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 #include <sys/hhook.h> 61 #include <sys/malloc.h> 62 #include <sys/mbuf.h> 63 #include <sys/proc.h> /* for proc0 declaration */ 64 #include <sys/protosw.h> 65 #include <sys/sdt.h> 66 #include <sys/signalvar.h> 67 #include <sys/socket.h> 68 #include <sys/socketvar.h> 69 #include <sys/sysctl.h> 70 #include <sys/syslog.h> 71 #include <sys/systm.h> 72 73 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 74 75 #include <vm/uma.h> 76 77 #include <net/if.h> 78 #include <net/if_var.h> 79 #include <net/route.h> 80 #include <net/vnet.h> 81 82 #define TCPSTATES /* for logging */ 83 84 #include <netinet/in.h> 85 #include <netinet/in_kdtrace.h> 86 #include <netinet/in_pcb.h> 87 #include <netinet/in_systm.h> 88 #include <netinet/ip.h> 89 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 90 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 91 #include <netinet/ip_var.h> 92 #include <netinet/ip_options.h> 93 #include <netinet/ip6.h> 94 #include <netinet/icmp6.h> 95 #include <netinet6/in6_pcb.h> 96 #include <netinet6/in6_var.h> 97 #include <netinet6/ip6_var.h> 98 #include <netinet6/nd6.h> 99 #ifdef TCP_RFC7413 100 #include <netinet/tcp_fastopen.h> 101 #endif 102 #include <netinet/tcp.h> 103 #include <netinet/tcp_fsm.h> 104 #include <netinet/tcp_seq.h> 105 #include <netinet/tcp_timer.h> 106 #include <netinet/tcp_var.h> 107 #include <netinet6/tcp6_var.h> 108 #include <netinet/tcpip.h> 109 #include <netinet/cc/cc.h> 110 #ifdef TCPPCAP 111 #include <netinet/tcp_pcap.h> 112 #endif 113 #include <netinet/tcp_syncache.h> 114 #ifdef TCPDEBUG 115 #include <netinet/tcp_debug.h> 116 #endif /* TCPDEBUG */ 117 #ifdef TCP_OFFLOAD 118 #include <netinet/tcp_offload.h> 119 #endif 120 121 #ifdef IPSEC 122 #include <netipsec/ipsec.h> 123 #include <netipsec/ipsec6.h> 124 #endif /*IPSEC*/ 125 126 #include <machine/in_cksum.h> 127 128 #include <security/mac/mac_framework.h> 129 130 const int tcprexmtthresh = 3; 131 132 int tcp_log_in_vain = 0; 133 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW, 134 &tcp_log_in_vain, 0, 135 "Log all incoming TCP segments to closed ports"); 136 137 VNET_DEFINE(int, blackhole) = 0; 138 #define V_blackhole VNET(blackhole) 139 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 140 &VNET_NAME(blackhole), 0, 141 "Do not send RST on segments to closed ports"); 142 143 VNET_DEFINE(int, tcp_delack_enabled) = 1; 144 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 145 &VNET_NAME(tcp_delack_enabled), 0, 146 "Delay ACK to try and piggyback it onto a data packet"); 147 148 VNET_DEFINE(int, drop_synfin) = 0; 149 #define V_drop_synfin VNET(drop_synfin) 150 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 151 &VNET_NAME(drop_synfin), 0, 152 "Drop TCP packets with SYN+FIN set"); 153 154 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 155 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 156 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 157 "Use calculated pipe/in-flight bytes per RFC 6675"); 158 159 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 160 #define V_tcp_do_rfc3042 VNET(tcp_do_rfc3042) 161 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 162 &VNET_NAME(tcp_do_rfc3042), 0, 163 "Enable RFC 3042 (Limited Transmit)"); 164 165 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 166 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 167 &VNET_NAME(tcp_do_rfc3390), 0, 168 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 169 170 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 171 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 172 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 173 "Slow-start flight size (initial congestion window) in number of segments"); 174 175 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 176 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 177 &VNET_NAME(tcp_do_rfc3465), 0, 178 "Enable RFC 3465 (Appropriate Byte Counting)"); 179 180 VNET_DEFINE(int, tcp_abc_l_var) = 2; 181 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 182 &VNET_NAME(tcp_abc_l_var), 2, 183 "Cap the max cwnd increment during slow-start to this number of segments"); 184 185 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN"); 186 187 VNET_DEFINE(int, tcp_do_ecn) = 2; 188 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 189 &VNET_NAME(tcp_do_ecn), 0, 190 "TCP ECN support"); 191 192 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 193 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 194 &VNET_NAME(tcp_ecn_maxretries), 0, 195 "Max retries before giving up on ECN"); 196 197 VNET_DEFINE(int, tcp_insecure_syn) = 0; 198 #define V_tcp_insecure_syn VNET(tcp_insecure_syn) 199 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 200 &VNET_NAME(tcp_insecure_syn), 0, 201 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 202 203 VNET_DEFINE(int, tcp_insecure_rst) = 0; 204 #define V_tcp_insecure_rst VNET(tcp_insecure_rst) 205 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 206 &VNET_NAME(tcp_insecure_rst), 0, 207 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 208 209 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 210 #define V_tcp_recvspace VNET(tcp_recvspace) 211 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 212 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 213 214 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 215 #define V_tcp_do_autorcvbuf VNET(tcp_do_autorcvbuf) 216 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 217 &VNET_NAME(tcp_do_autorcvbuf), 0, 218 "Enable automatic receive buffer sizing"); 219 220 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024; 221 #define V_tcp_autorcvbuf_inc VNET(tcp_autorcvbuf_inc) 222 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW, 223 &VNET_NAME(tcp_autorcvbuf_inc), 0, 224 "Incrementor step size of automatic receive buffer"); 225 226 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 227 #define V_tcp_autorcvbuf_max VNET(tcp_autorcvbuf_max) 228 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 229 &VNET_NAME(tcp_autorcvbuf_max), 0, 230 "Max size of automatic receive buffer"); 231 232 VNET_DEFINE(struct inpcbhead, tcb); 233 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 234 VNET_DEFINE(struct inpcbinfo, tcbinfo); 235 236 /* 237 * TCP statistics are stored in an array of counter(9)s, which size matches 238 * size of struct tcpstat. TCP running connection count is a regular array. 239 */ 240 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 241 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 242 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 243 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 244 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 245 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 246 "TCP connection counts by TCP state"); 247 248 static void 249 tcp_vnet_init(const void *unused) 250 { 251 252 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 253 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 254 } 255 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 256 tcp_vnet_init, NULL); 257 258 #ifdef VIMAGE 259 static void 260 tcp_vnet_uninit(const void *unused) 261 { 262 263 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 264 VNET_PCPUSTAT_FREE(tcpstat); 265 } 266 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 267 tcp_vnet_uninit, NULL); 268 #endif /* VIMAGE */ 269 270 /* 271 * Kernel module interface for updating tcpstat. The argument is an index 272 * into tcpstat treated as an array. 273 */ 274 void 275 kmod_tcpstat_inc(int statnum) 276 { 277 278 counter_u64_add(VNET(tcpstat)[statnum], 1); 279 } 280 281 /* 282 * Wrapper for the TCP established input helper hook. 283 */ 284 void 285 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 286 { 287 struct tcp_hhook_data hhook_data; 288 289 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 290 hhook_data.tp = tp; 291 hhook_data.th = th; 292 hhook_data.to = to; 293 294 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 295 tp->osd); 296 } 297 } 298 299 /* 300 * CC wrapper hook functions 301 */ 302 void 303 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type) 304 { 305 INP_WLOCK_ASSERT(tp->t_inpcb); 306 307 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 308 if (tp->snd_cwnd <= tp->snd_wnd) 309 tp->ccv->flags |= CCF_CWND_LIMITED; 310 else 311 tp->ccv->flags &= ~CCF_CWND_LIMITED; 312 313 if (type == CC_ACK) { 314 if (tp->snd_cwnd > tp->snd_ssthresh) { 315 tp->t_bytes_acked += min(tp->ccv->bytes_this_ack, 316 V_tcp_abc_l_var * tcp_maxseg(tp)); 317 if (tp->t_bytes_acked >= tp->snd_cwnd) { 318 tp->t_bytes_acked -= tp->snd_cwnd; 319 tp->ccv->flags |= CCF_ABC_SENTAWND; 320 } 321 } else { 322 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 323 tp->t_bytes_acked = 0; 324 } 325 } 326 327 if (CC_ALGO(tp)->ack_received != NULL) { 328 /* XXXLAS: Find a way to live without this */ 329 tp->ccv->curack = th->th_ack; 330 CC_ALGO(tp)->ack_received(tp->ccv, type); 331 } 332 } 333 334 void 335 cc_conn_init(struct tcpcb *tp) 336 { 337 struct hc_metrics_lite metrics; 338 struct inpcb *inp = tp->t_inpcb; 339 u_int maxseg; 340 int rtt; 341 342 INP_WLOCK_ASSERT(tp->t_inpcb); 343 344 tcp_hc_get(&inp->inp_inc, &metrics); 345 maxseg = tcp_maxseg(tp); 346 347 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 348 tp->t_srtt = rtt; 349 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 350 TCPSTAT_INC(tcps_usedrtt); 351 if (metrics.rmx_rttvar) { 352 tp->t_rttvar = metrics.rmx_rttvar; 353 TCPSTAT_INC(tcps_usedrttvar); 354 } else { 355 /* default variation is +- 1 rtt */ 356 tp->t_rttvar = 357 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 358 } 359 TCPT_RANGESET(tp->t_rxtcur, 360 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 361 tp->t_rttmin, TCPTV_REXMTMAX); 362 } 363 if (metrics.rmx_ssthresh) { 364 /* 365 * There's some sort of gateway or interface 366 * buffer limit on the path. Use this to set 367 * the slow start threshold, but set the 368 * threshold to no less than 2*mss. 369 */ 370 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 371 TCPSTAT_INC(tcps_usedssthresh); 372 } 373 374 /* 375 * Set the initial slow-start flight size. 376 * 377 * RFC5681 Section 3.1 specifies the default conservative values. 378 * RFC3390 specifies slightly more aggressive values. 379 * RFC6928 increases it to ten segments. 380 * Support for user specified value for initial flight size. 381 * 382 * If a SYN or SYN/ACK was lost and retransmitted, we have to 383 * reduce the initial CWND to one segment as congestion is likely 384 * requiring us to be cautious. 385 */ 386 if (tp->snd_cwnd == 1) 387 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 388 else if (V_tcp_initcwnd_segments) 389 tp->snd_cwnd = min(V_tcp_initcwnd_segments * maxseg, 390 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 391 else if (V_tcp_do_rfc3390) 392 tp->snd_cwnd = min(4 * maxseg, max(2 * maxseg, 4380)); 393 else { 394 /* Per RFC5681 Section 3.1 */ 395 if (maxseg > 2190) 396 tp->snd_cwnd = 2 * maxseg; 397 else if (maxseg > 1095) 398 tp->snd_cwnd = 3 * maxseg; 399 else 400 tp->snd_cwnd = 4 * maxseg; 401 } 402 403 if (CC_ALGO(tp)->conn_init != NULL) 404 CC_ALGO(tp)->conn_init(tp->ccv); 405 } 406 407 void inline 408 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 409 { 410 u_int maxseg; 411 412 INP_WLOCK_ASSERT(tp->t_inpcb); 413 414 switch(type) { 415 case CC_NDUPACK: 416 if (!IN_FASTRECOVERY(tp->t_flags)) { 417 tp->snd_recover = tp->snd_max; 418 if (tp->t_flags & TF_ECN_PERMIT) 419 tp->t_flags |= TF_ECN_SND_CWR; 420 } 421 break; 422 case CC_ECN: 423 if (!IN_CONGRECOVERY(tp->t_flags)) { 424 TCPSTAT_INC(tcps_ecn_rcwnd); 425 tp->snd_recover = tp->snd_max; 426 if (tp->t_flags & TF_ECN_PERMIT) 427 tp->t_flags |= TF_ECN_SND_CWR; 428 } 429 break; 430 case CC_RTO: 431 maxseg = tcp_maxseg(tp); 432 tp->t_dupacks = 0; 433 tp->t_bytes_acked = 0; 434 EXIT_RECOVERY(tp->t_flags); 435 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 436 maxseg) * maxseg; 437 tp->snd_cwnd = maxseg; 438 break; 439 case CC_RTO_ERR: 440 TCPSTAT_INC(tcps_sndrexmitbad); 441 /* RTO was unnecessary, so reset everything. */ 442 tp->snd_cwnd = tp->snd_cwnd_prev; 443 tp->snd_ssthresh = tp->snd_ssthresh_prev; 444 tp->snd_recover = tp->snd_recover_prev; 445 if (tp->t_flags & TF_WASFRECOVERY) 446 ENTER_FASTRECOVERY(tp->t_flags); 447 if (tp->t_flags & TF_WASCRECOVERY) 448 ENTER_CONGRECOVERY(tp->t_flags); 449 tp->snd_nxt = tp->snd_max; 450 tp->t_flags &= ~TF_PREVVALID; 451 tp->t_badrxtwin = 0; 452 break; 453 } 454 455 if (CC_ALGO(tp)->cong_signal != NULL) { 456 if (th != NULL) 457 tp->ccv->curack = th->th_ack; 458 CC_ALGO(tp)->cong_signal(tp->ccv, type); 459 } 460 } 461 462 void inline 463 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 464 { 465 INP_WLOCK_ASSERT(tp->t_inpcb); 466 467 /* XXXLAS: KASSERT that we're in recovery? */ 468 469 if (CC_ALGO(tp)->post_recovery != NULL) { 470 tp->ccv->curack = th->th_ack; 471 CC_ALGO(tp)->post_recovery(tp->ccv); 472 } 473 /* XXXLAS: EXIT_RECOVERY ? */ 474 tp->t_bytes_acked = 0; 475 } 476 477 #ifdef TCP_SIGNATURE 478 static inline int 479 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen, 480 struct tcpopt *to, struct tcphdr *th, u_int tcpbflag) 481 { 482 int ret; 483 484 tcp_fields_to_net(th); 485 ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag); 486 tcp_fields_to_host(th); 487 return (ret); 488 } 489 #endif 490 491 /* 492 * Indicate whether this ack should be delayed. We can delay the ack if 493 * following conditions are met: 494 * - There is no delayed ack timer in progress. 495 * - Our last ack wasn't a 0-sized window. We never want to delay 496 * the ack that opens up a 0-sized window. 497 * - LRO wasn't used for this segment. We make sure by checking that the 498 * segment size is not larger than the MSS. 499 */ 500 #define DELAY_ACK(tp, tlen) \ 501 ((!tcp_timer_active(tp, TT_DELACK) && \ 502 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 503 (tlen <= tp->t_maxseg) && \ 504 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 505 506 static void inline 507 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 508 { 509 INP_WLOCK_ASSERT(tp->t_inpcb); 510 511 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 512 switch (iptos & IPTOS_ECN_MASK) { 513 case IPTOS_ECN_CE: 514 tp->ccv->flags |= CCF_IPHDR_CE; 515 break; 516 case IPTOS_ECN_ECT0: 517 tp->ccv->flags &= ~CCF_IPHDR_CE; 518 break; 519 case IPTOS_ECN_ECT1: 520 tp->ccv->flags &= ~CCF_IPHDR_CE; 521 break; 522 } 523 524 if (th->th_flags & TH_CWR) 525 tp->ccv->flags |= CCF_TCPHDR_CWR; 526 else 527 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 528 529 if (tp->t_flags & TF_DELACK) 530 tp->ccv->flags |= CCF_DELACK; 531 else 532 tp->ccv->flags &= ~CCF_DELACK; 533 534 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 535 536 if (tp->ccv->flags & CCF_ACKNOW) 537 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 538 } 539 } 540 541 /* 542 * TCP input handling is split into multiple parts: 543 * tcp6_input is a thin wrapper around tcp_input for the extended 544 * ip6_protox[] call format in ip6_input 545 * tcp_input handles primary segment validation, inpcb lookup and 546 * SYN processing on listen sockets 547 * tcp_do_segment processes the ACK and text of the segment for 548 * establishing, established and closing connections 549 */ 550 #ifdef INET6 551 int 552 tcp6_input(struct mbuf **mp, int *offp, int proto) 553 { 554 struct mbuf *m = *mp; 555 struct in6_ifaddr *ia6; 556 struct ip6_hdr *ip6; 557 558 IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE); 559 560 /* 561 * draft-itojun-ipv6-tcp-to-anycast 562 * better place to put this in? 563 */ 564 ip6 = mtod(m, struct ip6_hdr *); 565 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 566 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 567 struct ip6_hdr *ip6; 568 569 ifa_free(&ia6->ia_ifa); 570 ip6 = mtod(m, struct ip6_hdr *); 571 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 572 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 573 return (IPPROTO_DONE); 574 } 575 if (ia6) 576 ifa_free(&ia6->ia_ifa); 577 578 return (tcp_input(mp, offp, proto)); 579 } 580 #endif /* INET6 */ 581 582 int 583 tcp_input(struct mbuf **mp, int *offp, int proto) 584 { 585 struct mbuf *m = *mp; 586 struct tcphdr *th = NULL; 587 struct ip *ip = NULL; 588 struct inpcb *inp = NULL; 589 struct tcpcb *tp = NULL; 590 struct socket *so = NULL; 591 u_char *optp = NULL; 592 int off0; 593 int optlen = 0; 594 #ifdef INET 595 int len; 596 #endif 597 int tlen = 0, off; 598 int drop_hdrlen; 599 int thflags; 600 int rstreason = 0; /* For badport_bandlim accounting purposes */ 601 #ifdef TCP_SIGNATURE 602 uint8_t sig_checked = 0; 603 #endif 604 uint8_t iptos = 0; 605 struct m_tag *fwd_tag = NULL; 606 #ifdef INET6 607 struct ip6_hdr *ip6 = NULL; 608 int isipv6; 609 #else 610 const void *ip6 = NULL; 611 #endif /* INET6 */ 612 struct tcpopt to; /* options in this segment */ 613 char *s = NULL; /* address and port logging */ 614 int ti_locked; 615 #ifdef TCPDEBUG 616 /* 617 * The size of tcp_saveipgen must be the size of the max ip header, 618 * now IPv6. 619 */ 620 u_char tcp_saveipgen[IP6_HDR_LEN]; 621 struct tcphdr tcp_savetcp; 622 short ostate = 0; 623 #endif 624 625 #ifdef INET6 626 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 627 #endif 628 629 off0 = *offp; 630 m = *mp; 631 *mp = NULL; 632 to.to_flags = 0; 633 TCPSTAT_INC(tcps_rcvtotal); 634 635 #ifdef INET6 636 if (isipv6) { 637 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */ 638 639 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) { 640 m = m_pullup(m, sizeof(*ip6) + sizeof(*th)); 641 if (m == NULL) { 642 TCPSTAT_INC(tcps_rcvshort); 643 return (IPPROTO_DONE); 644 } 645 } 646 647 ip6 = mtod(m, struct ip6_hdr *); 648 th = (struct tcphdr *)((caddr_t)ip6 + off0); 649 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 650 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 651 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 652 th->th_sum = m->m_pkthdr.csum_data; 653 else 654 th->th_sum = in6_cksum_pseudo(ip6, tlen, 655 IPPROTO_TCP, m->m_pkthdr.csum_data); 656 th->th_sum ^= 0xffff; 657 } else 658 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 659 if (th->th_sum) { 660 TCPSTAT_INC(tcps_rcvbadsum); 661 goto drop; 662 } 663 664 /* 665 * Be proactive about unspecified IPv6 address in source. 666 * As we use all-zero to indicate unbounded/unconnected pcb, 667 * unspecified IPv6 address can be used to confuse us. 668 * 669 * Note that packets with unspecified IPv6 destination is 670 * already dropped in ip6_input. 671 */ 672 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 673 /* XXX stat */ 674 goto drop; 675 } 676 } 677 #endif 678 #if defined(INET) && defined(INET6) 679 else 680 #endif 681 #ifdef INET 682 { 683 /* 684 * Get IP and TCP header together in first mbuf. 685 * Note: IP leaves IP header in first mbuf. 686 */ 687 if (off0 > sizeof (struct ip)) { 688 ip_stripoptions(m); 689 off0 = sizeof(struct ip); 690 } 691 if (m->m_len < sizeof (struct tcpiphdr)) { 692 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 693 == NULL) { 694 TCPSTAT_INC(tcps_rcvshort); 695 return (IPPROTO_DONE); 696 } 697 } 698 ip = mtod(m, struct ip *); 699 th = (struct tcphdr *)((caddr_t)ip + off0); 700 tlen = ntohs(ip->ip_len) - off0; 701 702 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 703 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 704 th->th_sum = m->m_pkthdr.csum_data; 705 else 706 th->th_sum = in_pseudo(ip->ip_src.s_addr, 707 ip->ip_dst.s_addr, 708 htonl(m->m_pkthdr.csum_data + tlen + 709 IPPROTO_TCP)); 710 th->th_sum ^= 0xffff; 711 } else { 712 struct ipovly *ipov = (struct ipovly *)ip; 713 714 /* 715 * Checksum extended TCP header and data. 716 */ 717 len = off0 + tlen; 718 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 719 ipov->ih_len = htons(tlen); 720 th->th_sum = in_cksum(m, len); 721 /* Reset length for SDT probes. */ 722 ip->ip_len = htons(tlen + off0); 723 } 724 725 if (th->th_sum) { 726 TCPSTAT_INC(tcps_rcvbadsum); 727 goto drop; 728 } 729 /* Re-initialization for later version check */ 730 ip->ip_v = IPVERSION; 731 } 732 #endif /* INET */ 733 734 #ifdef INET6 735 if (isipv6) 736 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 737 #endif 738 #if defined(INET) && defined(INET6) 739 else 740 #endif 741 #ifdef INET 742 iptos = ip->ip_tos; 743 #endif 744 745 /* 746 * Check that TCP offset makes sense, 747 * pull out TCP options and adjust length. XXX 748 */ 749 off = th->th_off << 2; 750 if (off < sizeof (struct tcphdr) || off > tlen) { 751 TCPSTAT_INC(tcps_rcvbadoff); 752 goto drop; 753 } 754 tlen -= off; /* tlen is used instead of ti->ti_len */ 755 if (off > sizeof (struct tcphdr)) { 756 #ifdef INET6 757 if (isipv6) { 758 IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE); 759 ip6 = mtod(m, struct ip6_hdr *); 760 th = (struct tcphdr *)((caddr_t)ip6 + off0); 761 } 762 #endif 763 #if defined(INET) && defined(INET6) 764 else 765 #endif 766 #ifdef INET 767 { 768 if (m->m_len < sizeof(struct ip) + off) { 769 if ((m = m_pullup(m, sizeof (struct ip) + off)) 770 == NULL) { 771 TCPSTAT_INC(tcps_rcvshort); 772 return (IPPROTO_DONE); 773 } 774 ip = mtod(m, struct ip *); 775 th = (struct tcphdr *)((caddr_t)ip + off0); 776 } 777 } 778 #endif 779 optlen = off - sizeof (struct tcphdr); 780 optp = (u_char *)(th + 1); 781 } 782 thflags = th->th_flags; 783 784 /* 785 * Convert TCP protocol specific fields to host format. 786 */ 787 tcp_fields_to_host(th); 788 789 /* 790 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 791 */ 792 drop_hdrlen = off0 + off; 793 794 /* 795 * Locate pcb for segment; if we're likely to add or remove a 796 * connection then first acquire pcbinfo lock. There are three cases 797 * where we might discover later we need a write lock despite the 798 * flags: ACKs moving a connection out of the syncache, ACKs for a 799 * connection in TIMEWAIT and SYNs not targeting a listening socket. 800 */ 801 if ((thflags & (TH_FIN | TH_RST)) != 0) { 802 INP_INFO_RLOCK(&V_tcbinfo); 803 ti_locked = TI_RLOCKED; 804 } else 805 ti_locked = TI_UNLOCKED; 806 807 /* 808 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 809 */ 810 if ( 811 #ifdef INET6 812 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 813 #ifdef INET 814 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 815 #endif 816 #endif 817 #if defined(INET) && !defined(INET6) 818 (m->m_flags & M_IP_NEXTHOP) 819 #endif 820 ) 821 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 822 823 findpcb: 824 #ifdef INVARIANTS 825 if (ti_locked == TI_RLOCKED) { 826 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 827 } else { 828 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 829 } 830 #endif 831 #ifdef INET6 832 if (isipv6 && fwd_tag != NULL) { 833 struct sockaddr_in6 *next_hop6; 834 835 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 836 /* 837 * Transparently forwarded. Pretend to be the destination. 838 * Already got one like this? 839 */ 840 inp = in6_pcblookup_mbuf(&V_tcbinfo, 841 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 842 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 843 if (!inp) { 844 /* 845 * It's new. Try to find the ambushing socket. 846 * Because we've rewritten the destination address, 847 * any hardware-generated hash is ignored. 848 */ 849 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 850 th->th_sport, &next_hop6->sin6_addr, 851 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 852 th->th_dport, INPLOOKUP_WILDCARD | 853 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 854 } 855 } else if (isipv6) { 856 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 857 th->th_sport, &ip6->ip6_dst, th->th_dport, 858 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 859 m->m_pkthdr.rcvif, m); 860 } 861 #endif /* INET6 */ 862 #if defined(INET6) && defined(INET) 863 else 864 #endif 865 #ifdef INET 866 if (fwd_tag != NULL) { 867 struct sockaddr_in *next_hop; 868 869 next_hop = (struct sockaddr_in *)(fwd_tag+1); 870 /* 871 * Transparently forwarded. Pretend to be the destination. 872 * already got one like this? 873 */ 874 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 875 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 876 m->m_pkthdr.rcvif, m); 877 if (!inp) { 878 /* 879 * It's new. Try to find the ambushing socket. 880 * Because we've rewritten the destination address, 881 * any hardware-generated hash is ignored. 882 */ 883 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 884 th->th_sport, next_hop->sin_addr, 885 next_hop->sin_port ? ntohs(next_hop->sin_port) : 886 th->th_dport, INPLOOKUP_WILDCARD | 887 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 888 } 889 } else 890 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 891 th->th_sport, ip->ip_dst, th->th_dport, 892 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 893 m->m_pkthdr.rcvif, m); 894 #endif /* INET */ 895 896 /* 897 * If the INPCB does not exist then all data in the incoming 898 * segment is discarded and an appropriate RST is sent back. 899 * XXX MRT Send RST using which routing table? 900 */ 901 if (inp == NULL) { 902 /* 903 * Log communication attempts to ports that are not 904 * in use. 905 */ 906 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 907 tcp_log_in_vain == 2) { 908 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 909 log(LOG_INFO, "%s; %s: Connection attempt " 910 "to closed port\n", s, __func__); 911 } 912 /* 913 * When blackholing do not respond with a RST but 914 * completely ignore the segment and drop it. 915 */ 916 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 917 V_blackhole == 2) 918 goto dropunlock; 919 920 rstreason = BANDLIM_RST_CLOSEDPORT; 921 goto dropwithreset; 922 } 923 INP_WLOCK_ASSERT(inp); 924 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 925 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 926 ((inp->inp_socket == NULL) || 927 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 928 inp->inp_flowid = m->m_pkthdr.flowid; 929 inp->inp_flowtype = M_HASHTYPE_GET(m); 930 } 931 #ifdef IPSEC 932 #ifdef INET6 933 if (isipv6 && ipsec6_in_reject(m, inp)) { 934 goto dropunlock; 935 } else 936 #endif /* INET6 */ 937 if (ipsec4_in_reject(m, inp) != 0) { 938 goto dropunlock; 939 } 940 #endif /* IPSEC */ 941 942 /* 943 * Check the minimum TTL for socket. 944 */ 945 if (inp->inp_ip_minttl != 0) { 946 #ifdef INET6 947 if (isipv6) { 948 if (inp->inp_ip_minttl > ip6->ip6_hlim) 949 goto dropunlock; 950 } else 951 #endif 952 if (inp->inp_ip_minttl > ip->ip_ttl) 953 goto dropunlock; 954 } 955 956 /* 957 * A previous connection in TIMEWAIT state is supposed to catch stray 958 * or duplicate segments arriving late. If this segment was a 959 * legitimate new connection attempt, the old INPCB gets removed and 960 * we can try again to find a listening socket. 961 * 962 * At this point, due to earlier optimism, we may hold only an inpcb 963 * lock, and not the inpcbinfo write lock. If so, we need to try to 964 * acquire it, or if that fails, acquire a reference on the inpcb, 965 * drop all locks, acquire a global write lock, and then re-acquire 966 * the inpcb lock. We may at that point discover that another thread 967 * has tried to free the inpcb, in which case we need to loop back 968 * and try to find a new inpcb to deliver to. 969 * 970 * XXXRW: It may be time to rethink timewait locking. 971 */ 972 relocked: 973 if (inp->inp_flags & INP_TIMEWAIT) { 974 if (ti_locked == TI_UNLOCKED) { 975 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 976 in_pcbref(inp); 977 INP_WUNLOCK(inp); 978 INP_INFO_RLOCK(&V_tcbinfo); 979 ti_locked = TI_RLOCKED; 980 INP_WLOCK(inp); 981 if (in_pcbrele_wlocked(inp)) { 982 inp = NULL; 983 goto findpcb; 984 } 985 } else 986 ti_locked = TI_RLOCKED; 987 } 988 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 989 990 if (thflags & TH_SYN) 991 tcp_dooptions(&to, optp, optlen, TO_SYN); 992 /* 993 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 994 */ 995 if (tcp_twcheck(inp, &to, th, m, tlen)) 996 goto findpcb; 997 INP_INFO_RUNLOCK(&V_tcbinfo); 998 return (IPPROTO_DONE); 999 } 1000 /* 1001 * The TCPCB may no longer exist if the connection is winding 1002 * down or it is in the CLOSED state. Either way we drop the 1003 * segment and send an appropriate response. 1004 */ 1005 tp = intotcpcb(inp); 1006 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1007 rstreason = BANDLIM_RST_CLOSEDPORT; 1008 goto dropwithreset; 1009 } 1010 1011 #ifdef TCP_OFFLOAD 1012 if (tp->t_flags & TF_TOE) { 1013 tcp_offload_input(tp, m); 1014 m = NULL; /* consumed by the TOE driver */ 1015 goto dropunlock; 1016 } 1017 #endif 1018 1019 /* 1020 * We've identified a valid inpcb, but it could be that we need an 1021 * inpcbinfo write lock but don't hold it. In this case, attempt to 1022 * acquire using the same strategy as the TIMEWAIT case above. If we 1023 * relock, we have to jump back to 'relocked' as the connection might 1024 * now be in TIMEWAIT. 1025 */ 1026 #ifdef INVARIANTS 1027 if ((thflags & (TH_FIN | TH_RST)) != 0) 1028 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1029 #endif 1030 if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) || 1031 (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN) && 1032 !(tp->t_flags & TF_FASTOPEN)))) { 1033 if (ti_locked == TI_UNLOCKED) { 1034 if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) { 1035 in_pcbref(inp); 1036 INP_WUNLOCK(inp); 1037 INP_INFO_RLOCK(&V_tcbinfo); 1038 ti_locked = TI_RLOCKED; 1039 INP_WLOCK(inp); 1040 if (in_pcbrele_wlocked(inp)) { 1041 inp = NULL; 1042 goto findpcb; 1043 } 1044 goto relocked; 1045 } else 1046 ti_locked = TI_RLOCKED; 1047 } 1048 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1049 } 1050 1051 #ifdef MAC 1052 INP_WLOCK_ASSERT(inp); 1053 if (mac_inpcb_check_deliver(inp, m)) 1054 goto dropunlock; 1055 #endif 1056 so = inp->inp_socket; 1057 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1058 #ifdef TCPDEBUG 1059 if (so->so_options & SO_DEBUG) { 1060 ostate = tp->t_state; 1061 #ifdef INET6 1062 if (isipv6) { 1063 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1064 } else 1065 #endif 1066 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1067 tcp_savetcp = *th; 1068 } 1069 #endif /* TCPDEBUG */ 1070 /* 1071 * When the socket is accepting connections (the INPCB is in LISTEN 1072 * state) we look into the SYN cache if this is a new connection 1073 * attempt or the completion of a previous one. 1074 */ 1075 if (so->so_options & SO_ACCEPTCONN) { 1076 struct in_conninfo inc; 1077 1078 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but " 1079 "tp not listening", __func__)); 1080 bzero(&inc, sizeof(inc)); 1081 #ifdef INET6 1082 if (isipv6) { 1083 inc.inc_flags |= INC_ISIPV6; 1084 inc.inc6_faddr = ip6->ip6_src; 1085 inc.inc6_laddr = ip6->ip6_dst; 1086 } else 1087 #endif 1088 { 1089 inc.inc_faddr = ip->ip_src; 1090 inc.inc_laddr = ip->ip_dst; 1091 } 1092 inc.inc_fport = th->th_sport; 1093 inc.inc_lport = th->th_dport; 1094 inc.inc_fibnum = so->so_fibnum; 1095 1096 /* 1097 * Check for an existing connection attempt in syncache if 1098 * the flag is only ACK. A successful lookup creates a new 1099 * socket appended to the listen queue in SYN_RECEIVED state. 1100 */ 1101 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1102 1103 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1104 /* 1105 * Parse the TCP options here because 1106 * syncookies need access to the reflected 1107 * timestamp. 1108 */ 1109 tcp_dooptions(&to, optp, optlen, 0); 1110 /* 1111 * NB: syncache_expand() doesn't unlock 1112 * inp and tcpinfo locks. 1113 */ 1114 if (!syncache_expand(&inc, &to, th, &so, m)) { 1115 /* 1116 * No syncache entry or ACK was not 1117 * for our SYN/ACK. Send a RST. 1118 * NB: syncache did its own logging 1119 * of the failure cause. 1120 */ 1121 rstreason = BANDLIM_RST_OPENPORT; 1122 goto dropwithreset; 1123 } 1124 #ifdef TCP_RFC7413 1125 new_tfo_socket: 1126 #endif 1127 if (so == NULL) { 1128 /* 1129 * We completed the 3-way handshake 1130 * but could not allocate a socket 1131 * either due to memory shortage, 1132 * listen queue length limits or 1133 * global socket limits. Send RST 1134 * or wait and have the remote end 1135 * retransmit the ACK for another 1136 * try. 1137 */ 1138 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1139 log(LOG_DEBUG, "%s; %s: Listen socket: " 1140 "Socket allocation failed due to " 1141 "limits or memory shortage, %s\n", 1142 s, __func__, 1143 V_tcp_sc_rst_sock_fail ? 1144 "sending RST" : "try again"); 1145 if (V_tcp_sc_rst_sock_fail) { 1146 rstreason = BANDLIM_UNLIMITED; 1147 goto dropwithreset; 1148 } else 1149 goto dropunlock; 1150 } 1151 /* 1152 * Socket is created in state SYN_RECEIVED. 1153 * Unlock the listen socket, lock the newly 1154 * created socket and update the tp variable. 1155 */ 1156 INP_WUNLOCK(inp); /* listen socket */ 1157 inp = sotoinpcb(so); 1158 /* 1159 * New connection inpcb is already locked by 1160 * syncache_expand(). 1161 */ 1162 INP_WLOCK_ASSERT(inp); 1163 tp = intotcpcb(inp); 1164 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1165 ("%s: ", __func__)); 1166 #ifdef TCP_SIGNATURE 1167 if (sig_checked == 0) { 1168 tcp_dooptions(&to, optp, optlen, 1169 (thflags & TH_SYN) ? TO_SYN : 0); 1170 if (!tcp_signature_verify_input(m, off0, tlen, 1171 optlen, &to, th, tp->t_flags)) { 1172 1173 /* 1174 * In SYN_SENT state if it receives an 1175 * RST, it is allowed for further 1176 * processing. 1177 */ 1178 if ((thflags & TH_RST) == 0 || 1179 (tp->t_state == TCPS_SYN_SENT) == 0) 1180 goto dropunlock; 1181 } 1182 sig_checked = 1; 1183 } 1184 #endif 1185 1186 /* 1187 * Process the segment and the data it 1188 * contains. tcp_do_segment() consumes 1189 * the mbuf chain and unlocks the inpcb. 1190 */ 1191 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1192 iptos, ti_locked); 1193 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1194 return (IPPROTO_DONE); 1195 } 1196 /* 1197 * Segment flag validation for new connection attempts: 1198 * 1199 * Our (SYN|ACK) response was rejected. 1200 * Check with syncache and remove entry to prevent 1201 * retransmits. 1202 * 1203 * NB: syncache_chkrst does its own logging of failure 1204 * causes. 1205 */ 1206 if (thflags & TH_RST) { 1207 syncache_chkrst(&inc, th); 1208 goto dropunlock; 1209 } 1210 /* 1211 * We can't do anything without SYN. 1212 */ 1213 if ((thflags & TH_SYN) == 0) { 1214 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1215 log(LOG_DEBUG, "%s; %s: Listen socket: " 1216 "SYN is missing, segment ignored\n", 1217 s, __func__); 1218 TCPSTAT_INC(tcps_badsyn); 1219 goto dropunlock; 1220 } 1221 /* 1222 * (SYN|ACK) is bogus on a listen socket. 1223 */ 1224 if (thflags & TH_ACK) { 1225 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1226 log(LOG_DEBUG, "%s; %s: Listen socket: " 1227 "SYN|ACK invalid, segment rejected\n", 1228 s, __func__); 1229 syncache_badack(&inc); /* XXX: Not needed! */ 1230 TCPSTAT_INC(tcps_badsyn); 1231 rstreason = BANDLIM_RST_OPENPORT; 1232 goto dropwithreset; 1233 } 1234 /* 1235 * If the drop_synfin option is enabled, drop all 1236 * segments with both the SYN and FIN bits set. 1237 * This prevents e.g. nmap from identifying the 1238 * TCP/IP stack. 1239 * XXX: Poor reasoning. nmap has other methods 1240 * and is constantly refining its stack detection 1241 * strategies. 1242 * XXX: This is a violation of the TCP specification 1243 * and was used by RFC1644. 1244 */ 1245 if ((thflags & TH_FIN) && V_drop_synfin) { 1246 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1247 log(LOG_DEBUG, "%s; %s: Listen socket: " 1248 "SYN|FIN segment ignored (based on " 1249 "sysctl setting)\n", s, __func__); 1250 TCPSTAT_INC(tcps_badsyn); 1251 goto dropunlock; 1252 } 1253 /* 1254 * Segment's flags are (SYN) or (SYN|FIN). 1255 * 1256 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1257 * as they do not affect the state of the TCP FSM. 1258 * The data pointed to by TH_URG and th_urp is ignored. 1259 */ 1260 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1261 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1262 KASSERT(thflags & (TH_SYN), 1263 ("%s: Listen socket: TH_SYN not set", __func__)); 1264 #ifdef INET6 1265 /* 1266 * If deprecated address is forbidden, 1267 * we do not accept SYN to deprecated interface 1268 * address to prevent any new inbound connection from 1269 * getting established. 1270 * When we do not accept SYN, we send a TCP RST, 1271 * with deprecated source address (instead of dropping 1272 * it). We compromise it as it is much better for peer 1273 * to send a RST, and RST will be the final packet 1274 * for the exchange. 1275 * 1276 * If we do not forbid deprecated addresses, we accept 1277 * the SYN packet. RFC2462 does not suggest dropping 1278 * SYN in this case. 1279 * If we decipher RFC2462 5.5.4, it says like this: 1280 * 1. use of deprecated addr with existing 1281 * communication is okay - "SHOULD continue to be 1282 * used" 1283 * 2. use of it with new communication: 1284 * (2a) "SHOULD NOT be used if alternate address 1285 * with sufficient scope is available" 1286 * (2b) nothing mentioned otherwise. 1287 * Here we fall into (2b) case as we have no choice in 1288 * our source address selection - we must obey the peer. 1289 * 1290 * The wording in RFC2462 is confusing, and there are 1291 * multiple description text for deprecated address 1292 * handling - worse, they are not exactly the same. 1293 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1294 */ 1295 if (isipv6 && !V_ip6_use_deprecated) { 1296 struct in6_ifaddr *ia6; 1297 1298 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1299 if (ia6 != NULL && 1300 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1301 ifa_free(&ia6->ia_ifa); 1302 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1303 log(LOG_DEBUG, "%s; %s: Listen socket: " 1304 "Connection attempt to deprecated " 1305 "IPv6 address rejected\n", 1306 s, __func__); 1307 rstreason = BANDLIM_RST_OPENPORT; 1308 goto dropwithreset; 1309 } 1310 if (ia6) 1311 ifa_free(&ia6->ia_ifa); 1312 } 1313 #endif /* INET6 */ 1314 /* 1315 * Basic sanity checks on incoming SYN requests: 1316 * Don't respond if the destination is a link layer 1317 * broadcast according to RFC1122 4.2.3.10, p. 104. 1318 * If it is from this socket it must be forged. 1319 * Don't respond if the source or destination is a 1320 * global or subnet broad- or multicast address. 1321 * Note that it is quite possible to receive unicast 1322 * link-layer packets with a broadcast IP address. Use 1323 * in_broadcast() to find them. 1324 */ 1325 if (m->m_flags & (M_BCAST|M_MCAST)) { 1326 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1327 log(LOG_DEBUG, "%s; %s: Listen socket: " 1328 "Connection attempt from broad- or multicast " 1329 "link layer address ignored\n", s, __func__); 1330 goto dropunlock; 1331 } 1332 #ifdef INET6 1333 if (isipv6) { 1334 if (th->th_dport == th->th_sport && 1335 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1336 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1337 log(LOG_DEBUG, "%s; %s: Listen socket: " 1338 "Connection attempt to/from self " 1339 "ignored\n", s, __func__); 1340 goto dropunlock; 1341 } 1342 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1343 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1344 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1345 log(LOG_DEBUG, "%s; %s: Listen socket: " 1346 "Connection attempt from/to multicast " 1347 "address ignored\n", s, __func__); 1348 goto dropunlock; 1349 } 1350 } 1351 #endif 1352 #if defined(INET) && defined(INET6) 1353 else 1354 #endif 1355 #ifdef INET 1356 { 1357 if (th->th_dport == th->th_sport && 1358 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1359 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1360 log(LOG_DEBUG, "%s; %s: Listen socket: " 1361 "Connection attempt from/to self " 1362 "ignored\n", s, __func__); 1363 goto dropunlock; 1364 } 1365 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1366 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1367 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1368 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1369 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1370 log(LOG_DEBUG, "%s; %s: Listen socket: " 1371 "Connection attempt from/to broad- " 1372 "or multicast address ignored\n", 1373 s, __func__); 1374 goto dropunlock; 1375 } 1376 } 1377 #endif 1378 /* 1379 * SYN appears to be valid. Create compressed TCP state 1380 * for syncache. 1381 */ 1382 #ifdef TCPDEBUG 1383 if (so->so_options & SO_DEBUG) 1384 tcp_trace(TA_INPUT, ostate, tp, 1385 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1386 #endif 1387 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1388 tcp_dooptions(&to, optp, optlen, TO_SYN); 1389 #ifdef TCP_RFC7413 1390 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL)) 1391 goto new_tfo_socket; 1392 #else 1393 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL); 1394 #endif 1395 /* 1396 * Entry added to syncache and mbuf consumed. 1397 * Only the listen socket is unlocked by syncache_add(). 1398 */ 1399 if (ti_locked == TI_RLOCKED) { 1400 INP_INFO_RUNLOCK(&V_tcbinfo); 1401 ti_locked = TI_UNLOCKED; 1402 } 1403 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1404 return (IPPROTO_DONE); 1405 } else if (tp->t_state == TCPS_LISTEN) { 1406 /* 1407 * When a listen socket is torn down the SO_ACCEPTCONN 1408 * flag is removed first while connections are drained 1409 * from the accept queue in a unlock/lock cycle of the 1410 * ACCEPT_LOCK, opening a race condition allowing a SYN 1411 * attempt go through unhandled. 1412 */ 1413 goto dropunlock; 1414 } 1415 1416 #ifdef TCP_SIGNATURE 1417 if (sig_checked == 0) { 1418 tcp_dooptions(&to, optp, optlen, 1419 (thflags & TH_SYN) ? TO_SYN : 0); 1420 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to, 1421 th, tp->t_flags)) { 1422 1423 /* 1424 * In SYN_SENT state if it receives an RST, it is 1425 * allowed for further processing. 1426 */ 1427 if ((thflags & TH_RST) == 0 || 1428 (tp->t_state == TCPS_SYN_SENT) == 0) 1429 goto dropunlock; 1430 } 1431 sig_checked = 1; 1432 } 1433 #endif 1434 1435 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1436 1437 /* 1438 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1439 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1440 * the inpcb, and unlocks pcbinfo. 1441 */ 1442 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked); 1443 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1444 return (IPPROTO_DONE); 1445 1446 dropwithreset: 1447 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1448 1449 if (ti_locked == TI_RLOCKED) { 1450 INP_INFO_RUNLOCK(&V_tcbinfo); 1451 ti_locked = TI_UNLOCKED; 1452 } 1453 #ifdef INVARIANTS 1454 else { 1455 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset " 1456 "ti_locked: %d", __func__, ti_locked)); 1457 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1458 } 1459 #endif 1460 1461 if (inp != NULL) { 1462 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1463 INP_WUNLOCK(inp); 1464 } else 1465 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1466 m = NULL; /* mbuf chain got consumed. */ 1467 goto drop; 1468 1469 dropunlock: 1470 if (m != NULL) 1471 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th); 1472 1473 if (ti_locked == TI_RLOCKED) { 1474 INP_INFO_RUNLOCK(&V_tcbinfo); 1475 ti_locked = TI_UNLOCKED; 1476 } 1477 #ifdef INVARIANTS 1478 else { 1479 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock " 1480 "ti_locked: %d", __func__, ti_locked)); 1481 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1482 } 1483 #endif 1484 1485 if (inp != NULL) 1486 INP_WUNLOCK(inp); 1487 1488 drop: 1489 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1490 if (s != NULL) 1491 free(s, M_TCPLOG); 1492 if (m != NULL) 1493 m_freem(m); 1494 return (IPPROTO_DONE); 1495 } 1496 1497 void 1498 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1499 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos, 1500 int ti_locked) 1501 { 1502 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1503 int rstreason, todrop, win; 1504 u_long tiwin; 1505 char *s; 1506 struct in_conninfo *inc; 1507 struct mbuf *mfree; 1508 struct tcpopt to; 1509 int tfo_syn; 1510 1511 #ifdef TCPDEBUG 1512 /* 1513 * The size of tcp_saveipgen must be the size of the max ip header, 1514 * now IPv6. 1515 */ 1516 u_char tcp_saveipgen[IP6_HDR_LEN]; 1517 struct tcphdr tcp_savetcp; 1518 short ostate = 0; 1519 #endif 1520 thflags = th->th_flags; 1521 inc = &tp->t_inpcb->inp_inc; 1522 tp->sackhint.last_sack_ack = 0; 1523 sack_changed = 0; 1524 1525 /* 1526 * If this is either a state-changing packet or current state isn't 1527 * established, we require a write lock on tcbinfo. Otherwise, we 1528 * allow the tcbinfo to be in either alocked or unlocked, as the 1529 * caller may have unnecessarily acquired a write lock due to a race. 1530 */ 1531 if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 || 1532 tp->t_state != TCPS_ESTABLISHED) { 1533 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for " 1534 "SYN/FIN/RST/!EST", __func__, ti_locked)); 1535 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1536 } else { 1537 #ifdef INVARIANTS 1538 if (ti_locked == TI_RLOCKED) 1539 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 1540 else { 1541 KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST " 1542 "ti_locked: %d", __func__, ti_locked)); 1543 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 1544 } 1545 #endif 1546 } 1547 INP_WLOCK_ASSERT(tp->t_inpcb); 1548 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1549 __func__)); 1550 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1551 __func__)); 1552 1553 #ifdef TCPPCAP 1554 /* Save segment, if requested. */ 1555 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1556 #endif 1557 1558 /* 1559 * Segment received on connection. 1560 * Reset idle time and keep-alive timer. 1561 * XXX: This should be done after segment 1562 * validation to ignore broken/spoofed segs. 1563 */ 1564 tp->t_rcvtime = ticks; 1565 if (TCPS_HAVEESTABLISHED(tp->t_state)) 1566 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 1567 1568 /* 1569 * Scale up the window into a 32-bit value. 1570 * For the SYN_SENT state the scale is zero. 1571 */ 1572 tiwin = th->th_win << tp->snd_scale; 1573 1574 /* 1575 * TCP ECN processing. 1576 */ 1577 if (tp->t_flags & TF_ECN_PERMIT) { 1578 if (thflags & TH_CWR) 1579 tp->t_flags &= ~TF_ECN_SND_ECE; 1580 switch (iptos & IPTOS_ECN_MASK) { 1581 case IPTOS_ECN_CE: 1582 tp->t_flags |= TF_ECN_SND_ECE; 1583 TCPSTAT_INC(tcps_ecn_ce); 1584 break; 1585 case IPTOS_ECN_ECT0: 1586 TCPSTAT_INC(tcps_ecn_ect0); 1587 break; 1588 case IPTOS_ECN_ECT1: 1589 TCPSTAT_INC(tcps_ecn_ect1); 1590 break; 1591 } 1592 1593 /* Process a packet differently from RFC3168. */ 1594 cc_ecnpkt_handler(tp, th, iptos); 1595 1596 /* Congestion experienced. */ 1597 if (thflags & TH_ECE) { 1598 cc_cong_signal(tp, th, CC_ECN); 1599 } 1600 } 1601 1602 /* 1603 * Parse options on any incoming segment. 1604 */ 1605 tcp_dooptions(&to, (u_char *)(th + 1), 1606 (th->th_off << 2) - sizeof(struct tcphdr), 1607 (thflags & TH_SYN) ? TO_SYN : 0); 1608 1609 /* 1610 * If echoed timestamp is later than the current time, 1611 * fall back to non RFC1323 RTT calculation. Normalize 1612 * timestamp if syncookies were used when this connection 1613 * was established. 1614 */ 1615 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1616 to.to_tsecr -= tp->ts_offset; 1617 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1618 to.to_tsecr = 0; 1619 } 1620 /* 1621 * If timestamps were negotiated during SYN/ACK they should 1622 * appear on every segment during this session and vice versa. 1623 */ 1624 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1625 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1626 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1627 "no action\n", s, __func__); 1628 free(s, M_TCPLOG); 1629 } 1630 } 1631 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1632 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1633 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1634 "no action\n", s, __func__); 1635 free(s, M_TCPLOG); 1636 } 1637 } 1638 1639 /* 1640 * Process options only when we get SYN/ACK back. The SYN case 1641 * for incoming connections is handled in tcp_syncache. 1642 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1643 * or <SYN,ACK>) segment itself is never scaled. 1644 * XXX this is traditional behavior, may need to be cleaned up. 1645 */ 1646 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1647 if ((to.to_flags & TOF_SCALE) && 1648 (tp->t_flags & TF_REQ_SCALE)) { 1649 tp->t_flags |= TF_RCVD_SCALE; 1650 tp->snd_scale = to.to_wscale; 1651 } 1652 /* 1653 * Initial send window. It will be updated with 1654 * the next incoming segment to the scaled value. 1655 */ 1656 tp->snd_wnd = th->th_win; 1657 if (to.to_flags & TOF_TS) { 1658 tp->t_flags |= TF_RCVD_TSTMP; 1659 tp->ts_recent = to.to_tsval; 1660 tp->ts_recent_age = tcp_ts_getticks(); 1661 } 1662 if (to.to_flags & TOF_MSS) 1663 tcp_mss(tp, to.to_mss); 1664 if ((tp->t_flags & TF_SACK_PERMIT) && 1665 (to.to_flags & TOF_SACKPERM) == 0) 1666 tp->t_flags &= ~TF_SACK_PERMIT; 1667 } 1668 1669 /* 1670 * Header prediction: check for the two common cases 1671 * of a uni-directional data xfer. If the packet has 1672 * no control flags, is in-sequence, the window didn't 1673 * change and we're not retransmitting, it's a 1674 * candidate. If the length is zero and the ack moved 1675 * forward, we're the sender side of the xfer. Just 1676 * free the data acked & wake any higher level process 1677 * that was blocked waiting for space. If the length 1678 * is non-zero and the ack didn't move, we're the 1679 * receiver side. If we're getting packets in-order 1680 * (the reassembly queue is empty), add the data to 1681 * the socket buffer and note that we need a delayed ack. 1682 * Make sure that the hidden state-flags are also off. 1683 * Since we check for TCPS_ESTABLISHED first, it can only 1684 * be TH_NEEDSYN. 1685 */ 1686 if (tp->t_state == TCPS_ESTABLISHED && 1687 th->th_seq == tp->rcv_nxt && 1688 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1689 tp->snd_nxt == tp->snd_max && 1690 tiwin && tiwin == tp->snd_wnd && 1691 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1692 LIST_EMPTY(&tp->t_segq) && 1693 ((to.to_flags & TOF_TS) == 0 || 1694 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1695 1696 /* 1697 * If last ACK falls within this segment's sequence numbers, 1698 * record the timestamp. 1699 * NOTE that the test is modified according to the latest 1700 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1701 */ 1702 if ((to.to_flags & TOF_TS) != 0 && 1703 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1704 tp->ts_recent_age = tcp_ts_getticks(); 1705 tp->ts_recent = to.to_tsval; 1706 } 1707 1708 if (tlen == 0) { 1709 if (SEQ_GT(th->th_ack, tp->snd_una) && 1710 SEQ_LEQ(th->th_ack, tp->snd_max) && 1711 !IN_RECOVERY(tp->t_flags) && 1712 (to.to_flags & TOF_SACK) == 0 && 1713 TAILQ_EMPTY(&tp->snd_holes)) { 1714 /* 1715 * This is a pure ack for outstanding data. 1716 */ 1717 if (ti_locked == TI_RLOCKED) 1718 INP_INFO_RUNLOCK(&V_tcbinfo); 1719 ti_locked = TI_UNLOCKED; 1720 1721 TCPSTAT_INC(tcps_predack); 1722 1723 /* 1724 * "bad retransmit" recovery. 1725 */ 1726 if (tp->t_rxtshift == 1 && 1727 tp->t_flags & TF_PREVVALID && 1728 (int)(ticks - tp->t_badrxtwin) < 0) { 1729 cc_cong_signal(tp, th, CC_RTO_ERR); 1730 } 1731 1732 /* 1733 * Recalculate the transmit timer / rtt. 1734 * 1735 * Some boxes send broken timestamp replies 1736 * during the SYN+ACK phase, ignore 1737 * timestamps of 0 or we could calculate a 1738 * huge RTT and blow up the retransmit timer. 1739 */ 1740 if ((to.to_flags & TOF_TS) != 0 && 1741 to.to_tsecr) { 1742 u_int t; 1743 1744 t = tcp_ts_getticks() - to.to_tsecr; 1745 if (!tp->t_rttlow || tp->t_rttlow > t) 1746 tp->t_rttlow = t; 1747 tcp_xmit_timer(tp, 1748 TCP_TS_TO_TICKS(t) + 1); 1749 } else if (tp->t_rtttime && 1750 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1751 if (!tp->t_rttlow || 1752 tp->t_rttlow > ticks - tp->t_rtttime) 1753 tp->t_rttlow = ticks - tp->t_rtttime; 1754 tcp_xmit_timer(tp, 1755 ticks - tp->t_rtttime); 1756 } 1757 acked = BYTES_THIS_ACK(tp, th); 1758 1759 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1760 hhook_run_tcp_est_in(tp, th, &to); 1761 1762 TCPSTAT_INC(tcps_rcvackpack); 1763 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1764 sbdrop(&so->so_snd, acked); 1765 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1766 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1767 tp->snd_recover = th->th_ack - 1; 1768 1769 /* 1770 * Let the congestion control algorithm update 1771 * congestion control related information. This 1772 * typically means increasing the congestion 1773 * window. 1774 */ 1775 cc_ack_received(tp, th, CC_ACK); 1776 1777 tp->snd_una = th->th_ack; 1778 /* 1779 * Pull snd_wl2 up to prevent seq wrap relative 1780 * to th_ack. 1781 */ 1782 tp->snd_wl2 = th->th_ack; 1783 tp->t_dupacks = 0; 1784 m_freem(m); 1785 1786 /* 1787 * If all outstanding data are acked, stop 1788 * retransmit timer, otherwise restart timer 1789 * using current (possibly backed-off) value. 1790 * If process is waiting for space, 1791 * wakeup/selwakeup/signal. If data 1792 * are ready to send, let tcp_output 1793 * decide between more output or persist. 1794 */ 1795 #ifdef TCPDEBUG 1796 if (so->so_options & SO_DEBUG) 1797 tcp_trace(TA_INPUT, ostate, tp, 1798 (void *)tcp_saveipgen, 1799 &tcp_savetcp, 0); 1800 #endif 1801 TCP_PROBE3(debug__input, tp, th, 1802 mtod(m, const char *)); 1803 if (tp->snd_una == tp->snd_max) 1804 tcp_timer_activate(tp, TT_REXMT, 0); 1805 else if (!tcp_timer_active(tp, TT_PERSIST)) 1806 tcp_timer_activate(tp, TT_REXMT, 1807 tp->t_rxtcur); 1808 sowwakeup(so); 1809 if (sbavail(&so->so_snd)) 1810 (void) tp->t_fb->tfb_tcp_output(tp); 1811 goto check_delack; 1812 } 1813 } else if (th->th_ack == tp->snd_una && 1814 tlen <= sbspace(&so->so_rcv)) { 1815 int newsize = 0; /* automatic sockbuf scaling */ 1816 1817 /* 1818 * This is a pure, in-sequence data packet with 1819 * nothing on the reassembly queue and we have enough 1820 * buffer space to take it. 1821 */ 1822 if (ti_locked == TI_RLOCKED) 1823 INP_INFO_RUNLOCK(&V_tcbinfo); 1824 ti_locked = TI_UNLOCKED; 1825 1826 /* Clean receiver SACK report if present */ 1827 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1828 tcp_clean_sackreport(tp); 1829 TCPSTAT_INC(tcps_preddat); 1830 tp->rcv_nxt += tlen; 1831 /* 1832 * Pull snd_wl1 up to prevent seq wrap relative to 1833 * th_seq. 1834 */ 1835 tp->snd_wl1 = th->th_seq; 1836 /* 1837 * Pull rcv_up up to prevent seq wrap relative to 1838 * rcv_nxt. 1839 */ 1840 tp->rcv_up = tp->rcv_nxt; 1841 TCPSTAT_INC(tcps_rcvpack); 1842 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1843 #ifdef TCPDEBUG 1844 if (so->so_options & SO_DEBUG) 1845 tcp_trace(TA_INPUT, ostate, tp, 1846 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1847 #endif 1848 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 1849 1850 /* 1851 * Automatic sizing of receive socket buffer. Often the send 1852 * buffer size is not optimally adjusted to the actual network 1853 * conditions at hand (delay bandwidth product). Setting the 1854 * buffer size too small limits throughput on links with high 1855 * bandwidth and high delay (eg. trans-continental/oceanic links). 1856 * 1857 * On the receive side the socket buffer memory is only rarely 1858 * used to any significant extent. This allows us to be much 1859 * more aggressive in scaling the receive socket buffer. For 1860 * the case that the buffer space is actually used to a large 1861 * extent and we run out of kernel memory we can simply drop 1862 * the new segments; TCP on the sender will just retransmit it 1863 * later. Setting the buffer size too big may only consume too 1864 * much kernel memory if the application doesn't read() from 1865 * the socket or packet loss or reordering makes use of the 1866 * reassembly queue. 1867 * 1868 * The criteria to step up the receive buffer one notch are: 1869 * 1. Application has not set receive buffer size with 1870 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1871 * 2. the number of bytes received during the time it takes 1872 * one timestamp to be reflected back to us (the RTT); 1873 * 3. received bytes per RTT is within seven eighth of the 1874 * current socket buffer size; 1875 * 4. receive buffer size has not hit maximal automatic size; 1876 * 1877 * This algorithm does one step per RTT at most and only if 1878 * we receive a bulk stream w/o packet losses or reorderings. 1879 * Shrinking the buffer during idle times is not necessary as 1880 * it doesn't consume any memory when idle. 1881 * 1882 * TODO: Only step up if the application is actually serving 1883 * the buffer to better manage the socket buffer resources. 1884 */ 1885 if (V_tcp_do_autorcvbuf && 1886 (to.to_flags & TOF_TS) && 1887 to.to_tsecr && 1888 (so->so_rcv.sb_flags & SB_AUTOSIZE)) { 1889 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) && 1890 to.to_tsecr - tp->rfbuf_ts < hz) { 1891 if (tp->rfbuf_cnt > 1892 (so->so_rcv.sb_hiwat / 8 * 7) && 1893 so->so_rcv.sb_hiwat < 1894 V_tcp_autorcvbuf_max) { 1895 newsize = 1896 min(so->so_rcv.sb_hiwat + 1897 V_tcp_autorcvbuf_inc, 1898 V_tcp_autorcvbuf_max); 1899 } 1900 /* Start over with next RTT. */ 1901 tp->rfbuf_ts = 0; 1902 tp->rfbuf_cnt = 0; 1903 } else 1904 tp->rfbuf_cnt += tlen; /* add up */ 1905 } 1906 1907 /* Add data to socket buffer. */ 1908 SOCKBUF_LOCK(&so->so_rcv); 1909 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1910 m_freem(m); 1911 } else { 1912 /* 1913 * Set new socket buffer size. 1914 * Give up when limit is reached. 1915 */ 1916 if (newsize) 1917 if (!sbreserve_locked(&so->so_rcv, 1918 newsize, so, NULL)) 1919 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1920 m_adj(m, drop_hdrlen); /* delayed header drop */ 1921 sbappendstream_locked(&so->so_rcv, m, 0); 1922 } 1923 /* NB: sorwakeup_locked() does an implicit unlock. */ 1924 sorwakeup_locked(so); 1925 if (DELAY_ACK(tp, tlen)) { 1926 tp->t_flags |= TF_DELACK; 1927 } else { 1928 tp->t_flags |= TF_ACKNOW; 1929 tp->t_fb->tfb_tcp_output(tp); 1930 } 1931 goto check_delack; 1932 } 1933 } 1934 1935 /* 1936 * Calculate amount of space in receive window, 1937 * and then do TCP input processing. 1938 * Receive window is amount of space in rcv queue, 1939 * but not less than advertised window. 1940 */ 1941 win = sbspace(&so->so_rcv); 1942 if (win < 0) 1943 win = 0; 1944 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1945 1946 /* Reset receive buffer auto scaling when not in bulk receive mode. */ 1947 tp->rfbuf_ts = 0; 1948 tp->rfbuf_cnt = 0; 1949 1950 switch (tp->t_state) { 1951 1952 /* 1953 * If the state is SYN_RECEIVED: 1954 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1955 */ 1956 case TCPS_SYN_RECEIVED: 1957 if ((thflags & TH_ACK) && 1958 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1959 SEQ_GT(th->th_ack, tp->snd_max))) { 1960 rstreason = BANDLIM_RST_OPENPORT; 1961 goto dropwithreset; 1962 } 1963 #ifdef TCP_RFC7413 1964 if (tp->t_flags & TF_FASTOPEN) { 1965 /* 1966 * When a TFO connection is in SYN_RECEIVED, the 1967 * only valid packets are the initial SYN, a 1968 * retransmit/copy of the initial SYN (possibly with 1969 * a subset of the original data), a valid ACK, a 1970 * FIN, or a RST. 1971 */ 1972 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1973 rstreason = BANDLIM_RST_OPENPORT; 1974 goto dropwithreset; 1975 } else if (thflags & TH_SYN) { 1976 /* non-initial SYN is ignored */ 1977 if ((tcp_timer_active(tp, TT_DELACK) || 1978 tcp_timer_active(tp, TT_REXMT))) 1979 goto drop; 1980 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1981 goto drop; 1982 } 1983 } 1984 #endif 1985 break; 1986 1987 /* 1988 * If the state is SYN_SENT: 1989 * if seg contains an ACK, but not for our SYN, drop the input. 1990 * if seg contains a RST, then drop the connection. 1991 * if seg does not contain SYN, then drop it. 1992 * Otherwise this is an acceptable SYN segment 1993 * initialize tp->rcv_nxt and tp->irs 1994 * if seg contains ack then advance tp->snd_una 1995 * if seg contains an ECE and ECN support is enabled, the stream 1996 * is ECN capable. 1997 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1998 * arrange for segment to be acked (eventually) 1999 * continue processing rest of data/controls, beginning with URG 2000 */ 2001 case TCPS_SYN_SENT: 2002 if ((thflags & TH_ACK) && 2003 (SEQ_LEQ(th->th_ack, tp->iss) || 2004 SEQ_GT(th->th_ack, tp->snd_max))) { 2005 rstreason = BANDLIM_UNLIMITED; 2006 goto dropwithreset; 2007 } 2008 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 2009 TCP_PROBE5(connect__refused, NULL, tp, 2010 mtod(m, const char *), tp, th); 2011 tp = tcp_drop(tp, ECONNREFUSED); 2012 } 2013 if (thflags & TH_RST) 2014 goto drop; 2015 if (!(thflags & TH_SYN)) 2016 goto drop; 2017 2018 tp->irs = th->th_seq; 2019 tcp_rcvseqinit(tp); 2020 if (thflags & TH_ACK) { 2021 TCPSTAT_INC(tcps_connects); 2022 soisconnected(so); 2023 #ifdef MAC 2024 mac_socketpeer_set_from_mbuf(m, so); 2025 #endif 2026 /* Do window scaling on this connection? */ 2027 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2028 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2029 tp->rcv_scale = tp->request_r_scale; 2030 } 2031 tp->rcv_adv += imin(tp->rcv_wnd, 2032 TCP_MAXWIN << tp->rcv_scale); 2033 tp->snd_una++; /* SYN is acked */ 2034 /* 2035 * If there's data, delay ACK; if there's also a FIN 2036 * ACKNOW will be turned on later. 2037 */ 2038 if (DELAY_ACK(tp, tlen) && tlen != 0) 2039 tcp_timer_activate(tp, TT_DELACK, 2040 tcp_delacktime); 2041 else 2042 tp->t_flags |= TF_ACKNOW; 2043 2044 if ((thflags & TH_ECE) && V_tcp_do_ecn) { 2045 tp->t_flags |= TF_ECN_PERMIT; 2046 TCPSTAT_INC(tcps_ecn_shs); 2047 } 2048 2049 /* 2050 * Received <SYN,ACK> in SYN_SENT[*] state. 2051 * Transitions: 2052 * SYN_SENT --> ESTABLISHED 2053 * SYN_SENT* --> FIN_WAIT_1 2054 */ 2055 tp->t_starttime = ticks; 2056 if (tp->t_flags & TF_NEEDFIN) { 2057 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2058 tp->t_flags &= ~TF_NEEDFIN; 2059 thflags &= ~TH_SYN; 2060 } else { 2061 tcp_state_change(tp, TCPS_ESTABLISHED); 2062 TCP_PROBE5(connect__established, NULL, tp, 2063 mtod(m, const char *), tp, th); 2064 cc_conn_init(tp); 2065 tcp_timer_activate(tp, TT_KEEP, 2066 TP_KEEPIDLE(tp)); 2067 } 2068 } else { 2069 /* 2070 * Received initial SYN in SYN-SENT[*] state => 2071 * simultaneous open. 2072 * If it succeeds, connection is * half-synchronized. 2073 * Otherwise, do 3-way handshake: 2074 * SYN-SENT -> SYN-RECEIVED 2075 * SYN-SENT* -> SYN-RECEIVED* 2076 */ 2077 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2078 tcp_timer_activate(tp, TT_REXMT, 0); 2079 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2080 } 2081 2082 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: " 2083 "ti_locked %d", __func__, ti_locked)); 2084 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2085 INP_WLOCK_ASSERT(tp->t_inpcb); 2086 2087 /* 2088 * Advance th->th_seq to correspond to first data byte. 2089 * If data, trim to stay within window, 2090 * dropping FIN if necessary. 2091 */ 2092 th->th_seq++; 2093 if (tlen > tp->rcv_wnd) { 2094 todrop = tlen - tp->rcv_wnd; 2095 m_adj(m, -todrop); 2096 tlen = tp->rcv_wnd; 2097 thflags &= ~TH_FIN; 2098 TCPSTAT_INC(tcps_rcvpackafterwin); 2099 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2100 } 2101 tp->snd_wl1 = th->th_seq - 1; 2102 tp->rcv_up = th->th_seq; 2103 /* 2104 * Client side of transaction: already sent SYN and data. 2105 * If the remote host used T/TCP to validate the SYN, 2106 * our data will be ACK'd; if so, enter normal data segment 2107 * processing in the middle of step 5, ack processing. 2108 * Otherwise, goto step 6. 2109 */ 2110 if (thflags & TH_ACK) 2111 goto process_ACK; 2112 2113 goto step6; 2114 2115 /* 2116 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2117 * do normal processing. 2118 * 2119 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2120 */ 2121 case TCPS_LAST_ACK: 2122 case TCPS_CLOSING: 2123 break; /* continue normal processing */ 2124 } 2125 2126 /* 2127 * States other than LISTEN or SYN_SENT. 2128 * First check the RST flag and sequence number since reset segments 2129 * are exempt from the timestamp and connection count tests. This 2130 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2131 * below which allowed reset segments in half the sequence space 2132 * to fall though and be processed (which gives forged reset 2133 * segments with a random sequence number a 50 percent chance of 2134 * killing a connection). 2135 * Then check timestamp, if present. 2136 * Then check the connection count, if present. 2137 * Then check that at least some bytes of segment are within 2138 * receive window. If segment begins before rcv_nxt, 2139 * drop leading data (and SYN); if nothing left, just ack. 2140 */ 2141 if (thflags & TH_RST) { 2142 /* 2143 * RFC5961 Section 3.2 2144 * 2145 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2146 * - If RST is in window, we send challenge ACK. 2147 * 2148 * Note: to take into account delayed ACKs, we should 2149 * test against last_ack_sent instead of rcv_nxt. 2150 * Note 2: we handle special case of closed window, not 2151 * covered by the RFC. 2152 */ 2153 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2154 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2155 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2156 2157 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2158 KASSERT(ti_locked == TI_RLOCKED, 2159 ("%s: TH_RST ti_locked %d, th %p tp %p", 2160 __func__, ti_locked, th, tp)); 2161 KASSERT(tp->t_state != TCPS_SYN_SENT, 2162 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2163 __func__, th, tp)); 2164 2165 if (V_tcp_insecure_rst || 2166 tp->last_ack_sent == th->th_seq) { 2167 TCPSTAT_INC(tcps_drops); 2168 /* Drop the connection. */ 2169 switch (tp->t_state) { 2170 case TCPS_SYN_RECEIVED: 2171 so->so_error = ECONNREFUSED; 2172 goto close; 2173 case TCPS_ESTABLISHED: 2174 case TCPS_FIN_WAIT_1: 2175 case TCPS_FIN_WAIT_2: 2176 case TCPS_CLOSE_WAIT: 2177 so->so_error = ECONNRESET; 2178 close: 2179 tcp_state_change(tp, TCPS_CLOSED); 2180 /* FALLTHROUGH */ 2181 default: 2182 tp = tcp_close(tp); 2183 } 2184 } else { 2185 TCPSTAT_INC(tcps_badrst); 2186 /* Send challenge ACK. */ 2187 tcp_respond(tp, mtod(m, void *), th, m, 2188 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2189 tp->last_ack_sent = tp->rcv_nxt; 2190 m = NULL; 2191 } 2192 } 2193 goto drop; 2194 } 2195 2196 /* 2197 * RFC5961 Section 4.2 2198 * Send challenge ACK for any SYN in synchronized state. 2199 */ 2200 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2201 tp->t_state != TCPS_SYN_RECEIVED) { 2202 KASSERT(ti_locked == TI_RLOCKED, 2203 ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked)); 2204 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2205 2206 TCPSTAT_INC(tcps_badsyn); 2207 if (V_tcp_insecure_syn && 2208 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2209 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2210 tp = tcp_drop(tp, ECONNRESET); 2211 rstreason = BANDLIM_UNLIMITED; 2212 } else { 2213 /* Send challenge ACK. */ 2214 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2215 tp->snd_nxt, TH_ACK); 2216 tp->last_ack_sent = tp->rcv_nxt; 2217 m = NULL; 2218 } 2219 goto drop; 2220 } 2221 2222 /* 2223 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2224 * and it's less than ts_recent, drop it. 2225 */ 2226 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2227 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2228 2229 /* Check to see if ts_recent is over 24 days old. */ 2230 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2231 /* 2232 * Invalidate ts_recent. If this segment updates 2233 * ts_recent, the age will be reset later and ts_recent 2234 * will get a valid value. If it does not, setting 2235 * ts_recent to zero will at least satisfy the 2236 * requirement that zero be placed in the timestamp 2237 * echo reply when ts_recent isn't valid. The 2238 * age isn't reset until we get a valid ts_recent 2239 * because we don't want out-of-order segments to be 2240 * dropped when ts_recent is old. 2241 */ 2242 tp->ts_recent = 0; 2243 } else { 2244 TCPSTAT_INC(tcps_rcvduppack); 2245 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2246 TCPSTAT_INC(tcps_pawsdrop); 2247 if (tlen) 2248 goto dropafterack; 2249 goto drop; 2250 } 2251 } 2252 2253 /* 2254 * In the SYN-RECEIVED state, validate that the packet belongs to 2255 * this connection before trimming the data to fit the receive 2256 * window. Check the sequence number versus IRS since we know 2257 * the sequence numbers haven't wrapped. This is a partial fix 2258 * for the "LAND" DoS attack. 2259 */ 2260 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2261 rstreason = BANDLIM_RST_OPENPORT; 2262 goto dropwithreset; 2263 } 2264 2265 todrop = tp->rcv_nxt - th->th_seq; 2266 if (todrop > 0) { 2267 if (thflags & TH_SYN) { 2268 thflags &= ~TH_SYN; 2269 th->th_seq++; 2270 if (th->th_urp > 1) 2271 th->th_urp--; 2272 else 2273 thflags &= ~TH_URG; 2274 todrop--; 2275 } 2276 /* 2277 * Following if statement from Stevens, vol. 2, p. 960. 2278 */ 2279 if (todrop > tlen 2280 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2281 /* 2282 * Any valid FIN must be to the left of the window. 2283 * At this point the FIN must be a duplicate or out 2284 * of sequence; drop it. 2285 */ 2286 thflags &= ~TH_FIN; 2287 2288 /* 2289 * Send an ACK to resynchronize and drop any data. 2290 * But keep on processing for RST or ACK. 2291 */ 2292 tp->t_flags |= TF_ACKNOW; 2293 todrop = tlen; 2294 TCPSTAT_INC(tcps_rcvduppack); 2295 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2296 } else { 2297 TCPSTAT_INC(tcps_rcvpartduppack); 2298 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2299 } 2300 drop_hdrlen += todrop; /* drop from the top afterwards */ 2301 th->th_seq += todrop; 2302 tlen -= todrop; 2303 if (th->th_urp > todrop) 2304 th->th_urp -= todrop; 2305 else { 2306 thflags &= ~TH_URG; 2307 th->th_urp = 0; 2308 } 2309 } 2310 2311 /* 2312 * If new data are received on a connection after the 2313 * user processes are gone, then RST the other end. 2314 */ 2315 if ((so->so_state & SS_NOFDREF) && 2316 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2317 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && " 2318 "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked)); 2319 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2320 2321 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2322 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2323 "after socket was closed, " 2324 "sending RST and removing tcpcb\n", 2325 s, __func__, tcpstates[tp->t_state], tlen); 2326 free(s, M_TCPLOG); 2327 } 2328 tp = tcp_close(tp); 2329 TCPSTAT_INC(tcps_rcvafterclose); 2330 rstreason = BANDLIM_UNLIMITED; 2331 goto dropwithreset; 2332 } 2333 2334 /* 2335 * If segment ends after window, drop trailing data 2336 * (and PUSH and FIN); if nothing left, just ACK. 2337 */ 2338 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2339 if (todrop > 0) { 2340 TCPSTAT_INC(tcps_rcvpackafterwin); 2341 if (todrop >= tlen) { 2342 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2343 /* 2344 * If window is closed can only take segments at 2345 * window edge, and have to drop data and PUSH from 2346 * incoming segments. Continue processing, but 2347 * remember to ack. Otherwise, drop segment 2348 * and ack. 2349 */ 2350 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2351 tp->t_flags |= TF_ACKNOW; 2352 TCPSTAT_INC(tcps_rcvwinprobe); 2353 } else 2354 goto dropafterack; 2355 } else 2356 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2357 m_adj(m, -todrop); 2358 tlen -= todrop; 2359 thflags &= ~(TH_PUSH|TH_FIN); 2360 } 2361 2362 /* 2363 * If last ACK falls within this segment's sequence numbers, 2364 * record its timestamp. 2365 * NOTE: 2366 * 1) That the test incorporates suggestions from the latest 2367 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2368 * 2) That updating only on newer timestamps interferes with 2369 * our earlier PAWS tests, so this check should be solely 2370 * predicated on the sequence space of this segment. 2371 * 3) That we modify the segment boundary check to be 2372 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2373 * instead of RFC1323's 2374 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2375 * This modified check allows us to overcome RFC1323's 2376 * limitations as described in Stevens TCP/IP Illustrated 2377 * Vol. 2 p.869. In such cases, we can still calculate the 2378 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2379 */ 2380 if ((to.to_flags & TOF_TS) != 0 && 2381 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2382 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2383 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2384 tp->ts_recent_age = tcp_ts_getticks(); 2385 tp->ts_recent = to.to_tsval; 2386 } 2387 2388 /* 2389 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2390 * flag is on (half-synchronized state), then queue data for 2391 * later processing; else drop segment and return. 2392 */ 2393 if ((thflags & TH_ACK) == 0) { 2394 if (tp->t_state == TCPS_SYN_RECEIVED || 2395 (tp->t_flags & TF_NEEDSYN)) { 2396 #ifdef TCP_RFC7413 2397 if (tp->t_state == TCPS_SYN_RECEIVED && 2398 tp->t_flags & TF_FASTOPEN) { 2399 tp->snd_wnd = tiwin; 2400 cc_conn_init(tp); 2401 } 2402 #endif 2403 goto step6; 2404 } else if (tp->t_flags & TF_ACKNOW) 2405 goto dropafterack; 2406 else 2407 goto drop; 2408 } 2409 2410 /* 2411 * Ack processing. 2412 */ 2413 switch (tp->t_state) { 2414 2415 /* 2416 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2417 * ESTABLISHED state and continue processing. 2418 * The ACK was checked above. 2419 */ 2420 case TCPS_SYN_RECEIVED: 2421 2422 TCPSTAT_INC(tcps_connects); 2423 soisconnected(so); 2424 /* Do window scaling? */ 2425 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2426 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2427 tp->rcv_scale = tp->request_r_scale; 2428 tp->snd_wnd = tiwin; 2429 } 2430 /* 2431 * Make transitions: 2432 * SYN-RECEIVED -> ESTABLISHED 2433 * SYN-RECEIVED* -> FIN-WAIT-1 2434 */ 2435 tp->t_starttime = ticks; 2436 if (tp->t_flags & TF_NEEDFIN) { 2437 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2438 tp->t_flags &= ~TF_NEEDFIN; 2439 } else { 2440 tcp_state_change(tp, TCPS_ESTABLISHED); 2441 TCP_PROBE5(accept__established, NULL, tp, 2442 mtod(m, const char *), tp, th); 2443 #ifdef TCP_RFC7413 2444 if (tp->t_tfo_pending) { 2445 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2446 tp->t_tfo_pending = NULL; 2447 2448 /* 2449 * Account for the ACK of our SYN prior to 2450 * regular ACK processing below. 2451 */ 2452 tp->snd_una++; 2453 } 2454 /* 2455 * TFO connections call cc_conn_init() during SYN 2456 * processing. Calling it again here for such 2457 * connections is not harmless as it would undo the 2458 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2459 * is retransmitted. 2460 */ 2461 if (!(tp->t_flags & TF_FASTOPEN)) 2462 #endif 2463 cc_conn_init(tp); 2464 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2465 } 2466 /* 2467 * If segment contains data or ACK, will call tcp_reass() 2468 * later; if not, do so now to pass queued data to user. 2469 */ 2470 if (tlen == 0 && (thflags & TH_FIN) == 0) 2471 (void) tcp_reass(tp, (struct tcphdr *)0, 0, 2472 (struct mbuf *)0); 2473 tp->snd_wl1 = th->th_seq - 1; 2474 /* FALLTHROUGH */ 2475 2476 /* 2477 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2478 * ACKs. If the ack is in the range 2479 * tp->snd_una < th->th_ack <= tp->snd_max 2480 * then advance tp->snd_una to th->th_ack and drop 2481 * data from the retransmission queue. If this ACK reflects 2482 * more up to date window information we update our window information. 2483 */ 2484 case TCPS_ESTABLISHED: 2485 case TCPS_FIN_WAIT_1: 2486 case TCPS_FIN_WAIT_2: 2487 case TCPS_CLOSE_WAIT: 2488 case TCPS_CLOSING: 2489 case TCPS_LAST_ACK: 2490 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2491 TCPSTAT_INC(tcps_rcvacktoomuch); 2492 goto dropafterack; 2493 } 2494 if ((tp->t_flags & TF_SACK_PERMIT) && 2495 ((to.to_flags & TOF_SACK) || 2496 !TAILQ_EMPTY(&tp->snd_holes))) 2497 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2498 else 2499 /* 2500 * Reset the value so that previous (valid) value 2501 * from the last ack with SACK doesn't get used. 2502 */ 2503 tp->sackhint.sacked_bytes = 0; 2504 2505 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2506 hhook_run_tcp_est_in(tp, th, &to); 2507 2508 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2509 u_int maxseg; 2510 2511 maxseg = tcp_maxseg(tp); 2512 if (tlen == 0 && 2513 (tiwin == tp->snd_wnd || 2514 (tp->t_flags & TF_SACK_PERMIT))) { 2515 /* 2516 * If this is the first time we've seen a 2517 * FIN from the remote, this is not a 2518 * duplicate and it needs to be processed 2519 * normally. This happens during a 2520 * simultaneous close. 2521 */ 2522 if ((thflags & TH_FIN) && 2523 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2524 tp->t_dupacks = 0; 2525 break; 2526 } 2527 TCPSTAT_INC(tcps_rcvdupack); 2528 /* 2529 * If we have outstanding data (other than 2530 * a window probe), this is a completely 2531 * duplicate ack (ie, window info didn't 2532 * change and FIN isn't set), 2533 * the ack is the biggest we've 2534 * seen and we've seen exactly our rexmt 2535 * threshold of them, assume a packet 2536 * has been dropped and retransmit it. 2537 * Kludge snd_nxt & the congestion 2538 * window so we send only this one 2539 * packet. 2540 * 2541 * We know we're losing at the current 2542 * window size so do congestion avoidance 2543 * (set ssthresh to half the current window 2544 * and pull our congestion window back to 2545 * the new ssthresh). 2546 * 2547 * Dup acks mean that packets have left the 2548 * network (they're now cached at the receiver) 2549 * so bump cwnd by the amount in the receiver 2550 * to keep a constant cwnd packets in the 2551 * network. 2552 * 2553 * When using TCP ECN, notify the peer that 2554 * we reduced the cwnd. 2555 */ 2556 /* 2557 * Following 2 kinds of acks should not affect 2558 * dupack counting: 2559 * 1) Old acks 2560 * 2) Acks with SACK but without any new SACK 2561 * information in them. These could result from 2562 * any anomaly in the network like a switch 2563 * duplicating packets or a possible DoS attack. 2564 */ 2565 if (th->th_ack != tp->snd_una || 2566 ((tp->t_flags & TF_SACK_PERMIT) && 2567 !sack_changed)) 2568 break; 2569 else if (!tcp_timer_active(tp, TT_REXMT)) 2570 tp->t_dupacks = 0; 2571 else if (++tp->t_dupacks > tcprexmtthresh || 2572 IN_FASTRECOVERY(tp->t_flags)) { 2573 cc_ack_received(tp, th, CC_DUPACK); 2574 if ((tp->t_flags & TF_SACK_PERMIT) && 2575 IN_FASTRECOVERY(tp->t_flags)) { 2576 int awnd; 2577 2578 /* 2579 * Compute the amount of data in flight first. 2580 * We can inject new data into the pipe iff 2581 * we have less than 1/2 the original window's 2582 * worth of data in flight. 2583 */ 2584 if (V_tcp_do_rfc6675_pipe) 2585 awnd = tcp_compute_pipe(tp); 2586 else 2587 awnd = (tp->snd_nxt - tp->snd_fack) + 2588 tp->sackhint.sack_bytes_rexmit; 2589 2590 if (awnd < tp->snd_ssthresh) { 2591 tp->snd_cwnd += maxseg; 2592 if (tp->snd_cwnd > tp->snd_ssthresh) 2593 tp->snd_cwnd = tp->snd_ssthresh; 2594 } 2595 } else 2596 tp->snd_cwnd += maxseg; 2597 (void) tp->t_fb->tfb_tcp_output(tp); 2598 goto drop; 2599 } else if (tp->t_dupacks == tcprexmtthresh) { 2600 tcp_seq onxt = tp->snd_nxt; 2601 2602 /* 2603 * If we're doing sack, check to 2604 * see if we're already in sack 2605 * recovery. If we're not doing sack, 2606 * check to see if we're in newreno 2607 * recovery. 2608 */ 2609 if (tp->t_flags & TF_SACK_PERMIT) { 2610 if (IN_FASTRECOVERY(tp->t_flags)) { 2611 tp->t_dupacks = 0; 2612 break; 2613 } 2614 } else { 2615 if (SEQ_LEQ(th->th_ack, 2616 tp->snd_recover)) { 2617 tp->t_dupacks = 0; 2618 break; 2619 } 2620 } 2621 /* Congestion signal before ack. */ 2622 cc_cong_signal(tp, th, CC_NDUPACK); 2623 cc_ack_received(tp, th, CC_DUPACK); 2624 tcp_timer_activate(tp, TT_REXMT, 0); 2625 tp->t_rtttime = 0; 2626 if (tp->t_flags & TF_SACK_PERMIT) { 2627 TCPSTAT_INC( 2628 tcps_sack_recovery_episode); 2629 tp->sack_newdata = tp->snd_nxt; 2630 tp->snd_cwnd = maxseg; 2631 (void) tp->t_fb->tfb_tcp_output(tp); 2632 goto drop; 2633 } 2634 tp->snd_nxt = th->th_ack; 2635 tp->snd_cwnd = maxseg; 2636 (void) tp->t_fb->tfb_tcp_output(tp); 2637 KASSERT(tp->snd_limited <= 2, 2638 ("%s: tp->snd_limited too big", 2639 __func__)); 2640 tp->snd_cwnd = tp->snd_ssthresh + 2641 maxseg * 2642 (tp->t_dupacks - tp->snd_limited); 2643 if (SEQ_GT(onxt, tp->snd_nxt)) 2644 tp->snd_nxt = onxt; 2645 goto drop; 2646 } else if (V_tcp_do_rfc3042) { 2647 /* 2648 * Process first and second duplicate 2649 * ACKs. Each indicates a segment 2650 * leaving the network, creating room 2651 * for more. Make sure we can send a 2652 * packet on reception of each duplicate 2653 * ACK by increasing snd_cwnd by one 2654 * segment. Restore the original 2655 * snd_cwnd after packet transmission. 2656 */ 2657 cc_ack_received(tp, th, CC_DUPACK); 2658 u_long oldcwnd = tp->snd_cwnd; 2659 tcp_seq oldsndmax = tp->snd_max; 2660 u_int sent; 2661 int avail; 2662 2663 KASSERT(tp->t_dupacks == 1 || 2664 tp->t_dupacks == 2, 2665 ("%s: dupacks not 1 or 2", 2666 __func__)); 2667 if (tp->t_dupacks == 1) 2668 tp->snd_limited = 0; 2669 tp->snd_cwnd = 2670 (tp->snd_nxt - tp->snd_una) + 2671 (tp->t_dupacks - tp->snd_limited) * 2672 maxseg; 2673 /* 2674 * Only call tcp_output when there 2675 * is new data available to be sent. 2676 * Otherwise we would send pure ACKs. 2677 */ 2678 SOCKBUF_LOCK(&so->so_snd); 2679 avail = sbavail(&so->so_snd) - 2680 (tp->snd_nxt - tp->snd_una); 2681 SOCKBUF_UNLOCK(&so->so_snd); 2682 if (avail > 0) 2683 (void) tp->t_fb->tfb_tcp_output(tp); 2684 sent = tp->snd_max - oldsndmax; 2685 if (sent > maxseg) { 2686 KASSERT((tp->t_dupacks == 2 && 2687 tp->snd_limited == 0) || 2688 (sent == maxseg + 1 && 2689 tp->t_flags & TF_SENTFIN), 2690 ("%s: sent too much", 2691 __func__)); 2692 tp->snd_limited = 2; 2693 } else if (sent > 0) 2694 ++tp->snd_limited; 2695 tp->snd_cwnd = oldcwnd; 2696 goto drop; 2697 } 2698 } 2699 break; 2700 } else { 2701 /* 2702 * This ack is advancing the left edge, reset the 2703 * counter. 2704 */ 2705 tp->t_dupacks = 0; 2706 /* 2707 * If this ack also has new SACK info, increment the 2708 * counter as per rfc6675. 2709 */ 2710 if ((tp->t_flags & TF_SACK_PERMIT) && sack_changed) 2711 tp->t_dupacks++; 2712 } 2713 2714 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2715 ("%s: th_ack <= snd_una", __func__)); 2716 2717 /* 2718 * If the congestion window was inflated to account 2719 * for the other side's cached packets, retract it. 2720 */ 2721 if (IN_FASTRECOVERY(tp->t_flags)) { 2722 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2723 if (tp->t_flags & TF_SACK_PERMIT) 2724 tcp_sack_partialack(tp, th); 2725 else 2726 tcp_newreno_partial_ack(tp, th); 2727 } else 2728 cc_post_recovery(tp, th); 2729 } 2730 /* 2731 * If we reach this point, ACK is not a duplicate, 2732 * i.e., it ACKs something we sent. 2733 */ 2734 if (tp->t_flags & TF_NEEDSYN) { 2735 /* 2736 * T/TCP: Connection was half-synchronized, and our 2737 * SYN has been ACK'd (so connection is now fully 2738 * synchronized). Go to non-starred state, 2739 * increment snd_una for ACK of SYN, and check if 2740 * we can do window scaling. 2741 */ 2742 tp->t_flags &= ~TF_NEEDSYN; 2743 tp->snd_una++; 2744 /* Do window scaling? */ 2745 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2746 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2747 tp->rcv_scale = tp->request_r_scale; 2748 /* Send window already scaled. */ 2749 } 2750 } 2751 2752 process_ACK: 2753 INP_WLOCK_ASSERT(tp->t_inpcb); 2754 2755 acked = BYTES_THIS_ACK(tp, th); 2756 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2757 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2758 tp->snd_una, th->th_ack, tp, m)); 2759 TCPSTAT_INC(tcps_rcvackpack); 2760 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2761 2762 /* 2763 * If we just performed our first retransmit, and the ACK 2764 * arrives within our recovery window, then it was a mistake 2765 * to do the retransmit in the first place. Recover our 2766 * original cwnd and ssthresh, and proceed to transmit where 2767 * we left off. 2768 */ 2769 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID && 2770 (int)(ticks - tp->t_badrxtwin) < 0) 2771 cc_cong_signal(tp, th, CC_RTO_ERR); 2772 2773 /* 2774 * If we have a timestamp reply, update smoothed 2775 * round trip time. If no timestamp is present but 2776 * transmit timer is running and timed sequence 2777 * number was acked, update smoothed round trip time. 2778 * Since we now have an rtt measurement, cancel the 2779 * timer backoff (cf., Phil Karn's retransmit alg.). 2780 * Recompute the initial retransmit timer. 2781 * 2782 * Some boxes send broken timestamp replies 2783 * during the SYN+ACK phase, ignore 2784 * timestamps of 0 or we could calculate a 2785 * huge RTT and blow up the retransmit timer. 2786 */ 2787 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2788 u_int t; 2789 2790 t = tcp_ts_getticks() - to.to_tsecr; 2791 if (!tp->t_rttlow || tp->t_rttlow > t) 2792 tp->t_rttlow = t; 2793 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2794 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2795 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2796 tp->t_rttlow = ticks - tp->t_rtttime; 2797 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2798 } 2799 2800 /* 2801 * If all outstanding data is acked, stop retransmit 2802 * timer and remember to restart (more output or persist). 2803 * If there is more data to be acked, restart retransmit 2804 * timer, using current (possibly backed-off) value. 2805 */ 2806 if (th->th_ack == tp->snd_max) { 2807 tcp_timer_activate(tp, TT_REXMT, 0); 2808 needoutput = 1; 2809 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2810 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2811 2812 /* 2813 * If no data (only SYN) was ACK'd, 2814 * skip rest of ACK processing. 2815 */ 2816 if (acked == 0) 2817 goto step6; 2818 2819 /* 2820 * Let the congestion control algorithm update congestion 2821 * control related information. This typically means increasing 2822 * the congestion window. 2823 */ 2824 cc_ack_received(tp, th, CC_ACK); 2825 2826 SOCKBUF_LOCK(&so->so_snd); 2827 if (acked > sbavail(&so->so_snd)) { 2828 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2829 tp->snd_wnd -= sbavail(&so->so_snd); 2830 else 2831 tp->snd_wnd = 0; 2832 mfree = sbcut_locked(&so->so_snd, 2833 (int)sbavail(&so->so_snd)); 2834 ourfinisacked = 1; 2835 } else { 2836 mfree = sbcut_locked(&so->so_snd, acked); 2837 if (tp->snd_wnd >= (u_long) acked) 2838 tp->snd_wnd -= acked; 2839 else 2840 tp->snd_wnd = 0; 2841 ourfinisacked = 0; 2842 } 2843 /* NB: sowwakeup_locked() does an implicit unlock. */ 2844 sowwakeup_locked(so); 2845 m_freem(mfree); 2846 /* Detect una wraparound. */ 2847 if (!IN_RECOVERY(tp->t_flags) && 2848 SEQ_GT(tp->snd_una, tp->snd_recover) && 2849 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2850 tp->snd_recover = th->th_ack - 1; 2851 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2852 if (IN_RECOVERY(tp->t_flags) && 2853 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2854 EXIT_RECOVERY(tp->t_flags); 2855 } 2856 tp->snd_una = th->th_ack; 2857 if (tp->t_flags & TF_SACK_PERMIT) { 2858 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2859 tp->snd_recover = tp->snd_una; 2860 } 2861 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2862 tp->snd_nxt = tp->snd_una; 2863 2864 switch (tp->t_state) { 2865 2866 /* 2867 * In FIN_WAIT_1 STATE in addition to the processing 2868 * for the ESTABLISHED state if our FIN is now acknowledged 2869 * then enter FIN_WAIT_2. 2870 */ 2871 case TCPS_FIN_WAIT_1: 2872 if (ourfinisacked) { 2873 /* 2874 * If we can't receive any more 2875 * data, then closing user can proceed. 2876 * Starting the timer is contrary to the 2877 * specification, but if we don't get a FIN 2878 * we'll hang forever. 2879 * 2880 * XXXjl: 2881 * we should release the tp also, and use a 2882 * compressed state. 2883 */ 2884 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2885 soisdisconnected(so); 2886 tcp_timer_activate(tp, TT_2MSL, 2887 (tcp_fast_finwait2_recycle ? 2888 tcp_finwait2_timeout : 2889 TP_MAXIDLE(tp))); 2890 } 2891 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2892 } 2893 break; 2894 2895 /* 2896 * In CLOSING STATE in addition to the processing for 2897 * the ESTABLISHED state if the ACK acknowledges our FIN 2898 * then enter the TIME-WAIT state, otherwise ignore 2899 * the segment. 2900 */ 2901 case TCPS_CLOSING: 2902 if (ourfinisacked) { 2903 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2904 tcp_twstart(tp); 2905 INP_INFO_RUNLOCK(&V_tcbinfo); 2906 m_freem(m); 2907 return; 2908 } 2909 break; 2910 2911 /* 2912 * In LAST_ACK, we may still be waiting for data to drain 2913 * and/or to be acked, as well as for the ack of our FIN. 2914 * If our FIN is now acknowledged, delete the TCB, 2915 * enter the closed state and return. 2916 */ 2917 case TCPS_LAST_ACK: 2918 if (ourfinisacked) { 2919 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 2920 tp = tcp_close(tp); 2921 goto drop; 2922 } 2923 break; 2924 } 2925 } 2926 2927 step6: 2928 INP_WLOCK_ASSERT(tp->t_inpcb); 2929 2930 /* 2931 * Update window information. 2932 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2933 */ 2934 if ((thflags & TH_ACK) && 2935 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2936 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2937 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2938 /* keep track of pure window updates */ 2939 if (tlen == 0 && 2940 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2941 TCPSTAT_INC(tcps_rcvwinupd); 2942 tp->snd_wnd = tiwin; 2943 tp->snd_wl1 = th->th_seq; 2944 tp->snd_wl2 = th->th_ack; 2945 if (tp->snd_wnd > tp->max_sndwnd) 2946 tp->max_sndwnd = tp->snd_wnd; 2947 needoutput = 1; 2948 } 2949 2950 /* 2951 * Process segments with URG. 2952 */ 2953 if ((thflags & TH_URG) && th->th_urp && 2954 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2955 /* 2956 * This is a kludge, but if we receive and accept 2957 * random urgent pointers, we'll crash in 2958 * soreceive. It's hard to imagine someone 2959 * actually wanting to send this much urgent data. 2960 */ 2961 SOCKBUF_LOCK(&so->so_rcv); 2962 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2963 th->th_urp = 0; /* XXX */ 2964 thflags &= ~TH_URG; /* XXX */ 2965 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2966 goto dodata; /* XXX */ 2967 } 2968 /* 2969 * If this segment advances the known urgent pointer, 2970 * then mark the data stream. This should not happen 2971 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2972 * a FIN has been received from the remote side. 2973 * In these states we ignore the URG. 2974 * 2975 * According to RFC961 (Assigned Protocols), 2976 * the urgent pointer points to the last octet 2977 * of urgent data. We continue, however, 2978 * to consider it to indicate the first octet 2979 * of data past the urgent section as the original 2980 * spec states (in one of two places). 2981 */ 2982 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2983 tp->rcv_up = th->th_seq + th->th_urp; 2984 so->so_oobmark = sbavail(&so->so_rcv) + 2985 (tp->rcv_up - tp->rcv_nxt) - 1; 2986 if (so->so_oobmark == 0) 2987 so->so_rcv.sb_state |= SBS_RCVATMARK; 2988 sohasoutofband(so); 2989 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2990 } 2991 SOCKBUF_UNLOCK(&so->so_rcv); 2992 /* 2993 * Remove out of band data so doesn't get presented to user. 2994 * This can happen independent of advancing the URG pointer, 2995 * but if two URG's are pending at once, some out-of-band 2996 * data may creep in... ick. 2997 */ 2998 if (th->th_urp <= (u_long)tlen && 2999 !(so->so_options & SO_OOBINLINE)) { 3000 /* hdr drop is delayed */ 3001 tcp_pulloutofband(so, th, m, drop_hdrlen); 3002 } 3003 } else { 3004 /* 3005 * If no out of band data is expected, 3006 * pull receive urgent pointer along 3007 * with the receive window. 3008 */ 3009 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 3010 tp->rcv_up = tp->rcv_nxt; 3011 } 3012 dodata: /* XXX */ 3013 INP_WLOCK_ASSERT(tp->t_inpcb); 3014 3015 /* 3016 * Process the segment text, merging it into the TCP sequencing queue, 3017 * and arranging for acknowledgment of receipt if necessary. 3018 * This process logically involves adjusting tp->rcv_wnd as data 3019 * is presented to the user (this happens in tcp_usrreq.c, 3020 * case PRU_RCVD). If a FIN has already been received on this 3021 * connection then we just ignore the text. 3022 */ 3023 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3024 (tp->t_flags & TF_FASTOPEN)); 3025 if ((tlen || (thflags & TH_FIN) || tfo_syn) && 3026 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3027 tcp_seq save_start = th->th_seq; 3028 m_adj(m, drop_hdrlen); /* delayed header drop */ 3029 /* 3030 * Insert segment which includes th into TCP reassembly queue 3031 * with control block tp. Set thflags to whether reassembly now 3032 * includes a segment with FIN. This handles the common case 3033 * inline (segment is the next to be received on an established 3034 * connection, and the queue is empty), avoiding linkage into 3035 * and removal from the queue and repetition of various 3036 * conversions. 3037 * Set DELACK for segments received in order, but ack 3038 * immediately when segments are out of order (so 3039 * fast retransmit can work). 3040 */ 3041 if (th->th_seq == tp->rcv_nxt && 3042 LIST_EMPTY(&tp->t_segq) && 3043 (TCPS_HAVEESTABLISHED(tp->t_state) || 3044 tfo_syn)) { 3045 if (DELAY_ACK(tp, tlen) || tfo_syn) 3046 tp->t_flags |= TF_DELACK; 3047 else 3048 tp->t_flags |= TF_ACKNOW; 3049 tp->rcv_nxt += tlen; 3050 thflags = th->th_flags & TH_FIN; 3051 TCPSTAT_INC(tcps_rcvpack); 3052 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3053 SOCKBUF_LOCK(&so->so_rcv); 3054 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3055 m_freem(m); 3056 else 3057 sbappendstream_locked(&so->so_rcv, m, 0); 3058 /* NB: sorwakeup_locked() does an implicit unlock. */ 3059 sorwakeup_locked(so); 3060 } else { 3061 /* 3062 * XXX: Due to the header drop above "th" is 3063 * theoretically invalid by now. Fortunately 3064 * m_adj() doesn't actually frees any mbufs 3065 * when trimming from the head. 3066 */ 3067 thflags = tcp_reass(tp, th, &tlen, m); 3068 tp->t_flags |= TF_ACKNOW; 3069 } 3070 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT)) 3071 tcp_update_sack_list(tp, save_start, save_start + tlen); 3072 #if 0 3073 /* 3074 * Note the amount of data that peer has sent into 3075 * our window, in order to estimate the sender's 3076 * buffer size. 3077 * XXX: Unused. 3078 */ 3079 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3080 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3081 else 3082 len = so->so_rcv.sb_hiwat; 3083 #endif 3084 } else { 3085 m_freem(m); 3086 thflags &= ~TH_FIN; 3087 } 3088 3089 /* 3090 * If FIN is received ACK the FIN and let the user know 3091 * that the connection is closing. 3092 */ 3093 if (thflags & TH_FIN) { 3094 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3095 socantrcvmore(so); 3096 /* 3097 * If connection is half-synchronized 3098 * (ie NEEDSYN flag on) then delay ACK, 3099 * so it may be piggybacked when SYN is sent. 3100 * Otherwise, since we received a FIN then no 3101 * more input can be expected, send ACK now. 3102 */ 3103 if (tp->t_flags & TF_NEEDSYN) 3104 tp->t_flags |= TF_DELACK; 3105 else 3106 tp->t_flags |= TF_ACKNOW; 3107 tp->rcv_nxt++; 3108 } 3109 switch (tp->t_state) { 3110 3111 /* 3112 * In SYN_RECEIVED and ESTABLISHED STATES 3113 * enter the CLOSE_WAIT state. 3114 */ 3115 case TCPS_SYN_RECEIVED: 3116 tp->t_starttime = ticks; 3117 /* FALLTHROUGH */ 3118 case TCPS_ESTABLISHED: 3119 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3120 break; 3121 3122 /* 3123 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3124 * enter the CLOSING state. 3125 */ 3126 case TCPS_FIN_WAIT_1: 3127 tcp_state_change(tp, TCPS_CLOSING); 3128 break; 3129 3130 /* 3131 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3132 * starting the time-wait timer, turning off the other 3133 * standard timers. 3134 */ 3135 case TCPS_FIN_WAIT_2: 3136 INP_INFO_RLOCK_ASSERT(&V_tcbinfo); 3137 KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata " 3138 "TCP_FIN_WAIT_2 ti_locked: %d", __func__, 3139 ti_locked)); 3140 3141 tcp_twstart(tp); 3142 INP_INFO_RUNLOCK(&V_tcbinfo); 3143 return; 3144 } 3145 } 3146 if (ti_locked == TI_RLOCKED) 3147 INP_INFO_RUNLOCK(&V_tcbinfo); 3148 ti_locked = TI_UNLOCKED; 3149 3150 #ifdef TCPDEBUG 3151 if (so->so_options & SO_DEBUG) 3152 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3153 &tcp_savetcp, 0); 3154 #endif 3155 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3156 3157 /* 3158 * Return any desired output. 3159 */ 3160 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3161 (void) tp->t_fb->tfb_tcp_output(tp); 3162 3163 check_delack: 3164 KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d", 3165 __func__, ti_locked)); 3166 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3167 INP_WLOCK_ASSERT(tp->t_inpcb); 3168 3169 if (tp->t_flags & TF_DELACK) { 3170 tp->t_flags &= ~TF_DELACK; 3171 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3172 } 3173 INP_WUNLOCK(tp->t_inpcb); 3174 return; 3175 3176 dropafterack: 3177 /* 3178 * Generate an ACK dropping incoming segment if it occupies 3179 * sequence space, where the ACK reflects our state. 3180 * 3181 * We can now skip the test for the RST flag since all 3182 * paths to this code happen after packets containing 3183 * RST have been dropped. 3184 * 3185 * In the SYN-RECEIVED state, don't send an ACK unless the 3186 * segment we received passes the SYN-RECEIVED ACK test. 3187 * If it fails send a RST. This breaks the loop in the 3188 * "LAND" DoS attack, and also prevents an ACK storm 3189 * between two listening ports that have been sent forged 3190 * SYN segments, each with the source address of the other. 3191 */ 3192 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3193 (SEQ_GT(tp->snd_una, th->th_ack) || 3194 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3195 rstreason = BANDLIM_RST_OPENPORT; 3196 goto dropwithreset; 3197 } 3198 #ifdef TCPDEBUG 3199 if (so->so_options & SO_DEBUG) 3200 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3201 &tcp_savetcp, 0); 3202 #endif 3203 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3204 if (ti_locked == TI_RLOCKED) 3205 INP_INFO_RUNLOCK(&V_tcbinfo); 3206 ti_locked = TI_UNLOCKED; 3207 3208 tp->t_flags |= TF_ACKNOW; 3209 (void) tp->t_fb->tfb_tcp_output(tp); 3210 INP_WUNLOCK(tp->t_inpcb); 3211 m_freem(m); 3212 return; 3213 3214 dropwithreset: 3215 if (ti_locked == TI_RLOCKED) 3216 INP_INFO_RUNLOCK(&V_tcbinfo); 3217 ti_locked = TI_UNLOCKED; 3218 3219 if (tp != NULL) { 3220 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3221 INP_WUNLOCK(tp->t_inpcb); 3222 } else 3223 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3224 return; 3225 3226 drop: 3227 if (ti_locked == TI_RLOCKED) { 3228 INP_INFO_RUNLOCK(&V_tcbinfo); 3229 ti_locked = TI_UNLOCKED; 3230 } 3231 #ifdef INVARIANTS 3232 else 3233 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo); 3234 #endif 3235 3236 /* 3237 * Drop space held by incoming segment and return. 3238 */ 3239 #ifdef TCPDEBUG 3240 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3241 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3242 &tcp_savetcp, 0); 3243 #endif 3244 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *)); 3245 if (tp != NULL) 3246 INP_WUNLOCK(tp->t_inpcb); 3247 m_freem(m); 3248 } 3249 3250 /* 3251 * Issue RST and make ACK acceptable to originator of segment. 3252 * The mbuf must still include the original packet header. 3253 * tp may be NULL. 3254 */ 3255 void 3256 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3257 int tlen, int rstreason) 3258 { 3259 #ifdef INET 3260 struct ip *ip; 3261 #endif 3262 #ifdef INET6 3263 struct ip6_hdr *ip6; 3264 #endif 3265 3266 if (tp != NULL) { 3267 INP_WLOCK_ASSERT(tp->t_inpcb); 3268 } 3269 3270 /* Don't bother if destination was broadcast/multicast. */ 3271 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3272 goto drop; 3273 #ifdef INET6 3274 if (mtod(m, struct ip *)->ip_v == 6) { 3275 ip6 = mtod(m, struct ip6_hdr *); 3276 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3277 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3278 goto drop; 3279 /* IPv6 anycast check is done at tcp6_input() */ 3280 } 3281 #endif 3282 #if defined(INET) && defined(INET6) 3283 else 3284 #endif 3285 #ifdef INET 3286 { 3287 ip = mtod(m, struct ip *); 3288 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3289 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3290 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3291 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3292 goto drop; 3293 } 3294 #endif 3295 3296 /* Perform bandwidth limiting. */ 3297 if (badport_bandlim(rstreason) < 0) 3298 goto drop; 3299 3300 /* tcp_respond consumes the mbuf chain. */ 3301 if (th->th_flags & TH_ACK) { 3302 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3303 th->th_ack, TH_RST); 3304 } else { 3305 if (th->th_flags & TH_SYN) 3306 tlen++; 3307 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3308 (tcp_seq)0, TH_RST|TH_ACK); 3309 } 3310 return; 3311 drop: 3312 m_freem(m); 3313 } 3314 3315 /* 3316 * Parse TCP options and place in tcpopt. 3317 */ 3318 void 3319 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3320 { 3321 int opt, optlen; 3322 3323 to->to_flags = 0; 3324 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3325 opt = cp[0]; 3326 if (opt == TCPOPT_EOL) 3327 break; 3328 if (opt == TCPOPT_NOP) 3329 optlen = 1; 3330 else { 3331 if (cnt < 2) 3332 break; 3333 optlen = cp[1]; 3334 if (optlen < 2 || optlen > cnt) 3335 break; 3336 } 3337 switch (opt) { 3338 case TCPOPT_MAXSEG: 3339 if (optlen != TCPOLEN_MAXSEG) 3340 continue; 3341 if (!(flags & TO_SYN)) 3342 continue; 3343 to->to_flags |= TOF_MSS; 3344 bcopy((char *)cp + 2, 3345 (char *)&to->to_mss, sizeof(to->to_mss)); 3346 to->to_mss = ntohs(to->to_mss); 3347 break; 3348 case TCPOPT_WINDOW: 3349 if (optlen != TCPOLEN_WINDOW) 3350 continue; 3351 if (!(flags & TO_SYN)) 3352 continue; 3353 to->to_flags |= TOF_SCALE; 3354 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3355 break; 3356 case TCPOPT_TIMESTAMP: 3357 if (optlen != TCPOLEN_TIMESTAMP) 3358 continue; 3359 to->to_flags |= TOF_TS; 3360 bcopy((char *)cp + 2, 3361 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3362 to->to_tsval = ntohl(to->to_tsval); 3363 bcopy((char *)cp + 6, 3364 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3365 to->to_tsecr = ntohl(to->to_tsecr); 3366 break; 3367 #ifdef TCP_SIGNATURE 3368 /* 3369 * XXX In order to reply to a host which has set the 3370 * TCP_SIGNATURE option in its initial SYN, we have to 3371 * record the fact that the option was observed here 3372 * for the syncache code to perform the correct response. 3373 */ 3374 case TCPOPT_SIGNATURE: 3375 if (optlen != TCPOLEN_SIGNATURE) 3376 continue; 3377 to->to_flags |= TOF_SIGNATURE; 3378 to->to_signature = cp + 2; 3379 break; 3380 #endif 3381 case TCPOPT_SACK_PERMITTED: 3382 if (optlen != TCPOLEN_SACK_PERMITTED) 3383 continue; 3384 if (!(flags & TO_SYN)) 3385 continue; 3386 if (!V_tcp_do_sack) 3387 continue; 3388 to->to_flags |= TOF_SACKPERM; 3389 break; 3390 case TCPOPT_SACK: 3391 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3392 continue; 3393 if (flags & TO_SYN) 3394 continue; 3395 to->to_flags |= TOF_SACK; 3396 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3397 to->to_sacks = cp + 2; 3398 TCPSTAT_INC(tcps_sack_rcv_blocks); 3399 break; 3400 #ifdef TCP_RFC7413 3401 case TCPOPT_FAST_OPEN: 3402 if ((optlen != TCPOLEN_FAST_OPEN_EMPTY) && 3403 (optlen < TCPOLEN_FAST_OPEN_MIN) && 3404 (optlen > TCPOLEN_FAST_OPEN_MAX)) 3405 continue; 3406 if (!(flags & TO_SYN)) 3407 continue; 3408 if (!V_tcp_fastopen_enabled) 3409 continue; 3410 to->to_flags |= TOF_FASTOPEN; 3411 to->to_tfo_len = optlen - 2; 3412 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3413 break; 3414 #endif 3415 default: 3416 continue; 3417 } 3418 } 3419 } 3420 3421 /* 3422 * Pull out of band byte out of a segment so 3423 * it doesn't appear in the user's data queue. 3424 * It is still reflected in the segment length for 3425 * sequencing purposes. 3426 */ 3427 void 3428 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3429 int off) 3430 { 3431 int cnt = off + th->th_urp - 1; 3432 3433 while (cnt >= 0) { 3434 if (m->m_len > cnt) { 3435 char *cp = mtod(m, caddr_t) + cnt; 3436 struct tcpcb *tp = sototcpcb(so); 3437 3438 INP_WLOCK_ASSERT(tp->t_inpcb); 3439 3440 tp->t_iobc = *cp; 3441 tp->t_oobflags |= TCPOOB_HAVEDATA; 3442 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3443 m->m_len--; 3444 if (m->m_flags & M_PKTHDR) 3445 m->m_pkthdr.len--; 3446 return; 3447 } 3448 cnt -= m->m_len; 3449 m = m->m_next; 3450 if (m == NULL) 3451 break; 3452 } 3453 panic("tcp_pulloutofband"); 3454 } 3455 3456 /* 3457 * Collect new round-trip time estimate 3458 * and update averages and current timeout. 3459 */ 3460 void 3461 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3462 { 3463 int delta; 3464 3465 INP_WLOCK_ASSERT(tp->t_inpcb); 3466 3467 TCPSTAT_INC(tcps_rttupdated); 3468 tp->t_rttupdated++; 3469 if (tp->t_srtt != 0) { 3470 /* 3471 * srtt is stored as fixed point with 5 bits after the 3472 * binary point (i.e., scaled by 8). The following magic 3473 * is equivalent to the smoothing algorithm in rfc793 with 3474 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3475 * point). Adjust rtt to origin 0. 3476 */ 3477 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3478 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3479 3480 if ((tp->t_srtt += delta) <= 0) 3481 tp->t_srtt = 1; 3482 3483 /* 3484 * We accumulate a smoothed rtt variance (actually, a 3485 * smoothed mean difference), then set the retransmit 3486 * timer to smoothed rtt + 4 times the smoothed variance. 3487 * rttvar is stored as fixed point with 4 bits after the 3488 * binary point (scaled by 16). The following is 3489 * equivalent to rfc793 smoothing with an alpha of .75 3490 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3491 * rfc793's wired-in beta. 3492 */ 3493 if (delta < 0) 3494 delta = -delta; 3495 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3496 if ((tp->t_rttvar += delta) <= 0) 3497 tp->t_rttvar = 1; 3498 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3499 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3500 } else { 3501 /* 3502 * No rtt measurement yet - use the unsmoothed rtt. 3503 * Set the variance to half the rtt (so our first 3504 * retransmit happens at 3*rtt). 3505 */ 3506 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3507 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3508 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3509 } 3510 tp->t_rtttime = 0; 3511 tp->t_rxtshift = 0; 3512 3513 /* 3514 * the retransmit should happen at rtt + 4 * rttvar. 3515 * Because of the way we do the smoothing, srtt and rttvar 3516 * will each average +1/2 tick of bias. When we compute 3517 * the retransmit timer, we want 1/2 tick of rounding and 3518 * 1 extra tick because of +-1/2 tick uncertainty in the 3519 * firing of the timer. The bias will give us exactly the 3520 * 1.5 tick we need. But, because the bias is 3521 * statistical, we have to test that we don't drop below 3522 * the minimum feasible timer (which is 2 ticks). 3523 */ 3524 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3525 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3526 3527 /* 3528 * We received an ack for a packet that wasn't retransmitted; 3529 * it is probably safe to discard any error indications we've 3530 * received recently. This isn't quite right, but close enough 3531 * for now (a route might have failed after we sent a segment, 3532 * and the return path might not be symmetrical). 3533 */ 3534 tp->t_softerror = 0; 3535 } 3536 3537 /* 3538 * Determine a reasonable value for maxseg size. 3539 * If the route is known, check route for mtu. 3540 * If none, use an mss that can be handled on the outgoing interface 3541 * without forcing IP to fragment. If no route is found, route has no mtu, 3542 * or the destination isn't local, use a default, hopefully conservative 3543 * size (usually 512 or the default IP max size, but no more than the mtu 3544 * of the interface), as we can't discover anything about intervening 3545 * gateways or networks. We also initialize the congestion/slow start 3546 * window to be a single segment if the destination isn't local. 3547 * While looking at the routing entry, we also initialize other path-dependent 3548 * parameters from pre-set or cached values in the routing entry. 3549 * 3550 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3551 * IP options, e.g. IPSEC data, since length of this data may vary, and 3552 * thus it is calculated for every segment separately in tcp_output(). 3553 * 3554 * NOTE that this routine is only called when we process an incoming 3555 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3556 * settings are handled in tcp_mssopt(). 3557 */ 3558 void 3559 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3560 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3561 { 3562 int mss = 0; 3563 u_long maxmtu = 0; 3564 struct inpcb *inp = tp->t_inpcb; 3565 struct hc_metrics_lite metrics; 3566 #ifdef INET6 3567 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3568 size_t min_protoh = isipv6 ? 3569 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3570 sizeof (struct tcpiphdr); 3571 #else 3572 const size_t min_protoh = sizeof(struct tcpiphdr); 3573 #endif 3574 3575 INP_WLOCK_ASSERT(tp->t_inpcb); 3576 3577 if (mtuoffer != -1) { 3578 KASSERT(offer == -1, ("%s: conflict", __func__)); 3579 offer = mtuoffer - min_protoh; 3580 } 3581 3582 /* Initialize. */ 3583 #ifdef INET6 3584 if (isipv6) { 3585 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3586 tp->t_maxseg = V_tcp_v6mssdflt; 3587 } 3588 #endif 3589 #if defined(INET) && defined(INET6) 3590 else 3591 #endif 3592 #ifdef INET 3593 { 3594 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3595 tp->t_maxseg = V_tcp_mssdflt; 3596 } 3597 #endif 3598 3599 /* 3600 * No route to sender, stay with default mss and return. 3601 */ 3602 if (maxmtu == 0) { 3603 /* 3604 * In case we return early we need to initialize metrics 3605 * to a defined state as tcp_hc_get() would do for us 3606 * if there was no cache hit. 3607 */ 3608 if (metricptr != NULL) 3609 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3610 return; 3611 } 3612 3613 /* What have we got? */ 3614 switch (offer) { 3615 case 0: 3616 /* 3617 * Offer == 0 means that there was no MSS on the SYN 3618 * segment, in this case we use tcp_mssdflt as 3619 * already assigned to t_maxseg above. 3620 */ 3621 offer = tp->t_maxseg; 3622 break; 3623 3624 case -1: 3625 /* 3626 * Offer == -1 means that we didn't receive SYN yet. 3627 */ 3628 /* FALLTHROUGH */ 3629 3630 default: 3631 /* 3632 * Prevent DoS attack with too small MSS. Round up 3633 * to at least minmss. 3634 */ 3635 offer = max(offer, V_tcp_minmss); 3636 } 3637 3638 /* 3639 * rmx information is now retrieved from tcp_hostcache. 3640 */ 3641 tcp_hc_get(&inp->inp_inc, &metrics); 3642 if (metricptr != NULL) 3643 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3644 3645 /* 3646 * If there's a discovered mtu in tcp hostcache, use it. 3647 * Else, use the link mtu. 3648 */ 3649 if (metrics.rmx_mtu) 3650 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3651 else { 3652 #ifdef INET6 3653 if (isipv6) { 3654 mss = maxmtu - min_protoh; 3655 if (!V_path_mtu_discovery && 3656 !in6_localaddr(&inp->in6p_faddr)) 3657 mss = min(mss, V_tcp_v6mssdflt); 3658 } 3659 #endif 3660 #if defined(INET) && defined(INET6) 3661 else 3662 #endif 3663 #ifdef INET 3664 { 3665 mss = maxmtu - min_protoh; 3666 if (!V_path_mtu_discovery && 3667 !in_localaddr(inp->inp_faddr)) 3668 mss = min(mss, V_tcp_mssdflt); 3669 } 3670 #endif 3671 /* 3672 * XXX - The above conditional (mss = maxmtu - min_protoh) 3673 * probably violates the TCP spec. 3674 * The problem is that, since we don't know the 3675 * other end's MSS, we are supposed to use a conservative 3676 * default. But, if we do that, then MTU discovery will 3677 * never actually take place, because the conservative 3678 * default is much less than the MTUs typically seen 3679 * on the Internet today. For the moment, we'll sweep 3680 * this under the carpet. 3681 * 3682 * The conservative default might not actually be a problem 3683 * if the only case this occurs is when sending an initial 3684 * SYN with options and data to a host we've never talked 3685 * to before. Then, they will reply with an MSS value which 3686 * will get recorded and the new parameters should get 3687 * recomputed. For Further Study. 3688 */ 3689 } 3690 mss = min(mss, offer); 3691 3692 /* 3693 * Sanity check: make sure that maxseg will be large 3694 * enough to allow some data on segments even if the 3695 * all the option space is used (40bytes). Otherwise 3696 * funny things may happen in tcp_output. 3697 * 3698 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3699 */ 3700 mss = max(mss, 64); 3701 3702 tp->t_maxseg = mss; 3703 } 3704 3705 void 3706 tcp_mss(struct tcpcb *tp, int offer) 3707 { 3708 int mss; 3709 u_long bufsize; 3710 struct inpcb *inp; 3711 struct socket *so; 3712 struct hc_metrics_lite metrics; 3713 struct tcp_ifcap cap; 3714 3715 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3716 3717 bzero(&cap, sizeof(cap)); 3718 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3719 3720 mss = tp->t_maxseg; 3721 inp = tp->t_inpcb; 3722 3723 /* 3724 * If there's a pipesize, change the socket buffer to that size, 3725 * don't change if sb_hiwat is different than default (then it 3726 * has been changed on purpose with setsockopt). 3727 * Make the socket buffers an integral number of mss units; 3728 * if the mss is larger than the socket buffer, decrease the mss. 3729 */ 3730 so = inp->inp_socket; 3731 SOCKBUF_LOCK(&so->so_snd); 3732 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3733 bufsize = metrics.rmx_sendpipe; 3734 else 3735 bufsize = so->so_snd.sb_hiwat; 3736 if (bufsize < mss) 3737 mss = bufsize; 3738 else { 3739 bufsize = roundup(bufsize, mss); 3740 if (bufsize > sb_max) 3741 bufsize = sb_max; 3742 if (bufsize > so->so_snd.sb_hiwat) 3743 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3744 } 3745 SOCKBUF_UNLOCK(&so->so_snd); 3746 tp->t_maxseg = mss; 3747 3748 SOCKBUF_LOCK(&so->so_rcv); 3749 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3750 bufsize = metrics.rmx_recvpipe; 3751 else 3752 bufsize = so->so_rcv.sb_hiwat; 3753 if (bufsize > mss) { 3754 bufsize = roundup(bufsize, mss); 3755 if (bufsize > sb_max) 3756 bufsize = sb_max; 3757 if (bufsize > so->so_rcv.sb_hiwat) 3758 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3759 } 3760 SOCKBUF_UNLOCK(&so->so_rcv); 3761 3762 /* Check the interface for TSO capabilities. */ 3763 if (cap.ifcap & CSUM_TSO) { 3764 tp->t_flags |= TF_TSO; 3765 tp->t_tsomax = cap.tsomax; 3766 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3767 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3768 } 3769 } 3770 3771 /* 3772 * Determine the MSS option to send on an outgoing SYN. 3773 */ 3774 int 3775 tcp_mssopt(struct in_conninfo *inc) 3776 { 3777 int mss = 0; 3778 u_long maxmtu = 0; 3779 u_long thcmtu = 0; 3780 size_t min_protoh; 3781 3782 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3783 3784 #ifdef INET6 3785 if (inc->inc_flags & INC_ISIPV6) { 3786 mss = V_tcp_v6mssdflt; 3787 maxmtu = tcp_maxmtu6(inc, NULL); 3788 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3789 } 3790 #endif 3791 #if defined(INET) && defined(INET6) 3792 else 3793 #endif 3794 #ifdef INET 3795 { 3796 mss = V_tcp_mssdflt; 3797 maxmtu = tcp_maxmtu(inc, NULL); 3798 min_protoh = sizeof(struct tcpiphdr); 3799 } 3800 #endif 3801 #if defined(INET6) || defined(INET) 3802 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3803 #endif 3804 3805 if (maxmtu && thcmtu) 3806 mss = min(maxmtu, thcmtu) - min_protoh; 3807 else if (maxmtu || thcmtu) 3808 mss = max(maxmtu, thcmtu) - min_protoh; 3809 3810 return (mss); 3811 } 3812 3813 3814 /* 3815 * On a partial ack arrives, force the retransmission of the 3816 * next unacknowledged segment. Do not clear tp->t_dupacks. 3817 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3818 * be started again. 3819 */ 3820 void 3821 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3822 { 3823 tcp_seq onxt = tp->snd_nxt; 3824 u_long ocwnd = tp->snd_cwnd; 3825 u_int maxseg = tcp_maxseg(tp); 3826 3827 INP_WLOCK_ASSERT(tp->t_inpcb); 3828 3829 tcp_timer_activate(tp, TT_REXMT, 0); 3830 tp->t_rtttime = 0; 3831 tp->snd_nxt = th->th_ack; 3832 /* 3833 * Set snd_cwnd to one segment beyond acknowledged offset. 3834 * (tp->snd_una has not yet been updated when this function is called.) 3835 */ 3836 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3837 tp->t_flags |= TF_ACKNOW; 3838 (void) tp->t_fb->tfb_tcp_output(tp); 3839 tp->snd_cwnd = ocwnd; 3840 if (SEQ_GT(onxt, tp->snd_nxt)) 3841 tp->snd_nxt = onxt; 3842 /* 3843 * Partial window deflation. Relies on fact that tp->snd_una 3844 * not updated yet. 3845 */ 3846 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3847 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3848 else 3849 tp->snd_cwnd = 0; 3850 tp->snd_cwnd += maxseg; 3851 } 3852 3853 int 3854 tcp_compute_pipe(struct tcpcb *tp) 3855 { 3856 return (tp->snd_max - tp->snd_una + 3857 tp->sackhint.sack_bytes_rexmit - 3858 tp->sackhint.sacked_bytes); 3859 } 3860