1 /* $OpenBSD: tcp_subr.c,v 1.7 1996/07/29 22:01:50 niklas Exp $ */ 2 /* $NetBSD: tcp_subr.c,v 1.22 1996/02/13 23:44:00 christos Exp $ */ 3 4 /* 5 * Copyright (c) 1982, 1986, 1988, 1990, 1993 6 * The Regents of the University of California. All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice, this list of conditions and the following disclaimer. 13 * 2. Redistributions in binary form must reproduce the above copyright 14 * notice, this list of conditions and the following disclaimer in the 15 * documentation and/or other materials provided with the distribution. 16 * 3. All advertising materials mentioning features or use of this software 17 * must display the following acknowledgement: 18 * This product includes software developed by the University of 19 * California, Berkeley and its contributors. 20 * 4. Neither the name of the University nor the names of its contributors 21 * may be used to endorse or promote products derived from this software 22 * without specific prior written permission. 23 * 24 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 25 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 26 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 27 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 28 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 29 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 30 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 31 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 32 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 33 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 34 * SUCH DAMAGE. 35 * 36 * @(#)tcp_subr.c 8.1 (Berkeley) 6/10/93 37 */ 38 39 #include <sys/param.h> 40 #include <sys/proc.h> 41 #include <sys/systm.h> 42 #include <sys/malloc.h> 43 #include <sys/mbuf.h> 44 #include <sys/socket.h> 45 #include <sys/socketvar.h> 46 #include <sys/protosw.h> 47 #include <sys/errno.h> 48 49 #include <net/route.h> 50 #include <net/if.h> 51 52 #include <netinet/in.h> 53 #include <netinet/in_systm.h> 54 #include <netinet/ip.h> 55 #include <netinet/in_pcb.h> 56 #include <netinet/ip_var.h> 57 #include <netinet/ip_icmp.h> 58 #include <netinet/tcp.h> 59 #include <netinet/tcp_fsm.h> 60 #include <netinet/tcp_seq.h> 61 #include <netinet/tcp_timer.h> 62 #include <netinet/tcp_var.h> 63 #include <netinet/tcpip.h> 64 65 /* patchable/settable parameters for tcp */ 66 int tcp_mssdflt = TCP_MSS; 67 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 68 69 /* 70 * Configure kernel with options "TCP_DO_RFC1323=0" to disable RFC1323 stuff. 71 * This is a good idea over slow SLIP/PPP links, because the timestamp 72 * pretty well destroys the VJ compression (any packet with a timestamp 73 * different from the previous one can't be compressed), as well as adding 74 * more overhead. 75 * XXX And it should be a settable per route characteristic (with this just 76 * used as the default). 77 */ 78 #ifndef TCP_DO_RFC1323 79 #define TCP_DO_RFC1323 1 80 #endif 81 int tcp_do_rfc1323 = TCP_DO_RFC1323; 82 83 #ifndef TCBHASHSIZE 84 #define TCBHASHSIZE 128 85 #endif 86 int tcbhashsize = TCBHASHSIZE; 87 88 /* 89 * Tcp initialization 90 */ 91 void 92 tcp_init() 93 { 94 #ifdef TCP_COMPAT_42 95 tcp_iss = 1; /* wrong */ 96 #else /* TCP_COMPAT_42 */ 97 tcp_iss = random() + 1; 98 #endif /* !TCP_COMPAT_42 */ 99 in_pcbinit(&tcbtable, tcbhashsize); 100 if (max_protohdr < sizeof(struct tcpiphdr)) 101 max_protohdr = sizeof(struct tcpiphdr); 102 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 103 panic("tcp_init"); 104 } 105 106 /* 107 * Create template to be used to send tcp packets on a connection. 108 * Call after host entry created, allocates an mbuf and fills 109 * in a skeletal tcp/ip header, minimizing the amount of work 110 * necessary when the connection is used. 111 */ 112 struct tcpiphdr * 113 tcp_template(tp) 114 struct tcpcb *tp; 115 { 116 register struct inpcb *inp = tp->t_inpcb; 117 register struct mbuf *m; 118 register struct tcpiphdr *n; 119 120 if ((n = tp->t_template) == 0) { 121 m = m_get(M_DONTWAIT, MT_HEADER); 122 if (m == NULL) 123 return (0); 124 m->m_len = sizeof (struct tcpiphdr); 125 n = mtod(m, struct tcpiphdr *); 126 } 127 bzero(n->ti_x1, sizeof n->ti_x1); 128 n->ti_pr = IPPROTO_TCP; 129 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 130 n->ti_src = inp->inp_laddr; 131 n->ti_dst = inp->inp_faddr; 132 n->ti_sport = inp->inp_lport; 133 n->ti_dport = inp->inp_fport; 134 n->ti_seq = 0; 135 n->ti_ack = 0; 136 n->ti_x2 = 0; 137 n->ti_off = 5; 138 n->ti_flags = 0; 139 n->ti_win = 0; 140 n->ti_sum = 0; 141 n->ti_urp = 0; 142 return (n); 143 } 144 145 /* 146 * Send a single message to the TCP at address specified by 147 * the given TCP/IP header. If m == 0, then we make a copy 148 * of the tcpiphdr at ti and send directly to the addressed host. 149 * This is used to force keep alive messages out using the TCP 150 * template for a connection tp->t_template. If flags are given 151 * then we send a message back to the TCP which originated the 152 * segment ti, and discard the mbuf containing it and any other 153 * attached mbufs. 154 * 155 * In any case the ack and sequence number of the transmitted 156 * segment are as specified by the parameters. 157 */ 158 void 159 tcp_respond(tp, ti, m, ack, seq, flags) 160 struct tcpcb *tp; 161 register struct tcpiphdr *ti; 162 register struct mbuf *m; 163 tcp_seq ack, seq; 164 int flags; 165 { 166 register int tlen; 167 int win = 0; 168 struct route *ro = 0; 169 170 if (tp) { 171 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 172 ro = &tp->t_inpcb->inp_route; 173 } 174 if (m == 0) { 175 m = m_gethdr(M_DONTWAIT, MT_HEADER); 176 if (m == NULL) 177 return; 178 #ifdef TCP_COMPAT_42 179 tlen = 1; 180 #else 181 tlen = 0; 182 #endif 183 m->m_data += max_linkhdr; 184 *mtod(m, struct tcpiphdr *) = *ti; 185 ti = mtod(m, struct tcpiphdr *); 186 flags = TH_ACK; 187 } else { 188 m_freem(m->m_next); 189 m->m_next = 0; 190 m->m_data = (caddr_t)ti; 191 m->m_len = sizeof (struct tcpiphdr); 192 tlen = 0; 193 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 194 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_int32_t); 195 xchg(ti->ti_dport, ti->ti_sport, u_int16_t); 196 #undef xchg 197 } 198 ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) + tlen)); 199 tlen += sizeof (struct tcpiphdr); 200 m->m_len = tlen; 201 m->m_pkthdr.len = tlen; 202 m->m_pkthdr.rcvif = (struct ifnet *) 0; 203 bzero(ti->ti_x1, sizeof ti->ti_x1); 204 ti->ti_seq = htonl(seq); 205 ti->ti_ack = htonl(ack); 206 ti->ti_x2 = 0; 207 ti->ti_off = sizeof (struct tcphdr) >> 2; 208 ti->ti_flags = flags; 209 if (tp) 210 ti->ti_win = htons((u_int16_t) (win >> tp->rcv_scale)); 211 else 212 ti->ti_win = htons((u_int16_t)win); 213 ti->ti_urp = 0; 214 ti->ti_sum = 0; 215 ti->ti_sum = in_cksum(m, tlen); 216 ((struct ip *)ti)->ip_len = tlen; 217 ((struct ip *)ti)->ip_ttl = ip_defttl; 218 (void) ip_output(m, NULL, ro, 0, NULL); 219 } 220 221 /* 222 * Create a new TCP control block, making an 223 * empty reassembly queue and hooking it to the argument 224 * protocol control block. 225 */ 226 struct tcpcb * 227 tcp_newtcpcb(inp) 228 struct inpcb *inp; 229 { 230 register struct tcpcb *tp; 231 232 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT); 233 if (tp == NULL) 234 return ((struct tcpcb *)0); 235 bzero((char *) tp, sizeof(struct tcpcb)); 236 LIST_INIT(&tp->segq); 237 tp->t_maxseg = tcp_mssdflt; 238 239 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 240 tp->t_inpcb = inp; 241 /* 242 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 243 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 244 * reasonable initial retransmit time. 245 */ 246 tp->t_srtt = TCPTV_SRTTBASE; 247 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << (TCP_RTTVAR_SHIFT + 2 - 1); 248 tp->t_rttmin = TCPTV_MIN; 249 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 250 TCPTV_MIN, TCPTV_REXMTMAX); 251 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 252 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 253 inp->inp_ip.ip_ttl = ip_defttl; 254 inp->inp_ppcb = (caddr_t)tp; 255 return (tp); 256 } 257 258 /* 259 * Drop a TCP connection, reporting 260 * the specified error. If connection is synchronized, 261 * then send a RST to peer. 262 */ 263 struct tcpcb * 264 tcp_drop(tp, errno) 265 register struct tcpcb *tp; 266 int errno; 267 { 268 struct socket *so = tp->t_inpcb->inp_socket; 269 270 if (TCPS_HAVERCVDSYN(tp->t_state)) { 271 tp->t_state = TCPS_CLOSED; 272 (void) tcp_output(tp); 273 tcpstat.tcps_drops++; 274 } else 275 tcpstat.tcps_conndrops++; 276 if (errno == ETIMEDOUT && tp->t_softerror) 277 errno = tp->t_softerror; 278 so->so_error = errno; 279 return (tcp_close(tp)); 280 } 281 282 /* 283 * Close a TCP control block: 284 * discard all space held by the tcp 285 * discard internet protocol block 286 * wake up any sleepers 287 */ 288 struct tcpcb * 289 tcp_close(tp) 290 register struct tcpcb *tp; 291 { 292 register struct ipqent *qe; 293 struct inpcb *inp = tp->t_inpcb; 294 struct socket *so = inp->inp_socket; 295 #ifdef RTV_RTT 296 register struct rtentry *rt; 297 298 /* 299 * If we sent enough data to get some meaningful characteristics, 300 * save them in the routing entry. 'Enough' is arbitrarily 301 * defined as the sendpipesize (default 4K) * 16. This would 302 * give us 16 rtt samples assuming we only get one sample per 303 * window (the usual case on a long haul net). 16 samples is 304 * enough for the srtt filter to converge to within 5% of the correct 305 * value; fewer samples and we could save a very bogus rtt. 306 * 307 * Don't update the default route's characteristics and don't 308 * update anything that the user "locked". 309 */ 310 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) && 311 (rt = inp->inp_route.ro_rt) && 312 satosin(rt_key(rt))->sin_addr.s_addr != INADDR_ANY) { 313 register u_long i = 0; 314 315 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 316 i = tp->t_srtt * 317 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 318 if (rt->rt_rmx.rmx_rtt && i) 319 /* 320 * filter this update to half the old & half 321 * the new values, converting scale. 322 * See route.h and tcp_var.h for a 323 * description of the scaling constants. 324 */ 325 rt->rt_rmx.rmx_rtt = 326 (rt->rt_rmx.rmx_rtt + i) / 2; 327 else 328 rt->rt_rmx.rmx_rtt = i; 329 } 330 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 331 i = tp->t_rttvar * 332 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 333 if (rt->rt_rmx.rmx_rttvar && i) 334 rt->rt_rmx.rmx_rttvar = 335 (rt->rt_rmx.rmx_rttvar + i) / 2; 336 else 337 rt->rt_rmx.rmx_rttvar = i; 338 } 339 /* 340 * update the pipelimit (ssthresh) if it has been updated 341 * already or if a pipesize was specified & the threshhold 342 * got below half the pipesize. I.e., wait for bad news 343 * before we start updating, then update on both good 344 * and bad news. 345 */ 346 if (((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 347 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh) || 348 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 349 /* 350 * convert the limit from user data bytes to 351 * packets then to packet data bytes. 352 */ 353 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 354 if (i < 2) 355 i = 2; 356 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 357 if (rt->rt_rmx.rmx_ssthresh) 358 rt->rt_rmx.rmx_ssthresh = 359 (rt->rt_rmx.rmx_ssthresh + i) / 2; 360 else 361 rt->rt_rmx.rmx_ssthresh = i; 362 } 363 } 364 #endif /* RTV_RTT */ 365 /* free the reassembly queue, if any */ 366 while ((qe = tp->segq.lh_first) != NULL) { 367 LIST_REMOVE(qe, ipqe_q); 368 m_freem(qe->ipqe_m); 369 FREE(qe, M_IPQ); 370 } 371 if (tp->t_template) 372 (void) m_free(dtom(tp->t_template)); 373 free(tp, M_PCB); 374 inp->inp_ppcb = 0; 375 soisdisconnected(so); 376 in_pcbdetach(inp); 377 tcpstat.tcps_closed++; 378 return ((struct tcpcb *)0); 379 } 380 381 void 382 tcp_drain() 383 { 384 385 } 386 387 /* 388 * Notify a tcp user of an asynchronous error; 389 * store error as soft error, but wake up user 390 * (for now, won't do anything until can select for soft error). 391 */ 392 void 393 tcp_notify(inp, error) 394 struct inpcb *inp; 395 int error; 396 { 397 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 398 register struct socket *so = inp->inp_socket; 399 400 /* 401 * Ignore some errors if we are hooked up. 402 * If connection hasn't completed, has retransmitted several times, 403 * and receives a second error, give up now. This is better 404 * than waiting a long time to establish a connection that 405 * can never complete. 406 */ 407 if (tp->t_state == TCPS_ESTABLISHED && 408 (error == EHOSTUNREACH || error == ENETUNREACH || 409 error == EHOSTDOWN)) { 410 return; 411 } else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 && 412 tp->t_rxtshift > 3 && tp->t_softerror) 413 so->so_error = error; 414 else 415 tp->t_softerror = error; 416 wakeup((caddr_t) &so->so_timeo); 417 sorwakeup(so); 418 sowwakeup(so); 419 } 420 421 void * 422 tcp_ctlinput(cmd, sa, v) 423 int cmd; 424 struct sockaddr *sa; 425 register void *v; 426 { 427 register struct ip *ip = v; 428 register struct tcphdr *th; 429 extern int inetctlerrmap[]; 430 void (*notify) __P((struct inpcb *, int)) = tcp_notify; 431 int errno; 432 433 if ((unsigned)cmd >= PRC_NCMDS) 434 return NULL; 435 errno = inetctlerrmap[cmd]; 436 if (cmd == PRC_QUENCH) 437 notify = tcp_quench; 438 else if (PRC_IS_REDIRECT(cmd)) 439 notify = in_rtchange, ip = 0; 440 else if (cmd == PRC_HOSTDEAD) 441 ip = 0; 442 else if (errno == 0) 443 return NULL; 444 if (ip) { 445 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 446 in_pcbnotify(&tcbtable, sa, th->th_dport, ip->ip_src, 447 th->th_sport, errno, notify); 448 } else 449 in_pcbnotifyall(&tcbtable, sa, errno, notify); 450 return NULL; 451 } 452 453 /* 454 * When a source quench is received, close congestion window 455 * to one segment. We will gradually open it again as we proceed. 456 */ 457 void 458 tcp_quench(inp, errno) 459 struct inpcb *inp; 460 int errno; 461 { 462 struct tcpcb *tp = intotcpcb(inp); 463 464 if (tp) 465 tp->snd_cwnd = tp->t_maxseg; 466 } 467