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 32 #include <sys/cdefs.h> 33 #include "opt_inet.h" 34 #include "opt_inet6.h" 35 #include "opt_ipsec.h" 36 37 #include <sys/param.h> 38 #include <sys/systm.h> 39 #include <sys/callout.h> 40 #include <sys/kernel.h> 41 #include <sys/sysctl.h> 42 #include <sys/malloc.h> 43 #include <sys/mbuf.h> 44 #include <sys/priv.h> 45 #include <sys/proc.h> 46 #include <sys/socket.h> 47 #include <sys/socketvar.h> 48 #include <sys/syslog.h> 49 #include <sys/protosw.h> 50 #include <sys/random.h> 51 52 #include <vm/uma.h> 53 54 #include <net/route.h> 55 #include <net/if.h> 56 #include <net/if_var.h> 57 #include <net/vnet.h> 58 59 #include <netinet/in.h> 60 #include <netinet/in_kdtrace.h> 61 #include <netinet/in_pcb.h> 62 #include <netinet/in_systm.h> 63 #include <netinet/in_var.h> 64 #include <netinet/ip.h> 65 #include <netinet/ip_icmp.h> 66 #include <netinet/ip_var.h> 67 #ifdef INET6 68 #include <netinet/ip6.h> 69 #include <netinet6/in6_pcb.h> 70 #include <netinet6/ip6_var.h> 71 #include <netinet6/scope6_var.h> 72 #include <netinet6/nd6.h> 73 #endif 74 #include <netinet/tcp.h> 75 #include <netinet/tcp_fsm.h> 76 #include <netinet/tcp_seq.h> 77 #include <netinet/tcp_timer.h> 78 #include <netinet/tcp_var.h> 79 #include <netinet/tcpip.h> 80 81 #include <netinet/udp.h> 82 #include <netinet/udp_var.h> 83 84 #include <netipsec/ipsec_support.h> 85 86 #include <machine/in_cksum.h> 87 88 #include <security/mac/mac_framework.h> 89 90 VNET_DEFINE_STATIC(bool, nolocaltimewait) = false; 91 #define V_nolocaltimewait VNET(nolocaltimewait) 92 93 static int 94 sysctl_net_inet_tcp_nolocaltimewait(SYSCTL_HANDLER_ARGS) 95 { 96 int error; 97 bool new; 98 99 new = V_nolocaltimewait; 100 error = sysctl_handle_bool(oidp, &new, 0, req); 101 if (error == 0 && req->newptr) { 102 V_nolocaltimewait = new; 103 gone_in(16, "net.inet.tcp.nolocaltimewait is obsolete." 104 " Use net.inet.tcp.msl_local instead.\n"); 105 } 106 return (error); 107 } 108 109 SYSCTL_PROC(_net_inet_tcp, OID_AUTO, nolocaltimewait, 110 CTLFLAG_VNET | CTLFLAG_RW | CTLTYPE_U8, 111 &VNET_NAME(nolocaltimewait), 0, sysctl_net_inet_tcp_nolocaltimewait, "CU", 112 "Do not create TCP TIME_WAIT state for local connections"); 113 114 static u_int 115 tcp_eff_msl(struct tcpcb *tp) 116 { 117 struct inpcb *inp = tptoinpcb(tp); 118 #ifdef INET6 119 bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 120 #endif 121 122 if ( 123 #ifdef INET6 124 isipv6 ? in6_localip(&inp->in6p_faddr) : 125 #endif 126 #ifdef INET 127 in_localip(inp->inp_faddr)) 128 #else 129 false) 130 #endif 131 return (V_tcp_msl_local); 132 else 133 return (V_tcp_msl); 134 } 135 136 /* 137 * Move a TCP connection into TIME_WAIT state. 138 * inp is locked, and is unlocked before returning. 139 * 140 * This function used to free tcpcb and allocate a compressed TCP time-wait 141 * structure tcptw. This served well for 20 years but is no longer relevant 142 * on modern machines in the modern internet. However, the function remains 143 * so that TCP stacks require less modification and we don't burn the bridge 144 * to go back to using compressed time-wait. 145 */ 146 void 147 tcp_twstart(struct tcpcb *tp) 148 { 149 struct inpcb *inp = tptoinpcb(tp); 150 #ifdef INET6 151 bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 152 #endif 153 154 NET_EPOCH_ASSERT(); 155 INP_WLOCK_ASSERT(inp); 156 157 /* A dropped inp should never transition to TIME_WAIT state. */ 158 KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: " 159 "(inp->inp_flags & INP_DROPPED) != 0")); 160 161 tcp_state_change(tp, TCPS_TIME_WAIT); 162 tcp_free_sackholes(tp); 163 soisdisconnected(inp->inp_socket); 164 165 if (tp->t_flags & TF_ACKNOW) 166 (void) tcp_output(tp); 167 168 if (V_nolocaltimewait && ( 169 #ifdef INET6 170 isipv6 ? in6_localip(&inp->in6p_faddr) : 171 #endif 172 #ifdef INET 173 in_localip(inp->inp_faddr) 174 #else 175 false 176 #endif 177 )) { 178 if ((tp = tcp_close(tp)) != NULL) 179 INP_WUNLOCK(inp); 180 return; 181 } 182 183 tcp_timer_activate(tp, TT_2MSL, 2 * tcp_eff_msl(tp)); 184 INP_WUNLOCK(inp); 185 } 186 187 /* 188 * Returns true if the TIME_WAIT state was killed and we should start over, 189 * looking for a pcb in the listen state. Otherwise returns false and frees 190 * the mbuf. 191 * 192 * For pure SYN-segments the PCB shall be read-locked and the tcpopt pointer 193 * may be NULL. For the rest write-lock and valid tcpopt. 194 */ 195 bool 196 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th, 197 struct mbuf *m, int tlen) 198 { 199 struct tcpcb *tp = intotcpcb(inp); 200 char *s; 201 int thflags; 202 tcp_seq seq; 203 204 NET_EPOCH_ASSERT(); 205 INP_LOCK_ASSERT(inp); 206 207 thflags = tcp_get_flags(th); 208 #ifdef INVARIANTS 209 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) 210 INP_RLOCK_ASSERT(inp); 211 else { 212 INP_WLOCK_ASSERT(inp); 213 KASSERT(to != NULL, 214 ("%s: called without options on a non-SYN segment", 215 __func__)); 216 } 217 #endif 218 219 /* 220 * NOTE: for FIN_WAIT_2 (to be added later), 221 * must validate sequence number before accepting RST 222 */ 223 224 /* 225 * If the segment contains RST: 226 * Drop the segment - see Stevens, vol. 2, p. 964 and 227 * RFC 1337. 228 */ 229 if (thflags & TH_RST) 230 goto drop; 231 232 #if 0 233 /* PAWS not needed at the moment */ 234 /* 235 * RFC 1323 PAWS: If we have a timestamp reply on this segment 236 * and it's less than ts_recent, drop it. 237 */ 238 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 239 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 240 if ((thflags & TH_ACK) == 0) 241 goto drop; 242 goto ack; 243 } 244 /* 245 * ts_recent is never updated because we never accept new segments. 246 */ 247 #endif 248 249 /* Honor the drop_synfin sysctl variable. */ 250 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 251 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) { 252 log(LOG_DEBUG, "%s; %s: " 253 "SYN|FIN segment ignored (based on " 254 "sysctl setting)\n", s, __func__); 255 free(s, M_TCPLOG); 256 } 257 goto drop; 258 } 259 260 /* 261 * If a new connection request is received 262 * while in TIME_WAIT, drop the old connection 263 * and start over if the sequence numbers 264 * are above the previous ones. 265 * Allow UDP port number changes in this case. 266 */ 267 if (((thflags & (TH_SYN | TH_ACK)) == TH_SYN) && 268 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 269 /* 270 * In case we can't upgrade our lock just pretend we have 271 * lost this packet. 272 */ 273 if (INP_TRY_UPGRADE(inp) == 0) 274 goto drop; 275 if ((tp = tcp_close(tp)) != NULL) 276 INP_WUNLOCK(inp); 277 TCPSTAT_INC(tcps_tw_recycles); 278 return (true); 279 } 280 281 /* 282 * Send RST if UDP port numbers don't match 283 */ 284 if (tp->t_port != m->m_pkthdr.tcp_tun_port) { 285 if (tcp_get_flags(th) & TH_ACK) { 286 tcp_respond(tp, mtod(m, void *), th, m, 287 (tcp_seq)0, th->th_ack, TH_RST); 288 } else { 289 if (tcp_get_flags(th) & TH_SYN) 290 tlen++; 291 if (tcp_get_flags(th) & TH_FIN) 292 tlen++; 293 tcp_respond(tp, mtod(m, void *), th, m, 294 th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK); 295 } 296 INP_UNLOCK(inp); 297 TCPSTAT_INC(tcps_tw_resets); 298 return (false); 299 } 300 301 /* 302 * Drop the segment if it does not contain an ACK. 303 */ 304 if ((thflags & TH_ACK) == 0) 305 goto drop; 306 307 INP_WLOCK_ASSERT(inp); 308 309 /* 310 * If timestamps were negotiated during SYN/ACK and a 311 * segment without a timestamp is received, silently drop 312 * the segment, unless the missing timestamps are tolerated. 313 * See section 3.2 of RFC 7323. 314 */ 315 if (((to->to_flags & TOF_TS) == 0) && (tp->ts_recent != 0) && 316 (V_tcp_tolerate_missing_ts == 0)) { 317 goto drop; 318 } 319 320 /* 321 * Reset the 2MSL timer if this is a duplicate FIN. 322 */ 323 if (thflags & TH_FIN) { 324 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 325 if (seq + 1 == tp->rcv_nxt) 326 tcp_timer_activate(tp, TT_2MSL, 2 * tcp_eff_msl(tp)); 327 } 328 329 /* 330 * Acknowledge the segment if it has data or is not a duplicate ACK. 331 */ 332 if (thflags != TH_ACK || tlen != 0 || 333 th->th_seq != tp->rcv_nxt || th->th_ack != tp->snd_nxt) { 334 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 335 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 336 tp->snd_nxt, TH_ACK); 337 INP_UNLOCK(inp); 338 TCPSTAT_INC(tcps_tw_responds); 339 return (false); 340 } 341 drop: 342 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 343 INP_UNLOCK(inp); 344 m_freem(m); 345 return (false); 346 } 347