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 7.18 (Berkeley) 06/28/90 8 */ 9 10 #include "param.h" 11 #include "systm.h" 12 #include "malloc.h" 13 #include "mbuf.h" 14 #include "socket.h" 15 #include "socketvar.h" 16 #include "protosw.h" 17 #include "errno.h" 18 19 #include "../net/route.h" 20 #include "../net/if.h" 21 22 #include "in.h" 23 #include "in_systm.h" 24 #include "ip.h" 25 #include "in_pcb.h" 26 #include "ip_var.h" 27 #include "ip_icmp.h" 28 #include "tcp.h" 29 #include "tcp_fsm.h" 30 #include "tcp_seq.h" 31 #include "tcp_timer.h" 32 #include "tcp_var.h" 33 #include "tcpip.h" 34 35 /* patchable/settable parameters for tcp */ 36 int tcp_ttl = TCP_TTL; 37 int tcp_mssdflt = TCP_MSS; 38 int tcp_rttdflt = TCPTV_SRTTDFLT / PR_SLOWHZ; 39 40 extern struct inpcb *tcp_last_inpcb; 41 42 /* 43 * Tcp initialization 44 */ 45 tcp_init() 46 { 47 48 tcp_iss = 1; /* wrong */ 49 tcb.inp_next = tcb.inp_prev = &tcb; 50 if (max_protohdr < sizeof(struct tcpiphdr)) 51 max_protohdr = sizeof(struct tcpiphdr); 52 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 53 panic("tcp_init"); 54 } 55 56 /* 57 * Create template to be used to send tcp packets on a connection. 58 * Call after host entry created, allocates an mbuf and fills 59 * in a skeletal tcp/ip header, minimizing the amount of work 60 * necessary when the connection is used. 61 */ 62 struct tcpiphdr * 63 tcp_template(tp) 64 struct tcpcb *tp; 65 { 66 register struct inpcb *inp = tp->t_inpcb; 67 register struct mbuf *m; 68 register struct tcpiphdr *n; 69 70 if ((n = tp->t_template) == 0) { 71 m = m_get(M_DONTWAIT, MT_HEADER); 72 if (m == NULL) 73 return (0); 74 m->m_len = sizeof (struct tcpiphdr); 75 n = mtod(m, struct tcpiphdr *); 76 } 77 n->ti_next = n->ti_prev = 0; 78 n->ti_x1 = 0; 79 n->ti_pr = IPPROTO_TCP; 80 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 81 n->ti_src = inp->inp_laddr; 82 n->ti_dst = inp->inp_faddr; 83 n->ti_sport = inp->inp_lport; 84 n->ti_dport = inp->inp_fport; 85 n->ti_seq = 0; 86 n->ti_ack = 0; 87 n->ti_x2 = 0; 88 n->ti_off = 5; 89 n->ti_flags = 0; 90 n->ti_win = 0; 91 n->ti_sum = 0; 92 n->ti_urp = 0; 93 return (n); 94 } 95 96 /* 97 * Send a single message to the TCP at address specified by 98 * the given TCP/IP header. If m == 0, then we make a copy 99 * of the tcpiphdr at ti and send directly to the addressed host. 100 * This is used to force keep alive messages out using the TCP 101 * template for a connection tp->t_template. If flags are given 102 * then we send a message back to the TCP which originated the 103 * segment ti, and discard the mbuf containing it and any other 104 * attached mbufs. 105 * 106 * In any case the ack and sequence number of the transmitted 107 * segment are as specified by the parameters. 108 */ 109 tcp_respond(tp, ti, m, ack, seq, flags) 110 struct tcpcb *tp; 111 register struct tcpiphdr *ti; 112 register struct mbuf *m; 113 tcp_seq ack, seq; 114 int flags; 115 { 116 int win = 0, tlen; 117 struct route *ro = 0; 118 119 if (tp) { 120 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 121 ro = &tp->t_inpcb->inp_route; 122 } 123 if (m == 0) { 124 m = m_gethdr(M_DONTWAIT, MT_HEADER); 125 if (m == NULL) 126 return; 127 #ifdef TCP_COMPAT_42 128 tlen = 1; 129 #else 130 tlen = 0; 131 #endif 132 m->m_data += max_linkhdr; 133 *mtod(m, struct tcpiphdr *) = *ti; 134 ti = mtod(m, struct tcpiphdr *); 135 flags = TH_ACK; 136 } else { 137 m_freem(m->m_next); 138 m->m_next = 0; 139 m->m_data = (caddr_t)ti; 140 m->m_len = sizeof (struct tcpiphdr); 141 tlen = 0; 142 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 143 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 144 xchg(ti->ti_dport, ti->ti_sport, u_short); 145 #undef xchg 146 } 147 m->m_len = sizeof (struct tcpiphdr) + tlen; 148 ti->ti_next = ti->ti_prev = 0; 149 ti->ti_x1 = 0; 150 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 151 ti->ti_seq = htonl(seq); 152 ti->ti_ack = htonl(ack); 153 ti->ti_x2 = 0; 154 ti->ti_off = sizeof (struct tcphdr) >> 2; 155 ti->ti_flags = flags; 156 ti->ti_win = htons((u_short)win); 157 ti->ti_urp = 0; 158 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + tlen); 159 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + tlen; 160 ((struct ip *)ti)->ip_ttl = tcp_ttl; 161 (void) ip_output(m, (struct mbuf *)0, ro, 0); 162 } 163 164 /* 165 * Create a new TCP control block, making an 166 * empty reassembly queue and hooking it to the argument 167 * protocol control block. 168 */ 169 struct tcpcb * 170 tcp_newtcpcb(inp) 171 struct inpcb *inp; 172 { 173 struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB); 174 register struct tcpcb *tp; 175 176 if (m == NULL) 177 return ((struct tcpcb *)0); 178 tp = mtod(m, struct tcpcb *); 179 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 180 tp->t_maxseg = tcp_mssdflt; 181 182 tp->t_flags = 0; /* sends options! */ 183 tp->t_inpcb = inp; 184 /* 185 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 186 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 187 * reasonable initial retransmit time. 188 */ 189 tp->t_srtt = TCPTV_SRTTBASE; 190 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << 2; 191 tp->t_rttmin = TCPTV_MIN; 192 TCPT_RANGESET(tp->t_rxtcur, 193 ((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1, 194 TCPTV_MIN, TCPTV_REXMTMAX); 195 tp->snd_cwnd = TCP_MAXWIN; 196 tp->snd_ssthresh = TCP_MAXWIN; 197 inp->inp_ip.ip_ttl = tcp_ttl; 198 inp->inp_ppcb = (caddr_t)tp; 199 return (tp); 200 } 201 202 /* 203 * Drop a TCP connection, reporting 204 * the specified error. If connection is synchronized, 205 * then send a RST to peer. 206 */ 207 struct tcpcb * 208 tcp_drop(tp, errno) 209 register struct tcpcb *tp; 210 int errno; 211 { 212 struct socket *so = tp->t_inpcb->inp_socket; 213 214 if (TCPS_HAVERCVDSYN(tp->t_state)) { 215 tp->t_state = TCPS_CLOSED; 216 (void) tcp_output(tp); 217 tcpstat.tcps_drops++; 218 } else 219 tcpstat.tcps_conndrops++; 220 if (errno == ETIMEDOUT && tp->t_softerror) 221 errno = tp->t_softerror; 222 so->so_error = errno; 223 return (tcp_close(tp)); 224 } 225 226 /* 227 * Close a TCP control block: 228 * discard all space held by the tcp 229 * discard internet protocol block 230 * wake up any sleepers 231 */ 232 struct tcpcb * 233 tcp_close(tp) 234 register struct tcpcb *tp; 235 { 236 register struct tcpiphdr *t; 237 struct inpcb *inp = tp->t_inpcb; 238 struct socket *so = inp->inp_socket; 239 register struct mbuf *m; 240 #ifdef RTV_RTT 241 register struct rtentry *rt; 242 243 /* 244 * If we sent enough data to get some meaningful characteristics, 245 * save them in the routing entry. 'Enough' is arbitrarily 246 * defined as 4K (default tcp_sendspace) * 16. This would 247 * give us 16 rtt samples assuming we only get one sample per 248 * window (the usual case on a long haul net). 16 samples is 249 * enough for the srtt filter to converge to within 5% of the correct 250 * value; fewer samples and we could save a very bogus rtt. 251 * 252 * Don't update the default route's characteristics and don't 253 * update anything that the user "locked". 254 */ 255 if (SEQ_LT(tp->iss+(4096*16), tp->snd_max) && 256 (rt = inp->inp_route.ro_rt) && 257 ((struct sockaddr_in *) rt_key(rt))->sin_addr.s_addr != 258 INADDR_ANY) { 259 register u_long i; 260 261 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 262 i = tp->t_srtt * 263 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 264 if (rt->rt_rmx.rmx_rtt && i) 265 /* 266 * filter this update to half the old & half 267 * the new values, converting scale. 268 * See route.h and tcp_var.h for a 269 * description of the scaling constants. 270 */ 271 rt->rt_rmx.rmx_rtt = 272 (rt->rt_rmx.rmx_rtt + i) / 2; 273 else 274 rt->rt_rmx.rmx_rtt = i; 275 } 276 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 277 i = tp->t_rttvar * 278 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 279 if (rt->rt_rmx.rmx_rttvar && i) 280 rt->rt_rmx.rmx_rttvar = 281 (rt->rt_rmx.rmx_rttvar + i) / 2; 282 else 283 rt->rt_rmx.rmx_rttvar = i; 284 } 285 /* 286 * update the pipelimit (ssthresh) if it has been updated 287 * already or if a pipesize was specified & the threshhold 288 * got below half the pipesize. I.e., wait for bad news 289 * before we start updating, then update on both good 290 * and bad news. 291 */ 292 if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 293 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh || 294 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 295 /* 296 * convert the limit from user data bytes to 297 * packets then to packet data bytes. 298 */ 299 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 300 if (i < 2) 301 i = 2; 302 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 303 if (rt->rt_rmx.rmx_ssthresh) 304 rt->rt_rmx.rmx_ssthresh = 305 (rt->rt_rmx.rmx_ssthresh + i) / 2; 306 else 307 rt->rt_rmx.rmx_ssthresh = i; 308 } 309 } 310 #endif RTV_RTT 311 /* free the reassembly queue, if any */ 312 t = tp->seg_next; 313 while (t != (struct tcpiphdr *)tp) { 314 t = (struct tcpiphdr *)t->ti_next; 315 m = REASS_MBUF((struct tcpiphdr *)t->ti_prev); 316 remque(t->ti_prev); 317 m_freem(m); 318 } 319 if (tp->t_template) 320 (void) m_free(dtom(tp->t_template)); 321 (void) m_free(dtom(tp)); 322 inp->inp_ppcb = 0; 323 soisdisconnected(so); 324 /* clobber input pcb cache if we're closing the cached connection */ 325 if (inp == tcp_last_inpcb) 326 tcp_last_inpcb = &tcb; 327 in_pcbdetach(inp); 328 tcpstat.tcps_closed++; 329 return ((struct tcpcb *)0); 330 } 331 332 tcp_drain() 333 { 334 335 } 336 337 /* 338 * Notify a tcp user of an asynchronous error; 339 * store error as soft error, but wake up user 340 * (for now, won't do anything until can select for soft error). 341 */ 342 tcp_notify(inp, error) 343 register struct inpcb *inp; 344 int error; 345 { 346 347 ((struct tcpcb *)inp->inp_ppcb)->t_softerror = error; 348 wakeup((caddr_t) &inp->inp_socket->so_timeo); 349 sorwakeup(inp->inp_socket); 350 sowwakeup(inp->inp_socket); 351 } 352 353 tcp_ctlinput(cmd, sa, ip) 354 int cmd; 355 struct sockaddr *sa; 356 register struct ip *ip; 357 { 358 register struct tcphdr *th; 359 extern struct in_addr zeroin_addr; 360 extern u_char inetctlerrmap[]; 361 int (*notify)() = tcp_notify, tcp_quench(); 362 363 if (cmd == PRC_QUENCH) 364 notify = tcp_quench; 365 else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0) 366 return; 367 if (ip) { 368 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 369 in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport, 370 cmd, notify); 371 } else 372 in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify); 373 } 374 375 /* 376 * When a source quench is received, close congestion window 377 * to one segment. We will gradually open it again as we proceed. 378 */ 379 tcp_quench(inp) 380 struct inpcb *inp; 381 { 382 struct tcpcb *tp = intotcpcb(inp); 383 384 if (tp) 385 tp->snd_cwnd = tp->t_maxseg; 386 } 387