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