1 /* $NetBSD: tcp_subr.c,v 1.19 1995/06/12 06:48:54 mycroft Exp $ */ 2 3 /* 4 * Copyright (c) 1982, 1986, 1988, 1990, 1993 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. All advertising materials mentioning features or use of this software 16 * must display the following acknowledgement: 17 * This product includes software developed by the University of 18 * California, Berkeley and its contributors. 19 * 4. Neither the name of the University nor the names of its contributors 20 * may be used to endorse or promote products derived from this software 21 * without specific prior written permission. 22 * 23 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 24 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 25 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 26 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 27 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 28 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 29 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 30 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 31 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 32 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 33 * SUCH DAMAGE. 34 * 35 * @(#)tcp_subr.c 8.1 (Berkeley) 6/10/93 36 */ 37 38 #include <sys/param.h> 39 #include <sys/proc.h> 40 #include <sys/systm.h> 41 #include <sys/malloc.h> 42 #include <sys/mbuf.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/protosw.h> 46 #include <sys/errno.h> 47 48 #include <net/route.h> 49 #include <net/if.h> 50 51 #include <netinet/in.h> 52 #include <netinet/in_systm.h> 53 #include <netinet/ip.h> 54 #include <netinet/in_pcb.h> 55 #include <netinet/ip_var.h> 56 #include <netinet/ip_icmp.h> 57 #include <netinet/tcp.h> 58 #include <netinet/tcp_fsm.h> 59 #include <netinet/tcp_seq.h> 60 #include <netinet/tcp_timer.h> 61 #include <netinet/tcp_var.h> 62 #include <netinet/tcpip.h> 63 64 /* patchable/settable parameters for tcp */ 65 int tcp_mssdflt = TCP_MSS; 66 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 67 int tcp_do_rfc1323 = 1; 68 69 extern struct inpcb *tcp_last_inpcb; 70 71 /* 72 * Tcp initialization 73 */ 74 void 75 tcp_init() 76 { 77 78 tcp_iss = 1; /* wrong */ 79 in_pcbinit(&tcbtable); 80 if (max_protohdr < sizeof(struct tcpiphdr)) 81 max_protohdr = sizeof(struct tcpiphdr); 82 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 83 panic("tcp_init"); 84 } 85 86 /* 87 * Create template to be used to send tcp packets on a connection. 88 * Call after host entry created, allocates an mbuf and fills 89 * in a skeletal tcp/ip header, minimizing the amount of work 90 * necessary when the connection is used. 91 */ 92 struct tcpiphdr * 93 tcp_template(tp) 94 struct tcpcb *tp; 95 { 96 register struct inpcb *inp = tp->t_inpcb; 97 register struct mbuf *m; 98 register struct tcpiphdr *n; 99 100 if ((n = tp->t_template) == 0) { 101 m = m_get(M_DONTWAIT, MT_HEADER); 102 if (m == NULL) 103 return (0); 104 m->m_len = sizeof (struct tcpiphdr); 105 n = mtod(m, struct tcpiphdr *); 106 } 107 n->ti_next = n->ti_prev = 0; 108 n->ti_x1 = 0; 109 n->ti_pr = IPPROTO_TCP; 110 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 111 n->ti_src = inp->inp_laddr; 112 n->ti_dst = inp->inp_faddr; 113 n->ti_sport = inp->inp_lport; 114 n->ti_dport = inp->inp_fport; 115 n->ti_seq = 0; 116 n->ti_ack = 0; 117 n->ti_x2 = 0; 118 n->ti_off = 5; 119 n->ti_flags = 0; 120 n->ti_win = 0; 121 n->ti_sum = 0; 122 n->ti_urp = 0; 123 return (n); 124 } 125 126 /* 127 * Send a single message to the TCP at address specified by 128 * the given TCP/IP header. If m == 0, then we make a copy 129 * of the tcpiphdr at ti and send directly to the addressed host. 130 * This is used to force keep alive messages out using the TCP 131 * template for a connection tp->t_template. If flags are given 132 * then we send a message back to the TCP which originated the 133 * segment ti, and discard the mbuf containing it and any other 134 * attached mbufs. 135 * 136 * In any case the ack and sequence number of the transmitted 137 * segment are as specified by the parameters. 138 */ 139 void 140 tcp_respond(tp, ti, m, ack, seq, flags) 141 struct tcpcb *tp; 142 register struct tcpiphdr *ti; 143 register struct mbuf *m; 144 tcp_seq ack, seq; 145 int flags; 146 { 147 register int tlen; 148 int win = 0; 149 struct route *ro = 0; 150 151 if (tp) { 152 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 153 ro = &tp->t_inpcb->inp_route; 154 } 155 if (m == 0) { 156 m = m_gethdr(M_DONTWAIT, MT_HEADER); 157 if (m == NULL) 158 return; 159 #ifdef TCP_COMPAT_42 160 tlen = 1; 161 #else 162 tlen = 0; 163 #endif 164 m->m_data += max_linkhdr; 165 *mtod(m, struct tcpiphdr *) = *ti; 166 ti = mtod(m, struct tcpiphdr *); 167 flags = TH_ACK; 168 } else { 169 m_freem(m->m_next); 170 m->m_next = 0; 171 m->m_data = (caddr_t)ti; 172 m->m_len = sizeof (struct tcpiphdr); 173 tlen = 0; 174 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 175 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_int32_t); 176 xchg(ti->ti_dport, ti->ti_sport, u_int16_t); 177 #undef xchg 178 } 179 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 180 tlen += sizeof (struct tcpiphdr); 181 m->m_len = tlen; 182 m->m_pkthdr.len = tlen; 183 m->m_pkthdr.rcvif = (struct ifnet *) 0; 184 ti->ti_next = ti->ti_prev = 0; 185 ti->ti_x1 = 0; 186 ti->ti_seq = htonl(seq); 187 ti->ti_ack = htonl(ack); 188 ti->ti_x2 = 0; 189 ti->ti_off = sizeof (struct tcphdr) >> 2; 190 ti->ti_flags = flags; 191 if (tp) 192 ti->ti_win = htons((u_int16_t) (win >> tp->rcv_scale)); 193 else 194 ti->ti_win = htons((u_int16_t)win); 195 ti->ti_urp = 0; 196 ti->ti_sum = 0; 197 ti->ti_sum = in_cksum(m, tlen); 198 ((struct ip *)ti)->ip_len = tlen; 199 ((struct ip *)ti)->ip_ttl = ip_defttl; 200 (void) ip_output(m, NULL, ro, 0, NULL); 201 } 202 203 /* 204 * Create a new TCP control block, making an 205 * empty reassembly queue and hooking it to the argument 206 * protocol control block. 207 */ 208 struct tcpcb * 209 tcp_newtcpcb(inp) 210 struct inpcb *inp; 211 { 212 register struct tcpcb *tp; 213 214 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT); 215 if (tp == NULL) 216 return ((struct tcpcb *)0); 217 bzero((char *) tp, sizeof(struct tcpcb)); 218 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 219 tp->t_maxseg = tcp_mssdflt; 220 221 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 222 tp->t_inpcb = inp; 223 /* 224 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 225 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 226 * reasonable initial retransmit time. 227 */ 228 tp->t_srtt = TCPTV_SRTTBASE; 229 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << (TCP_RTTVAR_SHIFT + 2 - 1); 230 tp->t_rttmin = TCPTV_MIN; 231 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 232 TCPTV_MIN, TCPTV_REXMTMAX); 233 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 234 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 235 inp->inp_ip.ip_ttl = ip_defttl; 236 inp->inp_ppcb = (caddr_t)tp; 237 return (tp); 238 } 239 240 /* 241 * Drop a TCP connection, reporting 242 * the specified error. If connection is synchronized, 243 * then send a RST to peer. 244 */ 245 struct tcpcb * 246 tcp_drop(tp, errno) 247 register struct tcpcb *tp; 248 int errno; 249 { 250 struct socket *so = tp->t_inpcb->inp_socket; 251 252 if (TCPS_HAVERCVDSYN(tp->t_state)) { 253 tp->t_state = TCPS_CLOSED; 254 (void) tcp_output(tp); 255 tcpstat.tcps_drops++; 256 } else 257 tcpstat.tcps_conndrops++; 258 if (errno == ETIMEDOUT && tp->t_softerror) 259 errno = tp->t_softerror; 260 so->so_error = errno; 261 return (tcp_close(tp)); 262 } 263 264 /* 265 * Close a TCP control block: 266 * discard all space held by the tcp 267 * discard internet protocol block 268 * wake up any sleepers 269 */ 270 struct tcpcb * 271 tcp_close(tp) 272 register struct tcpcb *tp; 273 { 274 register struct tcpiphdr *t; 275 struct inpcb *inp = tp->t_inpcb; 276 struct socket *so = inp->inp_socket; 277 register struct mbuf *m; 278 #ifdef RTV_RTT 279 register struct rtentry *rt; 280 281 /* 282 * If we sent enough data to get some meaningful characteristics, 283 * save them in the routing entry. 'Enough' is arbitrarily 284 * defined as the sendpipesize (default 4K) * 16. This would 285 * give us 16 rtt samples assuming we only get one sample per 286 * window (the usual case on a long haul net). 16 samples is 287 * enough for the srtt filter to converge to within 5% of the correct 288 * value; fewer samples and we could save a very bogus rtt. 289 * 290 * Don't update the default route's characteristics and don't 291 * update anything that the user "locked". 292 */ 293 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) && 294 (rt = inp->inp_route.ro_rt) && 295 satosin(rt_key(rt))->sin_addr.s_addr != INADDR_ANY) { 296 register u_long i; 297 298 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 299 i = tp->t_srtt * 300 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 301 if (rt->rt_rmx.rmx_rtt && i) 302 /* 303 * filter this update to half the old & half 304 * the new values, converting scale. 305 * See route.h and tcp_var.h for a 306 * description of the scaling constants. 307 */ 308 rt->rt_rmx.rmx_rtt = 309 (rt->rt_rmx.rmx_rtt + i) / 2; 310 else 311 rt->rt_rmx.rmx_rtt = i; 312 } 313 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 314 i = tp->t_rttvar * 315 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 316 if (rt->rt_rmx.rmx_rttvar && i) 317 rt->rt_rmx.rmx_rttvar = 318 (rt->rt_rmx.rmx_rttvar + i) / 2; 319 else 320 rt->rt_rmx.rmx_rttvar = i; 321 } 322 /* 323 * update the pipelimit (ssthresh) if it has been updated 324 * already or if a pipesize was specified & the threshhold 325 * got below half the pipesize. I.e., wait for bad news 326 * before we start updating, then update on both good 327 * and bad news. 328 */ 329 if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 330 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh || 331 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 332 /* 333 * convert the limit from user data bytes to 334 * packets then to packet data bytes. 335 */ 336 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 337 if (i < 2) 338 i = 2; 339 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 340 if (rt->rt_rmx.rmx_ssthresh) 341 rt->rt_rmx.rmx_ssthresh = 342 (rt->rt_rmx.rmx_ssthresh + i) / 2; 343 else 344 rt->rt_rmx.rmx_ssthresh = i; 345 } 346 } 347 #endif /* RTV_RTT */ 348 /* free the reassembly queue, if any */ 349 t = tp->seg_next; 350 while (t != (struct tcpiphdr *)tp) { 351 t = (struct tcpiphdr *)t->ti_next; 352 m = REASS_MBUF((struct tcpiphdr *)t->ti_prev); 353 remque(t->ti_prev); 354 m_freem(m); 355 } 356 if (tp->t_template) 357 (void) m_free(dtom(tp->t_template)); 358 free(tp, M_PCB); 359 inp->inp_ppcb = 0; 360 soisdisconnected(so); 361 /* clobber input pcb cache if we're closing the cached connection */ 362 if (inp == tcp_last_inpcb) 363 tcp_last_inpcb = 0; 364 in_pcbdetach(inp); 365 tcpstat.tcps_closed++; 366 return ((struct tcpcb *)0); 367 } 368 369 void 370 tcp_drain() 371 { 372 373 } 374 375 /* 376 * Notify a tcp user of an asynchronous error; 377 * store error as soft error, but wake up user 378 * (for now, won't do anything until can select for soft error). 379 */ 380 void 381 tcp_notify(inp, error) 382 struct inpcb *inp; 383 int error; 384 { 385 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 386 register struct socket *so = inp->inp_socket; 387 388 /* 389 * Ignore some errors if we are hooked up. 390 * If connection hasn't completed, has retransmitted several times, 391 * and receives a second error, give up now. This is better 392 * than waiting a long time to establish a connection that 393 * can never complete. 394 */ 395 if (tp->t_state == TCPS_ESTABLISHED && 396 (error == EHOSTUNREACH || error == ENETUNREACH || 397 error == EHOSTDOWN)) { 398 return; 399 } else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 && 400 tp->t_rxtshift > 3 && tp->t_softerror) 401 so->so_error = error; 402 else 403 tp->t_softerror = error; 404 wakeup((caddr_t) &so->so_timeo); 405 sorwakeup(so); 406 sowwakeup(so); 407 } 408 409 void 410 tcp_ctlinput(cmd, sa, ip) 411 int cmd; 412 struct sockaddr *sa; 413 register struct ip *ip; 414 { 415 register struct tcphdr *th; 416 extern struct in_addr zeroin_addr; 417 extern int inetctlerrmap[]; 418 void (*notify) __P((struct inpcb *, int)) = tcp_notify; 419 int errno; 420 421 if ((unsigned)cmd >= PRC_NCMDS) 422 return; 423 errno = inetctlerrmap[cmd]; 424 if (cmd == PRC_QUENCH) 425 notify = tcp_quench; 426 else if (PRC_IS_REDIRECT(cmd)) 427 notify = in_rtchange, ip = 0; 428 else if (cmd == PRC_HOSTDEAD) 429 ip = 0; 430 else if (errno == 0) 431 return; 432 if (ip) { 433 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 434 in_pcbnotify(&tcbtable, sa, th->th_dport, ip->ip_src, 435 th->th_sport, errno, notify); 436 } else 437 in_pcbnotifyall(&tcbtable, sa, errno, notify); 438 } 439 440 /* 441 * When a source quench is received, close congestion window 442 * to one segment. We will gradually open it again as we proceed. 443 */ 444 void 445 tcp_quench(inp, errno) 446 struct inpcb *inp; 447 int errno; 448 { 449 struct tcpcb *tp = intotcpcb(inp); 450 451 if (tp) 452 tp->snd_cwnd = tp->t_maxseg; 453 } 454