tcp_subr.c revision 1.22
1 /* $NetBSD: tcp_subr.c,v 1.22 1996/02/13 23:44:00 christos 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 #ifndef TCBHASHSIZE 70 #define TCBHASHSIZE 128 71 #endif 72 int tcbhashsize = TCBHASHSIZE; 73 74 /* 75 * Tcp initialization 76 */ 77 void 78 tcp_init() 79 { 80 81 tcp_iss = 1; /* wrong */ 82 in_pcbinit(&tcbtable, tcbhashsize); 83 if (max_protohdr < sizeof(struct tcpiphdr)) 84 max_protohdr = sizeof(struct tcpiphdr); 85 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 86 panic("tcp_init"); 87 } 88 89 /* 90 * Create template to be used to send tcp packets on a connection. 91 * Call after host entry created, allocates an mbuf and fills 92 * in a skeletal tcp/ip header, minimizing the amount of work 93 * necessary when the connection is used. 94 */ 95 struct tcpiphdr * 96 tcp_template(tp) 97 struct tcpcb *tp; 98 { 99 register struct inpcb *inp = tp->t_inpcb; 100 register struct mbuf *m; 101 register struct tcpiphdr *n; 102 103 if ((n = tp->t_template) == 0) { 104 m = m_get(M_DONTWAIT, MT_HEADER); 105 if (m == NULL) 106 return (0); 107 m->m_len = sizeof (struct tcpiphdr); 108 n = mtod(m, struct tcpiphdr *); 109 } 110 bzero(n->ti_x1, sizeof n->ti_x1); 111 n->ti_pr = IPPROTO_TCP; 112 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 113 n->ti_src = inp->inp_laddr; 114 n->ti_dst = inp->inp_faddr; 115 n->ti_sport = inp->inp_lport; 116 n->ti_dport = inp->inp_fport; 117 n->ti_seq = 0; 118 n->ti_ack = 0; 119 n->ti_x2 = 0; 120 n->ti_off = 5; 121 n->ti_flags = 0; 122 n->ti_win = 0; 123 n->ti_sum = 0; 124 n->ti_urp = 0; 125 return (n); 126 } 127 128 /* 129 * Send a single message to the TCP at address specified by 130 * the given TCP/IP header. If m == 0, then we make a copy 131 * of the tcpiphdr at ti and send directly to the addressed host. 132 * This is used to force keep alive messages out using the TCP 133 * template for a connection tp->t_template. If flags are given 134 * then we send a message back to the TCP which originated the 135 * segment ti, and discard the mbuf containing it and any other 136 * attached mbufs. 137 * 138 * In any case the ack and sequence number of the transmitted 139 * segment are as specified by the parameters. 140 */ 141 void 142 tcp_respond(tp, ti, m, ack, seq, flags) 143 struct tcpcb *tp; 144 register struct tcpiphdr *ti; 145 register struct mbuf *m; 146 tcp_seq ack, seq; 147 int flags; 148 { 149 register int tlen; 150 int win = 0; 151 struct route *ro = 0; 152 153 if (tp) { 154 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 155 ro = &tp->t_inpcb->inp_route; 156 } 157 if (m == 0) { 158 m = m_gethdr(M_DONTWAIT, MT_HEADER); 159 if (m == NULL) 160 return; 161 #ifdef TCP_COMPAT_42 162 tlen = 1; 163 #else 164 tlen = 0; 165 #endif 166 m->m_data += max_linkhdr; 167 *mtod(m, struct tcpiphdr *) = *ti; 168 ti = mtod(m, struct tcpiphdr *); 169 flags = TH_ACK; 170 } else { 171 m_freem(m->m_next); 172 m->m_next = 0; 173 m->m_data = (caddr_t)ti; 174 m->m_len = sizeof (struct tcpiphdr); 175 tlen = 0; 176 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 177 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_int32_t); 178 xchg(ti->ti_dport, ti->ti_sport, u_int16_t); 179 #undef xchg 180 } 181 ti->ti_len = htons((u_int16_t)(sizeof (struct tcphdr) + tlen)); 182 tlen += sizeof (struct tcpiphdr); 183 m->m_len = tlen; 184 m->m_pkthdr.len = tlen; 185 m->m_pkthdr.rcvif = (struct ifnet *) 0; 186 bzero(ti->ti_x1, sizeof ti->ti_x1); 187 ti->ti_seq = htonl(seq); 188 ti->ti_ack = htonl(ack); 189 ti->ti_x2 = 0; 190 ti->ti_off = sizeof (struct tcphdr) >> 2; 191 ti->ti_flags = flags; 192 if (tp) 193 ti->ti_win = htons((u_int16_t) (win >> tp->rcv_scale)); 194 else 195 ti->ti_win = htons((u_int16_t)win); 196 ti->ti_urp = 0; 197 ti->ti_sum = 0; 198 ti->ti_sum = in_cksum(m, tlen); 199 ((struct ip *)ti)->ip_len = tlen; 200 ((struct ip *)ti)->ip_ttl = ip_defttl; 201 (void) ip_output(m, NULL, ro, 0, NULL); 202 } 203 204 /* 205 * Create a new TCP control block, making an 206 * empty reassembly queue and hooking it to the argument 207 * protocol control block. 208 */ 209 struct tcpcb * 210 tcp_newtcpcb(inp) 211 struct inpcb *inp; 212 { 213 register struct tcpcb *tp; 214 215 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT); 216 if (tp == NULL) 217 return ((struct tcpcb *)0); 218 bzero((char *) tp, sizeof(struct tcpcb)); 219 LIST_INIT(&tp->segq); 220 tp->t_maxseg = tcp_mssdflt; 221 222 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 223 tp->t_inpcb = inp; 224 /* 225 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 226 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 227 * reasonable initial retransmit time. 228 */ 229 tp->t_srtt = TCPTV_SRTTBASE; 230 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << (TCP_RTTVAR_SHIFT + 2 - 1); 231 tp->t_rttmin = TCPTV_MIN; 232 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 233 TCPTV_MIN, TCPTV_REXMTMAX); 234 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 235 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 236 inp->inp_ip.ip_ttl = ip_defttl; 237 inp->inp_ppcb = (caddr_t)tp; 238 return (tp); 239 } 240 241 /* 242 * Drop a TCP connection, reporting 243 * the specified error. If connection is synchronized, 244 * then send a RST to peer. 245 */ 246 struct tcpcb * 247 tcp_drop(tp, errno) 248 register struct tcpcb *tp; 249 int errno; 250 { 251 struct socket *so = tp->t_inpcb->inp_socket; 252 253 if (TCPS_HAVERCVDSYN(tp->t_state)) { 254 tp->t_state = TCPS_CLOSED; 255 (void) tcp_output(tp); 256 tcpstat.tcps_drops++; 257 } else 258 tcpstat.tcps_conndrops++; 259 if (errno == ETIMEDOUT && tp->t_softerror) 260 errno = tp->t_softerror; 261 so->so_error = errno; 262 return (tcp_close(tp)); 263 } 264 265 /* 266 * Close a TCP control block: 267 * discard all space held by the tcp 268 * discard internet protocol block 269 * wake up any sleepers 270 */ 271 struct tcpcb * 272 tcp_close(tp) 273 register struct tcpcb *tp; 274 { 275 register struct ipqent *qe; 276 struct inpcb *inp = tp->t_inpcb; 277 struct socket *so = inp->inp_socket; 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 = 0; 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 while ((qe = tp->segq.lh_first) != NULL) { 350 LIST_REMOVE(qe, ipqe_q); 351 m_freem(qe->ipqe_m); 352 FREE(qe, M_IPQ); 353 } 354 if (tp->t_template) 355 (void) m_free(dtom(tp->t_template)); 356 free(tp, M_PCB); 357 inp->inp_ppcb = 0; 358 soisdisconnected(so); 359 in_pcbdetach(inp); 360 tcpstat.tcps_closed++; 361 return ((struct tcpcb *)0); 362 } 363 364 void 365 tcp_drain() 366 { 367 368 } 369 370 /* 371 * Notify a tcp user of an asynchronous error; 372 * store error as soft error, but wake up user 373 * (for now, won't do anything until can select for soft error). 374 */ 375 void 376 tcp_notify(inp, error) 377 struct inpcb *inp; 378 int error; 379 { 380 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 381 register struct socket *so = inp->inp_socket; 382 383 /* 384 * Ignore some errors if we are hooked up. 385 * If connection hasn't completed, has retransmitted several times, 386 * and receives a second error, give up now. This is better 387 * than waiting a long time to establish a connection that 388 * can never complete. 389 */ 390 if (tp->t_state == TCPS_ESTABLISHED && 391 (error == EHOSTUNREACH || error == ENETUNREACH || 392 error == EHOSTDOWN)) { 393 return; 394 } else if (TCPS_HAVEESTABLISHED(tp->t_state) == 0 && 395 tp->t_rxtshift > 3 && tp->t_softerror) 396 so->so_error = error; 397 else 398 tp->t_softerror = error; 399 wakeup((caddr_t) &so->so_timeo); 400 sorwakeup(so); 401 sowwakeup(so); 402 } 403 404 void * 405 tcp_ctlinput(cmd, sa, v) 406 int cmd; 407 struct sockaddr *sa; 408 register void *v; 409 { 410 register struct ip *ip = v; 411 register struct tcphdr *th; 412 extern int inetctlerrmap[]; 413 void (*notify) __P((struct inpcb *, int)) = tcp_notify; 414 int errno; 415 416 if ((unsigned)cmd >= PRC_NCMDS) 417 return NULL; 418 errno = inetctlerrmap[cmd]; 419 if (cmd == PRC_QUENCH) 420 notify = tcp_quench; 421 else if (PRC_IS_REDIRECT(cmd)) 422 notify = in_rtchange, ip = 0; 423 else if (cmd == PRC_HOSTDEAD) 424 ip = 0; 425 else if (errno == 0) 426 return NULL; 427 if (ip) { 428 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 429 in_pcbnotify(&tcbtable, sa, th->th_dport, ip->ip_src, 430 th->th_sport, errno, notify); 431 } else 432 in_pcbnotifyall(&tcbtable, sa, errno, notify); 433 return NULL; 434 } 435 436 /* 437 * When a source quench is received, close congestion window 438 * to one segment. We will gradually open it again as we proceed. 439 */ 440 void 441 tcp_quench(inp, errno) 442 struct inpcb *inp; 443 int errno; 444 { 445 struct tcpcb *tp = intotcpcb(inp); 446 447 if (tp) 448 tp->snd_cwnd = tp->t_maxseg; 449 } 450
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