1 /* tcp_output.c 4.38 82/04/10 */ 2 3 #include "../h/param.h" 4 #include "../h/systm.h" 5 #include "../h/mbuf.h" 6 #include "../h/protosw.h" 7 #include "../h/socket.h" 8 #include "../h/socketvar.h" 9 #include "../net/in.h" 10 #include "../net/route.h" 11 #include "../net/in_pcb.h" 12 #include "../net/in_systm.h" 13 #include "../net/ip.h" 14 #include "../net/ip_var.h" 15 #include "../net/tcp.h" 16 #define TCPOUTFLAGS 17 #include "../net/tcp_fsm.h" 18 #include "../net/tcp_seq.h" 19 #include "../net/tcp_timer.h" 20 #include "../net/tcp_var.h" 21 #include "../net/tcpip.h" 22 #include "../net/tcp_debug.h" 23 #include <errno.h> 24 25 char *tcpstates[]; /* XXX */ 26 27 /* 28 * Initial options: indicate max segment length 1/2 of space 29 * allocated for receive; if TCPTRUEOOB is defined, indicate 30 * willingness to do true out-of-band. 31 */ 32 #ifndef TCPTRUEOOB 33 u_char tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, }; 34 #else 35 u_char tcp_initopt[6] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, TCPOPT_WILLOOB, 2 }; 36 #endif 37 38 /* 39 * Tcp output routine: figure out what should be sent and send it. 40 */ 41 tcp_output(tp) 42 register struct tcpcb *tp; 43 { 44 register struct socket *so = tp->t_inpcb->inp_socket; 45 register int len; 46 struct mbuf *m0; 47 int off, flags, win, error; 48 register struct mbuf *m; 49 register struct tcpiphdr *ti; 50 u_char *opt; 51 unsigned optlen = 0; 52 53 COUNT(TCP_OUTPUT); 54 55 /* 56 * Determine length of data that should be transmitted, 57 * and flags that will be used. 58 * If there is some data or critical controls (SYN, RST) 59 * to send, then transmit; otherwise, investigate further. 60 */ 61 off = tp->snd_nxt - tp->snd_una; 62 len = MIN(so->so_snd.sb_cc, tp->snd_wnd+tp->t_force) - off; 63 if (len < 0) 64 return (0); /* ??? */ /* past FIN */ 65 if (len > tp->t_maxseg) 66 len = tp->t_maxseg; 67 68 flags = tcp_outflags[tp->t_state]; 69 if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc) 70 flags &= ~TH_FIN; 71 if (flags & (TH_SYN|TH_RST|TH_FIN)) 72 goto send; 73 if (SEQ_GT(tp->snd_up, tp->snd_una)) 74 goto send; 75 76 /* 77 * Sender silly window avoidance. If can send all data, 78 * a maximum segment, at least 1/4 of window do it, 79 * or are forced, do it; otherwise don't bother. 80 */ 81 if (len) { 82 if (len == tp->t_maxseg || off+len >= so->so_snd.sb_cc) 83 goto send; 84 if (len * 4 >= tp->snd_wnd) /* a lot */ 85 goto send; 86 if (tp->t_force) 87 goto send; 88 } 89 90 /* 91 * Send if we owe peer an ACK. 92 */ 93 if (tp->t_flags&TF_ACKNOW) 94 goto send; 95 96 #ifdef TCPTRUEOOB 97 /* 98 * Send if an out of band data or ack should be transmitted. 99 */ 100 if (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK))) 101 goto send; 102 #endif 103 104 /* 105 * Calculate available window in i, and also amount 106 * of window known to peer (as advertised window less 107 * next expected input.) If this is 35% or more of the 108 * maximum possible window, then want to send a segment to peer. 109 */ 110 win = sbspace(&so->so_rcv); 111 if (win > 0 && 112 ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35)) 113 goto send; 114 115 /* 116 * No reason to send a segment, just return. 117 */ 118 return (0); 119 120 send: 121 /* 122 * Grab a header mbuf, attaching a copy of data to 123 * be transmitted, and initialize the header from 124 * the template for sends on this connection. 125 */ 126 MGET(m, 0); 127 if (m == 0) 128 return (ENOBUFS); 129 m->m_off = MMAXOFF - sizeof (struct tcpiphdr); 130 m->m_len = sizeof (struct tcpiphdr); 131 if (len) { 132 m->m_next = m_copy(so->so_snd.sb_mb, off, len); 133 if (m->m_next == 0) 134 len = 0; 135 } 136 ti = mtod(m, struct tcpiphdr *); 137 if (tp->t_template == 0) 138 panic("tcp_output"); 139 bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); 140 141 /* 142 * Fill in fields, remembering maximum advertised 143 * window for use in delaying messages about window sizes. 144 */ 145 ti->ti_seq = tp->snd_nxt; 146 ti->ti_ack = tp->rcv_nxt; 147 #if vax 148 ti->ti_seq = htonl(ti->ti_seq); 149 ti->ti_ack = htonl(ti->ti_ack); 150 #endif 151 /* 152 * Before ESTABLISHED, force sending of initial options 153 * unless TCP set to not do any options. 154 */ 155 if (tp->t_state < TCPS_ESTABLISHED) { 156 if (tp->t_flags&TF_NOOPT) 157 goto noopt; 158 opt = tcp_initopt; 159 optlen = sizeof (tcp_initopt); 160 *(u_short *)(opt + 2) = so->so_rcv.sb_hiwat / 2; 161 #if vax 162 *(u_short *)(opt + 2) = htons(*(u_short *)(opt + 2)); 163 #endif 164 } else { 165 if (tp->t_tcpopt == 0) 166 goto noopt; 167 opt = mtod(tp->t_tcpopt, u_char *); 168 optlen = tp->t_tcpopt->m_len; 169 } 170 #ifndef TCPTRUEOOB 171 if (opt) 172 #else 173 if (opt || (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK))) 174 #endif 175 { 176 m0 = m->m_next; 177 m->m_next = m_get(M_DONTWAIT); 178 if (m->m_next == 0) { 179 (void) m_free(m); 180 m_freem(m0); 181 return (ENOBUFS); 182 } 183 m->m_next->m_next = m0; 184 m0 = m->m_next; 185 m0->m_off = MMINOFF; 186 m0->m_len = optlen; 187 bcopy((caddr_t)opt, mtod(m0, caddr_t), optlen); 188 opt = (u_char *)(mtod(m0, caddr_t) + optlen); 189 #ifdef TCPTRUEOOB 190 if (tp->t_oobflags&TCPOOB_OWEACK) { 191 printf("tp %x send OOBACK for %x\n", tp->t_iobseq); 192 *opt++ = TCPOPT_OOBACK; 193 *opt++ = 3; 194 *opt++ = tp->t_iobseq; 195 m0->m_len += 3; 196 tp->t_oobflags &= ~TCPOOB_OWEACK; 197 /* sender should rexmt oob to force ack repeat */ 198 } 199 if (tp->t_oobflags&TCPOOB_NEEDACK) { 200 printf("tp %x send OOBDATA seq %x data %x\n", tp->t_oobseq, tp->t_oobc); 201 *opt++ = TCPOPT_OOBDATA; 202 *opt++ = 8; 203 *opt++ = tp->t_oobseq; 204 *opt++ = tp->t_oobc; 205 *(tcp_seq *)opt = tp->t_oobmark - tp->snd_nxt; 206 #ifdef vax 207 *(tcp_seq *)opt = htonl((unsigned)*(tcp_seq *)opt); 208 #endif 209 m0->m_len += 8; 210 TCPT_RANGESET(tp->t_timer[TCPT_OOBREXMT], 211 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 212 } 213 #endif 214 while (m0->m_len & 0x3) { 215 *opt++ = TCPOPT_EOL; 216 m0->m_len++; 217 } 218 optlen = m0->m_len; 219 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 220 } 221 noopt: 222 ti->ti_flags = flags; 223 win = sbspace(&so->so_rcv); 224 if (win < so->so_rcv.sb_hiwat / 4) /* avoid silly window */ 225 win = 0; 226 if (win > 0) 227 #if vax 228 ti->ti_win = htons((u_short)win); 229 #else 230 ti->ti_win = win; 231 #endif 232 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 233 ti->ti_urp = tp->snd_up - tp->snd_nxt; 234 #if vax 235 ti->ti_urp = htons(ti->ti_urp); 236 #endif 237 ti->ti_flags |= TH_URG; 238 } else 239 /* 240 * If no urgent pointer to send, then we pull 241 * the urgent pointer to the left edge of the send window 242 * so that it doesn't drift into the send window on sequence 243 * number wraparound. 244 */ 245 tp->snd_up = tp->snd_una; /* drag it along */ 246 /* PUSH */ 247 248 /* 249 * Put TCP length in extended header, and then 250 * checksum extended header and data. 251 */ 252 if (len + optlen) { 253 ti->ti_len = sizeof (struct tcphdr) + optlen + len; 254 #if vax 255 ti->ti_len = htons((u_short)ti->ti_len); 256 #endif 257 } 258 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len); 259 260 /* 261 * Advance snd_nxt over sequence space of this segment 262 */ 263 if (flags & (TH_SYN|TH_FIN)) 264 tp->snd_nxt++; 265 tp->snd_nxt += len; 266 267 /* 268 * If this transmission closes the window, 269 * start persistance timer at 2 round trip times 270 * but at least TCPTV_PERSMIN ticks. 271 */ 272 if (TCPS_HAVERCVDSYN(tp->t_state) && 273 SEQ_GEQ(tp->snd_nxt, tp->snd_una+tp->snd_wnd) && 274 tp->t_timer[TCPT_PERSIST] == 0) 275 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], 276 2 * tp->t_srtt, TCPTV_PERSMIN, TCPTV_MAX); 277 278 /* 279 * Time this transmission if not a retransmission and 280 * not currently timing anything. 281 */ 282 if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) { 283 tp->t_rtt = 1; 284 tp->t_rtseq = tp->snd_nxt - len; 285 } 286 287 /* 288 * Set retransmit timer if not currently set. 289 * Initial value for retransmit timer to tcp_beta*tp->t_srtt. 290 * Initialize shift counter which is used for exponential 291 * backoff of retransmit time. 292 */ 293 if (tp->t_timer[TCPT_REXMT] == 0 && tp->snd_nxt != tp->snd_una) { 294 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 295 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 296 tp->t_rtt = 0; 297 tp->t_rxtshift = 0; 298 } 299 300 /* 301 * Trace. 302 */ 303 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 304 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 305 306 /* 307 * Fill in IP length and desired time to live and 308 * send to IP level. 309 */ 310 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len; 311 ((struct ip *)ti)->ip_ttl = TCP_TTL; 312 if (error = ip_output(m, tp->t_ipopt, &tp->t_inpcb->inp_route, 0)) 313 return (error); 314 315 /* 316 * Data sent (as far as we can tell). 317 * If this advertises a larger window than any other segment, 318 * then remember the size of the advertised window. 319 * Drop send for purpose of ACK requirements. 320 */ 321 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 322 tp->rcv_adv = tp->rcv_nxt + win; 323 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); 324 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) 325 tp->snd_max = tp->snd_nxt; 326 return (0); 327 } 328