1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California. 3 * All rights reserved. 4 * 5 * %sccs.include.redist.c% 6 * 7 * @(#)tcp_subr.c 7.25 (Berkeley) 01/08/93 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_ttl = TCP_TTL; 38 int tcp_mssdflt = TCP_MSS; 39 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 40 int tcp_do_rfc1323 = 1; 41 42 extern struct inpcb *tcp_last_inpcb; 43 44 /* 45 * Tcp initialization 46 */ 47 tcp_init() 48 { 49 50 tcp_iss = 1; /* wrong */ 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 tcp_respond(tp, ti, m, ack, seq, flags) 112 struct tcpcb *tp; 113 register struct tcpiphdr *ti; 114 register struct mbuf *m; 115 tcp_seq ack, seq; 116 int flags; 117 { 118 register int tlen; 119 int win = 0; 120 struct route *ro = 0; 121 122 if (tp) { 123 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 124 ro = &tp->t_inpcb->inp_route; 125 } 126 if (m == 0) { 127 m = m_gethdr(M_DONTWAIT, MT_HEADER); 128 if (m == NULL) 129 return; 130 #ifdef TCP_COMPAT_42 131 tlen = 1; 132 #else 133 tlen = 0; 134 #endif 135 m->m_data += max_linkhdr; 136 *mtod(m, struct tcpiphdr *) = *ti; 137 ti = mtod(m, struct tcpiphdr *); 138 flags = TH_ACK; 139 } else { 140 m_freem(m->m_next); 141 m->m_next = 0; 142 m->m_data = (caddr_t)ti; 143 m->m_len = sizeof (struct tcpiphdr); 144 tlen = 0; 145 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 146 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 147 xchg(ti->ti_dport, ti->ti_sport, u_short); 148 #undef xchg 149 } 150 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 151 tlen += sizeof (struct tcpiphdr); 152 m->m_len = tlen; 153 m->m_pkthdr.len = tlen; 154 m->m_pkthdr.rcvif = (struct ifnet *) 0; 155 ti->ti_next = ti->ti_prev = 0; 156 ti->ti_x1 = 0; 157 ti->ti_seq = htonl(seq); 158 ti->ti_ack = htonl(ack); 159 ti->ti_x2 = 0; 160 ti->ti_off = sizeof (struct tcphdr) >> 2; 161 ti->ti_flags = flags; 162 if (tp) 163 ti->ti_win = htons((u_short) (win >> tp->rcv_scale)); 164 else 165 ti->ti_win = htons((u_short)win); 166 ti->ti_urp = 0; 167 ti->ti_sum = 0; 168 ti->ti_sum = in_cksum(m, tlen); 169 ((struct ip *)ti)->ip_len = tlen; 170 ((struct ip *)ti)->ip_ttl = tcp_ttl; 171 (void) ip_output(m, (struct mbuf *)0, ro, 0); 172 } 173 174 /* 175 * Create a new TCP control block, making an 176 * empty reassembly queue and hooking it to the argument 177 * protocol control block. 178 */ 179 struct tcpcb * 180 tcp_newtcpcb(inp) 181 struct inpcb *inp; 182 { 183 register struct tcpcb *tp; 184 185 tp = malloc(sizeof(*tp), M_PCB, M_NOWAIT); 186 if (tp == NULL) 187 return ((struct tcpcb *)0); 188 bzero((char *) tp, sizeof(struct tcpcb)); 189 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 190 tp->t_maxseg = tcp_mssdflt; 191 192 tp->t_flags = tcp_do_rfc1323 ? (TF_REQ_SCALE|TF_REQ_TSTMP) : 0; 193 tp->t_inpcb = inp; 194 /* 195 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 196 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 197 * reasonable initial retransmit time. 198 */ 199 tp->t_srtt = TCPTV_SRTTBASE; 200 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << 2; 201 tp->t_rttmin = TCPTV_MIN; 202 TCPT_RANGESET(tp->t_rxtcur, 203 ((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1, 204 TCPTV_MIN, TCPTV_REXMTMAX); 205 tp->snd_cwnd = TCP_MAXWIN << TCP_MAX_WINSHIFT; 206 tp->snd_ssthresh = TCP_MAXWIN << TCP_MAX_WINSHIFT; 207 inp->inp_ip.ip_ttl = tcp_ttl; 208 inp->inp_ppcb = (caddr_t)tp; 209 return (tp); 210 } 211 212 /* 213 * Drop a TCP connection, reporting 214 * the specified error. If connection is synchronized, 215 * then send a RST to peer. 216 */ 217 struct tcpcb * 218 tcp_drop(tp, errno) 219 register struct tcpcb *tp; 220 int errno; 221 { 222 struct socket *so = tp->t_inpcb->inp_socket; 223 224 if (TCPS_HAVERCVDSYN(tp->t_state)) { 225 tp->t_state = TCPS_CLOSED; 226 (void) tcp_output(tp); 227 tcpstat.tcps_drops++; 228 } else 229 tcpstat.tcps_conndrops++; 230 if (errno == ETIMEDOUT && tp->t_softerror) 231 errno = tp->t_softerror; 232 so->so_error = errno; 233 return (tcp_close(tp)); 234 } 235 236 /* 237 * Close a TCP control block: 238 * discard all space held by the tcp 239 * discard internet protocol block 240 * wake up any sleepers 241 */ 242 struct tcpcb * 243 tcp_close(tp) 244 register struct tcpcb *tp; 245 { 246 register struct tcpiphdr *t; 247 struct inpcb *inp = tp->t_inpcb; 248 struct socket *so = inp->inp_socket; 249 register struct mbuf *m; 250 #ifdef RTV_RTT 251 register struct rtentry *rt; 252 253 /* 254 * If we sent enough data to get some meaningful characteristics, 255 * save them in the routing entry. 'Enough' is arbitrarily 256 * defined as the sendpipesize (default 4K) * 16. This would 257 * give us 16 rtt samples assuming we only get one sample per 258 * window (the usual case on a long haul net). 16 samples is 259 * enough for the srtt filter to converge to within 5% of the correct 260 * value; fewer samples and we could save a very bogus rtt. 261 * 262 * Don't update the default route's characteristics and don't 263 * update anything that the user "locked". 264 */ 265 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) && 266 (rt = inp->inp_route.ro_rt) && 267 ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) { 268 register u_long i; 269 270 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 271 i = tp->t_srtt * 272 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 273 if (rt->rt_rmx.rmx_rtt && i) 274 /* 275 * filter this update to half the old & half 276 * the new values, converting scale. 277 * See route.h and tcp_var.h for a 278 * description of the scaling constants. 279 */ 280 rt->rt_rmx.rmx_rtt = 281 (rt->rt_rmx.rmx_rtt + i) / 2; 282 else 283 rt->rt_rmx.rmx_rtt = i; 284 } 285 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 286 i = tp->t_rttvar * 287 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 288 if (rt->rt_rmx.rmx_rttvar && i) 289 rt->rt_rmx.rmx_rttvar = 290 (rt->rt_rmx.rmx_rttvar + i) / 2; 291 else 292 rt->rt_rmx.rmx_rttvar = i; 293 } 294 /* 295 * update the pipelimit (ssthresh) if it has been updated 296 * already or if a pipesize was specified & the threshhold 297 * got below half the pipesize. I.e., wait for bad news 298 * before we start updating, then update on both good 299 * and bad news. 300 */ 301 if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 302 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh || 303 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 304 /* 305 * convert the limit from user data bytes to 306 * packets then to packet data bytes. 307 */ 308 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 309 if (i < 2) 310 i = 2; 311 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 312 if (rt->rt_rmx.rmx_ssthresh) 313 rt->rt_rmx.rmx_ssthresh = 314 (rt->rt_rmx.rmx_ssthresh + i) / 2; 315 else 316 rt->rt_rmx.rmx_ssthresh = i; 317 } 318 } 319 #endif RTV_RTT 320 /* free the reassembly queue, if any */ 321 t = tp->seg_next; 322 while (t != (struct tcpiphdr *)tp) { 323 t = (struct tcpiphdr *)t->ti_next; 324 m = REASS_MBUF((struct tcpiphdr *)t->ti_prev); 325 remque(t->ti_prev); 326 m_freem(m); 327 } 328 if (tp->t_template) 329 (void) m_free(dtom(tp->t_template)); 330 free(tp, M_PCB); 331 inp->inp_ppcb = 0; 332 soisdisconnected(so); 333 /* clobber input pcb cache if we're closing the cached connection */ 334 if (inp == tcp_last_inpcb) 335 tcp_last_inpcb = &tcb; 336 in_pcbdetach(inp); 337 tcpstat.tcps_closed++; 338 return ((struct tcpcb *)0); 339 } 340 341 tcp_drain() 342 { 343 344 } 345 346 /* 347 * Notify a tcp user of an asynchronous error; 348 * store error as soft error, but wake up user 349 * (for now, won't do anything until can select for soft error). 350 */ 351 tcp_notify(inp, error) 352 struct inpcb *inp; 353 int error; 354 { 355 register struct tcpcb *tp = (struct tcpcb *)inp->inp_ppcb; 356 register struct socket *so = inp->inp_socket; 357 358 /* 359 * Ignore some errors if we are hooked up. 360 * If connection hasn't completed, has retransmitted several times, 361 * and receives a second error, give up now. This is better 362 * than waiting a long time to establish a connection that 363 * can never complete. 364 */ 365 if (tp->t_state == TCPS_ESTABLISHED && 366 (error == EHOSTUNREACH || error == ENETUNREACH || 367 error == EHOSTDOWN)) { 368 return; 369 } else if (tp->t_state < TCPS_ESTABLISHED && tp->t_rxtshift > 3 && 370 tp->t_softerror) 371 so->so_error = error; 372 else 373 tp->t_softerror = error; 374 wakeup((caddr_t) &so->so_timeo); 375 sorwakeup(so); 376 sowwakeup(so); 377 } 378 379 tcp_ctlinput(cmd, sa, ip) 380 int cmd; 381 struct sockaddr *sa; 382 register struct ip *ip; 383 { 384 register struct tcphdr *th; 385 extern struct in_addr zeroin_addr; 386 extern u_char inetctlerrmap[]; 387 int (*notify)() = tcp_notify, tcp_quench(); 388 389 if (cmd == PRC_QUENCH) 390 notify = tcp_quench; 391 else if (!PRC_IS_REDIRECT(cmd) && 392 ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0)) 393 return; 394 if (ip) { 395 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 396 in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport, 397 cmd, notify); 398 } else 399 in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify); 400 } 401 402 /* 403 * When a source quench is received, close congestion window 404 * to one segment. We will gradually open it again as we proceed. 405 */ 406 tcp_quench(inp) 407 struct inpcb *inp; 408 { 409 struct tcpcb *tp = intotcpcb(inp); 410 411 if (tp) 412 tp->snd_cwnd = tp->t_maxseg; 413 } 414