sys/netinet/tcp_input.c

   1 /*-
   2  * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994, 1995
   3  *      The Regents of the University of California.  All rights reserved.
   4  * Copyright (c) 2007-2008,2010
   5  *      Swinburne University of Technology, Melbourne, Australia.
   6  * Copyright (c) 2009-2010 Lawrence Stewart <lstewart@freebsd.org>
   7  * Copyright (c) 2010 The FreeBSD Foundation
   8  * Copyright (c) 2010-2011 Juniper Networks, Inc.
   9  * All rights reserved.
  10  *
  11  * Portions of this software were developed at the Centre for Advanced Internet
  12  * Architectures, Swinburne University of Technology, by Lawrence Stewart,
  13  * James Healy and David Hayes, made possible in part by a grant from the Cisco
  14  * University Research Program Fund at Community Foundation Silicon Valley.
  15  *
  16  * Portions of this software were developed at the Centre for Advanced
  17  * Internet Architectures, Swinburne University of Technology, Melbourne,
  18  * Australia by David Hayes under sponsorship from the FreeBSD Foundation.
  19  *
  20  * Portions of this software were developed by Robert N. M. Watson under
  21  * contract to Juniper Networks, Inc.
  22  *
  23  * Redistribution and use in source and binary forms, with or without
  24  * modification, are permitted provided that the following conditions
  25  * are met:
  26  * 1. Redistributions of source code must retain the above copyright
  27  *    notice, this list of conditions and the following disclaimer.
  28  * 2. Redistributions in binary form must reproduce the above copyright
  29  *    notice, this list of conditions and the following disclaimer in the
  30  *    documentation and/or other materials provided with the distribution.
  31  * 4. Neither the name of the University nor the names of its contributors
  32  *    may be used to endorse or promote products derived from this software
  33  *    without specific prior written permission.
  34  *
  35  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
  36  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  37  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  38  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
  39  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
  40  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
  41  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
  42  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  43  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
  44  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
  45  * SUCH DAMAGE.
  46  *
  47  *      @(#)tcp_input.c 8.12 (Berkeley) 5/24/95
  48  */
  49
  50 #include <sys/cdefs.h>
  51 __FBSDID("$FreeBSD$");
  52
  53 #include "opt_ipfw.h"           /* for ipfw_fwd */
  54 #include "opt_inet.h"
  55 #include "opt_inet6.h"
  56 #include "opt_ipsec.h"
  57 #include "opt_tcpdebug.h"
  58
  59 #include <sys/param.h>
  60 #include <sys/kernel.h>
  61 #include <sys/hhook.h>
  62 #include <sys/malloc.h>
  63 #include <sys/mbuf.h>
  64 #include <sys/proc.h>           /* for proc0 declaration */
  65 #include <sys/protosw.h>
  66 #include <sys/sdt.h>
  67 #include <sys/signalvar.h>
  68 #include <sys/socket.h>
  69 #include <sys/socketvar.h>
  70 #include <sys/sysctl.h>
  71 #include <sys/syslog.h>
  72 #include <sys/systm.h>
  73
  74 #include <machine/cpu.h>        /* before tcp_seq.h, for tcp_random18() */
  75
  76 #include <vm/uma.h>
  77
  78 #include <net/if.h>
  79 #include <net/if_var.h>
  80 #include <net/route.h>
  81 #include <net/vnet.h>
  82
  83 #define TCPSTATES               /* for logging */
  84
  85 #include <netinet/cc.h>
  86 #include <netinet/in.h>
  87 #include <netinet/in_kdtrace.h>
  88 #include <netinet/in_pcb.h>
  89 #include <netinet/in_systm.h>
  90 #include <netinet/in_var.h>
  91 #include <netinet/ip.h>
  92 #include <netinet/ip_icmp.h>    /* required for icmp_var.h */
  93 #include <netinet/icmp_var.h>   /* for ICMP_BANDLIM */
  94 #include <netinet/ip_var.h>
  95 #include <netinet/ip_options.h>
  96 #include <netinet/ip6.h>
  97 #include <netinet/icmp6.h>
  98 #include <netinet6/in6_pcb.h>
  99 #include <netinet6/ip6_var.h>
 100 #include <netinet6/nd6.h>
 101 #include <netinet/tcp_fsm.h>
 102 #include <netinet/tcp_seq.h>
 103 #include <netinet/tcp_timer.h>
 104 #include <netinet/tcp_var.h>
 105 #include <netinet6/tcp6_var.h>
 106 #include <netinet/tcpip.h>
 107 #ifdef TCPPCAP
 108 #include <netinet/tcp_pcap.h>
 109 #endif
 110 #include <netinet/tcp_syncache.h>
 111 #ifdef TCPDEBUG
 112 #include <netinet/tcp_debug.h>
 113 #endif /* TCPDEBUG */
 114 #ifdef TCP_OFFLOAD
 115 #include <netinet/tcp_offload.h>
 116 #endif
 117
 118 #ifdef IPSEC
 119 #include <netipsec/ipsec.h>
 120 #include <netipsec/ipsec6.h>
 121 #endif /*IPSEC*/
 122
 123 #include <machine/in_cksum.h>
 124
 125 #include <security/mac/mac_framework.h>
 126
 127 const int tcprexmtthresh = 3;
 128
 129 int tcp_log_in_vain = 0;
 130 SYSCTL_INT(_net_inet_tcp, OID_AUTO, log_in_vain, CTLFLAG_RW,
 131     &tcp_log_in_vain, 0,
 132     "Log all incoming TCP segments to closed ports");
 133
 134 VNET_DEFINE(int, blackhole) = 0;
 135 #define V_blackhole             VNET(blackhole)
 136 SYSCTL_INT(_net_inet_tcp, OID_AUTO, blackhole, CTLFLAG_VNET | CTLFLAG_RW,
 137     &VNET_NAME(blackhole), 0,
 138     "Do not send RST on segments to closed ports");
 139
 140 VNET_DEFINE(int, tcp_delack_enabled) = 1;
 141 SYSCTL_INT(_net_inet_tcp, OID_AUTO, delayed_ack, CTLFLAG_VNET | CTLFLAG_RW,
 142     &VNET_NAME(tcp_delack_enabled), 0,
 143     "Delay ACK to try and piggyback it onto a data packet");
 144
 145 VNET_DEFINE(int, drop_synfin) = 0;
 146 #define V_drop_synfin           VNET(drop_synfin)
 147 SYSCTL_INT(_net_inet_tcp, OID_AUTO, drop_synfin, CTLFLAG_VNET | CTLFLAG_RW,
 148     &VNET_NAME(drop_synfin), 0,
 149     "Drop TCP packets with SYN+FIN set");
 150
 151 VNET_DEFINE(int, tcp_do_rfc6675_pipe) = 0;
 152 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc6675_pipe, CTLFLAG_VNET | CTLFLAG_RW,
 153     &VNET_NAME(tcp_do_rfc6675_pipe), 0,
 154     "Use calculated pipe/in-flight bytes per RFC 6675");
 155
 156 VNET_DEFINE(int, tcp_do_rfc3042) = 1;
 157 #define V_tcp_do_rfc3042        VNET(tcp_do_rfc3042)
 158 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3042, CTLFLAG_VNET | CTLFLAG_RW,
 159     &VNET_NAME(tcp_do_rfc3042), 0,
 160     "Enable RFC 3042 (Limited Transmit)");
 161
 162 VNET_DEFINE(int, tcp_do_rfc3390) = 1;
 163 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3390, CTLFLAG_VNET | CTLFLAG_RW,
 164     &VNET_NAME(tcp_do_rfc3390), 0,
 165     "Enable RFC 3390 (Increasing TCP's Initial Congestion Window)");
 166
 167 VNET_DEFINE(int, tcp_initcwnd_segments) = 10;
 168 SYSCTL_INT(_net_inet_tcp, OID_AUTO, initcwnd_segments,
 169     CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(tcp_initcwnd_segments), 0,
 170     "Slow-start flight size (initial congestion window) in number of segments");
 171
 172 VNET_DEFINE(int, tcp_do_rfc3465) = 1;
 173 SYSCTL_INT(_net_inet_tcp, OID_AUTO, rfc3465, CTLFLAG_VNET | CTLFLAG_RW,
 174     &VNET_NAME(tcp_do_rfc3465), 0,
 175     "Enable RFC 3465 (Appropriate Byte Counting)");
 176
 177 VNET_DEFINE(int, tcp_abc_l_var) = 2;
 178 SYSCTL_INT(_net_inet_tcp, OID_AUTO, abc_l_var, CTLFLAG_VNET | CTLFLAG_RW,
 179     &VNET_NAME(tcp_abc_l_var), 2,
 180     "Cap the max cwnd increment during slow-start to this number of segments");
 181
 182 static SYSCTL_NODE(_net_inet_tcp, OID_AUTO, ecn, CTLFLAG_RW, 0, "TCP ECN");
 183
 184 VNET_DEFINE(int, tcp_do_ecn) = 0;
 185 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, enable, CTLFLAG_VNET | CTLFLAG_RW,
 186     &VNET_NAME(tcp_do_ecn), 0,
 187     "TCP ECN support");
 188
 189 VNET_DEFINE(int, tcp_ecn_maxretries) = 1;
 190 SYSCTL_INT(_net_inet_tcp_ecn, OID_AUTO, maxretries, CTLFLAG_VNET | CTLFLAG_RW,
 191     &VNET_NAME(tcp_ecn_maxretries), 0,
 192     "Max retries before giving up on ECN");
 193
 194 VNET_DEFINE(int, tcp_insecure_syn) = 0;
 195 #define V_tcp_insecure_syn      VNET(tcp_insecure_syn)
 196 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_syn, CTLFLAG_VNET | CTLFLAG_RW,
 197     &VNET_NAME(tcp_insecure_syn), 0,
 198     "Follow RFC793 instead of RFC5961 criteria for accepting SYN packets");
 199
 200 VNET_DEFINE(int, tcp_insecure_rst) = 0;
 201 #define V_tcp_insecure_rst      VNET(tcp_insecure_rst)
 202 SYSCTL_INT(_net_inet_tcp, OID_AUTO, insecure_rst, CTLFLAG_VNET | CTLFLAG_RW,
 203     &VNET_NAME(tcp_insecure_rst), 0,
 204     "Follow RFC793 instead of RFC5961 criteria for accepting RST packets");
 205
 206 VNET_DEFINE(int, tcp_recvspace) = 1024*64;
 207 #define V_tcp_recvspace VNET(tcp_recvspace)
 208 SYSCTL_INT(_net_inet_tcp, TCPCTL_RECVSPACE, recvspace, CTLFLAG_VNET | CTLFLAG_RW,
 209     &VNET_NAME(tcp_recvspace), 0, "Initial receive socket buffer size");
 210
 211 VNET_DEFINE(int, tcp_do_autorcvbuf) = 1;
 212 #define V_tcp_do_autorcvbuf     VNET(tcp_do_autorcvbuf)
 213 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_auto, CTLFLAG_VNET | CTLFLAG_RW,
 214     &VNET_NAME(tcp_do_autorcvbuf), 0,
 215     "Enable automatic receive buffer sizing");
 216
 217 VNET_DEFINE(int, tcp_autorcvbuf_inc) = 16*1024;
 218 #define V_tcp_autorcvbuf_inc    VNET(tcp_autorcvbuf_inc)
 219 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_inc, CTLFLAG_VNET | CTLFLAG_RW,
 220     &VNET_NAME(tcp_autorcvbuf_inc), 0,
 221     "Incrementor step size of automatic receive buffer");
 222
 223 VNET_DEFINE(int, tcp_autorcvbuf_max) = 2*1024*1024;
 224 #define V_tcp_autorcvbuf_max    VNET(tcp_autorcvbuf_max)
 225 SYSCTL_INT(_net_inet_tcp, OID_AUTO, recvbuf_max, CTLFLAG_VNET | CTLFLAG_RW,
 226     &VNET_NAME(tcp_autorcvbuf_max), 0,
 227     "Max size of automatic receive buffer");
 228
 229 VNET_DEFINE(struct inpcbhead, tcb);
 230 #define tcb6    tcb  /* for KAME src sync over BSD*'s */
 231 VNET_DEFINE(struct inpcbinfo, tcbinfo);
 232
 233 static void      tcp_dooptions(struct tcpopt *, u_char *, int, int);
 234 static void      tcp_do_segment(struct mbuf *, struct tcphdr *,
 235                      struct socket *, struct tcpcb *, int, int, uint8_t,
 236                      int);
 237 static void      tcp_dropwithreset(struct mbuf *, struct tcphdr *,
 238                      struct tcpcb *, int, int);
 239 static void      tcp_pulloutofband(struct socket *,
 240                      struct tcphdr *, struct mbuf *, int);
 241 static void      tcp_xmit_timer(struct tcpcb *, int);
 242 static void      tcp_newreno_partial_ack(struct tcpcb *, struct tcphdr *);
 243 static void inline      cc_ack_received(struct tcpcb *tp, struct tcphdr *th,
 244                             uint16_t type);
 245 static void inline      cc_conn_init(struct tcpcb *tp);
 246 static void inline      cc_post_recovery(struct tcpcb *tp, struct tcphdr *th);
 247 static void inline      hhook_run_tcp_est_in(struct tcpcb *tp,
 248                             struct tcphdr *th, struct tcpopt *to);
 249
 250 /*
 251  * TCP statistics are stored in an "array" of counter(9)s.
 252  */
 253 VNET_PCPUSTAT_DEFINE(struct tcpstat, tcpstat);
 254 VNET_PCPUSTAT_SYSINIT(tcpstat);
 255 SYSCTL_VNET_PCPUSTAT(_net_inet_tcp, TCPCTL_STATS, stats, struct tcpstat,
 256     tcpstat, "TCP statistics (struct tcpstat, netinet/tcp_var.h)");
 257
 258 #ifdef VIMAGE
 259 VNET_PCPUSTAT_SYSUNINIT(tcpstat);
 260 #endif /* VIMAGE */
 261 /*
 262  * Kernel module interface for updating tcpstat.  The argument is an index
 263  * into tcpstat treated as an array.
 264  */
 265 void
 266 kmod_tcpstat_inc(int statnum)
 267 {
 268
 269         counter_u64_add(VNET(tcpstat)[statnum], 1);
 270 }
 271
 272 /*
 273  * Wrapper for the TCP established input helper hook.
 274  */
 275 static void inline
 276 hhook_run_tcp_est_in(struct tcpcb *tp, struct tcphdr *th, struct tcpopt *to)
 277 {
 278         struct tcp_hhook_data hhook_data;
 279
 280         if (V_tcp_hhh[HHOOK_TCP_EST_IN]->hhh_nhooks > 0) {
 281                 hhook_data.tp = tp;
 282                 hhook_data.th = th;
 283                 hhook_data.to = to;
 284
 285                 hhook_run_hooks(V_tcp_hhh[HHOOK_TCP_EST_IN], &hhook_data,
 286                     tp->osd);
 287         }
 288 }
 289
 290 /*
 291  * CC wrapper hook functions
 292  */
 293 static void inline
 294 cc_ack_received(struct tcpcb *tp, struct tcphdr *th, uint16_t type)
 295 {
 296         INP_WLOCK_ASSERT(tp->t_inpcb);
 297
 298         tp->ccv->bytes_this_ack = BYTES_THIS_ACK(tp, th);
 299         if (tp->snd_cwnd <= tp->snd_wnd)
 300                 tp->ccv->flags |= CCF_CWND_LIMITED;
 301         else
 302                 tp->ccv->flags &= ~CCF_CWND_LIMITED;
 303
 304         if (type == CC_ACK) {
 305                 if (tp->snd_cwnd > tp->snd_ssthresh) {
 306                         tp->t_bytes_acked += min(tp->ccv->bytes_this_ack,
 307                              V_tcp_abc_l_var * tp->t_maxseg);
 308                         if (tp->t_bytes_acked >= tp->snd_cwnd) {
 309                                 tp->t_bytes_acked -= tp->snd_cwnd;
 310                                 tp->ccv->flags |= CCF_ABC_SENTAWND;
 311                         }
 312                 } else {
 313                                 tp->ccv->flags &= ~CCF_ABC_SENTAWND;
 314                                 tp->t_bytes_acked = 0;
 315                 }
 316         }
 317
 318         if (CC_ALGO(tp)->ack_received != NULL) {
 319                 /* XXXLAS: Find a way to live without this */
 320                 tp->ccv->curack = th->th_ack;
 321                 CC_ALGO(tp)->ack_received(tp->ccv, type);
 322         }
 323 }
 324
 325 static void inline
 326 cc_conn_init(struct tcpcb *tp)
 327 {
 328         struct hc_metrics_lite metrics;
 329         struct inpcb *inp = tp->t_inpcb;
 330         int rtt;
 331
 332         INP_WLOCK_ASSERT(tp->t_inpcb);
 333
 334         tcp_hc_get(&inp->inp_inc, &metrics);
 335
 336         if (tp->t_srtt == 0 && (rtt = metrics.rmx_rtt)) {
 337                 tp->t_srtt = rtt;
 338                 tp->t_rttbest = tp->t_srtt + TCP_RTT_SCALE;
 339                 TCPSTAT_INC(tcps_usedrtt);
 340                 if (metrics.rmx_rttvar) {
 341                         tp->t_rttvar = metrics.rmx_rttvar;
 342                         TCPSTAT_INC(tcps_usedrttvar);
 343                 } else {
 344                         /* default variation is +- 1 rtt */
 345                         tp->t_rttvar =
 346                             tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE;
 347                 }
 348                 TCPT_RANGESET(tp->t_rxtcur,
 349                     ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1,
 350                     tp->t_rttmin, TCPTV_REXMTMAX);
 351         }
 352         if (metrics.rmx_ssthresh) {
 353                 /*
 354                  * There's some sort of gateway or interface
 355                  * buffer limit on the path.  Use this to set
 356                  * the slow start threshhold, but set the
 357                  * threshold to no less than 2*mss.
 358                  */
 359                 tp->snd_ssthresh = max(2 * tp->t_maxseg, metrics.rmx_ssthresh);
 360                 TCPSTAT_INC(tcps_usedssthresh);
 361         }
 362
 363         /*
 364          * Set the initial slow-start flight size.
 365          *
 366          * RFC5681 Section 3.1 specifies the default conservative values.
 367          * RFC3390 specifies slightly more aggressive values.
 368          * RFC6928 increases it to ten segments.
 369          * Support for user specified value for initial flight size.
 370          *
 371          * If a SYN or SYN/ACK was lost and retransmitted, we have to
 372          * reduce the initial CWND to one segment as congestion is likely
 373          * requiring us to be cautious.
 374          */
 375         if (tp->snd_cwnd == 1)
 376                 tp->snd_cwnd = tp->t_maxseg;            /* SYN(-ACK) lost */
 377         else if (V_tcp_initcwnd_segments)
 378                 tp->snd_cwnd = min(V_tcp_initcwnd_segments * tp->t_maxseg,
 379                     max(2 * tp->t_maxseg, V_tcp_initcwnd_segments * 1460));
 380         else if (V_tcp_do_rfc3390)
 381                 tp->snd_cwnd = min(4 * tp->t_maxseg,
 382                     max(2 * tp->t_maxseg, 4380));
 383         else {
 384                 /* Per RFC5681 Section 3.1 */
 385                 if (tp->t_maxseg > 2190)
 386                         tp->snd_cwnd = 2 * tp->t_maxseg;
 387                 else if (tp->t_maxseg > 1095)
 388                         tp->snd_cwnd = 3 * tp->t_maxseg;
 389                 else
 390                         tp->snd_cwnd = 4 * tp->t_maxseg;
 391         }
 392
 393         if (CC_ALGO(tp)->conn_init != NULL)
 394                 CC_ALGO(tp)->conn_init(tp->ccv);
 395 }
 396
 397 void inline
 398 cc_cong_signal(struct tcpcb *tp, struct tcphdr *th, uint32_t type)
 399 {
 400         INP_WLOCK_ASSERT(tp->t_inpcb);
 401
 402         switch(type) {
 403         case CC_NDUPACK:
 404                 if (!IN_FASTRECOVERY(tp->t_flags)) {
 405                         tp->snd_recover = tp->snd_max;
 406                         if (tp->t_flags & TF_ECN_PERMIT)
 407                                 tp->t_flags |= TF_ECN_SND_CWR;
 408                 }
 409                 break;
 410         case CC_ECN:
 411                 if (!IN_CONGRECOVERY(tp->t_flags)) {
 412                         TCPSTAT_INC(tcps_ecn_rcwnd);
 413                         tp->snd_recover = tp->snd_max;
 414                         if (tp->t_flags & TF_ECN_PERMIT)
 415                                 tp->t_flags |= TF_ECN_SND_CWR;
 416                 }
 417                 break;
 418         case CC_RTO:
 419                 tp->t_dupacks = 0;
 420                 tp->t_bytes_acked = 0;
 421                 EXIT_RECOVERY(tp->t_flags);
 422                 tp->snd_ssthresh = max(2, min(tp->snd_wnd, tp->snd_cwnd) / 2 /
 423                     tp->t_maxseg) * tp->t_maxseg;
 424                 tp->snd_cwnd = tp->t_maxseg;
 425                 break;
 426         case CC_RTO_ERR:
 427                 TCPSTAT_INC(tcps_sndrexmitbad);
 428                 /* RTO was unnecessary, so reset everything. */
 429                 tp->snd_cwnd = tp->snd_cwnd_prev;
 430                 tp->snd_ssthresh = tp->snd_ssthresh_prev;
 431                 tp->snd_recover = tp->snd_recover_prev;
 432                 if (tp->t_flags & TF_WASFRECOVERY)
 433                         ENTER_FASTRECOVERY(tp->t_flags);
 434                 if (tp->t_flags & TF_WASCRECOVERY)
 435                         ENTER_CONGRECOVERY(tp->t_flags);
 436                 tp->snd_nxt = tp->snd_max;
 437                 tp->t_flags &= ~TF_PREVVALID;
 438                 tp->t_badrxtwin = 0;
 439                 break;
 440         }
 441
 442         if (CC_ALGO(tp)->cong_signal != NULL) {
 443                 if (th != NULL)
 444                         tp->ccv->curack = th->th_ack;
 445                 CC_ALGO(tp)->cong_signal(tp->ccv, type);
 446         }
 447 }
 448
 449 static void inline
 450 cc_post_recovery(struct tcpcb *tp, struct tcphdr *th)
 451 {
 452         INP_WLOCK_ASSERT(tp->t_inpcb);
 453
 454         /* XXXLAS: KASSERT that we're in recovery? */
 455
 456         if (CC_ALGO(tp)->post_recovery != NULL) {
 457                 tp->ccv->curack = th->th_ack;
 458                 CC_ALGO(tp)->post_recovery(tp->ccv);
 459         }
 460         /* XXXLAS: EXIT_RECOVERY ? */
 461         tp->t_bytes_acked = 0;
 462 }
 463
 464 #ifdef TCP_SIGNATURE
 465 static inline int
 466 tcp_signature_verify_input(struct mbuf *m, int off0, int tlen, int optlen,
 467     struct tcpopt *to, struct tcphdr *th, u_int tcpbflag)
 468 {
 469         int ret;
 470
 471         tcp_fields_to_net(th);
 472         ret = tcp_signature_verify(m, off0, tlen, optlen, to, th, tcpbflag);
 473         tcp_fields_to_host(th);
 474         return (ret);
 475 }
 476 #endif
 477
 478 /*
 479  * Indicate whether this ack should be delayed.  We can delay the ack if
 480  * following conditions are met:
 481  *      - There is no delayed ack timer in progress.
 482  *      - Our last ack wasn't a 0-sized window. We never want to delay
 483  *        the ack that opens up a 0-sized window.
 484  *      - LRO wasn't used for this segment. We make sure by checking that the
 485  *        segment size is not larger than the MSS.
 486  *      - Delayed acks are enabled or this is a half-synchronized T/TCP
 487  *        connection.
 488  */
 489 #define DELAY_ACK(tp, tlen)                                             \
 490         ((!tcp_timer_active(tp, TT_DELACK) &&                           \
 491             (tp->t_flags & TF_RXWIN0SENT) == 0) &&                      \
 492             (tlen <= tp->t_maxopd) &&                                   \
 493             (V_tcp_delack_enabled || (tp->t_flags & TF_NEEDSYN)))
 494
 495 static void inline
 496 cc_ecnpkt_handler(struct tcpcb *tp, struct tcphdr *th, uint8_t iptos)
 497 {
 498         INP_WLOCK_ASSERT(tp->t_inpcb);
 499
 500         if (CC_ALGO(tp)->ecnpkt_handler != NULL) {
 501                 switch (iptos & IPTOS_ECN_MASK) {
 502                 case IPTOS_ECN_CE:
 503                     tp->ccv->flags |= CCF_IPHDR_CE;
 504                     break;
 505                 case IPTOS_ECN_ECT0:
 506                     tp->ccv->flags &= ~CCF_IPHDR_CE;
 507                     break;
 508                 case IPTOS_ECN_ECT1:
 509                     tp->ccv->flags &= ~CCF_IPHDR_CE;
 510                     break;
 511                 }
 512
 513                 if (th->th_flags & TH_CWR)
 514                         tp->ccv->flags |= CCF_TCPHDR_CWR;
 515                 else
 516                         tp->ccv->flags &= ~CCF_TCPHDR_CWR;
 517
 518                 if (tp->t_flags & TF_DELACK)
 519                         tp->ccv->flags |= CCF_DELACK;
 520                 else
 521                         tp->ccv->flags &= ~CCF_DELACK;
 522
 523                 CC_ALGO(tp)->ecnpkt_handler(tp->ccv);
 524
 525                 if (tp->ccv->flags & CCF_ACKNOW)
 526                         tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
 527         }
 528 }
 529
 530 /*
 531  * TCP input handling is split into multiple parts:
 532  *   tcp6_input is a thin wrapper around tcp_input for the extended
 533  *      ip6_protox[] call format in ip6_input
 534  *   tcp_input handles primary segment validation, inpcb lookup and
 535  *      SYN processing on listen sockets
 536  *   tcp_do_segment processes the ACK and text of the segment for
 537  *      establishing, established and closing connections
 538  */
 539 #ifdef INET6
 540 int
 541 tcp6_input(struct mbuf **mp, int *offp, int proto)
 542 {
 543         struct mbuf *m = *mp;
 544         struct in6_ifaddr *ia6;
 545         struct ip6_hdr *ip6;
 546
 547         IP6_EXTHDR_CHECK(m, *offp, sizeof(struct tcphdr), IPPROTO_DONE);
 548
 549         /*
 550          * draft-itojun-ipv6-tcp-to-anycast
 551          * better place to put this in?
 552          */
 553         ip6 = mtod(m, struct ip6_hdr *);
 554         ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
 555         if (ia6 && (ia6->ia6_flags & IN6_IFF_ANYCAST)) {
 556                 struct ip6_hdr *ip6;
 557
 558                 ifa_free(&ia6->ia_ifa);
 559                 ip6 = mtod(m, struct ip6_hdr *);
 560                 icmp6_error(m, ICMP6_DST_UNREACH, ICMP6_DST_UNREACH_ADDR,
 561                             (caddr_t)&ip6->ip6_dst - (caddr_t)ip6);
 562                 return (IPPROTO_DONE);
 563         }
 564         if (ia6)
 565                 ifa_free(&ia6->ia_ifa);
 566
 567         return (tcp_input(mp, offp, proto));
 568 }
 569 #endif /* INET6 */
 570
 571 int
 572 tcp_input(struct mbuf **mp, int *offp, int proto)
 573 {
 574         struct mbuf *m = *mp;
 575         struct tcphdr *th = NULL;
 576         struct ip *ip = NULL;
 577         struct inpcb *inp = NULL;
 578         struct tcpcb *tp = NULL;
 579         struct socket *so = NULL;
 580         u_char *optp = NULL;
 581         int off0;
 582         int optlen = 0;
 583 #ifdef INET
 584         int len;
 585 #endif
 586         int tlen = 0, off;
 587         int drop_hdrlen;
 588         int thflags;
 589         int rstreason = 0;      /* For badport_bandlim accounting purposes */
 590 #ifdef TCP_SIGNATURE
 591         uint8_t sig_checked = 0;
 592 #endif
 593         uint8_t iptos = 0;
 594         struct m_tag *fwd_tag = NULL;
 595 #ifdef INET6
 596         struct ip6_hdr *ip6 = NULL;
 597         int isipv6;
 598 #else
 599         const void *ip6 = NULL;
 600 #endif /* INET6 */
 601         struct tcpopt to;               /* options in this segment */
 602         char *s = NULL;                 /* address and port logging */
 603         int ti_locked;
 604 #define TI_UNLOCKED     1
 605 #define TI_RLOCKED      2
 606
 607 #ifdef TCPDEBUG
 608         /*
 609          * The size of tcp_saveipgen must be the size of the max ip header,
 610          * now IPv6.
 611          */
 612         u_char tcp_saveipgen[IP6_HDR_LEN];
 613         struct tcphdr tcp_savetcp;
 614         short ostate = 0;
 615 #endif
 616
 617 #ifdef INET6
 618         isipv6 = (mtod(m, struct ip *)->ip_v == 6) ? 1 : 0;
 619 #endif
 620
 621         off0 = *offp;
 622         m = *mp;
 623         *mp = NULL;
 624         to.to_flags = 0;
 625         TCPSTAT_INC(tcps_rcvtotal);
 626
 627 #ifdef INET6
 628         if (isipv6) {
 629                 /* IP6_EXTHDR_CHECK() is already done at tcp6_input(). */
 630
 631                 if (m->m_len < (sizeof(*ip6) + sizeof(*th))) {
 632                         m = m_pullup(m, sizeof(*ip6) + sizeof(*th));
 633                         if (m == NULL) {
 634                                 TCPSTAT_INC(tcps_rcvshort);
 635                                 return (IPPROTO_DONE);
 636                         }
 637                 }
 638
 639                 ip6 = mtod(m, struct ip6_hdr *);
 640                 th = (struct tcphdr *)((caddr_t)ip6 + off0);
 641                 tlen = sizeof(*ip6) + ntohs(ip6->ip6_plen) - off0;
 642                 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID_IPV6) {
 643                         if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
 644                                 th->th_sum = m->m_pkthdr.csum_data;
 645                         else
 646                                 th->th_sum = in6_cksum_pseudo(ip6, tlen,
 647                                     IPPROTO_TCP, m->m_pkthdr.csum_data);
 648                         th->th_sum ^= 0xffff;
 649                 } else
 650                         th->th_sum = in6_cksum(m, IPPROTO_TCP, off0, tlen);
 651                 if (th->th_sum) {
 652                         TCPSTAT_INC(tcps_rcvbadsum);
 653                         goto drop;
 654                 }
 655
 656                 /*
 657                  * Be proactive about unspecified IPv6 address in source.
 658                  * As we use all-zero to indicate unbounded/unconnected pcb,
 659                  * unspecified IPv6 address can be used to confuse us.
 660                  *
 661                  * Note that packets with unspecified IPv6 destination is
 662                  * already dropped in ip6_input.
 663                  */
 664                 if (IN6_IS_ADDR_UNSPECIFIED(&ip6->ip6_src)) {
 665                         /* XXX stat */
 666                         goto drop;
 667                 }
 668         }
 669 #endif
 670 #if defined(INET) && defined(INET6)
 671         else
 672 #endif
 673 #ifdef INET
 674         {
 675                 /*
 676                  * Get IP and TCP header together in first mbuf.
 677                  * Note: IP leaves IP header in first mbuf.
 678                  */
 679                 if (off0 > sizeof (struct ip)) {
 680                         ip_stripoptions(m);
 681                         off0 = sizeof(struct ip);
 682                 }
 683                 if (m->m_len < sizeof (struct tcpiphdr)) {
 684                         if ((m = m_pullup(m, sizeof (struct tcpiphdr)))
 685                             == NULL) {
 686                                 TCPSTAT_INC(tcps_rcvshort);
 687                                 return (IPPROTO_DONE);
 688                         }
 689                 }
 690                 ip = mtod(m, struct ip *);
 691                 th = (struct tcphdr *)((caddr_t)ip + off0);
 692                 tlen = ntohs(ip->ip_len) - off0;
 693
 694                 if (m->m_pkthdr.csum_flags & CSUM_DATA_VALID) {
 695                         if (m->m_pkthdr.csum_flags & CSUM_PSEUDO_HDR)
 696                                 th->th_sum = m->m_pkthdr.csum_data;
 697                         else
 698                                 th->th_sum = in_pseudo(ip->ip_src.s_addr,
 699                                     ip->ip_dst.s_addr,
 700                                     htonl(m->m_pkthdr.csum_data + tlen +
 701                                     IPPROTO_TCP));
 702                         th->th_sum ^= 0xffff;
 703                 } else {
 704                         struct ipovly *ipov = (struct ipovly *)ip;
 705
 706                         /*
 707                          * Checksum extended TCP header and data.
 708                          */
 709                         len = off0 + tlen;
 710                         bzero(ipov->ih_x1, sizeof(ipov->ih_x1));
 711                         ipov->ih_len = htons(tlen);
 712                         th->th_sum = in_cksum(m, len);
 713                         /* Reset length for SDT probes. */
 714                         ip->ip_len = htons(tlen + off0);
 715                 }
 716
 717                 if (th->th_sum) {
 718                         TCPSTAT_INC(tcps_rcvbadsum);
 719                         goto drop;
 720                 }
 721                 /* Re-initialization for later version check */
 722                 ip->ip_v = IPVERSION;
 723         }
 724 #endif /* INET */
 725
 726 #ifdef INET6
 727         if (isipv6)
 728                 iptos = (ntohl(ip6->ip6_flow) >> 20) & 0xff;
 729 #endif
 730 #if defined(INET) && defined(INET6)
 731         else
 732 #endif
 733 #ifdef INET
 734                 iptos = ip->ip_tos;
 735 #endif
 736
 737         /*
 738          * Check that TCP offset makes sense,
 739          * pull out TCP options and adjust length.              XXX
 740          */
 741         off = th->th_off << 2;
 742         if (off < sizeof (struct tcphdr) || off > tlen) {
 743                 TCPSTAT_INC(tcps_rcvbadoff);
 744                 goto drop;
 745         }
 746         tlen -= off;    /* tlen is used instead of ti->ti_len */
 747         if (off > sizeof (struct tcphdr)) {
 748 #ifdef INET6
 749                 if (isipv6) {
 750                         IP6_EXTHDR_CHECK(m, off0, off, IPPROTO_DONE);
 751                         ip6 = mtod(m, struct ip6_hdr *);
 752                         th = (struct tcphdr *)((caddr_t)ip6 + off0);
 753                 }
 754 #endif
 755 #if defined(INET) && defined(INET6)
 756                 else
 757 #endif
 758 #ifdef INET
 759                 {
 760                         if (m->m_len < sizeof(struct ip) + off) {
 761                                 if ((m = m_pullup(m, sizeof (struct ip) + off))
 762                                     == NULL) {
 763                                         TCPSTAT_INC(tcps_rcvshort);
 764                                         return (IPPROTO_DONE);
 765                                 }
 766                                 ip = mtod(m, struct ip *);
 767                                 th = (struct tcphdr *)((caddr_t)ip + off0);
 768                         }
 769                 }
 770 #endif
 771                 optlen = off - sizeof (struct tcphdr);
 772                 optp = (u_char *)(th + 1);
 773         }
 774         thflags = th->th_flags;
 775
 776         /*
 777          * Convert TCP protocol specific fields to host format.
 778          */
 779         tcp_fields_to_host(th);
 780
 781         /*
 782          * Delay dropping TCP, IP headers, IPv6 ext headers, and TCP options.
 783          */
 784         drop_hdrlen = off0 + off;
 785
 786         /*
 787          * Locate pcb for segment; if we're likely to add or remove a
 788          * connection then first acquire pcbinfo lock.  There are three cases
 789          * where we might discover later we need a write lock despite the
 790          * flags: ACKs moving a connection out of the syncache, ACKs for a
 791          * connection in TIMEWAIT and SYNs not targeting a listening socket.
 792          */
 793         if ((thflags & (TH_FIN | TH_RST)) != 0) {
 794                 INP_INFO_RLOCK(&V_tcbinfo);
 795                 ti_locked = TI_RLOCKED;
 796         } else
 797                 ti_locked = TI_UNLOCKED;
 798
 799         /*
 800          * Grab info from PACKET_TAG_IPFORWARD tag prepended to the chain.
 801          */
 802         if (
 803 #ifdef INET6
 804             (isipv6 && (m->m_flags & M_IP6_NEXTHOP))
 805 #ifdef INET
 806             || (!isipv6 && (m->m_flags & M_IP_NEXTHOP))
 807 #endif
 808 #endif
 809 #if defined(INET) && !defined(INET6)
 810             (m->m_flags & M_IP_NEXTHOP)
 811 #endif
 812             )
 813                 fwd_tag = m_tag_find(m, PACKET_TAG_IPFORWARD, NULL);
 814
 815 findpcb:
 816 #ifdef INVARIANTS
 817         if (ti_locked == TI_RLOCKED) {
 818                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 819         } else {
 820                 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
 821         }
 822 #endif
 823 #ifdef INET6
 824         if (isipv6 && fwd_tag != NULL) {
 825                 struct sockaddr_in6 *next_hop6;
 826
 827                 next_hop6 = (struct sockaddr_in6 *)(fwd_tag + 1);
 828                 /*
 829                  * Transparently forwarded. Pretend to be the destination.
 830                  * Already got one like this?
 831                  */
 832                 inp = in6_pcblookup_mbuf(&V_tcbinfo,
 833                     &ip6->ip6_src, th->th_sport, &ip6->ip6_dst, th->th_dport,
 834                     INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif, m);
 835                 if (!inp) {
 836                         /*
 837                          * It's new.  Try to find the ambushing socket.
 838                          * Because we've rewritten the destination address,
 839                          * any hardware-generated hash is ignored.
 840                          */
 841                         inp = in6_pcblookup(&V_tcbinfo, &ip6->ip6_src,
 842                             th->th_sport, &next_hop6->sin6_addr,
 843                             next_hop6->sin6_port ? ntohs(next_hop6->sin6_port) :
 844                             th->th_dport, INPLOOKUP_WILDCARD |
 845                             INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
 846                 }
 847         } else if (isipv6) {
 848                 inp = in6_pcblookup_mbuf(&V_tcbinfo, &ip6->ip6_src,
 849                     th->th_sport, &ip6->ip6_dst, th->th_dport,
 850                     INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
 851                     m->m_pkthdr.rcvif, m);
 852         }
 853 #endif /* INET6 */
 854 #if defined(INET6) && defined(INET)
 855         else
 856 #endif
 857 #ifdef INET
 858         if (fwd_tag != NULL) {
 859                 struct sockaddr_in *next_hop;
 860
 861                 next_hop = (struct sockaddr_in *)(fwd_tag+1);
 862                 /*
 863                  * Transparently forwarded. Pretend to be the destination.
 864                  * already got one like this?
 865                  */
 866                 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src, th->th_sport,
 867                     ip->ip_dst, th->th_dport, INPLOOKUP_WLOCKPCB,
 868                     m->m_pkthdr.rcvif, m);
 869                 if (!inp) {
 870                         /*
 871                          * It's new.  Try to find the ambushing socket.
 872                          * Because we've rewritten the destination address,
 873                          * any hardware-generated hash is ignored.
 874                          */
 875                         inp = in_pcblookup(&V_tcbinfo, ip->ip_src,
 876                             th->th_sport, next_hop->sin_addr,
 877                             next_hop->sin_port ? ntohs(next_hop->sin_port) :
 878                             th->th_dport, INPLOOKUP_WILDCARD |
 879                             INPLOOKUP_WLOCKPCB, m->m_pkthdr.rcvif);
 880                 }
 881         } else
 882                 inp = in_pcblookup_mbuf(&V_tcbinfo, ip->ip_src,
 883                     th->th_sport, ip->ip_dst, th->th_dport,
 884                     INPLOOKUP_WILDCARD | INPLOOKUP_WLOCKPCB,
 885                     m->m_pkthdr.rcvif, m);
 886 #endif /* INET */
 887
 888         /*
 889          * If the INPCB does not exist then all data in the incoming
 890          * segment is discarded and an appropriate RST is sent back.
 891          * XXX MRT Send RST using which routing table?
 892          */
 893         if (inp == NULL) {
 894                 /*
 895                  * Log communication attempts to ports that are not
 896                  * in use.
 897                  */
 898                 if ((tcp_log_in_vain == 1 && (thflags & TH_SYN)) ||
 899                     tcp_log_in_vain == 2) {
 900                         if ((s = tcp_log_vain(NULL, th, (void *)ip, ip6)))
 901                                 log(LOG_INFO, "%s; %s: Connection attempt "
 902                                     "to closed port\n", s, __func__);
 903                 }
 904                 /*
 905                  * When blackholing do not respond with a RST but
 906                  * completely ignore the segment and drop it.
 907                  */
 908                 if ((V_blackhole == 1 && (thflags & TH_SYN)) ||
 909                     V_blackhole == 2)
 910                         goto dropunlock;
 911
 912                 rstreason = BANDLIM_RST_CLOSEDPORT;
 913                 goto dropwithreset;
 914         }
 915         INP_WLOCK_ASSERT(inp);
 916         if ((inp->inp_flowtype == M_HASHTYPE_NONE) &&
 917             (M_HASHTYPE_GET(m) != M_HASHTYPE_NONE) &&
 918             ((inp->inp_socket == NULL) ||
 919             (inp->inp_socket->so_options & SO_ACCEPTCONN) == 0)) {
 920                 inp->inp_flowid = m->m_pkthdr.flowid;
 921                 inp->inp_flowtype = M_HASHTYPE_GET(m);
 922         }
 923 #ifdef IPSEC
 924 #ifdef INET6
 925         if (isipv6 && ipsec6_in_reject(m, inp)) {
 926                 goto dropunlock;
 927         } else
 928 #endif /* INET6 */
 929         if (ipsec4_in_reject(m, inp) != 0) {
 930                 goto dropunlock;
 931         }
 932 #endif /* IPSEC */
 933
 934         /*
 935          * Check the minimum TTL for socket.
 936          */
 937         if (inp->inp_ip_minttl != 0) {
 938 #ifdef INET6
 939                 if (isipv6 && inp->inp_ip_minttl > ip6->ip6_hlim)
 940                         goto dropunlock;
 941                 else
 942 #endif
 943                 if (inp->inp_ip_minttl > ip->ip_ttl)
 944                         goto dropunlock;
 945         }
 946
 947         /*
 948          * A previous connection in TIMEWAIT state is supposed to catch stray
 949          * or duplicate segments arriving late.  If this segment was a
 950          * legitimate new connection attempt, the old INPCB gets removed and
 951          * we can try again to find a listening socket.
 952          *
 953          * At this point, due to earlier optimism, we may hold only an inpcb
 954          * lock, and not the inpcbinfo write lock.  If so, we need to try to
 955          * acquire it, or if that fails, acquire a reference on the inpcb,
 956          * drop all locks, acquire a global write lock, and then re-acquire
 957          * the inpcb lock.  We may at that point discover that another thread
 958          * has tried to free the inpcb, in which case we need to loop back
 959          * and try to find a new inpcb to deliver to.
 960          *
 961          * XXXRW: It may be time to rethink timewait locking.
 962          */
 963 relocked:
 964         if (inp->inp_flags & INP_TIMEWAIT) {
 965                 if (ti_locked == TI_UNLOCKED) {
 966                         if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) {
 967                                 in_pcbref(inp);
 968                                 INP_WUNLOCK(inp);
 969                                 INP_INFO_RLOCK(&V_tcbinfo);
 970                                 ti_locked = TI_RLOCKED;
 971                                 INP_WLOCK(inp);
 972                                 if (in_pcbrele_wlocked(inp)) {
 973                                         inp = NULL;
 974                                         goto findpcb;
 975                                 }
 976                         } else
 977                                 ti_locked = TI_RLOCKED;
 978                 }
 979                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
 980
 981                 if (thflags & TH_SYN)
 982                         tcp_dooptions(&to, optp, optlen, TO_SYN);
 983                 /*
 984                  * NB: tcp_twcheck unlocks the INP and frees the mbuf.
 985                  */
 986                 if (tcp_twcheck(inp, &to, th, m, tlen))
 987                         goto findpcb;
 988                 INP_INFO_RUNLOCK(&V_tcbinfo);
 989                 return (IPPROTO_DONE);
 990         }
 991         /*
 992          * The TCPCB may no longer exist if the connection is winding
 993          * down or it is in the CLOSED state.  Either way we drop the
 994          * segment and send an appropriate response.
 995          */
 996         tp = intotcpcb(inp);
 997         if (tp == NULL || tp->t_state == TCPS_CLOSED) {
 998                 rstreason = BANDLIM_RST_CLOSEDPORT;
 999                 goto dropwithreset;
1000         }
1001
1002 #ifdef TCP_OFFLOAD
1003         if (tp->t_flags & TF_TOE) {
1004                 tcp_offload_input(tp, m);
1005                 m = NULL;       /* consumed by the TOE driver */
1006                 goto dropunlock;
1007         }
1008 #endif
1009
1010         /*
1011          * We've identified a valid inpcb, but it could be that we need an
1012          * inpcbinfo write lock but don't hold it.  In this case, attempt to
1013          * acquire using the same strategy as the TIMEWAIT case above.  If we
1014          * relock, we have to jump back to 'relocked' as the connection might
1015          * now be in TIMEWAIT.
1016          */
1017 #ifdef INVARIANTS
1018         if ((thflags & (TH_FIN | TH_RST)) != 0)
1019                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1020 #endif
1021         if (!((tp->t_state == TCPS_ESTABLISHED && (thflags & TH_SYN) == 0) ||
1022             (tp->t_state == TCPS_LISTEN && (thflags & TH_SYN)))) {
1023                 if (ti_locked == TI_UNLOCKED) {
1024                         if (INP_INFO_TRY_RLOCK(&V_tcbinfo) == 0) {
1025                                 in_pcbref(inp);
1026                                 INP_WUNLOCK(inp);
1027                                 INP_INFO_RLOCK(&V_tcbinfo);
1028                                 ti_locked = TI_RLOCKED;
1029                                 INP_WLOCK(inp);
1030                                 if (in_pcbrele_wlocked(inp)) {
1031                                         inp = NULL;
1032                                         goto findpcb;
1033                                 }
1034                                 goto relocked;
1035                         } else
1036                                 ti_locked = TI_RLOCKED;
1037                 }
1038                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1039         }
1040
1041 #ifdef MAC
1042         INP_WLOCK_ASSERT(inp);
1043         if (mac_inpcb_check_deliver(inp, m))
1044                 goto dropunlock;
1045 #endif
1046         so = inp->inp_socket;
1047         KASSERT(so != NULL, ("%s: so == NULL", __func__));
1048 #ifdef TCPDEBUG
1049         if (so->so_options & SO_DEBUG) {
1050                 ostate = tp->t_state;
1051 #ifdef INET6
1052                 if (isipv6) {
1053                         bcopy((char *)ip6, (char *)tcp_saveipgen, sizeof(*ip6));
1054                 } else
1055 #endif
1056                         bcopy((char *)ip, (char *)tcp_saveipgen, sizeof(*ip));
1057                 tcp_savetcp = *th;
1058         }
1059 #endif /* TCPDEBUG */
1060         /*
1061          * When the socket is accepting connections (the INPCB is in LISTEN
1062          * state) we look into the SYN cache if this is a new connection
1063          * attempt or the completion of a previous one.
1064          */
1065         if (so->so_options & SO_ACCEPTCONN) {
1066                 struct in_conninfo inc;
1067
1068                 KASSERT(tp->t_state == TCPS_LISTEN, ("%s: so accepting but "
1069                     "tp not listening", __func__));
1070                 bzero(&inc, sizeof(inc));
1071 #ifdef INET6
1072                 if (isipv6) {
1073                         inc.inc_flags |= INC_ISIPV6;
1074                         inc.inc6_faddr = ip6->ip6_src;
1075                         inc.inc6_laddr = ip6->ip6_dst;
1076                 } else
1077 #endif
1078                 {
1079                         inc.inc_faddr = ip->ip_src;
1080                         inc.inc_laddr = ip->ip_dst;
1081                 }
1082                 inc.inc_fport = th->th_sport;
1083                 inc.inc_lport = th->th_dport;
1084                 inc.inc_fibnum = so->so_fibnum;
1085
1086                 /*
1087                  * Check for an existing connection attempt in syncache if
1088                  * the flag is only ACK.  A successful lookup creates a new
1089                  * socket appended to the listen queue in SYN_RECEIVED state.
1090                  */
1091                 if ((thflags & (TH_RST|TH_ACK|TH_SYN)) == TH_ACK) {
1092
1093                         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1094                         /*
1095                          * Parse the TCP options here because
1096                          * syncookies need access to the reflected
1097                          * timestamp.
1098                          */
1099                         tcp_dooptions(&to, optp, optlen, 0);
1100                         /*
1101                          * NB: syncache_expand() doesn't unlock
1102                          * inp and tcpinfo locks.
1103                          */
1104                         if (!syncache_expand(&inc, &to, th, &so, m)) {
1105                                 /*
1106                                  * No syncache entry or ACK was not
1107                                  * for our SYN/ACK.  Send a RST.
1108                                  * NB: syncache did its own logging
1109                                  * of the failure cause.
1110                                  */
1111                                 rstreason = BANDLIM_RST_OPENPORT;
1112                                 goto dropwithreset;
1113                         }
1114                         if (so == NULL) {
1115                                 /*
1116                                  * We completed the 3-way handshake
1117                                  * but could not allocate a socket
1118                                  * either due to memory shortage,
1119                                  * listen queue length limits or
1120                                  * global socket limits.  Send RST
1121                                  * or wait and have the remote end
1122                                  * retransmit the ACK for another
1123                                  * try.
1124                                  */
1125                                 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1126                                         log(LOG_DEBUG, "%s; %s: Listen socket: "
1127                                             "Socket allocation failed due to "
1128                                             "limits or memory shortage, %s\n",
1129                                             s, __func__,
1130                                             V_tcp_sc_rst_sock_fail ?
1131                                             "sending RST" : "try again");
1132                                 if (V_tcp_sc_rst_sock_fail) {
1133                                         rstreason = BANDLIM_UNLIMITED;
1134                                         goto dropwithreset;
1135                                 } else
1136                                         goto dropunlock;
1137                         }
1138                         /*
1139                          * Socket is created in state SYN_RECEIVED.
1140                          * Unlock the listen socket, lock the newly
1141                          * created socket and update the tp variable.
1142                          */
1143                         INP_WUNLOCK(inp);       /* listen socket */
1144                         inp = sotoinpcb(so);
1145                         /*
1146                          * New connection inpcb is already locked by
1147                          * syncache_expand().
1148                          */
1149                         INP_WLOCK_ASSERT(inp);
1150                         tp = intotcpcb(inp);
1151                         KASSERT(tp->t_state == TCPS_SYN_RECEIVED,
1152                             ("%s: ", __func__));
1153 #ifdef TCP_SIGNATURE
1154                         if (sig_checked == 0)  {
1155                                 tcp_dooptions(&to, optp, optlen,
1156                                     (thflags & TH_SYN) ? TO_SYN : 0);
1157                                 if (!tcp_signature_verify_input(m, off0, tlen,
1158                                     optlen, &to, th, tp->t_flags)) {
1159
1160                                         /*
1161                                          * In SYN_SENT state if it receives an
1162                                          * RST, it is allowed for further
1163                                          * processing.
1164                                          */
1165                                         if ((thflags & TH_RST) == 0 ||
1166                                             (tp->t_state == TCPS_SYN_SENT) == 0)
1167                                                 goto dropunlock;
1168                                 }
1169                                 sig_checked = 1;
1170                         }
1171 #endif
1172
1173                         /*
1174                          * Process the segment and the data it
1175                          * contains.  tcp_do_segment() consumes
1176                          * the mbuf chain and unlocks the inpcb.
1177                          */
1178                         tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen,
1179                             iptos, ti_locked);
1180                         INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1181                         return (IPPROTO_DONE);
1182                 }
1183                 /*
1184                  * Segment flag validation for new connection attempts:
1185                  *
1186                  * Our (SYN|ACK) response was rejected.
1187                  * Check with syncache and remove entry to prevent
1188                  * retransmits.
1189                  *
1190                  * NB: syncache_chkrst does its own logging of failure
1191                  * causes.
1192                  */
1193                 if (thflags & TH_RST) {
1194                         syncache_chkrst(&inc, th);
1195                         goto dropunlock;
1196                 }
1197                 /*
1198                  * We can't do anything without SYN.
1199                  */
1200                 if ((thflags & TH_SYN) == 0) {
1201                         if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1202                                 log(LOG_DEBUG, "%s; %s: Listen socket: "
1203                                     "SYN is missing, segment ignored\n",
1204                                     s, __func__);
1205                         TCPSTAT_INC(tcps_badsyn);
1206                         goto dropunlock;
1207                 }
1208                 /*
1209                  * (SYN|ACK) is bogus on a listen socket.
1210                  */
1211                 if (thflags & TH_ACK) {
1212                         if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1213                                 log(LOG_DEBUG, "%s; %s: Listen socket: "
1214                                     "SYN|ACK invalid, segment rejected\n",
1215                                     s, __func__);
1216                         syncache_badack(&inc);  /* XXX: Not needed! */
1217                         TCPSTAT_INC(tcps_badsyn);
1218                         rstreason = BANDLIM_RST_OPENPORT;
1219                         goto dropwithreset;
1220                 }
1221                 /*
1222                  * If the drop_synfin option is enabled, drop all
1223                  * segments with both the SYN and FIN bits set.
1224                  * This prevents e.g. nmap from identifying the
1225                  * TCP/IP stack.
1226                  * XXX: Poor reasoning.  nmap has other methods
1227                  * and is constantly refining its stack detection
1228                  * strategies.
1229                  * XXX: This is a violation of the TCP specification
1230                  * and was used by RFC1644.
1231                  */
1232                 if ((thflags & TH_FIN) && V_drop_synfin) {
1233                         if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1234                                 log(LOG_DEBUG, "%s; %s: Listen socket: "
1235                                     "SYN|FIN segment ignored (based on "
1236                                     "sysctl setting)\n", s, __func__);
1237                         TCPSTAT_INC(tcps_badsyn);
1238                         goto dropunlock;
1239                 }
1240                 /*
1241                  * Segment's flags are (SYN) or (SYN|FIN).
1242                  *
1243                  * TH_PUSH, TH_URG, TH_ECE, TH_CWR are ignored
1244                  * as they do not affect the state of the TCP FSM.
1245                  * The data pointed to by TH_URG and th_urp is ignored.
1246                  */
1247                 KASSERT((thflags & (TH_RST|TH_ACK)) == 0,
1248                     ("%s: Listen socket: TH_RST or TH_ACK set", __func__));
1249                 KASSERT(thflags & (TH_SYN),
1250                     ("%s: Listen socket: TH_SYN not set", __func__));
1251 #ifdef INET6
1252                 /*
1253                  * If deprecated address is forbidden,
1254                  * we do not accept SYN to deprecated interface
1255                  * address to prevent any new inbound connection from
1256                  * getting established.
1257                  * When we do not accept SYN, we send a TCP RST,
1258                  * with deprecated source address (instead of dropping
1259                  * it).  We compromise it as it is much better for peer
1260                  * to send a RST, and RST will be the final packet
1261                  * for the exchange.
1262                  *
1263                  * If we do not forbid deprecated addresses, we accept
1264                  * the SYN packet.  RFC2462 does not suggest dropping
1265                  * SYN in this case.
1266                  * If we decipher RFC2462 5.5.4, it says like this:
1267                  * 1. use of deprecated addr with existing
1268                  *    communication is okay - "SHOULD continue to be
1269                  *    used"
1270                  * 2. use of it with new communication:
1271                  *   (2a) "SHOULD NOT be used if alternate address
1272                  *        with sufficient scope is available"
1273                  *   (2b) nothing mentioned otherwise.
1274                  * Here we fall into (2b) case as we have no choice in
1275                  * our source address selection - we must obey the peer.
1276                  *
1277                  * The wording in RFC2462 is confusing, and there are
1278                  * multiple description text for deprecated address
1279                  * handling - worse, they are not exactly the same.
1280                  * I believe 5.5.4 is the best one, so we follow 5.5.4.
1281                  */
1282                 if (isipv6 && !V_ip6_use_deprecated) {
1283                         struct in6_ifaddr *ia6;
1284
1285                         ia6 = in6ifa_ifwithaddr(&ip6->ip6_dst, 0 /* XXX */);
1286                         if (ia6 != NULL &&
1287                             (ia6->ia6_flags & IN6_IFF_DEPRECATED)) {
1288                                 ifa_free(&ia6->ia_ifa);
1289                                 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1290                                     log(LOG_DEBUG, "%s; %s: Listen socket: "
1291                                         "Connection attempt to deprecated "
1292                                         "IPv6 address rejected\n",
1293                                         s, __func__);
1294                                 rstreason = BANDLIM_RST_OPENPORT;
1295                                 goto dropwithreset;
1296                         }
1297                         if (ia6)
1298                                 ifa_free(&ia6->ia_ifa);
1299                 }
1300 #endif /* INET6 */
1301                 /*
1302                  * Basic sanity checks on incoming SYN requests:
1303                  *   Don't respond if the destination is a link layer
1304                  *      broadcast according to RFC1122 4.2.3.10, p. 104.
1305                  *   If it is from this socket it must be forged.
1306                  *   Don't respond if the source or destination is a
1307                  *      global or subnet broad- or multicast address.
1308                  *   Note that it is quite possible to receive unicast
1309                  *      link-layer packets with a broadcast IP address. Use
1310                  *      in_broadcast() to find them.
1311                  */
1312                 if (m->m_flags & (M_BCAST|M_MCAST)) {
1313                         if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1314                             log(LOG_DEBUG, "%s; %s: Listen socket: "
1315                                 "Connection attempt from broad- or multicast "
1316                                 "link layer address ignored\n", s, __func__);
1317                         goto dropunlock;
1318                 }
1319 #ifdef INET6
1320                 if (isipv6) {
1321                         if (th->th_dport == th->th_sport &&
1322                             IN6_ARE_ADDR_EQUAL(&ip6->ip6_dst, &ip6->ip6_src)) {
1323                                 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1324                                     log(LOG_DEBUG, "%s; %s: Listen socket: "
1325                                         "Connection attempt to/from self "
1326                                         "ignored\n", s, __func__);
1327                                 goto dropunlock;
1328                         }
1329                         if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
1330                             IN6_IS_ADDR_MULTICAST(&ip6->ip6_src)) {
1331                                 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1332                                     log(LOG_DEBUG, "%s; %s: Listen socket: "
1333                                         "Connection attempt from/to multicast "
1334                                         "address ignored\n", s, __func__);
1335                                 goto dropunlock;
1336                         }
1337                 }
1338 #endif
1339 #if defined(INET) && defined(INET6)
1340                 else
1341 #endif
1342 #ifdef INET
1343                 {
1344                         if (th->th_dport == th->th_sport &&
1345                             ip->ip_dst.s_addr == ip->ip_src.s_addr) {
1346                                 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1347                                     log(LOG_DEBUG, "%s; %s: Listen socket: "
1348                                         "Connection attempt from/to self "
1349                                         "ignored\n", s, __func__);
1350                                 goto dropunlock;
1351                         }
1352                         if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
1353                             IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
1354                             ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
1355                             in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif)) {
1356                                 if ((s = tcp_log_addrs(&inc, th, NULL, NULL)))
1357                                     log(LOG_DEBUG, "%s; %s: Listen socket: "
1358                                         "Connection attempt from/to broad- "
1359                                         "or multicast address ignored\n",
1360                                         s, __func__);
1361                                 goto dropunlock;
1362                         }
1363                 }
1364 #endif
1365                 /*
1366                  * SYN appears to be valid.  Create compressed TCP state
1367                  * for syncache.
1368                  */
1369 #ifdef TCPDEBUG
1370                 if (so->so_options & SO_DEBUG)
1371                         tcp_trace(TA_INPUT, ostate, tp,
1372                             (void *)tcp_saveipgen, &tcp_savetcp, 0);
1373 #endif
1374                 TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
1375                 tcp_dooptions(&to, optp, optlen, TO_SYN);
1376                 syncache_add(&inc, &to, th, inp, &so, m, NULL, NULL);
1377                 /*
1378                  * Entry added to syncache and mbuf consumed.
1379                  * Only the listen socket is unlocked by syncache_add().
1380                  */
1381                 if (ti_locked == TI_RLOCKED) {
1382                         INP_INFO_RUNLOCK(&V_tcbinfo);
1383                         ti_locked = TI_UNLOCKED;
1384                 }
1385                 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1386                 return (IPPROTO_DONE);
1387         } else if (tp->t_state == TCPS_LISTEN) {
1388                 /*
1389                  * When a listen socket is torn down the SO_ACCEPTCONN
1390                  * flag is removed first while connections are drained
1391                  * from the accept queue in a unlock/lock cycle of the
1392                  * ACCEPT_LOCK, opening a race condition allowing a SYN
1393                  * attempt go through unhandled.
1394                  */
1395                 goto dropunlock;
1396         }
1397
1398 #ifdef TCP_SIGNATURE
1399         if (sig_checked == 0)  {
1400                 tcp_dooptions(&to, optp, optlen,
1401                     (thflags & TH_SYN) ? TO_SYN : 0);
1402                 if (!tcp_signature_verify_input(m, off0, tlen, optlen, &to,
1403                     th, tp->t_flags)) {
1404
1405                         /*
1406                          * In SYN_SENT state if it receives an RST, it is
1407                          * allowed for further processing.
1408                          */
1409                         if ((thflags & TH_RST) == 0 ||
1410                             (tp->t_state == TCPS_SYN_SENT) == 0)
1411                                 goto dropunlock;
1412                 }
1413                 sig_checked = 1;
1414         }
1415 #endif
1416
1417         TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1418
1419         /*
1420          * Segment belongs to a connection in SYN_SENT, ESTABLISHED or later
1421          * state.  tcp_do_segment() always consumes the mbuf chain, unlocks
1422          * the inpcb, and unlocks pcbinfo.
1423          */
1424         tcp_do_segment(m, th, so, tp, drop_hdrlen, tlen, iptos, ti_locked);
1425         INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1426         return (IPPROTO_DONE);
1427
1428 dropwithreset:
1429         TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1430
1431         if (ti_locked == TI_RLOCKED) {
1432                 INP_INFO_RUNLOCK(&V_tcbinfo);
1433                 ti_locked = TI_UNLOCKED;
1434         }
1435 #ifdef INVARIANTS
1436         else {
1437                 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropwithreset "
1438                     "ti_locked: %d", __func__, ti_locked));
1439                 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1440         }
1441 #endif
1442
1443         if (inp != NULL) {
1444                 tcp_dropwithreset(m, th, tp, tlen, rstreason);
1445                 INP_WUNLOCK(inp);
1446         } else
1447                 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
1448         m = NULL;       /* mbuf chain got consumed. */
1449         goto drop;
1450
1451 dropunlock:
1452         if (m != NULL)
1453                 TCP_PROBE5(receive, NULL, tp, mtod(m, const char *), tp, th);
1454
1455         if (ti_locked == TI_RLOCKED) {
1456                 INP_INFO_RUNLOCK(&V_tcbinfo);
1457                 ti_locked = TI_UNLOCKED;
1458         }
1459 #ifdef INVARIANTS
1460         else {
1461                 KASSERT(ti_locked == TI_UNLOCKED, ("%s: dropunlock "
1462                     "ti_locked: %d", __func__, ti_locked));
1463                 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1464         }
1465 #endif
1466
1467         if (inp != NULL)
1468                 INP_WUNLOCK(inp);
1469
1470 drop:
1471         INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1472         if (s != NULL)
1473                 free(s, M_TCPLOG);
1474         if (m != NULL)
1475                 m_freem(m);
1476         return (IPPROTO_DONE);
1477 }
1478
1479 static void
1480 tcp_do_segment(struct mbuf *m, struct tcphdr *th, struct socket *so,
1481     struct tcpcb *tp, int drop_hdrlen, int tlen, uint8_t iptos,
1482     int ti_locked)
1483 {
1484         int thflags, acked, ourfinisacked, needoutput = 0;
1485         int rstreason, todrop, win;
1486         u_long tiwin;
1487         char *s;
1488         struct in_conninfo *inc;
1489         struct mbuf *mfree;
1490         struct tcpopt to;
1491
1492 #ifdef TCPDEBUG
1493         /*
1494          * The size of tcp_saveipgen must be the size of the max ip header,
1495          * now IPv6.
1496          */
1497         u_char tcp_saveipgen[IP6_HDR_LEN];
1498         struct tcphdr tcp_savetcp;
1499         short ostate = 0;
1500 #endif
1501         thflags = th->th_flags;
1502         inc = &tp->t_inpcb->inp_inc;
1503         tp->sackhint.last_sack_ack = 0;
1504
1505         /*
1506          * If this is either a state-changing packet or current state isn't
1507          * established, we require a write lock on tcbinfo.  Otherwise, we
1508          * allow the tcbinfo to be in either alocked or unlocked, as the
1509          * caller may have unnecessarily acquired a write lock due to a race.
1510          */
1511         if ((thflags & (TH_SYN | TH_FIN | TH_RST)) != 0 ||
1512             tp->t_state != TCPS_ESTABLISHED) {
1513                 KASSERT(ti_locked == TI_RLOCKED, ("%s ti_locked %d for "
1514                     "SYN/FIN/RST/!EST", __func__, ti_locked));
1515                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1516         } else {
1517 #ifdef INVARIANTS
1518                 if (ti_locked == TI_RLOCKED)
1519                         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
1520                 else {
1521                         KASSERT(ti_locked == TI_UNLOCKED, ("%s: EST "
1522                             "ti_locked: %d", __func__, ti_locked));
1523                         INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
1524                 }
1525 #endif
1526         }
1527         INP_WLOCK_ASSERT(tp->t_inpcb);
1528         KASSERT(tp->t_state > TCPS_LISTEN, ("%s: TCPS_LISTEN",
1529             __func__));
1530         KASSERT(tp->t_state != TCPS_TIME_WAIT, ("%s: TCPS_TIME_WAIT",
1531             __func__));
1532
1533 #ifdef TCPPCAP
1534         /* Save segment, if requested. */
1535         tcp_pcap_add(th, m, &(tp->t_inpkts));
1536 #endif
1537
1538         /*
1539          * Segment received on connection.
1540          * Reset idle time and keep-alive timer.
1541          * XXX: This should be done after segment
1542          * validation to ignore broken/spoofed segs.
1543          */
1544         tp->t_rcvtime = ticks;
1545         if (TCPS_HAVEESTABLISHED(tp->t_state))
1546                 tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
1547
1548         /*
1549          * Scale up the window into a 32-bit value.
1550          * For the SYN_SENT state the scale is zero.
1551          */
1552         tiwin = th->th_win << tp->snd_scale;
1553
1554         /*
1555          * TCP ECN processing.
1556          */
1557         if (tp->t_flags & TF_ECN_PERMIT) {
1558                 if (thflags & TH_CWR)
1559                         tp->t_flags &= ~TF_ECN_SND_ECE;
1560                 switch (iptos & IPTOS_ECN_MASK) {
1561                 case IPTOS_ECN_CE:
1562                         tp->t_flags |= TF_ECN_SND_ECE;
1563                         TCPSTAT_INC(tcps_ecn_ce);
1564                         break;
1565                 case IPTOS_ECN_ECT0:
1566                         TCPSTAT_INC(tcps_ecn_ect0);
1567                         break;
1568                 case IPTOS_ECN_ECT1:
1569                         TCPSTAT_INC(tcps_ecn_ect1);
1570                         break;
1571                 }
1572
1573                 /* Process a packet differently from RFC3168. */
1574                 cc_ecnpkt_handler(tp, th, iptos);
1575
1576                 /* Congestion experienced. */
1577                 if (thflags & TH_ECE) {
1578                         cc_cong_signal(tp, th, CC_ECN);
1579                 }
1580         }
1581
1582         /*
1583          * Parse options on any incoming segment.
1584          */
1585         tcp_dooptions(&to, (u_char *)(th + 1),
1586             (th->th_off << 2) - sizeof(struct tcphdr),
1587             (thflags & TH_SYN) ? TO_SYN : 0);
1588
1589         /*
1590          * If echoed timestamp is later than the current time,
1591          * fall back to non RFC1323 RTT calculation.  Normalize
1592          * timestamp if syncookies were used when this connection
1593          * was established.
1594          */
1595         if ((to.to_flags & TOF_TS) && (to.to_tsecr != 0)) {
1596                 to.to_tsecr -= tp->ts_offset;
1597                 if (TSTMP_GT(to.to_tsecr, tcp_ts_getticks()))
1598                         to.to_tsecr = 0;
1599         }
1600         /*
1601          * If timestamps were negotiated during SYN/ACK they should
1602          * appear on every segment during this session and vice versa.
1603          */
1604         if ((tp->t_flags & TF_RCVD_TSTMP) && !(to.to_flags & TOF_TS)) {
1605                 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1606                         log(LOG_DEBUG, "%s; %s: Timestamp missing, "
1607                             "no action\n", s, __func__);
1608                         free(s, M_TCPLOG);
1609                 }
1610         }
1611         if (!(tp->t_flags & TF_RCVD_TSTMP) && (to.to_flags & TOF_TS)) {
1612                 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
1613                         log(LOG_DEBUG, "%s; %s: Timestamp not expected, "
1614                             "no action\n", s, __func__);
1615                         free(s, M_TCPLOG);
1616                 }
1617         }
1618
1619         /*
1620          * Process options only when we get SYN/ACK back. The SYN case
1621          * for incoming connections is handled in tcp_syncache.
1622          * According to RFC1323 the window field in a SYN (i.e., a <SYN>
1623          * or <SYN,ACK>) segment itself is never scaled.
1624          * XXX this is traditional behavior, may need to be cleaned up.
1625          */
1626         if (tp->t_state == TCPS_SYN_SENT && (thflags & TH_SYN)) {
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                 }
1632                 /*
1633                  * Initial send window.  It will be updated with
1634                  * the next incoming segment to the scaled value.
1635                  */
1636                 tp->snd_wnd = th->th_win;
1637                 if (to.to_flags & TOF_TS) {
1638                         tp->t_flags |= TF_RCVD_TSTMP;
1639                         tp->ts_recent = to.to_tsval;
1640                         tp->ts_recent_age = tcp_ts_getticks();
1641                 }
1642                 if (to.to_flags & TOF_MSS)
1643                         tcp_mss(tp, to.to_mss);
1644                 if ((tp->t_flags & TF_SACK_PERMIT) &&
1645                     (to.to_flags & TOF_SACKPERM) == 0)
1646                         tp->t_flags &= ~TF_SACK_PERMIT;
1647         }
1648
1649         /*
1650          * Header prediction: check for the two common cases
1651          * of a uni-directional data xfer.  If the packet has
1652          * no control flags, is in-sequence, the window didn't
1653          * change and we're not retransmitting, it's a
1654          * candidate.  If the length is zero and the ack moved
1655          * forward, we're the sender side of the xfer.  Just
1656          * free the data acked & wake any higher level process
1657          * that was blocked waiting for space.  If the length
1658          * is non-zero and the ack didn't move, we're the
1659          * receiver side.  If we're getting packets in-order
1660          * (the reassembly queue is empty), add the data to
1661          * the socket buffer and note that we need a delayed ack.
1662          * Make sure that the hidden state-flags are also off.
1663          * Since we check for TCPS_ESTABLISHED first, it can only
1664          * be TH_NEEDSYN.
1665          */
1666         if (tp->t_state == TCPS_ESTABLISHED &&
1667             th->th_seq == tp->rcv_nxt &&
1668             (thflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK &&
1669             tp->snd_nxt == tp->snd_max &&
1670             tiwin && tiwin == tp->snd_wnd &&
1671             ((tp->t_flags & (TF_NEEDSYN|TF_NEEDFIN)) == 0) &&
1672             LIST_EMPTY(&tp->t_segq) &&
1673             ((to.to_flags & TOF_TS) == 0 ||
1674              TSTMP_GEQ(to.to_tsval, tp->ts_recent)) ) {
1675
1676                 /*
1677                  * If last ACK falls within this segment's sequence numbers,
1678                  * record the timestamp.
1679                  * NOTE that the test is modified according to the latest
1680                  * proposal of the tcplw@cray.com list (Braden 1993/04/26).
1681                  */
1682                 if ((to.to_flags & TOF_TS) != 0 &&
1683                     SEQ_LEQ(th->th_seq, tp->last_ack_sent)) {
1684                         tp->ts_recent_age = tcp_ts_getticks();
1685                         tp->ts_recent = to.to_tsval;
1686                 }
1687
1688                 if (tlen == 0) {
1689                         if (SEQ_GT(th->th_ack, tp->snd_una) &&
1690                             SEQ_LEQ(th->th_ack, tp->snd_max) &&
1691                             !IN_RECOVERY(tp->t_flags) &&
1692                             (to.to_flags & TOF_SACK) == 0 &&
1693                             TAILQ_EMPTY(&tp->snd_holes)) {
1694                                 /*
1695                                  * This is a pure ack for outstanding data.
1696                                  */
1697                                 if (ti_locked == TI_RLOCKED)
1698                                         INP_INFO_RUNLOCK(&V_tcbinfo);
1699                                 ti_locked = TI_UNLOCKED;
1700
1701                                 TCPSTAT_INC(tcps_predack);
1702
1703                                 /*
1704                                  * "bad retransmit" recovery.
1705                                  */
1706                                 if (tp->t_rxtshift == 1 &&
1707                                     tp->t_flags & TF_PREVVALID &&
1708                                     (int)(ticks - tp->t_badrxtwin) < 0) {
1709                                         cc_cong_signal(tp, th, CC_RTO_ERR);
1710                                 }
1711
1712                                 /*
1713                                  * Recalculate the transmit timer / rtt.
1714                                  *
1715                                  * Some boxes send broken timestamp replies
1716                                  * during the SYN+ACK phase, ignore
1717                                  * timestamps of 0 or we could calculate a
1718                                  * huge RTT and blow up the retransmit timer.
1719                                  */
1720                                 if ((to.to_flags & TOF_TS) != 0 &&
1721                                     to.to_tsecr) {
1722                                         u_int t;
1723
1724                                         t = tcp_ts_getticks() - to.to_tsecr;
1725                                         if (!tp->t_rttlow || tp->t_rttlow > t)
1726                                                 tp->t_rttlow = t;
1727                                         tcp_xmit_timer(tp,
1728                                             TCP_TS_TO_TICKS(t) + 1);
1729                                 } else if (tp->t_rtttime &&
1730                                     SEQ_GT(th->th_ack, tp->t_rtseq)) {
1731                                         if (!tp->t_rttlow ||
1732                                             tp->t_rttlow > ticks - tp->t_rtttime)
1733                                                 tp->t_rttlow = ticks - tp->t_rtttime;
1734                                         tcp_xmit_timer(tp,
1735                                                         ticks - tp->t_rtttime);
1736                                 }
1737                                 acked = BYTES_THIS_ACK(tp, th);
1738
1739                                 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
1740                                 hhook_run_tcp_est_in(tp, th, &to);
1741
1742                                 TCPSTAT_INC(tcps_rcvackpack);
1743                                 TCPSTAT_ADD(tcps_rcvackbyte, acked);
1744                                 sbdrop(&so->so_snd, acked);
1745                                 if (SEQ_GT(tp->snd_una, tp->snd_recover) &&
1746                                     SEQ_LEQ(th->th_ack, tp->snd_recover))
1747                                         tp->snd_recover = th->th_ack - 1;
1748
1749                                 /*
1750                                  * Let the congestion control algorithm update
1751                                  * congestion control related information. This
1752                                  * typically means increasing the congestion
1753                                  * window.
1754                                  */
1755                                 cc_ack_received(tp, th, CC_ACK);
1756
1757                                 tp->snd_una = th->th_ack;
1758                                 /*
1759                                  * Pull snd_wl2 up to prevent seq wrap relative
1760                                  * to th_ack.
1761                                  */
1762                                 tp->snd_wl2 = th->th_ack;
1763                                 tp->t_dupacks = 0;
1764                                 m_freem(m);
1765
1766                                 /*
1767                                  * If all outstanding data are acked, stop
1768                                  * retransmit timer, otherwise restart timer
1769                                  * using current (possibly backed-off) value.
1770                                  * If process is waiting for space,
1771                                  * wakeup/selwakeup/signal.  If data
1772                                  * are ready to send, let tcp_output
1773                                  * decide between more output or persist.
1774                                  */
1775 #ifdef TCPDEBUG
1776                                 if (so->so_options & SO_DEBUG)
1777                                         tcp_trace(TA_INPUT, ostate, tp,
1778                                             (void *)tcp_saveipgen,
1779                                             &tcp_savetcp, 0);
1780 #endif
1781                                 TCP_PROBE3(debug__input, tp, th,
1782                                         mtod(m, const char *));
1783                                 if (tp->snd_una == tp->snd_max)
1784                                         tcp_timer_activate(tp, TT_REXMT, 0);
1785                                 else if (!tcp_timer_active(tp, TT_PERSIST))
1786                                         tcp_timer_activate(tp, TT_REXMT,
1787                                                       tp->t_rxtcur);
1788                                 sowwakeup(so);
1789                                 if (sbavail(&so->so_snd))
1790                                         (void) tcp_output(tp);
1791                                 goto check_delack;
1792                         }
1793                 } else if (th->th_ack == tp->snd_una &&
1794                     tlen <= sbspace(&so->so_rcv)) {
1795                         int newsize = 0;        /* automatic sockbuf scaling */
1796
1797                         /*
1798                          * This is a pure, in-sequence data packet with
1799                          * nothing on the reassembly queue and we have enough
1800                          * buffer space to take it.
1801                          */
1802                         if (ti_locked == TI_RLOCKED)
1803                                 INP_INFO_RUNLOCK(&V_tcbinfo);
1804                         ti_locked = TI_UNLOCKED;
1805
1806                         /* Clean receiver SACK report if present */
1807                         if ((tp->t_flags & TF_SACK_PERMIT) && tp->rcv_numsacks)
1808                                 tcp_clean_sackreport(tp);
1809                         TCPSTAT_INC(tcps_preddat);
1810                         tp->rcv_nxt += tlen;
1811                         /*
1812                          * Pull snd_wl1 up to prevent seq wrap relative to
1813                          * th_seq.
1814                          */
1815                         tp->snd_wl1 = th->th_seq;
1816                         /*
1817                          * Pull rcv_up up to prevent seq wrap relative to
1818                          * rcv_nxt.
1819                          */
1820                         tp->rcv_up = tp->rcv_nxt;
1821                         TCPSTAT_INC(tcps_rcvpack);
1822                         TCPSTAT_ADD(tcps_rcvbyte, tlen);
1823 #ifdef TCPDEBUG
1824                         if (so->so_options & SO_DEBUG)
1825                                 tcp_trace(TA_INPUT, ostate, tp,
1826                                     (void *)tcp_saveipgen, &tcp_savetcp, 0);
1827 #endif
1828                         TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
1829
1830                 /*
1831                  * Automatic sizing of receive socket buffer.  Often the send
1832                  * buffer size is not optimally adjusted to the actual network
1833                  * conditions at hand (delay bandwidth product).  Setting the
1834                  * buffer size too small limits throughput on links with high
1835                  * bandwidth and high delay (eg. trans-continental/oceanic links).
1836                  *
1837                  * On the receive side the socket buffer memory is only rarely
1838                  * used to any significant extent.  This allows us to be much
1839                  * more aggressive in scaling the receive socket buffer.  For
1840                  * the case that the buffer space is actually used to a large
1841                  * extent and we run out of kernel memory we can simply drop
1842                  * the new segments; TCP on the sender will just retransmit it
1843                  * later.  Setting the buffer size too big may only consume too
1844                  * much kernel memory if the application doesn't read() from
1845                  * the socket or packet loss or reordering makes use of the
1846                  * reassembly queue.
1847                  *
1848                  * The criteria to step up the receive buffer one notch are:
1849                  *  1. Application has not set receive buffer size with
1850                  *     SO_RCVBUF. Setting SO_RCVBUF clears SB_AUTOSIZE.
1851                  *  2. the number of bytes received during the time it takes
1852                  *     one timestamp to be reflected back to us (the RTT);
1853                  *  3. received bytes per RTT is within seven eighth of the
1854                  *     current socket buffer size;
1855                  *  4. receive buffer size has not hit maximal automatic size;
1856                  *
1857                  * This algorithm does one step per RTT at most and only if
1858                  * we receive a bulk stream w/o packet losses or reorderings.
1859                  * Shrinking the buffer during idle times is not necessary as
1860                  * it doesn't consume any memory when idle.
1861                  *
1862                  * TODO: Only step up if the application is actually serving
1863                  * the buffer to better manage the socket buffer resources.
1864                  */
1865                         if (V_tcp_do_autorcvbuf &&
1866                             (to.to_flags & TOF_TS) &&
1867                             to.to_tsecr &&
1868                             (so->so_rcv.sb_flags & SB_AUTOSIZE)) {
1869                                 if (TSTMP_GT(to.to_tsecr, tp->rfbuf_ts) &&
1870                                     to.to_tsecr - tp->rfbuf_ts < hz) {
1871                                         if (tp->rfbuf_cnt >
1872                                             (so->so_rcv.sb_hiwat / 8 * 7) &&
1873                                             so->so_rcv.sb_hiwat <
1874                                             V_tcp_autorcvbuf_max) {
1875                                                 newsize =
1876                                                     min(so->so_rcv.sb_hiwat +
1877                                                     V_tcp_autorcvbuf_inc,
1878                                                     V_tcp_autorcvbuf_max);
1879                                         }
1880                                         /* Start over with next RTT. */
1881                                         tp->rfbuf_ts = 0;
1882                                         tp->rfbuf_cnt = 0;
1883                                 } else
1884                                         tp->rfbuf_cnt += tlen;  /* add up */
1885                         }
1886
1887                         /* Add data to socket buffer. */
1888                         SOCKBUF_LOCK(&so->so_rcv);
1889                         if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
1890                                 m_freem(m);
1891                         } else {
1892                                 /*
1893                                  * Set new socket buffer size.
1894                                  * Give up when limit is reached.
1895                                  */
1896                                 if (newsize)
1897                                         if (!sbreserve_locked(&so->so_rcv,
1898                                             newsize, so, NULL))
1899                                                 so->so_rcv.sb_flags &= ~SB_AUTOSIZE;
1900                                 m_adj(m, drop_hdrlen);  /* delayed header drop */
1901                                 sbappendstream_locked(&so->so_rcv, m, 0);
1902                         }
1903                         /* NB: sorwakeup_locked() does an implicit unlock. */
1904                         sorwakeup_locked(so);
1905                         if (DELAY_ACK(tp, tlen)) {
1906                                 tp->t_flags |= TF_DELACK;
1907                         } else {
1908                                 tp->t_flags |= TF_ACKNOW;
1909                                 tcp_output(tp);
1910                         }
1911                         goto check_delack;
1912                 }
1913         }
1914
1915         /*
1916          * Calculate amount of space in receive window,
1917          * and then do TCP input processing.
1918          * Receive window is amount of space in rcv queue,
1919          * but not less than advertised window.
1920          */
1921         win = sbspace(&so->so_rcv);
1922         if (win < 0)
1923                 win = 0;
1924         tp->rcv_wnd = imax(win, (int)(tp->rcv_adv - tp->rcv_nxt));
1925
1926         /* Reset receive buffer auto scaling when not in bulk receive mode. */
1927         tp->rfbuf_ts = 0;
1928         tp->rfbuf_cnt = 0;
1929
1930         switch (tp->t_state) {
1931
1932         /*
1933          * If the state is SYN_RECEIVED:
1934          *      if seg contains an ACK, but not for our SYN/ACK, send a RST.
1935          */
1936         case TCPS_SYN_RECEIVED:
1937                 if ((thflags & TH_ACK) &&
1938                     (SEQ_LEQ(th->th_ack, tp->snd_una) ||
1939                      SEQ_GT(th->th_ack, tp->snd_max))) {
1940                                 rstreason = BANDLIM_RST_OPENPORT;
1941                                 goto dropwithreset;
1942                 }
1943                 break;
1944
1945         /*
1946          * If the state is SYN_SENT:
1947          *      if seg contains an ACK, but not for our SYN, drop the input.
1948          *      if seg contains a RST, then drop the connection.
1949          *      if seg does not contain SYN, then drop it.
1950          * Otherwise this is an acceptable SYN segment
1951          *      initialize tp->rcv_nxt and tp->irs
1952          *      if seg contains ack then advance tp->snd_una
1953          *      if seg contains an ECE and ECN support is enabled, the stream
1954          *          is ECN capable.
1955          *      if SYN has been acked change to ESTABLISHED else SYN_RCVD state
1956          *      arrange for segment to be acked (eventually)
1957          *      continue processing rest of data/controls, beginning with URG
1958          */
1959         case TCPS_SYN_SENT:
1960                 if ((thflags & TH_ACK) &&
1961                     (SEQ_LEQ(th->th_ack, tp->iss) ||
1962                      SEQ_GT(th->th_ack, tp->snd_max))) {
1963                         rstreason = BANDLIM_UNLIMITED;
1964                         goto dropwithreset;
1965                 }
1966                 if ((thflags & (TH_ACK|TH_RST)) == (TH_ACK|TH_RST)) {
1967                         TCP_PROBE5(connect__refused, NULL, tp,
1968                             mtod(m, const char *), tp, th);
1969                         tp = tcp_drop(tp, ECONNREFUSED);
1970                 }
1971                 if (thflags & TH_RST)
1972                         goto drop;
1973                 if (!(thflags & TH_SYN))
1974                         goto drop;
1975
1976                 tp->irs = th->th_seq;
1977                 tcp_rcvseqinit(tp);
1978                 if (thflags & TH_ACK) {
1979                         TCPSTAT_INC(tcps_connects);
1980                         soisconnected(so);
1981 #ifdef MAC
1982                         mac_socketpeer_set_from_mbuf(m, so);
1983 #endif
1984                         /* Do window scaling on this connection? */
1985                         if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
1986                                 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
1987                                 tp->rcv_scale = tp->request_r_scale;
1988                         }
1989                         tp->rcv_adv += imin(tp->rcv_wnd,
1990                             TCP_MAXWIN << tp->rcv_scale);
1991                         tp->snd_una++;          /* SYN is acked */
1992                         /*
1993                          * If there's data, delay ACK; if there's also a FIN
1994                          * ACKNOW will be turned on later.
1995                          */
1996                         if (DELAY_ACK(tp, tlen) && tlen != 0)
1997                                 tcp_timer_activate(tp, TT_DELACK,
1998                                     tcp_delacktime);
1999                         else
2000                                 tp->t_flags |= TF_ACKNOW;
2001
2002                         if ((thflags & TH_ECE) && V_tcp_do_ecn) {
2003                                 tp->t_flags |= TF_ECN_PERMIT;
2004                                 TCPSTAT_INC(tcps_ecn_shs);
2005                         }
2006
2007                         /*
2008                          * Received <SYN,ACK> in SYN_SENT[*] state.
2009                          * Transitions:
2010                          *      SYN_SENT  --> ESTABLISHED
2011                          *      SYN_SENT* --> FIN_WAIT_1
2012                          */
2013                         tp->t_starttime = ticks;
2014                         if (tp->t_flags & TF_NEEDFIN) {
2015                                 tcp_state_change(tp, TCPS_FIN_WAIT_1);
2016                                 tp->t_flags &= ~TF_NEEDFIN;
2017                                 thflags &= ~TH_SYN;
2018                         } else {
2019                                 tcp_state_change(tp, TCPS_ESTABLISHED);
2020                                 TCP_PROBE5(connect__established, NULL, tp,
2021                                     mtod(m, const char *), tp, th);
2022                                 cc_conn_init(tp);
2023                                 tcp_timer_activate(tp, TT_KEEP,
2024                                     TP_KEEPIDLE(tp));
2025                         }
2026                 } else {
2027                         /*
2028                          * Received initial SYN in SYN-SENT[*] state =>
2029                          * simultaneous open.
2030                          * If it succeeds, connection is * half-synchronized.
2031                          * Otherwise, do 3-way handshake:
2032                          *        SYN-SENT -> SYN-RECEIVED
2033                          *        SYN-SENT* -> SYN-RECEIVED*
2034                          */
2035                         tp->t_flags |= (TF_ACKNOW | TF_NEEDSYN);
2036                         tcp_timer_activate(tp, TT_REXMT, 0);
2037                         tcp_state_change(tp, TCPS_SYN_RECEIVED);
2038                 }
2039
2040                 KASSERT(ti_locked == TI_RLOCKED, ("%s: trimthenstep6: "
2041                     "ti_locked %d", __func__, ti_locked));
2042                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2043                 INP_WLOCK_ASSERT(tp->t_inpcb);
2044
2045                 /*
2046                  * Advance th->th_seq to correspond to first data byte.
2047                  * If data, trim to stay within window,
2048                  * dropping FIN if necessary.
2049                  */
2050                 th->th_seq++;
2051                 if (tlen > tp->rcv_wnd) {
2052                         todrop = tlen - tp->rcv_wnd;
2053                         m_adj(m, -todrop);
2054                         tlen = tp->rcv_wnd;
2055                         thflags &= ~TH_FIN;
2056                         TCPSTAT_INC(tcps_rcvpackafterwin);
2057                         TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2058                 }
2059                 tp->snd_wl1 = th->th_seq - 1;
2060                 tp->rcv_up = th->th_seq;
2061                 /*
2062                  * Client side of transaction: already sent SYN and data.
2063                  * If the remote host used T/TCP to validate the SYN,
2064                  * our data will be ACK'd; if so, enter normal data segment
2065                  * processing in the middle of step 5, ack processing.
2066                  * Otherwise, goto step 6.
2067                  */
2068                 if (thflags & TH_ACK)
2069                         goto process_ACK;
2070
2071                 goto step6;
2072
2073         /*
2074          * If the state is LAST_ACK or CLOSING or TIME_WAIT:
2075          *      do normal processing.
2076          *
2077          * NB: Leftover from RFC1644 T/TCP.  Cases to be reused later.
2078          */
2079         case TCPS_LAST_ACK:
2080         case TCPS_CLOSING:
2081                 break;  /* continue normal processing */
2082         }
2083
2084         /*
2085          * States other than LISTEN or SYN_SENT.
2086          * First check the RST flag and sequence number since reset segments
2087          * are exempt from the timestamp and connection count tests.  This
2088          * fixes a bug introduced by the Stevens, vol. 2, p. 960 bugfix
2089          * below which allowed reset segments in half the sequence space
2090          * to fall though and be processed (which gives forged reset
2091          * segments with a random sequence number a 50 percent chance of
2092          * killing a connection).
2093          * Then check timestamp, if present.
2094          * Then check the connection count, if present.
2095          * Then check that at least some bytes of segment are within
2096          * receive window.  If segment begins before rcv_nxt,
2097          * drop leading data (and SYN); if nothing left, just ack.
2098          */
2099         if (thflags & TH_RST) {
2100                 /*
2101                  * RFC5961 Section 3.2
2102                  *
2103                  * - RST drops connection only if SEG.SEQ == RCV.NXT.
2104                  * - If RST is in window, we send challenge ACK.
2105                  *
2106                  * Note: to take into account delayed ACKs, we should
2107                  *   test against last_ack_sent instead of rcv_nxt.
2108                  * Note 2: we handle special case of closed window, not
2109                  *   covered by the RFC.
2110                  */
2111                 if ((SEQ_GEQ(th->th_seq, tp->last_ack_sent) &&
2112                     SEQ_LT(th->th_seq, tp->last_ack_sent + tp->rcv_wnd)) ||
2113                     (tp->rcv_wnd == 0 && tp->last_ack_sent == th->th_seq)) {
2114
2115                         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2116                         KASSERT(ti_locked == TI_RLOCKED,
2117                             ("%s: TH_RST ti_locked %d, th %p tp %p",
2118                             __func__, ti_locked, th, tp));
2119                         KASSERT(tp->t_state != TCPS_SYN_SENT,
2120                             ("%s: TH_RST for TCPS_SYN_SENT th %p tp %p",
2121                             __func__, th, tp));
2122
2123                         if (V_tcp_insecure_rst ||
2124                             tp->last_ack_sent == th->th_seq) {
2125                                 TCPSTAT_INC(tcps_drops);
2126                                 /* Drop the connection. */
2127                                 switch (tp->t_state) {
2128                                 case TCPS_SYN_RECEIVED:
2129                                         so->so_error = ECONNREFUSED;
2130                                         goto close;
2131                                 case TCPS_ESTABLISHED:
2132                                 case TCPS_FIN_WAIT_1:
2133                                 case TCPS_FIN_WAIT_2:
2134                                 case TCPS_CLOSE_WAIT:
2135                                         so->so_error = ECONNRESET;
2136                                 close:
2137                                         tcp_state_change(tp, TCPS_CLOSED);
2138                                         /* FALLTHROUGH */
2139                                 default:
2140                                         tp = tcp_close(tp);
2141                                 }
2142                         } else {
2143                                 TCPSTAT_INC(tcps_badrst);
2144                                 /* Send challenge ACK. */
2145                                 tcp_respond(tp, mtod(m, void *), th, m,
2146                                     tp->rcv_nxt, tp->snd_nxt, TH_ACK);
2147                                 tp->last_ack_sent = tp->rcv_nxt;
2148                                 m = NULL;
2149                         }
2150                 }
2151                 goto drop;
2152         }
2153
2154         /*
2155          * RFC5961 Section 4.2
2156          * Send challenge ACK for any SYN in synchronized state.
2157          */
2158         if ((thflags & TH_SYN) && tp->t_state != TCPS_SYN_SENT) {
2159                 KASSERT(ti_locked == TI_RLOCKED,
2160                     ("tcp_do_segment: TH_SYN ti_locked %d", ti_locked));
2161                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2162
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                 drop_hdrlen += todrop;  /* drop from the top afterwards */
2258                 th->th_seq += todrop;
2259                 tlen -= todrop;
2260                 if (th->th_urp > todrop)
2261                         th->th_urp -= todrop;
2262                 else {
2263                         thflags &= ~TH_URG;
2264                         th->th_urp = 0;
2265                 }
2266         }
2267
2268         /*
2269          * If new data are received on a connection after the
2270          * user processes are gone, then RST the other end.
2271          */
2272         if ((so->so_state & SS_NOFDREF) &&
2273             tp->t_state > TCPS_CLOSE_WAIT && tlen) {
2274                 KASSERT(ti_locked == TI_RLOCKED, ("%s: SS_NOFDEREF && "
2275                     "CLOSE_WAIT && tlen ti_locked %d", __func__, ti_locked));
2276                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2277
2278                 if ((s = tcp_log_addrs(inc, th, NULL, NULL))) {
2279                         log(LOG_DEBUG, "%s; %s: %s: Received %d bytes of data "
2280                             "after socket was closed, "
2281                             "sending RST and removing tcpcb\n",
2282                             s, __func__, tcpstates[tp->t_state], tlen);
2283                         free(s, M_TCPLOG);
2284                 }
2285                 tp = tcp_close(tp);
2286                 TCPSTAT_INC(tcps_rcvafterclose);
2287                 rstreason = BANDLIM_UNLIMITED;
2288                 goto dropwithreset;
2289         }
2290
2291         /*
2292          * If segment ends after window, drop trailing data
2293          * (and PUSH and FIN); if nothing left, just ACK.
2294          */
2295         todrop = (th->th_seq + tlen) - (tp->rcv_nxt + tp->rcv_wnd);
2296         if (todrop > 0) {
2297                 TCPSTAT_INC(tcps_rcvpackafterwin);
2298                 if (todrop >= tlen) {
2299                         TCPSTAT_ADD(tcps_rcvbyteafterwin, tlen);
2300                         /*
2301                          * If window is closed can only take segments at
2302                          * window edge, and have to drop data and PUSH from
2303                          * incoming segments.  Continue processing, but
2304                          * remember to ack.  Otherwise, drop segment
2305                          * and ack.
2306                          */
2307                         if (tp->rcv_wnd == 0 && th->th_seq == tp->rcv_nxt) {
2308                                 tp->t_flags |= TF_ACKNOW;
2309                                 TCPSTAT_INC(tcps_rcvwinprobe);
2310                         } else
2311                                 goto dropafterack;
2312                 } else
2313                         TCPSTAT_ADD(tcps_rcvbyteafterwin, todrop);
2314                 m_adj(m, -todrop);
2315                 tlen -= todrop;
2316                 thflags &= ~(TH_PUSH|TH_FIN);
2317         }
2318
2319         /*
2320          * If last ACK falls within this segment's sequence numbers,
2321          * record its timestamp.
2322          * NOTE:
2323          * 1) That the test incorporates suggestions from the latest
2324          *    proposal of the tcplw@cray.com list (Braden 1993/04/26).
2325          * 2) That updating only on newer timestamps interferes with
2326          *    our earlier PAWS tests, so this check should be solely
2327          *    predicated on the sequence space of this segment.
2328          * 3) That we modify the segment boundary check to be
2329          *        Last.ACK.Sent <= SEG.SEQ + SEG.Len
2330          *    instead of RFC1323's
2331          *        Last.ACK.Sent < SEG.SEQ + SEG.Len,
2332          *    This modified check allows us to overcome RFC1323's
2333          *    limitations as described in Stevens TCP/IP Illustrated
2334          *    Vol. 2 p.869. In such cases, we can still calculate the
2335          *    RTT correctly when RCV.NXT == Last.ACK.Sent.
2336          */
2337         if ((to.to_flags & TOF_TS) != 0 &&
2338             SEQ_LEQ(th->th_seq, tp->last_ack_sent) &&
2339             SEQ_LEQ(tp->last_ack_sent, th->th_seq + tlen +
2340                 ((thflags & (TH_SYN|TH_FIN)) != 0))) {
2341                 tp->ts_recent_age = tcp_ts_getticks();
2342                 tp->ts_recent = to.to_tsval;
2343         }
2344
2345         /*
2346          * If the ACK bit is off:  if in SYN-RECEIVED state or SENDSYN
2347          * flag is on (half-synchronized state), then queue data for
2348          * later processing; else drop segment and return.
2349          */
2350         if ((thflags & TH_ACK) == 0) {
2351                 if (tp->t_state == TCPS_SYN_RECEIVED ||
2352                     (tp->t_flags & TF_NEEDSYN))
2353                         goto step6;
2354                 else if (tp->t_flags & TF_ACKNOW)
2355                         goto dropafterack;
2356                 else
2357                         goto drop;
2358         }
2359
2360         /*
2361          * Ack processing.
2362          */
2363         switch (tp->t_state) {
2364
2365         /*
2366          * In SYN_RECEIVED state, the ack ACKs our SYN, so enter
2367          * ESTABLISHED state and continue processing.
2368          * The ACK was checked above.
2369          */
2370         case TCPS_SYN_RECEIVED:
2371
2372                 TCPSTAT_INC(tcps_connects);
2373                 soisconnected(so);
2374                 /* Do window scaling? */
2375                 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2376                         (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2377                         tp->rcv_scale = tp->request_r_scale;
2378                         tp->snd_wnd = tiwin;
2379                 }
2380                 /*
2381                  * Make transitions:
2382                  *      SYN-RECEIVED  -> ESTABLISHED
2383                  *      SYN-RECEIVED* -> FIN-WAIT-1
2384                  */
2385                 tp->t_starttime = ticks;
2386                 if (tp->t_flags & TF_NEEDFIN) {
2387                         tcp_state_change(tp, TCPS_FIN_WAIT_1);
2388                         tp->t_flags &= ~TF_NEEDFIN;
2389                 } else {
2390                         tcp_state_change(tp, TCPS_ESTABLISHED);
2391                         TCP_PROBE5(accept__established, NULL, tp,
2392                             mtod(m, const char *), tp, th);
2393                         cc_conn_init(tp);
2394                         tcp_timer_activate(tp, TT_KEEP, TP_KEEPIDLE(tp));
2395                 }
2396                 /*
2397                  * If segment contains data or ACK, will call tcp_reass()
2398                  * later; if not, do so now to pass queued data to user.
2399                  */
2400                 if (tlen == 0 && (thflags & TH_FIN) == 0)
2401                         (void) tcp_reass(tp, (struct tcphdr *)0, 0,
2402                             (struct mbuf *)0);
2403                 tp->snd_wl1 = th->th_seq - 1;
2404                 /* FALLTHROUGH */
2405
2406         /*
2407          * In ESTABLISHED state: drop duplicate ACKs; ACK out of range
2408          * ACKs.  If the ack is in the range
2409          *      tp->snd_una < th->th_ack <= tp->snd_max
2410          * then advance tp->snd_una to th->th_ack and drop
2411          * data from the retransmission queue.  If this ACK reflects
2412          * more up to date window information we update our window information.
2413          */
2414         case TCPS_ESTABLISHED:
2415         case TCPS_FIN_WAIT_1:
2416         case TCPS_FIN_WAIT_2:
2417         case TCPS_CLOSE_WAIT:
2418         case TCPS_CLOSING:
2419         case TCPS_LAST_ACK:
2420                 if (SEQ_GT(th->th_ack, tp->snd_max)) {
2421                         TCPSTAT_INC(tcps_rcvacktoomuch);
2422                         goto dropafterack;
2423                 }
2424                 if ((tp->t_flags & TF_SACK_PERMIT) &&
2425                     ((to.to_flags & TOF_SACK) ||
2426                      !TAILQ_EMPTY(&tp->snd_holes)))
2427                         tcp_sack_doack(tp, &to, th->th_ack);
2428                 else
2429                         /*
2430                          * Reset the value so that previous (valid) value
2431                          * from the last ack with SACK doesn't get used.
2432                          */
2433                         tp->sackhint.sacked_bytes = 0;
2434
2435                 /* Run HHOOK_TCP_ESTABLISHED_IN helper hooks. */
2436                 hhook_run_tcp_est_in(tp, th, &to);
2437
2438                 if (SEQ_LEQ(th->th_ack, tp->snd_una)) {
2439                         if (tlen == 0 && tiwin == tp->snd_wnd) {
2440                                 /*
2441                                  * If this is the first time we've seen a
2442                                  * FIN from the remote, this is not a
2443                                  * duplicate and it needs to be processed
2444                                  * normally.  This happens during a
2445                                  * simultaneous close.
2446                                  */
2447                                 if ((thflags & TH_FIN) &&
2448                                     (TCPS_HAVERCVDFIN(tp->t_state) == 0)) {
2449                                         tp->t_dupacks = 0;
2450                                         break;
2451                                 }
2452                                 TCPSTAT_INC(tcps_rcvdupack);
2453                                 /*
2454                                  * If we have outstanding data (other than
2455                                  * a window probe), this is a completely
2456                                  * duplicate ack (ie, window info didn't
2457                                  * change and FIN isn't set),
2458                                  * the ack is the biggest we've
2459                                  * seen and we've seen exactly our rexmt
2460                                  * threshhold of them, assume a packet
2461                                  * has been dropped and retransmit it.
2462                                  * Kludge snd_nxt & the congestion
2463                                  * window so we send only this one
2464                                  * packet.
2465                                  *
2466                                  * We know we're losing at the current
2467                                  * window size so do congestion avoidance
2468                                  * (set ssthresh to half the current window
2469                                  * and pull our congestion window back to
2470                                  * the new ssthresh).
2471                                  *
2472                                  * Dup acks mean that packets have left the
2473                                  * network (they're now cached at the receiver)
2474                                  * so bump cwnd by the amount in the receiver
2475                                  * to keep a constant cwnd packets in the
2476                                  * network.
2477                                  *
2478                                  * When using TCP ECN, notify the peer that
2479                                  * we reduced the cwnd.
2480                                  */
2481                                 if (!tcp_timer_active(tp, TT_REXMT) ||
2482                                     th->th_ack != tp->snd_una)
2483                                         tp->t_dupacks = 0;
2484                                 else if (++tp->t_dupacks > tcprexmtthresh ||
2485                                      IN_FASTRECOVERY(tp->t_flags)) {
2486                                         cc_ack_received(tp, th, CC_DUPACK);
2487                                         if ((tp->t_flags & TF_SACK_PERMIT) &&
2488                                             IN_FASTRECOVERY(tp->t_flags)) {
2489                                                 int awnd;
2490
2491                                                 /*
2492                                                  * Compute the amount of data in flight first.
2493                                                  * We can inject new data into the pipe iff
2494                                                  * we have less than 1/2 the original window's
2495                                                  * worth of data in flight.
2496                                                  */
2497                                                 if (V_tcp_do_rfc6675_pipe)
2498                                                         awnd = tcp_compute_pipe(tp);
2499                                                 else
2500                                                         awnd = (tp->snd_nxt - tp->snd_fack) +
2501                                                                 tp->sackhint.sack_bytes_rexmit;
2502
2503                                                 if (awnd < tp->snd_ssthresh) {
2504                                                         tp->snd_cwnd += tp->t_maxseg;
2505                                                         if (tp->snd_cwnd > tp->snd_ssthresh)
2506                                                                 tp->snd_cwnd = tp->snd_ssthresh;
2507                                                 }
2508                                         } else
2509                                                 tp->snd_cwnd += tp->t_maxseg;
2510                                         (void) tcp_output(tp);
2511                                         goto drop;
2512                                 } else if (tp->t_dupacks == tcprexmtthresh) {
2513                                         tcp_seq onxt = tp->snd_nxt;
2514
2515                                         /*
2516                                          * If we're doing sack, check to
2517                                          * see if we're already in sack
2518                                          * recovery. If we're not doing sack,
2519                                          * check to see if we're in newreno
2520                                          * recovery.
2521                                          */
2522                                         if (tp->t_flags & TF_SACK_PERMIT) {
2523                                                 if (IN_FASTRECOVERY(tp->t_flags)) {
2524                                                         tp->t_dupacks = 0;
2525                                                         break;
2526                                                 }
2527                                         } else {
2528                                                 if (SEQ_LEQ(th->th_ack,
2529                                                     tp->snd_recover)) {
2530                                                         tp->t_dupacks = 0;
2531                                                         break;
2532                                                 }
2533                                         }
2534                                         /* Congestion signal before ack. */
2535                                         cc_cong_signal(tp, th, CC_NDUPACK);
2536                                         cc_ack_received(tp, th, CC_DUPACK);
2537                                         tcp_timer_activate(tp, TT_REXMT, 0);
2538                                         tp->t_rtttime = 0;
2539                                         if (tp->t_flags & TF_SACK_PERMIT) {
2540                                                 TCPSTAT_INC(
2541                                                     tcps_sack_recovery_episode);
2542                                                 tp->sack_newdata = tp->snd_nxt;
2543                                                 tp->snd_cwnd = tp->t_maxseg;
2544                                                 (void) tcp_output(tp);
2545                                                 goto drop;
2546                                         }
2547                                         tp->snd_nxt = th->th_ack;
2548                                         tp->snd_cwnd = tp->t_maxseg;
2549                                         (void) tcp_output(tp);
2550                                         KASSERT(tp->snd_limited <= 2,
2551                                             ("%s: tp->snd_limited too big",
2552                                             __func__));
2553                                         tp->snd_cwnd = tp->snd_ssthresh +
2554                                              tp->t_maxseg *
2555                                              (tp->t_dupacks - tp->snd_limited);
2556                                         if (SEQ_GT(onxt, tp->snd_nxt))
2557                                                 tp->snd_nxt = onxt;
2558                                         goto drop;
2559                                 } else if (V_tcp_do_rfc3042) {
2560                                         /*
2561                                          * Process first and second duplicate
2562                                          * ACKs. Each indicates a segment
2563                                          * leaving the network, creating room
2564                                          * for more. Make sure we can send a
2565                                          * packet on reception of each duplicate
2566                                          * ACK by increasing snd_cwnd by one
2567                                          * segment. Restore the original
2568                                          * snd_cwnd after packet transmission.
2569                                          */
2570                                         cc_ack_received(tp, th, CC_DUPACK);
2571                                         u_long oldcwnd = tp->snd_cwnd;
2572                                         tcp_seq oldsndmax = tp->snd_max;
2573                                         u_int sent;
2574                                         int avail;
2575
2576                                         KASSERT(tp->t_dupacks == 1 ||
2577                                             tp->t_dupacks == 2,
2578                                             ("%s: dupacks not 1 or 2",
2579                                             __func__));
2580                                         if (tp->t_dupacks == 1)
2581                                                 tp->snd_limited = 0;
2582                                         tp->snd_cwnd =
2583                                             (tp->snd_nxt - tp->snd_una) +
2584                                             (tp->t_dupacks - tp->snd_limited) *
2585                                             tp->t_maxseg;
2586                                         /*
2587                                          * Only call tcp_output when there
2588                                          * is new data available to be sent.
2589                                          * Otherwise we would send pure ACKs.
2590                                          */
2591                                         SOCKBUF_LOCK(&so->so_snd);
2592                                         avail = sbavail(&so->so_snd) -
2593                                             (tp->snd_nxt - tp->snd_una);
2594                                         SOCKBUF_UNLOCK(&so->so_snd);
2595                                         if (avail > 0)
2596                                                 (void) tcp_output(tp);
2597                                         sent = tp->snd_max - oldsndmax;
2598                                         if (sent > tp->t_maxseg) {
2599                                                 KASSERT((tp->t_dupacks == 2 &&
2600                                                     tp->snd_limited == 0) ||
2601                                                    (sent == tp->t_maxseg + 1 &&
2602                                                     tp->t_flags & TF_SENTFIN),
2603                                                     ("%s: sent too much",
2604                                                     __func__));
2605                                                 tp->snd_limited = 2;
2606                                         } else if (sent > 0)
2607                                                 ++tp->snd_limited;
2608                                         tp->snd_cwnd = oldcwnd;
2609                                         goto drop;
2610                                 }
2611                         } else
2612                                 tp->t_dupacks = 0;
2613                         break;
2614                 }
2615
2616                 KASSERT(SEQ_GT(th->th_ack, tp->snd_una),
2617                     ("%s: th_ack <= snd_una", __func__));
2618
2619                 /*
2620                  * If the congestion window was inflated to account
2621                  * for the other side's cached packets, retract it.
2622                  */
2623                 if (IN_FASTRECOVERY(tp->t_flags)) {
2624                         if (SEQ_LT(th->th_ack, tp->snd_recover)) {
2625                                 if (tp->t_flags & TF_SACK_PERMIT)
2626                                         tcp_sack_partialack(tp, th);
2627                                 else
2628                                         tcp_newreno_partial_ack(tp, th);
2629                         } else
2630                                 cc_post_recovery(tp, th);
2631                 }
2632                 tp->t_dupacks = 0;
2633                 /*
2634                  * If we reach this point, ACK is not a duplicate,
2635                  *     i.e., it ACKs something we sent.
2636                  */
2637                 if (tp->t_flags & TF_NEEDSYN) {
2638                         /*
2639                          * T/TCP: Connection was half-synchronized, and our
2640                          * SYN has been ACK'd (so connection is now fully
2641                          * synchronized).  Go to non-starred state,
2642                          * increment snd_una for ACK of SYN, and check if
2643                          * we can do window scaling.
2644                          */
2645                         tp->t_flags &= ~TF_NEEDSYN;
2646                         tp->snd_una++;
2647                         /* Do window scaling? */
2648                         if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
2649                                 (TF_RCVD_SCALE|TF_REQ_SCALE)) {
2650                                 tp->rcv_scale = tp->request_r_scale;
2651                                 /* Send window already scaled. */
2652                         }
2653                 }
2654
2655 process_ACK:
2656                 INP_WLOCK_ASSERT(tp->t_inpcb);
2657
2658                 acked = BYTES_THIS_ACK(tp, th);
2659                 TCPSTAT_INC(tcps_rcvackpack);
2660                 TCPSTAT_ADD(tcps_rcvackbyte, acked);
2661
2662                 /*
2663                  * If we just performed our first retransmit, and the ACK
2664                  * arrives within our recovery window, then it was a mistake
2665                  * to do the retransmit in the first place.  Recover our
2666                  * original cwnd and ssthresh, and proceed to transmit where
2667                  * we left off.
2668                  */
2669                 if (tp->t_rxtshift == 1 && tp->t_flags & TF_PREVVALID &&
2670                     (int)(ticks - tp->t_badrxtwin) < 0)
2671                         cc_cong_signal(tp, th, CC_RTO_ERR);
2672
2673                 /*
2674                  * If we have a timestamp reply, update smoothed
2675                  * round trip time.  If no timestamp is present but
2676                  * transmit timer is running and timed sequence
2677                  * number was acked, update smoothed round trip time.
2678                  * Since we now have an rtt measurement, cancel the
2679                  * timer backoff (cf., Phil Karn's retransmit alg.).
2680                  * Recompute the initial retransmit timer.
2681                  *
2682                  * Some boxes send broken timestamp replies
2683                  * during the SYN+ACK phase, ignore
2684                  * timestamps of 0 or we could calculate a
2685                  * huge RTT and blow up the retransmit timer.
2686                  */
2687                 if ((to.to_flags & TOF_TS) != 0 && to.to_tsecr) {
2688                         u_int t;
2689
2690                         t = tcp_ts_getticks() - to.to_tsecr;
2691                         if (!tp->t_rttlow || tp->t_rttlow > t)
2692                                 tp->t_rttlow = t;
2693                         tcp_xmit_timer(tp, TCP_TS_TO_TICKS(t) + 1);
2694                 } else if (tp->t_rtttime && SEQ_GT(th->th_ack, tp->t_rtseq)) {
2695                         if (!tp->t_rttlow || tp->t_rttlow > ticks - tp->t_rtttime)
2696                                 tp->t_rttlow = ticks - tp->t_rtttime;
2697                         tcp_xmit_timer(tp, ticks - tp->t_rtttime);
2698                 }
2699
2700                 /*
2701                  * If all outstanding data is acked, stop retransmit
2702                  * timer and remember to restart (more output or persist).
2703                  * If there is more data to be acked, restart retransmit
2704                  * timer, using current (possibly backed-off) value.
2705                  */
2706                 if (th->th_ack == tp->snd_max) {
2707                         tcp_timer_activate(tp, TT_REXMT, 0);
2708                         needoutput = 1;
2709                 } else if (!tcp_timer_active(tp, TT_PERSIST))
2710                         tcp_timer_activate(tp, TT_REXMT, tp->t_rxtcur);
2711
2712                 /*
2713                  * If no data (only SYN) was ACK'd,
2714                  *    skip rest of ACK processing.
2715                  */
2716                 if (acked == 0)
2717                         goto step6;
2718
2719                 /*
2720                  * Let the congestion control algorithm update congestion
2721                  * control related information. This typically means increasing
2722                  * the congestion window.
2723                  */
2724                 cc_ack_received(tp, th, CC_ACK);
2725
2726                 SOCKBUF_LOCK(&so->so_snd);
2727                 if (acked > sbavail(&so->so_snd)) {
2728                         tp->snd_wnd -= sbavail(&so->so_snd);
2729                         mfree = sbcut_locked(&so->so_snd,
2730                             (int)sbavail(&so->so_snd));
2731                         ourfinisacked = 1;
2732                 } else {
2733                         mfree = sbcut_locked(&so->so_snd, acked);
2734                         tp->snd_wnd -= acked;
2735                         ourfinisacked = 0;
2736                 }
2737                 /* NB: sowwakeup_locked() does an implicit unlock. */
2738                 sowwakeup_locked(so);
2739                 m_freem(mfree);
2740                 /* Detect una wraparound. */
2741                 if (!IN_RECOVERY(tp->t_flags) &&
2742                     SEQ_GT(tp->snd_una, tp->snd_recover) &&
2743                     SEQ_LEQ(th->th_ack, tp->snd_recover))
2744                         tp->snd_recover = th->th_ack - 1;
2745                 /* XXXLAS: Can this be moved up into cc_post_recovery? */
2746                 if (IN_RECOVERY(tp->t_flags) &&
2747                     SEQ_GEQ(th->th_ack, tp->snd_recover)) {
2748                         EXIT_RECOVERY(tp->t_flags);
2749                 }
2750                 tp->snd_una = th->th_ack;
2751                 if (tp->t_flags & TF_SACK_PERMIT) {
2752                         if (SEQ_GT(tp->snd_una, tp->snd_recover))
2753                                 tp->snd_recover = tp->snd_una;
2754                 }
2755                 if (SEQ_LT(tp->snd_nxt, tp->snd_una))
2756                         tp->snd_nxt = tp->snd_una;
2757
2758                 switch (tp->t_state) {
2759
2760                 /*
2761                  * In FIN_WAIT_1 STATE in addition to the processing
2762                  * for the ESTABLISHED state if our FIN is now acknowledged
2763                  * then enter FIN_WAIT_2.
2764                  */
2765                 case TCPS_FIN_WAIT_1:
2766                         if (ourfinisacked) {
2767                                 /*
2768                                  * If we can't receive any more
2769                                  * data, then closing user can proceed.
2770                                  * Starting the timer is contrary to the
2771                                  * specification, but if we don't get a FIN
2772                                  * we'll hang forever.
2773                                  *
2774                                  * XXXjl:
2775                                  * we should release the tp also, and use a
2776                                  * compressed state.
2777                                  */
2778                                 if (so->so_rcv.sb_state & SBS_CANTRCVMORE) {
2779                                         soisdisconnected(so);
2780                                         tcp_timer_activate(tp, TT_2MSL,
2781                                             (tcp_fast_finwait2_recycle ?
2782                                             tcp_finwait2_timeout :
2783                                             TP_MAXIDLE(tp)));
2784                                 }
2785                                 tcp_state_change(tp, TCPS_FIN_WAIT_2);
2786                         }
2787                         break;
2788
2789                 /*
2790                  * In CLOSING STATE in addition to the processing for
2791                  * the ESTABLISHED state if the ACK acknowledges our FIN
2792                  * then enter the TIME-WAIT state, otherwise ignore
2793                  * the segment.
2794                  */
2795                 case TCPS_CLOSING:
2796                         if (ourfinisacked) {
2797                                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2798                                 tcp_twstart(tp);
2799                                 INP_INFO_RUNLOCK(&V_tcbinfo);
2800                                 m_freem(m);
2801                                 return;
2802                         }
2803                         break;
2804
2805                 /*
2806                  * In LAST_ACK, we may still be waiting for data to drain
2807                  * and/or to be acked, as well as for the ack of our FIN.
2808                  * If our FIN is now acknowledged, delete the TCB,
2809                  * enter the closed state and return.
2810                  */
2811                 case TCPS_LAST_ACK:
2812                         if (ourfinisacked) {
2813                                 INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
2814                                 tp = tcp_close(tp);
2815                                 goto drop;
2816                         }
2817                         break;
2818                 }
2819         }
2820
2821 step6:
2822         INP_WLOCK_ASSERT(tp->t_inpcb);
2823
2824         /*
2825          * Update window information.
2826          * Don't look at window if no ACK: TAC's send garbage on first SYN.
2827          */
2828         if ((thflags & TH_ACK) &&
2829             (SEQ_LT(tp->snd_wl1, th->th_seq) ||
2830             (tp->snd_wl1 == th->th_seq && (SEQ_LT(tp->snd_wl2, th->th_ack) ||
2831              (tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd))))) {
2832                 /* keep track of pure window updates */
2833                 if (tlen == 0 &&
2834                     tp->snd_wl2 == th->th_ack && tiwin > tp->snd_wnd)
2835                         TCPSTAT_INC(tcps_rcvwinupd);
2836                 tp->snd_wnd = tiwin;
2837                 tp->snd_wl1 = th->th_seq;
2838                 tp->snd_wl2 = th->th_ack;
2839                 if (tp->snd_wnd > tp->max_sndwnd)
2840                         tp->max_sndwnd = tp->snd_wnd;
2841                 needoutput = 1;
2842         }
2843
2844         /*
2845          * Process segments with URG.
2846          */
2847         if ((thflags & TH_URG) && th->th_urp &&
2848             TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2849                 /*
2850                  * This is a kludge, but if we receive and accept
2851                  * random urgent pointers, we'll crash in
2852                  * soreceive.  It's hard to imagine someone
2853                  * actually wanting to send this much urgent data.
2854                  */
2855                 SOCKBUF_LOCK(&so->so_rcv);
2856                 if (th->th_urp + sbavail(&so->so_rcv) > sb_max) {
2857                         th->th_urp = 0;                 /* XXX */
2858                         thflags &= ~TH_URG;             /* XXX */
2859                         SOCKBUF_UNLOCK(&so->so_rcv);    /* XXX */
2860                         goto dodata;                    /* XXX */
2861                 }
2862                 /*
2863                  * If this segment advances the known urgent pointer,
2864                  * then mark the data stream.  This should not happen
2865                  * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since
2866                  * a FIN has been received from the remote side.
2867                  * In these states we ignore the URG.
2868                  *
2869                  * According to RFC961 (Assigned Protocols),
2870                  * the urgent pointer points to the last octet
2871                  * of urgent data.  We continue, however,
2872                  * to consider it to indicate the first octet
2873                  * of data past the urgent section as the original
2874                  * spec states (in one of two places).
2875                  */
2876                 if (SEQ_GT(th->th_seq+th->th_urp, tp->rcv_up)) {
2877                         tp->rcv_up = th->th_seq + th->th_urp;
2878                         so->so_oobmark = sbavail(&so->so_rcv) +
2879                             (tp->rcv_up - tp->rcv_nxt) - 1;
2880                         if (so->so_oobmark == 0)
2881                                 so->so_rcv.sb_state |= SBS_RCVATMARK;
2882                         sohasoutofband(so);
2883                         tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA);
2884                 }
2885                 SOCKBUF_UNLOCK(&so->so_rcv);
2886                 /*
2887                  * Remove out of band data so doesn't get presented to user.
2888                  * This can happen independent of advancing the URG pointer,
2889                  * but if two URG's are pending at once, some out-of-band
2890                  * data may creep in... ick.
2891                  */
2892                 if (th->th_urp <= (u_long)tlen &&
2893                     !(so->so_options & SO_OOBINLINE)) {
2894                         /* hdr drop is delayed */
2895                         tcp_pulloutofband(so, th, m, drop_hdrlen);
2896                 }
2897         } else {
2898                 /*
2899                  * If no out of band data is expected,
2900                  * pull receive urgent pointer along
2901                  * with the receive window.
2902                  */
2903                 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up))
2904                         tp->rcv_up = tp->rcv_nxt;
2905         }
2906 dodata:                                                 /* XXX */
2907         INP_WLOCK_ASSERT(tp->t_inpcb);
2908
2909         /*
2910          * Process the segment text, merging it into the TCP sequencing queue,
2911          * and arranging for acknowledgment of receipt if necessary.
2912          * This process logically involves adjusting tp->rcv_wnd as data
2913          * is presented to the user (this happens in tcp_usrreq.c,
2914          * case PRU_RCVD).  If a FIN has already been received on this
2915          * connection then we just ignore the text.
2916          */
2917         if ((tlen || (thflags & TH_FIN)) &&
2918             TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2919                 tcp_seq save_start = th->th_seq;
2920                 m_adj(m, drop_hdrlen);  /* delayed header drop */
2921                 /*
2922                  * Insert segment which includes th into TCP reassembly queue
2923                  * with control block tp.  Set thflags to whether reassembly now
2924                  * includes a segment with FIN.  This handles the common case
2925                  * inline (segment is the next to be received on an established
2926                  * connection, and the queue is empty), avoiding linkage into
2927                  * and removal from the queue and repetition of various
2928                  * conversions.
2929                  * Set DELACK for segments received in order, but ack
2930                  * immediately when segments are out of order (so
2931                  * fast retransmit can work).
2932                  */
2933                 if (th->th_seq == tp->rcv_nxt &&
2934                     LIST_EMPTY(&tp->t_segq) &&
2935                     TCPS_HAVEESTABLISHED(tp->t_state)) {
2936                         if (DELAY_ACK(tp, tlen))
2937                                 tp->t_flags |= TF_DELACK;
2938                         else
2939                                 tp->t_flags |= TF_ACKNOW;
2940                         tp->rcv_nxt += tlen;
2941                         thflags = th->th_flags & TH_FIN;
2942                         TCPSTAT_INC(tcps_rcvpack);
2943                         TCPSTAT_ADD(tcps_rcvbyte, tlen);
2944                         SOCKBUF_LOCK(&so->so_rcv);
2945                         if (so->so_rcv.sb_state & SBS_CANTRCVMORE)
2946                                 m_freem(m);
2947                         else
2948                                 sbappendstream_locked(&so->so_rcv, m, 0);
2949                         /* NB: sorwakeup_locked() does an implicit unlock. */
2950                         sorwakeup_locked(so);
2951                 } else {
2952                         /*
2953                          * XXX: Due to the header drop above "th" is
2954                          * theoretically invalid by now.  Fortunately
2955                          * m_adj() doesn't actually frees any mbufs
2956                          * when trimming from the head.
2957                          */
2958                         thflags = tcp_reass(tp, th, &tlen, m);
2959                         tp->t_flags |= TF_ACKNOW;
2960                 }
2961                 if (tlen > 0 && (tp->t_flags & TF_SACK_PERMIT))
2962                         tcp_update_sack_list(tp, save_start, save_start + tlen);
2963 #if 0
2964                 /*
2965                  * Note the amount of data that peer has sent into
2966                  * our window, in order to estimate the sender's
2967                  * buffer size.
2968                  * XXX: Unused.
2969                  */
2970                 if (SEQ_GT(tp->rcv_adv, tp->rcv_nxt))
2971                         len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt);
2972                 else
2973                         len = so->so_rcv.sb_hiwat;
2974 #endif
2975         } else {
2976                 m_freem(m);
2977                 thflags &= ~TH_FIN;
2978         }
2979
2980         /*
2981          * If FIN is received ACK the FIN and let the user know
2982          * that the connection is closing.
2983          */
2984         if (thflags & TH_FIN) {
2985                 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) {
2986                         socantrcvmore(so);
2987                         /*
2988                          * If connection is half-synchronized
2989                          * (ie NEEDSYN flag on) then delay ACK,
2990                          * so it may be piggybacked when SYN is sent.
2991                          * Otherwise, since we received a FIN then no
2992                          * more input can be expected, send ACK now.
2993                          */
2994                         if (tp->t_flags & TF_NEEDSYN)
2995                                 tp->t_flags |= TF_DELACK;
2996                         else
2997                                 tp->t_flags |= TF_ACKNOW;
2998                         tp->rcv_nxt++;
2999                 }
3000                 switch (tp->t_state) {
3001
3002                 /*
3003                  * In SYN_RECEIVED and ESTABLISHED STATES
3004                  * enter the CLOSE_WAIT state.
3005                  */
3006                 case TCPS_SYN_RECEIVED:
3007                         tp->t_starttime = ticks;
3008                         /* FALLTHROUGH */
3009                 case TCPS_ESTABLISHED:
3010                         tcp_state_change(tp, TCPS_CLOSE_WAIT);
3011                         break;
3012
3013                 /*
3014                  * If still in FIN_WAIT_1 STATE FIN has not been acked so
3015                  * enter the CLOSING state.
3016                  */
3017                 case TCPS_FIN_WAIT_1:
3018                         tcp_state_change(tp, TCPS_CLOSING);
3019                         break;
3020
3021                 /*
3022                  * In FIN_WAIT_2 state enter the TIME_WAIT state,
3023                  * starting the time-wait timer, turning off the other
3024                  * standard timers.
3025                  */
3026                 case TCPS_FIN_WAIT_2:
3027                         INP_INFO_RLOCK_ASSERT(&V_tcbinfo);
3028                         KASSERT(ti_locked == TI_RLOCKED, ("%s: dodata "
3029                             "TCP_FIN_WAIT_2 ti_locked: %d", __func__,
3030                             ti_locked));
3031
3032                         tcp_twstart(tp);
3033                         INP_INFO_RUNLOCK(&V_tcbinfo);
3034                         return;
3035                 }
3036         }
3037         if (ti_locked == TI_RLOCKED)
3038                 INP_INFO_RUNLOCK(&V_tcbinfo);
3039         ti_locked = TI_UNLOCKED;
3040
3041 #ifdef TCPDEBUG
3042         if (so->so_options & SO_DEBUG)
3043                 tcp_trace(TA_INPUT, ostate, tp, (void *)tcp_saveipgen,
3044                           &tcp_savetcp, 0);
3045 #endif
3046         TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
3047
3048         /*
3049          * Return any desired output.
3050          */
3051         if (needoutput || (tp->t_flags & TF_ACKNOW))
3052                 (void) tcp_output(tp);
3053
3054 check_delack:
3055         KASSERT(ti_locked == TI_UNLOCKED, ("%s: check_delack ti_locked %d",
3056             __func__, ti_locked));
3057         INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3058         INP_WLOCK_ASSERT(tp->t_inpcb);
3059
3060         if (tp->t_flags & TF_DELACK) {
3061                 tp->t_flags &= ~TF_DELACK;
3062                 tcp_timer_activate(tp, TT_DELACK, tcp_delacktime);
3063         }
3064         INP_WUNLOCK(tp->t_inpcb);
3065         return;
3066
3067 dropafterack:
3068         /*
3069          * Generate an ACK dropping incoming segment if it occupies
3070          * sequence space, where the ACK reflects our state.
3071          *
3072          * We can now skip the test for the RST flag since all
3073          * paths to this code happen after packets containing
3074          * RST have been dropped.
3075          *
3076          * In the SYN-RECEIVED state, don't send an ACK unless the
3077          * segment we received passes the SYN-RECEIVED ACK test.
3078          * If it fails send a RST.  This breaks the loop in the
3079          * "LAND" DoS attack, and also prevents an ACK storm
3080          * between two listening ports that have been sent forged
3081          * SYN segments, each with the source address of the other.
3082          */
3083         if (tp->t_state == TCPS_SYN_RECEIVED && (thflags & TH_ACK) &&
3084             (SEQ_GT(tp->snd_una, th->th_ack) ||
3085              SEQ_GT(th->th_ack, tp->snd_max)) ) {
3086                 rstreason = BANDLIM_RST_OPENPORT;
3087                 goto dropwithreset;
3088         }
3089 #ifdef TCPDEBUG
3090         if (so->so_options & SO_DEBUG)
3091                 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3092                           &tcp_savetcp, 0);
3093 #endif
3094         TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
3095         if (ti_locked == TI_RLOCKED)
3096                 INP_INFO_RUNLOCK(&V_tcbinfo);
3097         ti_locked = TI_UNLOCKED;
3098
3099         tp->t_flags |= TF_ACKNOW;
3100         (void) tcp_output(tp);
3101         INP_WUNLOCK(tp->t_inpcb);
3102         m_freem(m);
3103         return;
3104
3105 dropwithreset:
3106         if (ti_locked == TI_RLOCKED)
3107                 INP_INFO_RUNLOCK(&V_tcbinfo);
3108         ti_locked = TI_UNLOCKED;
3109
3110         if (tp != NULL) {
3111                 tcp_dropwithreset(m, th, tp, tlen, rstreason);
3112                 INP_WUNLOCK(tp->t_inpcb);
3113         } else
3114                 tcp_dropwithreset(m, th, NULL, tlen, rstreason);
3115         return;
3116
3117 drop:
3118         if (ti_locked == TI_RLOCKED) {
3119                 INP_INFO_RUNLOCK(&V_tcbinfo);
3120                 ti_locked = TI_UNLOCKED;
3121         }
3122 #ifdef INVARIANTS
3123         else
3124                 INP_INFO_UNLOCK_ASSERT(&V_tcbinfo);
3125 #endif
3126
3127         /*
3128          * Drop space held by incoming segment and return.
3129          */
3130 #ifdef TCPDEBUG
3131         if (tp == NULL || (tp->t_inpcb->inp_socket->so_options & SO_DEBUG))
3132                 tcp_trace(TA_DROP, ostate, tp, (void *)tcp_saveipgen,
3133                           &tcp_savetcp, 0);
3134 #endif
3135         TCP_PROBE3(debug__input, tp, th, mtod(m, const char *));
3136         if (tp != NULL)
3137                 INP_WUNLOCK(tp->t_inpcb);
3138         m_freem(m);
3139 }
3140
3141 /*
3142  * Issue RST and make ACK acceptable to originator of segment.
3143  * The mbuf must still include the original packet header.
3144  * tp may be NULL.
3145  */
3146 static void
3147 tcp_dropwithreset(struct mbuf *m, struct tcphdr *th, struct tcpcb *tp,
3148     int tlen, int rstreason)
3149 {
3150 #ifdef INET
3151         struct ip *ip;
3152 #endif
3153 #ifdef INET6
3154         struct ip6_hdr *ip6;
3155 #endif
3156
3157         if (tp != NULL) {
3158                 INP_WLOCK_ASSERT(tp->t_inpcb);
3159         }
3160
3161         /* Don't bother if destination was broadcast/multicast. */
3162         if ((th->th_flags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST))
3163                 goto drop;
3164 #ifdef INET6
3165         if (mtod(m, struct ip *)->ip_v == 6) {
3166                 ip6 = mtod(m, struct ip6_hdr *);
3167                 if (IN6_IS_ADDR_MULTICAST(&ip6->ip6_dst) ||
3168                     IN6_IS_ADDR_MULTICAST(&ip6->ip6_src))
3169                         goto drop;
3170                 /* IPv6 anycast check is done at tcp6_input() */
3171         }
3172 #endif
3173 #if defined(INET) && defined(INET6)
3174         else
3175 #endif
3176 #ifdef INET
3177         {
3178                 ip = mtod(m, struct ip *);
3179                 if (IN_MULTICAST(ntohl(ip->ip_dst.s_addr)) ||
3180                     IN_MULTICAST(ntohl(ip->ip_src.s_addr)) ||
3181                     ip->ip_src.s_addr == htonl(INADDR_BROADCAST) ||
3182                     in_broadcast(ip->ip_dst, m->m_pkthdr.rcvif))
3183                         goto drop;
3184         }
3185 #endif
3186
3187         /* Perform bandwidth limiting. */
3188         if (badport_bandlim(rstreason) < 0)
3189                 goto drop;
3190
3191         /* tcp_respond consumes the mbuf chain. */
3192         if (th->th_flags & TH_ACK) {
3193                 tcp_respond(tp, mtod(m, void *), th, m, (tcp_seq)0,
3194                     th->th_ack, TH_RST);
3195         } else {
3196                 if (th->th_flags & TH_SYN)
3197                         tlen++;
3198                 tcp_respond(tp, mtod(m, void *), th, m, th->th_seq+tlen,
3199                     (tcp_seq)0, TH_RST|TH_ACK);
3200         }
3201         return;
3202 drop:
3203         m_freem(m);
3204 }
3205
3206 /*
3207  * Parse TCP options and place in tcpopt.
3208  */
3209 static void
3210 tcp_dooptions(struct tcpopt *to, u_char *cp, int cnt, int flags)
3211 {
3212         int opt, optlen;
3213
3214         to->to_flags = 0;
3215         for (; cnt > 0; cnt -= optlen, cp += optlen) {
3216                 opt = cp[0];
3217                 if (opt == TCPOPT_EOL)
3218                         break;
3219                 if (opt == TCPOPT_NOP)
3220                         optlen = 1;
3221                 else {
3222                         if (cnt < 2)
3223                                 break;
3224                         optlen = cp[1];
3225                         if (optlen < 2 || optlen > cnt)
3226                                 break;
3227                 }
3228                 switch (opt) {
3229                 case TCPOPT_MAXSEG:
3230                         if (optlen != TCPOLEN_MAXSEG)
3231                                 continue;
3232                         if (!(flags & TO_SYN))
3233                                 continue;
3234                         to->to_flags |= TOF_MSS;
3235                         bcopy((char *)cp + 2,
3236                             (char *)&to->to_mss, sizeof(to->to_mss));
3237                         to->to_mss = ntohs(to->to_mss);
3238                         break;
3239                 case TCPOPT_WINDOW:
3240                         if (optlen != TCPOLEN_WINDOW)
3241                                 continue;
3242                         if (!(flags & TO_SYN))
3243                                 continue;
3244                         to->to_flags |= TOF_SCALE;
3245                         to->to_wscale = min(cp[2], TCP_MAX_WINSHIFT);
3246                         break;
3247                 case TCPOPT_TIMESTAMP:
3248                         if (optlen != TCPOLEN_TIMESTAMP)
3249                                 continue;
3250                         to->to_flags |= TOF_TS;
3251                         bcopy((char *)cp + 2,
3252                             (char *)&to->to_tsval, sizeof(to->to_tsval));
3253                         to->to_tsval = ntohl(to->to_tsval);
3254                         bcopy((char *)cp + 6,
3255                             (char *)&to->to_tsecr, sizeof(to->to_tsecr));
3256                         to->to_tsecr = ntohl(to->to_tsecr);
3257                         break;
3258 #ifdef TCP_SIGNATURE
3259                 /*
3260                  * XXX In order to reply to a host which has set the
3261                  * TCP_SIGNATURE option in its initial SYN, we have to
3262                  * record the fact that the option was observed here
3263                  * for the syncache code to perform the correct response.
3264                  */
3265                 case TCPOPT_SIGNATURE:
3266                         if (optlen != TCPOLEN_SIGNATURE)
3267                                 continue;
3268                         to->to_flags |= TOF_SIGNATURE;
3269                         to->to_signature = cp + 2;
3270                         break;
3271 #endif
3272                 case TCPOPT_SACK_PERMITTED:
3273                         if (optlen != TCPOLEN_SACK_PERMITTED)
3274                                 continue;
3275                         if (!(flags & TO_SYN))
3276                                 continue;
3277                         if (!V_tcp_do_sack)
3278                                 continue;
3279                         to->to_flags |= TOF_SACKPERM;
3280                         break;
3281                 case TCPOPT_SACK:
3282                         if (optlen <= 2 || (optlen - 2) % TCPOLEN_SACK != 0)
3283                                 continue;
3284                         if (flags & TO_SYN)
3285                                 continue;
3286                         to->to_flags |= TOF_SACK;
3287                         to->to_nsacks = (optlen - 2) / TCPOLEN_SACK;
3288                         to->to_sacks = cp + 2;
3289                         TCPSTAT_INC(tcps_sack_rcv_blocks);
3290                         break;
3291                 default:
3292                         continue;
3293                 }
3294         }
3295 }
3296
3297 /*
3298  * Pull out of band byte out of a segment so
3299  * it doesn't appear in the user's data queue.
3300  * It is still reflected in the segment length for
3301  * sequencing purposes.
3302  */
3303 static void
3304 tcp_pulloutofband(struct socket *so, struct tcphdr *th, struct mbuf *m,
3305     int off)
3306 {
3307         int cnt = off + th->th_urp - 1;
3308
3309         while (cnt >= 0) {
3310                 if (m->m_len > cnt) {
3311                         char *cp = mtod(m, caddr_t) + cnt;
3312                         struct tcpcb *tp = sototcpcb(so);
3313
3314                         INP_WLOCK_ASSERT(tp->t_inpcb);
3315
3316                         tp->t_iobc = *cp;
3317                         tp->t_oobflags |= TCPOOB_HAVEDATA;
3318                         bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1));
3319                         m->m_len--;
3320                         if (m->m_flags & M_PKTHDR)
3321                                 m->m_pkthdr.len--;
3322                         return;
3323                 }
3324                 cnt -= m->m_len;
3325                 m = m->m_next;
3326                 if (m == NULL)
3327                         break;
3328         }
3329         panic("tcp_pulloutofband");
3330 }
3331
3332 /*
3333  * Collect new round-trip time estimate
3334  * and update averages and current timeout.
3335  */
3336 static void
3337 tcp_xmit_timer(struct tcpcb *tp, int rtt)
3338 {
3339         int delta;
3340
3341         INP_WLOCK_ASSERT(tp->t_inpcb);
3342
3343         TCPSTAT_INC(tcps_rttupdated);
3344         tp->t_rttupdated++;
3345         if (tp->t_srtt != 0) {
3346                 /*
3347                  * srtt is stored as fixed point with 5 bits after the
3348                  * binary point (i.e., scaled by 8).  The following magic
3349                  * is equivalent to the smoothing algorithm in rfc793 with
3350                  * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed
3351                  * point).  Adjust rtt to origin 0.
3352                  */
3353                 delta = ((rtt - 1) << TCP_DELTA_SHIFT)
3354                         - (tp->t_srtt >> (TCP_RTT_SHIFT - TCP_DELTA_SHIFT));
3355
3356                 if ((tp->t_srtt += delta) <= 0)
3357                         tp->t_srtt = 1;
3358
3359                 /*
3360                  * We accumulate a smoothed rtt variance (actually, a
3361                  * smoothed mean difference), then set the retransmit
3362                  * timer to smoothed rtt + 4 times the smoothed variance.
3363                  * rttvar is stored as fixed point with 4 bits after the
3364                  * binary point (scaled by 16).  The following is
3365                  * equivalent to rfc793 smoothing with an alpha of .75
3366                  * (rttvar = rttvar*3/4 + |delta| / 4).  This replaces
3367                  * rfc793's wired-in beta.
3368                  */
3369                 if (delta < 0)
3370                         delta = -delta;
3371                 delta -= tp->t_rttvar >> (TCP_RTTVAR_SHIFT - TCP_DELTA_SHIFT);
3372                 if ((tp->t_rttvar += delta) <= 0)
3373                         tp->t_rttvar = 1;
3374                 if (tp->t_rttbest > tp->t_srtt + tp->t_rttvar)
3375                     tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3376         } else {
3377                 /*
3378                  * No rtt measurement yet - use the unsmoothed rtt.
3379                  * Set the variance to half the rtt (so our first
3380                  * retransmit happens at 3*rtt).
3381                  */
3382                 tp->t_srtt = rtt << TCP_RTT_SHIFT;
3383                 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1);
3384                 tp->t_rttbest = tp->t_srtt + tp->t_rttvar;
3385         }
3386         tp->t_rtttime = 0;
3387         tp->t_rxtshift = 0;
3388
3389         /*
3390          * the retransmit should happen at rtt + 4 * rttvar.
3391          * Because of the way we do the smoothing, srtt and rttvar
3392          * will each average +1/2 tick of bias.  When we compute
3393          * the retransmit timer, we want 1/2 tick of rounding and
3394          * 1 extra tick because of +-1/2 tick uncertainty in the
3395          * firing of the timer.  The bias will give us exactly the
3396          * 1.5 tick we need.  But, because the bias is
3397          * statistical, we have to test that we don't drop below
3398          * the minimum feasible timer (which is 2 ticks).
3399          */
3400         TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp),
3401                       max(tp->t_rttmin, rtt + 2), TCPTV_REXMTMAX);
3402
3403         /*
3404          * We received an ack for a packet that wasn't retransmitted;
3405          * it is probably safe to discard any error indications we've
3406          * received recently.  This isn't quite right, but close enough
3407          * for now (a route might have failed after we sent a segment,
3408          * and the return path might not be symmetrical).
3409          */
3410         tp->t_softerror = 0;
3411 }
3412
3413 /*
3414  * Determine a reasonable value for maxseg size.
3415  * If the route is known, check route for mtu.
3416  * If none, use an mss that can be handled on the outgoing interface
3417  * without forcing IP to fragment.  If no route is found, route has no mtu,
3418  * or the destination isn't local, use a default, hopefully conservative
3419  * size (usually 512 or the default IP max size, but no more than the mtu
3420  * of the interface), as we can't discover anything about intervening
3421  * gateways or networks.  We also initialize the congestion/slow start
3422  * window to be a single segment if the destination isn't local.
3423  * While looking at the routing entry, we also initialize other path-dependent
3424  * parameters from pre-set or cached values in the routing entry.
3425  *
3426  * Also take into account the space needed for options that we
3427  * send regularly.  Make maxseg shorter by that amount to assure
3428  * that we can send maxseg amount of data even when the options
3429  * are present.  Store the upper limit of the length of options plus
3430  * data in maxopd.
3431  *
3432  * NOTE that this routine is only called when we process an incoming
3433  * segment, or an ICMP need fragmentation datagram. Outgoing SYN/ACK MSS
3434  * settings are handled in tcp_mssopt().
3435  */
3436 void
3437 tcp_mss_update(struct tcpcb *tp, int offer, int mtuoffer,
3438     struct hc_metrics_lite *metricptr, struct tcp_ifcap *cap)
3439 {
3440         int mss = 0;
3441         u_long maxmtu = 0;
3442         struct inpcb *inp = tp->t_inpcb;
3443         struct hc_metrics_lite metrics;
3444         int origoffer;
3445 #ifdef INET6
3446         int isipv6 = ((inp->inp_vflag & INP_IPV6) != 0) ? 1 : 0;
3447         size_t min_protoh = isipv6 ?
3448                             sizeof (struct ip6_hdr) + sizeof (struct tcphdr) :
3449                             sizeof (struct tcpiphdr);
3450 #else
3451         const size_t min_protoh = sizeof(struct tcpiphdr);
3452 #endif
3453
3454         INP_WLOCK_ASSERT(tp->t_inpcb);
3455
3456         if (mtuoffer != -1) {
3457                 KASSERT(offer == -1, ("%s: conflict", __func__));
3458                 offer = mtuoffer - min_protoh;
3459         }
3460         origoffer = offer;
3461
3462         /* Initialize. */
3463 #ifdef INET6
3464         if (isipv6) {
3465                 maxmtu = tcp_maxmtu6(&inp->inp_inc, cap);
3466                 tp->t_maxopd = tp->t_maxseg = V_tcp_v6mssdflt;
3467         }
3468 #endif
3469 #if defined(INET) && defined(INET6)
3470         else
3471 #endif
3472 #ifdef INET
3473         {
3474                 maxmtu = tcp_maxmtu(&inp->inp_inc, cap);
3475                 tp->t_maxopd = tp->t_maxseg = V_tcp_mssdflt;
3476         }
3477 #endif
3478
3479         /*
3480          * No route to sender, stay with default mss and return.
3481          */
3482         if (maxmtu == 0) {
3483                 /*
3484                  * In case we return early we need to initialize metrics
3485                  * to a defined state as tcp_hc_get() would do for us
3486                  * if there was no cache hit.
3487                  */
3488                 if (metricptr != NULL)
3489                         bzero(metricptr, sizeof(struct hc_metrics_lite));
3490                 return;
3491         }
3492
3493         /* What have we got? */
3494         switch (offer) {
3495                 case 0:
3496                         /*
3497                          * Offer == 0 means that there was no MSS on the SYN
3498                          * segment, in this case we use tcp_mssdflt as
3499                          * already assigned to t_maxopd above.
3500                          */
3501                         offer = tp->t_maxopd;
3502                         break;
3503
3504                 case -1:
3505                         /*
3506                          * Offer == -1 means that we didn't receive SYN yet.
3507                          */
3508                         /* FALLTHROUGH */
3509
3510                 default:
3511                         /*
3512                          * Prevent DoS attack with too small MSS. Round up
3513                          * to at least minmss.
3514                          */
3515                         offer = max(offer, V_tcp_minmss);
3516         }
3517
3518         /*
3519          * rmx information is now retrieved from tcp_hostcache.
3520          */
3521         tcp_hc_get(&inp->inp_inc, &metrics);
3522         if (metricptr != NULL)
3523                 bcopy(&metrics, metricptr, sizeof(struct hc_metrics_lite));
3524
3525         /*
3526          * If there's a discovered mtu in tcp hostcache, use it.
3527          * Else, use the link mtu.
3528          */
3529         if (metrics.rmx_mtu)
3530                 mss = min(metrics.rmx_mtu, maxmtu) - min_protoh;
3531         else {
3532 #ifdef INET6
3533                 if (isipv6) {
3534                         mss = maxmtu - min_protoh;
3535                         if (!V_path_mtu_discovery &&
3536                             !in6_localaddr(&inp->in6p_faddr))
3537                                 mss = min(mss, V_tcp_v6mssdflt);
3538                 }
3539 #endif
3540 #if defined(INET) && defined(INET6)
3541                 else
3542 #endif
3543 #ifdef INET
3544                 {
3545                         mss = maxmtu - min_protoh;
3546                         if (!V_path_mtu_discovery &&
3547                             !in_localaddr(inp->inp_faddr))
3548                                 mss = min(mss, V_tcp_mssdflt);
3549                 }
3550 #endif
3551                 /*
3552                  * XXX - The above conditional (mss = maxmtu - min_protoh)
3553                  * probably violates the TCP spec.
3554                  * The problem is that, since we don't know the
3555                  * other end's MSS, we are supposed to use a conservative
3556                  * default.  But, if we do that, then MTU discovery will
3557                  * never actually take place, because the conservative
3558                  * default is much less than the MTUs typically seen
3559                  * on the Internet today.  For the moment, we'll sweep
3560                  * this under the carpet.
3561                  *
3562                  * The conservative default might not actually be a problem
3563                  * if the only case this occurs is when sending an initial
3564                  * SYN with options and data to a host we've never talked
3565                  * to before.  Then, they will reply with an MSS value which
3566                  * will get recorded and the new parameters should get
3567                  * recomputed.  For Further Study.
3568                  */
3569         }
3570         mss = min(mss, offer);
3571
3572         /*
3573          * Sanity check: make sure that maxopd will be large
3574          * enough to allow some data on segments even if the
3575          * all the option space is used (40bytes).  Otherwise
3576          * funny things may happen in tcp_output.
3577          */
3578         mss = max(mss, 64);
3579
3580         /*
3581          * maxopd stores the maximum length of data AND options
3582          * in a segment; maxseg is the amount of data in a normal
3583          * segment.  We need to store this value (maxopd) apart
3584          * from maxseg, because now every segment carries options
3585          * and thus we normally have somewhat less data in segments.
3586          */
3587         tp->t_maxopd = mss;
3588
3589         /*
3590          * origoffer==-1 indicates that no segments were received yet.
3591          * In this case we just guess.
3592          */
3593         if ((tp->t_flags & (TF_REQ_TSTMP|TF_NOOPT)) == TF_REQ_TSTMP &&
3594             (origoffer == -1 ||
3595              (tp->t_flags & TF_RCVD_TSTMP) == TF_RCVD_TSTMP))
3596                 mss -= TCPOLEN_TSTAMP_APPA;
3597
3598         tp->t_maxseg = mss;
3599 }
3600
3601 void
3602 tcp_mss(struct tcpcb *tp, int offer)
3603 {
3604         int mss;
3605         u_long bufsize;
3606         struct inpcb *inp;
3607         struct socket *so;
3608         struct hc_metrics_lite metrics;
3609         struct tcp_ifcap cap;
3610
3611         KASSERT(tp != NULL, ("%s: tp == NULL", __func__));
3612
3613         bzero(&cap, sizeof(cap));
3614         tcp_mss_update(tp, offer, -1, &metrics, &cap);
3615
3616         mss = tp->t_maxseg;
3617         inp = tp->t_inpcb;
3618
3619         /*
3620          * If there's a pipesize, change the socket buffer to that size,
3621          * don't change if sb_hiwat is different than default (then it
3622          * has been changed on purpose with setsockopt).
3623          * Make the socket buffers an integral number of mss units;
3624          * if the mss is larger than the socket buffer, decrease the mss.
3625          */
3626         so = inp->inp_socket;
3627         SOCKBUF_LOCK(&so->so_snd);
3628         if ((so->so_snd.sb_hiwat == V_tcp_sendspace) && metrics.rmx_sendpipe)
3629                 bufsize = metrics.rmx_sendpipe;
3630         else
3631                 bufsize = so->so_snd.sb_hiwat;
3632         if (bufsize < mss)
3633                 mss = bufsize;
3634         else {
3635                 bufsize = roundup(bufsize, mss);
3636                 if (bufsize > sb_max)
3637                         bufsize = sb_max;
3638                 if (bufsize > so->so_snd.sb_hiwat)
3639                         (void)sbreserve_locked(&so->so_snd, bufsize, so, NULL);
3640         }
3641         SOCKBUF_UNLOCK(&so->so_snd);
3642         tp->t_maxseg = mss;
3643
3644         SOCKBUF_LOCK(&so->so_rcv);
3645         if ((so->so_rcv.sb_hiwat == V_tcp_recvspace) && metrics.rmx_recvpipe)
3646                 bufsize = metrics.rmx_recvpipe;
3647         else
3648                 bufsize = so->so_rcv.sb_hiwat;
3649         if (bufsize > mss) {
3650                 bufsize = roundup(bufsize, mss);
3651                 if (bufsize > sb_max)
3652                         bufsize = sb_max;
3653                 if (bufsize > so->so_rcv.sb_hiwat)
3654                         (void)sbreserve_locked(&so->so_rcv, bufsize, so, NULL);
3655         }
3656         SOCKBUF_UNLOCK(&so->so_rcv);
3657
3658         /* Check the interface for TSO capabilities. */
3659         if (cap.ifcap & CSUM_TSO) {
3660                 tp->t_flags |= TF_TSO;
3661                 tp->t_tsomax = cap.tsomax;
3662                 tp->t_tsomaxsegcount = cap.tsomaxsegcount;
3663                 tp->t_tsomaxsegsize = cap.tsomaxsegsize;
3664         }
3665 }
3666
3667 /*
3668  * Determine the MSS option to send on an outgoing SYN.
3669  */
3670 int
3671 tcp_mssopt(struct in_conninfo *inc)
3672 {
3673         int mss = 0;
3674         u_long maxmtu = 0;
3675         u_long thcmtu = 0;
3676         size_t min_protoh;
3677
3678         KASSERT(inc != NULL, ("tcp_mssopt with NULL in_conninfo pointer"));
3679
3680 #ifdef INET6
3681         if (inc->inc_flags & INC_ISIPV6) {
3682                 mss = V_tcp_v6mssdflt;
3683                 maxmtu = tcp_maxmtu6(inc, NULL);
3684                 min_protoh = sizeof(struct ip6_hdr) + sizeof(struct tcphdr);
3685         }
3686 #endif
3687 #if defined(INET) && defined(INET6)
3688         else
3689 #endif
3690 #ifdef INET
3691         {
3692                 mss = V_tcp_mssdflt;
3693                 maxmtu = tcp_maxmtu(inc, NULL);
3694                 min_protoh = sizeof(struct tcpiphdr);
3695         }
3696 #endif
3697 #if defined(INET6) || defined(INET)
3698         thcmtu = tcp_hc_getmtu(inc); /* IPv4 and IPv6 */
3699 #endif
3700
3701         if (maxmtu && thcmtu)
3702                 mss = min(maxmtu, thcmtu) - min_protoh;
3703         else if (maxmtu || thcmtu)
3704                 mss = max(maxmtu, thcmtu) - min_protoh;
3705
3706         return (mss);
3707 }
3708
3709
3710 /*
3711  * On a partial ack arrives, force the retransmission of the
3712  * next unacknowledged segment.  Do not clear tp->t_dupacks.
3713  * By setting snd_nxt to ti_ack, this forces retransmission timer to
3714  * be started again.
3715  */
3716 static void
3717 tcp_newreno_partial_ack(struct tcpcb *tp, struct tcphdr *th)
3718 {
3719         tcp_seq onxt = tp->snd_nxt;
3720         u_long  ocwnd = tp->snd_cwnd;
3721
3722         INP_WLOCK_ASSERT(tp->t_inpcb);
3723
3724         tcp_timer_activate(tp, TT_REXMT, 0);
3725         tp->t_rtttime = 0;
3726         tp->snd_nxt = th->th_ack;
3727         /*
3728          * Set snd_cwnd to one segment beyond acknowledged offset.
3729          * (tp->snd_una has not yet been updated when this function is called.)
3730          */
3731         tp->snd_cwnd = tp->t_maxseg + BYTES_THIS_ACK(tp, th);
3732         tp->t_flags |= TF_ACKNOW;
3733         (void) tcp_output(tp);
3734         tp->snd_cwnd = ocwnd;
3735         if (SEQ_GT(onxt, tp->snd_nxt))
3736                 tp->snd_nxt = onxt;
3737         /*
3738          * Partial window deflation.  Relies on fact that tp->snd_una
3739          * not updated yet.
3740          */
3741         if (tp->snd_cwnd > BYTES_THIS_ACK(tp, th))
3742                 tp->snd_cwnd -= BYTES_THIS_ACK(tp, th);
3743         else
3744                 tp->snd_cwnd = 0;
3745         tp->snd_cwnd += tp->t_maxseg;
3746 }
3747
3748 int
3749 tcp_compute_pipe(struct tcpcb *tp)
3750 {
3751         return (tp->snd_max - tp->snd_una +
3752                 tp->sackhint.sack_bytes_rexmit -
3753                 tp->sackhint.sacked_bytes);
3754 }