1 /* tcp_output.c 4.34 82/03/15 */ 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/in_pcb.h" 11 #include "../net/in_systm.h" 12 #include "../net/ip.h" 13 #include "../net/ip_var.h" 14 #include "../net/tcp.h" 15 #define TCPOUTFLAGS 16 #include "../net/tcp_fsm.h" 17 #include "../net/tcp_seq.h" 18 #include "../net/tcp_timer.h" 19 #include "../net/tcp_var.h" 20 #include "../net/tcpip.h" 21 #include "../net/tcp_debug.h" 22 #include "../errno.h" 23 24 char *tcpstates[]; /* XXX */ 25 26 /* 27 * Initial options: indicate max segment length 1/2 of space 28 * allocated for receive; if TCPTRUEOOB is defined, indicate 29 * willingness to do true out-of-band. 30 */ 31 #ifndef TCPTRUEOOB 32 u_char tcp_initopt[4] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, }; 33 #else 34 u_char tcp_initopt[6] = { TCPOPT_MAXSEG, 4, 0x0, 0x0, TCPOPT_WILLOOB, 2 }; 35 #endif 36 37 /* 38 * Tcp output routine: figure out what should be sent and send it. 39 */ 40 tcp_output(tp) 41 register struct tcpcb *tp; 42 { 43 register struct socket *so = tp->t_inpcb->inp_socket; 44 register int len; 45 struct mbuf *m0; 46 int off, flags, win; 47 register struct mbuf *m; 48 register struct tcpiphdr *ti; 49 u_char *opt; 50 unsigned optlen = 0; 51 52 COUNT(TCP_OUTPUT); 53 54 /* 55 * Determine length of data that can be transmitted, 56 * and flags that will be used. 57 * If there is some data or critical controls (SYN, RST) 58 * to send, then transmit; otherwise, investigate further. 59 */ 60 off = tp->snd_nxt - tp->snd_una; 61 len = MIN(so->so_snd.sb_cc, tp->snd_wnd+tp->t_force) - off; 62 if (len < 0) 63 return (0); /* past FIN */ 64 if (len > tp->t_maxseg) 65 len = tp->t_maxseg; 66 flags = tcp_outflags[tp->t_state]; 67 if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc) 68 flags &= ~TH_FIN; 69 if (len || (flags & (TH_SYN|TH_RST|TH_FIN))) 70 goto send; 71 72 /* 73 * Send if we owe peer an ACK. 74 */ 75 if (tp->t_flags&TF_ACKNOW) 76 goto send; 77 78 #ifdef TCPTRUEOOB 79 /* 80 * Send if an out of band data or ack should be transmitted. 81 */ 82 if (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK))) 83 goto send; 84 #endif 85 86 /* 87 * Calculate available window in i, and also amount 88 * of window known to peer (as advertised window less 89 * next expected input.) If this is 35% or more of the 90 * maximum possible window, then want to send a segment to peer. 91 */ 92 win = sbspace(&so->so_rcv); 93 if (win > 0 && 94 ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35)) 95 goto send; 96 97 /* 98 * No reason to send a segment, just return. 99 */ 100 return (0); 101 102 send: 103 /* 104 * Grab a header mbuf, attaching a copy of data to 105 * be transmitted, and initialize the header from 106 * the template for sends on this connection. 107 */ 108 MGET(m, 0); 109 if (m == 0) 110 return (0); 111 m->m_off = MMAXOFF - sizeof (struct tcpiphdr); 112 m->m_len = sizeof (struct tcpiphdr); 113 if (len) { 114 m->m_next = m_copy(so->so_snd.sb_mb, off, len); 115 if (m->m_next == 0) 116 len = 0; 117 } 118 ti = mtod(m, struct tcpiphdr *); 119 if (tp->t_template == 0) 120 panic("tcp_output"); 121 bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); 122 123 /* 124 * Fill in fields, remembering maximum advertised 125 * window for use in delaying messages about window sizes. 126 */ 127 ti->ti_seq = tp->snd_nxt; 128 ti->ti_ack = tp->rcv_nxt; 129 #if vax 130 ti->ti_seq = htonl(ti->ti_seq); 131 ti->ti_ack = htonl(ti->ti_ack); 132 #endif 133 /* 134 * Before ESTABLISHED, force sending of initial options 135 * unless TCP set to not do any options. 136 */ 137 if (tp->t_state < TCPS_ESTABLISHED) { 138 if (tp->t_flags&TF_NOOPT) 139 goto noopt; 140 opt = tcp_initopt; 141 optlen = sizeof (tcp_initopt); 142 *(u_short *)(opt + 2) = so->so_rcv.sb_hiwat / 2; 143 #if vax 144 *(u_short *)(opt + 2) = htons(*(u_short *)(opt + 2)); 145 #endif 146 } else { 147 if (tp->t_tcpopt == 0) 148 goto noopt; 149 opt = mtod(tp->t_tcpopt, u_char *); 150 optlen = tp->t_tcpopt->m_len; 151 } 152 #ifndef TCPTRUEOOB 153 if (opt) 154 #else 155 if (opt || (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK))) 156 #endif 157 { 158 m0 = m->m_next; 159 m->m_next = m_get(M_DONTWAIT); 160 if (m->m_next == 0) { 161 (void) m_free(m); 162 m_freem(m0); 163 return (0); 164 } 165 m->m_next->m_next = m0; 166 m0 = m->m_next; 167 m0->m_off = MMINOFF; 168 m0->m_len = optlen; 169 bcopy((caddr_t)opt, mtod(m0, caddr_t), optlen); 170 opt = (u_char *)(mtod(m0, caddr_t) + optlen); 171 #ifdef TCPTRUEOOB 172 if (tp->t_oobflags&TCPOOB_OWEACK) { 173 printf("tp %x send OOBACK for %x\n", tp->t_iobseq); 174 *opt++ = TCPOPT_OOBACK; 175 *opt++ = 3; 176 *opt++ = tp->t_iobseq; 177 m0->m_len += 3; 178 tp->t_oobflags &= ~TCPOOB_OWEACK; 179 /* sender should rexmt oob to force ack repeat */ 180 } 181 if (tp->t_oobflags&TCPOOB_NEEDACK) { 182 printf("tp %x send OOBDATA seq %x data %x\n", tp->t_oobseq, tp->t_oobc); 183 *opt++ = TCPOPT_OOBDATA; 184 *opt++ = 8; 185 *opt++ = tp->t_oobseq; 186 *opt++ = tp->t_oobc; 187 *(tcp_seq *)opt = tp->t_oobmark - tp->snd_nxt; 188 #ifdef vax 189 *(tcp_seq *)opt = htonl((unsigned)*(tcp_seq *)opt); 190 #endif 191 m0->m_len += 8; 192 TCPT_RANGESET(tp->t_timer[TCPT_OOBREXMT], 193 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 194 } 195 #endif 196 while (m0->m_len & 0x3) { 197 *opt++ = TCPOPT_EOL; 198 m0->m_len++; 199 } 200 optlen = m0->m_len; 201 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 202 } 203 noopt: 204 ti->ti_flags = flags; 205 win = sbspace(&so->so_rcv); 206 if (win > 0) 207 ti->ti_win = htons((u_short)win); 208 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 209 ti->ti_urp = tp->snd_up - tp->snd_nxt; 210 #if vax 211 ti->ti_urp = htons(ti->ti_urp); 212 #endif 213 ti->ti_flags |= TH_URG; 214 } else 215 /* 216 * If no urgent pointer to send, then we pull 217 * the urgent pointer to the left edge of the send window 218 * so that it doesn't drift into the send window on sequence 219 * number wraparound. 220 */ 221 tp->snd_up = tp->snd_una; /* drag it along */ 222 /* PUSH */ 223 224 /* 225 * Put TCP length in extended header, and then 226 * checksum extended header and data. 227 */ 228 if (len + optlen) { 229 ti->ti_len = sizeof (struct tcphdr) + optlen + len; 230 #if vax 231 ti->ti_len = htons((u_short)ti->ti_len); 232 #endif 233 } 234 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + (int)optlen + len); 235 236 /* 237 * Advance snd_nxt over sequence space of this segment 238 */ 239 if (flags & (TH_SYN|TH_FIN)) 240 tp->snd_nxt++; 241 tp->snd_nxt += len; 242 243 /* 244 * If this transmission closes the window, 245 * start persistance timer at 2 round trip times 246 * but at least TCPTV_PERSMIN ticks. 247 */ 248 if (TCPS_HAVERCVDSYN(tp->t_state) && 249 SEQ_GEQ(tp->snd_nxt, tp->snd_una+tp->snd_wnd) && 250 tp->t_timer[TCPT_PERSIST] == 0) 251 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], 252 2 * tp->t_srtt, TCPTV_PERSMIN, TCPTV_MAX); 253 254 /* 255 * Time this transmission if not a retransmission and 256 * not currently timing anything. 257 */ 258 if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) { 259 tp->t_rtt = 1; 260 tp->t_rtseq = tp->snd_nxt - len; 261 } 262 263 /* 264 * Set retransmit timer if not currently set. 265 * Initial value for retransmit timer to tcp_beta*tp->t_srtt. 266 * Initialize shift counter which is used for exponential 267 * backoff of retransmit time. 268 */ 269 if (tp->t_timer[TCPT_REXMT] == 0 && tp->snd_nxt != tp->snd_una) { 270 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 271 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 272 tp->t_rtt = 0; 273 tp->t_rxtshift = 0; 274 } 275 276 /* 277 * Trace. 278 */ 279 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 280 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 281 282 /* 283 * Fill in IP length and desired time to live and 284 * send to IP level. 285 */ 286 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len; 287 ((struct ip *)ti)->ip_ttl = TCP_TTL; 288 if (ip_output(m, tp->t_ipopt, 0) == 0) 289 return (0); 290 291 /* 292 * Data sent (as far as we can tell). 293 * If this advertises a larger window than any other segment, 294 * then remember the size of the advertised window. 295 * Drop send for purpose of ACK requirements. 296 */ 297 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 298 tp->rcv_adv = tp->rcv_nxt + win; 299 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); 300 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) 301 tp->snd_max = tp->snd_nxt; 302 return (1); 303 } 304