1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995 5 * The Regents of the University of California. All rights reserved. 6 * Copyright (c) 2007-2008,2010 7 * Swinburne University of Technology, Melbourne, Australia. 8 * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org> 9 * Copyright (c) 2010 The FreeBSD Foundation 10 * Copyright (c) 2010-2011 Juniper Networks, Inc. 11 * All rights reserved. 12 * 13 * Portions of this software were developed at the Centre for Advanced Internet 14 * Architectures, Swinburne University of Technology, by Lawrence Stewart, 15 * James Healy and David Hayes, made possible in part by a grant from the Cisco 16 * University Research Program Fund at Community Foundation Silicon Valley. 17 * 18 * Portions of this software were developed at the Centre for Advanced 19 * Internet Architectures, Swinburne University of Technology, Melbourne, 20 * Australia by David Hayes under sponsorship from the FreeBSD Foundation. 21 * 22 * Portions of this software were developed by Robert N. M. Watson under 23 * contract to Juniper Networks, Inc. 24 * 25 * Redistribution and use in source and binary forms, with or without 26 * modification, are permitted provided that the following conditions 27 * are met: 28 * 1. Redistributions of source code must retain the above copyright 29 * notice, this list of conditions and the following disclaimer. 30 * 2. Redistributions in binary form must reproduce the above copyright 31 * notice, this list of conditions and the following disclaimer in the 32 * documentation and/or other materials provided with the distribution. 33 * 3. Neither the name of the University nor the names of its contributors 34 * may be used to endorse or promote products derived from this software 35 * without specific prior written permission. 36 * 37 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 38 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 39 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 40 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 41 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 42 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 43 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 44 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 45 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 46 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 47 * SUCH DAMAGE. 48 * 49 * @(#)tcp_input.c 8.12 (Berkeley) 5/24/95 50 */ 51 52 #include <sys/cdefs.h> 53 __FBSDID("$FreeBSD$"); 54 55 #include "opt_inet.h" 56 #include "opt_inet6.h" 57 #include "opt_ipsec.h" 58 #include "opt_tcpdebug.h" 59 60 #include <sys/param.h> 61 #include <sys/arb.h> 62 #include <sys/kernel.h> 63 #ifdef TCP_HHOOK 64 #include <sys/hhook.h> 65 #endif 66 #include <sys/malloc.h> 67 #include <sys/mbuf.h> 68 #include <sys/proc.h> /* for proc0 declaration */ 69 #include <sys/protosw.h> 70 #include <sys/qmath.h> 71 #include <sys/sdt.h> 72 #include <sys/signalvar.h> 73 #include <sys/socket.h> 74 #include <sys/socketvar.h> 75 #include <sys/sysctl.h> 76 #include <sys/syslog.h> 77 #include <sys/systm.h> 78 #include <sys/stats.h> 79 80 #include <machine/cpu.h> /* before tcp_seq.h, for tcp_random18() */ 81 82 #include <vm/uma.h> 83 84 #include <net/if.h> 85 #include <net/if_var.h> 86 #include <net/route.h> 87 #include <net/vnet.h> 88 89 #define TCPSTATES /* for logging */ 90 91 #include <netinet/in.h> 92 #include <netinet/in_kdtrace.h> 93 #include <netinet/in_pcb.h> 94 #include <netinet/in_systm.h> 95 #include <netinet/ip.h> 96 #include <netinet/ip_icmp.h> /* required for icmp_var.h */ 97 #include <netinet/icmp_var.h> /* for ICMP_BANDLIM */ 98 #include <netinet/ip_var.h> 99 #include <netinet/ip_options.h> 100 #include <netinet/ip6.h> 101 #include <netinet/icmp6.h> 102 #include <netinet6/in6_pcb.h> 103 #include <netinet6/in6_var.h> 104 #include <netinet6/ip6_var.h> 105 #include <netinet6/nd6.h> 106 #include <netinet/tcp.h> 107 #include <netinet/tcp_fsm.h> 108 #include <netinet/tcp_log_buf.h> 109 #include <netinet/tcp_seq.h> 110 #include <netinet/tcp_timer.h> 111 #include <netinet/tcp_var.h> 112 #include <netinet6/tcp6_var.h> 113 #include <netinet/tcpip.h> 114 #include <netinet/cc/cc.h> 115 #include <netinet/tcp_fastopen.h> 116 #ifdef TCPPCAP 117 #include <netinet/tcp_pcap.h> 118 #endif 119 #include <netinet/tcp_syncache.h> 120 #ifdef TCPDEBUG 121 #include <netinet/tcp_debug.h> 122 #endif /* TCPDEBUG */ 123 #ifdef TCP_OFFLOAD 124 #include <netinet/tcp_offload.h> 125 #endif 126 127 #include <netipsec/ipsec_support.h> 128 129 #include <machine/in_cksum.h> 130 131 #include <security/mac/mac_framework.h> 132 133 const int tcprexmtthresh = 3; 134 135 VNET_DEFINE(int, tcp_log_in_vain) = 0; 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_VNET | CTLFLAG_RW, 137 &VNET_NAME(tcp_log_in_vain), 0, 138 "Log all incoming TCP segments to closed ports"); 139 140 VNET_DEFINE(int, blackhole) = 0; 141 #define V_blackhole VNET(blackhole) 142 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW, 143 &VNET_NAME(blackhole), 0, 144 "Do not send RST on segments to closed ports"); 145 146 VNET_DEFINE(int, tcp_delack_enabled) = 1; 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW, 148 &VNET_NAME(tcp_delack_enabled), 0, 149 "Delay ACK to try and piggyback it onto a data packet"); 150 151 VNET_DEFINE(int, drop_synfin) = 0; 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW, 153 &VNET_NAME(drop_synfin), 0, 154 "Drop TCP packets with SYN+FIN set"); 155 156 VNET_DEFINE(int, tcp_do_newcwv) = 0; 157 SYSCTL_INT(_net_inet_tcp, OID_AUTO, newcwv, CTLFLAG_VNET | CTLFLAG_RW, 158 &VNET_NAME(tcp_do_newcwv), 0, 159 "Enable New Congestion Window Validation per RFC7661"); 160 161 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0; 162 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW, 163 &VNET_NAME(tcp_do_rfc6675_pipe), 0, 164 "Use calculated pipe/in-flight bytes per RFC 6675"); 165 166 VNET_DEFINE(int, tcp_do_rfc3042) = 1; 167 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW, 168 &VNET_NAME(tcp_do_rfc3042), 0, 169 "Enable RFC 3042 (Limited Transmit)"); 170 171 VNET_DEFINE(int, tcp_do_rfc3390) = 1; 172 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW, 173 &VNET_NAME(tcp_do_rfc3390), 0, 174 "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)"); 175 176 VNET_DEFINE(int, tcp_initcwnd_segments) = 10; 177 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments, 178 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0, 179 "Slow-start flight size (initial congestion window) in number of segments"); 180 181 VNET_DEFINE(int, tcp_do_rfc3465) = 1; 182 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW, 183 &VNET_NAME(tcp_do_rfc3465), 0, 184 "Enable RFC 3465 (Appropriate Byte Counting)"); 185 186 VNET_DEFINE(int, tcp_abc_l_var) = 2; 187 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW, 188 &VNET_NAME(tcp_abc_l_var), 2, 189 "Cap the max cwnd increment during slow-start to this number of segments"); 190 191 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, 192 CTLFLAG_RW | CTLFLAG_MPSAFE, 0, 193 "TCP ECN"); 194 195 VNET_DEFINE(int, tcp_do_ecn) = 2; 196 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW, 197 &VNET_NAME(tcp_do_ecn), 0, 198 "TCP ECN support"); 199 200 VNET_DEFINE(int, tcp_ecn_maxretries) = 1; 201 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW, 202 &VNET_NAME(tcp_ecn_maxretries), 0, 203 "Max retries before giving up on ECN"); 204 205 VNET_DEFINE(int, tcp_insecure_syn) = 0; 206 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW, 207 &VNET_NAME(tcp_insecure_syn), 0, 208 "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets"); 209 210 VNET_DEFINE(int, tcp_insecure_rst) = 0; 211 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW, 212 &VNET_NAME(tcp_insecure_rst), 0, 213 "Follow RFC793 instead of RFC5961 criteria for accepting RST packets"); 214 215 VNET_DEFINE(int, tcp_recvspace) = 1024*64; 216 #define V_tcp_recvspace VNET(tcp_recvspace) 217 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW, 218 &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size"); 219 220 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1; 221 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW, 222 &VNET_NAME(tcp_do_autorcvbuf), 0, 223 "Enable automatic receive buffer sizing"); 224 225 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024; 226 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW, 227 &VNET_NAME(tcp_autorcvbuf_max), 0, 228 "Max size of automatic receive buffer"); 229 230 VNET_DEFINE(struct inpcbhead, tcb); 231 #define tcb6 tcb /* for KAME src sync over BSD*'s */ 232 VNET_DEFINE(struct inpcbinfo, tcbinfo); 233 234 /* 235 * TCP statistics are stored in an array of counter(9)s, which size matches 236 * size of struct tcpstat. TCP running connection count is a regular array. 237 */ 238 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat); 239 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat, 240 tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)"); 241 VNET_DEFINE(counter_u64_t, tcps_states[TCP_NSTATES]); 242 SYSCTL_COUNTER_U64_ARRAY(_net_inet_tcp, TCPCTL_STATES, states, CTLFLAG_RD | 243 CTLFLAG_VNET, &VNET_NAME(tcps_states)[0], TCP_NSTATES, 244 "TCP connection counts by TCP state"); 245 246 static void 247 tcp_vnet_init(const void *unused) 248 { 249 250 COUNTER_ARRAY_ALLOC(V_tcps_states, TCP_NSTATES, M_WAITOK); 251 VNET_PCPUSTAT_ALLOC(tcpstat, M_WAITOK); 252 } 253 VNET_SYSINIT(tcp_vnet_init, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 254 tcp_vnet_init, NULL); 255 256 #ifdef VIMAGE 257 static void 258 tcp_vnet_uninit(const void *unused) 259 { 260 261 COUNTER_ARRAY_FREE(V_tcps_states, TCP_NSTATES); 262 VNET_PCPUSTAT_FREE(tcpstat); 263 } 264 VNET_SYSUNINIT(tcp_vnet_uninit, SI_SUB_PROTO_IFATTACHDOMAIN, SI_ORDER_ANY, 265 tcp_vnet_uninit, NULL); 266 #endif /* VIMAGE */ 267 268 /* 269 * Kernel module interface for updating tcpstat. The first argument is an index 270 * into tcpstat treated as an array. 271 */ 272 void 273 kmod_tcpstat_add(int statnum, int val) 274 { 275 276 counter_u64_add(VNET(tcpstat)[statnum], val); 277 } 278 279 #ifdef TCP_HHOOK 280 /* 281 * Wrapper for the TCP established input helper hook. 282 */ 283 void 284 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to) 285 { 286 struct tcp_hhook_data hhook_data; 287 288 if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) { 289 hhook_data.tp = tp; 290 hhook_data.th = th; 291 hhook_data.to = to; 292 293 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data, 294 tp->osd); 295 } 296 } 297 #endif 298 299 /* 300 * CC wrapper hook functions 301 */ 302 void 303 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t nsegs, 304 uint16_t type) 305 { 306 #ifdef STATS 307 int32_t gput; 308 #endif 309 310 INP_WLOCK_ASSERT(tp->t_inpcb); 311 312 tp->ccv->nsegs = nsegs; 313 tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th); 314 if ((!V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd)) || 315 (V_tcp_do_newcwv && (tp->snd_cwnd <= tp->snd_wnd) && 316 (tp->snd_cwnd < (tcp_compute_pipe(tp) * 2)))) 317 tp->ccv->flags |= CCF_CWND_LIMITED; 318 else 319 tp->ccv->flags &= ~CCF_CWND_LIMITED; 320 321 if (type == CC_ACK) { 322 #ifdef STATS 323 stats_voi_update_abs_s32(tp->t_stats, VOI_TCP_CALCFRWINDIFF, 324 ((int32_t)tp->snd_cwnd) - tp->snd_wnd); 325 if (!IN_RECOVERY(tp->t_flags)) 326 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_ACKLEN, 327 tp->ccv->bytes_this_ack / (tcp_maxseg(tp) * nsegs)); 328 if ((tp->t_flags & TF_GPUTINPROG) && 329 SEQ_GEQ(th->th_ack, tp->gput_ack)) { 330 /* 331 * Compute goodput in bits per millisecond. 332 */ 333 gput = (((int64_t)(th->th_ack - tp->gput_seq)) << 3) / 334 max(1, tcp_ts_getticks() - tp->gput_ts); 335 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_GPUT, 336 gput); 337 /* 338 * XXXLAS: This is a temporary hack, and should be 339 * chained off VOI_TCP_GPUT when stats(9) grows an API 340 * to deal with chained VOIs. 341 */ 342 if (tp->t_stats_gput_prev > 0) 343 stats_voi_update_abs_s32(tp->t_stats, 344 VOI_TCP_GPUT_ND, 345 ((gput - tp->t_stats_gput_prev) * 100) / 346 tp->t_stats_gput_prev); 347 tp->t_flags &= ~TF_GPUTINPROG; 348 tp->t_stats_gput_prev = gput; 349 } 350 #endif /* STATS */ 351 if (tp->snd_cwnd > tp->snd_ssthresh) { 352 tp->t_bytes_acked += tp->ccv->bytes_this_ack; 353 if (tp->t_bytes_acked >= tp->snd_cwnd) { 354 tp->t_bytes_acked -= tp->snd_cwnd; 355 tp->ccv->flags |= CCF_ABC_SENTAWND; 356 } 357 } else { 358 tp->ccv->flags &= ~CCF_ABC_SENTAWND; 359 tp->t_bytes_acked = 0; 360 } 361 } 362 363 if (CC_ALGO(tp)->ack_received != NULL) { 364 /* XXXLAS: Find a way to live without this */ 365 tp->ccv->curack = th->th_ack; 366 CC_ALGO(tp)->ack_received(tp->ccv, type); 367 } 368 #ifdef STATS 369 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_LCWIN, tp->snd_cwnd); 370 #endif 371 } 372 373 void 374 cc_conn_init(struct tcpcb *tp) 375 { 376 struct hc_metrics_lite metrics; 377 struct inpcb *inp = tp->t_inpcb; 378 u_int maxseg; 379 int rtt; 380 381 INP_WLOCK_ASSERT(tp->t_inpcb); 382 383 tcp_hc_get(&inp->inp_inc, &metrics); 384 maxseg = tcp_maxseg(tp); 385 386 if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) { 387 tp->t_srtt = rtt; 388 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE; 389 TCPSTAT_INC(tcps_usedrtt); 390 if (metrics.rmx_rttvar) { 391 tp->t_rttvar = metrics.rmx_rttvar; 392 TCPSTAT_INC(tcps_usedrttvar); 393 } else { 394 /* default variation is +- 1 rtt */ 395 tp->t_rttvar = 396 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 397 } 398 TCPT_RANGESET(tp->t_rxtcur, 399 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 400 tp->t_rttmin, TCPTV_REXMTMAX); 401 } 402 if (metrics.rmx_ssthresh) { 403 /* 404 * There's some sort of gateway or interface 405 * buffer limit on the path. Use this to set 406 * the slow start threshold, but set the 407 * threshold to no less than 2*mss. 408 */ 409 tp->snd_ssthresh = max(2 * maxseg, metrics.rmx_ssthresh); 410 TCPSTAT_INC(tcps_usedssthresh); 411 } 412 413 /* 414 * Set the initial slow-start flight size. 415 * 416 * If a SYN or SYN/ACK was lost and retransmitted, we have to 417 * reduce the initial CWND to one segment as congestion is likely 418 * requiring us to be cautious. 419 */ 420 if (tp->snd_cwnd == 1) 421 tp->snd_cwnd = maxseg; /* SYN(-ACK) lost */ 422 else 423 tp->snd_cwnd = tcp_compute_initwnd(maxseg); 424 425 if (CC_ALGO(tp)->conn_init != NULL) 426 CC_ALGO(tp)->conn_init(tp->ccv); 427 } 428 429 void inline 430 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type) 431 { 432 u_int maxseg; 433 434 INP_WLOCK_ASSERT(tp->t_inpcb); 435 436 #ifdef STATS 437 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_CSIG, type); 438 #endif 439 440 switch(type) { 441 case CC_NDUPACK: 442 if (!IN_FASTRECOVERY(tp->t_flags)) { 443 tp->snd_recover = tp->snd_max; 444 if (tp->t_flags2 & TF2_ECN_PERMIT) 445 tp->t_flags2 |= TF2_ECN_SND_CWR; 446 } 447 break; 448 case CC_ECN: 449 if (!IN_CONGRECOVERY(tp->t_flags) || 450 /* 451 * Allow ECN reaction on ACK to CWR, if 452 * that data segment was also CE marked. 453 */ 454 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 455 EXIT_CONGRECOVERY(tp->t_flags); 456 TCPSTAT_INC(tcps_ecn_rcwnd); 457 tp->snd_recover = tp->snd_max + 1; 458 if (tp->t_flags2 & TF2_ECN_PERMIT) 459 tp->t_flags2 |= TF2_ECN_SND_CWR; 460 } 461 break; 462 case CC_RTO: 463 maxseg = tcp_maxseg(tp); 464 tp->t_dupacks = 0; 465 tp->t_bytes_acked = 0; 466 EXIT_RECOVERY(tp->t_flags); 467 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 / 468 maxseg) * maxseg; 469 tp->snd_cwnd = maxseg; 470 if (tp->t_flags2 & TF2_ECN_PERMIT) 471 tp->t_flags2 |= TF2_ECN_SND_CWR; 472 break; 473 case CC_RTO_ERR: 474 TCPSTAT_INC(tcps_sndrexmitbad); 475 /* RTO was unnecessary, so reset everything. */ 476 tp->snd_cwnd = tp->snd_cwnd_prev; 477 tp->snd_ssthresh = tp->snd_ssthresh_prev; 478 tp->snd_recover = tp->snd_recover_prev; 479 if (tp->t_flags & TF_WASFRECOVERY) 480 ENTER_FASTRECOVERY(tp->t_flags); 481 if (tp->t_flags & TF_WASCRECOVERY) 482 ENTER_CONGRECOVERY(tp->t_flags); 483 tp->snd_nxt = tp->snd_max; 484 tp->t_flags &= ~TF_PREVVALID; 485 tp->t_badrxtwin = 0; 486 break; 487 } 488 489 if (CC_ALGO(tp)->cong_signal != NULL) { 490 if (th != NULL) 491 tp->ccv->curack = th->th_ack; 492 CC_ALGO(tp)->cong_signal(tp->ccv, type); 493 } 494 } 495 496 void inline 497 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th) 498 { 499 INP_WLOCK_ASSERT(tp->t_inpcb); 500 501 /* XXXLAS: KASSERT that we're in recovery? */ 502 503 if (CC_ALGO(tp)->post_recovery != NULL) { 504 tp->ccv->curack = th->th_ack; 505 CC_ALGO(tp)->post_recovery(tp->ccv); 506 } 507 /* XXXLAS: EXIT_RECOVERY ? */ 508 tp->t_bytes_acked = 0; 509 } 510 511 /* 512 * Indicate whether this ack should be delayed. We can delay the ack if 513 * following conditions are met: 514 * - There is no delayed ack timer in progress. 515 * - Our last ack wasn't a 0-sized window. We never want to delay 516 * the ack that opens up a 0-sized window. 517 * - LRO wasn't used for this segment. We make sure by checking that the 518 * segment size is not larger than the MSS. 519 */ 520 #define DELAY_ACK(tp, tlen) \ 521 ((!tcp_timer_active(tp, TT_DELACK) && \ 522 (tp->t_flags & TF_RXWIN0SENT) == 0) && \ 523 (tlen <= tp->t_maxseg) && \ 524 (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN))) 525 526 void inline 527 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos) 528 { 529 INP_WLOCK_ASSERT(tp->t_inpcb); 530 531 if (CC_ALGO(tp)->ecnpkt_handler != NULL) { 532 switch (iptos & IPTOS_ECN_MASK) { 533 case IPTOS_ECN_CE: 534 tp->ccv->flags |= CCF_IPHDR_CE; 535 break; 536 case IPTOS_ECN_ECT0: 537 /* FALLTHROUGH */ 538 case IPTOS_ECN_ECT1: 539 /* FALLTHROUGH */ 540 case IPTOS_ECN_NOTECT: 541 tp->ccv->flags &= ~CCF_IPHDR_CE; 542 break; 543 } 544 545 if (th->th_flags & TH_CWR) 546 tp->ccv->flags |= CCF_TCPHDR_CWR; 547 else 548 tp->ccv->flags &= ~CCF_TCPHDR_CWR; 549 550 CC_ALGO(tp)->ecnpkt_handler(tp->ccv); 551 552 if (tp->ccv->flags & CCF_ACKNOW) { 553 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 554 tp->t_flags |= TF_ACKNOW; 555 } 556 } 557 } 558 559 /* 560 * TCP input handling is split into multiple parts: 561 * tcp6_input is a thin wrapper around tcp_input for the extended 562 * ip6_protox[] call format in ip6_input 563 * tcp_input handles primary segment validation, inpcb lookup and 564 * SYN processing on listen sockets 565 * tcp_do_segment processes the ACK and text of the segment for 566 * establishing, established and closing connections 567 */ 568 #ifdef INET6 569 int 570 tcp6_input(struct mbuf **mp, int *offp, int proto) 571 { 572 struct mbuf *m; 573 struct in6_ifaddr *ia6; 574 struct ip6_hdr *ip6; 575 576 m = *mp; 577 if (m->m_len < *offp + sizeof(struct tcphdr)) { 578 m = m_pullup(m, *offp + sizeof(struct tcphdr)); 579 if (m == NULL) { 580 *mp = m; 581 TCPSTAT_INC(tcps_rcvshort); 582 return (IPPROTO_DONE); 583 } 584 } 585 586 /* 587 * draft-itojun-ipv6-tcp-to-anycast 588 * better place to put this in? 589 */ 590 ip6 = mtod(m, struct ip6_hdr *); 591 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 592 if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) { 593 594 ifa_free(&ia6->ia_ifa); 595 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR, 596 (caddr_t)&ip6->ip6_dst - (caddr_t)ip6); 597 *mp = NULL; 598 return (IPPROTO_DONE); 599 } 600 if (ia6) 601 ifa_free(&ia6->ia_ifa); 602 603 *mp = m; 604 return (tcp_input(mp, offp, proto)); 605 } 606 #endif /* INET6 */ 607 608 int 609 tcp_input(struct mbuf **mp, int *offp, int proto) 610 { 611 struct mbuf *m = *mp; 612 struct tcphdr *th = NULL; 613 struct ip *ip = NULL; 614 struct inpcb *inp = NULL; 615 struct tcpcb *tp = NULL; 616 struct socket *so = NULL; 617 u_char *optp = NULL; 618 int off0; 619 int optlen = 0; 620 #ifdef INET 621 int len; 622 uint8_t ipttl; 623 #endif 624 int tlen = 0, off; 625 int drop_hdrlen; 626 int thflags; 627 int rstreason = 0; /* For badport_bandlim accounting purposes */ 628 uint8_t iptos; 629 struct m_tag *fwd_tag = NULL; 630 #ifdef INET6 631 struct ip6_hdr *ip6 = NULL; 632 int isipv6; 633 #else 634 const void *ip6 = NULL; 635 #endif /* INET6 */ 636 struct tcpopt to; /* options in this segment */ 637 char *s = NULL; /* address and port logging */ 638 #ifdef TCPDEBUG 639 /* 640 * The size of tcp_saveipgen must be the size of the max ip header, 641 * now IPv6. 642 */ 643 u_char tcp_saveipgen[IP6_HDR_LEN]; 644 struct tcphdr tcp_savetcp; 645 short ostate = 0; 646 #endif 647 648 NET_EPOCH_ASSERT(); 649 650 #ifdef INET6 651 isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0; 652 #endif 653 654 off0 = *offp; 655 m = *mp; 656 *mp = NULL; 657 to.to_flags = 0; 658 TCPSTAT_INC(tcps_rcvtotal); 659 660 #ifdef INET6 661 if (isipv6) { 662 663 ip6 = mtod(m, struct ip6_hdr *); 664 th = (struct tcphdr *)((caddr_t)ip6 + off0); 665 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0; 666 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) { 667 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 668 th->th_sum = m->m_pkthdr.csum_data; 669 else 670 th->th_sum = in6_cksum_pseudo(ip6, tlen, 671 IPPROTO_TCP, m->m_pkthdr.csum_data); 672 th->th_sum ^= 0xffff; 673 } else 674 th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen); 675 if (th->th_sum) { 676 TCPSTAT_INC(tcps_rcvbadsum); 677 goto drop; 678 } 679 680 /* 681 * Be proactive about unspecified IPv6 address in source. 682 * As we use all-zero to indicate unbounded/unconnected pcb, 683 * unspecified IPv6 address can be used to confuse us. 684 * 685 * Note that packets with unspecified IPv6 destination is 686 * already dropped in ip6_input. 687 */ 688 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) { 689 /* XXX stat */ 690 goto drop; 691 } 692 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff; 693 } 694 #endif 695 #if defined(INET) && defined(INET6) 696 else 697 #endif 698 #ifdef INET 699 { 700 /* 701 * Get IP and TCP header together in first mbuf. 702 * Note: IP leaves IP header in first mbuf. 703 */ 704 if (off0 > sizeof (struct ip)) { 705 ip_stripoptions(m); 706 off0 = sizeof(struct ip); 707 } 708 if (m->m_len < sizeof (struct tcpiphdr)) { 709 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) 710 == NULL) { 711 TCPSTAT_INC(tcps_rcvshort); 712 return (IPPROTO_DONE); 713 } 714 } 715 ip = mtod(m, struct ip *); 716 th = (struct tcphdr *)((caddr_t)ip + off0); 717 tlen = ntohs(ip->ip_len) - off0; 718 719 iptos = ip->ip_tos; 720 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) { 721 if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR) 722 th->th_sum = m->m_pkthdr.csum_data; 723 else 724 th->th_sum = in_pseudo(ip->ip_src.s_addr, 725 ip->ip_dst.s_addr, 726 htonl(m->m_pkthdr.csum_data + tlen + 727 IPPROTO_TCP)); 728 th->th_sum ^= 0xffff; 729 } else { 730 struct ipovly *ipov = (struct ipovly *)ip; 731 732 /* 733 * Checksum extended TCP header and data. 734 */ 735 len = off0 + tlen; 736 ipttl = ip->ip_ttl; 737 bzero(ipov->ih_x1, sizeof(ipov->ih_x1)); 738 ipov->ih_len = htons(tlen); 739 th->th_sum = in_cksum(m, len); 740 /* Reset length for SDT probes. */ 741 ip->ip_len = htons(len); 742 /* Reset TOS bits */ 743 ip->ip_tos = iptos; 744 /* Re-initialization for later version check */ 745 ip->ip_ttl = ipttl; 746 ip->ip_v = IPVERSION; 747 ip->ip_hl = off0 >> 2; 748 } 749 750 if (th->th_sum) { 751 TCPSTAT_INC(tcps_rcvbadsum); 752 goto drop; 753 } 754 } 755 #endif /* INET */ 756 757 /* 758 * Check that TCP offset makes sense, 759 * pull out TCP options and adjust length. XXX 760 */ 761 off = th->th_off << 2; 762 if (off < sizeof (struct tcphdr) || off > tlen) { 763 TCPSTAT_INC(tcps_rcvbadoff); 764 goto drop; 765 } 766 tlen -= off; /* tlen is used instead of ti->ti_len */ 767 if (off > sizeof (struct tcphdr)) { 768 #ifdef INET6 769 if (isipv6) { 770 if (m->m_len < off0 + off) { 771 m = m_pullup(m, off0 + off); 772 if (m == NULL) { 773 TCPSTAT_INC(tcps_rcvshort); 774 return (IPPROTO_DONE); 775 } 776 } 777 ip6 = mtod(m, struct ip6_hdr *); 778 th = (struct tcphdr *)((caddr_t)ip6 + off0); 779 } 780 #endif 781 #if defined(INET) && defined(INET6) 782 else 783 #endif 784 #ifdef INET 785 { 786 if (m->m_len < sizeof(struct ip) + off) { 787 if ((m = m_pullup(m, sizeof (struct ip) + off)) 788 == NULL) { 789 TCPSTAT_INC(tcps_rcvshort); 790 return (IPPROTO_DONE); 791 } 792 ip = mtod(m, struct ip *); 793 th = (struct tcphdr *)((caddr_t)ip + off0); 794 } 795 } 796 #endif 797 optlen = off - sizeof (struct tcphdr); 798 optp = (u_char *)(th + 1); 799 } 800 thflags = th->th_flags; 801 802 /* 803 * Convert TCP protocol specific fields to host format. 804 */ 805 tcp_fields_to_host(th); 806 807 /* 808 * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options. 809 */ 810 drop_hdrlen = off0 + off; 811 812 /* 813 * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain. 814 */ 815 if ( 816 #ifdef INET6 817 (isipv6 && (m->m_flags & M_IP6_NEXTHOP)) 818 #ifdef INET 819 || (!isipv6 && (m->m_flags & M_IP_NEXTHOP)) 820 #endif 821 #endif 822 #if defined(INET) && !defined(INET6) 823 (m->m_flags & M_IP_NEXTHOP) 824 #endif 825 ) 826 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL); 827 828 findpcb: 829 #ifdef INET6 830 if (isipv6 && fwd_tag != NULL) { 831 struct sockaddr_in6 *next_hop6; 832 833 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1); 834 /* 835 * Transparently forwarded. Pretend to be the destination. 836 * Already got one like this? 837 */ 838 inp = in6_pcblookup_mbuf(&V_tcbinfo, 839 &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport, 840 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m); 841 if (!inp) { 842 /* 843 * It's new. Try to find the ambushing socket. 844 * Because we've rewritten the destination address, 845 * any hardware-generated hash is ignored. 846 */ 847 inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src, 848 th->th_sport, &next_hop6->sin6_addr, 849 next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) : 850 th->th_dport, INPLOOKUP_WILDCARD | 851 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 852 } 853 } else if (isipv6) { 854 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src, 855 th->th_sport, &ip6->ip6_dst, th->th_dport, 856 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 857 m->m_pkthdr.rcvif, m); 858 } 859 #endif /* INET6 */ 860 #if defined(INET6) && defined(INET) 861 else 862 #endif 863 #ifdef INET 864 if (fwd_tag != NULL) { 865 struct sockaddr_in *next_hop; 866 867 next_hop = (struct sockaddr_in *)(fwd_tag+1); 868 /* 869 * Transparently forwarded. Pretend to be the destination. 870 * already got one like this? 871 */ 872 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport, 873 ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB, 874 m->m_pkthdr.rcvif, m); 875 if (!inp) { 876 /* 877 * It's new. Try to find the ambushing socket. 878 * Because we've rewritten the destination address, 879 * any hardware-generated hash is ignored. 880 */ 881 inp = in_pcblookup(&V_tcbinfo, ip->ip_src, 882 th->th_sport, next_hop->sin_addr, 883 next_hop->sin_port ? ntohs(next_hop->sin_port) : 884 th->th_dport, INPLOOKUP_WILDCARD | 885 INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif); 886 } 887 } else 888 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, 889 th->th_sport, ip->ip_dst, th->th_dport, 890 INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB, 891 m->m_pkthdr.rcvif, m); 892 #endif /* INET */ 893 894 /* 895 * If the INPCB does not exist then all data in the incoming 896 * segment is discarded and an appropriate RST is sent back. 897 * XXX MRT Send RST using which routing table? 898 */ 899 if (inp == NULL) { 900 /* 901 * Log communication attempts to ports that are not 902 * in use. 903 */ 904 if ((V_tcp_log_in_vain == 1 && (thflags & TH_SYN)) || 905 V_tcp_log_in_vain == 2) { 906 if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6))) 907 log(LOG_INFO, "%s; %s: Connection attempt " 908 "to closed port\n", s, __func__); 909 } 910 /* 911 * When blackholing do not respond with a RST but 912 * completely ignore the segment and drop it. 913 */ 914 if ((V_blackhole == 1 && (thflags & TH_SYN)) || 915 V_blackhole == 2) 916 goto dropunlock; 917 918 rstreason = BANDLIM_RST_CLOSEDPORT; 919 goto dropwithreset; 920 } 921 INP_WLOCK_ASSERT(inp); 922 /* 923 * While waiting for inp lock during the lookup, another thread 924 * can have dropped the inpcb, in which case we need to loop back 925 * and try to find a new inpcb to deliver to. 926 */ 927 if (inp->inp_flags & INP_DROPPED) { 928 INP_WUNLOCK(inp); 929 inp = NULL; 930 goto findpcb; 931 } 932 if ((inp->inp_flowtype == M_HASHTYPE_NONE) && 933 (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) && 934 ((inp->inp_socket == NULL) || 935 (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) { 936 inp->inp_flowid = m->m_pkthdr.flowid; 937 inp->inp_flowtype = M_HASHTYPE_GET(m); 938 } 939 #if defined(IPSEC) || defined(IPSEC_SUPPORT) 940 #ifdef INET6 941 if (isipv6 && IPSEC_ENABLED(ipv6) && 942 IPSEC_CHECK_POLICY(ipv6, m, inp) != 0) { 943 goto dropunlock; 944 } 945 #ifdef INET 946 else 947 #endif 948 #endif /* INET6 */ 949 #ifdef INET 950 if (IPSEC_ENABLED(ipv4) && 951 IPSEC_CHECK_POLICY(ipv4, m, inp) != 0) { 952 goto dropunlock; 953 } 954 #endif /* INET */ 955 #endif /* IPSEC */ 956 957 /* 958 * Check the minimum TTL for socket. 959 */ 960 if (inp->inp_ip_minttl != 0) { 961 #ifdef INET6 962 if (isipv6) { 963 if (inp->inp_ip_minttl > ip6->ip6_hlim) 964 goto dropunlock; 965 } else 966 #endif 967 if (inp->inp_ip_minttl > ip->ip_ttl) 968 goto dropunlock; 969 } 970 971 /* 972 * A previous connection in TIMEWAIT state is supposed to catch stray 973 * or duplicate segments arriving late. If this segment was a 974 * legitimate new connection attempt, the old INPCB gets removed and 975 * we can try again to find a listening socket. 976 * 977 * At this point, due to earlier optimism, we may hold only an inpcb 978 * lock, and not the inpcbinfo write lock. If so, we need to try to 979 * acquire it, or if that fails, acquire a reference on the inpcb, 980 * drop all locks, acquire a global write lock, and then re-acquire 981 * the inpcb lock. We may at that point discover that another thread 982 * has tried to free the inpcb, in which case we need to loop back 983 * and try to find a new inpcb to deliver to. 984 * 985 * XXXRW: It may be time to rethink timewait locking. 986 */ 987 if (inp->inp_flags & INP_TIMEWAIT) { 988 if (thflags & TH_SYN) 989 tcp_dooptions(&to, optp, optlen, TO_SYN); 990 /* 991 * NB: tcp_twcheck unlocks the INP and frees the mbuf. 992 */ 993 if (tcp_twcheck(inp, &to, th, m, tlen)) 994 goto findpcb; 995 return (IPPROTO_DONE); 996 } 997 /* 998 * The TCPCB may no longer exist if the connection is winding 999 * down or it is in the CLOSED state. Either way we drop the 1000 * segment and send an appropriate response. 1001 */ 1002 tp = intotcpcb(inp); 1003 if (tp == NULL || tp->t_state == TCPS_CLOSED) { 1004 rstreason = BANDLIM_RST_CLOSEDPORT; 1005 goto dropwithreset; 1006 } 1007 1008 #ifdef TCP_OFFLOAD 1009 if (tp->t_flags & TF_TOE) { 1010 tcp_offload_input(tp, m); 1011 m = NULL; /* consumed by the TOE driver */ 1012 goto dropunlock; 1013 } 1014 #endif 1015 1016 #ifdef MAC 1017 INP_WLOCK_ASSERT(inp); 1018 if (mac_inpcb_check_deliver(inp, m)) 1019 goto dropunlock; 1020 #endif 1021 so = inp->inp_socket; 1022 KASSERT(so != NULL, ("%s: so == NULL", __func__)); 1023 #ifdef TCPDEBUG 1024 if (so->so_options & SO_DEBUG) { 1025 ostate = tp->t_state; 1026 #ifdef INET6 1027 if (isipv6) { 1028 bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6)); 1029 } else 1030 #endif 1031 bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip)); 1032 tcp_savetcp = *th; 1033 } 1034 #endif /* TCPDEBUG */ 1035 /* 1036 * When the socket is accepting connections (the INPCB is in LISTEN 1037 * state) we look into the SYN cache if this is a new connection 1038 * attempt or the completion of a previous one. 1039 */ 1040 KASSERT(tp->t_state == TCPS_LISTEN || !(so->so_options & SO_ACCEPTCONN), 1041 ("%s: so accepting but tp %p not listening", __func__, tp)); 1042 if (tp->t_state == TCPS_LISTEN && (so->so_options & SO_ACCEPTCONN)) { 1043 struct in_conninfo inc; 1044 1045 bzero(&inc, sizeof(inc)); 1046 #ifdef INET6 1047 if (isipv6) { 1048 inc.inc_flags |= INC_ISIPV6; 1049 if (inp->inp_inc.inc_flags & INC_IPV6MINMTU) 1050 inc.inc_flags |= INC_IPV6MINMTU; 1051 inc.inc6_faddr = ip6->ip6_src; 1052 inc.inc6_laddr = ip6->ip6_dst; 1053 } else 1054 #endif 1055 { 1056 inc.inc_faddr = ip->ip_src; 1057 inc.inc_laddr = ip->ip_dst; 1058 } 1059 inc.inc_fport = th->th_sport; 1060 inc.inc_lport = th->th_dport; 1061 inc.inc_fibnum = so->so_fibnum; 1062 1063 /* 1064 * Check for an existing connection attempt in syncache if 1065 * the flag is only ACK. A successful lookup creates a new 1066 * socket appended to the listen queue in SYN_RECEIVED state. 1067 */ 1068 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) { 1069 1070 /* 1071 * Parse the TCP options here because 1072 * syncookies need access to the reflected 1073 * timestamp. 1074 */ 1075 tcp_dooptions(&to, optp, optlen, 0); 1076 /* 1077 * NB: syncache_expand() doesn't unlock 1078 * inp and tcpinfo locks. 1079 */ 1080 rstreason = syncache_expand(&inc, &to, th, &so, m); 1081 if (rstreason < 0) { 1082 /* 1083 * A failing TCP MD5 signature comparison 1084 * must result in the segment being dropped 1085 * and must not produce any response back 1086 * to the sender. 1087 */ 1088 goto dropunlock; 1089 } else if (rstreason == 0) { 1090 /* 1091 * No syncache entry or ACK was not 1092 * for our SYN/ACK. Send a RST. 1093 * NB: syncache did its own logging 1094 * of the failure cause. 1095 */ 1096 rstreason = BANDLIM_RST_OPENPORT; 1097 goto dropwithreset; 1098 } 1099 tfo_socket_result: 1100 if (so == NULL) { 1101 /* 1102 * We completed the 3-way handshake 1103 * but could not allocate a socket 1104 * either due to memory shortage, 1105 * listen queue length limits or 1106 * global socket limits. Send RST 1107 * or wait and have the remote end 1108 * retransmit the ACK for another 1109 * try. 1110 */ 1111 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1112 log(LOG_DEBUG, "%s; %s: Listen socket: " 1113 "Socket allocation failed due to " 1114 "limits or memory shortage, %s\n", 1115 s, __func__, 1116 V_tcp_sc_rst_sock_fail ? 1117 "sending RST" : "try again"); 1118 if (V_tcp_sc_rst_sock_fail) { 1119 rstreason = BANDLIM_UNLIMITED; 1120 goto dropwithreset; 1121 } else 1122 goto dropunlock; 1123 } 1124 /* 1125 * Socket is created in state SYN_RECEIVED. 1126 * Unlock the listen socket, lock the newly 1127 * created socket and update the tp variable. 1128 */ 1129 INP_WUNLOCK(inp); /* listen socket */ 1130 inp = sotoinpcb(so); 1131 /* 1132 * New connection inpcb is already locked by 1133 * syncache_expand(). 1134 */ 1135 INP_WLOCK_ASSERT(inp); 1136 tp = intotcpcb(inp); 1137 KASSERT(tp->t_state == TCPS_SYN_RECEIVED, 1138 ("%s: ", __func__)); 1139 /* 1140 * Process the segment and the data it 1141 * contains. tcp_do_segment() consumes 1142 * the mbuf chain and unlocks the inpcb. 1143 */ 1144 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1145 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, 1146 iptos); 1147 return (IPPROTO_DONE); 1148 } 1149 /* 1150 * Segment flag validation for new connection attempts: 1151 * 1152 * Our (SYN|ACK) response was rejected. 1153 * Check with syncache and remove entry to prevent 1154 * retransmits. 1155 * 1156 * NB: syncache_chkrst does its own logging of failure 1157 * causes. 1158 */ 1159 if (thflags & TH_RST) { 1160 syncache_chkrst(&inc, th, m); 1161 goto dropunlock; 1162 } 1163 /* 1164 * We can't do anything without SYN. 1165 */ 1166 if ((thflags & TH_SYN) == 0) { 1167 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1168 log(LOG_DEBUG, "%s; %s: Listen socket: " 1169 "SYN is missing, segment ignored\n", 1170 s, __func__); 1171 TCPSTAT_INC(tcps_badsyn); 1172 goto dropunlock; 1173 } 1174 /* 1175 * (SYN|ACK) is bogus on a listen socket. 1176 */ 1177 if (thflags & TH_ACK) { 1178 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1179 log(LOG_DEBUG, "%s; %s: Listen socket: " 1180 "SYN|ACK invalid, segment rejected\n", 1181 s, __func__); 1182 syncache_badack(&inc); /* XXX: Not needed! */ 1183 TCPSTAT_INC(tcps_badsyn); 1184 rstreason = BANDLIM_RST_OPENPORT; 1185 goto dropwithreset; 1186 } 1187 /* 1188 * If the drop_synfin option is enabled, drop all 1189 * segments with both the SYN and FIN bits set. 1190 * This prevents e.g. nmap from identifying the 1191 * TCP/IP stack. 1192 * XXX: Poor reasoning. nmap has other methods 1193 * and is constantly refining its stack detection 1194 * strategies. 1195 * XXX: This is a violation of the TCP specification 1196 * and was used by RFC1644. 1197 */ 1198 if ((thflags & TH_FIN) && V_drop_synfin) { 1199 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1200 log(LOG_DEBUG, "%s; %s: Listen socket: " 1201 "SYN|FIN segment ignored (based on " 1202 "sysctl setting)\n", s, __func__); 1203 TCPSTAT_INC(tcps_badsyn); 1204 goto dropunlock; 1205 } 1206 /* 1207 * Segment's flags are (SYN) or (SYN|FIN). 1208 * 1209 * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored 1210 * as they do not affect the state of the TCP FSM. 1211 * The data pointed to by TH_URG and th_urp is ignored. 1212 */ 1213 KASSERT((thflags & (TH_RST|TH_ACK)) == 0, 1214 ("%s: Listen socket: TH_RST or TH_ACK set", __func__)); 1215 KASSERT(thflags & (TH_SYN), 1216 ("%s: Listen socket: TH_SYN not set", __func__)); 1217 #ifdef INET6 1218 /* 1219 * If deprecated address is forbidden, 1220 * we do not accept SYN to deprecated interface 1221 * address to prevent any new inbound connection from 1222 * getting established. 1223 * When we do not accept SYN, we send a TCP RST, 1224 * with deprecated source address (instead of dropping 1225 * it). We compromise it as it is much better for peer 1226 * to send a RST, and RST will be the final packet 1227 * for the exchange. 1228 * 1229 * If we do not forbid deprecated addresses, we accept 1230 * the SYN packet. RFC2462 does not suggest dropping 1231 * SYN in this case. 1232 * If we decipher RFC2462 5.5.4, it says like this: 1233 * 1. use of deprecated addr with existing 1234 * communication is okay - "SHOULD continue to be 1235 * used" 1236 * 2. use of it with new communication: 1237 * (2a) "SHOULD NOT be used if alternate address 1238 * with sufficient scope is available" 1239 * (2b) nothing mentioned otherwise. 1240 * Here we fall into (2b) case as we have no choice in 1241 * our source address selection - we must obey the peer. 1242 * 1243 * The wording in RFC2462 is confusing, and there are 1244 * multiple description text for deprecated address 1245 * handling - worse, they are not exactly the same. 1246 * I believe 5.5.4 is the best one, so we follow 5.5.4. 1247 */ 1248 if (isipv6 && !V_ip6_use_deprecated) { 1249 struct in6_ifaddr *ia6; 1250 1251 ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */); 1252 if (ia6 != NULL && 1253 (ia6->ia6_flags & IN6_IFF_DEPRECATED)) { 1254 ifa_free(&ia6->ia_ifa); 1255 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1256 log(LOG_DEBUG, "%s; %s: Listen socket: " 1257 "Connection attempt to deprecated " 1258 "IPv6 address rejected\n", 1259 s, __func__); 1260 rstreason = BANDLIM_RST_OPENPORT; 1261 goto dropwithreset; 1262 } 1263 if (ia6) 1264 ifa_free(&ia6->ia_ifa); 1265 } 1266 #endif /* INET6 */ 1267 /* 1268 * Basic sanity checks on incoming SYN requests: 1269 * Don't respond if the destination is a link layer 1270 * broadcast according to RFC1122 4.2.3.10, p. 104. 1271 * If it is from this socket it must be forged. 1272 * Don't respond if the source or destination is a 1273 * global or subnet broad- or multicast address. 1274 * Note that it is quite possible to receive unicast 1275 * link-layer packets with a broadcast IP address. Use 1276 * in_broadcast() to find them. 1277 */ 1278 if (m->m_flags & (M_BCAST|M_MCAST)) { 1279 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1280 log(LOG_DEBUG, "%s; %s: Listen socket: " 1281 "Connection attempt from broad- or multicast " 1282 "link layer address ignored\n", s, __func__); 1283 goto dropunlock; 1284 } 1285 #ifdef INET6 1286 if (isipv6) { 1287 if (th->th_dport == th->th_sport && 1288 IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) { 1289 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1290 log(LOG_DEBUG, "%s; %s: Listen socket: " 1291 "Connection attempt to/from self " 1292 "ignored\n", s, __func__); 1293 goto dropunlock; 1294 } 1295 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 1296 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) { 1297 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1298 log(LOG_DEBUG, "%s; %s: Listen socket: " 1299 "Connection attempt from/to multicast " 1300 "address ignored\n", s, __func__); 1301 goto dropunlock; 1302 } 1303 } 1304 #endif 1305 #if defined(INET) && defined(INET6) 1306 else 1307 #endif 1308 #ifdef INET 1309 { 1310 if (th->th_dport == th->th_sport && 1311 ip->ip_dst.s_addr == ip->ip_src.s_addr) { 1312 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1313 log(LOG_DEBUG, "%s; %s: Listen socket: " 1314 "Connection attempt from/to self " 1315 "ignored\n", s, __func__); 1316 goto dropunlock; 1317 } 1318 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 1319 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 1320 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 1321 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) { 1322 if ((s = tcp_log_addrs(&inc, th, NULL, NULL))) 1323 log(LOG_DEBUG, "%s; %s: Listen socket: " 1324 "Connection attempt from/to broad- " 1325 "or multicast address ignored\n", 1326 s, __func__); 1327 goto dropunlock; 1328 } 1329 } 1330 #endif 1331 /* 1332 * SYN appears to be valid. Create compressed TCP state 1333 * for syncache. 1334 */ 1335 #ifdef TCPDEBUG 1336 if (so->so_options & SO_DEBUG) 1337 tcp_trace(TA_INPUT, ostate, tp, 1338 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1339 #endif 1340 TCP_PROBE3(debug__input, tp, th, m); 1341 tcp_dooptions(&to, optp, optlen, TO_SYN); 1342 if (syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL, iptos)) 1343 goto tfo_socket_result; 1344 1345 /* 1346 * Entry added to syncache and mbuf consumed. 1347 * Only the listen socket is unlocked by syncache_add(). 1348 */ 1349 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1350 return (IPPROTO_DONE); 1351 } else if (tp->t_state == TCPS_LISTEN) { 1352 /* 1353 * When a listen socket is torn down the SO_ACCEPTCONN 1354 * flag is removed first while connections are drained 1355 * from the accept queue in a unlock/lock cycle of the 1356 * ACCEPT_LOCK, opening a race condition allowing a SYN 1357 * attempt go through unhandled. 1358 */ 1359 goto dropunlock; 1360 } 1361 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1362 if (tp->t_flags & TF_SIGNATURE) { 1363 tcp_dooptions(&to, optp, optlen, thflags); 1364 if ((to.to_flags & TOF_SIGNATURE) == 0) { 1365 TCPSTAT_INC(tcps_sig_err_nosigopt); 1366 goto dropunlock; 1367 } 1368 if (!TCPMD5_ENABLED() || 1369 TCPMD5_INPUT(m, th, to.to_signature) != 0) 1370 goto dropunlock; 1371 } 1372 #endif 1373 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1374 1375 /* 1376 * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later 1377 * state. tcp_do_segment() always consumes the mbuf chain, unlocks 1378 * the inpcb, and unlocks pcbinfo. 1379 */ 1380 tp->t_fb->tfb_tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos); 1381 return (IPPROTO_DONE); 1382 1383 dropwithreset: 1384 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1385 1386 if (inp != NULL) { 1387 tcp_dropwithreset(m, th, tp, tlen, rstreason); 1388 INP_WUNLOCK(inp); 1389 } else 1390 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 1391 m = NULL; /* mbuf chain got consumed. */ 1392 goto drop; 1393 1394 dropunlock: 1395 if (m != NULL) 1396 TCP_PROBE5(receive, NULL, tp, m, tp, th); 1397 1398 if (inp != NULL) 1399 INP_WUNLOCK(inp); 1400 1401 drop: 1402 INP_INFO_WUNLOCK_ASSERT(&V_tcbinfo); 1403 if (s != NULL) 1404 free(s, M_TCPLOG); 1405 if (m != NULL) 1406 m_freem(m); 1407 return (IPPROTO_DONE); 1408 } 1409 1410 /* 1411 * Automatic sizing of receive socket buffer. Often the send 1412 * buffer size is not optimally adjusted to the actual network 1413 * conditions at hand (delay bandwidth product). Setting the 1414 * buffer size too small limits throughput on links with high 1415 * bandwidth and high delay (eg. trans-continental/oceanic links). 1416 * 1417 * On the receive side the socket buffer memory is only rarely 1418 * used to any significant extent. This allows us to be much 1419 * more aggressive in scaling the receive socket buffer. For 1420 * the case that the buffer space is actually used to a large 1421 * extent and we run out of kernel memory we can simply drop 1422 * the new segments; TCP on the sender will just retransmit it 1423 * later. Setting the buffer size too big may only consume too 1424 * much kernel memory if the application doesn't read() from 1425 * the socket or packet loss or reordering makes use of the 1426 * reassembly queue. 1427 * 1428 * The criteria to step up the receive buffer one notch are: 1429 * 1. Application has not set receive buffer size with 1430 * SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE. 1431 * 2. the number of bytes received during 1/2 of an sRTT 1432 * is at least 3/8 of the current socket buffer size. 1433 * 3. receive buffer size has not hit maximal automatic size; 1434 * 1435 * If all of the criteria are met we increaset the socket buffer 1436 * by a 1/2 (bounded by the max). This allows us to keep ahead 1437 * of slow-start but also makes it so our peer never gets limited 1438 * by our rwnd which we then open up causing a burst. 1439 * 1440 * This algorithm does two steps per RTT at most and only if 1441 * we receive a bulk stream w/o packet losses or reorderings. 1442 * Shrinking the buffer during idle times is not necessary as 1443 * it doesn't consume any memory when idle. 1444 * 1445 * TODO: Only step up if the application is actually serving 1446 * the buffer to better manage the socket buffer resources. 1447 */ 1448 int 1449 tcp_autorcvbuf(struct mbuf *m, struct tcphdr *th, struct socket *so, 1450 struct tcpcb *tp, int tlen) 1451 { 1452 int newsize = 0; 1453 1454 if (V_tcp_do_autorcvbuf && (so->so_rcv.sb_flags & SB_AUTOSIZE) && 1455 tp->t_srtt != 0 && tp->rfbuf_ts != 0 && 1456 TCP_TS_TO_TICKS(tcp_ts_getticks() - tp->rfbuf_ts) > 1457 ((tp->t_srtt >> TCP_RTT_SHIFT)/2)) { 1458 if (tp->rfbuf_cnt > ((so->so_rcv.sb_hiwat / 2)/ 4 * 3) && 1459 so->so_rcv.sb_hiwat < V_tcp_autorcvbuf_max) { 1460 newsize = min((so->so_rcv.sb_hiwat + (so->so_rcv.sb_hiwat/2)), V_tcp_autorcvbuf_max); 1461 } 1462 TCP_PROBE6(receive__autoresize, NULL, tp, m, tp, th, newsize); 1463 1464 /* Start over with next RTT. */ 1465 tp->rfbuf_ts = 0; 1466 tp->rfbuf_cnt = 0; 1467 } else { 1468 tp->rfbuf_cnt += tlen; /* add up */ 1469 } 1470 return (newsize); 1471 } 1472 1473 void 1474 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so, 1475 struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos) 1476 { 1477 int thflags, acked, ourfinisacked, needoutput = 0, sack_changed; 1478 int rstreason, todrop, win, incforsyn = 0; 1479 uint32_t tiwin; 1480 uint16_t nsegs; 1481 char *s; 1482 struct in_conninfo *inc; 1483 struct mbuf *mfree; 1484 struct tcpopt to; 1485 int tfo_syn; 1486 1487 #ifdef TCPDEBUG 1488 /* 1489 * The size of tcp_saveipgen must be the size of the max ip header, 1490 * now IPv6. 1491 */ 1492 u_char tcp_saveipgen[IP6_HDR_LEN]; 1493 struct tcphdr tcp_savetcp; 1494 short ostate = 0; 1495 #endif 1496 thflags = th->th_flags; 1497 inc = &tp->t_inpcb->inp_inc; 1498 tp->sackhint.last_sack_ack = 0; 1499 sack_changed = 0; 1500 nsegs = max(1, m->m_pkthdr.lro_nsegs); 1501 1502 NET_EPOCH_ASSERT(); 1503 INP_WLOCK_ASSERT(tp->t_inpcb); 1504 KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN", 1505 __func__)); 1506 KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT", 1507 __func__)); 1508 1509 #ifdef TCPPCAP 1510 /* Save segment, if requested. */ 1511 tcp_pcap_add(th, m, &(tp->t_inpkts)); 1512 #endif 1513 TCP_LOG_EVENT(tp, th, &so->so_rcv, &so->so_snd, TCP_LOG_IN, 0, 1514 tlen, NULL, true); 1515 1516 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 1517 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1518 log(LOG_DEBUG, "%s; %s: " 1519 "SYN|FIN segment ignored (based on " 1520 "sysctl setting)\n", s, __func__); 1521 free(s, M_TCPLOG); 1522 } 1523 goto drop; 1524 } 1525 1526 /* 1527 * If a segment with the ACK-bit set arrives in the SYN-SENT state 1528 * check SEQ.ACK first. 1529 */ 1530 if ((tp->t_state == TCPS_SYN_SENT) && (thflags & TH_ACK) && 1531 (SEQ_LEQ(th->th_ack, tp->iss) || SEQ_GT(th->th_ack, tp->snd_max))) { 1532 rstreason = BANDLIM_UNLIMITED; 1533 goto dropwithreset; 1534 } 1535 1536 /* 1537 * Segment received on connection. 1538 * Reset idle time and keep-alive timer. 1539 * XXX: This should be done after segment 1540 * validation to ignore broken/spoofed segs. 1541 */ 1542 tp->t_rcvtime = ticks; 1543 1544 /* 1545 * Scale up the window into a 32-bit value. 1546 * For the SYN_SENT state the scale is zero. 1547 */ 1548 tiwin = th->th_win << tp->snd_scale; 1549 #ifdef STATS 1550 stats_voi_update_abs_ulong(tp->t_stats, VOI_TCP_FRWIN, tiwin); 1551 #endif 1552 1553 /* 1554 * TCP ECN processing. 1555 */ 1556 if (tp->t_flags2 & TF2_ECN_PERMIT) { 1557 if (thflags & TH_CWR) { 1558 tp->t_flags2 &= ~TF2_ECN_SND_ECE; 1559 tp->t_flags |= TF_ACKNOW; 1560 } 1561 switch (iptos & IPTOS_ECN_MASK) { 1562 case IPTOS_ECN_CE: 1563 tp->t_flags2 |= TF2_ECN_SND_ECE; 1564 TCPSTAT_INC(tcps_ecn_ce); 1565 break; 1566 case IPTOS_ECN_ECT0: 1567 TCPSTAT_INC(tcps_ecn_ect0); 1568 break; 1569 case IPTOS_ECN_ECT1: 1570 TCPSTAT_INC(tcps_ecn_ect1); 1571 break; 1572 } 1573 1574 /* Process a packet differently from RFC3168. */ 1575 cc_ecnpkt_handler(tp, th, iptos); 1576 1577 /* Congestion experienced. */ 1578 if (thflags & TH_ECE) { 1579 cc_cong_signal(tp, th, CC_ECN); 1580 } 1581 } 1582 1583 /* 1584 * Parse options on any incoming segment. 1585 */ 1586 tcp_dooptions(&to, (u_char *)(th + 1), 1587 (th->th_off << 2) - sizeof(struct tcphdr), 1588 (thflags & TH_SYN) ? TO_SYN : 0); 1589 1590 #if defined(IPSEC_SUPPORT) || defined(TCP_SIGNATURE) 1591 if ((tp->t_flags & TF_SIGNATURE) != 0 && 1592 (to.to_flags & TOF_SIGNATURE) == 0) { 1593 TCPSTAT_INC(tcps_sig_err_sigopt); 1594 /* XXX: should drop? */ 1595 } 1596 #endif 1597 /* 1598 * If echoed timestamp is later than the current time, 1599 * fall back to non RFC1323 RTT calculation. Normalize 1600 * timestamp if syncookies were used when this connection 1601 * was established. 1602 */ 1603 if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) { 1604 to.to_tsecr -= tp->ts_offset; 1605 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks())) 1606 to.to_tsecr = 0; 1607 else if (tp->t_flags & TF_PREVVALID && 1608 tp->t_badrxtwin != 0 && SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 1609 cc_cong_signal(tp, th, CC_RTO_ERR); 1610 } 1611 /* 1612 * Process options only when we get SYN/ACK back. The SYN case 1613 * for incoming connections is handled in tcp_syncache. 1614 * According to RFC1323 the window field in a SYN (i.e., a <SYN> 1615 * or <SYN,ACK>) segment itself is never scaled. 1616 * XXX this is traditional behavior, may need to be cleaned up. 1617 */ 1618 if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) { 1619 /* Handle parallel SYN for ECN */ 1620 if (!(thflags & TH_ACK) && 1621 ((thflags & (TH_CWR | TH_ECE)) == (TH_CWR | TH_ECE)) && 1622 ((V_tcp_do_ecn == 1) || (V_tcp_do_ecn == 2))) { 1623 tp->t_flags2 |= TF2_ECN_PERMIT; 1624 tp->t_flags2 |= TF2_ECN_SND_ECE; 1625 TCPSTAT_INC(tcps_ecn_shs); 1626 } 1627 if ((to.to_flags & TOF_SCALE) && 1628 (tp->t_flags & TF_REQ_SCALE)) { 1629 tp->t_flags |= TF_RCVD_SCALE; 1630 tp->snd_scale = to.to_wscale; 1631 } else 1632 tp->t_flags &= ~TF_REQ_SCALE; 1633 /* 1634 * Initial send window. It will be updated with 1635 * the next incoming segment to the scaled value. 1636 */ 1637 tp->snd_wnd = th->th_win; 1638 if ((to.to_flags & TOF_TS) && 1639 (tp->t_flags & TF_REQ_TSTMP)) { 1640 tp->t_flags |= TF_RCVD_TSTMP; 1641 tp->ts_recent = to.to_tsval; 1642 tp->ts_recent_age = tcp_ts_getticks(); 1643 } else 1644 tp->t_flags &= ~TF_REQ_TSTMP; 1645 if (to.to_flags & TOF_MSS) 1646 tcp_mss(tp, to.to_mss); 1647 if ((tp->t_flags & TF_SACK_PERMIT) && 1648 (to.to_flags & TOF_SACKPERM) == 0) 1649 tp->t_flags &= ~TF_SACK_PERMIT; 1650 if (IS_FASTOPEN(tp->t_flags)) { 1651 if (to.to_flags & TOF_FASTOPEN) { 1652 uint16_t mss; 1653 1654 if (to.to_flags & TOF_MSS) 1655 mss = to.to_mss; 1656 else 1657 if ((tp->t_inpcb->inp_vflag & INP_IPV6) != 0) 1658 mss = TCP6_MSS; 1659 else 1660 mss = TCP_MSS; 1661 tcp_fastopen_update_cache(tp, mss, 1662 to.to_tfo_len, to.to_tfo_cookie); 1663 } else 1664 tcp_fastopen_disable_path(tp); 1665 } 1666 } 1667 1668 /* 1669 * If timestamps were negotiated during SYN/ACK they should 1670 * appear on every segment during this session and vice versa. 1671 */ 1672 if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) { 1673 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1674 log(LOG_DEBUG, "%s; %s: Timestamp missing, " 1675 "no action\n", s, __func__); 1676 free(s, M_TCPLOG); 1677 } 1678 } 1679 if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) { 1680 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 1681 log(LOG_DEBUG, "%s; %s: Timestamp not expected, " 1682 "no action\n", s, __func__); 1683 free(s, M_TCPLOG); 1684 } 1685 } 1686 1687 /* 1688 * Header prediction: check for the two common cases 1689 * of a uni-directional data xfer. If the packet has 1690 * no control flags, is in-sequence, the window didn't 1691 * change and we're not retransmitting, it's a 1692 * candidate. If the length is zero and the ack moved 1693 * forward, we're the sender side of the xfer. Just 1694 * free the data acked & wake any higher level process 1695 * that was blocked waiting for space. If the length 1696 * is non-zero and the ack didn't move, we're the 1697 * receiver side. If we're getting packets in-order 1698 * (the reassembly queue is empty), add the data to 1699 * the socket buffer and note that we need a delayed ack. 1700 * Make sure that the hidden state-flags are also off. 1701 * Since we check for TCPS_ESTABLISHED first, it can only 1702 * be TH_NEEDSYN. 1703 */ 1704 if (tp->t_state == TCPS_ESTABLISHED && 1705 th->th_seq == tp->rcv_nxt && 1706 (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 1707 tp->snd_nxt == tp->snd_max && 1708 tiwin && tiwin == tp->snd_wnd && 1709 ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) && 1710 SEGQ_EMPTY(tp) && 1711 ((to.to_flags & TOF_TS) == 0 || 1712 TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) { 1713 1714 /* 1715 * If last ACK falls within this segment's sequence numbers, 1716 * record the timestamp. 1717 * NOTE that the test is modified according to the latest 1718 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 1719 */ 1720 if ((to.to_flags & TOF_TS) != 0 && 1721 SEQ_LEQ(th->th_seq, tp->last_ack_sent)) { 1722 tp->ts_recent_age = tcp_ts_getticks(); 1723 tp->ts_recent = to.to_tsval; 1724 } 1725 1726 if (tlen == 0) { 1727 if (SEQ_GT(th->th_ack, tp->snd_una) && 1728 SEQ_LEQ(th->th_ack, tp->snd_max) && 1729 !IN_RECOVERY(tp->t_flags) && 1730 (to.to_flags & TOF_SACK) == 0 && 1731 TAILQ_EMPTY(&tp->snd_holes)) { 1732 /* 1733 * This is a pure ack for outstanding data. 1734 */ 1735 TCPSTAT_INC(tcps_predack); 1736 1737 /* 1738 * "bad retransmit" recovery without timestamps. 1739 */ 1740 if ((to.to_flags & TOF_TS) == 0 && 1741 tp->t_rxtshift == 1 && 1742 tp->t_flags & TF_PREVVALID && 1743 (int)(ticks - tp->t_badrxtwin) < 0) { 1744 cc_cong_signal(tp, th, CC_RTO_ERR); 1745 } 1746 1747 /* 1748 * Recalculate the transmit timer / rtt. 1749 * 1750 * Some boxes send broken timestamp replies 1751 * during the SYN+ACK phase, ignore 1752 * timestamps of 0 or we could calculate a 1753 * huge RTT and blow up the retransmit timer. 1754 */ 1755 if ((to.to_flags & TOF_TS) != 0 && 1756 to.to_tsecr) { 1757 uint32_t t; 1758 1759 t = tcp_ts_getticks() - to.to_tsecr; 1760 if (!tp->t_rttlow || tp->t_rttlow > t) 1761 tp->t_rttlow = t; 1762 tcp_xmit_timer(tp, 1763 TCP_TS_TO_TICKS(t) + 1); 1764 } else if (tp->t_rtttime && 1765 SEQ_GT(th->th_ack, tp->t_rtseq)) { 1766 if (!tp->t_rttlow || 1767 tp->t_rttlow > ticks - tp->t_rtttime) 1768 tp->t_rttlow = ticks - tp->t_rtttime; 1769 tcp_xmit_timer(tp, 1770 ticks - tp->t_rtttime); 1771 } 1772 acked = BYTES_THIS_ACK(tp, th); 1773 1774 #ifdef TCP_HHOOK 1775 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 1776 hhook_run_tcp_est_in(tp, th, &to); 1777 #endif 1778 1779 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 1780 TCPSTAT_ADD(tcps_rcvackbyte, acked); 1781 sbdrop(&so->so_snd, acked); 1782 if (SEQ_GT(tp->snd_una, tp->snd_recover) && 1783 SEQ_LEQ(th->th_ack, tp->snd_recover)) 1784 tp->snd_recover = th->th_ack - 1; 1785 1786 /* 1787 * Let the congestion control algorithm update 1788 * congestion control related information. This 1789 * typically means increasing the congestion 1790 * window. 1791 */ 1792 cc_ack_received(tp, th, nsegs, CC_ACK); 1793 1794 tp->snd_una = th->th_ack; 1795 /* 1796 * Pull snd_wl2 up to prevent seq wrap relative 1797 * to th_ack. 1798 */ 1799 tp->snd_wl2 = th->th_ack; 1800 tp->t_dupacks = 0; 1801 m_freem(m); 1802 1803 /* 1804 * If all outstanding data are acked, stop 1805 * retransmit timer, otherwise restart timer 1806 * using current (possibly backed-off) value. 1807 * If process is waiting for space, 1808 * wakeup/selwakeup/signal. If data 1809 * are ready to send, let tcp_output 1810 * decide between more output or persist. 1811 */ 1812 #ifdef TCPDEBUG 1813 if (so->so_options & SO_DEBUG) 1814 tcp_trace(TA_INPUT, ostate, tp, 1815 (void *)tcp_saveipgen, 1816 &tcp_savetcp, 0); 1817 #endif 1818 TCP_PROBE3(debug__input, tp, th, m); 1819 if (tp->snd_una == tp->snd_max) 1820 tcp_timer_activate(tp, TT_REXMT, 0); 1821 else if (!tcp_timer_active(tp, TT_PERSIST)) 1822 tcp_timer_activate(tp, TT_REXMT, 1823 tp->t_rxtcur); 1824 sowwakeup(so); 1825 if (sbavail(&so->so_snd)) 1826 (void) tp->t_fb->tfb_tcp_output(tp); 1827 goto check_delack; 1828 } 1829 } else if (th->th_ack == tp->snd_una && 1830 tlen <= sbspace(&so->so_rcv)) { 1831 int newsize = 0; /* automatic sockbuf scaling */ 1832 1833 /* 1834 * This is a pure, in-sequence data packet with 1835 * nothing on the reassembly queue and we have enough 1836 * buffer space to take it. 1837 */ 1838 /* Clean receiver SACK report if present */ 1839 if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks) 1840 tcp_clean_sackreport(tp); 1841 TCPSTAT_INC(tcps_preddat); 1842 tp->rcv_nxt += tlen; 1843 if (tlen && 1844 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 1845 (tp->t_fbyte_in == 0)) { 1846 tp->t_fbyte_in = ticks; 1847 if (tp->t_fbyte_in == 0) 1848 tp->t_fbyte_in = 1; 1849 if (tp->t_fbyte_out && tp->t_fbyte_in) 1850 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 1851 } 1852 /* 1853 * Pull snd_wl1 up to prevent seq wrap relative to 1854 * th_seq. 1855 */ 1856 tp->snd_wl1 = th->th_seq; 1857 /* 1858 * Pull rcv_up up to prevent seq wrap relative to 1859 * rcv_nxt. 1860 */ 1861 tp->rcv_up = tp->rcv_nxt; 1862 TCPSTAT_ADD(tcps_rcvpack, nsegs); 1863 TCPSTAT_ADD(tcps_rcvbyte, tlen); 1864 #ifdef TCPDEBUG 1865 if (so->so_options & SO_DEBUG) 1866 tcp_trace(TA_INPUT, ostate, tp, 1867 (void *)tcp_saveipgen, &tcp_savetcp, 0); 1868 #endif 1869 TCP_PROBE3(debug__input, tp, th, m); 1870 1871 newsize = tcp_autorcvbuf(m, th, so, tp, tlen); 1872 1873 /* Add data to socket buffer. */ 1874 SOCKBUF_LOCK(&so->so_rcv); 1875 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 1876 m_freem(m); 1877 } else { 1878 /* 1879 * Set new socket buffer size. 1880 * Give up when limit is reached. 1881 */ 1882 if (newsize) 1883 if (!sbreserve_locked(&so->so_rcv, 1884 newsize, so, NULL)) 1885 so->so_rcv.sb_flags &= ~SB_AUTOSIZE; 1886 m_adj(m, drop_hdrlen); /* delayed header drop */ 1887 sbappendstream_locked(&so->so_rcv, m, 0); 1888 } 1889 /* NB: sorwakeup_locked() does an implicit unlock. */ 1890 sorwakeup_locked(so); 1891 if (DELAY_ACK(tp, tlen)) { 1892 tp->t_flags |= TF_DELACK; 1893 } else { 1894 tp->t_flags |= TF_ACKNOW; 1895 tp->t_fb->tfb_tcp_output(tp); 1896 } 1897 goto check_delack; 1898 } 1899 } 1900 1901 /* 1902 * Calculate amount of space in receive window, 1903 * and then do TCP input processing. 1904 * Receive window is amount of space in rcv queue, 1905 * but not less than advertised window. 1906 */ 1907 win = sbspace(&so->so_rcv); 1908 if (win < 0) 1909 win = 0; 1910 tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 1911 1912 switch (tp->t_state) { 1913 1914 /* 1915 * If the state is SYN_RECEIVED: 1916 * if seg contains an ACK, but not for our SYN/ACK, send a RST. 1917 */ 1918 case TCPS_SYN_RECEIVED: 1919 if ((thflags & TH_ACK) && 1920 (SEQ_LEQ(th->th_ack, tp->snd_una) || 1921 SEQ_GT(th->th_ack, tp->snd_max))) { 1922 rstreason = BANDLIM_RST_OPENPORT; 1923 goto dropwithreset; 1924 } 1925 if (IS_FASTOPEN(tp->t_flags)) { 1926 /* 1927 * When a TFO connection is in SYN_RECEIVED, the 1928 * only valid packets are the initial SYN, a 1929 * retransmit/copy of the initial SYN (possibly with 1930 * a subset of the original data), a valid ACK, a 1931 * FIN, or a RST. 1932 */ 1933 if ((thflags & (TH_SYN|TH_ACK)) == (TH_SYN|TH_ACK)) { 1934 rstreason = BANDLIM_RST_OPENPORT; 1935 goto dropwithreset; 1936 } else if (thflags & TH_SYN) { 1937 /* non-initial SYN is ignored */ 1938 if ((tcp_timer_active(tp, TT_DELACK) || 1939 tcp_timer_active(tp, TT_REXMT))) 1940 goto drop; 1941 } else if (!(thflags & (TH_ACK|TH_FIN|TH_RST))) { 1942 goto drop; 1943 } 1944 } 1945 break; 1946 1947 /* 1948 * If the state is SYN_SENT: 1949 * if seg contains a RST with valid ACK (SEQ.ACK has already 1950 * been verified), then drop the connection. 1951 * if seg contains a RST without an ACK, drop the seg. 1952 * if seg does not contain SYN, then drop the seg. 1953 * Otherwise this is an acceptable SYN segment 1954 * initialize tp->rcv_nxt and tp->irs 1955 * if seg contains ack then advance tp->snd_una 1956 * if seg contains an ECE and ECN support is enabled, the stream 1957 * is ECN capable. 1958 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 1959 * arrange for segment to be acked (eventually) 1960 * continue processing rest of data/controls, beginning with URG 1961 */ 1962 case TCPS_SYN_SENT: 1963 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) { 1964 TCP_PROBE5(connect__refused, NULL, tp, 1965 m, tp, th); 1966 tp = tcp_drop(tp, ECONNREFUSED); 1967 } 1968 if (thflags & TH_RST) 1969 goto drop; 1970 if (!(thflags & TH_SYN)) 1971 goto drop; 1972 1973 tp->irs = th->th_seq; 1974 tcp_rcvseqinit(tp); 1975 if (thflags & TH_ACK) { 1976 int tfo_partial_ack = 0; 1977 1978 TCPSTAT_INC(tcps_connects); 1979 soisconnected(so); 1980 #ifdef MAC 1981 mac_socketpeer_set_from_mbuf(m, so); 1982 #endif 1983 /* Do window scaling on this connection? */ 1984 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1985 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1986 tp->rcv_scale = tp->request_r_scale; 1987 } 1988 tp->rcv_adv += min(tp->rcv_wnd, 1989 TCP_MAXWIN << tp->rcv_scale); 1990 tp->snd_una++; /* SYN is acked */ 1991 /* 1992 * If not all the data that was sent in the TFO SYN 1993 * has been acked, resend the remainder right away. 1994 */ 1995 if (IS_FASTOPEN(tp->t_flags) && 1996 (tp->snd_una != tp->snd_max)) { 1997 tp->snd_nxt = th->th_ack; 1998 tfo_partial_ack = 1; 1999 } 2000 /* 2001 * If there's data, delay ACK; if there's also a FIN 2002 * ACKNOW will be turned on later. 2003 */ 2004 if (DELAY_ACK(tp, tlen) && tlen != 0 && !tfo_partial_ack) 2005 tcp_timer_activate(tp, TT_DELACK, 2006 tcp_delacktime); 2007 else 2008 tp->t_flags |= TF_ACKNOW; 2009 2010 if (((thflags & (TH_CWR | TH_ECE)) == TH_ECE) && 2011 (V_tcp_do_ecn == 1)) { 2012 tp->t_flags2 |= TF2_ECN_PERMIT; 2013 TCPSTAT_INC(tcps_ecn_shs); 2014 } 2015 2016 /* 2017 * Received <SYN,ACK> in SYN_SENT[*] state. 2018 * Transitions: 2019 * SYN_SENT --> ESTABLISHED 2020 * SYN_SENT* --> FIN_WAIT_1 2021 */ 2022 tp->t_starttime = ticks; 2023 if (tp->t_flags & TF_NEEDFIN) { 2024 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2025 tp->t_flags &= ~TF_NEEDFIN; 2026 thflags &= ~TH_SYN; 2027 } else { 2028 tcp_state_change(tp, TCPS_ESTABLISHED); 2029 TCP_PROBE5(connect__established, NULL, tp, 2030 m, tp, th); 2031 cc_conn_init(tp); 2032 tcp_timer_activate(tp, TT_KEEP, 2033 TP_KEEPIDLE(tp)); 2034 } 2035 } else { 2036 /* 2037 * Received initial SYN in SYN-SENT[*] state => 2038 * simultaneous open. 2039 * If it succeeds, connection is * half-synchronized. 2040 * Otherwise, do 3-way handshake: 2041 * SYN-SENT -> SYN-RECEIVED 2042 * SYN-SENT* -> SYN-RECEIVED* 2043 */ 2044 tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN); 2045 tcp_timer_activate(tp, TT_REXMT, 0); 2046 tcp_state_change(tp, TCPS_SYN_RECEIVED); 2047 } 2048 2049 INP_WLOCK_ASSERT(tp->t_inpcb); 2050 2051 /* 2052 * Advance th->th_seq to correspond to first data byte. 2053 * If data, trim to stay within window, 2054 * dropping FIN if necessary. 2055 */ 2056 th->th_seq++; 2057 if (tlen > tp->rcv_wnd) { 2058 todrop = tlen - tp->rcv_wnd; 2059 m_adj(m, -todrop); 2060 tlen = tp->rcv_wnd; 2061 thflags &= ~TH_FIN; 2062 TCPSTAT_INC(tcps_rcvpackafterwin); 2063 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2064 } 2065 tp->snd_wl1 = th->th_seq - 1; 2066 tp->rcv_up = th->th_seq; 2067 /* 2068 * Client side of transaction: already sent SYN and data. 2069 * If the remote host used T/TCP to validate the SYN, 2070 * our data will be ACK'd; if so, enter normal data segment 2071 * processing in the middle of step 5, ack processing. 2072 * Otherwise, goto step 6. 2073 */ 2074 if (thflags & TH_ACK) 2075 goto process_ACK; 2076 2077 goto step6; 2078 2079 /* 2080 * If the state is LAST_ACK or CLOSING or TIME_WAIT: 2081 * do normal processing. 2082 * 2083 * NB: Leftover from RFC1644 T/TCP. Cases to be reused later. 2084 */ 2085 case TCPS_LAST_ACK: 2086 case TCPS_CLOSING: 2087 break; /* continue normal processing */ 2088 } 2089 2090 /* 2091 * States other than LISTEN or SYN_SENT. 2092 * First check the RST flag and sequence number since reset segments 2093 * are exempt from the timestamp and connection count tests. This 2094 * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix 2095 * below which allowed reset segments in half the sequence space 2096 * to fall though and be processed (which gives forged reset 2097 * segments with a random sequence number a 50 percent chance of 2098 * killing a connection). 2099 * Then check timestamp, if present. 2100 * Then check the connection count, if present. 2101 * Then check that at least some bytes of segment are within 2102 * receive window. If segment begins before rcv_nxt, 2103 * drop leading data (and SYN); if nothing left, just ack. 2104 */ 2105 if (thflags & TH_RST) { 2106 /* 2107 * RFC5961 Section 3.2 2108 * 2109 * - RST drops connection only if SEG.SEQ == RCV.NXT. 2110 * - If RST is in window, we send challenge ACK. 2111 * 2112 * Note: to take into account delayed ACKs, we should 2113 * test against last_ack_sent instead of rcv_nxt. 2114 * Note 2: we handle special case of closed window, not 2115 * covered by the RFC. 2116 */ 2117 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2118 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) || 2119 (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) { 2120 2121 KASSERT(tp->t_state != TCPS_SYN_SENT, 2122 ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p", 2123 __func__, th, tp)); 2124 2125 if (V_tcp_insecure_rst || 2126 tp->last_ack_sent == th->th_seq) { 2127 TCPSTAT_INC(tcps_drops); 2128 /* Drop the connection. */ 2129 switch (tp->t_state) { 2130 case TCPS_SYN_RECEIVED: 2131 so->so_error = ECONNREFUSED; 2132 goto close; 2133 case TCPS_ESTABLISHED: 2134 case TCPS_FIN_WAIT_1: 2135 case TCPS_FIN_WAIT_2: 2136 case TCPS_CLOSE_WAIT: 2137 case TCPS_CLOSING: 2138 case TCPS_LAST_ACK: 2139 so->so_error = ECONNRESET; 2140 close: 2141 /* FALLTHROUGH */ 2142 default: 2143 tp = tcp_close(tp); 2144 } 2145 } else { 2146 TCPSTAT_INC(tcps_badrst); 2147 /* Send challenge ACK. */ 2148 tcp_respond(tp, mtod(m, void *), th, m, 2149 tp->rcv_nxt, tp->snd_nxt, TH_ACK); 2150 tp->last_ack_sent = tp->rcv_nxt; 2151 m = NULL; 2152 } 2153 } 2154 goto drop; 2155 } 2156 2157 /* 2158 * RFC5961 Section 4.2 2159 * Send challenge ACK for any SYN in synchronized state. 2160 */ 2161 if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT && 2162 tp->t_state != TCPS_SYN_RECEIVED) { 2163 TCPSTAT_INC(tcps_badsyn); 2164 if (V_tcp_insecure_syn && 2165 SEQ_GEQ(th->th_seq, tp->last_ack_sent) && 2166 SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) { 2167 tp = tcp_drop(tp, ECONNRESET); 2168 rstreason = BANDLIM_UNLIMITED; 2169 } else { 2170 /* Send challenge ACK. */ 2171 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 2172 tp->snd_nxt, TH_ACK); 2173 tp->last_ack_sent = tp->rcv_nxt; 2174 m = NULL; 2175 } 2176 goto drop; 2177 } 2178 2179 /* 2180 * RFC 1323 PAWS: If we have a timestamp reply on this segment 2181 * and it's less than ts_recent, drop it. 2182 */ 2183 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 2184 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 2185 2186 /* Check to see if ts_recent is over 24 days old. */ 2187 if (tcp_ts_getticks() - tp->ts_recent_age > TCP_PAWS_IDLE) { 2188 /* 2189 * Invalidate ts_recent. If this segment updates 2190 * ts_recent, the age will be reset later and ts_recent 2191 * will get a valid value. If it does not, setting 2192 * ts_recent to zero will at least satisfy the 2193 * requirement that zero be placed in the timestamp 2194 * echo reply when ts_recent isn't valid. The 2195 * age isn't reset until we get a valid ts_recent 2196 * because we don't want out-of-order segments to be 2197 * dropped when ts_recent is old. 2198 */ 2199 tp->ts_recent = 0; 2200 } else { 2201 TCPSTAT_INC(tcps_rcvduppack); 2202 TCPSTAT_ADD(tcps_rcvdupbyte, tlen); 2203 TCPSTAT_INC(tcps_pawsdrop); 2204 if (tlen) 2205 goto dropafterack; 2206 goto drop; 2207 } 2208 } 2209 2210 /* 2211 * In the SYN-RECEIVED state, validate that the packet belongs to 2212 * this connection before trimming the data to fit the receive 2213 * window. Check the sequence number versus IRS since we know 2214 * the sequence numbers haven't wrapped. This is a partial fix 2215 * for the "LAND" DoS attack. 2216 */ 2217 if (tp->t_state == TCPS_SYN_RECEIVED && SEQ_LT(th->th_seq, tp->irs)) { 2218 rstreason = BANDLIM_RST_OPENPORT; 2219 goto dropwithreset; 2220 } 2221 2222 todrop = tp->rcv_nxt - th->th_seq; 2223 if (todrop > 0) { 2224 if (thflags & TH_SYN) { 2225 thflags &= ~TH_SYN; 2226 th->th_seq++; 2227 if (th->th_urp > 1) 2228 th->th_urp--; 2229 else 2230 thflags &= ~TH_URG; 2231 todrop--; 2232 } 2233 /* 2234 * Following if statement from Stevens, vol. 2, p. 960. 2235 */ 2236 if (todrop > tlen 2237 || (todrop == tlen && (thflags & TH_FIN) == 0)) { 2238 /* 2239 * Any valid FIN must be to the left of the window. 2240 * At this point the FIN must be a duplicate or out 2241 * of sequence; drop it. 2242 */ 2243 thflags &= ~TH_FIN; 2244 2245 /* 2246 * Send an ACK to resynchronize and drop any data. 2247 * But keep on processing for RST or ACK. 2248 */ 2249 tp->t_flags |= TF_ACKNOW; 2250 todrop = tlen; 2251 TCPSTAT_INC(tcps_rcvduppack); 2252 TCPSTAT_ADD(tcps_rcvdupbyte, todrop); 2253 } else { 2254 TCPSTAT_INC(tcps_rcvpartduppack); 2255 TCPSTAT_ADD(tcps_rcvpartdupbyte, todrop); 2256 } 2257 /* 2258 * DSACK - add SACK block for dropped range 2259 */ 2260 if ((todrop > 0) && (tp->t_flags & TF_SACK_PERMIT)) { 2261 tcp_update_sack_list(tp, th->th_seq, 2262 th->th_seq + todrop); 2263 /* 2264 * ACK now, as the next in-sequence segment 2265 * will clear the DSACK block again 2266 */ 2267 tp->t_flags |= TF_ACKNOW; 2268 } 2269 drop_hdrlen += todrop; /* drop from the top afterwards */ 2270 th->th_seq += todrop; 2271 tlen -= todrop; 2272 if (th->th_urp > todrop) 2273 th->th_urp -= todrop; 2274 else { 2275 thflags &= ~TH_URG; 2276 th->th_urp = 0; 2277 } 2278 } 2279 2280 /* 2281 * If new data are received on a connection after the 2282 * user processes are gone, then RST the other end. 2283 */ 2284 if ((so->so_state & SS_NOFDREF) && 2285 tp->t_state > TCPS_CLOSE_WAIT && tlen) { 2286 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) { 2287 log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data " 2288 "after socket was closed, " 2289 "sending RST and removing tcpcb\n", 2290 s, __func__, tcpstates[tp->t_state], tlen); 2291 free(s, M_TCPLOG); 2292 } 2293 tp = tcp_close(tp); 2294 TCPSTAT_INC(tcps_rcvafterclose); 2295 rstreason = BANDLIM_UNLIMITED; 2296 goto dropwithreset; 2297 } 2298 2299 /* 2300 * If segment ends after window, drop trailing data 2301 * (and PUSH and FIN); if nothing left, just ACK. 2302 */ 2303 todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd); 2304 if (todrop > 0) { 2305 TCPSTAT_INC(tcps_rcvpackafterwin); 2306 if (todrop >= tlen) { 2307 TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen); 2308 /* 2309 * If window is closed can only take segments at 2310 * window edge, and have to drop data and PUSH from 2311 * incoming segments. Continue processing, but 2312 * remember to ack. Otherwise, drop segment 2313 * and ack. 2314 */ 2315 if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) { 2316 tp->t_flags |= TF_ACKNOW; 2317 TCPSTAT_INC(tcps_rcvwinprobe); 2318 } else 2319 goto dropafterack; 2320 } else 2321 TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop); 2322 m_adj(m, -todrop); 2323 tlen -= todrop; 2324 thflags &= ~(TH_PUSH|TH_FIN); 2325 } 2326 2327 /* 2328 * If last ACK falls within this segment's sequence numbers, 2329 * record its timestamp. 2330 * NOTE: 2331 * 1) That the test incorporates suggestions from the latest 2332 * proposal of the tcplw@cray.com list (Braden 1993/04/26). 2333 * 2) That updating only on newer timestamps interferes with 2334 * our earlier PAWS tests, so this check should be solely 2335 * predicated on the sequence space of this segment. 2336 * 3) That we modify the segment boundary check to be 2337 * Last.ACK.Sent <= SEG.SEQ + SEG.Len 2338 * instead of RFC1323's 2339 * Last.ACK.Sent < SEG.SEQ + SEG.Len, 2340 * This modified check allows us to overcome RFC1323's 2341 * limitations as described in Stevens TCP/IP Illustrated 2342 * Vol. 2 p.869. In such cases, we can still calculate the 2343 * RTT correctly when RCV.NXT == Last.ACK.Sent. 2344 */ 2345 if ((to.to_flags & TOF_TS) != 0 && 2346 SEQ_LEQ(th->th_seq, tp->last_ack_sent) && 2347 SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen + 2348 ((thflags & (TH_SYN|TH_FIN)) != 0))) { 2349 tp->ts_recent_age = tcp_ts_getticks(); 2350 tp->ts_recent = to.to_tsval; 2351 } 2352 2353 /* 2354 * If the ACK bit is off: if in SYN-RECEIVED state or SENDSYN 2355 * flag is on (half-synchronized state), then queue data for 2356 * later processing; else drop segment and return. 2357 */ 2358 if ((thflags & TH_ACK) == 0) { 2359 if (tp->t_state == TCPS_SYN_RECEIVED || 2360 (tp->t_flags & TF_NEEDSYN)) { 2361 if (tp->t_state == TCPS_SYN_RECEIVED && 2362 IS_FASTOPEN(tp->t_flags)) { 2363 tp->snd_wnd = tiwin; 2364 cc_conn_init(tp); 2365 } 2366 goto step6; 2367 } else if (tp->t_flags & TF_ACKNOW) 2368 goto dropafterack; 2369 else 2370 goto drop; 2371 } 2372 2373 /* 2374 * Ack processing. 2375 */ 2376 switch (tp->t_state) { 2377 2378 /* 2379 * In SYN_RECEIVED state, the ack ACKs our SYN, so enter 2380 * ESTABLISHED state and continue processing. 2381 * The ACK was checked above. 2382 */ 2383 case TCPS_SYN_RECEIVED: 2384 2385 TCPSTAT_INC(tcps_connects); 2386 soisconnected(so); 2387 /* Do window scaling? */ 2388 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2389 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2390 tp->rcv_scale = tp->request_r_scale; 2391 } 2392 tp->snd_wnd = tiwin; 2393 /* 2394 * Make transitions: 2395 * SYN-RECEIVED -> ESTABLISHED 2396 * SYN-RECEIVED* -> FIN-WAIT-1 2397 */ 2398 tp->t_starttime = ticks; 2399 if (IS_FASTOPEN(tp->t_flags) && tp->t_tfo_pending) { 2400 tcp_fastopen_decrement_counter(tp->t_tfo_pending); 2401 tp->t_tfo_pending = NULL; 2402 } 2403 if (tp->t_flags & TF_NEEDFIN) { 2404 tcp_state_change(tp, TCPS_FIN_WAIT_1); 2405 tp->t_flags &= ~TF_NEEDFIN; 2406 } else { 2407 tcp_state_change(tp, TCPS_ESTABLISHED); 2408 TCP_PROBE5(accept__established, NULL, tp, 2409 m, tp, th); 2410 /* 2411 * TFO connections call cc_conn_init() during SYN 2412 * processing. Calling it again here for such 2413 * connections is not harmless as it would undo the 2414 * snd_cwnd reduction that occurs when a TFO SYN|ACK 2415 * is retransmitted. 2416 */ 2417 if (!IS_FASTOPEN(tp->t_flags)) 2418 cc_conn_init(tp); 2419 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp)); 2420 } 2421 /* 2422 * Account for the ACK of our SYN prior to 2423 * regular ACK processing below, except for 2424 * simultaneous SYN, which is handled later. 2425 */ 2426 if (SEQ_GT(th->th_ack, tp->snd_una) && !(tp->t_flags & TF_NEEDSYN)) 2427 incforsyn = 1; 2428 /* 2429 * If segment contains data or ACK, will call tcp_reass() 2430 * later; if not, do so now to pass queued data to user. 2431 */ 2432 if (tlen == 0 && (thflags & TH_FIN) == 0) 2433 (void) tcp_reass(tp, (struct tcphdr *)0, NULL, 0, 2434 (struct mbuf *)0); 2435 tp->snd_wl1 = th->th_seq - 1; 2436 /* FALLTHROUGH */ 2437 2438 /* 2439 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 2440 * ACKs. If the ack is in the range 2441 * tp->snd_una < th->th_ack <= tp->snd_max 2442 * then advance tp->snd_una to th->th_ack and drop 2443 * data from the retransmission queue. If this ACK reflects 2444 * more up to date window information we update our window information. 2445 */ 2446 case TCPS_ESTABLISHED: 2447 case TCPS_FIN_WAIT_1: 2448 case TCPS_FIN_WAIT_2: 2449 case TCPS_CLOSE_WAIT: 2450 case TCPS_CLOSING: 2451 case TCPS_LAST_ACK: 2452 if (SEQ_GT(th->th_ack, tp->snd_max)) { 2453 TCPSTAT_INC(tcps_rcvacktoomuch); 2454 goto dropafterack; 2455 } 2456 if ((tp->t_flags & TF_SACK_PERMIT) && 2457 ((to.to_flags & TOF_SACK) || 2458 !TAILQ_EMPTY(&tp->snd_holes))) 2459 sack_changed = tcp_sack_doack(tp, &to, th->th_ack); 2460 else 2461 /* 2462 * Reset the value so that previous (valid) value 2463 * from the last ack with SACK doesn't get used. 2464 */ 2465 tp->sackhint.sacked_bytes = 0; 2466 2467 #ifdef TCP_HHOOK 2468 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */ 2469 hhook_run_tcp_est_in(tp, th, &to); 2470 #endif 2471 2472 if (SEQ_LEQ(th->th_ack, tp->snd_una)) { 2473 u_int maxseg; 2474 2475 maxseg = tcp_maxseg(tp); 2476 if (tlen == 0 && 2477 (tiwin == tp->snd_wnd || 2478 (tp->t_flags & TF_SACK_PERMIT))) { 2479 /* 2480 * If this is the first time we've seen a 2481 * FIN from the remote, this is not a 2482 * duplicate and it needs to be processed 2483 * normally. This happens during a 2484 * simultaneous close. 2485 */ 2486 if ((thflags & TH_FIN) && 2487 (TCPS_HAVERCVDFIN(tp->t_state) == 0)) { 2488 tp->t_dupacks = 0; 2489 break; 2490 } 2491 TCPSTAT_INC(tcps_rcvdupack); 2492 /* 2493 * If we have outstanding data (other than 2494 * a window probe), this is a completely 2495 * duplicate ack (ie, window info didn't 2496 * change and FIN isn't set), 2497 * the ack is the biggest we've 2498 * seen and we've seen exactly our rexmt 2499 * threshold of them, assume a packet 2500 * has been dropped and retransmit it. 2501 * Kludge snd_nxt & the congestion 2502 * window so we send only this one 2503 * packet. 2504 * 2505 * We know we're losing at the current 2506 * window size so do congestion avoidance 2507 * (set ssthresh to half the current window 2508 * and pull our congestion window back to 2509 * the new ssthresh). 2510 * 2511 * Dup acks mean that packets have left the 2512 * network (they're now cached at the receiver) 2513 * so bump cwnd by the amount in the receiver 2514 * to keep a constant cwnd packets in the 2515 * network. 2516 * 2517 * When using TCP ECN, notify the peer that 2518 * we reduced the cwnd. 2519 */ 2520 /* 2521 * Following 2 kinds of acks should not affect 2522 * dupack counting: 2523 * 1) Old acks 2524 * 2) Acks with SACK but without any new SACK 2525 * information in them. These could result from 2526 * any anomaly in the network like a switch 2527 * duplicating packets or a possible DoS attack. 2528 */ 2529 if (th->th_ack != tp->snd_una || 2530 ((tp->t_flags & TF_SACK_PERMIT) && 2531 !sack_changed)) 2532 break; 2533 else if (!tcp_timer_active(tp, TT_REXMT)) 2534 tp->t_dupacks = 0; 2535 else if (++tp->t_dupacks > tcprexmtthresh || 2536 IN_FASTRECOVERY(tp->t_flags)) { 2537 cc_ack_received(tp, th, nsegs, 2538 CC_DUPACK); 2539 if ((tp->t_flags & TF_SACK_PERMIT) && 2540 IN_FASTRECOVERY(tp->t_flags)) { 2541 int awnd; 2542 2543 /* 2544 * Compute the amount of data in flight first. 2545 * We can inject new data into the pipe iff 2546 * we have less than 1/2 the original window's 2547 * worth of data in flight. 2548 */ 2549 if (V_tcp_do_rfc6675_pipe) 2550 awnd = tcp_compute_pipe(tp); 2551 else 2552 awnd = (tp->snd_nxt - tp->snd_fack) + 2553 tp->sackhint.sack_bytes_rexmit; 2554 2555 if (awnd < tp->snd_ssthresh) { 2556 tp->snd_cwnd += maxseg; 2557 if (tp->snd_cwnd > tp->snd_ssthresh) 2558 tp->snd_cwnd = tp->snd_ssthresh; 2559 } 2560 } else 2561 tp->snd_cwnd += maxseg; 2562 (void) tp->t_fb->tfb_tcp_output(tp); 2563 goto drop; 2564 } else if (tp->t_dupacks == tcprexmtthresh) { 2565 tcp_seq onxt = tp->snd_nxt; 2566 2567 /* 2568 * If we're doing sack, check to 2569 * see if we're already in sack 2570 * recovery. If we're not doing sack, 2571 * check to see if we're in newreno 2572 * recovery. 2573 */ 2574 if (tp->t_flags & TF_SACK_PERMIT) { 2575 if (IN_FASTRECOVERY(tp->t_flags)) { 2576 tp->t_dupacks = 0; 2577 break; 2578 } 2579 } else { 2580 if (SEQ_LEQ(th->th_ack, 2581 tp->snd_recover)) { 2582 tp->t_dupacks = 0; 2583 break; 2584 } 2585 } 2586 /* Congestion signal before ack. */ 2587 cc_cong_signal(tp, th, CC_NDUPACK); 2588 cc_ack_received(tp, th, nsegs, 2589 CC_DUPACK); 2590 tcp_timer_activate(tp, TT_REXMT, 0); 2591 tp->t_rtttime = 0; 2592 if (tp->t_flags & TF_SACK_PERMIT) { 2593 TCPSTAT_INC( 2594 tcps_sack_recovery_episode); 2595 tp->snd_recover = tp->snd_nxt; 2596 tp->snd_cwnd = maxseg; 2597 (void) tp->t_fb->tfb_tcp_output(tp); 2598 goto drop; 2599 } 2600 tp->snd_nxt = th->th_ack; 2601 tp->snd_cwnd = maxseg; 2602 (void) tp->t_fb->tfb_tcp_output(tp); 2603 KASSERT(tp->snd_limited <= 2, 2604 ("%s: tp->snd_limited too big", 2605 __func__)); 2606 tp->snd_cwnd = tp->snd_ssthresh + 2607 maxseg * 2608 (tp->t_dupacks - tp->snd_limited); 2609 if (SEQ_GT(onxt, tp->snd_nxt)) 2610 tp->snd_nxt = onxt; 2611 goto drop; 2612 } else if (V_tcp_do_rfc3042) { 2613 /* 2614 * Process first and second duplicate 2615 * ACKs. Each indicates a segment 2616 * leaving the network, creating room 2617 * for more. Make sure we can send a 2618 * packet on reception of each duplicate 2619 * ACK by increasing snd_cwnd by one 2620 * segment. Restore the original 2621 * snd_cwnd after packet transmission. 2622 */ 2623 cc_ack_received(tp, th, nsegs, 2624 CC_DUPACK); 2625 uint32_t oldcwnd = tp->snd_cwnd; 2626 tcp_seq oldsndmax = tp->snd_max; 2627 u_int sent; 2628 int avail; 2629 2630 KASSERT(tp->t_dupacks == 1 || 2631 tp->t_dupacks == 2, 2632 ("%s: dupacks not 1 or 2", 2633 __func__)); 2634 if (tp->t_dupacks == 1) 2635 tp->snd_limited = 0; 2636 tp->snd_cwnd = 2637 (tp->snd_nxt - tp->snd_una) + 2638 (tp->t_dupacks - tp->snd_limited) * 2639 maxseg; 2640 /* 2641 * Only call tcp_output when there 2642 * is new data available to be sent. 2643 * Otherwise we would send pure ACKs. 2644 */ 2645 SOCKBUF_LOCK(&so->so_snd); 2646 avail = sbavail(&so->so_snd) - 2647 (tp->snd_nxt - tp->snd_una); 2648 SOCKBUF_UNLOCK(&so->so_snd); 2649 if (avail > 0) 2650 (void) tp->t_fb->tfb_tcp_output(tp); 2651 sent = tp->snd_max - oldsndmax; 2652 if (sent > maxseg) { 2653 KASSERT((tp->t_dupacks == 2 && 2654 tp->snd_limited == 0) || 2655 (sent == maxseg + 1 && 2656 tp->t_flags & TF_SENTFIN), 2657 ("%s: sent too much", 2658 __func__)); 2659 tp->snd_limited = 2; 2660 } else if (sent > 0) 2661 ++tp->snd_limited; 2662 tp->snd_cwnd = oldcwnd; 2663 goto drop; 2664 } 2665 } 2666 break; 2667 } else { 2668 /* 2669 * This ack is advancing the left edge, reset the 2670 * counter. 2671 */ 2672 tp->t_dupacks = 0; 2673 /* 2674 * If this ack also has new SACK info, increment the 2675 * counter as per rfc6675. The variable 2676 * sack_changed tracks all changes to the SACK 2677 * scoreboard, including when partial ACKs without 2678 * SACK options are received, and clear the scoreboard 2679 * from the left side. Such partial ACKs should not be 2680 * counted as dupacks here. 2681 */ 2682 if ((tp->t_flags & TF_SACK_PERMIT) && 2683 (to.to_flags & TOF_SACK) && 2684 sack_changed) 2685 tp->t_dupacks++; 2686 } 2687 2688 KASSERT(SEQ_GT(th->th_ack, tp->snd_una), 2689 ("%s: th_ack <= snd_una", __func__)); 2690 2691 /* 2692 * If the congestion window was inflated to account 2693 * for the other side's cached packets, retract it. 2694 */ 2695 if (IN_FASTRECOVERY(tp->t_flags)) { 2696 if (SEQ_LT(th->th_ack, tp->snd_recover)) { 2697 if (tp->t_flags & TF_SACK_PERMIT) 2698 tcp_sack_partialack(tp, th); 2699 else 2700 tcp_newreno_partial_ack(tp, th); 2701 } else 2702 cc_post_recovery(tp, th); 2703 } 2704 /* 2705 * If we reach this point, ACK is not a duplicate, 2706 * i.e., it ACKs something we sent. 2707 */ 2708 if (tp->t_flags & TF_NEEDSYN) { 2709 /* 2710 * T/TCP: Connection was half-synchronized, and our 2711 * SYN has been ACK'd (so connection is now fully 2712 * synchronized). Go to non-starred state, 2713 * increment snd_una for ACK of SYN, and check if 2714 * we can do window scaling. 2715 */ 2716 tp->t_flags &= ~TF_NEEDSYN; 2717 tp->snd_una++; 2718 /* Do window scaling? */ 2719 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 2720 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 2721 tp->rcv_scale = tp->request_r_scale; 2722 /* Send window already scaled. */ 2723 } 2724 } 2725 2726 process_ACK: 2727 INP_WLOCK_ASSERT(tp->t_inpcb); 2728 2729 /* 2730 * Adjust for the SYN bit in sequence space, 2731 * but don't account for it in cwnd calculations. 2732 * This is for the SYN_RECEIVED, non-simultaneous 2733 * SYN case. SYN_SENT and simultaneous SYN are 2734 * treated elsewhere. 2735 */ 2736 if (incforsyn) 2737 tp->snd_una++; 2738 acked = BYTES_THIS_ACK(tp, th); 2739 KASSERT(acked >= 0, ("%s: acked unexepectedly negative " 2740 "(tp->snd_una=%u, th->th_ack=%u, tp=%p, m=%p)", __func__, 2741 tp->snd_una, th->th_ack, tp, m)); 2742 TCPSTAT_ADD(tcps_rcvackpack, nsegs); 2743 TCPSTAT_ADD(tcps_rcvackbyte, acked); 2744 2745 /* 2746 * If we just performed our first retransmit, and the ACK 2747 * arrives within our recovery window, then it was a mistake 2748 * to do the retransmit in the first place. Recover our 2749 * original cwnd and ssthresh, and proceed to transmit where 2750 * we left off. 2751 */ 2752 if (tp->t_rxtshift == 1 && 2753 tp->t_flags & TF_PREVVALID && 2754 tp->t_badrxtwin && 2755 SEQ_LT(to.to_tsecr, tp->t_badrxtwin)) 2756 cc_cong_signal(tp, th, CC_RTO_ERR); 2757 2758 /* 2759 * If we have a timestamp reply, update smoothed 2760 * round trip time. If no timestamp is present but 2761 * transmit timer is running and timed sequence 2762 * number was acked, update smoothed round trip time. 2763 * Since we now have an rtt measurement, cancel the 2764 * timer backoff (cf., Phil Karn's retransmit alg.). 2765 * Recompute the initial retransmit timer. 2766 * 2767 * Some boxes send broken timestamp replies 2768 * during the SYN+ACK phase, ignore 2769 * timestamps of 0 or we could calculate a 2770 * huge RTT and blow up the retransmit timer. 2771 */ 2772 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) { 2773 uint32_t t; 2774 2775 t = tcp_ts_getticks() - to.to_tsecr; 2776 if (!tp->t_rttlow || tp->t_rttlow > t) 2777 tp->t_rttlow = t; 2778 tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1); 2779 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) { 2780 if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime) 2781 tp->t_rttlow = ticks - tp->t_rtttime; 2782 tcp_xmit_timer(tp, ticks - tp->t_rtttime); 2783 } 2784 2785 /* 2786 * If all outstanding data is acked, stop retransmit 2787 * timer and remember to restart (more output or persist). 2788 * If there is more data to be acked, restart retransmit 2789 * timer, using current (possibly backed-off) value. 2790 */ 2791 if (th->th_ack == tp->snd_max) { 2792 tcp_timer_activate(tp, TT_REXMT, 0); 2793 needoutput = 1; 2794 } else if (!tcp_timer_active(tp, TT_PERSIST)) 2795 tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur); 2796 2797 /* 2798 * If no data (only SYN) was ACK'd, 2799 * skip rest of ACK processing. 2800 */ 2801 if (acked == 0) 2802 goto step6; 2803 2804 /* 2805 * Let the congestion control algorithm update congestion 2806 * control related information. This typically means increasing 2807 * the congestion window. 2808 */ 2809 cc_ack_received(tp, th, nsegs, CC_ACK); 2810 2811 SOCKBUF_LOCK(&so->so_snd); 2812 if (acked > sbavail(&so->so_snd)) { 2813 if (tp->snd_wnd >= sbavail(&so->so_snd)) 2814 tp->snd_wnd -= sbavail(&so->so_snd); 2815 else 2816 tp->snd_wnd = 0; 2817 mfree = sbcut_locked(&so->so_snd, 2818 (int)sbavail(&so->so_snd)); 2819 ourfinisacked = 1; 2820 } else { 2821 mfree = sbcut_locked(&so->so_snd, acked); 2822 if (tp->snd_wnd >= (uint32_t) acked) 2823 tp->snd_wnd -= acked; 2824 else 2825 tp->snd_wnd = 0; 2826 ourfinisacked = 0; 2827 } 2828 /* NB: sowwakeup_locked() does an implicit unlock. */ 2829 sowwakeup_locked(so); 2830 m_freem(mfree); 2831 /* Detect una wraparound. */ 2832 if (!IN_RECOVERY(tp->t_flags) && 2833 SEQ_GT(tp->snd_una, tp->snd_recover) && 2834 SEQ_LEQ(th->th_ack, tp->snd_recover)) 2835 tp->snd_recover = th->th_ack - 1; 2836 /* XXXLAS: Can this be moved up into cc_post_recovery? */ 2837 if (IN_RECOVERY(tp->t_flags) && 2838 SEQ_GEQ(th->th_ack, tp->snd_recover)) { 2839 EXIT_RECOVERY(tp->t_flags); 2840 } 2841 tp->snd_una = th->th_ack; 2842 if (tp->t_flags & TF_SACK_PERMIT) { 2843 if (SEQ_GT(tp->snd_una, tp->snd_recover)) 2844 tp->snd_recover = tp->snd_una; 2845 } 2846 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 2847 tp->snd_nxt = tp->snd_una; 2848 2849 switch (tp->t_state) { 2850 2851 /* 2852 * In FIN_WAIT_1 STATE in addition to the processing 2853 * for the ESTABLISHED state if our FIN is now acknowledged 2854 * then enter FIN_WAIT_2. 2855 */ 2856 case TCPS_FIN_WAIT_1: 2857 if (ourfinisacked) { 2858 /* 2859 * If we can't receive any more 2860 * data, then closing user can proceed. 2861 * Starting the timer is contrary to the 2862 * specification, but if we don't get a FIN 2863 * we'll hang forever. 2864 * 2865 * XXXjl: 2866 * we should release the tp also, and use a 2867 * compressed state. 2868 */ 2869 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) { 2870 soisdisconnected(so); 2871 tcp_timer_activate(tp, TT_2MSL, 2872 (tcp_fast_finwait2_recycle ? 2873 tcp_finwait2_timeout : 2874 TP_MAXIDLE(tp))); 2875 } 2876 tcp_state_change(tp, TCPS_FIN_WAIT_2); 2877 } 2878 break; 2879 2880 /* 2881 * In CLOSING STATE in addition to the processing for 2882 * the ESTABLISHED state if the ACK acknowledges our FIN 2883 * then enter the TIME-WAIT state, otherwise ignore 2884 * the segment. 2885 */ 2886 case TCPS_CLOSING: 2887 if (ourfinisacked) { 2888 tcp_twstart(tp); 2889 m_freem(m); 2890 return; 2891 } 2892 break; 2893 2894 /* 2895 * In LAST_ACK, we may still be waiting for data to drain 2896 * and/or to be acked, as well as for the ack of our FIN. 2897 * If our FIN is now acknowledged, delete the TCB, 2898 * enter the closed state and return. 2899 */ 2900 case TCPS_LAST_ACK: 2901 if (ourfinisacked) { 2902 tp = tcp_close(tp); 2903 goto drop; 2904 } 2905 break; 2906 } 2907 } 2908 2909 step6: 2910 INP_WLOCK_ASSERT(tp->t_inpcb); 2911 2912 /* 2913 * Update window information. 2914 * Don't look at window if no ACK: TAC's send garbage on first SYN. 2915 */ 2916 if ((thflags & TH_ACK) && 2917 (SEQ_LT(tp->snd_wl1, th->th_seq) || 2918 (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) || 2919 (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) { 2920 /* keep track of pure window updates */ 2921 if (tlen == 0 && 2922 tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd) 2923 TCPSTAT_INC(tcps_rcvwinupd); 2924 tp->snd_wnd = tiwin; 2925 tp->snd_wl1 = th->th_seq; 2926 tp->snd_wl2 = th->th_ack; 2927 if (tp->snd_wnd > tp->max_sndwnd) 2928 tp->max_sndwnd = tp->snd_wnd; 2929 needoutput = 1; 2930 } 2931 2932 /* 2933 * Process segments with URG. 2934 */ 2935 if ((thflags & TH_URG) && th->th_urp && 2936 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 2937 /* 2938 * This is a kludge, but if we receive and accept 2939 * random urgent pointers, we'll crash in 2940 * soreceive. It's hard to imagine someone 2941 * actually wanting to send this much urgent data. 2942 */ 2943 SOCKBUF_LOCK(&so->so_rcv); 2944 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) { 2945 th->th_urp = 0; /* XXX */ 2946 thflags &= ~TH_URG; /* XXX */ 2947 SOCKBUF_UNLOCK(&so->so_rcv); /* XXX */ 2948 goto dodata; /* XXX */ 2949 } 2950 /* 2951 * If this segment advances the known urgent pointer, 2952 * then mark the data stream. This should not happen 2953 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 2954 * a FIN has been received from the remote side. 2955 * In these states we ignore the URG. 2956 * 2957 * According to RFC961 (Assigned Protocols), 2958 * the urgent pointer points to the last octet 2959 * of urgent data. We continue, however, 2960 * to consider it to indicate the first octet 2961 * of data past the urgent section as the original 2962 * spec states (in one of two places). 2963 */ 2964 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) { 2965 tp->rcv_up = th->th_seq + th->th_urp; 2966 so->so_oobmark = sbavail(&so->so_rcv) + 2967 (tp->rcv_up - tp->rcv_nxt) - 1; 2968 if (so->so_oobmark == 0) 2969 so->so_rcv.sb_state |= SBS_RCVATMARK; 2970 sohasoutofband(so); 2971 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 2972 } 2973 SOCKBUF_UNLOCK(&so->so_rcv); 2974 /* 2975 * Remove out of band data so doesn't get presented to user. 2976 * This can happen independent of advancing the URG pointer, 2977 * but if two URG's are pending at once, some out-of-band 2978 * data may creep in... ick. 2979 */ 2980 if (th->th_urp <= (uint32_t)tlen && 2981 !(so->so_options & SO_OOBINLINE)) { 2982 /* hdr drop is delayed */ 2983 tcp_pulloutofband(so, th, m, drop_hdrlen); 2984 } 2985 } else { 2986 /* 2987 * If no out of band data is expected, 2988 * pull receive urgent pointer along 2989 * with the receive window. 2990 */ 2991 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 2992 tp->rcv_up = tp->rcv_nxt; 2993 } 2994 dodata: /* XXX */ 2995 INP_WLOCK_ASSERT(tp->t_inpcb); 2996 2997 /* 2998 * Process the segment text, merging it into the TCP sequencing queue, 2999 * and arranging for acknowledgment of receipt if necessary. 3000 * This process logically involves adjusting tp->rcv_wnd as data 3001 * is presented to the user (this happens in tcp_usrreq.c, 3002 * case PRU_RCVD). If a FIN has already been received on this 3003 * connection then we just ignore the text. 3004 */ 3005 tfo_syn = ((tp->t_state == TCPS_SYN_RECEIVED) && 3006 IS_FASTOPEN(tp->t_flags)); 3007 if ((tlen || (thflags & TH_FIN) || (tfo_syn && tlen > 0)) && 3008 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3009 tcp_seq save_start = th->th_seq; 3010 tcp_seq save_rnxt = tp->rcv_nxt; 3011 int save_tlen = tlen; 3012 m_adj(m, drop_hdrlen); /* delayed header drop */ 3013 /* 3014 * Insert segment which includes th into TCP reassembly queue 3015 * with control block tp. Set thflags to whether reassembly now 3016 * includes a segment with FIN. This handles the common case 3017 * inline (segment is the next to be received on an established 3018 * connection, and the queue is empty), avoiding linkage into 3019 * and removal from the queue and repetition of various 3020 * conversions. 3021 * Set DELACK for segments received in order, but ack 3022 * immediately when segments are out of order (so 3023 * fast retransmit can work). 3024 */ 3025 if (th->th_seq == tp->rcv_nxt && 3026 SEGQ_EMPTY(tp) && 3027 (TCPS_HAVEESTABLISHED(tp->t_state) || 3028 tfo_syn)) { 3029 if (DELAY_ACK(tp, tlen) || tfo_syn) 3030 tp->t_flags |= TF_DELACK; 3031 else 3032 tp->t_flags |= TF_ACKNOW; 3033 tp->rcv_nxt += tlen; 3034 if (tlen && 3035 ((tp->t_flags2 & TF2_FBYTES_COMPLETE) == 0) && 3036 (tp->t_fbyte_in == 0)) { 3037 tp->t_fbyte_in = ticks; 3038 if (tp->t_fbyte_in == 0) 3039 tp->t_fbyte_in = 1; 3040 if (tp->t_fbyte_out && tp->t_fbyte_in) 3041 tp->t_flags2 |= TF2_FBYTES_COMPLETE; 3042 } 3043 thflags = th->th_flags & TH_FIN; 3044 TCPSTAT_INC(tcps_rcvpack); 3045 TCPSTAT_ADD(tcps_rcvbyte, tlen); 3046 SOCKBUF_LOCK(&so->so_rcv); 3047 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) 3048 m_freem(m); 3049 else 3050 sbappendstream_locked(&so->so_rcv, m, 0); 3051 /* NB: sorwakeup_locked() does an implicit unlock. */ 3052 sorwakeup_locked(so); 3053 } else { 3054 /* 3055 * XXX: Due to the header drop above "th" is 3056 * theoretically invalid by now. Fortunately 3057 * m_adj() doesn't actually frees any mbufs 3058 * when trimming from the head. 3059 */ 3060 tcp_seq temp = save_start; 3061 thflags = tcp_reass(tp, th, &temp, &tlen, m); 3062 tp->t_flags |= TF_ACKNOW; 3063 } 3064 if ((tp->t_flags & TF_SACK_PERMIT) && (save_tlen > 0)) { 3065 if ((tlen == 0) && (SEQ_LT(save_start, save_rnxt))) { 3066 /* 3067 * DSACK actually handled in the fastpath 3068 * above. 3069 */ 3070 tcp_update_sack_list(tp, save_start, 3071 save_start + save_tlen); 3072 } else if ((tlen > 0) && SEQ_GT(tp->rcv_nxt, save_rnxt)) { 3073 if ((tp->rcv_numsacks >= 1) && 3074 (tp->sackblks[0].end == save_start)) { 3075 /* 3076 * Partial overlap, recorded at todrop 3077 * above. 3078 */ 3079 tcp_update_sack_list(tp, 3080 tp->sackblks[0].start, 3081 tp->sackblks[0].end); 3082 } else { 3083 tcp_update_dsack_list(tp, save_start, 3084 save_start + save_tlen); 3085 } 3086 } else if (tlen >= save_tlen) { 3087 /* Update of sackblks. */ 3088 tcp_update_dsack_list(tp, save_start, 3089 save_start + save_tlen); 3090 } else if (tlen > 0) { 3091 tcp_update_dsack_list(tp, save_start, 3092 save_start + tlen); 3093 } 3094 } 3095 #if 0 3096 /* 3097 * Note the amount of data that peer has sent into 3098 * our window, in order to estimate the sender's 3099 * buffer size. 3100 * XXX: Unused. 3101 */ 3102 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt)) 3103 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 3104 else 3105 len = so->so_rcv.sb_hiwat; 3106 #endif 3107 } else { 3108 m_freem(m); 3109 thflags &= ~TH_FIN; 3110 } 3111 3112 /* 3113 * If FIN is received ACK the FIN and let the user know 3114 * that the connection is closing. 3115 */ 3116 if (thflags & TH_FIN) { 3117 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 3118 socantrcvmore(so); 3119 /* 3120 * If connection is half-synchronized 3121 * (ie NEEDSYN flag on) then delay ACK, 3122 * so it may be piggybacked when SYN is sent. 3123 * Otherwise, since we received a FIN then no 3124 * more input can be expected, send ACK now. 3125 */ 3126 if (tp->t_flags & TF_NEEDSYN) 3127 tp->t_flags |= TF_DELACK; 3128 else 3129 tp->t_flags |= TF_ACKNOW; 3130 tp->rcv_nxt++; 3131 } 3132 switch (tp->t_state) { 3133 3134 /* 3135 * In SYN_RECEIVED and ESTABLISHED STATES 3136 * enter the CLOSE_WAIT state. 3137 */ 3138 case TCPS_SYN_RECEIVED: 3139 tp->t_starttime = ticks; 3140 /* FALLTHROUGH */ 3141 case TCPS_ESTABLISHED: 3142 tcp_state_change(tp, TCPS_CLOSE_WAIT); 3143 break; 3144 3145 /* 3146 * If still in FIN_WAIT_1 STATE FIN has not been acked so 3147 * enter the CLOSING state. 3148 */ 3149 case TCPS_FIN_WAIT_1: 3150 tcp_state_change(tp, TCPS_CLOSING); 3151 break; 3152 3153 /* 3154 * In FIN_WAIT_2 state enter the TIME_WAIT state, 3155 * starting the time-wait timer, turning off the other 3156 * standard timers. 3157 */ 3158 case TCPS_FIN_WAIT_2: 3159 tcp_twstart(tp); 3160 return; 3161 } 3162 } 3163 #ifdef TCPDEBUG 3164 if (so->so_options & SO_DEBUG) 3165 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen, 3166 &tcp_savetcp, 0); 3167 #endif 3168 TCP_PROBE3(debug__input, tp, th, m); 3169 3170 /* 3171 * Return any desired output. 3172 */ 3173 if (needoutput || (tp->t_flags & TF_ACKNOW)) 3174 (void) tp->t_fb->tfb_tcp_output(tp); 3175 3176 check_delack: 3177 INP_WLOCK_ASSERT(tp->t_inpcb); 3178 3179 if (tp->t_flags & TF_DELACK) { 3180 tp->t_flags &= ~TF_DELACK; 3181 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime); 3182 } 3183 INP_WUNLOCK(tp->t_inpcb); 3184 return; 3185 3186 dropafterack: 3187 /* 3188 * Generate an ACK dropping incoming segment if it occupies 3189 * sequence space, where the ACK reflects our state. 3190 * 3191 * We can now skip the test for the RST flag since all 3192 * paths to this code happen after packets containing 3193 * RST have been dropped. 3194 * 3195 * In the SYN-RECEIVED state, don't send an ACK unless the 3196 * segment we received passes the SYN-RECEIVED ACK test. 3197 * If it fails send a RST. This breaks the loop in the 3198 * "LAND" DoS attack, and also prevents an ACK storm 3199 * between two listening ports that have been sent forged 3200 * SYN segments, each with the source address of the other. 3201 */ 3202 if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) && 3203 (SEQ_GT(tp->snd_una, th->th_ack) || 3204 SEQ_GT(th->th_ack, tp->snd_max)) ) { 3205 rstreason = BANDLIM_RST_OPENPORT; 3206 goto dropwithreset; 3207 } 3208 #ifdef TCPDEBUG 3209 if (so->so_options & SO_DEBUG) 3210 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3211 &tcp_savetcp, 0); 3212 #endif 3213 TCP_PROBE3(debug__input, tp, th, m); 3214 tp->t_flags |= TF_ACKNOW; 3215 (void) tp->t_fb->tfb_tcp_output(tp); 3216 INP_WUNLOCK(tp->t_inpcb); 3217 m_freem(m); 3218 return; 3219 3220 dropwithreset: 3221 if (tp != NULL) { 3222 tcp_dropwithreset(m, th, tp, tlen, rstreason); 3223 INP_WUNLOCK(tp->t_inpcb); 3224 } else 3225 tcp_dropwithreset(m, th, NULL, tlen, rstreason); 3226 return; 3227 3228 drop: 3229 /* 3230 * Drop space held by incoming segment and return. 3231 */ 3232 #ifdef TCPDEBUG 3233 if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 3234 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen, 3235 &tcp_savetcp, 0); 3236 #endif 3237 TCP_PROBE3(debug__input, tp, th, m); 3238 if (tp != NULL) 3239 INP_WUNLOCK(tp->t_inpcb); 3240 m_freem(m); 3241 } 3242 3243 /* 3244 * Issue RST and make ACK acceptable to originator of segment. 3245 * The mbuf must still include the original packet header. 3246 * tp may be NULL. 3247 */ 3248 void 3249 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp, 3250 int tlen, int rstreason) 3251 { 3252 #ifdef INET 3253 struct ip *ip; 3254 #endif 3255 #ifdef INET6 3256 struct ip6_hdr *ip6; 3257 #endif 3258 3259 if (tp != NULL) { 3260 INP_WLOCK_ASSERT(tp->t_inpcb); 3261 } 3262 3263 /* Don't bother if destination was broadcast/multicast. */ 3264 if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST)) 3265 goto drop; 3266 #ifdef INET6 3267 if (mtod(m, struct ip *)->ip_v == 6) { 3268 ip6 = mtod(m, struct ip6_hdr *); 3269 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) || 3270 IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) 3271 goto drop; 3272 /* IPv6 anycast check is done at tcp6_input() */ 3273 } 3274 #endif 3275 #if defined(INET) && defined(INET6) 3276 else 3277 #endif 3278 #ifdef INET 3279 { 3280 ip = mtod(m, struct ip *); 3281 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) || 3282 IN_MULTICAST(ntohl(ip->ip_src.s_addr)) || 3283 ip->ip_src.s_addr == htonl(INADDR_BROADCAST) || 3284 in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) 3285 goto drop; 3286 } 3287 #endif 3288 3289 /* Perform bandwidth limiting. */ 3290 if (badport_bandlim(rstreason) < 0) 3291 goto drop; 3292 3293 /* tcp_respond consumes the mbuf chain. */ 3294 if (th->th_flags & TH_ACK) { 3295 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0, 3296 th->th_ack, TH_RST); 3297 } else { 3298 if (th->th_flags & TH_SYN) 3299 tlen++; 3300 if (th->th_flags & TH_FIN) 3301 tlen++; 3302 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen, 3303 (tcp_seq)0, TH_RST|TH_ACK); 3304 } 3305 return; 3306 drop: 3307 m_freem(m); 3308 } 3309 3310 /* 3311 * Parse TCP options and place in tcpopt. 3312 */ 3313 void 3314 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags) 3315 { 3316 int opt, optlen; 3317 3318 to->to_flags = 0; 3319 for (; cnt > 0; cnt -= optlen, cp += optlen) { 3320 opt = cp[0]; 3321 if (opt == TCPOPT_EOL) 3322 break; 3323 if (opt == TCPOPT_NOP) 3324 optlen = 1; 3325 else { 3326 if (cnt < 2) 3327 break; 3328 optlen = cp[1]; 3329 if (optlen < 2 || optlen > cnt) 3330 break; 3331 } 3332 switch (opt) { 3333 case TCPOPT_MAXSEG: 3334 if (optlen != TCPOLEN_MAXSEG) 3335 continue; 3336 if (!(flags & TO_SYN)) 3337 continue; 3338 to->to_flags |= TOF_MSS; 3339 bcopy((char *)cp + 2, 3340 (char *)&to->to_mss, sizeof(to->to_mss)); 3341 to->to_mss = ntohs(to->to_mss); 3342 break; 3343 case TCPOPT_WINDOW: 3344 if (optlen != TCPOLEN_WINDOW) 3345 continue; 3346 if (!(flags & TO_SYN)) 3347 continue; 3348 to->to_flags |= TOF_SCALE; 3349 to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT); 3350 break; 3351 case TCPOPT_TIMESTAMP: 3352 if (optlen != TCPOLEN_TIMESTAMP) 3353 continue; 3354 to->to_flags |= TOF_TS; 3355 bcopy((char *)cp + 2, 3356 (char *)&to->to_tsval, sizeof(to->to_tsval)); 3357 to->to_tsval = ntohl(to->to_tsval); 3358 bcopy((char *)cp + 6, 3359 (char *)&to->to_tsecr, sizeof(to->to_tsecr)); 3360 to->to_tsecr = ntohl(to->to_tsecr); 3361 break; 3362 case TCPOPT_SIGNATURE: 3363 /* 3364 * In order to reply to a host which has set the 3365 * TCP_SIGNATURE option in its initial SYN, we have 3366 * to record the fact that the option was observed 3367 * here for the syncache code to perform the correct 3368 * response. 3369 */ 3370 if (optlen != TCPOLEN_SIGNATURE) 3371 continue; 3372 to->to_flags |= TOF_SIGNATURE; 3373 to->to_signature = cp + 2; 3374 break; 3375 case TCPOPT_SACK_PERMITTED: 3376 if (optlen != TCPOLEN_SACK_PERMITTED) 3377 continue; 3378 if (!(flags & TO_SYN)) 3379 continue; 3380 if (!V_tcp_do_sack) 3381 continue; 3382 to->to_flags |= TOF_SACKPERM; 3383 break; 3384 case TCPOPT_SACK: 3385 if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0) 3386 continue; 3387 if (flags & TO_SYN) 3388 continue; 3389 to->to_flags |= TOF_SACK; 3390 to->to_nsacks = (optlen - 2) / TCPOLEN_SACK; 3391 to->to_sacks = cp + 2; 3392 TCPSTAT_INC(tcps_sack_rcv_blocks); 3393 break; 3394 case TCPOPT_FAST_OPEN: 3395 /* 3396 * Cookie length validation is performed by the 3397 * server side cookie checking code or the client 3398 * side cookie cache update code. 3399 */ 3400 if (!(flags & TO_SYN)) 3401 continue; 3402 if (!V_tcp_fastopen_client_enable && 3403 !V_tcp_fastopen_server_enable) 3404 continue; 3405 to->to_flags |= TOF_FASTOPEN; 3406 to->to_tfo_len = optlen - 2; 3407 to->to_tfo_cookie = to->to_tfo_len ? cp + 2 : NULL; 3408 break; 3409 default: 3410 continue; 3411 } 3412 } 3413 } 3414 3415 /* 3416 * Pull out of band byte out of a segment so 3417 * it doesn't appear in the user's data queue. 3418 * It is still reflected in the segment length for 3419 * sequencing purposes. 3420 */ 3421 void 3422 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m, 3423 int off) 3424 { 3425 int cnt = off + th->th_urp - 1; 3426 3427 while (cnt >= 0) { 3428 if (m->m_len > cnt) { 3429 char *cp = mtod(m, caddr_t) + cnt; 3430 struct tcpcb *tp = sototcpcb(so); 3431 3432 INP_WLOCK_ASSERT(tp->t_inpcb); 3433 3434 tp->t_iobc = *cp; 3435 tp->t_oobflags |= TCPOOB_HAVEDATA; 3436 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 3437 m->m_len--; 3438 if (m->m_flags & M_PKTHDR) 3439 m->m_pkthdr.len--; 3440 return; 3441 } 3442 cnt -= m->m_len; 3443 m = m->m_next; 3444 if (m == NULL) 3445 break; 3446 } 3447 panic("tcp_pulloutofband"); 3448 } 3449 3450 /* 3451 * Collect new round-trip time estimate 3452 * and update averages and current timeout. 3453 */ 3454 void 3455 tcp_xmit_timer(struct tcpcb *tp, int rtt) 3456 { 3457 int delta; 3458 3459 INP_WLOCK_ASSERT(tp->t_inpcb); 3460 3461 TCPSTAT_INC(tcps_rttupdated); 3462 tp->t_rttupdated++; 3463 #ifdef STATS 3464 stats_voi_update_abs_u32(tp->t_stats, VOI_TCP_RTT, 3465 imax(0, rtt * 1000 / hz)); 3466 #endif 3467 if ((tp->t_srtt != 0) && (tp->t_rxtshift <= TCP_RTT_INVALIDATE)) { 3468 /* 3469 * srtt is stored as fixed point with 5 bits after the 3470 * binary point (i.e., scaled by 8). The following magic 3471 * is equivalent to the smoothing algorithm in rfc793 with 3472 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 3473 * point). Adjust rtt to origin 0. 3474 */ 3475 delta = ((rtt - 1) << TCP_DELTA_SHIFT) 3476 - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT)); 3477 3478 if ((tp->t_srtt += delta) <= 0) 3479 tp->t_srtt = 1; 3480 3481 /* 3482 * We accumulate a smoothed rtt variance (actually, a 3483 * smoothed mean difference), then set the retransmit 3484 * timer to smoothed rtt + 4 times the smoothed variance. 3485 * rttvar is stored as fixed point with 4 bits after the 3486 * binary point (scaled by 16). The following is 3487 * equivalent to rfc793 smoothing with an alpha of .75 3488 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 3489 * rfc793's wired-in beta. 3490 */ 3491 if (delta < 0) 3492 delta = -delta; 3493 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT); 3494 if ((tp->t_rttvar += delta) <= 0) 3495 tp->t_rttvar = 1; 3496 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar) 3497 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3498 } else { 3499 /* 3500 * No rtt measurement yet - use the unsmoothed rtt. 3501 * Set the variance to half the rtt (so our first 3502 * retransmit happens at 3*rtt). 3503 */ 3504 tp->t_srtt = rtt << TCP_RTT_SHIFT; 3505 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 3506 tp->t_rttbest = tp->t_srtt + tp->t_rttvar; 3507 } 3508 tp->t_rtttime = 0; 3509 tp->t_rxtshift = 0; 3510 3511 /* 3512 * the retransmit should happen at rtt + 4 * rttvar. 3513 * Because of the way we do the smoothing, srtt and rttvar 3514 * will each average +1/2 tick of bias. When we compute 3515 * the retransmit timer, we want 1/2 tick of rounding and 3516 * 1 extra tick because of +-1/2 tick uncertainty in the 3517 * firing of the timer. The bias will give us exactly the 3518 * 1.5 tick we need. But, because the bias is 3519 * statistical, we have to test that we don't drop below 3520 * the minimum feasible timer (which is 2 ticks). 3521 */ 3522 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 3523 max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX); 3524 3525 /* 3526 * We received an ack for a packet that wasn't retransmitted; 3527 * it is probably safe to discard any error indications we've 3528 * received recently. This isn't quite right, but close enough 3529 * for now (a route might have failed after we sent a segment, 3530 * and the return path might not be symmetrical). 3531 */ 3532 tp->t_softerror = 0; 3533 } 3534 3535 /* 3536 * Determine a reasonable value for maxseg size. 3537 * If the route is known, check route for mtu. 3538 * If none, use an mss that can be handled on the outgoing interface 3539 * without forcing IP to fragment. If no route is found, route has no mtu, 3540 * or the destination isn't local, use a default, hopefully conservative 3541 * size (usually 512 or the default IP max size, but no more than the mtu 3542 * of the interface), as we can't discover anything about intervening 3543 * gateways or networks. We also initialize the congestion/slow start 3544 * window to be a single segment if the destination isn't local. 3545 * While looking at the routing entry, we also initialize other path-dependent 3546 * parameters from pre-set or cached values in the routing entry. 3547 * 3548 * NOTE that resulting t_maxseg doesn't include space for TCP options or 3549 * IP options, e.g. IPSEC data, since length of this data may vary, and 3550 * thus it is calculated for every segment separately in tcp_output(). 3551 * 3552 * NOTE that this routine is only called when we process an incoming 3553 * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS 3554 * settings are handled in tcp_mssopt(). 3555 */ 3556 void 3557 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer, 3558 struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap) 3559 { 3560 int mss = 0; 3561 uint32_t maxmtu = 0; 3562 struct inpcb *inp = tp->t_inpcb; 3563 struct hc_metrics_lite metrics; 3564 #ifdef INET6 3565 int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0; 3566 size_t min_protoh = isipv6 ? 3567 sizeof (struct ip6_hdr) + sizeof (struct tcphdr) : 3568 sizeof (struct tcpiphdr); 3569 #else 3570 const size_t min_protoh = sizeof(struct tcpiphdr); 3571 #endif 3572 3573 INP_WLOCK_ASSERT(tp->t_inpcb); 3574 3575 if (mtuoffer != -1) { 3576 KASSERT(offer == -1, ("%s: conflict", __func__)); 3577 offer = mtuoffer - min_protoh; 3578 } 3579 3580 /* Initialize. */ 3581 #ifdef INET6 3582 if (isipv6) { 3583 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap); 3584 tp->t_maxseg = V_tcp_v6mssdflt; 3585 } 3586 #endif 3587 #if defined(INET) && defined(INET6) 3588 else 3589 #endif 3590 #ifdef INET 3591 { 3592 maxmtu = tcp_maxmtu(&inp->inp_inc, cap); 3593 tp->t_maxseg = V_tcp_mssdflt; 3594 } 3595 #endif 3596 3597 /* 3598 * No route to sender, stay with default mss and return. 3599 */ 3600 if (maxmtu == 0) { 3601 /* 3602 * In case we return early we need to initialize metrics 3603 * to a defined state as tcp_hc_get() would do for us 3604 * if there was no cache hit. 3605 */ 3606 if (metricptr != NULL) 3607 bzero(metricptr, sizeof(struct hc_metrics_lite)); 3608 return; 3609 } 3610 3611 /* What have we got? */ 3612 switch (offer) { 3613 case 0: 3614 /* 3615 * Offer == 0 means that there was no MSS on the SYN 3616 * segment, in this case we use tcp_mssdflt as 3617 * already assigned to t_maxseg above. 3618 */ 3619 offer = tp->t_maxseg; 3620 break; 3621 3622 case -1: 3623 /* 3624 * Offer == -1 means that we didn't receive SYN yet. 3625 */ 3626 /* FALLTHROUGH */ 3627 3628 default: 3629 /* 3630 * Prevent DoS attack with too small MSS. Round up 3631 * to at least minmss. 3632 */ 3633 offer = max(offer, V_tcp_minmss); 3634 } 3635 3636 /* 3637 * rmx information is now retrieved from tcp_hostcache. 3638 */ 3639 tcp_hc_get(&inp->inp_inc, &metrics); 3640 if (metricptr != NULL) 3641 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite)); 3642 3643 /* 3644 * If there's a discovered mtu in tcp hostcache, use it. 3645 * Else, use the link mtu. 3646 */ 3647 if (metrics.rmx_mtu) 3648 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh; 3649 else { 3650 #ifdef INET6 3651 if (isipv6) { 3652 mss = maxmtu - min_protoh; 3653 if (!V_path_mtu_discovery && 3654 !in6_localaddr(&inp->in6p_faddr)) 3655 mss = min(mss, V_tcp_v6mssdflt); 3656 } 3657 #endif 3658 #if defined(INET) && defined(INET6) 3659 else 3660 #endif 3661 #ifdef INET 3662 { 3663 mss = maxmtu - min_protoh; 3664 if (!V_path_mtu_discovery && 3665 !in_localaddr(inp->inp_faddr)) 3666 mss = min(mss, V_tcp_mssdflt); 3667 } 3668 #endif 3669 /* 3670 * XXX - The above conditional (mss = maxmtu - min_protoh) 3671 * probably violates the TCP spec. 3672 * The problem is that, since we don't know the 3673 * other end's MSS, we are supposed to use a conservative 3674 * default. But, if we do that, then MTU discovery will 3675 * never actually take place, because the conservative 3676 * default is much less than the MTUs typically seen 3677 * on the Internet today. For the moment, we'll sweep 3678 * this under the carpet. 3679 * 3680 * The conservative default might not actually be a problem 3681 * if the only case this occurs is when sending an initial 3682 * SYN with options and data to a host we've never talked 3683 * to before. Then, they will reply with an MSS value which 3684 * will get recorded and the new parameters should get 3685 * recomputed. For Further Study. 3686 */ 3687 } 3688 mss = min(mss, offer); 3689 3690 /* 3691 * Sanity check: make sure that maxseg will be large 3692 * enough to allow some data on segments even if the 3693 * all the option space is used (40bytes). Otherwise 3694 * funny things may happen in tcp_output. 3695 * 3696 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3697 */ 3698 mss = max(mss, 64); 3699 3700 tp->t_maxseg = mss; 3701 } 3702 3703 void 3704 tcp_mss(struct tcpcb *tp, int offer) 3705 { 3706 int mss; 3707 uint32_t bufsize; 3708 struct inpcb *inp; 3709 struct socket *so; 3710 struct hc_metrics_lite metrics; 3711 struct tcp_ifcap cap; 3712 3713 KASSERT(tp != NULL, ("%s: tp == NULL", __func__)); 3714 3715 bzero(&cap, sizeof(cap)); 3716 tcp_mss_update(tp, offer, -1, &metrics, &cap); 3717 3718 mss = tp->t_maxseg; 3719 inp = tp->t_inpcb; 3720 3721 /* 3722 * If there's a pipesize, change the socket buffer to that size, 3723 * don't change if sb_hiwat is different than default (then it 3724 * has been changed on purpose with setsockopt). 3725 * Make the socket buffers an integral number of mss units; 3726 * if the mss is larger than the socket buffer, decrease the mss. 3727 */ 3728 so = inp->inp_socket; 3729 SOCKBUF_LOCK(&so->so_snd); 3730 if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe) 3731 bufsize = metrics.rmx_sendpipe; 3732 else 3733 bufsize = so->so_snd.sb_hiwat; 3734 if (bufsize < mss) 3735 mss = bufsize; 3736 else { 3737 bufsize = roundup(bufsize, mss); 3738 if (bufsize > sb_max) 3739 bufsize = sb_max; 3740 if (bufsize > so->so_snd.sb_hiwat) 3741 (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL); 3742 } 3743 SOCKBUF_UNLOCK(&so->so_snd); 3744 /* 3745 * Sanity check: make sure that maxseg will be large 3746 * enough to allow some data on segments even if the 3747 * all the option space is used (40bytes). Otherwise 3748 * funny things may happen in tcp_output. 3749 * 3750 * XXXGL: shouldn't we reserve space for IP/IPv6 options? 3751 */ 3752 tp->t_maxseg = max(mss, 64); 3753 3754 SOCKBUF_LOCK(&so->so_rcv); 3755 if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe) 3756 bufsize = metrics.rmx_recvpipe; 3757 else 3758 bufsize = so->so_rcv.sb_hiwat; 3759 if (bufsize > mss) { 3760 bufsize = roundup(bufsize, mss); 3761 if (bufsize > sb_max) 3762 bufsize = sb_max; 3763 if (bufsize > so->so_rcv.sb_hiwat) 3764 (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL); 3765 } 3766 SOCKBUF_UNLOCK(&so->so_rcv); 3767 3768 /* Check the interface for TSO capabilities. */ 3769 if (cap.ifcap & CSUM_TSO) { 3770 tp->t_flags |= TF_TSO; 3771 tp->t_tsomax = cap.tsomax; 3772 tp->t_tsomaxsegcount = cap.tsomaxsegcount; 3773 tp->t_tsomaxsegsize = cap.tsomaxsegsize; 3774 } 3775 } 3776 3777 /* 3778 * Determine the MSS option to send on an outgoing SYN. 3779 */ 3780 int 3781 tcp_mssopt(struct in_conninfo *inc) 3782 { 3783 int mss = 0; 3784 uint32_t thcmtu = 0; 3785 uint32_t maxmtu = 0; 3786 size_t min_protoh; 3787 3788 KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer")); 3789 3790 #ifdef INET6 3791 if (inc->inc_flags & INC_ISIPV6) { 3792 mss = V_tcp_v6mssdflt; 3793 maxmtu = tcp_maxmtu6(inc, NULL); 3794 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr); 3795 } 3796 #endif 3797 #if defined(INET) && defined(INET6) 3798 else 3799 #endif 3800 #ifdef INET 3801 { 3802 mss = V_tcp_mssdflt; 3803 maxmtu = tcp_maxmtu(inc, NULL); 3804 min_protoh = sizeof(struct tcpiphdr); 3805 } 3806 #endif 3807 #if defined(INET6) || defined(INET) 3808 thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */ 3809 #endif 3810 3811 if (maxmtu && thcmtu) 3812 mss = min(maxmtu, thcmtu) - min_protoh; 3813 else if (maxmtu || thcmtu) 3814 mss = max(maxmtu, thcmtu) - min_protoh; 3815 3816 return (mss); 3817 } 3818 3819 3820 /* 3821 * On a partial ack arrives, force the retransmission of the 3822 * next unacknowledged segment. Do not clear tp->t_dupacks. 3823 * By setting snd_nxt to ti_ack, this forces retransmission timer to 3824 * be started again. 3825 */ 3826 void 3827 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th) 3828 { 3829 tcp_seq onxt = tp->snd_nxt; 3830 uint32_t ocwnd = tp->snd_cwnd; 3831 u_int maxseg = tcp_maxseg(tp); 3832 3833 INP_WLOCK_ASSERT(tp->t_inpcb); 3834 3835 tcp_timer_activate(tp, TT_REXMT, 0); 3836 tp->t_rtttime = 0; 3837 tp->snd_nxt = th->th_ack; 3838 /* 3839 * Set snd_cwnd to one segment beyond acknowledged offset. 3840 * (tp->snd_una has not yet been updated when this function is called.) 3841 */ 3842 tp->snd_cwnd = maxseg + BYTES_THIS_ACK(tp, th); 3843 tp->t_flags |= TF_ACKNOW; 3844 (void) tp->t_fb->tfb_tcp_output(tp); 3845 tp->snd_cwnd = ocwnd; 3846 if (SEQ_GT(onxt, tp->snd_nxt)) 3847 tp->snd_nxt = onxt; 3848 /* 3849 * Partial window deflation. Relies on fact that tp->snd_una 3850 * not updated yet. 3851 */ 3852 if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th)) 3853 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th); 3854 else 3855 tp->snd_cwnd = 0; 3856 tp->snd_cwnd += maxseg; 3857 } 3858 3859 int 3860 tcp_compute_pipe(struct tcpcb *tp) 3861 { 3862 return (tp->snd_max - tp->snd_una + 3863 tp->sackhint.sack_bytes_rexmit - 3864 tp->sackhint.sacked_bytes); 3865 } 3866 3867 uint32_t 3868 tcp_compute_initwnd(uint32_t maxseg) 3869 { 3870 /* 3871 * Calculate the Initial Window, also used as Restart Window 3872 * 3873 * RFC5681 Section 3.1 specifies the default conservative values. 3874 * RFC3390 specifies slightly more aggressive values. 3875 * RFC6928 increases it to ten segments. 3876 * Support for user specified value for initial flight size. 3877 */ 3878 if (V_tcp_initcwnd_segments) 3879 return min(V_tcp_initcwnd_segments * maxseg, 3880 max(2 * maxseg, V_tcp_initcwnd_segments * 1460)); 3881 else if (V_tcp_do_rfc3390) 3882 return min(4 * maxseg, max(2 * maxseg, 4380)); 3883 else { 3884 /* Per RFC5681 Section 3.1 */ 3885 if (maxseg > 2190) 3886 return (2 * maxseg); 3887 else if (maxseg > 1095) 3888 return (3 * maxseg); 3889 else 3890 return (4 * maxseg); 3891 } 3892 } 3893