1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that the above copyright notice and this paragraph are 7 * duplicated in all such forms and that any documentation, 8 * advertising materials, and other materials related to such 9 * distribution and use acknowledge that the software was developed 10 * by the University of California, Berkeley. The name of the 11 * University may not be used to endorse or promote products derived 12 * from this software without specific prior written permission. 13 * THIS SOFTWARE IS PROVIDED ``AS IS'' AND WITHOUT ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, WITHOUT LIMITATION, THE IMPLIED 15 * WARRANTIES OF MERCHANTIBILITY AND FITNESS FOR A PARTICULAR PURPOSE. 16 * 17 * @(#)tcp_subr.c 7.17 (Berkeley) 06/28/90 18 */ 19 20 #include "param.h" 21 #include "systm.h" 22 #include "malloc.h" 23 #include "mbuf.h" 24 #include "socket.h" 25 #include "socketvar.h" 26 #include "protosw.h" 27 #include "errno.h" 28 29 #include "../net/route.h" 30 #include "../net/if.h" 31 32 #include "in.h" 33 #include "in_systm.h" 34 #include "ip.h" 35 #include "in_pcb.h" 36 #include "ip_var.h" 37 #include "ip_icmp.h" 38 #include "tcp.h" 39 #include "tcp_fsm.h" 40 #include "tcp_seq.h" 41 #include "tcp_timer.h" 42 #include "tcp_var.h" 43 #include "tcpip.h" 44 45 /* patchable/settable parameters for tcp */ 46 int tcp_ttl = TCP_TTL; 47 int tcp_mssdflt = TCP_MSS; 48 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 49 50 extern struct inpcb *tcp_last_inpcb; 51 52 /* 53 * Tcp initialization 54 */ 55 tcp_init() 56 { 57 58 tcp_iss = 1; /* wrong */ 59 tcb.inp_next = tcb.inp_prev = &tcb; 60 if (max_protohdr < sizeof(struct tcpiphdr)) 61 max_protohdr = sizeof(struct tcpiphdr); 62 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 63 panic("tcp_init"); 64 } 65 66 /* 67 * Create template to be used to send tcp packets on a connection. 68 * Call after host entry created, allocates an mbuf and fills 69 * in a skeletal tcp/ip header, minimizing the amount of work 70 * necessary when the connection is used. 71 */ 72 struct tcpiphdr * 73 tcp_template(tp) 74 struct tcpcb *tp; 75 { 76 register struct inpcb *inp = tp->t_inpcb; 77 register struct mbuf *m; 78 register struct tcpiphdr *n; 79 80 if ((n = tp->t_template) == 0) { 81 m = m_get(M_DONTWAIT, MT_HEADER); 82 if (m == NULL) 83 return (0); 84 m->m_len = sizeof (struct tcpiphdr); 85 n = mtod(m, struct tcpiphdr *); 86 } 87 n->ti_next = n->ti_prev = 0; 88 n->ti_x1 = 0; 89 n->ti_pr = IPPROTO_TCP; 90 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 91 n->ti_src = inp->inp_laddr; 92 n->ti_dst = inp->inp_faddr; 93 n->ti_sport = inp->inp_lport; 94 n->ti_dport = inp->inp_fport; 95 n->ti_seq = 0; 96 n->ti_ack = 0; 97 n->ti_x2 = 0; 98 n->ti_off = 5; 99 n->ti_flags = 0; 100 n->ti_win = 0; 101 n->ti_sum = 0; 102 n->ti_urp = 0; 103 return (n); 104 } 105 106 /* 107 * Send a single message to the TCP at address specified by 108 * the given TCP/IP header. If m == 0, then we make a copy 109 * of the tcpiphdr at ti and send directly to the addressed host. 110 * This is used to force keep alive messages out using the TCP 111 * template for a connection tp->t_template. If flags are given 112 * then we send a message back to the TCP which originated the 113 * segment ti, and discard the mbuf containing it and any other 114 * attached mbufs. 115 * 116 * In any case the ack and sequence number of the transmitted 117 * segment are as specified by the parameters. 118 */ 119 tcp_respond(tp, ti, m, ack, seq, flags) 120 struct tcpcb *tp; 121 register struct tcpiphdr *ti; 122 register struct mbuf *m; 123 tcp_seq ack, seq; 124 int flags; 125 { 126 int win = 0, tlen; 127 struct route *ro = 0; 128 129 if (tp) { 130 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 131 ro = &tp->t_inpcb->inp_route; 132 } 133 if (m == 0) { 134 m = m_gethdr(M_DONTWAIT, MT_HEADER); 135 if (m == NULL) 136 return; 137 #ifdef TCP_COMPAT_42 138 tlen = 1; 139 #else 140 tlen = 0; 141 #endif 142 m->m_data += max_linkhdr; 143 *mtod(m, struct tcpiphdr *) = *ti; 144 ti = mtod(m, struct tcpiphdr *); 145 flags = TH_ACK; 146 } else { 147 m_freem(m->m_next); 148 m->m_next = 0; 149 m->m_data = (caddr_t)ti; 150 m->m_len = sizeof (struct tcpiphdr); 151 tlen = 0; 152 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 153 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 154 xchg(ti->ti_dport, ti->ti_sport, u_short); 155 #undef xchg 156 } 157 m->m_len = sizeof (struct tcpiphdr) + tlen; 158 ti->ti_next = ti->ti_prev = 0; 159 ti->ti_x1 = 0; 160 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 161 ti->ti_seq = htonl(seq); 162 ti->ti_ack = htonl(ack); 163 ti->ti_x2 = 0; 164 ti->ti_off = sizeof (struct tcphdr) >> 2; 165 ti->ti_flags = flags; 166 ti->ti_win = htons((u_short)win); 167 ti->ti_urp = 0; 168 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + tlen); 169 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + 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 struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB); 184 register struct tcpcb *tp; 185 186 if (m == NULL) 187 return ((struct tcpcb *)0); 188 tp = mtod(m, struct tcpcb *); 189 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 190 tp->t_maxseg = tcp_mssdflt; 191 192 tp->t_flags = 0; /* sends options! */ 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; 206 tp->snd_ssthresh = TCP_MAXWIN; 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 4K (default tcp_sendspace) * 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+(4096*16), tp->snd_max) && 266 (rt = inp->inp_route.ro_rt) && 267 ((struct sockaddr_in *) rt_key(rt))->sin_addr.s_addr != 268 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 (void) m_free(dtom(tp)); 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 tcp_drain() 343 { 344 345 } 346 347 /* 348 * Notify a tcp user of an asynchronous error; 349 * store error as soft error, but wake up user 350 * (for now, won't do anything until can select for soft error). 351 */ 352 tcp_notify(inp, error) 353 register struct inpcb *inp; 354 int error; 355 { 356 357 ((struct tcpcb *)inp->inp_ppcb)->t_softerror = error; 358 wakeup((caddr_t) &inp->inp_socket->so_timeo); 359 sorwakeup(inp->inp_socket); 360 sowwakeup(inp->inp_socket); 361 } 362 363 tcp_ctlinput(cmd, sa, ip) 364 int cmd; 365 struct sockaddr *sa; 366 register struct ip *ip; 367 { 368 register struct tcphdr *th; 369 extern struct in_addr zeroin_addr; 370 extern u_char inetctlerrmap[]; 371 int (*notify)() = tcp_notify, tcp_quench(); 372 373 if (cmd == PRC_QUENCH) 374 notify = tcp_quench; 375 else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0) 376 return; 377 if (ip) { 378 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 379 in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport, 380 cmd, notify); 381 } else 382 in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify); 383 } 384 385 /* 386 * When a source quench is received, close congestion window 387 * to one segment. We will gradually open it again as we proceed. 388 */ 389 tcp_quench(inp) 390 struct inpcb *inp; 391 { 392 struct tcpcb *tp = intotcpcb(inp); 393 394 if (tp) 395 tp->snd_cwnd = tp->t_maxseg; 396 } 397