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 7.21 (Berkeley) 02/15/92 8 */ 9 10 #include "param.h" 11 #include "proc.h" 12 #include "systm.h" 13 #include "malloc.h" 14 #include "mbuf.h" 15 #include "socket.h" 16 #include "socketvar.h" 17 #include "protosw.h" 18 #include "errno.h" 19 20 #include "../net/route.h" 21 #include "../net/if.h" 22 23 #include "in.h" 24 #include "in_systm.h" 25 #include "ip.h" 26 #include "in_pcb.h" 27 #include "ip_var.h" 28 #include "ip_icmp.h" 29 #include "tcp.h" 30 #include "tcp_fsm.h" 31 #include "tcp_seq.h" 32 #include "tcp_timer.h" 33 #include "tcp_var.h" 34 #include "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 41 extern struct inpcb *tcp_last_inpcb; 42 43 /* 44 * Tcp initialization 45 */ 46 tcp_init() 47 { 48 49 tcp_iss = 1; /* wrong */ 50 tcb.inp_next = tcb.inp_prev = &tcb; 51 if (max_protohdr < sizeof(struct tcpiphdr)) 52 max_protohdr = sizeof(struct tcpiphdr); 53 if (max_linkhdr + sizeof(struct tcpiphdr) > MHLEN) 54 panic("tcp_init"); 55 } 56 57 /* 58 * Create template to be used to send tcp packets on a connection. 59 * Call after host entry created, allocates an mbuf and fills 60 * in a skeletal tcp/ip header, minimizing the amount of work 61 * necessary when the connection is used. 62 */ 63 struct tcpiphdr * 64 tcp_template(tp) 65 struct tcpcb *tp; 66 { 67 register struct inpcb *inp = tp->t_inpcb; 68 register struct mbuf *m; 69 register struct tcpiphdr *n; 70 71 if ((n = tp->t_template) == 0) { 72 m = m_get(M_DONTWAIT, MT_HEADER); 73 if (m == NULL) 74 return (0); 75 m->m_len = sizeof (struct tcpiphdr); 76 n = mtod(m, struct tcpiphdr *); 77 } 78 n->ti_next = n->ti_prev = 0; 79 n->ti_x1 = 0; 80 n->ti_pr = IPPROTO_TCP; 81 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 82 n->ti_src = inp->inp_laddr; 83 n->ti_dst = inp->inp_faddr; 84 n->ti_sport = inp->inp_lport; 85 n->ti_dport = inp->inp_fport; 86 n->ti_seq = 0; 87 n->ti_ack = 0; 88 n->ti_x2 = 0; 89 n->ti_off = 5; 90 n->ti_flags = 0; 91 n->ti_win = 0; 92 n->ti_sum = 0; 93 n->ti_urp = 0; 94 return (n); 95 } 96 97 /* 98 * Send a single message to the TCP at address specified by 99 * the given TCP/IP header. If m == 0, then we make a copy 100 * of the tcpiphdr at ti and send directly to the addressed host. 101 * This is used to force keep alive messages out using the TCP 102 * template for a connection tp->t_template. If flags are given 103 * then we send a message back to the TCP which originated the 104 * segment ti, and discard the mbuf containing it and any other 105 * attached mbufs. 106 * 107 * In any case the ack and sequence number of the transmitted 108 * segment are as specified by the parameters. 109 */ 110 tcp_respond(tp, ti, m, ack, seq, flags) 111 struct tcpcb *tp; 112 register struct tcpiphdr *ti; 113 register struct mbuf *m; 114 tcp_seq ack, seq; 115 int flags; 116 { 117 register int tlen; 118 int win = 0; 119 struct route *ro = 0; 120 121 if (tp) { 122 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 123 ro = &tp->t_inpcb->inp_route; 124 } 125 if (m == 0) { 126 m = m_gethdr(M_DONTWAIT, MT_HEADER); 127 if (m == NULL) 128 return; 129 #ifdef TCP_COMPAT_42 130 tlen = 1; 131 #else 132 tlen = 0; 133 #endif 134 m->m_data += max_linkhdr; 135 *mtod(m, struct tcpiphdr *) = *ti; 136 ti = mtod(m, struct tcpiphdr *); 137 flags = TH_ACK; 138 } else { 139 m_freem(m->m_next); 140 m->m_next = 0; 141 m->m_data = (caddr_t)ti; 142 m->m_len = sizeof (struct tcpiphdr); 143 tlen = 0; 144 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 145 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 146 xchg(ti->ti_dport, ti->ti_sport, u_short); 147 #undef xchg 148 } 149 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 150 tlen += sizeof (struct tcpiphdr); 151 m->m_len = tlen; 152 m->m_pkthdr.len = tlen; 153 m->m_pkthdr.rcvif = (struct ifnet *) 0; 154 ti->ti_next = ti->ti_prev = 0; 155 ti->ti_x1 = 0; 156 ti->ti_seq = htonl(seq); 157 ti->ti_ack = htonl(ack); 158 ti->ti_x2 = 0; 159 ti->ti_off = sizeof (struct tcphdr) >> 2; 160 ti->ti_flags = flags; 161 ti->ti_win = htons((u_short)win); 162 ti->ti_urp = 0; 163 ti->ti_sum = in_cksum(m, tlen); 164 ((struct ip *)ti)->ip_len = tlen; 165 ((struct ip *)ti)->ip_ttl = tcp_ttl; 166 (void) ip_output(m, (struct mbuf *)0, ro, 0); 167 } 168 169 /* 170 * Create a new TCP control block, making an 171 * empty reassembly queue and hooking it to the argument 172 * protocol control block. 173 */ 174 struct tcpcb * 175 tcp_newtcpcb(inp) 176 struct inpcb *inp; 177 { 178 struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB); 179 register struct tcpcb *tp; 180 181 if (m == NULL) 182 return ((struct tcpcb *)0); 183 tp = mtod(m, struct tcpcb *); 184 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 185 tp->t_maxseg = tcp_mssdflt; 186 187 tp->t_flags = 0; /* sends options! */ 188 tp->t_inpcb = inp; 189 /* 190 * Init srtt to TCPTV_SRTTBASE (0), so we can tell that we have no 191 * rtt estimate. Set rttvar so that srtt + 2 * rttvar gives 192 * reasonable initial retransmit time. 193 */ 194 tp->t_srtt = TCPTV_SRTTBASE; 195 tp->t_rttvar = tcp_rttdflt * PR_SLOWHZ << 2; 196 tp->t_rttmin = TCPTV_MIN; 197 TCPT_RANGESET(tp->t_rxtcur, 198 ((TCPTV_SRTTBASE >> 2) + (TCPTV_SRTTDFLT << 2)) >> 1, 199 TCPTV_MIN, TCPTV_REXMTMAX); 200 tp->snd_cwnd = TCP_MAXWIN; 201 tp->snd_ssthresh = TCP_MAXWIN; 202 inp->inp_ip.ip_ttl = tcp_ttl; 203 inp->inp_ppcb = (caddr_t)tp; 204 return (tp); 205 } 206 207 /* 208 * Drop a TCP connection, reporting 209 * the specified error. If connection is synchronized, 210 * then send a RST to peer. 211 */ 212 struct tcpcb * 213 tcp_drop(tp, errno) 214 register struct tcpcb *tp; 215 int errno; 216 { 217 struct socket *so = tp->t_inpcb->inp_socket; 218 219 if (TCPS_HAVERCVDSYN(tp->t_state)) { 220 tp->t_state = TCPS_CLOSED; 221 (void) tcp_output(tp); 222 tcpstat.tcps_drops++; 223 } else 224 tcpstat.tcps_conndrops++; 225 if (errno == ETIMEDOUT && tp->t_softerror) 226 errno = tp->t_softerror; 227 so->so_error = errno; 228 return (tcp_close(tp)); 229 } 230 231 /* 232 * Close a TCP control block: 233 * discard all space held by the tcp 234 * discard internet protocol block 235 * wake up any sleepers 236 */ 237 struct tcpcb * 238 tcp_close(tp) 239 register struct tcpcb *tp; 240 { 241 register struct tcpiphdr *t; 242 struct inpcb *inp = tp->t_inpcb; 243 struct socket *so = inp->inp_socket; 244 register struct mbuf *m; 245 #ifdef RTV_RTT 246 register struct rtentry *rt; 247 248 /* 249 * If we sent enough data to get some meaningful characteristics, 250 * save them in the routing entry. 'Enough' is arbitrarily 251 * defined as the sendpipesize (default 4K) * 16. This would 252 * give us 16 rtt samples assuming we only get one sample per 253 * window (the usual case on a long haul net). 16 samples is 254 * enough for the srtt filter to converge to within 5% of the correct 255 * value; fewer samples and we could save a very bogus rtt. 256 * 257 * Don't update the default route's characteristics and don't 258 * update anything that the user "locked". 259 */ 260 if (SEQ_LT(tp->iss + so->so_snd.sb_hiwat * 16, tp->snd_max) && 261 (rt = inp->inp_route.ro_rt) && 262 ((struct sockaddr_in *)rt_key(rt))->sin_addr.s_addr != INADDR_ANY) { 263 register u_long i; 264 265 if ((rt->rt_rmx.rmx_locks & RTV_RTT) == 0) { 266 i = tp->t_srtt * 267 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 268 if (rt->rt_rmx.rmx_rtt && i) 269 /* 270 * filter this update to half the old & half 271 * the new values, converting scale. 272 * See route.h and tcp_var.h for a 273 * description of the scaling constants. 274 */ 275 rt->rt_rmx.rmx_rtt = 276 (rt->rt_rmx.rmx_rtt + i) / 2; 277 else 278 rt->rt_rmx.rmx_rtt = i; 279 } 280 if ((rt->rt_rmx.rmx_locks & RTV_RTTVAR) == 0) { 281 i = tp->t_rttvar * 282 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 283 if (rt->rt_rmx.rmx_rttvar && i) 284 rt->rt_rmx.rmx_rttvar = 285 (rt->rt_rmx.rmx_rttvar + i) / 2; 286 else 287 rt->rt_rmx.rmx_rttvar = i; 288 } 289 /* 290 * update the pipelimit (ssthresh) if it has been updated 291 * already or if a pipesize was specified & the threshhold 292 * got below half the pipesize. I.e., wait for bad news 293 * before we start updating, then update on both good 294 * and bad news. 295 */ 296 if ((rt->rt_rmx.rmx_locks & RTV_SSTHRESH) == 0 && 297 (i = tp->snd_ssthresh) && rt->rt_rmx.rmx_ssthresh || 298 i < (rt->rt_rmx.rmx_sendpipe / 2)) { 299 /* 300 * convert the limit from user data bytes to 301 * packets then to packet data bytes. 302 */ 303 i = (i + tp->t_maxseg / 2) / tp->t_maxseg; 304 if (i < 2) 305 i = 2; 306 i *= (u_long)(tp->t_maxseg + sizeof (struct tcpiphdr)); 307 if (rt->rt_rmx.rmx_ssthresh) 308 rt->rt_rmx.rmx_ssthresh = 309 (rt->rt_rmx.rmx_ssthresh + i) / 2; 310 else 311 rt->rt_rmx.rmx_ssthresh = i; 312 } 313 } 314 #endif RTV_RTT 315 /* free the reassembly queue, if any */ 316 t = tp->seg_next; 317 while (t != (struct tcpiphdr *)tp) { 318 t = (struct tcpiphdr *)t->ti_next; 319 m = REASS_MBUF((struct tcpiphdr *)t->ti_prev); 320 remque(t->ti_prev); 321 m_freem(m); 322 } 323 if (tp->t_template) 324 (void) m_free(dtom(tp->t_template)); 325 (void) m_free(dtom(tp)); 326 inp->inp_ppcb = 0; 327 soisdisconnected(so); 328 /* clobber input pcb cache if we're closing the cached connection */ 329 if (inp == tcp_last_inpcb) 330 tcp_last_inpcb = &tcb; 331 in_pcbdetach(inp); 332 tcpstat.tcps_closed++; 333 return ((struct tcpcb *)0); 334 } 335 336 tcp_drain() 337 { 338 339 } 340 341 /* 342 * Notify a tcp user of an asynchronous error; 343 * store error as soft error, but wake up user 344 * (for now, won't do anything until can select for soft error). 345 */ 346 tcp_notify(inp, error) 347 register struct inpcb *inp; 348 int error; 349 { 350 351 ((struct tcpcb *)inp->inp_ppcb)->t_softerror = error; 352 wakeup((caddr_t) &inp->inp_socket->so_timeo); 353 sorwakeup(inp->inp_socket); 354 sowwakeup(inp->inp_socket); 355 } 356 357 tcp_ctlinput(cmd, sa, ip) 358 int cmd; 359 struct sockaddr *sa; 360 register struct ip *ip; 361 { 362 register struct tcphdr *th; 363 extern struct in_addr zeroin_addr; 364 extern u_char inetctlerrmap[]; 365 int (*notify)() = tcp_notify, tcp_quench(); 366 367 if (cmd == PRC_QUENCH) 368 notify = tcp_quench; 369 else if ((unsigned)cmd > PRC_NCMDS || inetctlerrmap[cmd] == 0) 370 return; 371 if (ip) { 372 th = (struct tcphdr *)((caddr_t)ip + (ip->ip_hl << 2)); 373 in_pcbnotify(&tcb, sa, th->th_dport, ip->ip_src, th->th_sport, 374 cmd, notify); 375 } else 376 in_pcbnotify(&tcb, sa, 0, zeroin_addr, 0, cmd, notify); 377 } 378 379 /* 380 * When a source quench is received, close congestion window 381 * to one segment. We will gradually open it again as we proceed. 382 */ 383 tcp_quench(inp) 384 struct inpcb *inp; 385 { 386 struct tcpcb *tp = intotcpcb(inp); 387 388 if (tp) 389 tp->snd_cwnd = tp->t_maxseg; 390 } 391