1 /* 2 * Copyright (c) 1982, 1986 Regents of the University of California. 3 * All rights reserved. The Berkeley software License Agreement 4 * specifies the terms and conditions for redistribution. 5 * 6 * @(#)tcp_subr.c 7.7 (Berkeley) 06/30/87 7 */ 8 9 #include "param.h" 10 #include "systm.h" 11 #include "mbuf.h" 12 #include "socket.h" 13 #include "socketvar.h" 14 #include "protosw.h" 15 #include "errno.h" 16 17 #include "../net/route.h" 18 #include "../net/if.h" 19 20 #include "in.h" 21 #include "in_pcb.h" 22 #include "in_systm.h" 23 #include "ip.h" 24 #include "ip_var.h" 25 #include "ip_icmp.h" 26 #include "tcp.h" 27 #include "tcp_fsm.h" 28 #include "tcp_seq.h" 29 #include "tcp_timer.h" 30 #include "tcp_var.h" 31 #include "tcpip.h" 32 33 int tcp_ttl = TCP_TTL; 34 35 /* 36 * Tcp initialization 37 */ 38 tcp_init() 39 { 40 41 tcp_iss = 1; /* wrong */ 42 tcb.inp_next = tcb.inp_prev = &tcb; 43 } 44 45 /* 46 * Create template to be used to send tcp packets on a connection. 47 * Call after host entry created, allocates an mbuf and fills 48 * in a skeletal tcp/ip header, minimizing the amount of work 49 * necessary when the connection is used. 50 */ 51 struct tcpiphdr * 52 tcp_template(tp) 53 struct tcpcb *tp; 54 { 55 register struct inpcb *inp = tp->t_inpcb; 56 register struct mbuf *m; 57 register struct tcpiphdr *n; 58 59 if ((n = tp->t_template) == 0) { 60 m = m_get(M_WAIT, MT_HEADER); 61 if (m == NULL) 62 return (0); 63 m->m_off = MMAXOFF - sizeof (struct tcpiphdr); 64 m->m_len = sizeof (struct tcpiphdr); 65 n = mtod(m, struct tcpiphdr *); 66 } 67 n->ti_next = n->ti_prev = 0; 68 n->ti_x1 = 0; 69 n->ti_pr = IPPROTO_TCP; 70 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 71 n->ti_src = inp->inp_laddr; 72 n->ti_dst = inp->inp_faddr; 73 n->ti_sport = inp->inp_lport; 74 n->ti_dport = inp->inp_fport; 75 n->ti_seq = 0; 76 n->ti_ack = 0; 77 n->ti_x2 = 0; 78 n->ti_off = 5; 79 n->ti_flags = 0; 80 n->ti_win = 0; 81 n->ti_sum = 0; 82 n->ti_urp = 0; 83 return (n); 84 } 85 86 /* 87 * Send a single message to the TCP at address specified by 88 * the given TCP/IP header. If flags==0, then we make a copy 89 * of the tcpiphdr at ti and send directly to the addressed host. 90 * This is used to force keep alive messages out using the TCP 91 * template for a connection tp->t_template. If flags are given 92 * then we send a message back to the TCP which originated the 93 * segment ti, and discard the mbuf containing it and any other 94 * attached mbufs. 95 * 96 * In any case the ack and sequence number of the transmitted 97 * segment are as specified by the parameters. 98 */ 99 tcp_respond(tp, ti, ack, seq, flags) 100 struct tcpcb *tp; 101 register struct tcpiphdr *ti; 102 tcp_seq ack, seq; 103 int flags; 104 { 105 register struct mbuf *m; 106 int win = 0, tlen; 107 struct route *ro = 0; 108 extern int tcp_keeplen; 109 110 if (tp) { 111 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 112 ro = &tp->t_inpcb->inp_route; 113 } 114 if (flags == 0) { 115 m = m_get(M_DONTWAIT, MT_HEADER); 116 if (m == NULL) 117 return; 118 tlen = tcp_keeplen; 119 m->m_len = sizeof (struct tcpiphdr) + tlen; 120 *mtod(m, struct tcpiphdr *) = *ti; 121 ti = mtod(m, struct tcpiphdr *); 122 flags = TH_ACK; 123 } else { 124 m = dtom(ti); 125 m_freem(m->m_next); 126 m->m_next = 0; 127 m->m_off = (int)ti - (int)m; 128 tlen = 0; 129 m->m_len = sizeof (struct tcpiphdr); 130 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 131 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 132 xchg(ti->ti_dport, ti->ti_sport, u_short); 133 #undef xchg 134 } 135 ti->ti_next = ti->ti_prev = 0; 136 ti->ti_x1 = 0; 137 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 138 ti->ti_seq = htonl(seq); 139 ti->ti_ack = htonl(ack); 140 ti->ti_x2 = 0; 141 ti->ti_off = sizeof (struct tcphdr) >> 2; 142 ti->ti_flags = flags; 143 ti->ti_win = htons((u_short)win); 144 ti->ti_urp = 0; 145 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + tlen); 146 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + tlen; 147 ((struct ip *)ti)->ip_ttl = tcp_ttl; 148 (void) ip_output(m, (struct mbuf *)0, ro, 0); 149 } 150 151 /* 152 * Create a new TCP control block, making an 153 * empty reassembly queue and hooking it to the argument 154 * protocol control block. 155 */ 156 struct tcpcb * 157 tcp_newtcpcb(inp) 158 struct inpcb *inp; 159 { 160 struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB); 161 register struct tcpcb *tp; 162 163 if (m == NULL) 164 return ((struct tcpcb *)0); 165 tp = mtod(m, struct tcpcb *); 166 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 167 tp->t_maxseg = TCP_MSS; 168 tp->t_flags = 0; /* sends options! */ 169 tp->t_inpcb = inp; 170 /* 171 * Init srtt to 0, so we can tell that we have no rtt estimate. 172 * Set rttvar so that srtt + 2 * rttvar gives reasonable initial 173 * retransmit time. 174 */ 175 tp->t_srtt = 0; 176 tp->t_rttvar = TCPTV_SRTTBASE << 2; 177 tp->snd_cwnd = sbspace(&inp->inp_socket->so_snd); 178 inp->inp_ppcb = (caddr_t)tp; 179 return (tp); 180 } 181 182 /* 183 * Drop a TCP connection, reporting 184 * the specified error. If connection is synchronized, 185 * then send a RST to peer. 186 */ 187 struct tcpcb * 188 tcp_drop(tp, errno) 189 register struct tcpcb *tp; 190 int errno; 191 { 192 struct socket *so = tp->t_inpcb->inp_socket; 193 194 if (TCPS_HAVERCVDSYN(tp->t_state)) { 195 tp->t_state = TCPS_CLOSED; 196 (void) tcp_output(tp); 197 tcpstat.tcps_drops++; 198 } else 199 tcpstat.tcps_conndrops++; 200 so->so_error = errno; 201 return (tcp_close(tp)); 202 } 203 204 /* 205 * Close a TCP control block: 206 * discard all space held by the tcp 207 * discard internet protocol block 208 * wake up any sleepers 209 */ 210 struct tcpcb * 211 tcp_close(tp) 212 register struct tcpcb *tp; 213 { 214 register struct tcpiphdr *t; 215 struct inpcb *inp = tp->t_inpcb; 216 struct socket *so = inp->inp_socket; 217 register struct mbuf *m; 218 219 t = tp->seg_next; 220 while (t != (struct tcpiphdr *)tp) { 221 t = (struct tcpiphdr *)t->ti_next; 222 m = dtom(t->ti_prev); 223 remque(t->ti_prev); 224 m_freem(m); 225 } 226 if (tp->t_template) 227 (void) m_free(dtom(tp->t_template)); 228 if (tp->t_tcpopt) 229 (void) m_free(dtom(tp->t_tcpopt)); 230 (void) m_free(dtom(tp)); 231 inp->inp_ppcb = 0; 232 soisdisconnected(so); 233 in_pcbdetach(inp); 234 tcpstat.tcps_closed++; 235 return ((struct tcpcb *)0); 236 } 237 238 tcp_drain() 239 { 240 241 } 242 243 /* 244 * Notify a tcp user of an asynchronous error; 245 * just wake up so that he can collect error status. 246 */ 247 tcp_notify(inp) 248 register struct inpcb *inp; 249 { 250 251 wakeup((caddr_t) &inp->inp_socket->so_timeo); 252 sorwakeup(inp->inp_socket); 253 sowwakeup(inp->inp_socket); 254 } 255 tcp_ctlinput(cmd, sa) 256 int cmd; 257 struct sockaddr *sa; 258 { 259 extern u_char inetctlerrmap[]; 260 struct sockaddr_in *sin; 261 int tcp_quench(), in_rtchange(); 262 263 if ((unsigned)cmd > PRC_NCMDS) 264 return; 265 if (sa->sa_family != AF_INET && sa->sa_family != AF_IMPLINK) 266 return; 267 sin = (struct sockaddr_in *)sa; 268 if (sin->sin_addr.s_addr == INADDR_ANY) 269 return; 270 271 switch (cmd) { 272 273 case PRC_QUENCH: 274 in_pcbnotify(&tcb, &sin->sin_addr, 0, tcp_quench); 275 break; 276 277 case PRC_ROUTEDEAD: 278 case PRC_REDIRECT_NET: 279 case PRC_REDIRECT_HOST: 280 case PRC_REDIRECT_TOSNET: 281 case PRC_REDIRECT_TOSHOST: 282 in_pcbnotify(&tcb, &sin->sin_addr, 0, in_rtchange); 283 break; 284 285 default: 286 if (inetctlerrmap[cmd] == 0) 287 return; /* XXX */ 288 in_pcbnotify(&tcb, &sin->sin_addr, (int)inetctlerrmap[cmd], 289 tcp_notify); 290 } 291 } 292 293 /* 294 * When a source quench is received, close congestion window 295 * to one segment. We will gradually open it again as we proceed. 296 */ 297 tcp_quench(inp) 298 struct inpcb *inp; 299 { 300 struct tcpcb *tp = intotcpcb(inp); 301 302 if (tp) 303 tp->snd_cwnd = tp->t_maxseg; 304 } 305