1 /*- 2 * SPDX-License-Identifier: BSD-3-Clause 3 * 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 5 * The Regents of the University of California. All rights reserved. 6 * 7 * Redistribution and use in source and binary forms, with or without 8 * modification, are permitted provided that the following conditions 9 * are met: 10 * 1. Redistributions of source code must retain the above copyright 11 * notice, this list of conditions and the following disclaimer. 12 * 2. Redistributions in binary form must reproduce the above copyright 13 * notice, this list of conditions and the following disclaimer in the 14 * documentation and/or other materials provided with the distribution. 15 * 3. Neither the name of the University nor the names of its contributors 16 * may be used to endorse or promote products derived from this software 17 * without specific prior written permission. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 20 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 23 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 24 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 25 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 26 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 27 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 28 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 29 * SUCH DAMAGE. 30 * 31 * @(#)tcp_subr.c 8.2 (Berkeley) 5/24/95 32 */ 33 34 #include <sys/cdefs.h> 35 __FBSDID("$FreeBSD$"); 36 37 #include "opt_inet.h" 38 #include "opt_inet6.h" 39 #include "opt_ipsec.h" 40 41 #include <sys/param.h> 42 #include <sys/systm.h> 43 #include <sys/callout.h> 44 #include <sys/kernel.h> 45 #include <sys/sysctl.h> 46 #include <sys/malloc.h> 47 #include <sys/mbuf.h> 48 #include <sys/priv.h> 49 #include <sys/proc.h> 50 #include <sys/socket.h> 51 #include <sys/socketvar.h> 52 #include <sys/syslog.h> 53 #include <sys/protosw.h> 54 #include <sys/random.h> 55 56 #include <vm/uma.h> 57 58 #include <net/route.h> 59 #include <net/if.h> 60 #include <net/if_var.h> 61 #include <net/vnet.h> 62 63 #include <netinet/in.h> 64 #include <netinet/in_kdtrace.h> 65 #include <netinet/in_pcb.h> 66 #include <netinet/in_systm.h> 67 #include <netinet/in_var.h> 68 #include <netinet/ip.h> 69 #include <netinet/ip_icmp.h> 70 #include <netinet/ip_var.h> 71 #ifdef INET6 72 #include <netinet/ip6.h> 73 #include <netinet6/in6_pcb.h> 74 #include <netinet6/ip6_var.h> 75 #include <netinet6/scope6_var.h> 76 #include <netinet6/nd6.h> 77 #endif 78 #include <netinet/tcp.h> 79 #include <netinet/tcp_fsm.h> 80 #include <netinet/tcp_seq.h> 81 #include <netinet/tcp_timer.h> 82 #include <netinet/tcp_var.h> 83 #include <netinet/tcp_hpts.h> 84 #include <netinet/tcpip.h> 85 86 #include <netinet/udp.h> 87 #include <netinet/udp_var.h> 88 89 #include <netipsec/ipsec_support.h> 90 91 #include <machine/in_cksum.h> 92 93 #include <security/mac/mac_framework.h> 94 95 VNET_DEFINE_STATIC(bool, nolocaltimewait) = true; 96 #define V_nolocaltimewait VNET(nolocaltimewait) 97 SYSCTL_BOOL(_net_inet_tcp, OID_AUTO, nolocaltimewait, 98 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(nolocaltimewait), true, 99 "Do not create TCP TIME_WAIT state for local connections"); 100 101 /* 102 * Move a TCP connection into TIME_WAIT state. 103 * inp is locked, and is unlocked before returning. 104 * 105 * This function used to free tcpcb and allocate a compressed TCP time-wait 106 * structure tcptw. This served well for 20 years but is no longer relevant 107 * on modern machines in the modern internet. However, the function remains 108 * so that TCP stacks require less modification and we don't burn the bridge 109 * to go back to using compressed time-wait. 110 */ 111 void 112 tcp_twstart(struct tcpcb *tp) 113 { 114 struct inpcb *inp = tptoinpcb(tp); 115 #ifdef INET6 116 bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 117 #endif 118 119 NET_EPOCH_ASSERT(); 120 INP_WLOCK_ASSERT(inp); 121 122 /* A dropped inp should never transition to TIME_WAIT state. */ 123 KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: " 124 "(inp->inp_flags & INP_DROPPED) != 0")); 125 126 tcp_state_change(tp, TCPS_TIME_WAIT); 127 soisdisconnected(inp->inp_socket); 128 129 if (tp->t_flags & TF_ACKNOW) 130 tcp_output(tp); 131 132 if (V_nolocaltimewait && ( 133 #ifdef INET6 134 isipv6 ? in6_localaddr(&inp->in6p_faddr) : 135 #endif 136 #ifdef INET 137 in_localip(inp->inp_faddr) 138 #else 139 false 140 #endif 141 )) { 142 if ((tp = tcp_close(tp)) != NULL) 143 INP_WUNLOCK(inp); 144 return; 145 } 146 147 tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl); 148 INP_WUNLOCK(inp); 149 } 150 151 /* 152 * Returns true if the TIME_WAIT state was killed and we should start over, 153 * looking for a pcb in the listen state. Otherwise returns false and frees 154 * the mbuf. 155 * 156 * For pure SYN-segments the PCB shall be read-locked and the tcpopt pointer 157 * may be NULL. For the rest write-lock and valid tcpopt. 158 */ 159 bool 160 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th, 161 struct mbuf *m, int tlen) 162 { 163 struct tcpcb *tp = intotcpcb(inp); 164 char *s; 165 int thflags; 166 tcp_seq seq; 167 168 NET_EPOCH_ASSERT(); 169 INP_LOCK_ASSERT(inp); 170 171 thflags = tcp_get_flags(th); 172 #ifdef INVARIANTS 173 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) 174 INP_RLOCK_ASSERT(inp); 175 else { 176 INP_WLOCK_ASSERT(inp); 177 KASSERT(to != NULL, 178 ("%s: called without options on a non-SYN segment", 179 __func__)); 180 } 181 #endif 182 183 /* 184 * NOTE: for FIN_WAIT_2 (to be added later), 185 * must validate sequence number before accepting RST 186 */ 187 188 /* 189 * If the segment contains RST: 190 * Drop the segment - see Stevens, vol. 2, p. 964 and 191 * RFC 1337. 192 */ 193 if (thflags & TH_RST) 194 goto drop; 195 196 #if 0 197 /* PAWS not needed at the moment */ 198 /* 199 * RFC 1323 PAWS: If we have a timestamp reply on this segment 200 * and it's less than ts_recent, drop it. 201 */ 202 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 203 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 204 if ((thflags & TH_ACK) == 0) 205 goto drop; 206 goto ack; 207 } 208 /* 209 * ts_recent is never updated because we never accept new segments. 210 */ 211 #endif 212 213 /* Honor the drop_synfin sysctl variable. */ 214 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 215 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) { 216 log(LOG_DEBUG, "%s; %s: " 217 "SYN|FIN segment ignored (based on " 218 "sysctl setting)\n", s, __func__); 219 free(s, M_TCPLOG); 220 } 221 goto drop; 222 } 223 224 /* 225 * If a new connection request is received 226 * while in TIME_WAIT, drop the old connection 227 * and start over if the sequence numbers 228 * are above the previous ones. 229 * Allow UDP port number changes in this case. 230 */ 231 if (((thflags & (TH_SYN | TH_ACK)) == TH_SYN) && 232 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 233 /* 234 * In case we can't upgrade our lock just pretend we have 235 * lost this packet. 236 */ 237 if (INP_TRY_UPGRADE(inp) == 0) 238 goto drop; 239 if ((tp = tcp_close(tp)) != NULL) 240 INP_WUNLOCK(inp); 241 TCPSTAT_INC(tcps_tw_recycles); 242 return (true); 243 } 244 245 /* 246 * Send RST if UDP port numbers don't match 247 */ 248 if (tp->t_port != m->m_pkthdr.tcp_tun_port) { 249 if (tcp_get_flags(th) & TH_ACK) { 250 tcp_respond(tp, mtod(m, void *), th, m, 251 (tcp_seq)0, th->th_ack, TH_RST); 252 } else { 253 if (tcp_get_flags(th) & TH_SYN) 254 tlen++; 255 if (tcp_get_flags(th) & TH_FIN) 256 tlen++; 257 tcp_respond(tp, mtod(m, void *), th, m, 258 th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK); 259 } 260 INP_UNLOCK(inp); 261 TCPSTAT_INC(tcps_tw_resets); 262 return (false); 263 } 264 265 /* 266 * Drop the segment if it does not contain an ACK. 267 */ 268 if ((thflags & TH_ACK) == 0) 269 goto drop; 270 271 INP_WLOCK_ASSERT(inp); 272 273 /* 274 * If timestamps were negotiated during SYN/ACK and a 275 * segment without a timestamp is received, silently drop 276 * the segment, unless the missing timestamps are tolerated. 277 * See section 3.2 of RFC 7323. 278 */ 279 if (((to->to_flags & TOF_TS) == 0) && (tp->ts_recent != 0) && 280 (V_tcp_tolerate_missing_ts == 0)) { 281 goto drop; 282 } 283 284 /* 285 * Reset the 2MSL timer if this is a duplicate FIN. 286 */ 287 if (thflags & TH_FIN) { 288 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 289 if (seq + 1 == tp->rcv_nxt) 290 tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl); 291 } 292 293 /* 294 * Acknowledge the segment if it has data or is not a duplicate ACK. 295 */ 296 if (thflags != TH_ACK || tlen != 0 || 297 th->th_seq != tp->rcv_nxt || th->th_ack != tp->snd_nxt) { 298 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 299 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 300 tp->snd_nxt, TH_ACK); 301 INP_UNLOCK(inp); 302 TCPSTAT_INC(tcps_tw_responds); 303 return (false); 304 } 305 drop: 306 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 307 INP_UNLOCK(inp); 308 m_freem(m); 309 return (false); 310 } 311