 449 tp->snd_ssthresh = tp->snd_ssthresh_prev; 450 tp->snd_recover = tp->snd_recover_prev; 451 if (tp->t_flags & TF_WASFRECOVERY) 452 ENTER_FASTRECOVERY(tp->t_flags); 453 if (tp->t_flags & TF_WASCRECOVERY) 454 ENTER_CONGRECOVERY(tp->t_flags); 455 tp->snd_nxt = tp->snd_max; 456 tp->t_flags &= ~TF_PREVVALID; 457 tp->t_badrxtwin = 0; 458 break; 459 } 460 461 if (CC_ALGO(tp)->cong_signal != NULL) { 462 if (th != NULL) 463 tp->ccv->curack = th->th_ack; 464 CC_ALGO(tp)->cong_signal(tp->ccv, type); 465 } 466 } 467 468 void inline 469 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 470 { 471 INP_WLOCK_ASSERT(tp->t_inpcb); 472 473 /* XXXLAS: KASSERT that we're in recovery? */ 474 475 if (CC_ALGO(tp)->post_recovery != NULL) { 476 tp->ccv->curack = th->th_ack; 477 CC_ALGO(tp)->post_recovery(tp->ccv); 478 } 479 /* XXXLAS: EXIT_RECOVERY ? */ 480 tp->t_bytes_acked = 0; 481 } 482 483 #ifdef TCP_SIGNATURE 484 static inline int 485 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 486 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 487 { 488 int ret; 489 490 tcp_fields_to_net(th); 491 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 492 tcp_fields_to_host(th); 493 return (ret); 494 } 495 #endif 496 497 /* 498 * Indicate whether this ack should be delayed. We can delay the ack if 499 * following conditions are met: 500 * - There is no delayed ack timer in progress. 501 * - Our last ack wasn't a 0-sized window. We never want to delay 502 * the ack that opens up a 0-sized window. 503 * - LRO wasn't used for this segment. We make sure by checking that the 504 * segment size is not larger than the MSS. 505 */ 506 #define DELAY_ACK(tp, tlen) \ 507 ((!tcp_timer_active(tp, TT_DELACK) && \ 508 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 509 (tlen <= tp->t_maxseg) && \ 510 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 511 512 static void inline 513 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 514 { 515 INP_WLOCK_ASSERT(tp->t_inpcb); 516 517 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 518 switch (iptos & IPTOS_ECN_MASK) { 519 case IPTOS_ECN_CE: 520 tp->ccv->flags |= CCF_IPHDR_CE; 521 break; 522 case IPTOS_ECN_ECT0: 523 tp->ccv->flags &= ~CCF_IPHDR_CE; 524 break; 525 case IPTOS_ECN_ECT1: 526 tp->ccv->flags &= ~CCF_IPHDR_CE; 527 break; 528 } 529 530 if (th->th_flags & TH_CWR) 531 tp->ccv->flags |= CCF_TCPHDR_CWR; 532 else 533 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 534 535 if (tp->t_flags & TF_DELACK) 536 tp->ccv->flags |= CCF_DELACK; 537 else 538 tp->ccv->flags &= ~CCF_DELACK; 539 540 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 541 542 if (tp->ccv->flags & CCF_ACKNOW) 543 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 544 } 545 } 546 547 /* 548 * TCP input handling is split into multiple parts: 549 * tcp6_input is a thin wrapper around tcp_input for the extended 550 * ip6_protox[] call format in ip6_input 551 * tcp_input handles primary segment validation, inpcb lookup and 552 * SYN processing on listen sockets 553 * tcp_do_segment processes the ACK and text of the segment for 554 * establishing, established and closing connections 555 */ 556 #ifdef INET6 557 int 558 tcp6_input(struct mbuf **mp, int *offp, int proto) 559 { 560 struct mbuf *m = *mp; 561 struct in6_ifaddr *ia6; 562 struct ip6_hdr *ip6; 563 564 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 565 566 /* 567 * draft-itojun-ipv6-tcp-to-anycast 568 * better place to put this in? 569 */ 570 ip6 = mtod(m, struct ip6_hdr *); 571 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 572 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 573 struct ip6_hdr *ip6; 574 575 ifa_free(&ia6->ia_ifa); 576 ip6 = mtod(m, struct ip6_hdr *); 577 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 578 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 579 return (IPPROTO_DONE); 580 } 581 if (ia6) 582 ifa_free(&ia6->ia_ifa); 583 584 return (tcp_input(mp, offp, proto)); 585 } 586 #endif /* INET6 */ 587 588 int 589 tcp_input(struct mbuf **mp, int *offp, int proto) 590 { 591 struct mbuf *m = *mp; 592 struct tcphdr *th = NULL; 593 struct ip *ip = NULL; 594 struct inpcb *inp = NULL; 595 struct tcpcb *tp = NULL; 596 struct socket *so = NULL; 597 u_char *optp = NULL; 598 int off0; 599 int optlen = 0; 600 #ifdef INET 601 int len; 602 #endif 603 int tlen = 0, off; 604 int drop_hdrlen; 605 int thflags; 606 int rstreason = 0; /* For badport_bandlim accounting purposes */ 607 #ifdef TCP_SIGNATURE 608 uint8_t sig_checked = 0; 609 #endif 610 uint8_t iptos; 611 struct m_tag *fwd_tag = NULL; 612 #ifdef INET6 613 struct ip6_hdr *ip6 = NULL; 614 int isipv6; 615 #else 616 const void *ip6 = NULL; 617 #endif /* INET6 */ 618 struct tcpopt to; /* options in this segment */ 619 char *s = NULL; /* address and port logging */ 620 int ti_locked; 621 #ifdef TCPDEBUG 622 /* 623 * The size of tcp_saveipgen must be the size of the max ip header, 624 * now IPv6. 625 */ 626 u_char tcp_saveipgen[IP6_HDR_LEN]; 627 struct tcphdr tcp_savetcp; 628 short ostate = 0; 629 #endif 630 631 #ifdef INET6 632 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 633 #endif 634 635 off0 = *offp; 636 m = *mp; 637 *mp = NULL; 638 to.to_flags = 0; 639 TCPSTAT_INC(tcps_rcvtotal); 640 641 #ifdef INET6 642 if (isipv6) { 643 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 644 645 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 646 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 647 if (m == NULL) { 648 TCPSTAT_INC(tcps_rcvshort); 649 return (IPPROTO_DONE); 650 } 651 } 652 653 ip6 = mtod(m, struct ip6_hdr *); 654 th = (struct tcphdr *)((caddr_t)ip6 + off0); 655 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 656 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 657 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 658 th->th_sum = m->m_pkthdr.csum_data; 659 else 660 th->th_sum = in6_cksum_pseudo(ip6, tlen, 661 IPPROTO_TCP, m->m_pkthdr.csum_data); 662 th->th_sum ^= 0xffff; 663 } else 664 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 665 if (th->th_sum) { 666 TCPSTAT_INC(tcps_rcvbadsum); 667 goto drop; 668 } 669 670 /* 671 * Be proactive about unspecified IPv6 address in source. 672 * As we use all-zero to indicate unbounded/unconnected pcb, 673 * unspecified IPv6 address can be used to confuse us. 674 * 675 * Note that packets with unspecified IPv6 destination is 676 * already dropped in ip6_input. 677 */ 678 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 679 /* XXX stat */ 680 goto drop; 681 } 682 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 683 } 684 #endif 685 #if defined(INET) && defined(INET6) 686 else 687 #endif 688 #ifdef INET 689 { 690 /* 691 * Get IP and TCP header together in first mbuf. 692 * Note: IP leaves IP header in first mbuf. 693 */ 694 if (off0 > sizeof (struct ip)) { 695 ip_stripoptions(m); 696 off0 = sizeof(struct ip); 697 } 698 if (m->m_len < sizeof (struct tcpiphdr)) { 699 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 700 == NULL) { 701 TCPSTAT_INC(tcps_rcvshort); 702 return (IPPROTO_DONE); 703 } 704 } 705 ip = mtod(m, struct ip *); 706 th = (struct tcphdr *)((caddr_t)ip + off0); 707 tlen = ntohs(ip->ip_len) - off0; 708 709 iptos = ip->ip_tos; 710 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 711 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 712 th->th_sum = m->m_pkthdr.csum_data; 713 else 714 th->th_sum = in_pseudo(ip->ip_src.s_addr, 715 ip->ip_dst.s_addr, 716 htonl(m->m_pkthdr.csum_data + tlen + 717 IPPROTO_TCP)); 718 th->th_sum ^= 0xffff; 719 } else { 720 struct ipovly *ipov = (struct ipovly *)ip; 721 722 /* 723 * Checksum extended TCP header and data. 724 */ 725 len = off0 + tlen; 726 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 727 ipov->ih_len = htons(tlen); 728 th->th_sum = in_cksum(m, len); 729 /* Reset length for SDT probes. */ 730 ip->ip_len = htons(len); 731 /* Reset TOS bits */ 732 ip->ip_tos = iptos; 733 /* Re-initialization for later version check */ 734 ip->ip_v = IPVERSION; 735 } 736 737 if (th->th_sum) { 738 TCPSTAT_INC(tcps_rcvbadsum); 739 goto drop; 740 } 741 } 742 #endif /* INET */ 743 744 /* 745 * Check that TCP offset makes sense, 746 * pull out TCP options and adjust length. XXX 747 */ 748 off = th->th_off << 2; 749 if (off < sizeof (struct tcphdr) || off > tlen) { 750 TCPSTAT_INC(tcps_rcvbadoff); 751 goto drop; 752 } 753 tlen -= off; /* tlen is used instead of ti->ti_len */ 754 if (off > sizeof (struct tcphdr)) { 755 #ifdef INET6 756 if (isipv6) { 757 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 758 ip6 = mtod(m, struct ip6_hdr *); 759 th = (struct tcphdr *)((caddr_t)ip6 + off0); 760 } 761 #endif 762 #if defined(INET) && defined(INET6) 763 else 764 #endif 765 #ifdef INET 766 { 767 if (m->m_len < sizeof(struct ip) + off) { 768 if ((m = m_pullup(m, sizeof (struct ip) + off)) 769 == NULL) { 770 TCPSTAT_INC(tcps_rcvshort); 771 return (IPPROTO_DONE); 772 } 773 ip = mtod(m, struct ip *); 774 th = (struct tcphdr *)((caddr_t)ip + off0); 775 } 776 } 777 #endif 778 optlen = off - sizeof (struct tcphdr); 779 optp = (u_char *)(th + 1); 780 } 781 thflags = th->th_flags; 782 783 /* 784 * Convert TCP protocol specific fields to host format. 785 */ 786 tcp_fields_to_host(th); 787 788 /* 789 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 790 */ 791 drop_hdrlen = off0 + off; 792 793 /* 794 * Locate pcb for segment; if we're likely to add or remove a 795 * connection then first acquire pcbinfo lock. There are three cases 796 * where we might discover later we need a write lock despite the 797 * flags: ACKs moving a connection out of the syncache, ACKs for a 798 * connection in TIMEWAIT and SYNs not targeting a listening socket. 799 */ 800 if ((thflags & (TH_FIN | TH_RST)) != 0) { 801 INP_INFO_RLOCK(&V_tcbinfo); 802 ti_locked = TI_RLOCKED; 803 } else 804 ti_locked = TI_UNLOCKED; 805 806 /* 807 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 808 */ 809 if ( 810 #ifdef INET6 811 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 812 #ifdef INET 813 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 814 #endif 815 #endif 816 #if defined(INET) && !defined(INET6) 817 (m->m_flags & M_IP_NEXTHOP) 818 #endif 819 ) 820 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 821 822 findpcb: 823 #ifdef INVARIANTS 824 if (ti_locked == TI_RLOCKED) { 825 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 826 } else { 827 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 828 } 829 #endif 830 #ifdef INET6 831 if (isipv6 && fwd_tag != NULL) { 832 struct sockaddr_in6 *next_hop6; 833 834 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 835 /* 836 * Transparently forwarded. Pretend to be the destination. 837 * Already got one like this? 838 */ 839 inp = in6_pcblookup_mbuf(&V_tcbinfo, 840 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 841 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 842 if (!inp) { 843 /* 844 * It's new. Try to find the ambushing socket. 845 * Because we've rewritten the destination address, 846 * any hardware-generated hash is ignored. 847 */ 848 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 849 th->th_sport, &next_hop6->sin6_addr, 850 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 851 th->th_dport, INPLOOKUP_WILDCARD | 852 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 853 } 854 } else if (isipv6) { 855 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 856 th->th_sport, &ip6->ip6_dst, th->th_dport, 857 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 858 m->m_pkthdr.rcvif, m); 859 } 860 #endif /* INET6 */ 861 #if defined(INET6) && defined(INET) 862 else 863 #endif 864 #ifdef INET 865 if (fwd_tag != NULL) { 866 struct sockaddr_in *next_hop; 867 868 next_hop = (struct sockaddr_in *)(fwd_tag+1); 869 /* 870 * Transparently forwarded. Pretend to be the destination. 871 * already got one like this? 872 */ 873 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 874 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 875 m->m_pkthdr.rcvif, m); 876 if (!inp) { 877 /* 878 * It's new. Try to find the ambushing socket. 879 * Because we've rewritten the destination address, 880 * any hardware-generated hash is ignored. 881 */ 882 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 883 th->th_sport, next_hop->sin_addr, 884 next_hop->sin_port ? ntohs(next_hop->sin_port) : 885 th->th_dport, INPLOOKUP_WILDCARD | 886 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 887 } 888 } else 889 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 890 th->th_sport, ip->ip_dst, th->th_dport, 891 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 892 m->m_pkthdr.rcvif, m); 893 #endif /* INET */ 894 895 /* 896 * If the INPCB does not exist then all data in the incoming 897 * segment is discarded and an appropriate RST is sent back. 898 * XXX MRT Send RST using which routing table? 899 */ 900 if (inp == NULL) { 901 /* 902 * Log communication attempts to ports that are not 903 * in use. 904 */ 905 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 906 tcp_log_in_vain == 2) { 907 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 908 log(LOG_INFO, "%s; %s: Connection attempt " 909 "to closed port\n", s, __func__); 910 } 911 /* 912 * When blackholing do not respond with a RST but 913 * completely ignore the segment and drop it. 914 */ 915 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 916 V_blackhole == 2) 917 goto dropunlock; 918 919 rstreason = BANDLIM_RST_CLOSEDPORT; 920 goto dropwithreset; 921 } 922 INP_WLOCK_ASSERT(inp); 923 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 924 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 925 ((inp->inp_socket == NULL) || 926 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 927 inp->inp_flowid = m->m_pkthdr.flowid; 928 inp->inp_flowtype = M_HASHTYPE_GET(m); 929 } 930 #ifdef IPSEC 931 #ifdef INET6 932 if (isipv6 && ipsec6_in_reject(m, inp)) { 933 goto dropunlock; 934 } else 935 #endif /* INET6 */ 936 if (ipsec4_in_reject(m, inp) != 0) { 937 goto dropunlock; 938 } 939 #endif /* IPSEC */ 940 941 /* 942 * Check the minimum TTL for socket. 943 */ 944 if (inp->inp_ip_minttl != 0) { 945 #ifdef INET6 946 if (isipv6) { 947 if (inp->inp_ip_minttl > ip6->ip6_hlim) 948 goto dropunlock; 949 } else 950 #endif 951 if (inp->inp_ip_minttl > ip->ip_ttl) 952 goto dropunlock; 953 } 954 955 /* 956 * A previous connection in TIMEWAIT state is supposed to catch stray 957 * or duplicate segments arriving late. If this segment was a 958 * legitimate new connection attempt, the old INPCB gets removed and 959 * we can try again to find a listening socket. 960 * 961 * At this point, due to earlier optimism, we may hold only an inpcb 962 * lock, and not the inpcbinfo write lock. If so, we need to try to 963 * acquire it, or if that fails, acquire a reference on the inpcb, 964 * drop all locks, acquire a global write lock, and then re-acquire 965 * the inpcb lock. We may at that point discover that another thread 966 * has tried to free the inpcb, in which case we need to loop back 967 * and try to find a new inpcb to deliver to. 968 * 969 * XXXRW: It may be time to rethink timewait locking. 970 */ 971 relocked: 972 if (inp->inp_flags & INP_TIMEWAIT) { 973 if (ti_locked == TI_UNLOCKED) { 974 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 975 in_pcbref(inp); 976 INP_WUNLOCK(inp); 977 INP_INFO_RLOCK(&V_tcbinfo); 978 ti_locked = TI_RLOCKED; 979 INP_WLOCK(inp); 980 if (in_pcbrele_wlocked(inp)) { 981 inp = NULL; 982 goto findpcb; 983 } 984 } else 985 ti_locked = TI_RLOCKED; 986 } 987 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 988 989 if (thflags & TH_SYN) 990 tcp_dooptions(&to, optp, optlen, TO_SYN); 991 /* 992 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 993 */ 994 if (tcp_twcheck(inp, &to, th, m, tlen)) 995 goto findpcb; 996 INP_INFO_RUNLOCK(&V_tcbinfo); 997 return (IPPROTO_DONE); 998 } 999 /* 1000 * The TCPCB may no longer exist if the connection is winding 1001 * down or it is in the CLOSED state. Either way we drop the 1002 * segment and send an appropriate response. 1003 */ 1004 tp = intotcpcb(inp); 1005 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1006 rstreason = BANDLIM_RST_CLOSEDPORT; 1007 goto dropwithreset; 1008 } 1009 1010 #ifdef TCP_OFFLOAD 1011 if (tp->t_flags & TF_TOE) { 1012 tcp_offload_input(tp, m); 1013 m = NULL; /* consumed by the TOE driver */ 1014 goto dropunlock; 1015 } 1016 #endif 1017 1018 /* 1019 * We've identified a valid inpcb, but it could be that we need an 1020 * inpcbinfo write lock but don't hold it. In this case, attempt to 1021 * acquire using the same strategy as the TIMEWAIT case above. If we 1022 * relock, we have to jump back to 'relocked' as the connection might 1023 * now be in TIMEWAIT. 1024 */ 1025 #ifdef INVARIANTS 1026 if ((thflags & (TH_FIN | TH_RST)) != 0) 1027 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1028 #endif 1029 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) || 1030 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) && 1031 !IS_FASTOPEN(tp->t_flags)))) { 1032 if (ti_locked == TI_UNLOCKED) { 1033 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 1034 in_pcbref(inp); 1035 INP_WUNLOCK(inp); 1036 INP_INFO_RLOCK(&V_tcbinfo); 1037 ti_locked = TI_RLOCKED; 1038 INP_WLOCK(inp); 1039 if (in_pcbrele_wlocked(inp)) { 1040 inp = NULL; 1041 goto findpcb; 1042 } 1043 goto relocked; 1044 } else 1045 ti_locked = TI_RLOCKED; 1046 } 1047 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1048 } 1049 1050 #ifdef MAC 1051 INP_WLOCK_ASSERT(inp); 1052 if (mac_inpcb_check_deliver(inp, m)) 1053 goto dropunlock; 1054 #endif 1055 so = inp->inp_socket; 1056 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1057 #ifdef TCPDEBUG 1058 if (so->so_options & SO_DEBUG) { 1059 ostate = tp->t_state; 1060 #ifdef INET6 1061 if (isipv6) { 1062 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1063 } else 1064 #endif 1065 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1066 tcp_savetcp = *th; 1067 } 1068 #endif /* TCPDEBUG */ 1069 /* 1070 * When the socket is accepting connections (the INPCB is in LISTEN 1071 * state) we look into the SYN cache if this is a new connection 1072 * attempt or the completion of a previous one. 1073 */ 1074 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1075 ("%s: so accepting but tp %p not listening", __func__, tp)); 1076 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1077 struct in_conninfo inc; 1078 1079 bzero(&inc, sizeof(inc)); 1080 #ifdef INET6 1081 if (isipv6) { 1082 inc.inc_flags |= INC_ISIPV6; 1083 inc.inc6_faddr = ip6->ip6_src; 1084 inc.inc6_laddr = ip6->ip6_dst; 1085 } else 1086 #endif 1087 { 1088 inc.inc_faddr = ip->ip_src; 1089 inc.inc_laddr = ip->ip_dst; 1090 } 1091 inc.inc_fport = th->th_sport; 1092 inc.inc_lport = th->th_dport; 1093 inc.inc_fibnum = so->so_fibnum; 1094 1095 /* 1096 * Check for an existing connection attempt in syncache if 1097 * the flag is only ACK. A successful lookup creates a new 1098 * socket appended to the listen queue in SYN_RECEIVED state. 1099 */ 1100 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1101 1102 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1103 /* 1104 * Parse the TCP options here because 1105 * syncookies need access to the reflected 1106 * timestamp. 1107 */ 1108 tcp_dooptions(&to, optp, optlen, 0); 1109 /* 1110 * NB: syncache_expand() doesn't unlock 1111 * inp and tcpinfo locks. 1112 */ 1113 if (!syncache_expand(&inc, &to, th, &so, m)) { 1114 /* 1115 * No syncache entry or ACK was not 1116 * for our SYN/ACK. Send a RST. 1117 * NB: syncache did its own logging 1118 * of the failure cause. 1119 */ 1120 rstreason = BANDLIM_RST_OPENPORT; 1121 goto dropwithreset; 1122 } 1123 #ifdef TCP_RFC7413 1124 tfo_socket_result: 1125 #endif 1126 if (so == NULL) { 1127 /* 1128 * We completed the 3-way handshake 1129 * but could not allocate a socket 1130 * either due to memory shortage, 1131 * listen queue length limits or 1132 * global socket limits. Send RST 1133 * or wait and have the remote end 1134 * retransmit the ACK for another 1135 * try. 1136 */ 1137 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1138 log(LOG_DEBUG, "%s; %s: Listen socket: " 1139 "Socket allocation failed due to " 1140 "limits or memory shortage, %s\n", 1141 s, __func__, 1142 V_tcp_sc_rst_sock_fail ? 1143 "sending RST" : "try again"); 1144 if (V_tcp_sc_rst_sock_fail) { 1145 rstreason = BANDLIM_UNLIMITED; 1146 goto dropwithreset; 1147 } else 1148 goto dropunlock; 1149 } 1150 /* 1151 * Socket is created in state SYN_RECEIVED. 1152 * Unlock the listen socket, lock the newly 1153 * created socket and update the tp variable. 1154 */ 1155 INP_WUNLOCK(inp); /* listen socket */ 1156 inp = sotoinpcb(so); 1157 /* 1158 * New connection inpcb is already locked by 1159 * syncache_expand(). 1160 */ 1161 INP_WLOCK_ASSERT(inp); 1162 tp = intotcpcb(inp); 1163 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1164 ("%s: ", __func__)); 1165 #ifdef TCP_SIGNATURE 1166 if (sig_checked == 0) { 1167 tcp_dooptions(&to, optp, optlen, 1168 (thflags & TH_SYN) ? TO_SYN : 0); 1169 if (!tcp_signature_verify_input(m, off0, tlen, 1170 optlen, &to, th, tp->t_flags)) { 1171 1172 /* 1173 * In SYN_SENT state if it receives an 1174 * RST, it is allowed for further 1175 * processing. 1176 */ 1177 if ((thflags & TH_RST) == 0 || 1178 (tp->t_state == TCPS_SYN_SENT) == 0) 1179 goto dropunlock; 1180 } 1181 sig_checked = 1; 1182 } 1183 #endif 1184 1185 /* 1186 * Process the segment and the data it 1187 * contains. tcp_do_segment() consumes 1188 * the mbuf chain and unlocks the inpcb. 1189 */ 1190 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1191 iptos, ti_locked); 1192 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1193 return (IPPROTO_DONE); 1194 } 1195 /* 1196 * Segment flag validation for new connection attempts: 1197 * 1198 * Our (SYN|ACK) response was rejected. 1199 * Check with syncache and remove entry to prevent 1200 * retransmits. 1201 * 1202 * NB: syncache_chkrst does its own logging of failure 1203 * causes. 1204 */ 1205 if (thflags & TH_RST) { 1206 syncache_chkrst(&inc, th); 1207 goto dropunlock; 1208 } 1209 /* 1210 * We can't do anything without SYN. 1211 */ 1212 if ((thflags & TH_SYN) == 0) { 1213 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1214 log(LOG_DEBUG, "%s; %s: Listen socket: " 1215 "SYN is missing, segment ignored\n", 1216 s, __func__); 1217 TCPSTAT_INC(tcps_badsyn); 1218 goto dropunlock; 1219 } 1220 /* 1221 * (SYN|ACK) is bogus on a listen socket. 1222 */ 1223 if (thflags & TH_ACK) { 1224 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1225 log(LOG_DEBUG, "%s; %s: Listen socket: " 1226 "SYN|ACK invalid, segment rejected\n", 1227 s, __func__); 1228 syncache_badack(&inc); /* XXX: Not needed! */ 1229 TCPSTAT_INC(tcps_badsyn); 1230 rstreason = BANDLIM_RST_OPENPORT; 1231 goto dropwithreset; 1232 } 1233 /* 1234 * If the drop_synfin option is enabled, drop all 1235 * segments with both the SYN and FIN bits set. 1236 * This prevents e.g. nmap from identifying the 1237 * TCP/IP stack. 1238 * XXX: Poor reasoning. nmap has other methods 1239 * and is constantly refining its stack detection 1240 * strategies. 1241 * XXX: This is a violation of the TCP specification 1242 * and was used by RFC1644. 1243 */ 1244 if ((thflags & TH_FIN) && V_drop_synfin) { 1245 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1246 log(LOG_DEBUG, "%s; %s: Listen socket: " 1247 "SYN|FIN segment ignored (based on " 1248 "sysctl setting)\n", s, __func__); 1249 TCPSTAT_INC(tcps_badsyn); 1250 goto dropunlock; 1251 } 1252 /* 1253 * Segment's flags are (SYN) or (SYN|FIN). 1254 * 1255 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1256 * as they do not affect the state of the TCP FSM. 1257 * The data pointed to by TH_URG and th_urp is ignored. 1258 */ 1259 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1260 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1261 KASSERT(thflags & (TH_SYN), 1262 ("%s: Listen socket: TH_SYN not set", __func__)); 1263 #ifdef INET6 1264 /* 1265 * If deprecated address is forbidden, 1266 * we do not accept SYN to deprecated interface 1267 * address to prevent any new inbound connection from 1268 * getting established. 1269 * When we do not accept SYN, we send a TCP RST, 1270 * with deprecated source address (instead of dropping 1271 * it). We compromise it as it is much better for peer 1272 * to send a RST, and RST will be the final packet 1273 * for the exchange. 1274 * 1275 * If we do not forbid deprecated addresses, we accept 1276 * the SYN packet. RFC2462 does not suggest dropping 1277 * SYN in this case. 1278 * If we decipher RFC2462 5.5.4, it says like this: 1279 * 1. use of deprecated addr with existing 1280 * communication is okay - "SHOULD continue to be 1281 * used" 1282 * 2. use of it with new communication: 1283 * (2a) "SHOULD NOT be used if alternate address 1284 * with sufficient scope is available" 1285 * (2b) nothing mentioned otherwise. 1286 * Here we fall into (2b) case as we have no choice in 1287 * our source address selection - we must obey the peer. 1288 * 1289 * The wording in RFC2462 is confusing, and there are 1290 * multiple description text for deprecated address 1291 * handling - worse, they are not exactly the same. 1292 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1293 */ 1294 if (isipv6 && !V_ip6_use_deprecated) { 1295 struct in6_ifaddr *ia6; 1296 1297 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1298 if (ia6 != NULL && 1299 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1300 ifa_free(&ia6->ia_ifa); 1301 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1302 log(LOG_DEBUG, "%s; %s: Listen socket: " 1303 "Connection attempt to deprecated " 1304 "IPv6 address rejected\n", 1305 s, __func__); 1306 rstreason = BANDLIM_RST_OPENPORT; 1307 goto dropwithreset; 1308 } 1309 if (ia6) 1310 ifa_free(&ia6->ia_ifa); 1311 } 1312 #endif /* INET6 */ 1313 /* 1314 * Basic sanity checks on incoming SYN requests: 1315 * Don't respond if the destination is a link layer 1316 * broadcast according to RFC1122 4.2.3.10, p. 104. 1317 * If it is from this socket it must be forged. 1318 * Don't respond if the source or destination is a 1319 * global or subnet broad- or multicast address. 1320 * Note that it is quite possible to receive unicast 1321 * link-layer packets with a broadcast IP address. Use 1322 * in_broadcast() to find them. 1323 */ 1324 if (m->m_flags & (M_BCAST|M_MCAST)) { 1325 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1326 log(LOG_DEBUG, "%s; %s: Listen socket: " 1327 "Connection attempt from broad- or multicast " 1328 "link layer address ignored\n", s, __func__); 1329 goto dropunlock; 1330 } 1331 #ifdef INET6 1332 if (isipv6) { 1333 if (th->th_dport == th->th_sport && 1334 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1335 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1336 log(LOG_DEBUG, "%s; %s: Listen socket: " 1337 "Connection attempt to/from self " 1338 "ignored\n", s, __func__); 1339 goto dropunlock; 1340 } 1341 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1342 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1343 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1344 log(LOG_DEBUG, "%s; %s: Listen socket: " 1345 "Connection attempt from/to multicast " 1346 "address ignored\n", s, __func__); 1347 goto dropunlock; 1348 } 1349 } 1350 #endif 1351 #if defined(INET) && defined(INET6) 1352 else 1353 #endif 1354 #ifdef INET 1355 { 1356 if (th->th_dport == th->th_sport && 1357 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1358 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1359 log(LOG_DEBUG, "%s; %s: Listen socket: " 1360 "Connection attempt from/to self " 1361 "ignored\n", s, __func__); 1362 goto dropunlock; 1363 } 1364 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1365 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1366 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1367 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1368 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1369 log(LOG_DEBUG, "%s; %s: Listen socket: " 1370 "Connection attempt from/to broad- " 1371 "or multicast address ignored\n", 1372 s, __func__); 1373 goto dropunlock; 1374 } 1375 } 1376 #endif 1377 /* 1378 * SYN appears to be valid. Create compressed TCP state 1379 * for syncache. 1380 */ 1381 #ifdef TCPDEBUG 1382 if (so->so_options & SO_DEBUG) 1383 tcp_trace(TA_INPUT, ostate, tp, 1384 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1385 #endif 1386 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1387 tcp_dooptions(&to, optp, optlen, TO_SYN); 1388 #ifdef TCP_RFC7413 1389 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL)) 1390 goto tfo_socket_result; 1391 #else 1392 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1393 #endif 1394 /* 1395 * Entry added to syncache and mbuf consumed. 1396 * Only the listen socket is unlocked by syncache_add(). 1397 */ 1398 if (ti_locked == TI_RLOCKED) { 1399 INP_INFO_RUNLOCK(&V_tcbinfo); 1400 ti_locked = TI_UNLOCKED; 1401 } 1402 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1403 return (IPPROTO_DONE); 1404 } else if (tp->t_state == TCPS_LISTEN) { 1405 /* 1406 * When a listen socket is torn down the SO_ACCEPTCONN 1407 * flag is removed first while connections are drained 1408 * from the accept queue in a unlock/lock cycle of the 1409 * ACCEPT_LOCK, opening a race condition allowing a SYN 1410 * attempt go through unhandled. 1411 */ 1412 goto dropunlock; 1413 } 1414 1415 #ifdef TCP_SIGNATURE 1416 if (sig_checked == 0) { 1417 tcp_dooptions(&to, optp, optlen, 1418 (thflags & TH_SYN) ? TO_SYN : 0); 1419 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1420 th, tp->t_flags)) { 1421 1422 /* 1423 * In SYN_SENT state if it receives an RST, it is 1424 * allowed for further processing. 1425 */ 1426 if ((thflags & TH_RST) == 0 || 1427 (tp->t_state == TCPS_SYN_SENT) == 0) 1428 goto dropunlock; 1429 } 1430 sig_checked = 1; 1431 } 1432 #endif 1433 1434 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1435 1436 /* 1437 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1438 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1439 * the inpcb, and unlocks pcbinfo. 1440 */ 1441 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1442 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1443 return (IPPROTO_DONE); 1444 1445 dropwithreset: 1446 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1447 1448 if (ti_locked == TI_RLOCKED) { 1449 INP_INFO_RUNLOCK(&V_tcbinfo); 1450 ti_locked = TI_UNLOCKED; 1451 } 1452 #ifdef INVARIANTS 1453 else { 1454 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1455 "ti_locked: %d", __func__, ti_locked)); 1456 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1457 } 1458 #endif 1459 1460 if (inp != NULL) { 1461 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1462 INP_WUNLOCK(inp); 1463 } else 1464 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1465 m = NULL; /* mbuf chain got consumed. */ 1466 goto drop; 1467 1468 dropunlock: 1469 if (m != NULL) 1470 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1471 1472 if (ti_locked == TI_RLOCKED) { 1473 INP_INFO_RUNLOCK(&V_tcbinfo); 1474 ti_locked = TI_UNLOCKED; 1475 } 1476 #ifdef INVARIANTS 1477 else { 1478 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1479 "ti_locked: %d", __func__, ti_locked)); 1480 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1481 } 1482 #endif 1483 1484 if (inp != NULL) 1485 INP_WUNLOCK(inp); 1486 1487 drop: 1488 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1489 if (s != NULL) 1490 free(s, M_TCPLOG); 1491 if (m != NULL) 1492 m_freem(m); 1493 return (IPPROTO_DONE); 1494 } 1495 1496 void 1497 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1498 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1499 int ti_locked) 1500 { 1501 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1502 int rstreason, todrop, win; 1503 uint32_t tiwin; 1504 uint16_t nsegs; 1505 char *s; 1506 struct in_conninfo *inc; 1507 struct mbuf *mfree; 1508 struct tcpopt to; 1509 #ifdef TCP_RFC7413 1510 int tfo_syn; 1511 #endif 1512 1513 #ifdef TCPDEBUG 1514 /* 1515 * The size of tcp_saveipgen must be the size of the max ip header, 1516 * now IPv6. 1517 */ 1518 u_char tcp_saveipgen[IP6_HDR_LEN]; 1519 struct tcphdr tcp_savetcp; 1520 short ostate = 0; 1521 #endif 1522 thflags = th->th_flags; 1523 inc = &tp->t_inpcb->inp_inc; 1524 tp->sackhint.last_sack_ack = 0; 1525 sack_changed = 0; 1526 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1527 1528 /* 1529 * If this is either a state-changing packet or current state isn't 1530 * established, we require a write lock on tcbinfo. Otherwise, we 1531 * allow the tcbinfo to be in either alocked or unlocked, as the 1532 * caller may have unnecessarily acquired a write lock due to a race. 1533 */ 1534 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1535 tp->t_state != TCPS_ESTABLISHED) { 1536 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for " 1537 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1538 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1539 } else { 1540 #ifdef INVARIANTS 1541 if (ti_locked == TI_RLOCKED) 1542 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1543 else { 1544 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1545 "ti_locked: %d", __func__, ti_locked)); 1546 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1547 } 1548 #endif 1549 } 1550 INP_WLOCK_ASSERT(tp->t_inpcb); 1551 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1552 __func__)); 1553 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1554 __func__)); 1555 1556 #ifdef TCPPCAP 1557 /* Save segment, if requested. */ 1558 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1559 #endif 1560 1561 /* 1562 * Segment received on connection. 1563 * Reset idle time and keep-alive timer. 1564 * XXX: This should be done after segment 1565 * validation to ignore broken/spoofed segs. 1566 */ 1567 tp->t_rcvtime = ticks; 1568 1569 /* 1570 * Scale up the window into a 32-bit value. 1571 * For the SYN_SENT state the scale is zero. 1572 */ 1573 tiwin = th->th_win << tp->snd_scale; 1574 1575 /* 1576 * TCP ECN processing. 1577 */ 1578 if (tp->t_flags & TF_ECN_PERMIT) { 1579 if (thflags & TH_CWR) 1580 tp->t_flags &= ~TF_ECN_SND_ECE; 1581 switch (iptos & IPTOS_ECN_MASK) { 1582 case IPTOS_ECN_CE: 1583 tp->t_flags |= TF_ECN_SND_ECE; 1584 TCPSTAT_INC(tcps_ecn_ce); 1585 break; 1586 case IPTOS_ECN_ECT0: 1587 TCPSTAT_INC(tcps_ecn_ect0); 1588 break; 1589 case IPTOS_ECN_ECT1: 1590 TCPSTAT_INC(tcps_ecn_ect1); 1591 break; 1592 } 1593 1594 /* Process a packet differently from RFC3168. */ 1595 cc_ecnpkt_handler(tp, th, iptos); 1596 1597 /* Congestion experienced. */ 1598 if (thflags & TH_ECE) { 1599 cc_cong_signal(tp, th, CC_ECN); 1600 } 1601 } 1602 1603 /* 1604 * Parse options on any incoming segment. 1605 */ 1606 tcp_dooptions(&to, (u_char *)(th + 1), 1607 (th->th_off << 2) - sizeof(struct tcphdr), 1608 (thflags & TH_SYN) ? TO_SYN : 0); 1609 1610 /* 1611 * If echoed timestamp is later than the current time, 1612 * fall back to non RFC1323 RTT calculation. Normalize 1613 * timestamp if syncookies were used when this connection 1614 * was established. 1615 */ 1616 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1617 to.to_tsecr -= tp->ts_offset; 1618 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1619 to.to_tsecr = 0; 1620 } 1621 /* 1622 * If timestamps were negotiated during SYN/ACK they should 1623 * appear on every segment during this session and vice versa. 1624 */ 1625 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1626 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1627 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1628 "no action\n", s, __func__); 1629 free(s, M_TCPLOG); 1630 } 1631 } 1632 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1633 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1634 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1635 "no action\n", s, __func__); 1636 free(s, M_TCPLOG); 1637 } 1638 } 1639 1640 /* 1641 * Process options only when we get SYN/ACK back. The SYN case 1642 * for incoming connections is handled in tcp_syncache. 1643 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1644 * or <SYN,ACK>) segment itself is never scaled. 1645 * XXX this is traditional behavior, may need to be cleaned up. 1646 */ 1647 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1648 if ((to.to_flags & TOF_SCALE) && 1649 (tp->t_flags & TF_REQ_SCALE)) { 1650 tp->t_flags |= TF_RCVD_SCALE; 1651 tp->snd_scale = to.to_wscale; 1652 } 1653 /* 1654 * Initial send window. It will be updated with 1655 * the next incoming segment to the scaled value. 1656 */ 1657 tp->snd_wnd = th->th_win; 1658 if (to.to_flags & TOF_TS) { 1659 tp->t_flags |= TF_RCVD_TSTMP; 1660 tp->ts_recent = to.to_tsval; 1661 tp->ts_recent_age = tcp_ts_getticks(); 1662 } 1663 if (to.to_flags & TOF_MSS) 1664 tcp_mss(tp, to.to_mss); 1665 if ((tp->t_flags & TF_SACK_PERMIT) && 1666 (to.to_flags & TOF_SACKPERM) == 0) 1667 tp->t_flags &= ~TF_SACK_PERMIT; 1668 } 1669 1670 /* 1671 * Header prediction: check for the two common cases 1672 * of a uni-directional data xfer. If the packet has 1673 * no control flags, is in-sequence, the window didn't 1674 * change and we're not retransmitting, it's a 1675 * candidate. If the length is zero and the ack moved 1676 * forward, we're the sender side of the xfer. Just 1677 * free the data acked & wake any higher level process 1678 * that was blocked waiting for space. If the length 1679 * is non-zero and the ack didn't move, we're the 1680 * receiver side. If we're getting packets in-order 1681 * (the reassembly queue is empty), add the data to 1682 * the socket buffer and note that we need a delayed ack. 1683 * Make sure that the hidden state-flags are also off. 1684 * Since we check for TCPS_ESTABLISHED first, it can only 1685 * be TH_NEEDSYN. 1686 */ 1687 if (tp->t_state == TCPS_ESTABLISHED && 1688 th->th_seq == tp->rcv_nxt && 1689 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1690 tp->snd_nxt == tp->snd_max && 1691 tiwin && tiwin == tp->snd_wnd && 1692 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1693 LIST_EMPTY(&tp->t_segq) && 1694 ((to.to_flags & TOF_TS) == 0 || 1695 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1696 1697 /* 1698 * If last ACK falls within this segment's sequence numbers, 1699 * record the timestamp. 1700 * NOTE that the test is modified according to the latest 1701 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1702 */ 1703 if ((to.to_flags & TOF_TS) != 0 && 1704 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1705 tp->ts_recent_age = tcp_ts_getticks(); 1706 tp->ts_recent = to.to_tsval; 1707 } 1708 1709 if (tlen == 0) { 1710 if (SEQ_GT(th->th_ack, tp->snd_una) && 1711 SEQ_LEQ(th->th_ack, tp->snd_max) && 1712 !IN_RECOVERY(tp->t_flags) && 1713 (to.to_flags & TOF_SACK) == 0 && 1714 TAILQ_EMPTY(&tp->snd_holes)) { 1715 /* 1716 * This is a pure ack for outstanding data. 1717 */ 1718 if (ti_locked == TI_RLOCKED) 1719 INP_INFO_RUNLOCK(&V_tcbinfo); 1720 ti_locked = TI_UNLOCKED; 1721 1722 TCPSTAT_INC(tcps_predack); 1723 1724 /* 1725 * "bad retransmit" recovery. 1726 */ 1727 if (tp->t_rxtshift == 1 && 1728 tp->t_flags & TF_PREVVALID && 1729 (int)(ticks - tp->t_badrxtwin) < 0) { 1730 cc_cong_signal(tp, th, CC_RTO_ERR); 1731 } 1732 1733 /* 1734 * Recalculate the transmit timer / rtt. 1735 * 1736 * Some boxes send broken timestamp replies 1737 * during the SYN+ACK phase, ignore 1738 * timestamps of 0 or we could calculate a 1739 * huge RTT and blow up the retransmit timer. 1740 */ 1741 if ((to.to_flags & TOF_TS) != 0 && 1742 to.to_tsecr) { 1743 uint32_t t; 1744 1745 t = tcp_ts_getticks() - to.to_tsecr; 1746 if (!tp->t_rttlow || tp->t_rttlow > t) 1747 tp->t_rttlow = t; 1748 tcp_xmit_timer(tp, 1749 TCP_TS_TO_TICKS(t) + 1); 1750 } else if (tp->t_rtttime && 1751 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1752 if (!tp->t_rttlow || 1753 tp->t_rttlow > ticks - tp->t_rtttime) 1754 tp->t_rttlow = ticks - tp->t_rtttime; 1755 tcp_xmit_timer(tp, 1756 ticks - tp->t_rtttime); 1757 } 1758 acked = BYTES_THIS_ACK(tp, th); 1759 1760 #ifdef TCP_HHOOK 1761 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1762 hhook_run_tcp_est_in(tp, th, &to); 1763 #endif 1764 1765 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1766 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1767 sbdrop(&so->so_snd, acked); 1768 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1769 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1770 tp->snd_recover = th->th_ack - 1; 1771 1772 /* 1773 * Let the congestion control algorithm update 1774 * congestion control related information. This 1775 * typically means increasing the congestion 1776 * window. 1777 */ 1778 cc_ack_received(tp, th, nsegs, CC_ACK); 1779 1780 tp->snd_una = th->th_ack; 1781 /* 1782 * Pull snd_wl2 up to prevent seq wrap relative 1783 * to th_ack. 1784 */ 1785 tp->snd_wl2 = th->th_ack; 1786 tp->t_dupacks = 0; 1787 m_freem(m); 1788 1789 /* 1790 * If all outstanding data are acked, stop 1791 * retransmit timer, otherwise restart timer 1792 * using current (possibly backed-off) value. 1793 * If process is waiting for space, 1794 * wakeup/selwakeup/signal. If data 1795 * are ready to send, let tcp_output 1796 * decide between more output or persist. 1797 */ 1798 #ifdef TCPDEBUG 1799 if (so->so_options & SO_DEBUG) 1800 tcp_trace(TA_INPUT, ostate, tp, 1801 (void *)tcp_saveipgen, 1802 &tcp_savetcp, 0); 1803 #endif 1804 TCP_PROBE3(debug__input, tp, th, 1805 mtod(m, const char *)); 1806 if (tp->snd_una == tp->snd_max) 1807 tcp_timer_activate(tp, TT_REXMT, 0); 1808 else if (!tcp_timer_active(tp, TT_PERSIST)) 1809 tcp_timer_activate(tp, TT_REXMT, 1810 tp->t_rxtcur); 1811 sowwakeup(so); 1812 if (sbavail(&so->so_snd)) 1813 (void) tp->t_fb->tfb_tcp_output(tp); 1814 goto check_delack; 1815 } 1816 } else if (th->th_ack == tp->snd_una && 1817 tlen <= sbspace(&so->so_rcv)) { 1818 int newsize = 0; /* automatic sockbuf scaling */ 1819 1820 /* 1821 * This is a pure, in-sequence data packet with 1822 * nothing on the reassembly queue and we have enough 1823 * buffer space to take it. 1824 */ 1825 if (ti_locked == TI_RLOCKED) 1826 INP_INFO_RUNLOCK(&V_tcbinfo); 1827 ti_locked = TI_UNLOCKED; 1828 1829 /* Clean receiver SACK report if present */ 1830 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1831 tcp_clean_sackreport(tp); 1832 TCPSTAT_INC(tcps_preddat); 1833 tp->rcv_nxt += tlen; 1834 /* 1835 * Pull snd_wl1 up to prevent seq wrap relative to 1836 * th_seq. 1837 */ 1838 tp->snd_wl1 = th->th_seq; 1839 /* 1840 * Pull rcv_up up to prevent seq wrap relative to 1841 * rcv_nxt. 1842 */ 1843 tp->rcv_up = tp->rcv_nxt; 1844 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1845 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1846 #ifdef TCPDEBUG 1847 if (so->so_options & SO_DEBUG) 1848 tcp_trace(TA_INPUT, ostate, tp, 1849 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1850 #endif 1851 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1852 1853 /* 1854 * Automatic sizing of receive socket buffer. Often the send 1855 * buffer size is not optimally adjusted to the actual network 1856 * conditions at hand (delay bandwidth product). Setting the 1857 * buffer size too small limits throughput on links with high 1858 * bandwidth and high delay (eg. trans-continental/oceanic links). 1859 * 1860 * On the receive side the socket buffer memory is only rarely 1861 * used to any significant extent. This allows us to be much 1862 * more aggressive in scaling the receive socket buffer. For 1863 * the case that the buffer space is actually used to a large 1864 * extent and we run out of kernel memory we can simply drop 1865 * the new segments; TCP on the sender will just retransmit it 1866 * later. Setting the buffer size too big may only consume too 1867 * much kernel memory if the application doesn't read() from 1868 * the socket or packet loss or reordering makes use of the 1869 * reassembly queue. 1870 * 1871 * The criteria to step up the receive buffer one notch are: 1872 * 1. Application has not set receive buffer size with 1873 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1874 * 2. the number of bytes received during the time it takes 1875 * one timestamp to be reflected back to us (the RTT); 1876 * 3. received bytes per RTT is within seven eighth of the 1877 * current socket buffer size; 1878 * 4. receive buffer size has not hit maximal automatic size; 1879 * 1880 * This algorithm does one step per RTT at most and only if 1881 * we receive a bulk stream w/o packet losses or reorderings. 1882 * Shrinking the buffer during idle times is not necessary as 1883 * it doesn't consume any memory when idle. 1884 * 1885 * TODO: Only step up if the application is actually serving 1886 * the buffer to better manage the socket buffer resources. 1887 */ 1888 if (V_tcp_do_autorcvbuf && 1889 (to.to_flags & TOF_TS) && 1890 to.to_tsecr && 1891 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1892 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1893 to.to_tsecr - tp->rfbuf_ts < hz) { 1894 if (tp->rfbuf_cnt > 1895 (so->so_rcv.sb_hiwat / 8 * 7) && 1896 so->so_rcv.sb_hiwat < 1897 V_tcp_autorcvbuf_max) { 1898 newsize = 1899 min(so->so_rcv.sb_hiwat + 1900 V_tcp_autorcvbuf_inc, 1901 V_tcp_autorcvbuf_max); 1902 } 1903 /* Start over with next RTT. */ 1904 tp->rfbuf_ts = 0; 1905 tp->rfbuf_cnt = 0; 1906 } else 1907 tp->rfbuf_cnt += tlen; /* add up */ 1908 } 1909 1910 /* Add data to socket buffer. */ 1911 SOCKBUF_LOCK(&so->so_rcv); 1912 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1913 m_freem(m); 1914 } else { 1915 /* 1916 * Set new socket buffer size. 1917 * Give up when limit is reached. 1918 */ 1919 if (newsize) 1920 if (!sbreserve_locked(&so->so_rcv, 1921 newsize, so, NULL)) 1922 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1923 m_adj(m, drop_hdrlen); /* delayed header drop */ 1924 sbappendstream_locked(&so->so_rcv, m, 0); 1925 } 1926 /* NB: sorwakeup_locked() does an implicit unlock. */ 1927 sorwakeup_locked(so); 1928 if (DELAY_ACK(tp, tlen)) { 1929 tp->t_flags |= TF_DELACK; 1930 } else { 1931 tp->t_flags |= TF_ACKNOW; 1932 tp->t_fb->tfb_tcp_output(tp); 1933 } 1934 goto check_delack; 1935 } 1936 } 1937 1938 /* 1939 * Calculate amount of space in receive window, 1940 * and then do TCP input processing. 1941 * Receive window is amount of space in rcv queue, 1942 * but not less than advertised window. 1943 */ 1944 win = sbspace(&so->so_rcv); 1945 if (win < 0) 1946 win = 0; 1947 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1948 1949 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1950 tp->rfbuf_ts = 0; 1951 tp->rfbuf_cnt = 0; 1952 1953 switch (tp->t_state) { 1954 1955 /* 1956 * If the state is SYN_RECEIVED: 1957 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1958 */ 1959 case TCPS_SYN_RECEIVED: 1960 if ((thflags & TH_ACK) && 1961 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1962 SEQ_GT(th->th_ack, tp->snd_max))) { 1963 rstreason = BANDLIM_RST_OPENPORT; 1964 goto dropwithreset; 1965 } 1966 #ifdef TCP_RFC7413 1967 if (IS_FASTOPEN(tp->t_flags)) { 1968 /* 1969 * When a TFO connection is in SYN_RECEIVED, the 1970 * only valid packets are the initial SYN, a 1971 * retransmit/copy of the initial SYN (possibly with 1972 * a subset of the original data), a valid ACK, a 1973 * FIN, or a RST. 1974 */ 1975 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1976 rstreason = BANDLIM_RST_OPENPORT; 1977 goto dropwithreset; 1978 } else if (thflags & TH_SYN) { 1979 /* non-initial SYN is ignored */ 1980 if ((tcp_timer_active(tp, TT_DELACK) || 1981 tcp_timer_active(tp, TT_REXMT))) 1982 goto drop; 1983 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1984 goto drop; 1985 } 1986 } 1987 #endif 1988 break; 1989 1990 /* 1991 * If the state is SYN_SENT: 1992 * if seg contains an ACK, but not for our SYN, drop the input. 1993 * if seg contains a RST, then drop the connection. 1994 * if seg does not contain SYN, then drop it. 1995 * Otherwise this is an acceptable SYN segment 1996 * initialize tp->rcv_nxt and tp->irs 1997 * if seg contains ack then advance tp->snd_una 1998 * if seg contains an ECE and ECN support is enabled, the stream 1999 * is ECN capable. 2000 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 2001 * arrange for segment to be acked (eventually) 2002 * continue processing rest of data/controls, beginning with URG 2003 */ 2004 case TCPS_SYN_SENT: 2005 if ((thflags & TH_ACK) && 2006 (SEQ_LEQ(th->th_ack, tp->iss) || 2007 SEQ_GT(th->th_ack, tp->snd_max))) { 2008 rstreason = BANDLIM_UNLIMITED; 2009 goto dropwithreset; 2010 } 2011 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 2012 TCP_PROBE5(connect__refused, NULL, tp, 2013 mtod(m, const char *), tp, th); 2014 tp = tcp_drop(tp, ECONNREFUSED); 2015 } 2016 if (thflags & TH_RST) 2017 goto drop; 2018 if (!(thflags & TH_SYN)) 2019 goto drop; 2020 2021 tp->irs = th->th_seq; 2022 tcp_rcvseqinit(tp); 2023 if (thflags & TH_ACK) { 2024 TCPSTAT_INC(tcps_connects); 2025 soisconnected(so); 2026 #ifdef MAC 2027 mac_socketpeer_set_from_mbuf(m, so); 2028 #endif 2029 /* Do window scaling on this connection? */ 2030 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2031 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2032 tp->rcv_scale = tp->request_r_scale; 2033 } 2034 tp->rcv_adv += min(tp->rcv_wnd, 2035 TCP_MAXWIN << tp->rcv_scale); 2036 tp->snd_una++; /* SYN is acked */ 2037 /* 2038 * If there's data, delay ACK; if there's also a FIN 2039 * ACKNOW will be turned on later. 2040 */ 2041 if (DELAY_ACK(tp, tlen) && tlen != 0) 2042 tcp_timer_activate(tp, TT_DELACK, 2043 tcp_delacktime); 2044 else 2045 tp->t_flags |= TF_ACKNOW; 2046 2047 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 2048 tp->t_flags |= TF_ECN_PERMIT; 2049 TCPSTAT_INC(tcps_ecn_shs); 2050 } 2051 2052 /* 2053 * Received <SYN,ACK> in SYN_SENT[*] state. 2054 * Transitions: 2055 * SYN_SENT --> ESTABLISHED 2056 * SYN_SENT* --> FIN_WAIT_1 2057 */ 2058 tp->t_starttime = ticks; 2059 if (tp->t_flags & TF_NEEDFIN) { 2060 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2061 tp->t_flags &= ~TF_NEEDFIN; 2062 thflags &= ~TH_SYN; 2063 } else { 2064 tcp_state_change(tp, TCPS_ESTABLISHED); 2065 TCP_PROBE5(connect__established, NULL, tp, 2066 mtod(m, const char *), tp, th); 2067 cc_conn_init(tp); 2068 tcp_timer_activate(tp, TT_KEEP, 2069 TP_KEEPIDLE(tp)); 2070 } 2071 } else { 2072 /* 2073 * Received initial SYN in SYN-SENT[*] state => 2074 * simultaneous open. 2075 * If it succeeds, connection is * half-synchronized. 2076 * Otherwise, do 3-way handshake: 2077 * SYN-SENT -> SYN-RECEIVED 2078 * SYN-SENT* -> SYN-RECEIVED* 2079 */ 2080 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2081 tcp_timer_activate(tp, TT_REXMT, 0); 2082 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2083 } 2084 2085 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: " 2086 "ti_locked %d", __func__, ti_locked)); 2087 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2088 INP_WLOCK_ASSERT(tp->t_inpcb); 2089 2090 /* 2091 * Advance th->th_seq to correspond to first data byte. 2092 * If data, trim to stay within window, 2093 * dropping FIN if necessary. 2094 */ 2095 th->th_seq++; 2096 if (tlen > tp->rcv_wnd) { 2097 todrop = tlen - tp->rcv_wnd; 2098 m_adj(m, -todrop); 2099 tlen = tp->rcv_wnd; 2100 thflags &= ~TH_FIN; 2101 TCPSTAT_INC(tcps_rcvpackafterwin); 2102 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2103 } 2104 tp->snd_wl1 = th->th_seq - 1; 2105 tp->rcv_up = th->th_seq; 2106 /* 2107 * Client side of transaction: already sent SYN and data. 2108 * If the remote host used T/TCP to validate the SYN, 2109 * our data will be ACK'd; if so, enter normal data segment 2110 * processing in the middle of step 5, ack processing. 2111 * Otherwise, goto step 6. 2112 */ 2113 if (thflags & TH_ACK) 2114 goto process_ACK; 2115 2116 goto step6; 2117 2118 /* 2119 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2120 * do normal processing. 2121 * 2122 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2123 */ 2124 case TCPS_LAST_ACK: 2125 case TCPS_CLOSING: 2126 break; /* continue normal processing */ 2127 } 2128 2129 /* 2130 * States other than LISTEN or SYN_SENT. 2131 * First check the RST flag and sequence number since reset segments 2132 * are exempt from the timestamp and connection count tests. This 2133 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2134 * below which allowed reset segments in half the sequence space 2135 * to fall though and be processed (which gives forged reset 2136 * segments with a random sequence number a 50 percent chance of 2137 * killing a connection). 2138 * Then check timestamp, if present. 2139 * Then check the connection count, if present. 2140 * Then check that at least some bytes of segment are within 2141 * receive window. If segment begins before rcv_nxt, 2142 * drop leading data (and SYN); if nothing left, just ack. 2143 */ 2144 if (thflags & TH_RST) { 2145 /* 2146 * RFC5961 Section 3.2 2147 * 2148 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2149 * - If RST is in window, we send challenge ACK. 2150 * 2151 * Note: to take into account delayed ACKs, we should 2152 * test against last_ack_sent instead of rcv_nxt. 2153 * Note 2: we handle special case of closed window, not 2154 * covered by the RFC. 2155 */ 2156 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2157 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2158 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2159 2160 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2161 KASSERT(ti_locked == TI_RLOCKED, 2162 ("%s: TH_RST ti_locked %d, th %p tp %p", 2163 __func__, ti_locked, th, tp)); 2164 KASSERT(tp->t_state != TCPS_SYN_SENT, 2165 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2166 __func__, th, tp)); 2167 2168 if (V_tcp_insecure_rst || 2169 tp->last_ack_sent == th->th_seq) { 2170 TCPSTAT_INC(tcps_drops); 2171 /* Drop the connection. */ 2172 switch (tp->t_state) { 2173 case TCPS_SYN_RECEIVED: 2174 so->so_error = ECONNREFUSED; 2175 goto close; 2176 case TCPS_ESTABLISHED: 2177 case TCPS_FIN_WAIT_1: 2178 case TCPS_FIN_WAIT_2: 2179 case TCPS_CLOSE_WAIT: 2180 so->so_error = ECONNRESET; 2181 close: 2182 tcp_state_change(tp, TCPS_CLOSED); 2183 /* FALLTHROUGH */ 2184 default: 2185 tp = tcp_close(tp); 2186 } 2187 } else { 2188 TCPSTAT_INC(tcps_badrst); 2189 /* Send challenge ACK. */ 2190 tcp_respond(tp, mtod(m, void *), th, m, 2191 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2192 tp->last_ack_sent = tp->rcv_nxt; 2193 m = NULL; 2194 } 2195 } 2196 goto drop; 2197 } 2198 2199 /* 2200 * RFC5961 Section 4.2 2201 * Send challenge ACK for any SYN in synchronized state. 2202 */ 2203 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2204 tp->t_state != TCPS_SYN_RECEIVED) { 2205 KASSERT(ti_locked == TI_RLOCKED, 2206 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2207 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2208 2209 TCPSTAT_INC(tcps_badsyn); 2210 if (V_tcp_insecure_syn && 2211 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2212 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2213 tp = tcp_drop(tp, ECONNRESET); 2214 rstreason = BANDLIM_UNLIMITED; 2215 } else { 2216 /* Send challenge ACK. */ 2217 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2218 tp->snd_nxt, TH_ACK); 2219 tp->last_ack_sent = tp->rcv_nxt; 2220 m = NULL; 2221 } 2222 goto drop; 2223 } 2224 2225 /* 2226 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2227 * and it's less than ts_recent, drop it. 2228 */ 2229 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2230 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2231 2232 /* Check to see if ts_recent is over 24 days old. */ 2233 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2234 /* 2235 * Invalidate ts_recent. If this segment updates 2236 * ts_recent, the age will be reset later and ts_recent 2237 * will get a valid value. If it does not, setting 2238 * ts_recent to zero will at least satisfy the 2239 * requirement that zero be placed in the timestamp 2240 * echo reply when ts_recent isn't valid. The 2241 * age isn't reset until we get a valid ts_recent 2242 * because we don't want out-of-order segments to be 2243 * dropped when ts_recent is old. 2244 */ 2245 tp->ts_recent = 0; 2246 } else { 2247 TCPSTAT_INC(tcps_rcvduppack); 2248 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2249 TCPSTAT_INC(tcps_pawsdrop); 2250 if (tlen) 2251 goto dropafterack; 2252 goto drop; 2253 } 2254 } 2255 2256 /* 2257 * In the SYN-RECEIVED state, validate that the packet belongs to 2258 * this connection before trimming the data to fit the receive 2259 * window. Check the sequence number versus IRS since we know 2260 * the sequence numbers haven't wrapped. This is a partial fix 2261 * for the "LAND" DoS attack. 2262 */ 2263 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2264 rstreason = BANDLIM_RST_OPENPORT; 2265 goto dropwithreset; 2266 } 2267 2268 todrop = tp->rcv_nxt - th->th_seq; 2269 if (todrop > 0) { 2270 if (thflags & TH_SYN) { 2271 thflags &= ~TH_SYN; 2272 th->th_seq++; 2273 if (th->th_urp > 1) 2274 th->th_urp--; 2275 else 2276 thflags &= ~TH_URG; 2277 todrop--; 2278 } 2279 /* 2280 * Following if statement from Stevens, vol. 2, p. 960. 2281 */ 2282 if (todrop > tlen 2283 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2284 /* 2285 * Any valid FIN must be to the left of the window. 2286 * At this point the FIN must be a duplicate or out 2287 * of sequence; drop it. 2288 */ 2289 thflags &= ~TH_FIN; 2290 2291 /* 2292 * Send an ACK to resynchronize and drop any data. 2293 * But keep on processing for RST or ACK. 2294 */ 2295 tp->t_flags |= TF_ACKNOW; 2296 todrop = tlen; 2297 TCPSTAT_INC(tcps_rcvduppack); 2298 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2299 } else { 2300 TCPSTAT_INC(tcps_rcvpartduppack); 2301 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2302 } 2303 drop_hdrlen += todrop; /* drop from the top afterwards */ 2304 th->th_seq += todrop; 2305 tlen -= todrop; 2306 if (th->th_urp > todrop) 2307 th->th_urp -= todrop; 2308 else { 2309 thflags &= ~TH_URG; 2310 th->th_urp = 0; 2311 } 2312 } 2313 2314 /* 2315 * If new data are received on a connection after the 2316 * user processes are gone, then RST the other end. 2317 */ 2318 if ((so->so_state & SS_NOFDREF) && 2319 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2320 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && " 2321 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2322 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2323 2324 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2325 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2326 "after socket was closed, " 2327 "sending RST and removing tcpcb\n", 2328 s, __func__, tcpstates[tp->t_state], tlen); 2329 free(s, M_TCPLOG); 2330 } 2331 tp = tcp_close(tp); 2332 TCPSTAT_INC(tcps_rcvafterclose); 2333 rstreason = BANDLIM_UNLIMITED; 2334 goto dropwithreset; 2335 } 2336 2337 /* 2338 * If segment ends after window, drop trailing data 2339 * (and PUSH and FIN); if nothing left, just ACK. 2340 */ 2341 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2342 if (todrop > 0) { 2343 TCPSTAT_INC(tcps_rcvpackafterwin); 2344 if (todrop >= tlen) { 2345 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2346 /* 2347 * If window is closed can only take segments at 2348 * window edge, and have to drop data and PUSH from 2349 * incoming segments. Continue processing, but 2350 * remember to ack. Otherwise, drop segment 2351 * and ack. 2352 */ 2353 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2354 tp->t_flags |= TF_ACKNOW; 2355 TCPSTAT_INC(tcps_rcvwinprobe); 2356 } else 2357 goto dropafterack; 2358 } else 2359 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2360 m_adj(m, -todrop); 2361 tlen -= todrop; 2362 thflags &= ~(TH_PUSH|TH_FIN); 2363 } 2364 2365 /* 2366 * If last ACK falls within this segment's sequence numbers, 2367 * record its timestamp. 2368 * NOTE: 2369 * 1) That the test incorporates suggestions from the latest 2370 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2371 * 2) That updating only on newer timestamps interferes with 2372 * our earlier PAWS tests, so this check should be solely 2373 * predicated on the sequence space of this segment. 2374 * 3) That we modify the segment boundary check to be 2375 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2376 * instead of RFC1323's 2377 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2378 * This modified check allows us to overcome RFC1323's 2379 * limitations as described in Stevens TCP/IP Illustrated 2380 * Vol. 2 p.869. In such cases, we can still calculate the 2381 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2382 */ 2383 if ((to.to_flags & TOF_TS) != 0 && 2384 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2385 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2386 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2387 tp->ts_recent_age = tcp_ts_getticks(); 2388 tp->ts_recent = to.to_tsval; 2389 } 2390 2391 /* 2392 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2393 * flag is on (half-synchronized state), then queue data for 2394 * later processing; else drop segment and return. 2395 */ 2396 if ((thflags & TH_ACK) == 0) { 2397 if (tp->t_state == TCPS_SYN_RECEIVED || 2398 (tp->t_flags & TF_NEEDSYN)) { 2399 #ifdef TCP_RFC7413 2400 if (tp->t_state == TCPS_SYN_RECEIVED && 2401 IS_FASTOPEN(tp->t_flags)) { 2402 tp->snd_wnd = tiwin; 2403 cc_conn_init(tp); 2404 } 2405 #endif 2406 goto step6; 2407 } else if (tp->t_flags & TF_ACKNOW) 2408 goto dropafterack; 2409 else 2410 goto drop; 2411 } 2412 2413 /* 2414 * Ack processing. 2415 */ 2416 switch (tp->t_state) { 2417 2418 /* 2419 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2420 * ESTABLISHED state and continue processing. 2421 * The ACK was checked above. 2422 */ 2423 case TCPS_SYN_RECEIVED: 2424 2425 TCPSTAT_INC(tcps_connects); 2426 soisconnected(so); 2427 /* Do window scaling? */ 2428 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2429 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2430 tp->rcv_scale = tp->request_r_scale; 2431 tp->snd_wnd = tiwin; 2432 } 2433 /* 2434 * Make transitions: 2435 * SYN-RECEIVED -> ESTABLISHED 2436 * SYN-RECEIVED* -> FIN-WAIT-1 2437 */ 2438 tp->t_starttime = ticks; 2439 if (tp->t_flags & TF_NEEDFIN) { 2440 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2441 tp->t_flags &= ~TF_NEEDFIN; 2442 } else { 2443 tcp_state_change(tp, TCPS_ESTABLISHED); 2444 TCP_PROBE5(accept__established, NULL, tp, 2445 mtod(m, const char *), tp, th); 2446 #ifdef TCP_RFC7413 2447 if (tp->t_tfo_pending) { 2448 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2449 tp->t_tfo_pending = NULL; 2450 2451 /* 2452 * Account for the ACK of our SYN prior to 2453 * regular ACK processing below. 2454 */ 2455 tp->snd_una++; 2456 } 2457 /* 2458 * TFO connections call cc_conn_init() during SYN 2459 * processing. Calling it again here for such 2460 * connections is not harmless as it would undo the 2461 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2462 * is retransmitted. 2463 */ 2464 if (!IS_FASTOPEN(tp->t_flags)) 2465 #endif 2466 cc_conn_init(tp); 2467 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2468 } 2469 /* 2470 * If segment contains data or ACK, will call tcp_reass() 2471 * later; if not, do so now to pass queued data to user. 2472 */ 2473 if (tlen == 0 && (thflags & TH_FIN) == 0) 2474 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2475 (struct mbuf *)0); 2476 tp->snd_wl1 = th->th_seq - 1; 2477 /* FALLTHROUGH */ 2478 2479 /* 2480 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2481 * ACKs. If the ack is in the range 2482 * tp->snd_una < th->th_ack <= tp->snd_max 2483 * then advance tp->snd_una to th->th_ack and drop 2484 * data from the retransmission queue. If this ACK reflects 2485 * more up to date window information we update our window information. 2486 */ 2487 case TCPS_ESTABLISHED: 2488 case TCPS_FIN_WAIT_1: 2489 case TCPS_FIN_WAIT_2: 2490 case TCPS_CLOSE_WAIT: 2491 case TCPS_CLOSING: 2492 case TCPS_LAST_ACK: 2493 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2494 TCPSTAT_INC(tcps_rcvacktoomuch); 2495 goto dropafterack; 2496 } 2497 if ((tp->t_flags & TF_SACK_PERMIT) && 2498 ((to.to_flags & TOF_SACK) || 2499 !TAILQ_EMPTY(&tp->snd_holes))) 2500 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2501 else 2502 /* 2503 * Reset the value so that previous (valid) value 2504 * from the last ack with SACK doesn't get used. 2505 */ 2506 tp->sackhint.sacked_bytes = 0; 2507 2508 #ifdef TCP_HHOOK 2509 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2510 hhook_run_tcp_est_in(tp, th, &to); 2511 #endif 2512 2513 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2514 u_int maxseg; 2515 2516 maxseg = tcp_maxseg(tp); 2517 if (tlen == 0 && 2518 (tiwin == tp->snd_wnd || 2519 (tp->t_flags & TF_SACK_PERMIT))) { 2520 /* 2521 * If this is the first time we've seen a 2522 * FIN from the remote, this is not a 2523 * duplicate and it needs to be processed 2524 * normally. This happens during a 2525 * simultaneous close. 2526 */ 2527 if ((thflags & TH_FIN) && 2528 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2529 tp->t_dupacks = 0; 2530 break; 2531 } 2532 TCPSTAT_INC(tcps_rcvdupack); 2533 /* 2534 * If we have outstanding data (other than 2535 * a window probe), this is a completely 2536 * duplicate ack (ie, window info didn't 2537 * change and FIN isn't set), 2538 * the ack is the biggest we've 2539 * seen and we've seen exactly our rexmt 2540 * threshold of them, assume a packet 2541 * has been dropped and retransmit it. 2542 * Kludge snd_nxt & the congestion 2543 * window so we send only this one 2544 * packet. 2545 * 2546 * We know we're losing at the current 2547 * window size so do congestion avoidance 2548 * (set ssthresh to half the current window 2549 * and pull our congestion window back to 2550 * the new ssthresh). 2551 * 2552 * Dup acks mean that packets have left the 2553 * network (they're now cached at the receiver) 2554 * so bump cwnd by the amount in the receiver 2555 * to keep a constant cwnd packets in the 2556 * network. 2557 * 2558 * When using TCP ECN, notify the peer that 2559 * we reduced the cwnd. 2560 */ 2561 /* 2562 * Following 2 kinds of acks should not affect 2563 * dupack counting: 2564 * 1) Old acks 2565 * 2) Acks with SACK but without any new SACK 2566 * information in them. These could result from 2567 * any anomaly in the network like a switch 2568 * duplicating packets or a possible DoS attack. 2569 */ 2570 if (th->th_ack != tp->snd_una || 2571 ((tp->t_flags & TF_SACK_PERMIT) && 2572 !sack_changed)) 2573 break; 2574 else if (!tcp_timer_active(tp, TT_REXMT)) 2575 tp->t_dupacks = 0; 2576 else if (++tp->t_dupacks > tcprexmtthresh || 2577 IN_FASTRECOVERY(tp->t_flags)) { 2578 cc_ack_received(tp, th, nsegs, 2579 CC_DUPACK); 2580 if ((tp->t_flags & TF_SACK_PERMIT) && 2581 IN_FASTRECOVERY(tp->t_flags)) { 2582 int awnd; 2583 2584 /* 2585 * Compute the amount of data in flight first. 2586 * We can inject new data into the pipe iff 2587 * we have less than 1/2 the original window's 2588 * worth of data in flight. 2589 */ 2590 if (V_tcp_do_rfc6675_pipe) 2591 awnd = tcp_compute_pipe(tp); 2592 else 2593 awnd = (tp->snd_nxt - tp->snd_fack) + 2594 tp->sackhint.sack_bytes_rexmit; 2595 2596 if (awnd < tp->snd_ssthresh) { 2597 tp->snd_cwnd += maxseg; 2598 if (tp->snd_cwnd > tp->snd_ssthresh) 2599 tp->snd_cwnd = tp->snd_ssthresh; 2600 } 2601 } else 2602 tp->snd_cwnd += maxseg; 2603 (void) tp->t_fb->tfb_tcp_output(tp); 2604 goto drop; 2605 } else if (tp->t_dupacks == tcprexmtthresh) { 2606 tcp_seq onxt = tp->snd_nxt; 2607 2608 /* 2609 * If we're doing sack, check to 2610 * see if we're already in sack 2611 * recovery. If we're not doing sack, 2612 * check to see if we're in newreno 2613 * recovery. 2614 */ 2615 if (tp->t_flags & TF_SACK_PERMIT) { 2616 if (IN_FASTRECOVERY(tp->t_flags)) { 2617 tp->t_dupacks = 0; 2618 break; 2619 } 2620 } else { 2621 if (SEQ_LEQ(th->th_ack, 2622 tp->snd_recover)) { 2623 tp->t_dupacks = 0; 2624 break; 2625 } 2626 } 2627 /* Congestion signal before ack. */ 2628 cc_cong_signal(tp, th, CC_NDUPACK); 2629 cc_ack_received(tp, th, nsegs, 2630 CC_DUPACK); 2631 tcp_timer_activate(tp, TT_REXMT, 0); 2632 tp->t_rtttime = 0; 2633 if (tp->t_flags & TF_SACK_PERMIT) { 2634 TCPSTAT_INC( 2635 tcps_sack_recovery_episode); 2636 tp->sack_newdata = tp->snd_nxt; 2637 tp->snd_cwnd = maxseg; 2638 (void) tp->t_fb->tfb_tcp_output(tp); 2639 goto drop; 2640 } 2641 tp->snd_nxt = th->th_ack; 2642 tp->snd_cwnd = maxseg; 2643 (void) tp->t_fb->tfb_tcp_output(tp); 2644 KASSERT(tp->snd_limited <= 2, 2645 ("%s: tp->snd_limited too big", 2646 __func__)); 2647 tp->snd_cwnd = tp->snd_ssthresh + 2648 maxseg * 2649 (tp->t_dupacks - tp->snd_limited); 2650 if (SEQ_GT(onxt, tp->snd_nxt)) 2651 tp->snd_nxt = onxt; 2652 goto drop; 2653 } else if (V_tcp_do_rfc3042) { 2654 /* 2655 * Process first and second duplicate 2656 * ACKs. Each indicates a segment 2657 * leaving the network, creating room 2658 * for more. Make sure we can send a 2659 * packet on reception of each duplicate 2660 * ACK by increasing snd_cwnd by one 2661 * segment. Restore the original 2662 * snd_cwnd after packet transmission. 2663 */ 2664 cc_ack_received(tp, th, nsegs, 2665 CC_DUPACK); 2666 uint32_t oldcwnd = tp->snd_cwnd; 2667 tcp_seq oldsndmax = tp->snd_max; 2668 u_int sent; 2669 int avail; 2670 2671 KASSERT(tp->t_dupacks == 1 || 2672 tp->t_dupacks == 2, 2673 ("%s: dupacks not 1 or 2", 2674 __func__)); 2675 if (tp->t_dupacks == 1) 2676 tp->snd_limited = 0; 2677 tp->snd_cwnd = 2678 (tp->snd_nxt - tp->snd_una) + 2679 (tp->t_dupacks - tp->snd_limited) * 2680 maxseg; 2681 /* 2682 * Only call tcp_output when there 2683 * is new data available to be sent. 2684 * Otherwise we would send pure ACKs. 2685 */ 2686 SOCKBUF_LOCK(&so->so_snd); 2687 avail = sbavail(&so->so_snd) - 2688 (tp->snd_nxt - tp->snd_una); 2689 SOCKBUF_UNLOCK(&so->so_snd); 2690 if (avail > 0) 2691 (void) tp->t_fb->tfb_tcp_output(tp); 2692 sent = tp->snd_max - oldsndmax; 2693 if (sent > maxseg) { 2694 KASSERT((tp->t_dupacks == 2 && 2695 tp->snd_limited == 0) || 2696 (sent == maxseg + 1 && 2697 tp->t_flags & TF_SENTFIN), 2698 ("%s: sent too much", 2699 __func__)); 2700 tp->snd_limited = 2; 2701 } else if (sent > 0) 2702 ++tp->snd_limited; 2703 tp->snd_cwnd = oldcwnd; 2704 goto drop; 2705 } 2706 } 2707 break; 2708 } else { 2709 /* 2710 * This ack is advancing the left edge, reset the 2711 * counter. 2712 */ 2713 tp->t_dupacks = 0; 2714 /* 2715 * If this ack also has new SACK info, increment the 2716 * counter as per rfc6675. 2717 */ 2718 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed) 2719 tp->t_dupacks++; 2720 } 2721 2722 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2723 ("%s: th_ack <= snd_una", __func__)); 2724 2725 /* 2726 * If the congestion window was inflated to account 2727 * for the other side's cached packets, retract it. 2728 */ 2729 if (IN_FASTRECOVERY(tp->t_flags)) { 2730 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2731 if (tp->t_flags & TF_SACK_PERMIT) 2732 tcp_sack_partialack(tp, th); 2733 else 2734 tcp_newreno_partial_ack(tp, th); 2735 } else 2736 cc_post_recovery(tp, th); 2737 } 2738 /* 2739 * If we reach this point, ACK is not a duplicate, 2740 * i.e., it ACKs something we sent. 2741 */ 2742 if (tp->t_flags & TF_NEEDSYN) { 2743 /* 2744 * T/TCP: Connection was half-synchronized, and our 2745 * SYN has been ACK'd (so connection is now fully 2746 * synchronized). Go to non-starred state, 2747 * increment snd_una for ACK of SYN, and check if 2748 * we can do window scaling. 2749 */ 2750 tp->t_flags &= ~TF_NEEDSYN; 2751 tp->snd_una++; 2752 /* Do window scaling? */ 2753 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2754 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2755 tp->rcv_scale = tp->request_r_scale; 2756 /* Send window already scaled. */ 2757 } 2758 } 2759 2760 process_ACK: 2761 INP_WLOCK_ASSERT(tp->t_inpcb); 2762 2763 acked = BYTES_THIS_ACK(tp, th); 2764 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2765 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2766 tp->snd_una, th->th_ack, tp, m)); 2767 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2768 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2769 2770 /* 2771 * If we just performed our first retransmit, and the ACK 2772 * arrives within our recovery window, then it was a mistake 2773 * to do the retransmit in the first place. Recover our 2774 * original cwnd and ssthresh, and proceed to transmit where 2775 * we left off. 2776 */ 2777 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2778 (int)(ticks - tp->t_badrxtwin) < 0) 2779 cc_cong_signal(tp, th, CC_RTO_ERR); 2780 2781 /* 2782 * If we have a timestamp reply, update smoothed 2783 * round trip time. If no timestamp is present but 2784 * transmit timer is running and timed sequence 2785 * number was acked, update smoothed round trip time. 2786 * Since we now have an rtt measurement, cancel the 2787 * timer backoff (cf., Phil Karn's retransmit alg.). 2788 * Recompute the initial retransmit timer. 2789 * 2790 * Some boxes send broken timestamp replies 2791 * during the SYN+ACK phase, ignore 2792 * timestamps of 0 or we could calculate a 2793 * huge RTT and blow up the retransmit timer. 2794 */ 2795 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2796 uint32_t t; 2797 2798 t = tcp_ts_getticks() - to.to_tsecr; 2799 if (!tp->t_rttlow || tp->t_rttlow > t) 2800 tp->t_rttlow = t; 2801 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2802 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2803 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2804 tp->t_rttlow = ticks - tp->t_rtttime; 2805 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2806 } 2807 2808 /* 2809 * If all outstanding data is acked, stop retransmit 2810 * timer and remember to restart (more output or persist). 2811 * If there is more data to be acked, restart retransmit 2812 * timer, using current (possibly backed-off) value. 2813 */ 2814 if (th->th_ack == tp->snd_max) { 2815 tcp_timer_activate(tp, TT_REXMT, 0); 2816 needoutput = 1; 2817 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2818 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2819 2820 /* 2821 * If no data (only SYN) was ACK'd, 2822 * skip rest of ACK processing. 2823 */ 2824 if (acked == 0) 2825 goto step6; 2826 2827 /* 2828 * Let the congestion control algorithm update congestion 2829 * control related information. This typically means increasing 2830 * the congestion window. 2831 */ 2832 cc_ack_received(tp, th, nsegs, CC_ACK); 2833 2834 SOCKBUF_LOCK(&so->so_snd); 2835 if (acked > sbavail(&so->so_snd)) { 2836 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2837 tp->snd_wnd -= sbavail(&so->so_snd); 2838 else 2839 tp->snd_wnd = 0; 2840 mfree = sbcut_locked(&so->so_snd, 2841 (int)sbavail(&so->so_snd)); 2842 ourfinisacked = 1; 2843 } else { 2844 mfree = sbcut_locked(&so->so_snd, acked); 2845 if (tp->snd_wnd >= (uint32_t) acked) 2846 tp->snd_wnd -= acked; 2847 else 2848 tp->snd_wnd = 0; 2849 ourfinisacked = 0; 2850 } 2851 /* NB: sowwakeup_locked() does an implicit unlock. */ 2852 sowwakeup_locked(so); 2853 m_freem(mfree); 2854 /* Detect una wraparound. */ 2855 if (!IN_RECOVERY(tp->t_flags) && 2856 SEQ_GT(tp->snd_una, tp->snd_recover) && 2857 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2858 tp->snd_recover = th->th_ack - 1; 2859 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2860 if (IN_RECOVERY(tp->t_flags) && 2861 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2862 EXIT_RECOVERY(tp->t_flags); 2863 } 2864 tp->snd_una = th->th_ack; 2865 if (tp->t_flags & TF_SACK_PERMIT) { 2866 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2867 tp->snd_recover = tp->snd_una; 2868 } 2869 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2870 tp->snd_nxt = tp->snd_una; 2871 2872 switch (tp->t_state) { 2873 2874 /* 2875 * In FIN_WAIT_1 STATE in addition to the processing 2876 * for the ESTABLISHED state if our FIN is now acknowledged 2877 * then enter FIN_WAIT_2. 2878 */ 2879 case TCPS_FIN_WAIT_1: 2880 if (ourfinisacked) { 2881 /* 2882 * If we can't receive any more 2883 * data, then closing user can proceed. 2884 * Starting the timer is contrary to the 2885 * specification, but if we don't get a FIN 2886 * we'll hang forever. 2887 * 2888 * XXXjl: 2889 * we should release the tp also, and use a 2890 * compressed state. 2891 */ 2892 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2893 soisdisconnected(so); 2894 tcp_timer_activate(tp, TT_2MSL, 2895 (tcp_fast_finwait2_recycle ? 2896 tcp_finwait2_timeout : 2897 TP_MAXIDLE(tp))); 2898 } 2899 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2900 } 2901 break; 2902 2903 /* 2904 * In CLOSING STATE in addition to the processing for 2905 * the ESTABLISHED state if the ACK acknowledges our FIN 2906 * then enter the TIME-WAIT state, otherwise ignore 2907 * the segment. 2908 */ 2909 case TCPS_CLOSING: 2910 if (ourfinisacked) { 2911 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2912 tcp_twstart(tp); 2913 INP_INFO_RUNLOCK(&V_tcbinfo); 2914 m_freem(m); 2915 return; 2916 } 2917 break; 2918 2919 /* 2920 * In LAST_ACK, we may still be waiting for data to drain 2921 * and/or to be acked, as well as for the ack of our FIN. 2922 * If our FIN is now acknowledged, delete the TCB, 2923 * enter the closed state and return. 2924 */ 2925 case TCPS_LAST_ACK: 2926 if (ourfinisacked) { 2927 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2928 tp = tcp_close(tp); 2929 goto drop; 2930 } 2931 break; 2932 } 2933 } 2934 2935 step6: 2936 INP_WLOCK_ASSERT(tp->t_inpcb); 2937 2938 /* 2939 * Update window information. 2940 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2941 */ 2942 if ((thflags & TH_ACK) && 2943 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2944 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2945 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2946 /* keep track of pure window updates */ 2947 if (tlen == 0 && 2948 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2949 TCPSTAT_INC(tcps_rcvwinupd); 2950 tp->snd_wnd = tiwin; 2951 tp->snd_wl1 = th->th_seq; 2952 tp->snd_wl2 = th->th_ack; 2953 if (tp->snd_wnd > tp->max_sndwnd) 2954 tp->max_sndwnd = tp->snd_wnd; 2955 needoutput = 1; 2956 } 2957 2958 /* 2959 * Process segments with URG. 2960 */ 2961 if ((thflags & TH_URG) && th->th_urp && 2962 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2963 /* 2964 * This is a kludge, but if we receive and accept 2965 * random urgent pointers, we'll crash in 2966 * soreceive. It's hard to imagine someone 2967 * actually wanting to send this much urgent data. 2968 */ 2969 SOCKBUF_LOCK(&so->so_rcv); 2970 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2971 th->th_urp = 0; /* XXX */ 2972 thflags &= ~TH_URG; /* XXX */ 2973 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2974 goto dodata; /* XXX */ 2975 } 2976 /* 2977 * If this segment advances the known urgent pointer, 2978 * then mark the data stream. This should not happen 2979 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2980 * a FIN has been received from the remote side. 2981 * In these states we ignore the URG. 2982 * 2983 * According to RFC961 (Assigned Protocols), 2984 * the urgent pointer points to the last octet 2985 * of urgent data. We continue, however, 2986 * to consider it to indicate the first octet 2987 * of data past the urgent section as the original 2988 * spec states (in one of two places). 2989 */ 2990 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2991 tp->rcv_up = th->th_seq + th->th_urp; 2992 so->so_oobmark = sbavail(&so->so_rcv) + 2993 (tp->rcv_up - tp->rcv_nxt) - 1; 2994 if (so->so_oobmark == 0) 2995 so->so_rcv.sb_state |= SBS_RCVATMARK; 2996 sohasoutofband(so); 2997 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2998 } 2999 SOCKBUF_UNLOCK(&so->so_rcv); 3000 /* 3001 * Remove out of band data so doesn't get presented to user. 3002 * This can happen independent of advancing the URG pointer, 3003 * but if two URG's are pending at once, some out-of-band 3004 * data may creep in... ick. 3005 */ 3006 if (th->th_urp <= (uint32_t)tlen && 3007 !(so->so_options & SO_OOBINLINE)) { 3008 /* hdr drop is delayed */ 3009 tcp_pulloutofband(so, th, m, drop_hdrlen); 3010 } 3011 } else { 3012 /* 3013 * If no out of band data is expected, 3014 * pull receive urgent pointer along 3015 * with the receive window. 3016 */ 3017 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3018 tp->rcv_up = tp->rcv_nxt; 3019 } 3020 dodata: /* XXX */ 3021 INP_WLOCK_ASSERT(tp->t_inpcb); 3022 3023 /* 3024 * Process the segment text, merging it into the TCP sequencing queue, 3025 * and arranging for acknowledgment of receipt if necessary. 3026 * This process logically involves adjusting tp->rcv_wnd as data 3027 * is presented to the user (this happens in tcp_usrreq.c, 3028 * case PRU_RCVD). If a FIN has already been received on this 3029 * connection then we just ignore the text. 3030 */ 3031 #ifdef TCP_RFC7413 3032 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3033 IS_FASTOPEN(tp->t_flags)); 3034 #else 3035 #define tfo_syn (false) 3036 #endif 3037 if ((tlen || (thflags & TH_FIN) || tfo_syn) && 3038 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3039 tcp_seq save_start = th->th_seq; 3040 m_adj(m, drop_hdrlen); /* delayed header drop */ 3041 /* 3042 * Insert segment which includes th into TCP reassembly queue 3043 * with control block tp. Set thflags to whether reassembly now 3044 * includes a segment with FIN. This handles the common case 3045 * inline (segment is the next to be received on an established 3046 * connection, and the queue is empty), avoiding linkage into 3047 * and removal from the queue and repetition of various 3048 * conversions. 3049 * Set DELACK for segments received in order, but ack 3050 * immediately when segments are out of order (so 3051 * fast retransmit can work). 3052 */ 3053 if (th->th_seq == tp->rcv_nxt && 3054 LIST_EMPTY(&tp->t_segq) && 3055 (TCPS_HAVEESTABLISHED(tp->t_state) || 3056 tfo_syn)) { 3057 if (DELAY_ACK(tp, tlen) || tfo_syn) 3058 tp->t_flags |= TF_DELACK; 3059 else 3060 tp->t_flags |= TF_ACKNOW; 3061 tp->rcv_nxt += tlen; 3062 thflags = th->th_flags & TH_FIN; 3063 TCPSTAT_INC(tcps_rcvpack); 3064 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3065 SOCKBUF_LOCK(&so->so_rcv); 3066 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3067 m_freem(m); 3068 else 3069 sbappendstream_locked(&so->so_rcv, m, 0); 3070 /* NB: sorwakeup_locked() does an implicit unlock. */ 3071 sorwakeup_locked(so); 3072 } else { 3073 /* 3074 * XXX: Due to the header drop above "th" is 3075 * theoretically invalid by now. Fortunately 3076 * m_adj() doesn't actually frees any mbufs 3077 * when trimming from the head. 3078 */ 3079 thflags = tcp_reass(tp, th, &tlen, m); 3080 tp->t_flags |= TF_ACKNOW; 3081 } 3082 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 3083 tcp_update_sack_list(tp, save_start, save_start + tlen); 3084 #if 0 3085 /* 3086 * Note the amount of data that peer has sent into 3087 * our window, in order to estimate the sender's 3088 * buffer size. 3089 * XXX: Unused. 3090 */ 3091 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3092 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3093 else 3094 len = so->so_rcv.sb_hiwat; 3095 #endif 3096 } else { 3097 m_freem(m); 3098 thflags &= ~TH_FIN; 3099 } 3100 3101 /* 3102 * If FIN is received ACK the FIN and let the user know 3103 * that the connection is closing. 3104 */ 3105 if (thflags & TH_FIN) { 3106 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3107 socantrcvmore(so); 3108 /* 3109 * If connection is half-synchronized 3110 * (ie NEEDSYN flag on) then delay ACK, 3111 * so it may be piggybacked when SYN is sent. 3112 * Otherwise, since we received a FIN then no 3113 * more input can be expected, send ACK now. 3114 */ 3115 if (tp->t_flags & TF_NEEDSYN) 3116 tp->t_flags |= TF_DELACK; 3117 else 3118 tp->t_flags |= TF_ACKNOW; 3119 tp->rcv_nxt++; 3120 } 3121 switch (tp->t_state) { 3122 3123 /* 3124 * In SYN_RECEIVED and ESTABLISHED STATES 3125 * enter the CLOSE_WAIT state. 3126 */ 3127 case TCPS_SYN_RECEIVED: 3128 tp->t_starttime = ticks; 3129 /* FALLTHROUGH */ 3130 case TCPS_ESTABLISHED: 3131 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3132 break; 3133 3134 /* 3135 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3136 * enter the CLOSING state. 3137 */ 3138 case TCPS_FIN_WAIT_1: 3139 tcp_state_change(tp, TCPS_CLOSING); 3140 break; 3141 3142 /* 3143 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3144 * starting the time-wait timer, turning off the other 3145 * standard timers. 3146 */ 3147 case TCPS_FIN_WAIT_2: 3148 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 3149 KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata " 3150 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 3151 ti_locked)); 3152 3153 tcp_twstart(tp); 3154 INP_INFO_RUNLOCK(&V_tcbinfo); 3155 return; 3156 } 3157 } 3158 if (ti_locked == TI_RLOCKED) 3159 INP_INFO_RUNLOCK(&V_tcbinfo); 3160 ti_locked = TI_UNLOCKED; 3161 3162 #ifdef TCPDEBUG 3163 if (so->so_options & SO_DEBUG) 3164 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3165 &tcp_savetcp, 0); 3166 #endif 3167 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3168 3169 /* 3170 * Return any desired output. 3171 */ 3172 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3173 (void) tp->t_fb->tfb_tcp_output(tp); 3174 3175 check_delack: 3176 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3177 __func__, ti_locked)); 3178 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3179 INP_WLOCK_ASSERT(tp->t_inpcb); 3180 3181 if (tp->t_flags & TF_DELACK) { 3182 tp->t_flags &= ~TF_DELACK; 3183 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3184 } 3185 INP_WUNLOCK(tp->t_inpcb); 3186 return; 3187 3188 dropafterack: 3189 /* 3190 * Generate an ACK dropping incoming segment if it occupies 3191 * sequence space, where the ACK reflects our state. 3192 * 3193 * We can now skip the test for the RST flag since all 3194 * paths to this code happen after packets containing 3195 * RST have been dropped. 3196 * 3197 * In the SYN-RECEIVED state, don't send an ACK unless the 3198 * segment we received passes the SYN-RECEIVED ACK test. 3199 * If it fails send a RST. This breaks the loop in the 3200 * "LAND" DoS attack, and also prevents an ACK storm 3201 * between two listening ports that have been sent forged 3202 * SYN segments, each with the source address of the other. 3203 */ 3204 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3205 (SEQ_GT(tp->snd_una, th->th_ack) || 3206 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3207 rstreason = BANDLIM_RST_OPENPORT; 3208 goto dropwithreset; 3209 } 3210 #ifdef TCPDEBUG 3211 if (so->so_options & SO_DEBUG) 3212 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3213 &tcp_savetcp, 0); 3214 #endif 3215 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3216 if (ti_locked == TI_RLOCKED) 3217 INP_INFO_RUNLOCK(&V_tcbinfo); 3218 ti_locked = TI_UNLOCKED; 3219 3220 tp->t_flags |= TF_ACKNOW; 3221 (void) tp->t_fb->tfb_tcp_output(tp); 3222 INP_WUNLOCK(tp->t_inpcb); 3223 m_freem(m); 3224 return; 3225 3226 dropwithreset: 3227 if (ti_locked == TI_RLOCKED) 3228 INP_INFO_RUNLOCK(&V_tcbinfo); 3229 ti_locked = TI_UNLOCKED; 3230 3231 if (tp != NULL) { 3232 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3233 INP_WUNLOCK(tp->t_inpcb); 3234 } else 3235 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3236 return; 3237 3238 drop: 3239 if (ti_locked == TI_RLOCKED) { 3240 INP_INFO_RUNLOCK(&V_tcbinfo); 3241 ti_locked = TI_UNLOCKED; 3242 } 3243 #ifdef INVARIANTS 3244 else 3245 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3246 #endif 3247 3248 /* 3249 * Drop space held by incoming segment and return. 3250 */ 3251 #ifdef TCPDEBUG 3252 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3253 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3254 &tcp_savetcp, 0); 3255 #endif 3256 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3257 if (tp != NULL) 3258 INP_WUNLOCK(tp->t_inpcb); 3259 m_freem(m); 3260 #ifndef TCP_RFC7413 3261 #undef tfo_syn 3262 #endif 3263 } 3264 3265 /* 3266 * Issue RST and make ACK acceptable to originator of segment. 3267 * The mbuf must still include the original packet header. 3268 * tp may be NULL. 3269 */ 3270 void 3271 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3272 int tlen, int rstreason) 3273 { 3274 #ifdef INET 3275 struct ip *ip; 3276 #endif 3277 #ifdef INET6 3278 struct ip6_hdr *ip6; 3279 #endif 3280 3281 if (tp != NULL) { 3282 INP_WLOCK_ASSERT(tp->t_inpcb); 3283 } 3284 3285 /* Don't bother if destination was broadcast/multicast. */ 3286 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3287 goto drop; 3288 #ifdef INET6 3289 if (mtod(m, struct ip *)->ip_v == 6) { 3290 ip6 = mtod(m, struct ip6_hdr *); 3291 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3292 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3293 goto drop; 3294 /* IPv6 anycast check is done at tcp6_input() */ 3295 } 3296 #endif 3297 #if defined(INET) && defined(INET6) 3298 else 3299 #endif 3300 #ifdef INET 3301 { 3302 ip = mtod(m, struct ip *); 3303 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3304 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3305 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3306 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3307 goto drop; 3308 } 3309 #endif 3310 3311 /* Perform bandwidth limiting. */ 3312 if (badport_bandlim(rstreason) < 0) 3313 goto drop; 3314 3315 /* tcp_respond consumes the mbuf chain. */ 3316 if (th->th_flags & TH_ACK) { 3317 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3318 th->th_ack, TH_RST); 3319 } else { 3320 if (th->th_flags & TH_SYN) 3321 tlen++; 3322 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3323 (tcp_seq)0, TH_RST|TH_ACK); 3324 } 3325 return; 3326 drop: 3327 m_freem(m); 3328 } 3329 3330 /* 3331 * Parse TCP options and place in tcpopt. 3332 */ 3333 void 3334 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3335 { 3336 int opt, optlen; 3337 3338 to->to_flags = 0; 3339 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3340 opt = cp[0]; 3341 if (opt == TCPOPT_EOL) 3342 break; 3343 if (opt == TCPOPT_NOP) 3344 optlen = 1; 3345 else { 3346 if (cnt < 2) 3347 break; 3348 optlen = cp[1]; 3349 if (optlen < 2 || optlen > cnt) 3350 break; 3351 } 3352 switch (opt) { 3353 case TCPOPT_MAXSEG: 3354 if (optlen != TCPOLEN_MAXSEG) 3355 continue; 3356 if (!(flags & TO_SYN)) 3357 continue; 3358 to->to_flags |= TOF_MSS; 3359 bcopy((char *)cp + 2, 3360 (char *)&to->to_mss, sizeof(to->to_mss)); 3361 to->to_mss = ntohs(to->to_mss); 3362 break; 3363 case TCPOPT_WINDOW: 3364 if (optlen != TCPOLEN_WINDOW) 3365 continue; 3366 if (!(flags & TO_SYN)) 3367 continue; 3368 to->to_flags |= TOF_SCALE; 3369 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3370 break; 3371 case TCPOPT_TIMESTAMP: 3372 if (optlen != TCPOLEN_TIMESTAMP) 3373 continue; 3374 to->to_flags |= TOF_TS; 3375 bcopy((char *)cp + 2, 3376 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3377 to->to_tsval = ntohl(to->to_tsval); 3378 bcopy((char *)cp + 6, 3379 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3380 to->to_tsecr = ntohl(to->to_tsecr); 3381 break; 3382 #ifdef TCP_SIGNATURE 3383 /* 3384 * XXX In order to reply to a host which has set the 3385 * TCP_SIGNATURE option in its initial SYN, we have to 3386 * record the fact that the option was observed here 3387 * for the syncache code to perform the correct response. 3388 */ 3389 case TCPOPT_SIGNATURE: 3390 if (optlen != TCPOLEN_SIGNATURE) 3391 continue; 3392 to->to_flags |= TOF_SIGNATURE; 3393 to->to_signature = cp + 2; 3394 break; 3395 #endif 3396 case TCPOPT_SACK_PERMITTED: 3397 if (optlen != TCPOLEN_SACK_PERMITTED) 3398 continue; 3399 if (!(flags & TO_SYN)) 3400 continue; 3401 if (!V_tcp_do_sack) 3402 continue; 3403 to->to_flags |= TOF_SACKPERM; 3404 break; 3405 case TCPOPT_SACK: 3406 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3407 continue; 3408 if (flags & TO_SYN) 3409 continue; 3410 to->to_flags |= TOF_SACK; 3411 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3412 to->to_sacks = cp + 2; 3413 TCPSTAT_INC(tcps_sack_rcv_blocks); 3414 break; 3415 #ifdef TCP_RFC7413 3416 case TCPOPT_FAST_OPEN: 3417 if ((optlen != TCPOLEN_FAST_OPEN_EMPTY) && 3418 (optlen < TCPOLEN_FAST_OPEN_MIN) && 3419 (optlen > TCPOLEN_FAST_OPEN_MAX)) 3420 continue; 3421 if (!(flags & TO_SYN)) 3422 continue; 3423 if (!V_tcp_fastopen_enabled) 3424 continue; 3425 to->to_flags |= TOF_FASTOPEN; 3426 to->to_tfo_len = optlen - 2; 3427 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3428 break; 3429 #endif 3430 default: 3431 continue; 3432 } 3433 } 3434 } 3435 3436 /* 3437 * Pull out of band byte out of a segment so 3438 * it doesn't appear in the user's data queue. 3439 * It is still reflected in the segment length for 3440 * sequencing purposes. 3441 */ 3442 void 3443 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3444 int off) 3445 { 3446 int cnt = off + th->th_urp - 1; 3447 3448 while (cnt >= 0) { 3449 if (m->m_len > cnt) { 3450 char *cp = mtod(m, caddr_t) + cnt; 3451 struct tcpcb *tp = sototcpcb(so); 3452 3453 INP_WLOCK_ASSERT(tp->t_inpcb); 3454 3455 tp->t_iobc = *cp; 3456 tp->t_oobflags |= TCPOOB_HAVEDATA; 3457 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3458 m->m_len--; 3459 if (m->m_flags & M_PKTHDR) 3460 m->m_pkthdr.len--; 3461 return; 3462 } 3463 cnt -= m->m_len; 3464 m = m->m_next; 3465 if (m == NULL) 3466 break; 3467 } 3468 panic("tcp_pulloutofband"); 3469 } 3470 3471 /* 3472 * Collect new round-trip time estimate 3473 * and update averages and current timeout. 3474 */ 3475 void 3476 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3477 { 3478 int delta; 3479 3480 INP_WLOCK_ASSERT(tp->t_inpcb); 3481 3482 TCPSTAT_INC(tcps_rttupdated); 3483 tp->t_rttupdated++; 3484 if (tp->t_srtt != 0) { 3485 /* 3486 * srtt is stored as fixed point with 5 bits after the 3487 * binary point (i.e., scaled by 8). The following magic 3488 * is equivalent to the smoothing algorithm in rfc793 with 3489 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3490 * point). Adjust rtt to origin 0. 3491 */ 3492 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3493 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3494 3495 if ((tp->t_srtt += delta) <= 0) 3496 tp->t_srtt = 1; 3497 3498 /* 3499 * We accumulate a smoothed rtt variance (actually, a 3500 * smoothed mean difference), then set the retransmit 3501 * timer to smoothed rtt + 4 times the smoothed variance. 3502 * rttvar is stored as fixed point with 4 bits after the 3503 * binary point (scaled by 16). The following is 3504 * equivalent to rfc793 smoothing with an alpha of .75 3505 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3506 * rfc793's wired-in beta. 3507 */ 3508 if (delta < 0) 3509 delta = -delta; 3510 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3511 if ((tp->t_rttvar += delta) <= 0) 3512 tp->t_rttvar = 1; 3513 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3514 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3515 } else { 3516 /* 3517 * No rtt measurement yet - use the unsmoothed rtt. 3518 * Set the variance to half the rtt (so our first 3519 * retransmit happens at 3*rtt). 3520 */ 3521 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3522 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3523 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3524 } 3525 tp->t_rtttime = 0; 3526 tp->t_rxtshift = 0; 3527 3528 /* 3529 * the retransmit should happen at rtt + 4 * rttvar. 3530 * Because of the way we do the smoothing, srtt and rttvar 3531 * will each average +1/2 tick of bias. When we compute 3532 * the retransmit timer, we want 1/2 tick of rounding and 3533 * 1 extra tick because of +-1/2 tick uncertainty in the 3534 * firing of the timer. The bias will give us exactly the 3535 * 1.5 tick we need. But, because the bias is 3536 * statistical, we have to test that we don't drop below 3537 * the minimum feasible timer (which is 2 ticks). 3538 */ 3539 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3540 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3541 3542 /* 3543 * We received an ack for a packet that wasn't retransmitted; 3544 * it is probably safe to discard any error indications we've 3545 * received recently. This isn't quite right, but close enough 3546 * for now (a route might have failed after we sent a segment, 3547 * and the return path might not be symmetrical). 3548 */ 3549 tp->t_softerror = 0; 3550 } 3551 3552 /* 3553 * Determine a reasonable value for maxseg size. 3554 * If the route is known, check route for mtu. 3555 * If none, use an mss that can be handled on the outgoing interface 3556 * without forcing IP to fragment. If no route is found, route has no mtu, 3557 * or the destination isn't local, use a default, hopefully conservative 3558 * size (usually 512 or the default IP max size, but no more than the mtu 3559 * of the interface), as we can't discover anything about intervening 3560 * gateways or networks. We also initialize the congestion/slow start 3561 * window to be a single segment if the destination isn't local. 3562 * While looking at the routing entry, we also initialize other path-dependent 3563 * parameters from pre-set or cached values in the routing entry. 3564 * 3565 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3566 * IP options, e.g. IPSEC data, since length of this data may vary, and 3567 * thus it is calculated for every segment separately in tcp_output(). 3568 * 3569 * NOTE that this routine is only called when we process an incoming 3570 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3571 * settings are handled in tcp_mssopt(). 3572 */ 3573 void 3574 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3575 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3576 { 3577 int mss = 0; 3578 uint32_t maxmtu = 0; 3579 struct inpcb *inp = tp->t_inpcb; 3580 struct hc_metrics_lite metrics; 3581 #ifdef INET6 3582 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3583 size_t min_protoh = isipv6 ? 3584 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3585 sizeof (struct tcpiphdr); 3586 #else 3587 const size_t min_protoh = sizeof(struct tcpiphdr); 3588 #endif 3589 3590 INP_WLOCK_ASSERT(tp->t_inpcb); 3591 3592 if (mtuoffer != -1) { 3593 KASSERT(offer == -1, ("%s: conflict", __func__)); 3594 offer = mtuoffer - min_protoh; 3595 } 3596 3597 /* Initialize. */ 3598 #ifdef INET6 3599 if (isipv6) { 3600 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3601 tp->t_maxseg = V_tcp_v6mssdflt; 3602 } 3603 #endif 3604 #if defined(INET) && defined(INET6) 3605 else 3606 #endif 3607 #ifdef INET 3608 { 3609 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3610 tp->t_maxseg = V_tcp_mssdflt; 3611 } 3612 #endif 3613 3614 /* 3615 * No route to sender, stay with default mss and return. 3616 */ 3617 if (maxmtu == 0) { 3618 /* 3619 * In case we return early we need to initialize metrics 3620 * to a defined state as tcp_hc_get() would do for us 3621 * if there was no cache hit. 3622 */ 3623 if (metricptr != NULL) 3624 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3625 return; 3626 } 3627 3628 /* What have we got? */ 3629 switch (offer) { 3630 case 0: 3631 /* 3632 * Offer == 0 means that there was no MSS on the SYN 3633 * segment, in this case we use tcp_mssdflt as 3634 * already assigned to t_maxseg above. 3635 */ 3636 offer = tp->t_maxseg; 3637 break; 3638 3639 case -1: 3640 /* 3641 * Offer == -1 means that we didn't receive SYN yet. 3642 */ 3643 /* FALLTHROUGH */ 3644 3645 default: 3646 /* 3647 * Prevent DoS attack with too small MSS. Round up 3648 * to at least minmss. 3649 */ 3650 offer = max(offer, V_tcp_minmss); 3651 } 3652 3653 /* 3654 * rmx information is now retrieved from tcp_hostcache. 3655 */ 3656 tcp_hc_get(&inp->inp_inc, &metrics); 3657 if (metricptr != NULL) 3658 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3659 3660 /* 3661 * If there's a discovered mtu in tcp hostcache, use it. 3662 * Else, use the link mtu. 3663 */ 3664 if (metrics.rmx_mtu) 3665 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3666 else { 3667 #ifdef INET6 3668 if (isipv6) { 3669 mss = maxmtu - min_protoh; 3670 if (!V_path_mtu_discovery && 3671 !in6_localaddr(&inp->in6p_faddr)) 3672 mss = min(mss, V_tcp_v6mssdflt); 3673 } 3674 #endif 3675 #if defined(INET) && defined(INET6) 3676 else 3677 #endif 3678 #ifdef INET 3679 { 3680 mss = maxmtu - min_protoh; 3681 if (!V_path_mtu_discovery && 3682 !in_localaddr(inp->inp_faddr)) 3683 mss = min(mss, V_tcp_mssdflt); 3684 } 3685 #endif 3686 /* 3687 * XXX - The above conditional (mss = maxmtu - min_protoh) 3688 * probably violates the TCP spec. 3689 * The problem is that, since we don't know the 3690 * other end's MSS, we are supposed to use a conservative 3691 * default. But, if we do that, then MTU discovery will 3692 * never actually take place, because the conservative 3693 * default is much less than the MTUs typically seen 3694 * on the Internet today. For the moment, we'll sweep 3695 * this under the carpet. 3696 * 3697 * The conservative default might not actually be a problem 3698 * if the only case this occurs is when sending an initial 3699 * SYN with options and data to a host we've never talked 3700 * to before. Then, they will reply with an MSS value which 3701 * will get recorded and the new parameters should get 3702 * recomputed. For Further Study. 3703 */ 3704 } 3705 mss = min(mss, offer); 3706 3707 /* 3708 * Sanity check: make sure that maxseg will be large 3709 * enough to allow some data on segments even if the 3710 * all the option space is used (40bytes). Otherwise 3711 * funny things may happen in tcp_output. 3712 * 3713 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3714 */ 3715 mss = max(mss, 64); 3716 3717 tp->t_maxseg = mss; 3718 } 3719 3720 void 3721 tcp_mss(struct tcpcb *tp, int offer) 3722 { 3723 int mss; 3724 uint32_t bufsize; 3725 struct inpcb *inp; 3726 struct socket *so; 3727 struct hc_metrics_lite metrics; 3728 struct tcp_ifcap cap; 3729 3730 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3731 3732 bzero(&cap, sizeof(cap)); 3733 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3734 3735 mss = tp->t_maxseg; 3736 inp = tp->t_inpcb; 3737 3738 /* 3739 * If there's a pipesize, change the socket buffer to that size, 3740 * don't change if sb_hiwat is different than default (then it 3741 * has been changed on purpose with setsockopt). 3742 * Make the socket buffers an integral number of mss units; 3743 * if the mss is larger than the socket buffer, decrease the mss. 3744 */ 3745 so = inp->inp_socket; 3746 SOCKBUF_LOCK(&so->so_snd); 3747 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3748 bufsize = metrics.rmx_sendpipe; 3749 else 3750 bufsize = so->so_snd.sb_hiwat; 3751 if (bufsize < mss) 3752 mss = bufsize; 3753 else { 3754 bufsize = roundup(bufsize, mss); 3755 if (bufsize > sb_max) 3756 bufsize = sb_max; 3757 if (bufsize > so->so_snd.sb_hiwat) 3758 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3759 } 3760 SOCKBUF_UNLOCK(&so->so_snd); 3761 tp->t_maxseg = mss; 3762 3763 SOCKBUF_LOCK(&so->so_rcv); 3764 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3765 bufsize = metrics.rmx_recvpipe; 3766 else 3767 bufsize = so->so_rcv.sb_hiwat; 3768 if (bufsize > mss) { 3769 bufsize = roundup(bufsize, mss); 3770 if (bufsize > sb_max) 3771 bufsize = sb_max; 3772 if (bufsize > so->so_rcv.sb_hiwat) 3773 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3774 } 3775 SOCKBUF_UNLOCK(&so->so_rcv); 3776 3777 /* Check the interface for TSO capabilities. */ 3778 if (cap.ifcap & CSUM_TSO) { 3779 tp->t_flags |= TF_TSO; 3780 tp->t_tsomax = cap.tsomax; 3781 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3782 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3783 } 3784 } 3785 3786 /* 3787 * Determine the MSS option to send on an outgoing SYN. 3788 */ 3789 int 3790 tcp_mssopt(struct in_conninfo *inc) 3791 { 3792 int mss = 0; 3793 uint32_t thcmtu = 0; 3794 uint32_t maxmtu = 0; 3795 size_t min_protoh; 3796 3797 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3798 3799 #ifdef INET6 3800 if (inc->inc_flags & INC_ISIPV6) { 3801 mss = V_tcp_v6mssdflt; 3802 maxmtu = tcp_maxmtu6(inc, NULL); 3803 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3804 } 3805 #endif 3806 #if defined(INET) && defined(INET6) 3807 else 3808 #endif 3809 #ifdef INET 3810 { 3811 mss = V_tcp_mssdflt; 3812 maxmtu = tcp_maxmtu(inc, NULL); 3813 min_protoh = sizeof(struct tcpiphdr); 3814 } 3815 #endif 3816 #if defined(INET6) || defined(INET) 3817 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3818 #endif 3819 3820 if (maxmtu && thcmtu) 3821 mss = min(maxmtu, thcmtu) - min_protoh; 3822 else if (maxmtu || thcmtu) 3823 mss = max(maxmtu, thcmtu) - min_protoh; 3824 3825 return (mss); 3826 } 3827 3828 3829 /* 3830 * On a partial ack arrives, force the retransmission of the 3831 * next unacknowledged segment. Do not clear tp->t_dupacks. 3832 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3833 * be started again. 3834 */ 3835 void 3836 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3837 { 3838 tcp_seq onxt = tp->snd_nxt; 3839 uint32_t ocwnd = tp->snd_cwnd; 3840 u_int maxseg = tcp_maxseg(tp); 3841 3842 INP_WLOCK_ASSERT(tp->t_inpcb); 3843 3844 tcp_timer_activate(tp, TT_REXMT, 0); 3845 tp->t_rtttime = 0; 3846 tp->snd_nxt = th->th_ack; 3847 /* 3848 * Set snd_cwnd to one segment beyond acknowledged offset. 3849 * (tp->snd_una has not yet been updated when this function is called.) 3850 */ 3851 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3852 tp->t_flags |= TF_ACKNOW; 3853 (void) tp->t_fb->tfb_tcp_output(tp); 3854 tp->snd_cwnd = ocwnd; 3855 if (SEQ_GT(onxt, tp->snd_nxt)) 3856 tp->snd_nxt = onxt; 3857 /* 3858 * Partial window deflation. Relies on fact that tp->snd_una 3859 * not updated yet. 3860 */ 3861 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3862 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3863 else 3864 tp->snd_cwnd = 0; 3865 tp->snd_cwnd += maxseg; 3866 } 3867 3868 int 3869 tcp_compute_pipe(struct tcpcb *tp) 3870 { 3871 return (tp->snd_max - tp->snd_una + 3872 tp->sackhint.sack_bytes_rexmit - 3873 tp->sackhint.sacked_bytes); 3874 } 3875