1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1995 3 * The Regents of the University of California. All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)tcp_subr.c 8.2 (Berkeley) 05/24/95 8 */ 9 10 #include <sys/param.h> 11 #include <sys/proc.h> 12 #include <sys/systm.h> 13 #include <sys/malloc.h> 14 #include <sys/mbuf.h> 15 #include <sys/socket.h> 16 #include <sys/socketvar.h> 17 #include <sys/protosw.h> 18 #include <sys/errno.h> 19 20 #include <net/route.h> 21 #include <net/if.h> 22 23 #include <netinet/in.h> 24 #include <netinet/in_systm.h> 25 #include <netinet/ip.h> 26 #include <netinet/in_pcb.h> 27 #include <netinet/ip_var.h> 28 #include <netinet/ip_icmp.h> 29 #include <netinet/tcp.h> 30 #include <netinet/tcp_fsm.h> 31 #include <netinet/tcp_seq.h> 32 #include <netinet/tcp_timer.h> 33 #include <netinet/tcp_var.h> 34 #include <netinet/tcpip.h> 35 36 /* patchable/settable parameters for tcp */ 37 int tcp_mssdflt = TCP_MSS; 38 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 39 int tcp_do_rfc1323 = 1; 40 41 extern struct inpcb *tcp_last_inpcb; 42 43 /* 44 * Tcp initialization 45 */ 46 void 47 tcp_init() 48 { 49 50 tcp_iss = random(); /* wrong, but better than a constant */ 51 tcb.inp_next = tcb.inp_prev = &tcb; 52 if (max_protohdr < sizeof(struct tcpiphdr)) 53 max_protohdr = sizeof(struct tcpiphdr); 54 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 55 panic("tcp_init"); 56 } 57 58 /* 59 * Create template to be used to send tcp packets on a connection. 60 * Call after host entry created, allocates an mbuf and fills 61 * in a skeletal tcp/ip header, minimizing the amount of work 62 * necessary when the connection is used. 63 */ 64 struct tcpiphdr * 65 tcp_template(tp) 66 struct tcpcb *tp; 67 { 68 register struct inpcb *inp = tp->t_inpcb; 69 register struct mbuf *m; 70 register struct tcpiphdr *n; 71 72 if ((n = tp->t_template) == 0) { 73 m = m_get(M_DONTWAIT, MT_HEADER); 74 if (m == NULL) 75 return (0); 76 m->m_len = sizeof (struct tcpiphdr); 77 n = mtod(m, struct tcpiphdr *); 78 } 79 n->ti_next = n->ti_prev = 0; 80 n->ti_x1 = 0; 81 n->ti_pr = IPPROTO_TCP; 82 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 83 n->ti_src = inp->inp_laddr; 84 n->ti_dst = inp->inp_faddr; 85 n->ti_sport = inp->inp_lport; 86 n->ti_dport = inp->inp_fport; 87 n->ti_seq = 0; 88 n->ti_ack = 0; 89 n->ti_x2 = 0; 90 n->ti_off = 5; 91 n->ti_flags = 0; 92 n->ti_win = 0; 93 n->ti_sum = 0; 94 n->ti_urp = 0; 95 return (n); 96 } 97 98 /* 99 * Send a single message to the TCP at address specified by 100 * the given TCP/IP header. If m == 0, then we make a copy 101 * of the tcpiphdr at ti and send directly to the addressed host. 102 * This is used to force keep alive messages out using the TCP 103 * template for a connection tp->t_template. If flags are given 104 * then we send a message back to the TCP which originated the 105 * segment ti, and discard the mbuf containing it and any other 106 * attached mbufs. 107 * 108 * In any case the ack and sequence number of the transmitted 109 * segment are as specified by the parameters. 110 */ 111 void 112 tcp_respond(tp, ti, m, ack, seq, flags) 113 struct tcpcb *tp; 114 register struct tcpiphdr *ti; 115 register struct mbuf *m; 116 tcp_seq ack, seq; 117 int flags; 118 { 119 register int tlen; 120 int win = 0; 121 struct route *ro = 0; 122 123 if (tp) { 124 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 125 ro = &tp->t_inpcb->inp_route; 126 } 127 if (m == 0) { 128 m = m_gethdr(M_DONTWAIT, MT_HEADER); 129 if (m == NULL) 130 return; 131 #ifdef TCP_COMPAT_42 132 tlen = 1; 133 #else 134 tlen = 0; 135 #endif 136 m->m_data += max_linkhdr; 137 *mtod(m, struct tcpiphdr *) = *ti; 138 ti = mtod(m, struct tcpiphdr *); 139 flags = TH_ACK; 140 } else { 141 m_freem(m->m_next); 142 m->m_next = 0; 143 m->m_data = (caddr_t)ti; 144 m->m_len = sizeof (struct tcpiphdr); 145 tlen = 0; 146 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 147 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 148 xchg(ti->ti_dport, ti->ti_sport, u_short); 149 #undef xchg 150 } 151 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 152 tlen += sizeof (struct tcpiphdr); 153 m->m_len = tlen; 154 m->m_pkthdr.len = tlen; 155 m->m_pkthdr.rcvif = (struct ifnet *) 0; 156 ti->ti_next = ti->ti_prev = 0; 157 ti->ti_x1 = 0; 158 ti->ti_seq = htonl(seq); 159 ti->ti_ack = htonl(ack); 160 ti->ti_x2 = 0; 161 ti->ti_off = sizeof (struct tcphdr) >> 2; 162 ti->ti_flags = flags; 163 if (tp) 164 ti->ti_win = htons((u_short) (win >> tp->rcv_scale)); 165 else 166 ti->ti_win = htons((u_short)win); 167 ti->ti_urp = 0; 168 ti->ti_sum = 0; 169 ti->ti_sum = in_cksum(m, tlen); 170 ((struct ip *)ti)->ip_len = tlen; 171 ((struct ip *)ti)->ip_ttl = ip_defttl; 172 (void) ip_output(m, NULL, ro, 0, NULL); 173 } 174 175 /* 176 * Create a new TCP control block, making an 177 * empty reassembly queue and hooking it to the argument 178 * protocol control block. 179 */ 180 struct tcpcb * 181 tcp_newtcpcb(inp) 182 struct inpcb *inp; 183 { 184 register struct tcpcb *tp; 185 186 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT); 187 if (tp == NULL) 188 return ((struct tcpcb *)0); 189 bzero((char *) tp, sizeof(struct tcpcb)); 190 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 191 tp->t_maxseg = tcp_mssdflt; 192 193 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 194 tp->t_inpcb = inp; 195 /* 196 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 197 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 198 * reasonable initial retransmit time. 199 */ 200 tp->t_srtt = TCPTV_SRTTBASE; 201 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << 2; 202 tp->t_rttmin = TCPTV_MIN; 203 TCPT_RANGESET(tp->t_rxtcur, 204 ((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1, 205 TCPTV_MIN, TCPTV_REXMTMAX); 206 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 207 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 208 inp->inp_ip.ip_ttl = ip_defttl; 209 inp->inp_ppcb = (caddr_t)tp; 210 return (tp); 211 } 212 213 /* 214 * Drop a TCP connection, reporting 215 * the specified error. If connection is synchronized, 216 * then send a RST to peer. 217 */ 218 struct tcpcb * 219 tcp_drop(tp, errno) 220 register struct tcpcb *tp; 221 int errno; 222 { 223 struct socket *so = tp->t_inpcb->inp_socket; 224 225 if (TCPS_HAVERCVDSYN(tp->t_state)) { 226 tp->t_state = TCPS_CLOSED; 227 (void) tcp_output(tp); 228 tcpstat.tcps_drops++; 229 } else 230 tcpstat.tcps_conndrops++; 231 if (errno == ETIMEDOUT && tp->t_softerror) 232 errno = tp->t_softerror; 233 so->so_error = errno; 234 return (tcp_close(tp)); 235 } 236 237 /* 238 * Close a TCP control block: 239 * discard all space held by the tcp 240 * discard internet protocol block 241 * wake up any sleepers 242 */ 243 struct tcpcb * 244 tcp_close(tp) 245 register struct tcpcb *tp; 246 { 247 register struct tcpiphdr *t; 248 struct inpcb *inp = tp->t_inpcb; 249 struct socket *so = inp->inp_socket; 250 register struct mbuf *m; 251 #ifdef RTV_RTT 252 register struct rtentry *rt; 253 254 /* 255 * If we sent enough data to get some meaningful characteristics, 256 * save them in the routing entry. 'Enough' is arbitrarily 257 * defined as the sendpipesize (default 4K) * 16. This would 258 * give us 16 rtt samples assuming we only get one sample per 259 * window (the usual case on a long haul net). 16 samples is 260 * enough for the srtt filter to converge to within 5% of the correct 261 * value; fewer samples and we could save a very bogus rtt. 262 * 263 * Don't update the default route's characteristics and don't 264 * update anything that the user "locked". 265 */ 266 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) && 267 (rt = inp->inp_route.ro_rt) && 268 ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) { 269 register u_long i; 270 271 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 272 i = tp->t_srtt * 273 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 274 if (rt->rt_rmx.rmx_rtt && i) 275 /* 276 * filter this update to half the old & half 277 * the new values, converting scale. 278 * See route.h and tcp_var.h for a 279 * description of the scaling constants. 280 */ 281 rt->rt_rmx.rmx_rtt = 282 (rt->rt_rmx.rmx_rtt + i) / 2; 283 else 284 rt->rt_rmx.rmx_rtt = i; 285 } 286 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 287 i = tp->t_rttvar * 288 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 289 if (rt->rt_rmx.rmx_rttvar && i) 290 rt->rt_rmx.rmx_rttvar = 291 (rt->rt_rmx.rmx_rttvar + i) / 2; 292 else 293 rt->rt_rmx.rmx_rttvar = i; 294 } 295 /* 296 * update the pipelimit (ssthresh) if it has been updated 297 * already or if a pipesize was specified & the threshhold 298 * got below half the pipesize. I.e., wait for bad news 299 * before we start updating, then update on both good 300 * and bad news. 301 */ 302 if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 303 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh || 304 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 305 /* 306 * convert the limit from user data bytes to 307 * packets then to packet data bytes. 308 */ 309 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 310 if (i < 2) 311 i = 2; 312 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 313 if (rt->rt_rmx.rmx_ssthresh) 314 rt->rt_rmx.rmx_ssthresh = 315 (rt->rt_rmx.rmx_ssthresh + i) / 2; 316 else 317 rt->rt_rmx.rmx_ssthresh = i; 318 } 319 } 320 #endif /* RTV_RTT */ 321 /* free the reassembly queue, if any */ 322 t = tp->seg_next; 323 while (t != (struct tcpiphdr *)tp) { 324 t = (struct tcpiphdr *)t->ti_next; 325 m = REASS_MBUF((struct tcpiphdr *)t->ti_prev); 326 remque(t->ti_prev); 327 m_freem(m); 328 } 329 if (tp->t_template) 330 (void) m_free(dtom(tp->t_template)); 331 free(tp, M_PCB); 332 inp->inp_ppcb = 0; 333 soisdisconnected(so); 334 /* clobber input pcb cache if we're closing the cached connection */ 335 if (inp == tcp_last_inpcb) 336 tcp_last_inpcb = &tcb; 337 in_pcbdetach(inp); 338 tcpstat.tcps_closed++; 339 return ((struct tcpcb *)0); 340 } 341 342 void 343 tcp_drain() 344 { 345 346 } 347 348 /* 349 * Notify a tcp user of an asynchronous error; 350 * store error as soft error, but wake up user 351 * (for now, won't do anything until can select for soft error). 352 */ 353 void 354 tcp_notify(inp, error) 355 struct inpcb *inp; 356 int error; 357 { 358 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 359 register struct socket *so = inp->inp_socket; 360 361 /* 362 * Ignore some errors if we are hooked up. 363 * If connection hasn't completed, has retransmitted several times, 364 * and receives a second error, give up now. This is better 365 * than waiting a long time to establish a connection that 366 * can never complete. 367 */ 368 if (tp->t_state == TCPS_ESTABLISHED && 369 (error == EHOSTUNREACH || error == ENETUNREACH || 370 error == EHOSTDOWN)) { 371 return; 372 } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 && 373 tp->t_softerror) 374 so->so_error = error; 375 else 376 tp->t_softerror = error; 377 wakeup((caddr_t) &so->so_timeo); 378 sorwakeup(so); 379 sowwakeup(so); 380 } 381 382 void 383 tcp_ctlinput(cmd, sa, ip) 384 int cmd; 385 struct sockaddr *sa; 386 register struct ip *ip; 387 { 388 register struct tcphdr *th; 389 extern struct in_addr zeroin_addr; 390 extern u_char inetctlerrmap[]; 391 void (*notify) __P((struct inpcb *, int)) = tcp_notify; 392 393 if (cmd == PRC_QUENCH) 394 notify = tcp_quench; 395 else if (!PRC_IS_REDIRECT(cmd) && 396 ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0)) 397 return; 398 if (ip) { 399 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 400 in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport, 401 cmd, notify); 402 } else 403 in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify); 404 } 405 406 /* 407 * When a source quench is received, close congestion window 408 * to one segment. We will gradually open it again as we proceed. 409 */ 410 void 411 tcp_quench(inp, errno) 412 struct inpcb *inp; 413 int errno; 414 { 415 struct tcpcb *tp = intotcpcb(inp); 416 417 if (tp) 418 tp->snd_cwnd = tp->t_maxseg; 419 } 420