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 7.6 (Berkeley) 06/06/87 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 float tcp_alpha = TCP_ALPHA; 35 float tcp_beta = TCP_BETA; 36 37 /* 38 * Tcp initialization 39 */ 40 tcp_init() 41 { 42 43 tcp_iss = 1; /* wrong */ 44 tcb.inp_next = tcb.inp_prev = &tcb; 45 } 46 47 /* 48 * Create template to be used to send tcp packets on a connection. 49 * Call after host entry created, allocates an mbuf and fills 50 * in a skeletal tcp/ip header, minimizing the amount of work 51 * necessary when the connection is used. 52 */ 53 struct tcpiphdr * 54 tcp_template(tp) 55 struct tcpcb *tp; 56 { 57 register struct inpcb *inp = tp->t_inpcb; 58 register struct mbuf *m; 59 register struct tcpiphdr *n; 60 61 if ((n = tp->t_template) == 0) { 62 m = m_get(M_WAIT, MT_HEADER); 63 if (m == NULL) 64 return (0); 65 m->m_off = MMAXOFF - sizeof (struct tcpiphdr); 66 m->m_len = sizeof (struct tcpiphdr); 67 n = mtod(m, struct tcpiphdr *); 68 } 69 n->ti_next = n->ti_prev = 0; 70 n->ti_x1 = 0; 71 n->ti_pr = IPPROTO_TCP; 72 n->ti_len = htons(sizeof (struct tcpiphdr) - sizeof (struct ip)); 73 n->ti_src = inp->inp_laddr; 74 n->ti_dst = inp->inp_faddr; 75 n->ti_sport = inp->inp_lport; 76 n->ti_dport = inp->inp_fport; 77 n->ti_seq = 0; 78 n->ti_ack = 0; 79 n->ti_x2 = 0; 80 n->ti_off = 5; 81 n->ti_flags = 0; 82 n->ti_win = 0; 83 n->ti_sum = 0; 84 n->ti_urp = 0; 85 return (n); 86 } 87 88 /* 89 * Send a single message to the TCP at address specified by 90 * the given TCP/IP header. If flags==0, then we make a copy 91 * of the tcpiphdr at ti and send directly to the addressed host. 92 * This is used to force keep alive messages out using the TCP 93 * template for a connection tp->t_template. If flags are given 94 * then we send a message back to the TCP which originated the 95 * segment ti, and discard the mbuf containing it and any other 96 * attached mbufs. 97 * 98 * In any case the ack and sequence number of the transmitted 99 * segment are as specified by the parameters. 100 */ 101 tcp_respond(tp, ti, ack, seq, flags) 102 struct tcpcb *tp; 103 register struct tcpiphdr *ti; 104 tcp_seq ack, seq; 105 int flags; 106 { 107 register struct mbuf *m; 108 int win = 0, tlen; 109 struct route *ro = 0; 110 extern int tcp_keeplen; 111 112 if (tp) { 113 win = sbspace(&tp->t_inpcb->inp_socket->so_rcv); 114 ro = &tp->t_inpcb->inp_route; 115 } 116 if (flags == 0) { 117 m = m_get(M_DONTWAIT, MT_HEADER); 118 if (m == NULL) 119 return; 120 tlen = tcp_keeplen; 121 m->m_len = sizeof (struct tcpiphdr) + tlen; 122 *mtod(m, struct tcpiphdr *) = *ti; 123 ti = mtod(m, struct tcpiphdr *); 124 flags = TH_ACK; 125 } else { 126 m = dtom(ti); 127 m_freem(m->m_next); 128 m->m_next = 0; 129 m->m_off = (int)ti - (int)m; 130 tlen = 0; 131 m->m_len = sizeof (struct tcpiphdr); 132 #define xchg(a,b,type) { type t; t=a; a=b; b=t; } 133 xchg(ti->ti_dst.s_addr, ti->ti_src.s_addr, u_long); 134 xchg(ti->ti_dport, ti->ti_sport, u_short); 135 #undef xchg 136 } 137 ti->ti_next = ti->ti_prev = 0; 138 ti->ti_x1 = 0; 139 ti->ti_len = htons((u_short)(sizeof (struct tcphdr) + tlen)); 140 ti->ti_seq = htonl(seq); 141 ti->ti_ack = htonl(ack); 142 ti->ti_x2 = 0; 143 ti->ti_off = sizeof (struct tcphdr) >> 2; 144 ti->ti_flags = flags; 145 ti->ti_win = htons((u_short)win); 146 ti->ti_urp = 0; 147 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + tlen); 148 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + tlen; 149 ((struct ip *)ti)->ip_ttl = tcp_ttl; 150 (void) ip_output(m, (struct mbuf *)0, ro, 0); 151 } 152 153 /* 154 * Create a new TCP control block, making an 155 * empty reassembly queue and hooking it to the argument 156 * protocol control block. 157 */ 158 struct tcpcb * 159 tcp_newtcpcb(inp) 160 struct inpcb *inp; 161 { 162 struct mbuf *m = m_getclr(M_DONTWAIT, MT_PCB); 163 register struct tcpcb *tp; 164 165 if (m == NULL) 166 return ((struct tcpcb *)0); 167 tp = mtod(m, struct tcpcb *); 168 tp->seg_next = tp->seg_prev = (struct tcpiphdr *)tp; 169 tp->t_maxseg = TCP_MSS; 170 tp->t_flags = 0; /* sends options! */ 171 tp->t_inpcb = inp; 172 tp->t_srtt = TCPTV_SRTTBASE; 173 tp->snd_cwnd = sbspace(&inp->inp_socket->so_snd); 174 inp->inp_ppcb = (caddr_t)tp; 175 return (tp); 176 } 177 178 /* 179 * Drop a TCP connection, reporting 180 * the specified error. If connection is synchronized, 181 * then send a RST to peer. 182 */ 183 struct tcpcb * 184 tcp_drop(tp, errno) 185 register struct tcpcb *tp; 186 int errno; 187 { 188 struct socket *so = tp->t_inpcb->inp_socket; 189 190 if (TCPS_HAVERCVDSYN(tp->t_state)) { 191 tp->t_state = TCPS_CLOSED; 192 (void) tcp_output(tp); 193 tcpstat.tcps_drops++; 194 } else 195 tcpstat.tcps_conndrops++; 196 so->so_error = errno; 197 return (tcp_close(tp)); 198 } 199 200 /* 201 * Close a TCP control block: 202 * discard all space held by the tcp 203 * discard internet protocol block 204 * wake up any sleepers 205 */ 206 struct tcpcb * 207 tcp_close(tp) 208 register struct tcpcb *tp; 209 { 210 register struct tcpiphdr *t; 211 struct inpcb *inp = tp->t_inpcb; 212 struct socket *so = inp->inp_socket; 213 register struct mbuf *m; 214 215 t = tp->seg_next; 216 while (t != (struct tcpiphdr *)tp) { 217 t = (struct tcpiphdr *)t->ti_next; 218 m = dtom(t->ti_prev); 219 remque(t->ti_prev); 220 m_freem(m); 221 } 222 if (tp->t_template) 223 (void) m_free(dtom(tp->t_template)); 224 if (tp->t_tcpopt) 225 (void) m_free(dtom(tp->t_tcpopt)); 226 (void) m_free(dtom(tp)); 227 inp->inp_ppcb = 0; 228 soisdisconnected(so); 229 in_pcbdetach(inp); 230 tcpstat.tcps_closed++; 231 return ((struct tcpcb *)0); 232 } 233 234 tcp_drain() 235 { 236 237 } 238 239 /* 240 * Notify a tcp user of an asynchronous error; 241 * just wake up so that he can collect error status. 242 */ 243 tcp_notify(inp) 244 register struct inpcb *inp; 245 { 246 247 wakeup((caddr_t) &inp->inp_socket->so_timeo); 248 sorwakeup(inp->inp_socket); 249 sowwakeup(inp->inp_socket); 250 } 251 tcp_ctlinput(cmd, sa) 252 int cmd; 253 struct sockaddr *sa; 254 { 255 extern u_char inetctlerrmap[]; 256 struct sockaddr_in *sin; 257 int tcp_quench(), in_rtchange(); 258 259 if ((unsigned)cmd > PRC_NCMDS) 260 return; 261 if (sa->sa_family != AF_INET && sa->sa_family != AF_IMPLINK) 262 return; 263 sin = (struct sockaddr_in *)sa; 264 if (sin->sin_addr.s_addr == INADDR_ANY) 265 return; 266 267 switch (cmd) { 268 269 case PRC_QUENCH: 270 in_pcbnotify(&tcb, &sin->sin_addr, 0, tcp_quench); 271 break; 272 273 case PRC_ROUTEDEAD: 274 case PRC_REDIRECT_NET: 275 case PRC_REDIRECT_HOST: 276 case PRC_REDIRECT_TOSNET: 277 case PRC_REDIRECT_TOSHOST: 278 in_pcbnotify(&tcb, &sin->sin_addr, 0, in_rtchange); 279 break; 280 281 default: 282 if (inetctlerrmap[cmd] == 0) 283 return; /* XXX */ 284 in_pcbnotify(&tcb, &sin->sin_addr, (int)inetctlerrmap[cmd], 285 tcp_notify); 286 } 287 } 288 289 /* 290 * When a source quench is received, close congestion window 291 * to one segment. We will gradually open it again as we proceed. 292 */ 293 tcp_quench(inp) 294 struct inpcb *inp; 295 { 296 struct tcpcb *tp = intotcpcb(inp); 297 298 if (tp) 299 tp->snd_cwnd = tp->t_maxseg; 300 } 301