1 /* tcp_output.c 4.29 82/01/17 */ 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; 47 register struct mbuf *m; 48 register struct tcpiphdr *ti; 49 int win, force; 50 u_char *opt; 51 unsigned optlen = 0; 52 53 COUNT(TCP_OUTPUT); 54 55 /* 56 * Determine length of data that can 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; /* past FIN */ 65 if (len > tp->t_maxseg) 66 len = tp->t_maxseg; 67 flags = tcp_outflags[tp->t_state]; 68 if (tp->snd_nxt + len < tp->snd_una + so->so_snd.sb_cc) 69 flags &= ~TH_FIN; 70 if (len || (flags & (TH_SYN|TH_RST|TH_FIN))) 71 goto send; 72 73 /* 74 * Send if we owe peer an ACK. 75 */ 76 if (tp->t_flags&TF_ACKNOW) 77 goto send; 78 79 #ifdef TCPTRUEOOB 80 /* 81 * Send if an out of band data or ack should be transmitted. 82 */ 83 if (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK))) 84 goto send; 85 #endif 86 87 /* 88 * Calculate available window in i, and also amount 89 * of window known to peer (as advertised window less 90 * next expected input.) If this is 35% or more of the 91 * maximum possible window, then want to send a segment to peer. 92 */ 93 win = sbspace(&so->so_rcv); 94 if (win > 0 && 95 ((100*(win-(tp->rcv_adv-tp->rcv_nxt))/so->so_rcv.sb_hiwat) >= 35)) 96 goto send; 97 98 /* 99 * No reason to send a segment, just return. 100 */ 101 return (0); 102 103 send: 104 /* 105 * Grab a header mbuf, attaching a copy of data to 106 * be transmitted, and initialize the header from 107 * the template for sends on this connection. 108 */ 109 MGET(m, 0); 110 if (m == 0) 111 return (0); 112 m->m_off = MMAXOFF - sizeof (struct tcpiphdr); 113 m->m_len = sizeof (struct tcpiphdr); 114 if (len) { 115 m->m_next = m_copy(so->so_snd.sb_mb, off, len); 116 if (m->m_next == 0) 117 len = 0; 118 } 119 ti = mtod(m, struct tcpiphdr *); 120 if (tp->t_template == 0) 121 panic("tcp_output"); 122 bcopy((caddr_t)tp->t_template, (caddr_t)ti, sizeof (struct tcpiphdr)); 123 124 /* 125 * Fill in fields, remembering maximum advertised 126 * window for use in delaying messages about window sizes. 127 */ 128 ti->ti_seq = tp->snd_nxt; 129 ti->ti_ack = tp->rcv_nxt; 130 #if vax 131 ti->ti_seq = htonl(ti->ti_seq); 132 ti->ti_ack = htonl(ti->ti_ack); 133 #endif 134 /* 135 * Before ESTABLISHED, force sending of initial options 136 * unless TCP set to not do any options. 137 */ 138 if (tp->t_state < TCPS_ESTABLISHED) { 139 if (tp->t_flags&TF_NOOPT) 140 goto noopt; 141 opt = tcp_initopt; 142 optlen = sizeof (tcp_initopt); 143 *(u_short *)(opt + 2) = so->so_rcv.sb_hiwat / 2; 144 #if vax 145 *(u_short *)(opt + 2) = htons(*(u_short *)(opt + 2)); 146 #endif 147 } else { 148 if (tp->t_tcpopt == 0) 149 goto noopt; 150 opt = mtod(tp->t_tcpopt, u_char *); 151 optlen = tp->t_tcpopt->m_len; 152 } 153 #ifndef TCPTRUEOOB 154 if (opt) 155 #else 156 if (opt || (tp->t_oobflags&(TCPOOB_OWEACK|TCPOOB_NEEDACK))) 157 #endif 158 { 159 m0 = m->m_next; 160 m->m_next = m_get(0); 161 if (m->m_next == 0) { 162 (void) m_free(m); 163 m_freem(m0); 164 return (0); 165 } 166 m->m_next->m_next = m0; 167 m0 = m->m_next; 168 m0->m_off = MMINOFF; 169 m0->m_len = optlen; 170 bcopy(opt, mtod(m0, caddr_t), optlen); 171 opt = (u_char *)(mtod(m0, caddr_t) + optlen); 172 #ifdef TCPTRUEOOB 173 if (tp->t_oobflags&TCPOOB_OWEACK) { 174 printf("tp %x send OOBACK for %x\n", tp->t_iobseq); 175 *opt++ = TCPOPT_OOBACK; 176 *opt++ = 3; 177 *opt++ = tp->t_iobseq; 178 m0->m_len += 3; 179 tp->t_oobflags &= ~TCPOOB_OWEACK; 180 /* sender should rexmt oob to force ack repeat */ 181 } 182 if (tp->t_oobflags&TCPOOB_NEEDACK) { 183 printf("tp %x send OOBDATA seq %x data %x\n", tp->t_oobseq, tp->t_oobc); 184 *opt++ = TCPOPT_OOBDATA; 185 *opt++ = 4; 186 *opt++ = tp->t_oobseq; 187 *opt++ = tp->t_oobc; 188 m0->m_len += 4; 189 TCPT_RANGESET(tp->t_timer[TCPT_OOBREXMT], 190 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 191 } 192 #endif 193 while (m0->m_len & 0x3) { 194 *opt++ = TCPOPT_EOL; 195 m0->m_len++; 196 } 197 optlen = m0->m_len; 198 ti->ti_off = (sizeof (struct tcphdr) + optlen) >> 2; 199 } 200 noopt: 201 ti->ti_flags = flags; 202 win = sbspace(&so->so_rcv); 203 if (win > 0) 204 ti->ti_win = htons((u_short)win); 205 if (SEQ_GT(tp->snd_up, tp->snd_nxt)) { 206 ti->ti_urp = tp->snd_up - tp->snd_nxt; 207 #if vax 208 ti->ti_urp = htons(ti->ti_urp); 209 #endif 210 ti->ti_flags |= TH_URG; 211 } else 212 /* 213 * If no urgent pointer to send, then we pull 214 * the urgent pointer to the left edge of the send window 215 * so that it doesn't drift into the send window on sequence 216 * number wraparound. 217 */ 218 tp->snd_up = tp->snd_una; /* drag it along */ 219 /* PUSH */ 220 221 /* 222 * Put TCP length in extended header, and then 223 * checksum extended header and data. 224 */ 225 if (len + optlen) { 226 ti->ti_len = sizeof (struct tcphdr) + optlen + len; 227 #if vax 228 ti->ti_len = htons((u_short)ti->ti_len); 229 #endif 230 } 231 ti->ti_sum = in_cksum(m, sizeof (struct tcpiphdr) + optlen + len); 232 233 /* 234 * Advance snd_nxt over sequence space of this segment 235 */ 236 if (flags & (TH_SYN|TH_FIN)) 237 tp->snd_nxt++; 238 tp->snd_nxt += len; 239 240 /* 241 * If this transmission closes the window, 242 * start persistance timer at 2 round trip times 243 * but at least TCPTV_PERSMIN ticks. 244 */ 245 if (TCPS_HAVERCVDSYN(tp->t_state) && 246 SEQ_GEQ(tp->snd_nxt, tp->snd_una+tp->snd_wnd) && 247 tp->t_timer[TCPT_PERSIST] == 0) 248 TCPT_RANGESET(tp->t_timer[TCPT_PERSIST], 249 2 * tp->t_srtt, TCPTV_PERSMIN, TCPTV_MAX); 250 251 /* 252 * Time this transmission if not a retransmission and 253 * not currently timing anything. 254 */ 255 if (SEQ_GT(tp->snd_nxt, tp->snd_max) && tp->t_rtt == 0) { 256 tp->t_rtt = 1; 257 tp->t_rtseq = tp->snd_nxt - len; 258 } 259 260 /* 261 * Set retransmit timer if not currently set. 262 * Initial value for retransmit timer to tcp_beta*tp->t_srtt. 263 * Initialize shift counter which is used for exponential 264 * backoff of retransmit time. 265 */ 266 if (tp->t_timer[TCPT_REXMT] == 0 && tp->snd_nxt != tp->snd_una) { 267 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 268 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 269 tp->t_rtt = 0; 270 tp->t_rxtshift = 0; 271 } 272 273 /* 274 * Trace. 275 */ 276 if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 277 tcp_trace(TA_OUTPUT, tp->t_state, tp, ti, 0); 278 279 /* 280 * Fill in IP length and desired time to live and 281 * send to IP level. 282 */ 283 ((struct ip *)ti)->ip_len = sizeof (struct tcpiphdr) + optlen + len; 284 ((struct ip *)ti)->ip_ttl = TCP_TTL; 285 if (ip_output(m, tp->t_ipopt) == 0) 286 return (0); 287 288 /* 289 * Data sent (as far as we can tell). 290 * If this advertises a larger window than any other segment, 291 * then remember the size of the advertised window. 292 * Drop send for purpose of ACK requirements. 293 */ 294 if (win > 0 && SEQ_GT(tp->rcv_nxt+win, tp->rcv_adv)) 295 tp->rcv_adv = tp->rcv_nxt + win; 296 tp->t_flags &= ~(TF_ACKNOW|TF_DELACK); 297 if (SEQ_GT(tp->snd_nxt, tp->snd_max)) 298 tp->snd_max = tp->snd_nxt; 299 return (1); 300 } 301