1 /* 2 * Copyright (c) 1982, 1986, 1988 Regents of the University of California. 3 * All rights reserved. 4 * 5 * Redistribution and use in source and binary forms are permitted 6 * provided that this notice is preserved and that due credit is given 7 * to the University of California at Berkeley. The name of the University 8 * may not be used to endorse or promote products derived from this 9 * software without specific prior written permission. This software 10 * is provided ``as is'' without express or implied warranty. 11 * 12 * @(#)tcp_input.c 7.15.1.2 (Berkeley) 03/16/88 13 */ 14 15 #include "param.h" 16 #include "systm.h" 17 #include "mbuf.h" 18 #include "protosw.h" 19 #include "socket.h" 20 #include "socketvar.h" 21 #include "errno.h" 22 23 #include "../net/if.h" 24 #include "../net/route.h" 25 26 #include "in.h" 27 #include "in_pcb.h" 28 #include "in_systm.h" 29 #include "ip.h" 30 #include "ip_var.h" 31 #include "tcp.h" 32 #include "tcp_fsm.h" 33 #include "tcp_seq.h" 34 #include "tcp_timer.h" 35 #include "tcp_var.h" 36 #include "tcpip.h" 37 #include "tcp_debug.h" 38 39 int tcpprintfs = 0; 40 int tcpcksum = 1; 41 int tcprexmtthresh = 3; 42 struct tcpiphdr tcp_saveti; 43 extern tcpnodelack; 44 45 struct tcpcb *tcp_newtcpcb(); 46 47 /* 48 * Insert segment ti into reassembly queue of tcp with 49 * control block tp. Return TH_FIN if reassembly now includes 50 * a segment with FIN. The macro form does the common case inline 51 * (segment is the next to be received on an established connection, 52 * and the queue is empty), avoiding linkage into and removal 53 * from the queue and repetition of various conversions. 54 */ 55 #define TCP_REASS(tp, ti, m, so, flags) { \ 56 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 57 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 58 (tp)->t_state == TCPS_ESTABLISHED) { \ 59 (tp)->rcv_nxt += (ti)->ti_len; \ 60 flags = (ti)->ti_flags & TH_FIN; \ 61 tcpstat.tcps_rcvpack++;\ 62 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 63 sbappend(&(so)->so_rcv, (m)); \ 64 sorwakeup(so); \ 65 } else \ 66 (flags) = tcp_reass((tp), (ti)); \ 67 } 68 69 tcp_reass(tp, ti) 70 register struct tcpcb *tp; 71 register struct tcpiphdr *ti; 72 { 73 register struct tcpiphdr *q; 74 struct socket *so = tp->t_inpcb->inp_socket; 75 struct mbuf *m; 76 int flags; 77 78 /* 79 * Call with ti==0 after become established to 80 * force pre-ESTABLISHED data up to user socket. 81 */ 82 if (ti == 0) 83 goto present; 84 85 /* 86 * Find a segment which begins after this one does. 87 */ 88 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 89 q = (struct tcpiphdr *)q->ti_next) 90 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 91 break; 92 93 /* 94 * If there is a preceding segment, it may provide some of 95 * our data already. If so, drop the data from the incoming 96 * segment. If it provides all of our data, drop us. 97 */ 98 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 99 register int i; 100 q = (struct tcpiphdr *)q->ti_prev; 101 /* conversion to int (in i) handles seq wraparound */ 102 i = q->ti_seq + q->ti_len - ti->ti_seq; 103 if (i > 0) { 104 if (i >= ti->ti_len) { 105 tcpstat.tcps_rcvduppack++; 106 tcpstat.tcps_rcvdupbyte += ti->ti_len; 107 goto drop; 108 } 109 m_adj(dtom(ti), i); 110 ti->ti_len -= i; 111 ti->ti_seq += i; 112 } 113 q = (struct tcpiphdr *)(q->ti_next); 114 } 115 tcpstat.tcps_rcvoopack++; 116 tcpstat.tcps_rcvoobyte += ti->ti_len; 117 118 /* 119 * While we overlap succeeding segments trim them or, 120 * if they are completely covered, dequeue them. 121 */ 122 while (q != (struct tcpiphdr *)tp) { 123 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 124 if (i <= 0) 125 break; 126 if (i < q->ti_len) { 127 q->ti_seq += i; 128 q->ti_len -= i; 129 m_adj(dtom(q), i); 130 break; 131 } 132 q = (struct tcpiphdr *)q->ti_next; 133 m = dtom(q->ti_prev); 134 remque(q->ti_prev); 135 m_freem(m); 136 } 137 138 /* 139 * Stick new segment in its place. 140 */ 141 insque(ti, q->ti_prev); 142 143 present: 144 /* 145 * Present data to user, advancing rcv_nxt through 146 * completed sequence space. 147 */ 148 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 149 return (0); 150 ti = tp->seg_next; 151 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 152 return (0); 153 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 154 return (0); 155 do { 156 tp->rcv_nxt += ti->ti_len; 157 flags = ti->ti_flags & TH_FIN; 158 remque(ti); 159 m = dtom(ti); 160 ti = (struct tcpiphdr *)ti->ti_next; 161 if (so->so_state & SS_CANTRCVMORE) 162 m_freem(m); 163 else 164 sbappend(&so->so_rcv, m); 165 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 166 sorwakeup(so); 167 return (flags); 168 drop: 169 m_freem(dtom(ti)); 170 return (0); 171 } 172 173 /* 174 * TCP input routine, follows pages 65-76 of the 175 * protocol specification dated September, 1981 very closely. 176 */ 177 tcp_input(m0) 178 struct mbuf *m0; 179 { 180 register struct tcpiphdr *ti; 181 struct inpcb *inp; 182 register struct mbuf *m; 183 struct mbuf *om = 0; 184 int len, tlen, off; 185 register struct tcpcb *tp = 0; 186 register int tiflags; 187 struct socket *so; 188 int todrop, acked, ourfinisacked, needoutput = 0; 189 short ostate; 190 struct in_addr laddr; 191 int dropsocket = 0; 192 int iss = 0; 193 194 tcpstat.tcps_rcvtotal++; 195 /* 196 * Get IP and TCP header together in first mbuf. 197 * Note: IP leaves IP header in first mbuf. 198 */ 199 m = m0; 200 ti = mtod(m, struct tcpiphdr *); 201 if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 202 ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 203 if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 204 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 205 tcpstat.tcps_rcvshort++; 206 return; 207 } 208 ti = mtod(m, struct tcpiphdr *); 209 } 210 211 /* 212 * Checksum extended TCP header and data. 213 */ 214 tlen = ((struct ip *)ti)->ip_len; 215 len = sizeof (struct ip) + tlen; 216 if (tcpcksum) { 217 ti->ti_next = ti->ti_prev = 0; 218 ti->ti_x1 = 0; 219 ti->ti_len = (u_short)tlen; 220 ti->ti_len = htons((u_short)ti->ti_len); 221 if (ti->ti_sum = in_cksum(m, len)) { 222 if (tcpprintfs) 223 printf("tcp sum: src %x\n", ti->ti_src); 224 tcpstat.tcps_rcvbadsum++; 225 goto drop; 226 } 227 } 228 229 /* 230 * Check that TCP offset makes sense, 231 * pull out TCP options and adjust length. 232 */ 233 off = ti->ti_off << 2; 234 if (off < sizeof (struct tcphdr) || off > tlen) { 235 if (tcpprintfs) 236 printf("tcp off: src %x off %d\n", ti->ti_src, off); 237 tcpstat.tcps_rcvbadoff++; 238 goto drop; 239 } 240 tlen -= off; 241 ti->ti_len = tlen; 242 if (off > sizeof (struct tcphdr)) { 243 if (m->m_len < sizeof(struct ip) + off) { 244 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 245 tcpstat.tcps_rcvshort++; 246 return; 247 } 248 ti = mtod(m, struct tcpiphdr *); 249 } 250 om = m_get(M_DONTWAIT, MT_DATA); 251 if (om == 0) 252 goto drop; 253 om->m_len = off - sizeof (struct tcphdr); 254 { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 255 bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); 256 m->m_len -= om->m_len; 257 bcopy(op+om->m_len, op, 258 (unsigned)(m->m_len-sizeof (struct tcpiphdr))); 259 } 260 } 261 tiflags = ti->ti_flags; 262 263 /* 264 * Drop TCP and IP headers; TCP options were dropped above. 265 */ 266 m->m_off += sizeof(struct tcpiphdr); 267 m->m_len -= sizeof(struct tcpiphdr); 268 269 /* 270 * Convert TCP protocol specific fields to host format. 271 */ 272 ti->ti_seq = ntohl(ti->ti_seq); 273 ti->ti_ack = ntohl(ti->ti_ack); 274 ti->ti_win = ntohs(ti->ti_win); 275 ti->ti_urp = ntohs(ti->ti_urp); 276 277 /* 278 * Locate pcb for segment. 279 */ 280 findpcb: 281 inp = in_pcblookup 282 (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, 283 INPLOOKUP_WILDCARD); 284 285 /* 286 * If the state is CLOSED (i.e., TCB does not exist) then 287 * all data in the incoming segment is discarded. 288 * If the TCB exists but is in CLOSED state, it is embryonic, 289 * but should either do a listen or a connect soon. 290 */ 291 if (inp == 0) 292 goto dropwithreset; 293 tp = intotcpcb(inp); 294 if (tp == 0) 295 goto dropwithreset; 296 if (tp->t_state == TCPS_CLOSED) 297 goto drop; 298 so = inp->inp_socket; 299 if (so->so_options & SO_DEBUG) { 300 ostate = tp->t_state; 301 tcp_saveti = *ti; 302 } 303 if (so->so_options & SO_ACCEPTCONN) { 304 so = sonewconn(so); 305 if (so == 0) 306 goto drop; 307 /* 308 * This is ugly, but .... 309 * 310 * Mark socket as temporary until we're 311 * committed to keeping it. The code at 312 * ``drop'' and ``dropwithreset'' check the 313 * flag dropsocket to see if the temporary 314 * socket created here should be discarded. 315 * We mark the socket as discardable until 316 * we're committed to it below in TCPS_LISTEN. 317 */ 318 dropsocket++; 319 inp = (struct inpcb *)so->so_pcb; 320 inp->inp_laddr = ti->ti_dst; 321 inp->inp_lport = ti->ti_dport; 322 #if BSD>=43 323 inp->inp_options = ip_srcroute(); 324 #endif 325 tp = intotcpcb(inp); 326 tp->t_state = TCPS_LISTEN; 327 } 328 329 /* 330 * Segment received on connection. 331 * Reset idle time and keep-alive timer. 332 */ 333 tp->t_idle = 0; 334 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 335 336 /* 337 * Process options if not in LISTEN state, 338 * else do it below (after getting remote address). 339 */ 340 if (om && tp->t_state != TCPS_LISTEN) { 341 tcp_dooptions(tp, om, ti); 342 om = 0; 343 } 344 345 /* 346 * Calculate amount of space in receive window, 347 * and then do TCP input processing. 348 * Receive window is amount of space in rcv queue, 349 * but not less than advertised window. 350 */ 351 { int win; 352 353 win = sbspace(&so->so_rcv); 354 if (win < 0) 355 win = 0; 356 tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 357 } 358 359 switch (tp->t_state) { 360 361 /* 362 * If the state is LISTEN then ignore segment if it contains an RST. 363 * If the segment contains an ACK then it is bad and send a RST. 364 * If it does not contain a SYN then it is not interesting; drop it. 365 * Don't bother responding if the destination was a broadcast. 366 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 367 * tp->iss, and send a segment: 368 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 369 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 370 * Fill in remote peer address fields if not previously specified. 371 * Enter SYN_RECEIVED state, and process any other fields of this 372 * segment in this state. 373 */ 374 case TCPS_LISTEN: { 375 struct mbuf *am; 376 register struct sockaddr_in *sin; 377 378 if (tiflags & TH_RST) 379 goto drop; 380 if (tiflags & TH_ACK) 381 goto dropwithreset; 382 if ((tiflags & TH_SYN) == 0) 383 goto drop; 384 if (in_broadcast(ti->ti_dst)) 385 goto drop; 386 am = m_get(M_DONTWAIT, MT_SONAME); 387 if (am == NULL) 388 goto drop; 389 am->m_len = sizeof (struct sockaddr_in); 390 sin = mtod(am, struct sockaddr_in *); 391 sin->sin_family = AF_INET; 392 sin->sin_addr = ti->ti_src; 393 sin->sin_port = ti->ti_sport; 394 laddr = inp->inp_laddr; 395 if (inp->inp_laddr.s_addr == INADDR_ANY) 396 inp->inp_laddr = ti->ti_dst; 397 if (in_pcbconnect(inp, am)) { 398 inp->inp_laddr = laddr; 399 (void) m_free(am); 400 goto drop; 401 } 402 (void) m_free(am); 403 tp->t_template = tcp_template(tp); 404 if (tp->t_template == 0) { 405 tp = tcp_drop(tp, ENOBUFS); 406 dropsocket = 0; /* socket is already gone */ 407 goto drop; 408 } 409 if (om) { 410 tcp_dooptions(tp, om, ti); 411 om = 0; 412 } 413 if (iss) 414 tp->iss = iss; 415 else 416 tp->iss = tcp_iss; 417 tcp_iss += TCP_ISSINCR/2; 418 tp->irs = ti->ti_seq; 419 tcp_sendseqinit(tp); 420 tcp_rcvseqinit(tp); 421 tp->t_flags |= TF_ACKNOW; 422 tp->t_state = TCPS_SYN_RECEIVED; 423 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 424 dropsocket = 0; /* committed to socket */ 425 tcpstat.tcps_accepts++; 426 goto trimthenstep6; 427 } 428 429 /* 430 * If the state is SYN_SENT: 431 * if seg contains an ACK, but not for our SYN, drop the input. 432 * if seg contains a RST, then drop the connection. 433 * if seg does not contain SYN, then drop it. 434 * Otherwise this is an acceptable SYN segment 435 * initialize tp->rcv_nxt and tp->irs 436 * if seg contains ack then advance tp->snd_una 437 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 438 * arrange for segment to be acked (eventually) 439 * continue processing rest of data/controls, beginning with URG 440 */ 441 case TCPS_SYN_SENT: 442 if ((tiflags & TH_ACK) && 443 (SEQ_LEQ(ti->ti_ack, tp->iss) || 444 SEQ_GT(ti->ti_ack, tp->snd_max))) 445 goto dropwithreset; 446 if (tiflags & TH_RST) { 447 if (tiflags & TH_ACK) 448 tp = tcp_drop(tp, ECONNREFUSED); 449 goto drop; 450 } 451 if ((tiflags & TH_SYN) == 0) 452 goto drop; 453 if (tiflags & TH_ACK) { 454 tp->snd_una = ti->ti_ack; 455 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 456 tp->snd_nxt = tp->snd_una; 457 } 458 tp->t_timer[TCPT_REXMT] = 0; 459 tp->irs = ti->ti_seq; 460 tcp_rcvseqinit(tp); 461 tp->t_flags |= TF_ACKNOW; 462 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 463 tcpstat.tcps_connects++; 464 soisconnected(so); 465 tp->t_state = TCPS_ESTABLISHED; 466 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 467 (void) tcp_reass(tp, (struct tcpiphdr *)0); 468 /* 469 * if we didn't have to retransmit the SYN, 470 * use its rtt as our initial srtt & rtt var. 471 */ 472 if (tp->t_rtt) { 473 tp->t_srtt = tp->t_rtt << 3; 474 tp->t_rttvar = tp->t_rtt << 1; 475 TCPT_RANGESET(tp->t_rxtcur, 476 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 477 TCPTV_MIN, TCPTV_REXMTMAX); 478 tp->t_rtt = 0; 479 } 480 } else 481 tp->t_state = TCPS_SYN_RECEIVED; 482 483 trimthenstep6: 484 /* 485 * Advance ti->ti_seq to correspond to first data byte. 486 * If data, trim to stay within window, 487 * dropping FIN if necessary. 488 */ 489 ti->ti_seq++; 490 if (ti->ti_len > tp->rcv_wnd) { 491 todrop = ti->ti_len - tp->rcv_wnd; 492 #if BSD>=43 493 m_adj(m, -todrop); 494 #else 495 /* XXX work around 4.2 m_adj bug */ 496 if (m->m_len) { 497 m_adj(m, -todrop); 498 } else { 499 /* skip tcp/ip header in first mbuf */ 500 m_adj(m->m_next, -todrop); 501 } 502 #endif 503 ti->ti_len = tp->rcv_wnd; 504 tiflags &= ~TH_FIN; 505 tcpstat.tcps_rcvpackafterwin++; 506 tcpstat.tcps_rcvbyteafterwin += todrop; 507 } 508 tp->snd_wl1 = ti->ti_seq - 1; 509 tp->rcv_up = ti->ti_seq; 510 goto step6; 511 } 512 513 /* 514 * States other than LISTEN or SYN_SENT. 515 * First check that at least some bytes of segment are within 516 * receive window. If segment begins before rcv_nxt, 517 * drop leading data (and SYN); if nothing left, just ack. 518 */ 519 todrop = tp->rcv_nxt - ti->ti_seq; 520 if (todrop > 0) { 521 if (tiflags & TH_SYN) { 522 tiflags &= ~TH_SYN; 523 ti->ti_seq++; 524 if (ti->ti_urp > 1) 525 ti->ti_urp--; 526 else 527 tiflags &= ~TH_URG; 528 todrop--; 529 } 530 if (todrop > ti->ti_len || 531 todrop == ti->ti_len && (tiflags&TH_FIN) == 0) { 532 tcpstat.tcps_rcvduppack++; 533 tcpstat.tcps_rcvdupbyte += ti->ti_len; 534 /* 535 * If segment is just one to the left of the window, 536 * check two special cases: 537 * 1. Don't toss RST in response to 4.2-style keepalive. 538 * 2. If the only thing to drop is a FIN, we can drop 539 * it, but check the ACK or we will get into FIN 540 * wars if our FINs crossed (both CLOSING). 541 * In either case, send ACK to resynchronize, 542 * but keep on processing for RST or ACK. 543 */ 544 if ((tiflags & TH_FIN && todrop == ti->ti_len + 1) 545 #ifdef TCP_COMPAT_42 546 || (tiflags & TH_RST && ti->ti_seq == tp->rcv_nxt - 1) 547 #endif 548 ) { 549 todrop = ti->ti_len; 550 tiflags &= ~TH_FIN; 551 tp->t_flags |= TF_ACKNOW; 552 } else 553 goto dropafterack; 554 } else { 555 tcpstat.tcps_rcvpartduppack++; 556 tcpstat.tcps_rcvpartdupbyte += todrop; 557 } 558 m_adj(m, todrop); 559 ti->ti_seq += todrop; 560 ti->ti_len -= todrop; 561 if (ti->ti_urp > todrop) 562 ti->ti_urp -= todrop; 563 else { 564 tiflags &= ~TH_URG; 565 ti->ti_urp = 0; 566 } 567 } 568 569 /* 570 * If new data are received on a connection after the 571 * user processes are gone, then RST the other end. 572 */ 573 if ((so->so_state & SS_NOFDREF) && 574 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 575 tp = tcp_close(tp); 576 tcpstat.tcps_rcvafterclose++; 577 goto dropwithreset; 578 } 579 580 /* 581 * If segment ends after window, drop trailing data 582 * (and PUSH and FIN); if nothing left, just ACK. 583 */ 584 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 585 if (todrop > 0) { 586 tcpstat.tcps_rcvpackafterwin++; 587 if (todrop >= ti->ti_len) { 588 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 589 /* 590 * If a new connection request is received 591 * while in TIME_WAIT, drop the old connection 592 * and start over if the sequence numbers 593 * are above the previous ones. 594 */ 595 if (tiflags & TH_SYN && 596 tp->t_state == TCPS_TIME_WAIT && 597 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 598 iss = tp->rcv_nxt + TCP_ISSINCR; 599 (void) tcp_close(tp); 600 goto findpcb; 601 } 602 /* 603 * If window is closed can only take segments at 604 * window edge, and have to drop data and PUSH from 605 * incoming segments. Continue processing, but 606 * remember to ack. Otherwise, drop segment 607 * and ack. 608 */ 609 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 610 tp->t_flags |= TF_ACKNOW; 611 tcpstat.tcps_rcvwinprobe++; 612 } else 613 goto dropafterack; 614 } else 615 tcpstat.tcps_rcvbyteafterwin += todrop; 616 #if BSD>=43 617 m_adj(m, -todrop); 618 #else 619 /* XXX work around m_adj bug */ 620 if (m->m_len) { 621 m_adj(m, -todrop); 622 } else { 623 /* skip tcp/ip header in first mbuf */ 624 m_adj(m->m_next, -todrop); 625 } 626 #endif 627 ti->ti_len -= todrop; 628 tiflags &= ~(TH_PUSH|TH_FIN); 629 } 630 631 /* 632 * If the RST bit is set examine the state: 633 * SYN_RECEIVED STATE: 634 * If passive open, return to LISTEN state. 635 * If active open, inform user that connection was refused. 636 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 637 * Inform user that connection was reset, and close tcb. 638 * CLOSING, LAST_ACK, TIME_WAIT STATES 639 * Close the tcb. 640 */ 641 if (tiflags&TH_RST) switch (tp->t_state) { 642 643 case TCPS_SYN_RECEIVED: 644 so->so_error = ECONNREFUSED; 645 goto close; 646 647 case TCPS_ESTABLISHED: 648 case TCPS_FIN_WAIT_1: 649 case TCPS_FIN_WAIT_2: 650 case TCPS_CLOSE_WAIT: 651 so->so_error = ECONNRESET; 652 close: 653 tp->t_state = TCPS_CLOSED; 654 tcpstat.tcps_drops++; 655 tp = tcp_close(tp); 656 goto drop; 657 658 case TCPS_CLOSING: 659 case TCPS_LAST_ACK: 660 case TCPS_TIME_WAIT: 661 tp = tcp_close(tp); 662 goto drop; 663 } 664 665 /* 666 * If a SYN is in the window, then this is an 667 * error and we send an RST and drop the connection. 668 */ 669 if (tiflags & TH_SYN) { 670 tp = tcp_drop(tp, ECONNRESET); 671 goto dropwithreset; 672 } 673 674 /* 675 * If the ACK bit is off we drop the segment and return. 676 */ 677 if ((tiflags & TH_ACK) == 0) 678 goto drop; 679 680 /* 681 * Ack processing. 682 */ 683 switch (tp->t_state) { 684 685 /* 686 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 687 * ESTABLISHED state and continue processing, otherwise 688 * send an RST. 689 */ 690 case TCPS_SYN_RECEIVED: 691 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 692 SEQ_GT(ti->ti_ack, tp->snd_max)) 693 goto dropwithreset; 694 tcpstat.tcps_connects++; 695 soisconnected(so); 696 tp->t_state = TCPS_ESTABLISHED; 697 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 698 (void) tcp_reass(tp, (struct tcpiphdr *)0); 699 tp->snd_wl1 = ti->ti_seq - 1; 700 /* fall into ... */ 701 702 /* 703 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 704 * ACKs. If the ack is in the range 705 * tp->snd_una < ti->ti_ack <= tp->snd_max 706 * then advance tp->snd_una to ti->ti_ack and drop 707 * data from the retransmission queue. If this ACK reflects 708 * more up to date window information we update our window information. 709 */ 710 case TCPS_ESTABLISHED: 711 case TCPS_FIN_WAIT_1: 712 case TCPS_FIN_WAIT_2: 713 case TCPS_CLOSE_WAIT: 714 case TCPS_CLOSING: 715 case TCPS_LAST_ACK: 716 case TCPS_TIME_WAIT: 717 718 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 719 if (ti->ti_len == 0 && ti->ti_win == tp->snd_wnd) { 720 tcpstat.tcps_rcvdupack++; 721 /* 722 * If we have outstanding data (not a 723 * window probe), this is a completely 724 * duplicate ack (ie, window info didn't 725 * change), the ack is the biggest we've 726 * seen and we've seen exactly our rexmt 727 * threshhold of them, assume a packet 728 * has been dropped and retransmit it. 729 * Kludge snd_nxt & the congestion 730 * window so we send only this one 731 * packet. If this packet fills the 732 * only hole in the receiver's seq. 733 * space, the next real ack will fully 734 * open our window. This means we 735 * have to do the usual slow-start to 736 * not overwhelm an intermediate gateway 737 * with a burst of packets. Leave 738 * here with the congestion window set 739 * to allow 2 packets on the next real 740 * ack and the exp-to-linear thresh 741 * set for half the current window 742 * size (since we know we're losing at 743 * the current window size). 744 */ 745 if (tp->t_timer[TCPT_REXMT] == 0 || 746 ti->ti_ack != tp->snd_una) 747 tp->t_dupacks = 0; 748 else if (++tp->t_dupacks == tcprexmtthresh) { 749 tcp_seq onxt = tp->snd_nxt; 750 u_int win = 751 MIN(tp->snd_wnd, tp->snd_cwnd) / 2 / 752 tp->t_maxseg; 753 754 if (win < 2) 755 win = 2; 756 tp->snd_ssthresh = win * tp->t_maxseg; 757 758 tp->t_timer[TCPT_REXMT] = 0; 759 tp->t_rtt = 0; 760 tp->snd_nxt = ti->ti_ack; 761 tp->snd_cwnd = tp->t_maxseg; 762 (void) tcp_output(tp); 763 764 if (SEQ_GT(onxt, tp->snd_nxt)) 765 tp->snd_nxt = onxt; 766 goto drop; 767 } 768 } else 769 tp->t_dupacks = 0; 770 break; 771 } 772 tp->t_dupacks = 0; 773 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 774 tcpstat.tcps_rcvacktoomuch++; 775 goto dropafterack; 776 } 777 acked = ti->ti_ack - tp->snd_una; 778 tcpstat.tcps_rcvackpack++; 779 tcpstat.tcps_rcvackbyte += acked; 780 781 /* 782 * If transmit timer is running and timed sequence 783 * number was acked, update smoothed round trip time. 784 * Since we now have an rtt measurement, cancel the 785 * timer backoff (cf., Phil Karn's retransmit alg.). 786 * Recompute the initial retransmit timer. 787 */ 788 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 789 tcpstat.tcps_rttupdated++; 790 if (tp->t_srtt != 0) { 791 register short delta; 792 793 /* 794 * srtt is stored as fixed point with 3 bits 795 * after the binary point (i.e., scaled by 8). 796 * The following magic is equivalent 797 * to the smoothing algorithm in rfc793 798 * with an alpha of .875 799 * (srtt = rtt/8 + srtt*7/8 in fixed point). 800 * Adjust t_rtt to origin 0. 801 */ 802 delta = tp->t_rtt - 1 - (tp->t_srtt >> 3); 803 if ((tp->t_srtt += delta) <= 0) 804 tp->t_srtt = 1; 805 /* 806 * We accumulate a smoothed rtt variance 807 * (actually, a smoothed mean difference), 808 * then set the retransmit timer to smoothed 809 * rtt + 2 times the smoothed variance. 810 * rttvar is stored as fixed point 811 * with 2 bits after the binary point 812 * (scaled by 4). The following is equivalent 813 * to rfc793 smoothing with an alpha of .75 814 * (rttvar = rttvar*3/4 + |delta| / 4). 815 * This replaces rfc793's wired-in beta. 816 */ 817 if (delta < 0) 818 delta = -delta; 819 delta -= (tp->t_rttvar >> 2); 820 if ((tp->t_rttvar += delta) <= 0) 821 tp->t_rttvar = 1; 822 } else { 823 /* 824 * No rtt measurement yet - use the 825 * unsmoothed rtt. Set the variance 826 * to half the rtt (so our first 827 * retransmit happens at 2*rtt) 828 */ 829 tp->t_srtt = tp->t_rtt << 3; 830 tp->t_rttvar = tp->t_rtt << 1; 831 } 832 tp->t_rtt = 0; 833 tp->t_rxtshift = 0; 834 TCPT_RANGESET(tp->t_rxtcur, 835 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 836 TCPTV_MIN, TCPTV_REXMTMAX); 837 } 838 839 /* 840 * If all outstanding data is acked, stop retransmit 841 * timer and remember to restart (more output or persist). 842 * If there is more data to be acked, restart retransmit 843 * timer, using current (possibly backed-off) value. 844 */ 845 if (ti->ti_ack == tp->snd_max) { 846 tp->t_timer[TCPT_REXMT] = 0; 847 needoutput = 1; 848 } else if (tp->t_timer[TCPT_PERSIST] == 0) 849 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 850 /* 851 * When new data is acked, open the congestion window. 852 * If the window gives us less than ssthresh packets 853 * in flight, open exponentially (maxseg per packet). 854 * Otherwise open linearly (maxseg per window, 855 * or maxseg^2 / cwnd per packet). 856 */ 857 { 858 u_int incr = tp->t_maxseg; 859 860 if (tp->snd_cwnd > tp->snd_ssthresh) 861 incr = MAX(incr * incr / tp->snd_cwnd, 1); 862 863 tp->snd_cwnd = MIN(tp->snd_cwnd + incr, IP_MAXPACKET); /* XXX */ 864 } 865 if (acked > so->so_snd.sb_cc) { 866 tp->snd_wnd -= so->so_snd.sb_cc; 867 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 868 ourfinisacked = 1; 869 } else { 870 sbdrop(&so->so_snd, acked); 871 tp->snd_wnd -= acked; 872 ourfinisacked = 0; 873 } 874 if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 875 sowwakeup(so); 876 tp->snd_una = ti->ti_ack; 877 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 878 tp->snd_nxt = tp->snd_una; 879 880 switch (tp->t_state) { 881 882 /* 883 * In FIN_WAIT_1 STATE in addition to the processing 884 * for the ESTABLISHED state if our FIN is now acknowledged 885 * then enter FIN_WAIT_2. 886 */ 887 case TCPS_FIN_WAIT_1: 888 if (ourfinisacked) { 889 /* 890 * If we can't receive any more 891 * data, then closing user can proceed. 892 * Starting the timer is contrary to the 893 * specification, but if we don't get a FIN 894 * we'll hang forever. 895 */ 896 if (so->so_state & SS_CANTRCVMORE) { 897 soisdisconnected(so); 898 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 899 } 900 tp->t_state = TCPS_FIN_WAIT_2; 901 } 902 break; 903 904 /* 905 * In CLOSING STATE in addition to the processing for 906 * the ESTABLISHED state if the ACK acknowledges our FIN 907 * then enter the TIME-WAIT state, otherwise ignore 908 * the segment. 909 */ 910 case TCPS_CLOSING: 911 if (ourfinisacked) { 912 tp->t_state = TCPS_TIME_WAIT; 913 tcp_canceltimers(tp); 914 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 915 soisdisconnected(so); 916 } 917 break; 918 919 /* 920 * In LAST_ACK, we may still be waiting for data to drain 921 * and/or to be acked, as well as for the ack of our FIN. 922 * If our FIN is now acknowledged, delete the TCB, 923 * enter the closed state and return. 924 */ 925 case TCPS_LAST_ACK: 926 if (ourfinisacked) { 927 tp = tcp_close(tp); 928 goto drop; 929 } 930 break; 931 932 /* 933 * In TIME_WAIT state the only thing that should arrive 934 * is a retransmission of the remote FIN. Acknowledge 935 * it and restart the finack timer. 936 */ 937 case TCPS_TIME_WAIT: 938 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 939 goto dropafterack; 940 } 941 } 942 943 step6: 944 /* 945 * Update window information. 946 * Don't look at window if no ACK: TAC's send garbage on first SYN. 947 */ 948 if ((tiflags & TH_ACK) && 949 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 950 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 951 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) { 952 /* keep track of pure window updates */ 953 if (ti->ti_len == 0 && 954 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd) 955 tcpstat.tcps_rcvwinupd++; 956 tp->snd_wnd = ti->ti_win; 957 tp->snd_wl1 = ti->ti_seq; 958 tp->snd_wl2 = ti->ti_ack; 959 if (tp->snd_wnd > tp->max_sndwnd) 960 tp->max_sndwnd = tp->snd_wnd; 961 needoutput = 1; 962 } 963 964 /* 965 * Process segments with URG. 966 */ 967 if ((tiflags & TH_URG) && ti->ti_urp && 968 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 969 /* 970 * This is a kludge, but if we receive and accept 971 * random urgent pointers, we'll crash in 972 * soreceive. It's hard to imagine someone 973 * actually wanting to send this much urgent data. 974 */ 975 if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { 976 ti->ti_urp = 0; /* XXX */ 977 tiflags &= ~TH_URG; /* XXX */ 978 goto dodata; /* XXX */ 979 } 980 /* 981 * If this segment advances the known urgent pointer, 982 * then mark the data stream. This should not happen 983 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 984 * a FIN has been received from the remote side. 985 * In these states we ignore the URG. 986 * 987 * According to RFC961 (Assigned Protocols), 988 * the urgent pointer points to the last octet 989 * of urgent data. We continue, however, 990 * to consider it to indicate the first octet 991 * of data past the urgent section 992 * as the original spec states. 993 */ 994 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 995 tp->rcv_up = ti->ti_seq + ti->ti_urp; 996 so->so_oobmark = so->so_rcv.sb_cc + 997 (tp->rcv_up - tp->rcv_nxt) - 1; 998 if (so->so_oobmark == 0) 999 so->so_state |= SS_RCVATMARK; 1000 sohasoutofband(so); 1001 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1002 } 1003 /* 1004 * Remove out of band data so doesn't get presented to user. 1005 * This can happen independent of advancing the URG pointer, 1006 * but if two URG's are pending at once, some out-of-band 1007 * data may creep in... ick. 1008 */ 1009 if (ti->ti_urp <= ti->ti_len 1010 #ifdef SO_OOBINLINE 1011 && (so->so_options & SO_OOBINLINE) == 0 1012 #endif 1013 ) 1014 tcp_pulloutofband(so, ti); 1015 } else 1016 /* 1017 * If no out of band data is expected, 1018 * pull receive urgent pointer along 1019 * with the receive window. 1020 */ 1021 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1022 tp->rcv_up = tp->rcv_nxt; 1023 dodata: /* XXX */ 1024 1025 /* 1026 * Process the segment text, merging it into the TCP sequencing queue, 1027 * and arranging for acknowledgment of receipt if necessary. 1028 * This process logically involves adjusting tp->rcv_wnd as data 1029 * is presented to the user (this happens in tcp_usrreq.c, 1030 * case PRU_RCVD). If a FIN has already been received on this 1031 * connection then we just ignore the text. 1032 */ 1033 if ((ti->ti_len || (tiflags&TH_FIN)) && 1034 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1035 TCP_REASS(tp, ti, m, so, tiflags); 1036 if (tcpnodelack == 0) 1037 tp->t_flags |= TF_DELACK; 1038 else 1039 tp->t_flags |= TF_ACKNOW; 1040 /* 1041 * Note the amount of data that peer has sent into 1042 * our window, in order to estimate the sender's 1043 * buffer size. 1044 */ 1045 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1046 if (len > tp->max_rcvd) 1047 tp->max_rcvd = len; 1048 } else { 1049 m_freem(m); 1050 tiflags &= ~TH_FIN; 1051 } 1052 1053 /* 1054 * If FIN is received ACK the FIN and let the user know 1055 * that the connection is closing. 1056 */ 1057 if (tiflags & TH_FIN) { 1058 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1059 socantrcvmore(so); 1060 tp->t_flags |= TF_ACKNOW; 1061 tp->rcv_nxt++; 1062 } 1063 switch (tp->t_state) { 1064 1065 /* 1066 * In SYN_RECEIVED and ESTABLISHED STATES 1067 * enter the CLOSE_WAIT state. 1068 */ 1069 case TCPS_SYN_RECEIVED: 1070 case TCPS_ESTABLISHED: 1071 tp->t_state = TCPS_CLOSE_WAIT; 1072 break; 1073 1074 /* 1075 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1076 * enter the CLOSING state. 1077 */ 1078 case TCPS_FIN_WAIT_1: 1079 tp->t_state = TCPS_CLOSING; 1080 break; 1081 1082 /* 1083 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1084 * starting the time-wait timer, turning off the other 1085 * standard timers. 1086 */ 1087 case TCPS_FIN_WAIT_2: 1088 tp->t_state = TCPS_TIME_WAIT; 1089 tcp_canceltimers(tp); 1090 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1091 soisdisconnected(so); 1092 break; 1093 1094 /* 1095 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1096 */ 1097 case TCPS_TIME_WAIT: 1098 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1099 break; 1100 } 1101 } 1102 if (so->so_options & SO_DEBUG) 1103 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1104 1105 /* 1106 * Return any desired output. 1107 */ 1108 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1109 (void) tcp_output(tp); 1110 return; 1111 1112 dropafterack: 1113 /* 1114 * Generate an ACK dropping incoming segment if it occupies 1115 * sequence space, where the ACK reflects our state. 1116 */ 1117 if (tiflags & TH_RST) 1118 goto drop; 1119 m_freem(m); 1120 tp->t_flags |= TF_ACKNOW; 1121 (void) tcp_output(tp); 1122 return; 1123 1124 dropwithreset: 1125 if (om) { 1126 (void) m_free(om); 1127 om = 0; 1128 } 1129 /* 1130 * Generate a RST, dropping incoming segment. 1131 * Make ACK acceptable to originator of segment. 1132 * Don't bother to respond if destination was broadcast. 1133 */ 1134 if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) 1135 goto drop; 1136 if (tiflags & TH_ACK) 1137 tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 1138 else { 1139 if (tiflags & TH_SYN) 1140 ti->ti_len++; 1141 tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1142 TH_RST|TH_ACK); 1143 } 1144 /* destroy temporarily created socket */ 1145 if (dropsocket) 1146 (void) soabort(so); 1147 return; 1148 1149 drop: 1150 if (om) 1151 (void) m_free(om); 1152 /* 1153 * Drop space held by incoming segment and return. 1154 */ 1155 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1156 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1157 m_freem(m); 1158 /* destroy temporarily created socket */ 1159 if (dropsocket) 1160 (void) soabort(so); 1161 return; 1162 } 1163 1164 tcp_dooptions(tp, om, ti) 1165 struct tcpcb *tp; 1166 struct mbuf *om; 1167 struct tcpiphdr *ti; 1168 { 1169 register u_char *cp; 1170 int opt, optlen, cnt; 1171 1172 cp = mtod(om, u_char *); 1173 cnt = om->m_len; 1174 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1175 opt = cp[0]; 1176 if (opt == TCPOPT_EOL) 1177 break; 1178 if (opt == TCPOPT_NOP) 1179 optlen = 1; 1180 else { 1181 optlen = cp[1]; 1182 if (optlen <= 0) 1183 break; 1184 } 1185 switch (opt) { 1186 1187 default: 1188 break; 1189 1190 case TCPOPT_MAXSEG: 1191 if (optlen != 4) 1192 continue; 1193 if (!(ti->ti_flags & TH_SYN)) 1194 continue; 1195 tp->t_maxseg = *(u_short *)(cp + 2); 1196 tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 1197 tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 1198 break; 1199 } 1200 } 1201 (void) m_free(om); 1202 } 1203 1204 /* 1205 * Pull out of band byte out of a segment so 1206 * it doesn't appear in the user's data queue. 1207 * It is still reflected in the segment length for 1208 * sequencing purposes. 1209 */ 1210 tcp_pulloutofband(so, ti) 1211 struct socket *so; 1212 struct tcpiphdr *ti; 1213 { 1214 register struct mbuf *m; 1215 int cnt = ti->ti_urp - 1; 1216 1217 m = dtom(ti); 1218 while (cnt >= 0) { 1219 if (m->m_len > cnt) { 1220 char *cp = mtod(m, caddr_t) + cnt; 1221 struct tcpcb *tp = sototcpcb(so); 1222 1223 tp->t_iobc = *cp; 1224 tp->t_oobflags |= TCPOOB_HAVEDATA; 1225 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1226 m->m_len--; 1227 return; 1228 } 1229 cnt -= m->m_len; 1230 m = m->m_next; 1231 if (m == 0) 1232 break; 1233 } 1234 panic("tcp_pulloutofband"); 1235 } 1236 1237 /* 1238 * Determine a reasonable value for maxseg size. 1239 * If the route is known, use one that can be handled 1240 * on the given interface without forcing IP to fragment. 1241 * If bigger than an mbuf cluster (MCLBYTES), round down to nearest size 1242 * to utilize large mbufs. 1243 * If interface pointer is unavailable, or the destination isn't local, 1244 * use a conservative size (512 or the default IP max size, but no more 1245 * than the mtu of the interface through which we route), 1246 * as we can't discover anything about intervening gateways or networks. 1247 * We also initialize the congestion/slow start window to be a single 1248 * segment if the destination isn't local; this information should 1249 * probably all be saved with the routing entry at the transport level. 1250 * 1251 * This is ugly, and doesn't belong at this level, but has to happen somehow. 1252 */ 1253 tcp_mss(tp) 1254 register struct tcpcb *tp; 1255 { 1256 struct route *ro; 1257 struct ifnet *ifp; 1258 int mss; 1259 struct inpcb *inp; 1260 1261 inp = tp->t_inpcb; 1262 ro = &inp->inp_route; 1263 if ((ro->ro_rt == (struct rtentry *)0) || 1264 (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1265 /* No route yet, so try to acquire one */ 1266 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1267 ro->ro_dst.sa_family = AF_INET; 1268 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1269 inp->inp_faddr; 1270 rtalloc(ro); 1271 } 1272 if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1273 return (TCP_MSS); 1274 } 1275 1276 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1277 #if (MCLBYTES & (MCLBYTES - 1)) == 0 1278 if (mss > MCLBYTES) 1279 mss &= ~(MCLBYTES-1); 1280 #else 1281 if (mss > MCLBYTES) 1282 mss = mss / MCLBYTES * MCLBYTES; 1283 #endif 1284 if (in_localaddr(inp->inp_faddr)) 1285 return (mss); 1286 1287 mss = MIN(mss, TCP_MSS); 1288 tp->snd_cwnd = mss; 1289 return (mss); 1290 } 1291 1292 #if BSD<43 1293 /* XXX this belongs in netinet/in.c */ 1294 in_localaddr(in) 1295 struct in_addr in; 1296 { 1297 register u_long i = ntohl(in.s_addr); 1298 register struct ifnet *ifp; 1299 register struct sockaddr_in *sin; 1300 register u_long mask; 1301 1302 if (IN_CLASSA(i)) 1303 mask = IN_CLASSA_NET; 1304 else if (IN_CLASSB(i)) 1305 mask = IN_CLASSB_NET; 1306 else if (IN_CLASSC(i)) 1307 mask = IN_CLASSC_NET; 1308 else 1309 return (0); 1310 1311 i &= mask; 1312 for (ifp = ifnet; ifp; ifp = ifp->if_next) { 1313 if (ifp->if_addr.sa_family != AF_INET) 1314 continue; 1315 sin = (struct sockaddr_in *)&ifp->if_addr; 1316 if ((sin->sin_addr.s_addr & mask) == i) 1317 return (1); 1318 } 1319 return (0); 1320 } 1321 #endif 1322