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 #include "opt_inet.h" 36 #include "opt_inet6.h" 37 #include "opt_ipsec.h" 38 39 #include <sys/param.h> 40 #include <sys/systm.h> 41 #include <sys/callout.h> 42 #include <sys/kernel.h> 43 #include <sys/sysctl.h> 44 #include <sys/malloc.h> 45 #include <sys/mbuf.h> 46 #include <sys/priv.h> 47 #include <sys/proc.h> 48 #include <sys/socket.h> 49 #include <sys/socketvar.h> 50 #include <sys/syslog.h> 51 #include <sys/protosw.h> 52 #include <sys/random.h> 53 54 #include <vm/uma.h> 55 56 #include <net/route.h> 57 #include <net/if.h> 58 #include <net/if_var.h> 59 #include <net/vnet.h> 60 61 #include <netinet/in.h> 62 #include <netinet/in_kdtrace.h> 63 #include <netinet/in_pcb.h> 64 #include <netinet/in_systm.h> 65 #include <netinet/in_var.h> 66 #include <netinet/ip.h> 67 #include <netinet/ip_icmp.h> 68 #include <netinet/ip_var.h> 69 #ifdef INET6 70 #include <netinet/ip6.h> 71 #include <netinet6/in6_pcb.h> 72 #include <netinet6/ip6_var.h> 73 #include <netinet6/scope6_var.h> 74 #include <netinet6/nd6.h> 75 #endif 76 #include <netinet/tcp.h> 77 #include <netinet/tcp_fsm.h> 78 #include <netinet/tcp_seq.h> 79 #include <netinet/tcp_timer.h> 80 #include <netinet/tcp_var.h> 81 #include <netinet/tcpip.h> 82 83 #include <netinet/udp.h> 84 #include <netinet/udp_var.h> 85 86 #include <netipsec/ipsec_support.h> 87 88 #include <machine/in_cksum.h> 89 90 #include <security/mac/mac_framework.h> 91 92 VNET_DEFINE_STATIC(bool, nolocaltimewait) = true; 93 #define V_nolocaltimewait VNET(nolocaltimewait) 94 SYSCTL_BOOL(_net_inet_tcp, OID_AUTO, nolocaltimewait, 95 CTLFLAG_VNET | CTLFLAG_RW, &VNET_NAME(nolocaltimewait), true, 96 "Do not create TCP TIME_WAIT state for local connections"); 97 98 /* 99 * Move a TCP connection into TIME_WAIT state. 100 * inp is locked, and is unlocked before returning. 101 * 102 * This function used to free tcpcb and allocate a compressed TCP time-wait 103 * structure tcptw. This served well for 20 years but is no longer relevant 104 * on modern machines in the modern internet. However, the function remains 105 * so that TCP stacks require less modification and we don't burn the bridge 106 * to go back to using compressed time-wait. 107 */ 108 void 109 tcp_twstart(struct tcpcb *tp) 110 { 111 struct inpcb *inp = tptoinpcb(tp); 112 #ifdef INET6 113 bool isipv6 = inp->inp_inc.inc_flags & INC_ISIPV6; 114 #endif 115 116 NET_EPOCH_ASSERT(); 117 INP_WLOCK_ASSERT(inp); 118 119 /* A dropped inp should never transition to TIME_WAIT state. */ 120 KASSERT((inp->inp_flags & INP_DROPPED) == 0, ("tcp_twstart: " 121 "(inp->inp_flags & INP_DROPPED) != 0")); 122 123 tcp_state_change(tp, TCPS_TIME_WAIT); 124 soisdisconnected(inp->inp_socket); 125 126 if (tp->t_flags & TF_ACKNOW) 127 tcp_output(tp); 128 129 if (V_nolocaltimewait && ( 130 #ifdef INET6 131 isipv6 ? in6_localaddr(&inp->in6p_faddr) : 132 #endif 133 #ifdef INET 134 in_localip(inp->inp_faddr) 135 #else 136 false 137 #endif 138 )) { 139 if ((tp = tcp_close(tp)) != NULL) 140 INP_WUNLOCK(inp); 141 return; 142 } 143 144 tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl); 145 INP_WUNLOCK(inp); 146 } 147 148 /* 149 * Returns true if the TIME_WAIT state was killed and we should start over, 150 * looking for a pcb in the listen state. Otherwise returns false and frees 151 * the mbuf. 152 * 153 * For pure SYN-segments the PCB shall be read-locked and the tcpopt pointer 154 * may be NULL. For the rest write-lock and valid tcpopt. 155 */ 156 bool 157 tcp_twcheck(struct inpcb *inp, struct tcpopt *to, struct tcphdr *th, 158 struct mbuf *m, int tlen) 159 { 160 struct tcpcb *tp = intotcpcb(inp); 161 char *s; 162 int thflags; 163 tcp_seq seq; 164 165 NET_EPOCH_ASSERT(); 166 INP_LOCK_ASSERT(inp); 167 168 thflags = tcp_get_flags(th); 169 #ifdef INVARIANTS 170 if ((thflags & (TH_SYN | TH_ACK)) == TH_SYN) 171 INP_RLOCK_ASSERT(inp); 172 else { 173 INP_WLOCK_ASSERT(inp); 174 KASSERT(to != NULL, 175 ("%s: called without options on a non-SYN segment", 176 __func__)); 177 } 178 #endif 179 180 /* 181 * NOTE: for FIN_WAIT_2 (to be added later), 182 * must validate sequence number before accepting RST 183 */ 184 185 /* 186 * If the segment contains RST: 187 * Drop the segment - see Stevens, vol. 2, p. 964 and 188 * RFC 1337. 189 */ 190 if (thflags & TH_RST) 191 goto drop; 192 193 #if 0 194 /* PAWS not needed at the moment */ 195 /* 196 * RFC 1323 PAWS: If we have a timestamp reply on this segment 197 * and it's less than ts_recent, drop it. 198 */ 199 if ((to.to_flags & TOF_TS) != 0 && tp->ts_recent && 200 TSTMP_LT(to.to_tsval, tp->ts_recent)) { 201 if ((thflags & TH_ACK) == 0) 202 goto drop; 203 goto ack; 204 } 205 /* 206 * ts_recent is never updated because we never accept new segments. 207 */ 208 #endif 209 210 /* Honor the drop_synfin sysctl variable. */ 211 if ((thflags & TH_SYN) && (thflags & TH_FIN) && V_drop_synfin) { 212 if ((s = tcp_log_addrs(&inp->inp_inc, th, NULL, NULL))) { 213 log(LOG_DEBUG, "%s; %s: " 214 "SYN|FIN segment ignored (based on " 215 "sysctl setting)\n", s, __func__); 216 free(s, M_TCPLOG); 217 } 218 goto drop; 219 } 220 221 /* 222 * If a new connection request is received 223 * while in TIME_WAIT, drop the old connection 224 * and start over if the sequence numbers 225 * are above the previous ones. 226 * Allow UDP port number changes in this case. 227 */ 228 if (((thflags & (TH_SYN | TH_ACK)) == TH_SYN) && 229 SEQ_GT(th->th_seq, tp->rcv_nxt)) { 230 /* 231 * In case we can't upgrade our lock just pretend we have 232 * lost this packet. 233 */ 234 if (INP_TRY_UPGRADE(inp) == 0) 235 goto drop; 236 if ((tp = tcp_close(tp)) != NULL) 237 INP_WUNLOCK(inp); 238 TCPSTAT_INC(tcps_tw_recycles); 239 return (true); 240 } 241 242 /* 243 * Send RST if UDP port numbers don't match 244 */ 245 if (tp->t_port != m->m_pkthdr.tcp_tun_port) { 246 if (tcp_get_flags(th) & TH_ACK) { 247 tcp_respond(tp, mtod(m, void *), th, m, 248 (tcp_seq)0, th->th_ack, TH_RST); 249 } else { 250 if (tcp_get_flags(th) & TH_SYN) 251 tlen++; 252 if (tcp_get_flags(th) & TH_FIN) 253 tlen++; 254 tcp_respond(tp, mtod(m, void *), th, m, 255 th->th_seq+tlen, (tcp_seq)0, TH_RST|TH_ACK); 256 } 257 INP_UNLOCK(inp); 258 TCPSTAT_INC(tcps_tw_resets); 259 return (false); 260 } 261 262 /* 263 * Drop the segment if it does not contain an ACK. 264 */ 265 if ((thflags & TH_ACK) == 0) 266 goto drop; 267 268 INP_WLOCK_ASSERT(inp); 269 270 /* 271 * If timestamps were negotiated during SYN/ACK and a 272 * segment without a timestamp is received, silently drop 273 * the segment, unless the missing timestamps are tolerated. 274 * See section 3.2 of RFC 7323. 275 */ 276 if (((to->to_flags & TOF_TS) == 0) && (tp->ts_recent != 0) && 277 (V_tcp_tolerate_missing_ts == 0)) { 278 goto drop; 279 } 280 281 /* 282 * Reset the 2MSL timer if this is a duplicate FIN. 283 */ 284 if (thflags & TH_FIN) { 285 seq = th->th_seq + tlen + (thflags & TH_SYN ? 1 : 0); 286 if (seq + 1 == tp->rcv_nxt) 287 tcp_timer_activate(tp, TT_2MSL, 2 * V_tcp_msl); 288 } 289 290 /* 291 * Acknowledge the segment if it has data or is not a duplicate ACK. 292 */ 293 if (thflags != TH_ACK || tlen != 0 || 294 th->th_seq != tp->rcv_nxt || th->th_ack != tp->snd_nxt) { 295 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 296 tcp_respond(tp, mtod(m, void *), th, m, tp->rcv_nxt, 297 tp->snd_nxt, TH_ACK); 298 INP_UNLOCK(inp); 299 TCPSTAT_INC(tcps_tw_responds); 300 return (false); 301 } 302 drop: 303 TCP_PROBE5(receive, NULL, NULL, m, NULL, th); 304 INP_UNLOCK(inp); 305 m_freem(m); 306 return (false); 307 } 308