1 /* 2 * Copyright (c) 1982, 1986, 1988, 1990, 1993, 1994 3 * The Regents of the University of California. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 3. All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Berkeley and its contributors. 17 * 4. Neither the name of the University nor the names of its contributors 18 * may be used to endorse or promote products derived from this software 19 * without specific prior written permission. 20 * 21 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 22 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 23 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 24 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 25 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 26 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 27 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 28 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 29 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 30 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 31 * SUCH DAMAGE. 32 * 33 * from: @(#)tcp_input.c 8.5 (Berkeley) 4/10/94 34 * $Id: tcp_input.c,v 1.9 1994/05/13 06:06:39 mycroft Exp $ 35 */ 36 37 #ifndef TUBA_INCLUDE 38 #include <sys/param.h> 39 #include <sys/systm.h> 40 #include <sys/malloc.h> 41 #include <sys/mbuf.h> 42 #include <sys/protosw.h> 43 #include <sys/socket.h> 44 #include <sys/socketvar.h> 45 #include <sys/errno.h> 46 47 #include <net/if.h> 48 #include <net/route.h> 49 50 #include <netinet/in.h> 51 #include <netinet/in_systm.h> 52 #include <netinet/ip.h> 53 #include <netinet/in_pcb.h> 54 #include <netinet/ip_var.h> 55 #include <netinet/tcp.h> 56 #include <netinet/tcp_fsm.h> 57 #include <netinet/tcp_seq.h> 58 #include <netinet/tcp_timer.h> 59 #include <netinet/tcp_var.h> 60 #include <netinet/tcpip.h> 61 #include <netinet/tcp_debug.h> 62 63 int tcprexmtthresh = 3; 64 struct tcpiphdr tcp_saveti; 65 struct inpcb *tcp_last_inpcb = &tcb; 66 67 extern u_long sb_max; 68 69 #endif /* TUBA_INCLUDE */ 70 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) 71 72 /* for modulo comparisons of timestamps */ 73 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) 74 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) 75 76 77 /* 78 * Insert segment ti into reassembly queue of tcp with 79 * control block tp. Return TH_FIN if reassembly now includes 80 * a segment with FIN. The macro form does the common case inline 81 * (segment is the next to be received on an established connection, 82 * and the queue is empty), avoiding linkage into and removal 83 * from the queue and repetition of various conversions. 84 * Set DELACK for segments received in order, but ack immediately 85 * when segments are out of order (so fast retransmit can work). 86 */ 87 #define TCP_REASS(tp, ti, m, so, flags) { \ 88 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 89 (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 90 (tp)->t_state == TCPS_ESTABLISHED) { \ 91 if ((ti)->ti_flags & TH_PUSH) \ 92 tp->t_flags |= TF_ACKNOW; \ 93 else \ 94 tp->t_flags |= TF_DELACK; \ 95 (tp)->rcv_nxt += (ti)->ti_len; \ 96 flags = (ti)->ti_flags & TH_FIN; \ 97 tcpstat.tcps_rcvpack++;\ 98 tcpstat.tcps_rcvbyte += (ti)->ti_len;\ 99 sbappend(&(so)->so_rcv, (m)); \ 100 sorwakeup(so); \ 101 } else { \ 102 (flags) = tcp_reass((tp), (ti), (m)); \ 103 tp->t_flags |= TF_ACKNOW; \ 104 } \ 105 } 106 #ifndef TUBA_INCLUDE 107 108 int 109 tcp_reass(tp, ti, m) 110 register struct tcpcb *tp; 111 register struct tcpiphdr *ti; 112 struct mbuf *m; 113 { 114 register struct tcpiphdr *q; 115 struct socket *so = tp->t_inpcb->inp_socket; 116 int flags; 117 118 /* 119 * Call with ti==0 after become established to 120 * force pre-ESTABLISHED data up to user socket. 121 */ 122 if (ti == 0) 123 goto present; 124 125 /* 126 * Find a segment which begins after this one does. 127 */ 128 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 129 q = (struct tcpiphdr *)q->ti_next) 130 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 131 break; 132 133 /* 134 * If there is a preceding segment, it may provide some of 135 * our data already. If so, drop the data from the incoming 136 * segment. If it provides all of our data, drop us. 137 */ 138 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 139 register int i; 140 q = (struct tcpiphdr *)q->ti_prev; 141 /* conversion to int (in i) handles seq wraparound */ 142 i = q->ti_seq + q->ti_len - ti->ti_seq; 143 if (i > 0) { 144 if (i >= ti->ti_len) { 145 tcpstat.tcps_rcvduppack++; 146 tcpstat.tcps_rcvdupbyte += ti->ti_len; 147 m_freem(m); 148 return (0); 149 } 150 m_adj(m, i); 151 ti->ti_len -= i; 152 ti->ti_seq += i; 153 } 154 q = (struct tcpiphdr *)(q->ti_next); 155 } 156 tcpstat.tcps_rcvoopack++; 157 tcpstat.tcps_rcvoobyte += ti->ti_len; 158 REASS_MBUF(ti) = m; /* XXX */ 159 160 /* 161 * While we overlap succeeding segments trim them or, 162 * if they are completely covered, dequeue them. 163 */ 164 while (q != (struct tcpiphdr *)tp) { 165 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 166 if (i <= 0) 167 break; 168 if (i < q->ti_len) { 169 q->ti_seq += i; 170 q->ti_len -= i; 171 m_adj(REASS_MBUF(q), i); 172 break; 173 } 174 q = (struct tcpiphdr *)q->ti_next; 175 m = REASS_MBUF((struct tcpiphdr *)q->ti_prev); 176 remque(q->ti_prev); 177 m_freem(m); 178 } 179 180 /* 181 * Stick new segment in its place. 182 */ 183 insque(ti, q->ti_prev); 184 185 present: 186 /* 187 * Present data to user, advancing rcv_nxt through 188 * completed sequence space. 189 */ 190 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 191 return (0); 192 ti = tp->seg_next; 193 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 194 return (0); 195 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 196 return (0); 197 do { 198 tp->rcv_nxt += ti->ti_len; 199 flags = ti->ti_flags & TH_FIN; 200 remque(ti); 201 m = REASS_MBUF(ti); 202 ti = (struct tcpiphdr *)ti->ti_next; 203 if (so->so_state & SS_CANTRCVMORE) 204 m_freem(m); 205 else 206 sbappend(&so->so_rcv, m); 207 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 208 sorwakeup(so); 209 return (flags); 210 } 211 212 /* 213 * TCP input routine, follows pages 65-76 of the 214 * protocol specification dated September, 1981 very closely. 215 */ 216 void 217 tcp_input(m, iphlen) 218 register struct mbuf *m; 219 int iphlen; 220 { 221 register struct tcpiphdr *ti; 222 register struct inpcb *inp; 223 caddr_t optp = NULL; 224 int optlen; 225 int len, tlen, off; 226 register struct tcpcb *tp = 0; 227 register int tiflags; 228 struct socket *so; 229 int todrop, acked, ourfinisacked, needoutput = 0; 230 short ostate; 231 struct in_addr laddr; 232 int dropsocket = 0; 233 int iss = 0; 234 u_long tiwin, ts_val, ts_ecr; 235 int ts_present = 0; 236 237 tcpstat.tcps_rcvtotal++; 238 /* 239 * Get IP and TCP header together in first mbuf. 240 * Note: IP leaves IP header in first mbuf. 241 */ 242 ti = mtod(m, struct tcpiphdr *); 243 if (iphlen > sizeof (struct ip)) 244 ip_stripoptions(m, (struct mbuf *)0); 245 if (m->m_len < sizeof (struct tcpiphdr)) { 246 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 247 tcpstat.tcps_rcvshort++; 248 return; 249 } 250 ti = mtod(m, struct tcpiphdr *); 251 } 252 253 /* 254 * Checksum extended TCP header and data. 255 */ 256 tlen = ((struct ip *)ti)->ip_len; 257 len = sizeof (struct ip) + tlen; 258 ti->ti_next = ti->ti_prev = 0; 259 ti->ti_x1 = 0; 260 ti->ti_len = (u_short)tlen; 261 HTONS(ti->ti_len); 262 if (ti->ti_sum = in_cksum(m, len)) { 263 tcpstat.tcps_rcvbadsum++; 264 goto drop; 265 } 266 #endif /* TUBA_INCLUDE */ 267 268 /* 269 * Check that TCP offset makes sense, 270 * pull out TCP options and adjust length. XXX 271 */ 272 off = ti->ti_off << 2; 273 if (off < sizeof (struct tcphdr) || off > tlen) { 274 tcpstat.tcps_rcvbadoff++; 275 goto drop; 276 } 277 tlen -= off; 278 ti->ti_len = tlen; 279 if (off > sizeof (struct tcphdr)) { 280 if (m->m_len < sizeof(struct ip) + off) { 281 if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 282 tcpstat.tcps_rcvshort++; 283 return; 284 } 285 ti = mtod(m, struct tcpiphdr *); 286 } 287 optlen = off - sizeof (struct tcphdr); 288 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 289 /* 290 * Do quick retrieval of timestamp options ("options 291 * prediction?"). If timestamp is the only option and it's 292 * formatted as recommended in RFC 1323 appendix A, we 293 * quickly get the values now and not bother calling 294 * tcp_dooptions(), etc. 295 */ 296 if ((optlen == TCPOLEN_TSTAMP_APPA || 297 (optlen > TCPOLEN_TSTAMP_APPA && 298 optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 299 *(u_long *)optp == htonl(TCPOPT_TSTAMP_HDR) && 300 (ti->ti_flags & TH_SYN) == 0) { 301 ts_present = 1; 302 ts_val = ntohl(*(u_long *)(optp + 4)); 303 ts_ecr = ntohl(*(u_long *)(optp + 8)); 304 optp = NULL; /* we've parsed the options */ 305 } 306 } 307 tiflags = ti->ti_flags; 308 309 /* 310 * Convert TCP protocol specific fields to host format. 311 */ 312 NTOHL(ti->ti_seq); 313 NTOHL(ti->ti_ack); 314 NTOHS(ti->ti_win); 315 NTOHS(ti->ti_urp); 316 317 /* 318 * Locate pcb for segment. 319 */ 320 findpcb: 321 inp = tcp_last_inpcb; 322 if (inp->inp_lport != ti->ti_dport || 323 inp->inp_fport != ti->ti_sport || 324 inp->inp_faddr.s_addr != ti->ti_src.s_addr || 325 inp->inp_laddr.s_addr != ti->ti_dst.s_addr) { 326 inp = in_pcblookup(&tcb, ti->ti_src, ti->ti_sport, 327 ti->ti_dst, ti->ti_dport, INPLOOKUP_WILDCARD); 328 if (inp) 329 tcp_last_inpcb = inp; 330 ++tcpstat.tcps_pcbcachemiss; 331 } 332 333 /* 334 * If the state is CLOSED (i.e., TCB does not exist) then 335 * all data in the incoming segment is discarded. 336 * If the TCB exists but is in CLOSED state, it is embryonic, 337 * but should either do a listen or a connect soon. 338 */ 339 if (inp == 0) 340 goto dropwithreset; 341 tp = intotcpcb(inp); 342 if (tp == 0) 343 goto dropwithreset; 344 if (tp->t_state == TCPS_CLOSED) 345 goto drop; 346 347 /* Unscale the window into a 32-bit value. */ 348 if ((tiflags & TH_SYN) == 0) 349 tiwin = ti->ti_win << tp->snd_scale; 350 else 351 tiwin = ti->ti_win; 352 353 so = inp->inp_socket; 354 if (so->so_options & (SO_DEBUG|SO_ACCEPTCONN)) { 355 if (so->so_options & SO_DEBUG) { 356 ostate = tp->t_state; 357 tcp_saveti = *ti; 358 } 359 if (so->so_options & SO_ACCEPTCONN) { 360 so = sonewconn(so, 0); 361 if (so == 0) 362 goto drop; 363 /* 364 * This is ugly, but .... 365 * 366 * Mark socket as temporary until we're 367 * committed to keeping it. The code at 368 * ``drop'' and ``dropwithreset'' check the 369 * flag dropsocket to see if the temporary 370 * socket created here should be discarded. 371 * We mark the socket as discardable until 372 * we're committed to it below in TCPS_LISTEN. 373 */ 374 dropsocket++; 375 inp = (struct inpcb *)so->so_pcb; 376 inp->inp_laddr = ti->ti_dst; 377 inp->inp_lport = ti->ti_dport; 378 #if BSD>=43 379 inp->inp_options = ip_srcroute(); 380 #endif 381 tp = intotcpcb(inp); 382 tp->t_state = TCPS_LISTEN; 383 384 /* Compute proper scaling value from buffer space 385 */ 386 while (tp->request_r_scale < TCP_MAX_WINSHIFT && 387 TCP_MAXWIN << tp->request_r_scale < so->so_rcv.sb_hiwat) 388 tp->request_r_scale++; 389 } 390 } 391 392 /* 393 * Segment received on connection. 394 * Reset idle time and keep-alive timer. 395 */ 396 tp->t_idle = 0; 397 tp->t_timer[TCPT_KEEP] = tcp_keepidle; 398 399 /* 400 * Process options if not in LISTEN state, 401 * else do it below (after getting remote address). 402 */ 403 if (optp && tp->t_state != TCPS_LISTEN) 404 tcp_dooptions(tp, optp, optlen, ti, 405 &ts_present, &ts_val, &ts_ecr); 406 407 /* 408 * Header prediction: check for the two common cases 409 * of a uni-directional data xfer. If the packet has 410 * no control flags, is in-sequence, the window didn't 411 * change and we're not retransmitting, it's a 412 * candidate. If the length is zero and the ack moved 413 * forward, we're the sender side of the xfer. Just 414 * free the data acked & wake any higher level process 415 * that was blocked waiting for space. If the length 416 * is non-zero and the ack didn't move, we're the 417 * receiver side. If we're getting packets in-order 418 * (the reassembly queue is empty), add the data to 419 * the socket buffer and note that we need a delayed ack. 420 */ 421 if (tp->t_state == TCPS_ESTABLISHED && 422 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 423 (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && 424 ti->ti_seq == tp->rcv_nxt && 425 tiwin && tiwin == tp->snd_wnd && 426 tp->snd_nxt == tp->snd_max) { 427 428 /* 429 * If last ACK falls within this segment's sequence numbers, 430 * record the timestamp. 431 */ 432 if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 433 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) { 434 tp->ts_recent_age = tcp_now; 435 tp->ts_recent = ts_val; 436 } 437 438 if (ti->ti_len == 0) { 439 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 440 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 441 tp->snd_cwnd >= tp->snd_wnd) { 442 /* 443 * this is a pure ack for outstanding data. 444 */ 445 ++tcpstat.tcps_predack; 446 if (ts_present) 447 tcp_xmit_timer(tp, tcp_now-ts_ecr+1); 448 else if (tp->t_rtt && 449 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 450 tcp_xmit_timer(tp, tp->t_rtt); 451 acked = ti->ti_ack - tp->snd_una; 452 tcpstat.tcps_rcvackpack++; 453 tcpstat.tcps_rcvackbyte += acked; 454 sbdrop(&so->so_snd, acked); 455 tp->snd_una = ti->ti_ack; 456 m_freem(m); 457 458 /* 459 * If all outstanding data are acked, stop 460 * retransmit timer, otherwise restart timer 461 * using current (possibly backed-off) value. 462 * If process is waiting for space, 463 * wakeup/selwakeup/signal. If data 464 * are ready to send, let tcp_output 465 * decide between more output or persist. 466 */ 467 if (tp->snd_una == tp->snd_max) 468 tp->t_timer[TCPT_REXMT] = 0; 469 else if (tp->t_timer[TCPT_PERSIST] == 0) 470 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 471 472 if (so->so_snd.sb_flags & SB_NOTIFY) 473 sowwakeup(so); 474 if (so->so_snd.sb_cc) 475 (void) tcp_output(tp); 476 return; 477 } 478 } else if (ti->ti_ack == tp->snd_una && 479 tp->seg_next == (struct tcpiphdr *)tp && 480 ti->ti_len <= sbspace(&so->so_rcv)) { 481 /* 482 * this is a pure, in-sequence data packet 483 * with nothing on the reassembly queue and 484 * we have enough buffer space to take it. 485 */ 486 ++tcpstat.tcps_preddat; 487 tp->rcv_nxt += ti->ti_len; 488 tcpstat.tcps_rcvpack++; 489 tcpstat.tcps_rcvbyte += ti->ti_len; 490 /* 491 * Drop TCP, IP headers and TCP options then add data 492 * to socket buffer. 493 */ 494 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 495 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 496 sbappend(&so->so_rcv, m); 497 sorwakeup(so); 498 if (ti->ti_flags & TH_PUSH) 499 tp->t_flags |= TF_ACKNOW; 500 else 501 tp->t_flags |= TF_DELACK; 502 return; 503 } 504 } 505 506 /* 507 * Drop TCP, IP headers and TCP options. 508 */ 509 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 510 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 511 512 /* 513 * Calculate amount of space in receive window, 514 * and then do TCP input processing. 515 * Receive window is amount of space in rcv queue, 516 * but not less than advertised window. 517 */ 518 { int win; 519 520 win = sbspace(&so->so_rcv); 521 if (win < 0) 522 win = 0; 523 tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 524 } 525 526 switch (tp->t_state) { 527 528 /* 529 * If the state is LISTEN then ignore segment if it contains an RST. 530 * If the segment contains an ACK then it is bad and send a RST. 531 * If it does not contain a SYN then it is not interesting; drop it. 532 * Don't bother responding if the destination was a broadcast. 533 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 534 * tp->iss, and send a segment: 535 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 536 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 537 * Fill in remote peer address fields if not previously specified. 538 * Enter SYN_RECEIVED state, and process any other fields of this 539 * segment in this state. 540 */ 541 case TCPS_LISTEN: { 542 struct mbuf *am; 543 register struct sockaddr_in *sin; 544 545 if (tiflags & TH_RST) 546 goto drop; 547 if (tiflags & TH_ACK) 548 goto dropwithreset; 549 if ((tiflags & TH_SYN) == 0) 550 goto drop; 551 /* 552 * RFC1122 4.2.3.10, p. 104: discard bcast/mcast SYN 553 * in_broadcast() should never return true on a received 554 * packet with M_BCAST not set. 555 */ 556 if (m->m_flags & (M_BCAST|M_MCAST) || 557 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 558 goto drop; 559 am = m_get(M_DONTWAIT, MT_SONAME); /* XXX */ 560 if (am == NULL) 561 goto drop; 562 am->m_len = sizeof (struct sockaddr_in); 563 sin = mtod(am, struct sockaddr_in *); 564 sin->sin_family = AF_INET; 565 sin->sin_len = sizeof(*sin); 566 sin->sin_addr = ti->ti_src; 567 sin->sin_port = ti->ti_sport; 568 bzero((caddr_t)sin->sin_zero, sizeof(sin->sin_zero)); 569 laddr = inp->inp_laddr; 570 if (inp->inp_laddr.s_addr == INADDR_ANY) 571 inp->inp_laddr = ti->ti_dst; 572 if (in_pcbconnect(inp, am)) { 573 inp->inp_laddr = laddr; 574 (void) m_free(am); 575 goto drop; 576 } 577 (void) m_free(am); 578 tp->t_template = tcp_template(tp); 579 if (tp->t_template == 0) { 580 tp = tcp_drop(tp, ENOBUFS); 581 dropsocket = 0; /* socket is already gone */ 582 goto drop; 583 } 584 if (optp) 585 tcp_dooptions(tp, optp, optlen, ti, 586 &ts_present, &ts_val, &ts_ecr); 587 if (iss) 588 tp->iss = iss; 589 else 590 tp->iss = tcp_iss; 591 tcp_iss += TCP_ISSINCR/2; 592 tp->irs = ti->ti_seq; 593 tcp_sendseqinit(tp); 594 tcp_rcvseqinit(tp); 595 tp->t_flags |= TF_ACKNOW; 596 tp->t_state = TCPS_SYN_RECEIVED; 597 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 598 dropsocket = 0; /* committed to socket */ 599 tcpstat.tcps_accepts++; 600 goto trimthenstep6; 601 } 602 603 /* 604 * If the state is SYN_SENT: 605 * if seg contains an ACK, but not for our SYN, drop the input. 606 * if seg contains a RST, then drop the connection. 607 * if seg does not contain SYN, then drop it. 608 * Otherwise this is an acceptable SYN segment 609 * initialize tp->rcv_nxt and tp->irs 610 * if seg contains ack then advance tp->snd_una 611 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 612 * arrange for segment to be acked (eventually) 613 * continue processing rest of data/controls, beginning with URG 614 */ 615 case TCPS_SYN_SENT: 616 if ((tiflags & TH_ACK) && 617 (SEQ_LEQ(ti->ti_ack, tp->iss) || 618 SEQ_GT(ti->ti_ack, tp->snd_max))) 619 goto dropwithreset; 620 if (tiflags & TH_RST) { 621 if (tiflags & TH_ACK) 622 tp = tcp_drop(tp, ECONNREFUSED); 623 goto drop; 624 } 625 if ((tiflags & TH_SYN) == 0) 626 goto drop; 627 if (tiflags & TH_ACK) { 628 tp->snd_una = ti->ti_ack; 629 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 630 tp->snd_nxt = tp->snd_una; 631 } 632 tp->t_timer[TCPT_REXMT] = 0; 633 tp->irs = ti->ti_seq; 634 tcp_rcvseqinit(tp); 635 tp->t_flags |= TF_ACKNOW; 636 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 637 tcpstat.tcps_connects++; 638 soisconnected(so); 639 tp->t_state = TCPS_ESTABLISHED; 640 /* Do window scaling on this connection? */ 641 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 642 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 643 tp->snd_scale = tp->requested_s_scale; 644 tp->rcv_scale = tp->request_r_scale; 645 } 646 (void) tcp_reass(tp, (struct tcpiphdr *)0, 647 (struct mbuf *)0); 648 /* 649 * if we didn't have to retransmit the SYN, 650 * use its rtt as our initial srtt & rtt var. 651 */ 652 if (tp->t_rtt) 653 tcp_xmit_timer(tp, tp->t_rtt); 654 } else 655 tp->t_state = TCPS_SYN_RECEIVED; 656 657 trimthenstep6: 658 /* 659 * Advance ti->ti_seq to correspond to first data byte. 660 * If data, trim to stay within window, 661 * dropping FIN if necessary. 662 */ 663 ti->ti_seq++; 664 if (ti->ti_len > tp->rcv_wnd) { 665 todrop = ti->ti_len - tp->rcv_wnd; 666 m_adj(m, -todrop); 667 ti->ti_len = tp->rcv_wnd; 668 tiflags &= ~TH_FIN; 669 tcpstat.tcps_rcvpackafterwin++; 670 tcpstat.tcps_rcvbyteafterwin += todrop; 671 } 672 tp->snd_wl1 = ti->ti_seq - 1; 673 tp->rcv_up = ti->ti_seq; 674 goto step6; 675 } 676 677 /* 678 * States other than LISTEN or SYN_SENT. 679 * First check timestamp, if present. 680 * Then check that at least some bytes of segment are within 681 * receive window. If segment begins before rcv_nxt, 682 * drop leading data (and SYN); if nothing left, just ack. 683 * 684 * RFC 1323 PAWS: If we have a timestamp reply on this segment 685 * and it's less than ts_recent, drop it. 686 */ 687 if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && 688 TSTMP_LT(ts_val, tp->ts_recent)) { 689 690 /* Check to see if ts_recent is over 24 days old. */ 691 if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 692 /* 693 * Invalidate ts_recent. If this segment updates 694 * ts_recent, the age will be reset later and ts_recent 695 * will get a valid value. If it does not, setting 696 * ts_recent to zero will at least satisfy the 697 * requirement that zero be placed in the timestamp 698 * echo reply when ts_recent isn't valid. The 699 * age isn't reset until we get a valid ts_recent 700 * because we don't want out-of-order segments to be 701 * dropped when ts_recent is old. 702 */ 703 tp->ts_recent = 0; 704 } else { 705 tcpstat.tcps_rcvduppack++; 706 tcpstat.tcps_rcvdupbyte += ti->ti_len; 707 tcpstat.tcps_pawsdrop++; 708 goto dropafterack; 709 } 710 } 711 712 todrop = tp->rcv_nxt - ti->ti_seq; 713 if (todrop > 0) { 714 if (tiflags & TH_SYN) { 715 tiflags &= ~TH_SYN; 716 ti->ti_seq++; 717 if (ti->ti_urp > 1) 718 ti->ti_urp--; 719 else 720 tiflags &= ~TH_URG; 721 todrop--; 722 } 723 if (todrop >= ti->ti_len) { 724 /* 725 * Any valid FIN must be to the left of the 726 * window. At this point, FIN must be a 727 * duplicate or out-of-sequence, so drop it. 728 */ 729 tiflags &= ~TH_FIN; 730 /* 731 * Send ACK to resynchronize, and drop any data, 732 * but keep on processing for RST or ACK. 733 */ 734 tp->t_flags |= TF_ACKNOW; 735 tcpstat.tcps_rcvdupbyte += todrop = ti->ti_len; 736 tcpstat.tcps_rcvduppack++; 737 } else { 738 tcpstat.tcps_rcvpartduppack++; 739 tcpstat.tcps_rcvpartdupbyte += todrop; 740 } 741 m_adj(m, todrop); 742 ti->ti_seq += todrop; 743 ti->ti_len -= todrop; 744 if (ti->ti_urp > todrop) 745 ti->ti_urp -= todrop; 746 else { 747 tiflags &= ~TH_URG; 748 ti->ti_urp = 0; 749 } 750 } 751 752 /* 753 * If new data are received on a connection after the 754 * user processes are gone, then RST the other end. 755 */ 756 if ((so->so_state & SS_NOFDREF) && 757 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 758 tp = tcp_close(tp); 759 tcpstat.tcps_rcvafterclose++; 760 goto dropwithreset; 761 } 762 763 /* 764 * If segment ends after window, drop trailing data 765 * (and PUSH and FIN); if nothing left, just ACK. 766 */ 767 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 768 if (todrop > 0) { 769 tcpstat.tcps_rcvpackafterwin++; 770 if (todrop >= ti->ti_len) { 771 tcpstat.tcps_rcvbyteafterwin += ti->ti_len; 772 /* 773 * If a new connection request is received 774 * while in TIME_WAIT, drop the old connection 775 * and start over if the sequence numbers 776 * are above the previous ones. 777 */ 778 if (tiflags & TH_SYN && 779 tp->t_state == TCPS_TIME_WAIT && 780 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 781 iss = tp->rcv_nxt + TCP_ISSINCR; 782 tp = tcp_close(tp); 783 goto findpcb; 784 } 785 /* 786 * If window is closed can only take segments at 787 * window edge, and have to drop data and PUSH from 788 * incoming segments. Continue processing, but 789 * remember to ack. Otherwise, drop segment 790 * and ack. 791 */ 792 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 793 tp->t_flags |= TF_ACKNOW; 794 tcpstat.tcps_rcvwinprobe++; 795 } else 796 goto dropafterack; 797 } else 798 tcpstat.tcps_rcvbyteafterwin += todrop; 799 m_adj(m, -todrop); 800 ti->ti_len -= todrop; 801 tiflags &= ~(TH_PUSH|TH_FIN); 802 } 803 804 /* 805 * If last ACK falls within this segment's sequence numbers, 806 * record its timestamp. 807 */ 808 if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 809 SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len + 810 ((tiflags & (TH_SYN|TH_FIN)) != 0))) { 811 tp->ts_recent_age = tcp_now; 812 tp->ts_recent = ts_val; 813 } 814 815 /* 816 * If the RST bit is set examine the state: 817 * SYN_RECEIVED STATE: 818 * If passive open, return to LISTEN state. 819 * If active open, inform user that connection was refused. 820 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 821 * Inform user that connection was reset, and close tcb. 822 * CLOSING, LAST_ACK, TIME_WAIT STATES 823 * Close the tcb. 824 */ 825 if (tiflags&TH_RST) switch (tp->t_state) { 826 827 case TCPS_SYN_RECEIVED: 828 so->so_error = ECONNREFUSED; 829 goto close; 830 831 case TCPS_ESTABLISHED: 832 case TCPS_FIN_WAIT_1: 833 case TCPS_FIN_WAIT_2: 834 case TCPS_CLOSE_WAIT: 835 so->so_error = ECONNRESET; 836 close: 837 tp->t_state = TCPS_CLOSED; 838 tcpstat.tcps_drops++; 839 tp = tcp_close(tp); 840 goto drop; 841 842 case TCPS_CLOSING: 843 case TCPS_LAST_ACK: 844 case TCPS_TIME_WAIT: 845 tp = tcp_close(tp); 846 goto drop; 847 } 848 849 /* 850 * If a SYN is in the window, then this is an 851 * error and we send an RST and drop the connection. 852 */ 853 if (tiflags & TH_SYN) { 854 tp = tcp_drop(tp, ECONNRESET); 855 goto dropwithreset; 856 } 857 858 /* 859 * If the ACK bit is off we drop the segment and return. 860 */ 861 if ((tiflags & TH_ACK) == 0) 862 goto drop; 863 864 /* 865 * Ack processing. 866 */ 867 switch (tp->t_state) { 868 869 /* 870 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 871 * ESTABLISHED state and continue processing, otherwise 872 * send an RST. 873 */ 874 case TCPS_SYN_RECEIVED: 875 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 876 SEQ_GT(ti->ti_ack, tp->snd_max)) 877 goto dropwithreset; 878 tcpstat.tcps_connects++; 879 soisconnected(so); 880 tp->t_state = TCPS_ESTABLISHED; 881 /* Do window scaling? */ 882 if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 883 (TF_RCVD_SCALE|TF_REQ_SCALE)) { 884 tp->snd_scale = tp->requested_s_scale; 885 tp->rcv_scale = tp->request_r_scale; 886 } 887 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); 888 tp->snd_wl1 = ti->ti_seq - 1; 889 /* fall into ... */ 890 891 /* 892 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 893 * ACKs. If the ack is in the range 894 * tp->snd_una < ti->ti_ack <= tp->snd_max 895 * then advance tp->snd_una to ti->ti_ack and drop 896 * data from the retransmission queue. If this ACK reflects 897 * more up to date window information we update our window information. 898 */ 899 case TCPS_ESTABLISHED: 900 case TCPS_FIN_WAIT_1: 901 case TCPS_FIN_WAIT_2: 902 case TCPS_CLOSE_WAIT: 903 case TCPS_CLOSING: 904 case TCPS_LAST_ACK: 905 case TCPS_TIME_WAIT: 906 907 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 908 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 909 tcpstat.tcps_rcvdupack++; 910 /* 911 * If we have outstanding data (other than 912 * a window probe), this is a completely 913 * duplicate ack (ie, window info didn't 914 * change), the ack is the biggest we've 915 * seen and we've seen exactly our rexmt 916 * threshhold of them, assume a packet 917 * has been dropped and retransmit it. 918 * Kludge snd_nxt & the congestion 919 * window so we send only this one 920 * packet. 921 * 922 * We know we're losing at the current 923 * window size so do congestion avoidance 924 * (set ssthresh to half the current window 925 * and pull our congestion window back to 926 * the new ssthresh). 927 * 928 * Dup acks mean that packets have left the 929 * network (they're now cached at the receiver) 930 * so bump cwnd by the amount in the receiver 931 * to keep a constant cwnd packets in the 932 * network. 933 */ 934 if (tp->t_timer[TCPT_REXMT] == 0 || 935 ti->ti_ack != tp->snd_una) 936 tp->t_dupacks = 0; 937 else if (++tp->t_dupacks == tcprexmtthresh) { 938 tcp_seq onxt = tp->snd_nxt; 939 u_int win = 940 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 941 tp->t_maxseg; 942 943 if (win < 2) 944 win = 2; 945 tp->snd_ssthresh = win * tp->t_maxseg; 946 tp->t_timer[TCPT_REXMT] = 0; 947 tp->t_rtt = 0; 948 tp->snd_nxt = ti->ti_ack; 949 tp->snd_cwnd = tp->t_maxseg; 950 (void) tcp_output(tp); 951 tp->snd_cwnd = tp->snd_ssthresh + 952 tp->t_maxseg * tp->t_dupacks; 953 if (SEQ_GT(onxt, tp->snd_nxt)) 954 tp->snd_nxt = onxt; 955 goto drop; 956 } else if (tp->t_dupacks > tcprexmtthresh) { 957 tp->snd_cwnd += tp->t_maxseg; 958 (void) tcp_output(tp); 959 goto drop; 960 } 961 } else 962 tp->t_dupacks = 0; 963 break; 964 } 965 /* 966 * If the congestion window was inflated to account 967 * for the other side's cached packets, retract it. 968 */ 969 if (tp->t_dupacks > tcprexmtthresh && 970 tp->snd_cwnd > tp->snd_ssthresh) 971 tp->snd_cwnd = tp->snd_ssthresh; 972 tp->t_dupacks = 0; 973 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 974 tcpstat.tcps_rcvacktoomuch++; 975 goto dropafterack; 976 } 977 acked = ti->ti_ack - tp->snd_una; 978 tcpstat.tcps_rcvackpack++; 979 tcpstat.tcps_rcvackbyte += acked; 980 981 /* 982 * If we have a timestamp reply, update smoothed 983 * round trip time. If no timestamp is present but 984 * transmit timer is running and timed sequence 985 * number was acked, update smoothed round trip time. 986 * Since we now have an rtt measurement, cancel the 987 * timer backoff (cf., Phil Karn's retransmit alg.). 988 * Recompute the initial retransmit timer. 989 */ 990 if (ts_present) 991 tcp_xmit_timer(tp, tcp_now-ts_ecr+1); 992 else if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 993 tcp_xmit_timer(tp,tp->t_rtt); 994 995 /* 996 * If all outstanding data is acked, stop retransmit 997 * timer and remember to restart (more output or persist). 998 * If there is more data to be acked, restart retransmit 999 * timer, using current (possibly backed-off) value. 1000 */ 1001 if (ti->ti_ack == tp->snd_max) { 1002 tp->t_timer[TCPT_REXMT] = 0; 1003 needoutput = 1; 1004 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1005 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1006 /* 1007 * When new data is acked, open the congestion window. 1008 * If the window gives us less than ssthresh packets 1009 * in flight, open exponentially (maxseg per packet). 1010 * Otherwise open linearly: maxseg per window 1011 * (maxseg^2 / cwnd per packet), plus a constant 1012 * fraction of a packet (maxseg/8) to help larger windows 1013 * open quickly enough. 1014 */ 1015 { 1016 register u_int cw = tp->snd_cwnd; 1017 register u_int incr = tp->t_maxseg; 1018 1019 if (cw > tp->snd_ssthresh) 1020 incr = incr * incr / cw + incr / 8; 1021 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1022 } 1023 if (acked > so->so_snd.sb_cc) { 1024 tp->snd_wnd -= so->so_snd.sb_cc; 1025 sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 1026 ourfinisacked = 1; 1027 } else { 1028 sbdrop(&so->so_snd, acked); 1029 tp->snd_wnd -= acked; 1030 ourfinisacked = 0; 1031 } 1032 if (so->so_snd.sb_flags & SB_NOTIFY) 1033 sowwakeup(so); 1034 tp->snd_una = ti->ti_ack; 1035 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1036 tp->snd_nxt = tp->snd_una; 1037 1038 switch (tp->t_state) { 1039 1040 /* 1041 * In FIN_WAIT_1 STATE in addition to the processing 1042 * for the ESTABLISHED state if our FIN is now acknowledged 1043 * then enter FIN_WAIT_2. 1044 */ 1045 case TCPS_FIN_WAIT_1: 1046 if (ourfinisacked) { 1047 /* 1048 * If we can't receive any more 1049 * data, then closing user can proceed. 1050 * Starting the timer is contrary to the 1051 * specification, but if we don't get a FIN 1052 * we'll hang forever. 1053 */ 1054 if (so->so_state & SS_CANTRCVMORE) { 1055 soisdisconnected(so); 1056 tp->t_timer[TCPT_2MSL] = tcp_maxidle; 1057 } 1058 tp->t_state = TCPS_FIN_WAIT_2; 1059 } 1060 break; 1061 1062 /* 1063 * In CLOSING STATE in addition to the processing for 1064 * the ESTABLISHED state if the ACK acknowledges our FIN 1065 * then enter the TIME-WAIT state, otherwise ignore 1066 * the segment. 1067 */ 1068 case TCPS_CLOSING: 1069 if (ourfinisacked) { 1070 tp->t_state = TCPS_TIME_WAIT; 1071 tcp_canceltimers(tp); 1072 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1073 soisdisconnected(so); 1074 } 1075 break; 1076 1077 /* 1078 * In LAST_ACK, we may still be waiting for data to drain 1079 * and/or to be acked, as well as for the ack of our FIN. 1080 * If our FIN is now acknowledged, delete the TCB, 1081 * enter the closed state and return. 1082 */ 1083 case TCPS_LAST_ACK: 1084 if (ourfinisacked) { 1085 tp = tcp_close(tp); 1086 goto drop; 1087 } 1088 break; 1089 1090 /* 1091 * In TIME_WAIT state the only thing that should arrive 1092 * is a retransmission of the remote FIN. Acknowledge 1093 * it and restart the finack timer. 1094 */ 1095 case TCPS_TIME_WAIT: 1096 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1097 goto dropafterack; 1098 } 1099 } 1100 1101 step6: 1102 /* 1103 * Update window information. 1104 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1105 */ 1106 if ((tiflags & TH_ACK) && 1107 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 1108 (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 1109 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))) { 1110 /* keep track of pure window updates */ 1111 if (ti->ti_len == 0 && 1112 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1113 tcpstat.tcps_rcvwinupd++; 1114 tp->snd_wnd = tiwin; 1115 tp->snd_wl1 = ti->ti_seq; 1116 tp->snd_wl2 = ti->ti_ack; 1117 if (tp->snd_wnd > tp->max_sndwnd) 1118 tp->max_sndwnd = tp->snd_wnd; 1119 needoutput = 1; 1120 } 1121 1122 /* 1123 * Process segments with URG. 1124 */ 1125 if ((tiflags & TH_URG) && ti->ti_urp && 1126 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1127 /* 1128 * This is a kludge, but if we receive and accept 1129 * random urgent pointers, we'll crash in 1130 * soreceive. It's hard to imagine someone 1131 * actually wanting to send this much urgent data. 1132 */ 1133 if (ti->ti_urp + so->so_rcv.sb_cc > sb_max) { 1134 ti->ti_urp = 0; /* XXX */ 1135 tiflags &= ~TH_URG; /* XXX */ 1136 goto dodata; /* XXX */ 1137 } 1138 /* 1139 * If this segment advances the known urgent pointer, 1140 * then mark the data stream. This should not happen 1141 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1142 * a FIN has been received from the remote side. 1143 * In these states we ignore the URG. 1144 * 1145 * According to RFC961 (Assigned Protocols), 1146 * the urgent pointer points to the last octet 1147 * of urgent data. We continue, however, 1148 * to consider it to indicate the first octet 1149 * of data past the urgent section as the original 1150 * spec states (in one of two places). 1151 */ 1152 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1153 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1154 so->so_oobmark = so->so_rcv.sb_cc + 1155 (tp->rcv_up - tp->rcv_nxt) - 1; 1156 if (so->so_oobmark == 0) 1157 so->so_state |= SS_RCVATMARK; 1158 sohasoutofband(so); 1159 tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 1160 } 1161 /* 1162 * Remove out of band data so doesn't get presented to user. 1163 * This can happen independent of advancing the URG pointer, 1164 * but if two URG's are pending at once, some out-of-band 1165 * data may creep in... ick. 1166 */ 1167 if (ti->ti_urp <= ti->ti_len 1168 #ifdef SO_OOBINLINE 1169 && (so->so_options & SO_OOBINLINE) == 0 1170 #endif 1171 ) 1172 tcp_pulloutofband(so, ti, m); 1173 } else 1174 /* 1175 * If no out of band data is expected, 1176 * pull receive urgent pointer along 1177 * with the receive window. 1178 */ 1179 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1180 tp->rcv_up = tp->rcv_nxt; 1181 dodata: /* XXX */ 1182 1183 /* 1184 * Process the segment text, merging it into the TCP sequencing queue, 1185 * and arranging for acknowledgment of receipt if necessary. 1186 * This process logically involves adjusting tp->rcv_wnd as data 1187 * is presented to the user (this happens in tcp_usrreq.c, 1188 * case PRU_RCVD). If a FIN has already been received on this 1189 * connection then we just ignore the text. 1190 */ 1191 if ((ti->ti_len || (tiflags&TH_FIN)) && 1192 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1193 TCP_REASS(tp, ti, m, so, tiflags); 1194 /* 1195 * Note the amount of data that peer has sent into 1196 * our window, in order to estimate the sender's 1197 * buffer size. 1198 */ 1199 len = so->so_rcv.sb_hiwat - (tp->rcv_adv - tp->rcv_nxt); 1200 } else { 1201 m_freem(m); 1202 tiflags &= ~TH_FIN; 1203 } 1204 1205 /* 1206 * If FIN is received ACK the FIN and let the user know 1207 * that the connection is closing. 1208 */ 1209 if (tiflags & TH_FIN) { 1210 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1211 socantrcvmore(so); 1212 tp->t_flags |= TF_ACKNOW; 1213 tp->rcv_nxt++; 1214 } 1215 switch (tp->t_state) { 1216 1217 /* 1218 * In SYN_RECEIVED and ESTABLISHED STATES 1219 * enter the CLOSE_WAIT state. 1220 */ 1221 case TCPS_SYN_RECEIVED: 1222 case TCPS_ESTABLISHED: 1223 tp->t_state = TCPS_CLOSE_WAIT; 1224 break; 1225 1226 /* 1227 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1228 * enter the CLOSING state. 1229 */ 1230 case TCPS_FIN_WAIT_1: 1231 tp->t_state = TCPS_CLOSING; 1232 break; 1233 1234 /* 1235 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1236 * starting the time-wait timer, turning off the other 1237 * standard timers. 1238 */ 1239 case TCPS_FIN_WAIT_2: 1240 tp->t_state = TCPS_TIME_WAIT; 1241 tcp_canceltimers(tp); 1242 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1243 soisdisconnected(so); 1244 break; 1245 1246 /* 1247 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1248 */ 1249 case TCPS_TIME_WAIT: 1250 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1251 break; 1252 } 1253 } 1254 if (so->so_options & SO_DEBUG) 1255 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 1256 1257 /* 1258 * Return any desired output. 1259 */ 1260 if (needoutput || (tp->t_flags & TF_ACKNOW)) 1261 (void) tcp_output(tp); 1262 return; 1263 1264 dropafterack: 1265 /* 1266 * Generate an ACK dropping incoming segment if it occupies 1267 * sequence space, where the ACK reflects our state. 1268 */ 1269 if (tiflags & TH_RST) 1270 goto drop; 1271 m_freem(m); 1272 tp->t_flags |= TF_ACKNOW; 1273 (void) tcp_output(tp); 1274 return; 1275 1276 dropwithreset: 1277 /* 1278 * Generate a RST, dropping incoming segment. 1279 * Make ACK acceptable to originator of segment. 1280 * Don't bother to respond if destination was broadcast/multicast. 1281 */ 1282 if ((tiflags & TH_RST) || m->m_flags & (M_BCAST|M_MCAST) || 1283 IN_MULTICAST(ntohl(ti->ti_dst.s_addr))) 1284 goto drop; 1285 if (tiflags & TH_ACK) 1286 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1287 else { 1288 if (tiflags & TH_SYN) 1289 ti->ti_len++; 1290 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1291 TH_RST|TH_ACK); 1292 } 1293 /* destroy temporarily created socket */ 1294 if (dropsocket) 1295 (void) soabort(so); 1296 return; 1297 1298 drop: 1299 /* 1300 * Drop space held by incoming segment and return. 1301 */ 1302 if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 1303 tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 1304 m_freem(m); 1305 /* destroy temporarily created socket */ 1306 if (dropsocket) 1307 (void) soabort(so); 1308 return; 1309 #ifndef TUBA_INCLUDE 1310 } 1311 1312 void 1313 tcp_dooptions(tp, cp, cnt, ti, ts_present, ts_val, ts_ecr) 1314 struct tcpcb *tp; 1315 u_char *cp; 1316 int cnt; 1317 struct tcpiphdr *ti; 1318 int *ts_present; 1319 u_long *ts_val, *ts_ecr; 1320 { 1321 u_short mss; 1322 int opt, optlen; 1323 1324 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1325 opt = cp[0]; 1326 if (opt == TCPOPT_EOL) 1327 break; 1328 if (opt == TCPOPT_NOP) 1329 optlen = 1; 1330 else { 1331 optlen = cp[1]; 1332 if (optlen <= 0) 1333 break; 1334 } 1335 switch (opt) { 1336 1337 default: 1338 continue; 1339 1340 case TCPOPT_MAXSEG: 1341 if (optlen != TCPOLEN_MAXSEG) 1342 continue; 1343 if (!(ti->ti_flags & TH_SYN)) 1344 continue; 1345 bcopy((char *) cp + 2, (char *) &mss, sizeof(mss)); 1346 NTOHS(mss); 1347 (void) tcp_mss(tp, mss); /* sets t_maxseg */ 1348 break; 1349 1350 case TCPOPT_WINDOW: 1351 if (optlen != TCPOLEN_WINDOW) 1352 continue; 1353 if (!(ti->ti_flags & TH_SYN)) 1354 continue; 1355 tp->t_flags |= TF_RCVD_SCALE; 1356 tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1357 break; 1358 1359 case TCPOPT_TIMESTAMP: 1360 if (optlen != TCPOLEN_TIMESTAMP) 1361 continue; 1362 *ts_present = 1; 1363 bcopy((char *)cp + 2, (char *) ts_val, sizeof(*ts_val)); 1364 NTOHL(*ts_val); 1365 bcopy((char *)cp + 6, (char *) ts_ecr, sizeof(*ts_ecr)); 1366 NTOHL(*ts_ecr); 1367 1368 /* 1369 * A timestamp received in a SYN makes 1370 * it ok to send timestamp requests and replies. 1371 */ 1372 if (ti->ti_flags & TH_SYN) { 1373 tp->t_flags |= TF_RCVD_TSTMP; 1374 tp->ts_recent = *ts_val; 1375 tp->ts_recent_age = tcp_now; 1376 } 1377 break; 1378 } 1379 } 1380 } 1381 1382 /* 1383 * Pull out of band byte out of a segment so 1384 * it doesn't appear in the user's data queue. 1385 * It is still reflected in the segment length for 1386 * sequencing purposes. 1387 */ 1388 void 1389 tcp_pulloutofband(so, ti, m) 1390 struct socket *so; 1391 struct tcpiphdr *ti; 1392 register struct mbuf *m; 1393 { 1394 int cnt = ti->ti_urp - 1; 1395 1396 while (cnt >= 0) { 1397 if (m->m_len > cnt) { 1398 char *cp = mtod(m, caddr_t) + cnt; 1399 struct tcpcb *tp = sototcpcb(so); 1400 1401 tp->t_iobc = *cp; 1402 tp->t_oobflags |= TCPOOB_HAVEDATA; 1403 bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1404 m->m_len--; 1405 return; 1406 } 1407 cnt -= m->m_len; 1408 m = m->m_next; 1409 if (m == 0) 1410 break; 1411 } 1412 panic("tcp_pulloutofband"); 1413 } 1414 1415 /* 1416 * Collect new round-trip time estimate 1417 * and update averages and current timeout. 1418 */ 1419 void 1420 tcp_xmit_timer(tp, rtt) 1421 register struct tcpcb *tp; 1422 short rtt; 1423 { 1424 register short delta; 1425 1426 tcpstat.tcps_rttupdated++; 1427 if (tp->t_srtt != 0) { 1428 /* 1429 * srtt is stored as fixed point with 3 bits after the 1430 * binary point (i.e., scaled by 8). The following magic 1431 * is equivalent to the smoothing algorithm in rfc793 with 1432 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1433 * point). Adjust rtt to origin 0. 1434 */ 1435 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT); 1436 if ((tp->t_srtt += delta) <= 0) 1437 tp->t_srtt = 1; 1438 /* 1439 * We accumulate a smoothed rtt variance (actually, a 1440 * smoothed mean difference), then set the retransmit 1441 * timer to smoothed rtt + 4 times the smoothed variance. 1442 * rttvar is stored as fixed point with 2 bits after the 1443 * binary point (scaled by 4). The following is 1444 * equivalent to rfc793 smoothing with an alpha of .75 1445 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1446 * rfc793's wired-in beta. 1447 */ 1448 if (delta < 0) 1449 delta = -delta; 1450 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 1451 if ((tp->t_rttvar += delta) <= 0) 1452 tp->t_rttvar = 1; 1453 } else { 1454 /* 1455 * No rtt measurement yet - use the unsmoothed rtt. 1456 * Set the variance to half the rtt (so our first 1457 * retransmit happens at 3*rtt). 1458 */ 1459 tp->t_srtt = rtt << TCP_RTT_SHIFT; 1460 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 1461 } 1462 tp->t_rtt = 0; 1463 tp->t_rxtshift = 0; 1464 1465 /* 1466 * the retransmit should happen at rtt + 4 * rttvar. 1467 * Because of the way we do the smoothing, srtt and rttvar 1468 * will each average +1/2 tick of bias. When we compute 1469 * the retransmit timer, we want 1/2 tick of rounding and 1470 * 1 extra tick because of +-1/2 tick uncertainty in the 1471 * firing of the timer. The bias will give us exactly the 1472 * 1.5 tick we need. But, because the bias is 1473 * statistical, we have to test that we don't drop below 1474 * the minimum feasible timer (which is 2 ticks). 1475 */ 1476 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 1477 tp->t_rttmin, TCPTV_REXMTMAX); 1478 1479 /* 1480 * We received an ack for a packet that wasn't retransmitted; 1481 * it is probably safe to discard any error indications we've 1482 * received recently. This isn't quite right, but close enough 1483 * for now (a route might have failed after we sent a segment, 1484 * and the return path might not be symmetrical). 1485 */ 1486 tp->t_softerror = 0; 1487 } 1488 1489 /* 1490 * Determine a reasonable value for maxseg size. 1491 * If the route is known, check route for mtu. 1492 * If none, use an mss that can be handled on the outgoing 1493 * interface without forcing IP to fragment; if bigger than 1494 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 1495 * to utilize large mbufs. If no route is found, route has no mtu, 1496 * or the destination isn't local, use a default, hopefully conservative 1497 * size (usually 512 or the default IP max size, but no more than the mtu 1498 * of the interface), as we can't discover anything about intervening 1499 * gateways or networks. We also initialize the congestion/slow start 1500 * window to be a single segment if the destination isn't local. 1501 * While looking at the routing entry, we also initialize other path-dependent 1502 * parameters from pre-set or cached values in the routing entry. 1503 */ 1504 int 1505 tcp_mss(tp, offer) 1506 register struct tcpcb *tp; 1507 u_int offer; 1508 { 1509 struct route *ro; 1510 register struct rtentry *rt; 1511 struct ifnet *ifp; 1512 register int rtt, mss; 1513 u_long bufsize; 1514 struct inpcb *inp; 1515 struct socket *so; 1516 extern int tcp_mssdflt; 1517 1518 inp = tp->t_inpcb; 1519 ro = &inp->inp_route; 1520 1521 if ((rt = ro->ro_rt) == (struct rtentry *)0) { 1522 /* No route yet, so try to acquire one */ 1523 if (inp->inp_faddr.s_addr != INADDR_ANY) { 1524 ro->ro_dst.sa_family = AF_INET; 1525 ro->ro_dst.sa_len = sizeof(ro->ro_dst); 1526 ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1527 inp->inp_faddr; 1528 rtalloc(ro); 1529 } 1530 if ((rt = ro->ro_rt) == (struct rtentry *)0) 1531 return (tcp_mssdflt); 1532 } 1533 ifp = rt->rt_ifp; 1534 so = inp->inp_socket; 1535 1536 #ifdef RTV_MTU /* if route characteristics exist ... */ 1537 /* 1538 * While we're here, check if there's an initial rtt 1539 * or rttvar. Convert from the route-table units 1540 * to scaled multiples of the slow timeout timer. 1541 */ 1542 if (tp->t_srtt == 0 && (rtt = rt->rt_rmx.rmx_rtt)) { 1543 /* 1544 * XXX the lock bit for MTU indicates that the value 1545 * is also a minimum value; this is subject to time. 1546 */ 1547 if (rt->rt_rmx.rmx_locks & RTV_RTT) 1548 tp->t_rttmin = rtt / (RTM_RTTUNIT / PR_SLOWHZ); 1549 tp->t_srtt = rtt / (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTT_SCALE)); 1550 if (rt->rt_rmx.rmx_rttvar) 1551 tp->t_rttvar = rt->rt_rmx.rmx_rttvar / 1552 (RTM_RTTUNIT / (PR_SLOWHZ * TCP_RTTVAR_SCALE)); 1553 else 1554 /* default variation is +- 1 rtt */ 1555 tp->t_rttvar = 1556 tp->t_srtt * TCP_RTTVAR_SCALE / TCP_RTT_SCALE; 1557 TCPT_RANGESET(tp->t_rxtcur, 1558 ((tp->t_srtt >> 2) + tp->t_rttvar) >> 1, 1559 tp->t_rttmin, TCPTV_REXMTMAX); 1560 } 1561 /* 1562 * if there's an mtu associated with the route, use it 1563 */ 1564 if (rt->rt_rmx.rmx_mtu) 1565 mss = rt->rt_rmx.rmx_mtu - sizeof(struct tcpiphdr); 1566 else 1567 #endif /* RTV_MTU */ 1568 { 1569 mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1570 #if (MCLBYTES & (MCLBYTES - 1)) == 0 1571 if (mss > MCLBYTES) 1572 mss &= ~(MCLBYTES-1); 1573 #else 1574 if (mss > MCLBYTES) 1575 mss = mss / MCLBYTES * MCLBYTES; 1576 #endif 1577 if (!in_localaddr(inp->inp_faddr)) 1578 mss = min(mss, tcp_mssdflt); 1579 } 1580 /* 1581 * The current mss, t_maxseg, is initialized to the default value. 1582 * If we compute a smaller value, reduce the current mss. 1583 * If we compute a larger value, return it for use in sending 1584 * a max seg size option, but don't store it for use 1585 * unless we received an offer at least that large from peer. 1586 * However, do not accept offers under 32 bytes. 1587 */ 1588 if (offer) 1589 mss = min(mss, offer); 1590 mss = max(mss, 32); /* sanity */ 1591 if (mss < tp->t_maxseg || offer != 0) { 1592 /* 1593 * If there's a pipesize, change the socket buffer 1594 * to that size. Make the socket buffers an integral 1595 * number of mss units; if the mss is larger than 1596 * the socket buffer, decrease the mss. 1597 */ 1598 #ifdef RTV_SPIPE 1599 if ((bufsize = rt->rt_rmx.rmx_sendpipe) == 0) 1600 #endif 1601 bufsize = so->so_snd.sb_hiwat; 1602 if (bufsize < mss) 1603 mss = bufsize; 1604 else { 1605 bufsize = roundup(bufsize, mss); 1606 if (bufsize > sb_max) 1607 bufsize = sb_max; 1608 (void)sbreserve(&so->so_snd, bufsize); 1609 } 1610 tp->t_maxseg = mss; 1611 1612 #ifdef RTV_RPIPE 1613 if ((bufsize = rt->rt_rmx.rmx_recvpipe) == 0) 1614 #endif 1615 bufsize = so->so_rcv.sb_hiwat; 1616 if (bufsize > mss) { 1617 bufsize = roundup(bufsize, mss); 1618 if (bufsize > sb_max) 1619 bufsize = sb_max; 1620 (void)sbreserve(&so->so_rcv, bufsize); 1621 } 1622 } 1623 tp->snd_cwnd = mss; 1624 1625 #ifdef RTV_SSTHRESH 1626 if (rt->rt_rmx.rmx_ssthresh) { 1627 /* 1628 * There's some sort of gateway or interface 1629 * buffer limit on the path. Use this to set 1630 * the slow start threshhold, but set the 1631 * threshold to no less than 2*mss. 1632 */ 1633 tp->snd_ssthresh = max(2 * mss, rt->rt_rmx.rmx_ssthresh); 1634 } 1635 #endif /* RTV_MTU */ 1636 return (mss); 1637 } 1638 #endif /* TUBA_INCLUDE */ 1639