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. Neither the name of the University nor the names of its contributors 14 * may be used to endorse or promote products derived from this software 15 * without specific prior written permission. 16 * 17 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 18 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 19 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 20 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 21 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 22 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 23 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 24 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 25 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 26 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 27 * SUCH DAMAGE. 28 * 29 * @(#)tcp_input.c 8.5 (Berkeley) 4/10/94 30 * tcp_input.c,v 1.10 1994/10/13 18:36:32 wollman Exp 31 */ 32 33 /* 34 * Changes and additions relating to SLiRP 35 * Copyright (c) 1995 Danny Gasparovski. 36 * 37 * Please read the file COPYRIGHT for the 38 * terms and conditions of the copyright. 39 */ 40 41 #include <slirp.h> 42 #include "ip_icmp.h" 43 44 struct socket tcb; 45 46 #define TCPREXMTTHRESH 3 47 struct socket *tcp_last_so = &tcb; 48 49 tcp_seq tcp_iss; /* tcp initial send seq # */ 50 51 #define TCP_PAWS_IDLE (24 * 24 * 60 * 60 * PR_SLOWHZ) 52 53 /* for modulo comparisons of timestamps */ 54 #define TSTMP_LT(a,b) ((int)((a)-(b)) < 0) 55 #define TSTMP_GEQ(a,b) ((int)((a)-(b)) >= 0) 56 57 /* 58 * Insert segment ti into reassembly queue of tcp with 59 * control block tp. Return TH_FIN if reassembly now includes 60 * a segment with FIN. The macro form does the common case inline 61 * (segment is the next to be received on an established connection, 62 * and the queue is empty), avoiding linkage into and removal 63 * from the queue and repetition of various conversions. 64 * Set DELACK for segments received in order, but ack immediately 65 * when segments are out of order (so fast retransmit can work). 66 */ 67 #ifdef TCP_ACK_HACK 68 #define TCP_REASS(tp, ti, m, so, flags) {\ 69 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 70 tcpfrag_list_empty(tp) && \ 71 (tp)->t_state == TCPS_ESTABLISHED) {\ 72 if (ti->ti_flags & TH_PUSH) \ 73 tp->t_flags |= TF_ACKNOW; \ 74 else \ 75 tp->t_flags |= TF_DELACK; \ 76 (tp)->rcv_nxt += (ti)->ti_len; \ 77 flags = (ti)->ti_flags & TH_FIN; \ 78 STAT(tcpstat.tcps_rcvpack++); \ 79 STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \ 80 if (so->so_emu) { \ 81 if (tcp_emu((so),(m))) sbappend((so), (m)); \ 82 } else \ 83 sbappend((so), (m)); \ 84 /* sorwakeup(so); */ \ 85 } else {\ 86 (flags) = tcp_reass((tp), (ti), (m)); \ 87 tp->t_flags |= TF_ACKNOW; \ 88 } \ 89 } 90 #else 91 #define TCP_REASS(tp, ti, m, so, flags) { \ 92 if ((ti)->ti_seq == (tp)->rcv_nxt && \ 93 tcpfrag_list_empty(tp) && \ 94 (tp)->t_state == TCPS_ESTABLISHED) { \ 95 tp->t_flags |= TF_DELACK; \ 96 (tp)->rcv_nxt += (ti)->ti_len; \ 97 flags = (ti)->ti_flags & TH_FIN; \ 98 STAT(tcpstat.tcps_rcvpack++); \ 99 STAT(tcpstat.tcps_rcvbyte += (ti)->ti_len); \ 100 if (so->so_emu) { \ 101 if (tcp_emu((so),(m))) sbappend(so, (m)); \ 102 } else \ 103 sbappend((so), (m)); \ 104 /* sorwakeup(so); */ \ 105 } else { \ 106 (flags) = tcp_reass((tp), (ti), (m)); \ 107 tp->t_flags |= TF_ACKNOW; \ 108 } \ 109 } 110 #endif 111 static void tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, 112 struct tcpiphdr *ti); 113 static void tcp_xmit_timer(register struct tcpcb *tp, int rtt); 114 115 static int 116 tcp_reass(register struct tcpcb *tp, register struct tcpiphdr *ti, 117 struct mbuf *m) 118 { 119 register struct tcpiphdr *q; 120 struct socket *so = tp->t_socket; 121 int flags; 122 123 /* 124 * Call with ti==NULL after become established to 125 * force pre-ESTABLISHED data up to user socket. 126 */ 127 if (ti == NULL) 128 goto present; 129 130 /* 131 * Find a segment which begins after this one does. 132 */ 133 for (q = tcpfrag_list_first(tp); !tcpfrag_list_end(q, tp); 134 q = tcpiphdr_next(q)) 135 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 136 break; 137 138 /* 139 * If there is a preceding segment, it may provide some of 140 * our data already. If so, drop the data from the incoming 141 * segment. If it provides all of our data, drop us. 142 */ 143 if (!tcpfrag_list_end(tcpiphdr_prev(q), tp)) { 144 register int i; 145 q = tcpiphdr_prev(q); 146 /* conversion to int (in i) handles seq wraparound */ 147 i = q->ti_seq + q->ti_len - ti->ti_seq; 148 if (i > 0) { 149 if (i >= ti->ti_len) { 150 STAT(tcpstat.tcps_rcvduppack++); 151 STAT(tcpstat.tcps_rcvdupbyte += ti->ti_len); 152 m_freem(m); 153 /* 154 * Try to present any queued data 155 * at the left window edge to the user. 156 * This is needed after the 3-WHS 157 * completes. 158 */ 159 goto present; /* ??? */ 160 } 161 m_adj(m, i); 162 ti->ti_len -= i; 163 ti->ti_seq += i; 164 } 165 q = tcpiphdr_next(q); 166 } 167 STAT(tcpstat.tcps_rcvoopack++); 168 STAT(tcpstat.tcps_rcvoobyte += ti->ti_len); 169 ti->ti_mbuf = m; 170 171 /* 172 * While we overlap succeeding segments trim them or, 173 * if they are completely covered, dequeue them. 174 */ 175 while (!tcpfrag_list_end(q, tp)) { 176 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 177 if (i <= 0) 178 break; 179 if (i < q->ti_len) { 180 q->ti_seq += i; 181 q->ti_len -= i; 182 m_adj(q->ti_mbuf, i); 183 break; 184 } 185 q = tcpiphdr_next(q); 186 m = tcpiphdr_prev(q)->ti_mbuf; 187 remque(tcpiphdr2qlink(tcpiphdr_prev(q))); 188 m_freem(m); 189 } 190 191 /* 192 * Stick new segment in its place. 193 */ 194 insque(tcpiphdr2qlink(ti), tcpiphdr2qlink(tcpiphdr_prev(q))); 195 196 present: 197 /* 198 * Present data to user, advancing rcv_nxt through 199 * completed sequence space. 200 */ 201 if (!TCPS_HAVEESTABLISHED(tp->t_state)) 202 return (0); 203 ti = tcpfrag_list_first(tp); 204 if (tcpfrag_list_end(ti, tp) || ti->ti_seq != tp->rcv_nxt) 205 return (0); 206 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 207 return (0); 208 do { 209 tp->rcv_nxt += ti->ti_len; 210 flags = ti->ti_flags & TH_FIN; 211 remque(tcpiphdr2qlink(ti)); 212 m = ti->ti_mbuf; 213 ti = tcpiphdr_next(ti); 214 /* if (so->so_state & SS_FCANTRCVMORE) */ 215 if (so->so_state & SS_FCANTSENDMORE) 216 m_freem(m); 217 else { 218 if (so->so_emu) { 219 if (tcp_emu(so,m)) sbappend(so, m); 220 } else 221 sbappend(so, m); 222 } 223 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 224 /* sorwakeup(so); */ 225 return (flags); 226 } 227 228 /* 229 * TCP input routine, follows pages 65-76 of the 230 * protocol specification dated September, 1981 very closely. 231 */ 232 void 233 tcp_input(struct mbuf *m, int iphlen, struct socket *inso) 234 { 235 struct ip save_ip, *ip; 236 register struct tcpiphdr *ti; 237 caddr_t optp = NULL; 238 int optlen = 0; 239 int len, tlen, off; 240 register struct tcpcb *tp = NULL; 241 register int tiflags; 242 struct socket *so = NULL; 243 int todrop, acked, ourfinisacked, needoutput = 0; 244 /* int dropsocket = 0; */ 245 int iss = 0; 246 u_long tiwin; 247 int ret; 248 /* int ts_present = 0; */ 249 struct ex_list *ex_ptr; 250 251 DEBUG_CALL("tcp_input"); 252 DEBUG_ARGS((dfd," m = %8lx iphlen = %2d inso = %lx\n", 253 (long )m, iphlen, (long )inso )); 254 255 /* 256 * If called with m == 0, then we're continuing the connect 257 */ 258 if (m == NULL) { 259 so = inso; 260 261 /* Re-set a few variables */ 262 tp = sototcpcb(so); 263 m = so->so_m; 264 so->so_m = NULL; 265 ti = so->so_ti; 266 tiwin = ti->ti_win; 267 tiflags = ti->ti_flags; 268 269 goto cont_conn; 270 } 271 272 273 STAT(tcpstat.tcps_rcvtotal++); 274 /* 275 * Get IP and TCP header together in first mbuf. 276 * Note: IP leaves IP header in first mbuf. 277 */ 278 ti = mtod(m, struct tcpiphdr *); 279 if (iphlen > sizeof(struct ip )) { 280 ip_stripoptions(m, (struct mbuf *)0); 281 iphlen=sizeof(struct ip ); 282 } 283 /* XXX Check if too short */ 284 285 286 /* 287 * Save a copy of the IP header in case we want restore it 288 * for sending an ICMP error message in response. 289 */ 290 ip=mtod(m, struct ip *); 291 save_ip = *ip; 292 save_ip.ip_len+= iphlen; 293 294 /* 295 * Checksum extended TCP header and data. 296 */ 297 tlen = ((struct ip *)ti)->ip_len; 298 tcpiphdr2qlink(ti)->next = tcpiphdr2qlink(ti)->prev = NULL; 299 memset(&ti->ti_i.ih_mbuf, 0 , sizeof(struct mbuf_ptr)); 300 ti->ti_x1 = 0; 301 ti->ti_len = htons((u_int16_t)tlen); 302 len = sizeof(struct ip ) + tlen; 303 /* keep checksum for ICMP reply 304 * ti->ti_sum = cksum(m, len); 305 * if (ti->ti_sum) { */ 306 if(cksum(m, len)) { 307 STAT(tcpstat.tcps_rcvbadsum++); 308 goto drop; 309 } 310 311 /* 312 * Check that TCP offset makes sense, 313 * pull out TCP options and adjust length. XXX 314 */ 315 off = ti->ti_off << 2; 316 if (off < sizeof (struct tcphdr) || off > tlen) { 317 STAT(tcpstat.tcps_rcvbadoff++); 318 goto drop; 319 } 320 tlen -= off; 321 ti->ti_len = tlen; 322 if (off > sizeof (struct tcphdr)) { 323 optlen = off - sizeof (struct tcphdr); 324 optp = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 325 326 /* 327 * Do quick retrieval of timestamp options ("options 328 * prediction?"). If timestamp is the only option and it's 329 * formatted as recommended in RFC 1323 appendix A, we 330 * quickly get the values now and not bother calling 331 * tcp_dooptions(), etc. 332 */ 333 /* if ((optlen == TCPOLEN_TSTAMP_APPA || 334 * (optlen > TCPOLEN_TSTAMP_APPA && 335 * optp[TCPOLEN_TSTAMP_APPA] == TCPOPT_EOL)) && 336 * *(u_int32_t *)optp == htonl(TCPOPT_TSTAMP_HDR) && 337 * (ti->ti_flags & TH_SYN) == 0) { 338 * ts_present = 1; 339 * ts_val = ntohl(*(u_int32_t *)(optp + 4)); 340 * ts_ecr = ntohl(*(u_int32_t *)(optp + 8)); 341 * optp = NULL; / * we've parsed the options * / 342 * } 343 */ 344 } 345 tiflags = ti->ti_flags; 346 347 /* 348 * Convert TCP protocol specific fields to host format. 349 */ 350 NTOHL(ti->ti_seq); 351 NTOHL(ti->ti_ack); 352 NTOHS(ti->ti_win); 353 NTOHS(ti->ti_urp); 354 355 /* 356 * Drop TCP, IP headers and TCP options. 357 */ 358 m->m_data += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 359 m->m_len -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 360 361 if (slirp_restrict) { 362 for (ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) 363 if (ex_ptr->ex_fport == port_geth(ti->ti_dport) && 364 (ip_geth(ti->ti_dst) & 0xff) == ex_ptr->ex_addr) 365 break; 366 367 if (!ex_ptr) 368 goto drop; 369 } 370 /* 371 * Locate pcb for segment. 372 */ 373 findso: 374 so = tcp_last_so; 375 { 376 uint32_t srcip = ip_geth(ti->ti_src); 377 uint32_t dstip = ip_geth(ti->ti_dst); 378 uint16_t dstport = port_geth(ti->ti_dport); 379 uint16_t srcport = port_geth(ti->ti_sport); 380 381 if (so->so_faddr_port != dstport || 382 so->so_laddr_port != srcport || 383 so->so_laddr_ip != srcip || 384 so->so_faddr_ip != dstip) { 385 so = solookup(&tcb, srcip, srcport, dstip, dstport); 386 if (so) 387 tcp_last_so = so; 388 STAT(tcpstat.tcps_socachemiss++); 389 } 390 } 391 /* 392 * If the state is CLOSED (i.e., TCB does not exist) then 393 * all data in the incoming segment is discarded. 394 * If the TCB exists but is in CLOSED state, it is embryonic, 395 * but should either do a listen or a connect soon. 396 * 397 * state == CLOSED means we've done socreate() but haven't 398 * attached it to a protocol yet... 399 * 400 * XXX If a TCB does not exist, and the TH_SYN flag is 401 * the only flag set, then create a session, mark it 402 * as if it was LISTENING, and continue... 403 */ 404 if (so == NULL) { 405 if ((tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) != TH_SYN) 406 goto dropwithreset; 407 408 if ((so = socreate()) == NULL) 409 goto dropwithreset; 410 if (tcp_attach(so) < 0) { 411 free(so); /* Not sofree (if it failed, it's not insqued) */ 412 goto dropwithreset; 413 } 414 415 sbreserve(&so->so_snd, TCP_SNDSPACE); 416 sbreserve(&so->so_rcv, TCP_RCVSPACE); 417 418 /* tcp_last_so = so; */ /* XXX ? */ 419 /* tp = sototcpcb(so); */ 420 421 so->so_laddr_ip = ip_geth(ti->ti_src); 422 so->so_laddr_port = port_geth(ti->ti_sport); 423 so->so_faddr_ip = ip_geth(ti->ti_dst); 424 so->so_faddr_port = port_geth(ti->ti_dport); 425 426 if ((so->so_iptos = tcp_tos(so)) == 0) 427 so->so_iptos = ((struct ip *)ti)->ip_tos; 428 429 tp = sototcpcb(so); 430 tp->t_state = TCPS_LISTEN; 431 } 432 433 /* 434 * If this is a still-connecting socket, this probably 435 * a retransmit of the SYN. Whether it's a retransmit SYN 436 * or something else, we nuke it. 437 */ 438 if (so->so_state & SS_ISFCONNECTING) 439 goto drop; 440 441 tp = sototcpcb(so); 442 443 /* XXX Should never fail */ 444 if (tp == NULL) 445 goto dropwithreset; 446 if (tp->t_state == TCPS_CLOSED) 447 goto drop; 448 449 /* Unscale the window into a 32-bit value. */ 450 /* if ((tiflags & TH_SYN) == 0) 451 * tiwin = ti->ti_win << tp->snd_scale; 452 * else 453 */ 454 tiwin = ti->ti_win; 455 456 /* 457 * Segment received on connection. 458 * Reset idle time and keep-alive timer. 459 */ 460 tp->t_idle = 0; 461 if (SO_OPTIONS) 462 tp->t_timer[TCPT_KEEP] = TCPTV_KEEPINTVL; 463 else 464 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_IDLE; 465 466 /* 467 * Process options if not in LISTEN state, 468 * else do it below (after getting remote address). 469 */ 470 if (optp && tp->t_state != TCPS_LISTEN) 471 tcp_dooptions(tp, (u_char *)optp, optlen, ti); 472 /* , */ 473 /* &ts_present, &ts_val, &ts_ecr); */ 474 475 /* 476 * Header prediction: check for the two common cases 477 * of a uni-directional data xfer. If the packet has 478 * no control flags, is in-sequence, the window didn't 479 * change and we're not retransmitting, it's a 480 * candidate. If the length is zero and the ack moved 481 * forward, we're the sender side of the xfer. Just 482 * free the data acked & wake any higher level process 483 * that was blocked waiting for space. If the length 484 * is non-zero and the ack didn't move, we're the 485 * receiver side. If we're getting packets in-order 486 * (the reassembly queue is empty), add the data to 487 * the socket buffer and note that we need a delayed ack. 488 * 489 * XXX Some of these tests are not needed 490 * eg: the tiwin == tp->snd_wnd prevents many more 491 * predictions.. with no *real* advantage.. 492 */ 493 if (tp->t_state == TCPS_ESTABLISHED && 494 (tiflags & (TH_SYN|TH_FIN|TH_RST|TH_URG|TH_ACK)) == TH_ACK && 495 /* (!ts_present || TSTMP_GEQ(ts_val, tp->ts_recent)) && */ 496 ti->ti_seq == tp->rcv_nxt && 497 tiwin && tiwin == tp->snd_wnd && 498 tp->snd_nxt == tp->snd_max) { 499 /* 500 * If last ACK falls within this segment's sequence numbers, 501 * record the timestamp. 502 */ 503 /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 504 * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len)) { 505 * tp->ts_recent_age = tcp_now; 506 * tp->ts_recent = ts_val; 507 * } 508 */ 509 if (ti->ti_len == 0) { 510 if (SEQ_GT(ti->ti_ack, tp->snd_una) && 511 SEQ_LEQ(ti->ti_ack, tp->snd_max) && 512 tp->snd_cwnd >= tp->snd_wnd) { 513 /* 514 * this is a pure ack for outstanding data. 515 */ 516 STAT(tcpstat.tcps_predack++); 517 /* if (ts_present) 518 * tcp_xmit_timer(tp, tcp_now-ts_ecr+1); 519 * else 520 */ if (tp->t_rtt && 521 SEQ_GT(ti->ti_ack, tp->t_rtseq)) 522 tcp_xmit_timer(tp, tp->t_rtt); 523 acked = ti->ti_ack - tp->snd_una; 524 STAT(tcpstat.tcps_rcvackpack++); 525 STAT(tcpstat.tcps_rcvackbyte += acked); 526 sbdrop(&so->so_snd, acked); 527 tp->snd_una = ti->ti_ack; 528 m_freem(m); 529 530 /* 531 * If all outstanding data are acked, stop 532 * retransmit timer, otherwise restart timer 533 * using current (possibly backed-off) value. 534 * If process is waiting for space, 535 * wakeup/selwakeup/signal. If data 536 * are ready to send, let tcp_output 537 * decide between more output or persist. 538 */ 539 if (tp->snd_una == tp->snd_max) 540 tp->t_timer[TCPT_REXMT] = 0; 541 else if (tp->t_timer[TCPT_PERSIST] == 0) 542 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 543 544 /* 545 * There's room in so_snd, sowwakup will read() 546 * from the socket if we can 547 */ 548 /* if (so->so_snd.sb_flags & SB_NOTIFY) 549 * sowwakeup(so); 550 */ 551 /* 552 * This is called because sowwakeup might have 553 * put data into so_snd. Since we don't so sowwakeup, 554 * we don't need this.. XXX??? 555 */ 556 if (so->so_snd.sb_cc) 557 (void) tcp_output(tp); 558 559 return; 560 } 561 } else if (ti->ti_ack == tp->snd_una && 562 tcpfrag_list_empty(tp) && 563 ti->ti_len <= sbspace(&so->so_rcv)) { 564 /* 565 * this is a pure, in-sequence data packet 566 * with nothing on the reassembly queue and 567 * we have enough buffer space to take it. 568 */ 569 STAT(tcpstat.tcps_preddat++); 570 tp->rcv_nxt += ti->ti_len; 571 STAT(tcpstat.tcps_rcvpack++); 572 STAT(tcpstat.tcps_rcvbyte += ti->ti_len); 573 /* 574 * Add data to socket buffer. 575 */ 576 if (so->so_emu) { 577 if (tcp_emu(so,m)) sbappend(so, m); 578 } else 579 sbappend(so, m); 580 581 /* 582 * XXX This is called when data arrives. Later, check 583 * if we can actually write() to the socket 584 * XXX Need to check? It's be NON_BLOCKING 585 */ 586 /* sorwakeup(so); */ 587 588 /* 589 * If this is a short packet, then ACK now - with Nagel 590 * congestion avoidance sender won't send more until 591 * he gets an ACK. 592 * 593 * It is better to not delay acks at all to maximize 594 * TCP throughput. See RFC 2581. 595 */ 596 tp->t_flags |= TF_ACKNOW; 597 tcp_output(tp); 598 return; 599 } 600 } /* header prediction */ 601 /* 602 * Calculate amount of space in receive window, 603 * and then do TCP input processing. 604 * Receive window is amount of space in rcv queue, 605 * but not less than advertised window. 606 */ 607 { int win; 608 win = sbspace(&so->so_rcv); 609 if (win < 0) 610 win = 0; 611 tp->rcv_wnd = max(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 612 } 613 614 switch (tp->t_state) { 615 616 /* 617 * If the state is LISTEN then ignore segment if it contains an RST. 618 * If the segment contains an ACK then it is bad and send a RST. 619 * If it does not contain a SYN then it is not interesting; drop it. 620 * Don't bother responding if the destination was a broadcast. 621 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 622 * tp->iss, and send a segment: 623 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 624 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 625 * Fill in remote peer address fields if not previously specified. 626 * Enter SYN_RECEIVED state, and process any other fields of this 627 * segment in this state. 628 */ 629 case TCPS_LISTEN: { 630 631 if (tiflags & TH_RST) 632 goto drop; 633 if (tiflags & TH_ACK) 634 goto dropwithreset; 635 if ((tiflags & TH_SYN) == 0) 636 goto drop; 637 638 /* 639 * This has way too many gotos... 640 * But a bit of spaghetti code never hurt anybody :) 641 */ 642 643 /* 644 * If this is destined for the control address, then flag to 645 * tcp_ctl once connected, otherwise connect 646 */ 647 if ((so->so_faddr_ip & 0xffffff00) == special_addr_ip) { 648 int lastbyte=so->so_faddr_ip & 0xff; 649 if (lastbyte!=CTL_ALIAS && lastbyte!=CTL_DNS) { 650 #if 0 651 if(lastbyte==CTL_CMD || lastbyte==CTL_EXEC) { 652 /* Command or exec adress */ 653 so->so_state |= SS_CTL; 654 } else 655 #endif 656 { 657 /* May be an add exec */ 658 for(ex_ptr = exec_list; ex_ptr; ex_ptr = ex_ptr->ex_next) { 659 if(ex_ptr->ex_fport == so->so_faddr_port && 660 lastbyte == ex_ptr->ex_addr) { 661 so->so_state |= SS_CTL; 662 break; 663 } 664 } 665 } 666 if(so->so_state & SS_CTL) goto cont_input; 667 } 668 /* CTL_ALIAS: Do nothing, tcp_fconnect will be called on it */ 669 } 670 671 if (so->so_emu & EMU_NOCONNECT) { 672 so->so_emu &= ~EMU_NOCONNECT; 673 goto cont_input; 674 } 675 676 if((tcp_fconnect(so) == -1) && (errno != EINPROGRESS) && 677 (errno != EWOULDBLOCK) && (errno != EAGAIN)) { 678 u_char code=ICMP_UNREACH_NET; 679 DEBUG_MISC((dfd," tcp fconnect errno = %d-%s\n", 680 errno,errno_str)); 681 if(errno == ECONNREFUSED) { 682 /* ACK the SYN, send RST to refuse the connection */ 683 tcp_respond(tp, ti, m, ti->ti_seq+1, (tcp_seq)0, 684 TH_RST|TH_ACK); 685 } else { 686 if(errno == EHOSTUNREACH) code=ICMP_UNREACH_HOST; 687 HTONL(ti->ti_seq); /* restore tcp header */ 688 HTONL(ti->ti_ack); 689 HTONS(ti->ti_win); 690 HTONS(ti->ti_urp); 691 m->m_data -= sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 692 m->m_len += sizeof(struct tcpiphdr)+off-sizeof(struct tcphdr); 693 *ip=save_ip; 694 icmp_error(m, ICMP_UNREACH,code, 0,errno_str); 695 } 696 tp = tcp_close(tp); 697 m_free(m); 698 } else { 699 /* 700 * Haven't connected yet, save the current mbuf 701 * and ti, and return 702 * XXX Some OS's don't tell us whether the connect() 703 * succeeded or not. So we must time it out. 704 */ 705 so->so_m = m; 706 so->so_ti = ti; 707 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 708 tp->t_state = TCPS_SYN_RECEIVED; 709 } 710 return; 711 712 cont_conn: 713 /* m==NULL 714 * Check if the connect succeeded 715 */ 716 if (so->so_state & SS_NOFDREF) { 717 tp = tcp_close(tp); 718 goto dropwithreset; 719 } 720 cont_input: 721 tcp_template(tp); 722 723 if (optp) 724 tcp_dooptions(tp, (u_char *)optp, optlen, ti); 725 /* , */ 726 /* &ts_present, &ts_val, &ts_ecr); */ 727 728 if (iss) 729 tp->iss = iss; 730 else 731 tp->iss = tcp_iss; 732 tcp_iss += TCP_ISSINCR/2; 733 tp->irs = ti->ti_seq; 734 tcp_sendseqinit(tp); 735 tcp_rcvseqinit(tp); 736 tp->t_flags |= TF_ACKNOW; 737 tp->t_state = TCPS_SYN_RECEIVED; 738 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP_INIT; 739 STAT(tcpstat.tcps_accepts++); 740 goto trimthenstep6; 741 } /* case TCPS_LISTEN */ 742 743 /* 744 * If the state is SYN_SENT: 745 * if seg contains an ACK, but not for our SYN, drop the input. 746 * if seg contains a RST, then drop the connection. 747 * if seg does not contain SYN, then drop it. 748 * Otherwise this is an acceptable SYN segment 749 * initialize tp->rcv_nxt and tp->irs 750 * if seg contains ack then advance tp->snd_una 751 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 752 * arrange for segment to be acked (eventually) 753 * continue processing rest of data/controls, beginning with URG 754 */ 755 case TCPS_SYN_SENT: 756 if ((tiflags & TH_ACK) && 757 (SEQ_LEQ(ti->ti_ack, tp->iss) || 758 SEQ_GT(ti->ti_ack, tp->snd_max))) 759 goto dropwithreset; 760 761 if (tiflags & TH_RST) { 762 if (tiflags & TH_ACK) 763 tp = tcp_drop(tp,0); /* XXX Check t_softerror! */ 764 goto drop; 765 } 766 767 if ((tiflags & TH_SYN) == 0) 768 goto drop; 769 if (tiflags & TH_ACK) { 770 tp->snd_una = ti->ti_ack; 771 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 772 tp->snd_nxt = tp->snd_una; 773 } 774 775 tp->t_timer[TCPT_REXMT] = 0; 776 tp->irs = ti->ti_seq; 777 tcp_rcvseqinit(tp); 778 tp->t_flags |= TF_ACKNOW; 779 if (tiflags & TH_ACK && SEQ_GT(tp->snd_una, tp->iss)) { 780 STAT(tcpstat.tcps_connects++); 781 soisfconnected(so); 782 tp->t_state = TCPS_ESTABLISHED; 783 784 /* Do window scaling on this connection? */ 785 /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 786 * (TF_RCVD_SCALE|TF_REQ_SCALE)) { 787 * tp->snd_scale = tp->requested_s_scale; 788 * tp->rcv_scale = tp->request_r_scale; 789 * } 790 */ 791 (void) tcp_reass(tp, (struct tcpiphdr *)0, 792 (struct mbuf *)0); 793 /* 794 * if we didn't have to retransmit the SYN, 795 * use its rtt as our initial srtt & rtt var. 796 */ 797 if (tp->t_rtt) 798 tcp_xmit_timer(tp, tp->t_rtt); 799 } else 800 tp->t_state = TCPS_SYN_RECEIVED; 801 802 trimthenstep6: 803 /* 804 * Advance ti->ti_seq to correspond to first data byte. 805 * If data, trim to stay within window, 806 * dropping FIN if necessary. 807 */ 808 ti->ti_seq++; 809 if (ti->ti_len > tp->rcv_wnd) { 810 todrop = ti->ti_len - tp->rcv_wnd; 811 m_adj(m, -todrop); 812 ti->ti_len = tp->rcv_wnd; 813 tiflags &= ~TH_FIN; 814 STAT(tcpstat.tcps_rcvpackafterwin++); 815 STAT(tcpstat.tcps_rcvbyteafterwin += todrop); 816 } 817 tp->snd_wl1 = ti->ti_seq - 1; 818 tp->rcv_up = ti->ti_seq; 819 goto step6; 820 } /* switch tp->t_state */ 821 /* 822 * States other than LISTEN or SYN_SENT. 823 * First check timestamp, if present. 824 * Then check that at least some bytes of segment are within 825 * receive window. If segment begins before rcv_nxt, 826 * drop leading data (and SYN); if nothing left, just ack. 827 * 828 * RFC 1323 PAWS: If we have a timestamp reply on this segment 829 * and it's less than ts_recent, drop it. 830 */ 831 /* if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent && 832 * TSTMP_LT(ts_val, tp->ts_recent)) { 833 * 834 */ /* Check to see if ts_recent is over 24 days old. */ 835 /* if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) { 836 */ /* 837 * * Invalidate ts_recent. If this segment updates 838 * * ts_recent, the age will be reset later and ts_recent 839 * * will get a valid value. If it does not, setting 840 * * ts_recent to zero will at least satisfy the 841 * * requirement that zero be placed in the timestamp 842 * * echo reply when ts_recent isn't valid. The 843 * * age isn't reset until we get a valid ts_recent 844 * * because we don't want out-of-order segments to be 845 * * dropped when ts_recent is old. 846 * */ 847 /* tp->ts_recent = 0; 848 * } else { 849 * tcpstat.tcps_rcvduppack++; 850 * tcpstat.tcps_rcvdupbyte += ti->ti_len; 851 * tcpstat.tcps_pawsdrop++; 852 * goto dropafterack; 853 * } 854 * } 855 */ 856 857 todrop = tp->rcv_nxt - ti->ti_seq; 858 if (todrop > 0) { 859 if (tiflags & TH_SYN) { 860 tiflags &= ~TH_SYN; 861 ti->ti_seq++; 862 if (ti->ti_urp > 1) 863 ti->ti_urp--; 864 else 865 tiflags &= ~TH_URG; 866 todrop--; 867 } 868 /* 869 * Following if statement from Stevens, vol. 2, p. 960. 870 */ 871 if (todrop > ti->ti_len 872 || (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) { 873 /* 874 * Any valid FIN must be to the left of the window. 875 * At this point the FIN must be a duplicate or out 876 * of sequence; drop it. 877 */ 878 tiflags &= ~TH_FIN; 879 880 /* 881 * Send an ACK to resynchronize and drop any data. 882 * But keep on processing for RST or ACK. 883 */ 884 tp->t_flags |= TF_ACKNOW; 885 todrop = ti->ti_len; 886 STAT(tcpstat.tcps_rcvduppack++); 887 STAT(tcpstat.tcps_rcvdupbyte += todrop); 888 } else { 889 STAT(tcpstat.tcps_rcvpartduppack++); 890 STAT(tcpstat.tcps_rcvpartdupbyte += todrop); 891 } 892 m_adj(m, todrop); 893 ti->ti_seq += todrop; 894 ti->ti_len -= todrop; 895 if (ti->ti_urp > todrop) 896 ti->ti_urp -= todrop; 897 else { 898 tiflags &= ~TH_URG; 899 ti->ti_urp = 0; 900 } 901 } 902 /* 903 * If new data are received on a connection after the 904 * user processes are gone, then RST the other end. 905 */ 906 if ((so->so_state & SS_NOFDREF) && 907 tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) { 908 tp = tcp_close(tp); 909 STAT(tcpstat.tcps_rcvafterclose++); 910 goto dropwithreset; 911 } 912 913 /* 914 * If segment ends after window, drop trailing data 915 * (and PUSH and FIN); if nothing left, just ACK. 916 */ 917 todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 918 if (todrop > 0) { 919 STAT(tcpstat.tcps_rcvpackafterwin++); 920 if (todrop >= ti->ti_len) { 921 STAT(tcpstat.tcps_rcvbyteafterwin += ti->ti_len); 922 /* 923 * If a new connection request is received 924 * while in TIME_WAIT, drop the old connection 925 * and start over if the sequence numbers 926 * are above the previous ones. 927 */ 928 if (tiflags & TH_SYN && 929 tp->t_state == TCPS_TIME_WAIT && 930 SEQ_GT(ti->ti_seq, tp->rcv_nxt)) { 931 iss = tp->rcv_nxt + TCP_ISSINCR; 932 tp = tcp_close(tp); 933 goto findso; 934 } 935 /* 936 * If window is closed can only take segments at 937 * window edge, and have to drop data and PUSH from 938 * incoming segments. Continue processing, but 939 * remember to ack. Otherwise, drop segment 940 * and ack. 941 */ 942 if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) { 943 tp->t_flags |= TF_ACKNOW; 944 STAT(tcpstat.tcps_rcvwinprobe++); 945 } else 946 goto dropafterack; 947 } else 948 STAT(tcpstat.tcps_rcvbyteafterwin += todrop); 949 m_adj(m, -todrop); 950 ti->ti_len -= todrop; 951 tiflags &= ~(TH_PUSH|TH_FIN); 952 } 953 954 /* 955 * If last ACK falls within this segment's sequence numbers, 956 * record its timestamp. 957 */ 958 /* if (ts_present && SEQ_LEQ(ti->ti_seq, tp->last_ack_sent) && 959 * SEQ_LT(tp->last_ack_sent, ti->ti_seq + ti->ti_len + 960 * ((tiflags & (TH_SYN|TH_FIN)) != 0))) { 961 * tp->ts_recent_age = tcp_now; 962 * tp->ts_recent = ts_val; 963 * } 964 */ 965 966 /* 967 * If the RST bit is set examine the state: 968 * SYN_RECEIVED STATE: 969 * If passive open, return to LISTEN state. 970 * If active open, inform user that connection was refused. 971 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 972 * Inform user that connection was reset, and close tcb. 973 * CLOSING, LAST_ACK, TIME_WAIT STATES 974 * Close the tcb. 975 */ 976 if (tiflags&TH_RST) switch (tp->t_state) { 977 978 case TCPS_SYN_RECEIVED: 979 /* so->so_error = ECONNREFUSED; */ 980 goto close; 981 982 case TCPS_ESTABLISHED: 983 case TCPS_FIN_WAIT_1: 984 case TCPS_FIN_WAIT_2: 985 case TCPS_CLOSE_WAIT: 986 /* so->so_error = ECONNRESET; */ 987 close: 988 tp->t_state = TCPS_CLOSED; 989 STAT(tcpstat.tcps_drops++); 990 tp = tcp_close(tp); 991 goto drop; 992 993 case TCPS_CLOSING: 994 case TCPS_LAST_ACK: 995 case TCPS_TIME_WAIT: 996 tp = tcp_close(tp); 997 goto drop; 998 } 999 1000 /* 1001 * If a SYN is in the window, then this is an 1002 * error and we send an RST and drop the connection. 1003 */ 1004 if (tiflags & TH_SYN) { 1005 tp = tcp_drop(tp,0); 1006 goto dropwithreset; 1007 } 1008 1009 /* 1010 * If the ACK bit is off we drop the segment and return. 1011 */ 1012 if ((tiflags & TH_ACK) == 0) goto drop; 1013 1014 /* 1015 * Ack processing. 1016 */ 1017 switch (tp->t_state) { 1018 /* 1019 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 1020 * ESTABLISHED state and continue processing, otherwise 1021 * send an RST. una<=ack<=max 1022 */ 1023 case TCPS_SYN_RECEIVED: 1024 1025 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 1026 SEQ_GT(ti->ti_ack, tp->snd_max)) 1027 goto dropwithreset; 1028 STAT(tcpstat.tcps_connects++); 1029 tp->t_state = TCPS_ESTABLISHED; 1030 /* 1031 * The sent SYN is ack'ed with our sequence number +1 1032 * The first data byte already in the buffer will get 1033 * lost if no correction is made. This is only needed for 1034 * SS_CTL since the buffer is empty otherwise. 1035 * tp->snd_una++; or: 1036 */ 1037 tp->snd_una=ti->ti_ack; 1038 if (so->so_state & SS_CTL) { 1039 /* So tcp_ctl reports the right state */ 1040 ret = tcp_ctl(so); 1041 if (ret == 1) { 1042 soisfconnected(so); 1043 so->so_state &= ~SS_CTL; /* success XXX */ 1044 } else if (ret == 2) { 1045 so->so_state = SS_NOFDREF; /* CTL_CMD */ 1046 } else { 1047 needoutput = 1; 1048 tp->t_state = TCPS_FIN_WAIT_1; 1049 } 1050 } else { 1051 soisfconnected(so); 1052 } 1053 1054 /* Do window scaling? */ 1055 /* if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) == 1056 * (TF_RCVD_SCALE|TF_REQ_SCALE)) { 1057 * tp->snd_scale = tp->requested_s_scale; 1058 * tp->rcv_scale = tp->request_r_scale; 1059 * } 1060 */ 1061 (void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)0); 1062 tp->snd_wl1 = ti->ti_seq - 1; 1063 /* Avoid ack processing; snd_una==ti_ack => dup ack */ 1064 goto synrx_to_est; 1065 /* fall into ... */ 1066 1067 /* 1068 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 1069 * ACKs. If the ack is in the range 1070 * tp->snd_una < ti->ti_ack <= tp->snd_max 1071 * then advance tp->snd_una to ti->ti_ack and drop 1072 * data from the retransmission queue. If this ACK reflects 1073 * more up to date window information we update our window information. 1074 */ 1075 case TCPS_ESTABLISHED: 1076 case TCPS_FIN_WAIT_1: 1077 case TCPS_FIN_WAIT_2: 1078 case TCPS_CLOSE_WAIT: 1079 case TCPS_CLOSING: 1080 case TCPS_LAST_ACK: 1081 case TCPS_TIME_WAIT: 1082 1083 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) { 1084 if (ti->ti_len == 0 && tiwin == tp->snd_wnd) { 1085 STAT(tcpstat.tcps_rcvdupack++); 1086 DEBUG_MISC((dfd," dup ack m = %lx so = %lx \n", 1087 (long )m, (long )so)); 1088 /* 1089 * If we have outstanding data (other than 1090 * a window probe), this is a completely 1091 * duplicate ack (ie, window info didn't 1092 * change), the ack is the biggest we've 1093 * seen and we've seen exactly our rexmt 1094 * threshold of them, assume a packet 1095 * has been dropped and retransmit it. 1096 * Kludge snd_nxt & the congestion 1097 * window so we send only this one 1098 * packet. 1099 * 1100 * We know we're losing at the current 1101 * window size so do congestion avoidance 1102 * (set ssthresh to half the current window 1103 * and pull our congestion window back to 1104 * the new ssthresh). 1105 * 1106 * Dup acks mean that packets have left the 1107 * network (they're now cached at the receiver) 1108 * so bump cwnd by the amount in the receiver 1109 * to keep a constant cwnd packets in the 1110 * network. 1111 */ 1112 if (tp->t_timer[TCPT_REXMT] == 0 || 1113 ti->ti_ack != tp->snd_una) 1114 tp->t_dupacks = 0; 1115 else if (++tp->t_dupacks == TCPREXMTTHRESH) { 1116 tcp_seq onxt = tp->snd_nxt; 1117 u_int win = 1118 min(tp->snd_wnd, tp->snd_cwnd) / 2 / 1119 tp->t_maxseg; 1120 1121 if (win < 2) 1122 win = 2; 1123 tp->snd_ssthresh = win * tp->t_maxseg; 1124 tp->t_timer[TCPT_REXMT] = 0; 1125 tp->t_rtt = 0; 1126 tp->snd_nxt = ti->ti_ack; 1127 tp->snd_cwnd = tp->t_maxseg; 1128 (void) tcp_output(tp); 1129 tp->snd_cwnd = tp->snd_ssthresh + 1130 tp->t_maxseg * tp->t_dupacks; 1131 if (SEQ_GT(onxt, tp->snd_nxt)) 1132 tp->snd_nxt = onxt; 1133 goto drop; 1134 } else if (tp->t_dupacks > TCPREXMTTHRESH) { 1135 tp->snd_cwnd += tp->t_maxseg; 1136 (void) tcp_output(tp); 1137 goto drop; 1138 } 1139 } else 1140 tp->t_dupacks = 0; 1141 break; 1142 } 1143 synrx_to_est: 1144 /* 1145 * If the congestion window was inflated to account 1146 * for the other side's cached packets, retract it. 1147 */ 1148 if (tp->t_dupacks > TCPREXMTTHRESH && 1149 tp->snd_cwnd > tp->snd_ssthresh) 1150 tp->snd_cwnd = tp->snd_ssthresh; 1151 tp->t_dupacks = 0; 1152 if (SEQ_GT(ti->ti_ack, tp->snd_max)) { 1153 STAT(tcpstat.tcps_rcvacktoomuch++); 1154 goto dropafterack; 1155 } 1156 acked = ti->ti_ack - tp->snd_una; 1157 STAT(tcpstat.tcps_rcvackpack++); 1158 STAT(tcpstat.tcps_rcvackbyte += acked); 1159 1160 /* 1161 * If we have a timestamp reply, update smoothed 1162 * round trip time. If no timestamp is present but 1163 * transmit timer is running and timed sequence 1164 * number was acked, update smoothed round trip time. 1165 * Since we now have an rtt measurement, cancel the 1166 * timer backoff (cf., Phil Karn's retransmit alg.). 1167 * Recompute the initial retransmit timer. 1168 */ 1169 /* if (ts_present) 1170 * tcp_xmit_timer(tp, tcp_now-ts_ecr+1); 1171 * else 1172 */ 1173 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) 1174 tcp_xmit_timer(tp,tp->t_rtt); 1175 1176 /* 1177 * If all outstanding data is acked, stop retransmit 1178 * timer and remember to restart (more output or persist). 1179 * If there is more data to be acked, restart retransmit 1180 * timer, using current (possibly backed-off) value. 1181 */ 1182 if (ti->ti_ack == tp->snd_max) { 1183 tp->t_timer[TCPT_REXMT] = 0; 1184 needoutput = 1; 1185 } else if (tp->t_timer[TCPT_PERSIST] == 0) 1186 tp->t_timer[TCPT_REXMT] = tp->t_rxtcur; 1187 /* 1188 * When new data is acked, open the congestion window. 1189 * If the window gives us less than ssthresh packets 1190 * in flight, open exponentially (maxseg per packet). 1191 * Otherwise open linearly: maxseg per window 1192 * (maxseg^2 / cwnd per packet). 1193 */ 1194 { 1195 register u_int cw = tp->snd_cwnd; 1196 register u_int incr = tp->t_maxseg; 1197 1198 if (cw > tp->snd_ssthresh) 1199 incr = incr * incr / cw; 1200 tp->snd_cwnd = min(cw + incr, TCP_MAXWIN<<tp->snd_scale); 1201 } 1202 if (acked > so->so_snd.sb_cc) { 1203 tp->snd_wnd -= so->so_snd.sb_cc; 1204 sbdrop(&so->so_snd, (int )so->so_snd.sb_cc); 1205 ourfinisacked = 1; 1206 } else { 1207 sbdrop(&so->so_snd, acked); 1208 tp->snd_wnd -= acked; 1209 ourfinisacked = 0; 1210 } 1211 /* 1212 * XXX sowwakup is called when data is acked and there's room for 1213 * for more data... it should read() the socket 1214 */ 1215 /* if (so->so_snd.sb_flags & SB_NOTIFY) 1216 * sowwakeup(so); 1217 */ 1218 tp->snd_una = ti->ti_ack; 1219 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 1220 tp->snd_nxt = tp->snd_una; 1221 1222 switch (tp->t_state) { 1223 1224 /* 1225 * In FIN_WAIT_1 STATE in addition to the processing 1226 * for the ESTABLISHED state if our FIN is now acknowledged 1227 * then enter FIN_WAIT_2. 1228 */ 1229 case TCPS_FIN_WAIT_1: 1230 if (ourfinisacked) { 1231 /* 1232 * If we can't receive any more 1233 * data, then closing user can proceed. 1234 * Starting the timer is contrary to the 1235 * specification, but if we don't get a FIN 1236 * we'll hang forever. 1237 */ 1238 if (so->so_state & SS_FCANTRCVMORE) { 1239 soisfdisconnected(so); 1240 tp->t_timer[TCPT_2MSL] = TCP_MAXIDLE; 1241 } 1242 tp->t_state = TCPS_FIN_WAIT_2; 1243 } 1244 break; 1245 1246 /* 1247 * In CLOSING STATE in addition to the processing for 1248 * the ESTABLISHED state if the ACK acknowledges our FIN 1249 * then enter the TIME-WAIT state, otherwise ignore 1250 * the segment. 1251 */ 1252 case TCPS_CLOSING: 1253 if (ourfinisacked) { 1254 tp->t_state = TCPS_TIME_WAIT; 1255 tcp_canceltimers(tp); 1256 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1257 soisfdisconnected(so); 1258 } 1259 break; 1260 1261 /* 1262 * In LAST_ACK, we may still be waiting for data to drain 1263 * and/or to be acked, as well as for the ack of our FIN. 1264 * If our FIN is now acknowledged, delete the TCB, 1265 * enter the closed state and return. 1266 */ 1267 case TCPS_LAST_ACK: 1268 if (ourfinisacked) { 1269 tp = tcp_close(tp); 1270 goto drop; 1271 } 1272 break; 1273 1274 /* 1275 * In TIME_WAIT state the only thing that should arrive 1276 * is a retransmission of the remote FIN. Acknowledge 1277 * it and restart the finack timer. 1278 */ 1279 case TCPS_TIME_WAIT: 1280 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1281 goto dropafterack; 1282 } 1283 } /* switch(tp->t_state) */ 1284 1285 step6: 1286 /* 1287 * Update window information. 1288 * Don't look at window if no ACK: TAC's send garbage on first SYN. 1289 */ 1290 if ((tiflags & TH_ACK) && 1291 (SEQ_LT(tp->snd_wl1, ti->ti_seq) || 1292 (tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 1293 (tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd))))) { 1294 /* keep track of pure window updates */ 1295 if (ti->ti_len == 0 && 1296 tp->snd_wl2 == ti->ti_ack && tiwin > tp->snd_wnd) 1297 STAT(tcpstat.tcps_rcvwinupd++); 1298 tp->snd_wnd = tiwin; 1299 tp->snd_wl1 = ti->ti_seq; 1300 tp->snd_wl2 = ti->ti_ack; 1301 if (tp->snd_wnd > tp->max_sndwnd) 1302 tp->max_sndwnd = tp->snd_wnd; 1303 needoutput = 1; 1304 } 1305 1306 /* 1307 * Process segments with URG. 1308 */ 1309 if ((tiflags & TH_URG) && ti->ti_urp && 1310 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1311 /* 1312 * This is a kludge, but if we receive and accept 1313 * random urgent pointers, we'll crash in 1314 * soreceive. It's hard to imagine someone 1315 * actually wanting to send this much urgent data. 1316 */ 1317 if (ti->ti_urp + so->so_rcv.sb_cc > so->so_rcv.sb_datalen) { 1318 ti->ti_urp = 0; 1319 tiflags &= ~TH_URG; 1320 goto dodata; 1321 } 1322 /* 1323 * If this segment advances the known urgent pointer, 1324 * then mark the data stream. This should not happen 1325 * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 1326 * a FIN has been received from the remote side. 1327 * In these states we ignore the URG. 1328 * 1329 * According to RFC961 (Assigned Protocols), 1330 * the urgent pointer points to the last octet 1331 * of urgent data. We continue, however, 1332 * to consider it to indicate the first octet 1333 * of data past the urgent section as the original 1334 * spec states (in one of two places). 1335 */ 1336 if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 1337 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1338 so->so_urgc = so->so_rcv.sb_cc + 1339 (tp->rcv_up - tp->rcv_nxt); /* -1; */ 1340 tp->rcv_up = ti->ti_seq + ti->ti_urp; 1341 1342 } 1343 } else 1344 /* 1345 * If no out of band data is expected, 1346 * pull receive urgent pointer along 1347 * with the receive window. 1348 */ 1349 if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 1350 tp->rcv_up = tp->rcv_nxt; 1351 dodata: 1352 1353 /* 1354 * Process the segment text, merging it into the TCP sequencing queue, 1355 * and arranging for acknowledgment of receipt if necessary. 1356 * This process logically involves adjusting tp->rcv_wnd as data 1357 * is presented to the user (this happens in tcp_usrreq.c, 1358 * case PRU_RCVD). If a FIN has already been received on this 1359 * connection then we just ignore the text. 1360 */ 1361 if ((ti->ti_len || (tiflags&TH_FIN)) && 1362 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1363 TCP_REASS(tp, ti, m, so, tiflags); 1364 /* 1365 * Note the amount of data that peer has sent into 1366 * our window, in order to estimate the sender's 1367 * buffer size. 1368 */ 1369 len = so->so_rcv.sb_datalen - (tp->rcv_adv - tp->rcv_nxt); 1370 } else { 1371 m_free(m); 1372 tiflags &= ~TH_FIN; 1373 } 1374 1375 /* 1376 * If FIN is received ACK the FIN and let the user know 1377 * that the connection is closing. 1378 */ 1379 if (tiflags & TH_FIN) { 1380 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 1381 /* 1382 * If we receive a FIN we can't send more data, 1383 * set it SS_FDRAIN 1384 * Shutdown the socket if there is no rx data in the 1385 * buffer. 1386 * soread() is called on completion of shutdown() and 1387 * will got to TCPS_LAST_ACK, and use tcp_output() 1388 * to send the FIN. 1389 */ 1390 /* sofcantrcvmore(so); */ 1391 sofwdrain(so); 1392 1393 tp->t_flags |= TF_ACKNOW; 1394 tp->rcv_nxt++; 1395 } 1396 switch (tp->t_state) { 1397 1398 /* 1399 * In SYN_RECEIVED and ESTABLISHED STATES 1400 * enter the CLOSE_WAIT state. 1401 */ 1402 case TCPS_SYN_RECEIVED: 1403 case TCPS_ESTABLISHED: 1404 if(so->so_emu == EMU_CTL) /* no shutdown on socket */ 1405 tp->t_state = TCPS_LAST_ACK; 1406 else 1407 tp->t_state = TCPS_CLOSE_WAIT; 1408 break; 1409 1410 /* 1411 * If still in FIN_WAIT_1 STATE FIN has not been acked so 1412 * enter the CLOSING state. 1413 */ 1414 case TCPS_FIN_WAIT_1: 1415 tp->t_state = TCPS_CLOSING; 1416 break; 1417 1418 /* 1419 * In FIN_WAIT_2 state enter the TIME_WAIT state, 1420 * starting the time-wait timer, turning off the other 1421 * standard timers. 1422 */ 1423 case TCPS_FIN_WAIT_2: 1424 tp->t_state = TCPS_TIME_WAIT; 1425 tcp_canceltimers(tp); 1426 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1427 soisfdisconnected(so); 1428 break; 1429 1430 /* 1431 * In TIME_WAIT state restart the 2 MSL time_wait timer. 1432 */ 1433 case TCPS_TIME_WAIT: 1434 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 1435 break; 1436 } 1437 } 1438 1439 /* 1440 * If this is a small packet, then ACK now - with Nagel 1441 * congestion avoidance sender won't send more until 1442 * he gets an ACK. 1443 * 1444 * See above. 1445 */ 1446 /* if (ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg) { 1447 */ 1448 /* if ((ti->ti_len && (unsigned)ti->ti_len < tp->t_maxseg && 1449 * (so->so_iptos & IPTOS_LOWDELAY) == 0) || 1450 * ((so->so_iptos & IPTOS_LOWDELAY) && 1451 * ((struct tcpiphdr_2 *)ti)->first_char == (char)27)) { 1452 */ 1453 if (ti->ti_len && (unsigned)ti->ti_len <= 5 && 1454 ((struct tcpiphdr_2 *)ti)->first_char == (char)27) { 1455 tp->t_flags |= TF_ACKNOW; 1456 } 1457 1458 /* 1459 * Return any desired output. 1460 */ 1461 if (needoutput || (tp->t_flags & TF_ACKNOW)) { 1462 (void) tcp_output(tp); 1463 } 1464 return; 1465 1466 dropafterack: 1467 /* 1468 * Generate an ACK dropping incoming segment if it occupies 1469 * sequence space, where the ACK reflects our state. 1470 */ 1471 if (tiflags & TH_RST) 1472 goto drop; 1473 m_freem(m); 1474 tp->t_flags |= TF_ACKNOW; 1475 (void) tcp_output(tp); 1476 return; 1477 1478 dropwithreset: 1479 /* reuses m if m!=NULL, m_free() unnecessary */ 1480 if (tiflags & TH_ACK) 1481 tcp_respond(tp, ti, m, (tcp_seq)0, ti->ti_ack, TH_RST); 1482 else { 1483 if (tiflags & TH_SYN) ti->ti_len++; 1484 tcp_respond(tp, ti, m, ti->ti_seq+ti->ti_len, (tcp_seq)0, 1485 TH_RST|TH_ACK); 1486 } 1487 1488 return; 1489 1490 drop: 1491 /* 1492 * Drop space held by incoming segment and return. 1493 */ 1494 m_free(m); 1495 1496 return; 1497 } 1498 1499 /* , ts_present, ts_val, ts_ecr) */ 1500 /* int *ts_present; 1501 * u_int32_t *ts_val, *ts_ecr; 1502 */ 1503 static void 1504 tcp_dooptions(struct tcpcb *tp, u_char *cp, int cnt, struct tcpiphdr *ti) 1505 { 1506 u_int16_t mss; 1507 int opt, optlen; 1508 1509 DEBUG_CALL("tcp_dooptions"); 1510 DEBUG_ARGS((dfd," tp = %lx cnt=%i \n", (long )tp, cnt)); 1511 1512 for (; cnt > 0; cnt -= optlen, cp += optlen) { 1513 opt = cp[0]; 1514 if (opt == TCPOPT_EOL) 1515 break; 1516 if (opt == TCPOPT_NOP) 1517 optlen = 1; 1518 else { 1519 optlen = cp[1]; 1520 if (optlen <= 0) 1521 break; 1522 } 1523 switch (opt) { 1524 1525 default: 1526 continue; 1527 1528 case TCPOPT_MAXSEG: 1529 if (optlen != TCPOLEN_MAXSEG) 1530 continue; 1531 if (!(ti->ti_flags & TH_SYN)) 1532 continue; 1533 memcpy((char *) &mss, (char *) cp + 2, sizeof(mss)); 1534 NTOHS(mss); 1535 (void) tcp_mss(tp, mss); /* sets t_maxseg */ 1536 break; 1537 1538 /* case TCPOPT_WINDOW: 1539 * if (optlen != TCPOLEN_WINDOW) 1540 * continue; 1541 * if (!(ti->ti_flags & TH_SYN)) 1542 * continue; 1543 * tp->t_flags |= TF_RCVD_SCALE; 1544 * tp->requested_s_scale = min(cp[2], TCP_MAX_WINSHIFT); 1545 * break; 1546 */ 1547 /* case TCPOPT_TIMESTAMP: 1548 * if (optlen != TCPOLEN_TIMESTAMP) 1549 * continue; 1550 * *ts_present = 1; 1551 * memcpy((char *) ts_val, (char *)cp + 2, sizeof(*ts_val)); 1552 * NTOHL(*ts_val); 1553 * memcpy((char *) ts_ecr, (char *)cp + 6, sizeof(*ts_ecr)); 1554 * NTOHL(*ts_ecr); 1555 * 1556 */ /* 1557 * * A timestamp received in a SYN makes 1558 * * it ok to send timestamp requests and replies. 1559 * */ 1560 /* if (ti->ti_flags & TH_SYN) { 1561 * tp->t_flags |= TF_RCVD_TSTMP; 1562 * tp->ts_recent = *ts_val; 1563 * tp->ts_recent_age = tcp_now; 1564 * } 1565 */ break; 1566 } 1567 } 1568 } 1569 1570 1571 /* 1572 * Pull out of band byte out of a segment so 1573 * it doesn't appear in the user's data queue. 1574 * It is still reflected in the segment length for 1575 * sequencing purposes. 1576 */ 1577 1578 #ifdef notdef 1579 1580 void 1581 tcp_pulloutofband(so, ti, m) 1582 struct socket *so; 1583 struct tcpiphdr *ti; 1584 register struct mbuf *m; 1585 { 1586 int cnt = ti->ti_urp - 1; 1587 1588 while (cnt >= 0) { 1589 if (m->m_len > cnt) { 1590 char *cp = mtod(m, caddr_t) + cnt; 1591 struct tcpcb *tp = sototcpcb(so); 1592 1593 tp->t_iobc = *cp; 1594 tp->t_oobflags |= TCPOOB_HAVEDATA; 1595 memcpy(sp, cp+1, (unsigned)(m->m_len - cnt - 1)); 1596 m->m_len--; 1597 return; 1598 } 1599 cnt -= m->m_len; 1600 m = m->m_next; /* XXX WRONG! Fix it! */ 1601 if (m == 0) 1602 break; 1603 } 1604 panic("tcp_pulloutofband"); 1605 } 1606 1607 #endif /* notdef */ 1608 1609 /* 1610 * Collect new round-trip time estimate 1611 * and update averages and current timeout. 1612 */ 1613 1614 static void 1615 tcp_xmit_timer(register struct tcpcb *tp, int rtt) 1616 { 1617 register short delta; 1618 1619 DEBUG_CALL("tcp_xmit_timer"); 1620 DEBUG_ARG("tp = %lx", (long)tp); 1621 DEBUG_ARG("rtt = %d", rtt); 1622 1623 STAT(tcpstat.tcps_rttupdated++); 1624 if (tp->t_srtt != 0) { 1625 /* 1626 * srtt is stored as fixed point with 3 bits after the 1627 * binary point (i.e., scaled by 8). The following magic 1628 * is equivalent to the smoothing algorithm in rfc793 with 1629 * an alpha of .875 (srtt = rtt/8 + srtt*7/8 in fixed 1630 * point). Adjust rtt to origin 0. 1631 */ 1632 delta = rtt - 1 - (tp->t_srtt >> TCP_RTT_SHIFT); 1633 if ((tp->t_srtt += delta) <= 0) 1634 tp->t_srtt = 1; 1635 /* 1636 * We accumulate a smoothed rtt variance (actually, a 1637 * smoothed mean difference), then set the retransmit 1638 * timer to smoothed rtt + 4 times the smoothed variance. 1639 * rttvar is stored as fixed point with 2 bits after the 1640 * binary point (scaled by 4). The following is 1641 * equivalent to rfc793 smoothing with an alpha of .75 1642 * (rttvar = rttvar*3/4 + |delta| / 4). This replaces 1643 * rfc793's wired-in beta. 1644 */ 1645 if (delta < 0) 1646 delta = -delta; 1647 delta -= (tp->t_rttvar >> TCP_RTTVAR_SHIFT); 1648 if ((tp->t_rttvar += delta) <= 0) 1649 tp->t_rttvar = 1; 1650 } else { 1651 /* 1652 * No rtt measurement yet - use the unsmoothed rtt. 1653 * Set the variance to half the rtt (so our first 1654 * retransmit happens at 3*rtt). 1655 */ 1656 tp->t_srtt = rtt << TCP_RTT_SHIFT; 1657 tp->t_rttvar = rtt << (TCP_RTTVAR_SHIFT - 1); 1658 } 1659 tp->t_rtt = 0; 1660 tp->t_rxtshift = 0; 1661 1662 /* 1663 * the retransmit should happen at rtt + 4 * rttvar. 1664 * Because of the way we do the smoothing, srtt and rttvar 1665 * will each average +1/2 tick of bias. When we compute 1666 * the retransmit timer, we want 1/2 tick of rounding and 1667 * 1 extra tick because of +-1/2 tick uncertainty in the 1668 * firing of the timer. The bias will give us exactly the 1669 * 1.5 tick we need. But, because the bias is 1670 * statistical, we have to test that we don't drop below 1671 * the minimum feasible timer (which is 2 ticks). 1672 */ 1673 TCPT_RANGESET(tp->t_rxtcur, TCP_REXMTVAL(tp), 1674 (short)tp->t_rttmin, TCPTV_REXMTMAX); /* XXX */ 1675 1676 /* 1677 * We received an ack for a packet that wasn't retransmitted; 1678 * it is probably safe to discard any error indications we've 1679 * received recently. This isn't quite right, but close enough 1680 * for now (a route might have failed after we sent a segment, 1681 * and the return path might not be symmetrical). 1682 */ 1683 tp->t_softerror = 0; 1684 } 1685 1686 /* 1687 * Determine a reasonable value for maxseg size. 1688 * If the route is known, check route for mtu. 1689 * If none, use an mss that can be handled on the outgoing 1690 * interface without forcing IP to fragment; if bigger than 1691 * an mbuf cluster (MCLBYTES), round down to nearest multiple of MCLBYTES 1692 * to utilize large mbufs. If no route is found, route has no mtu, 1693 * or the destination isn't local, use a default, hopefully conservative 1694 * size (usually 512 or the default IP max size, but no more than the mtu 1695 * of the interface), as we can't discover anything about intervening 1696 * gateways or networks. We also initialize the congestion/slow start 1697 * window to be a single segment if the destination isn't local. 1698 * While looking at the routing entry, we also initialize other path-dependent 1699 * parameters from pre-set or cached values in the routing entry. 1700 */ 1701 1702 int 1703 tcp_mss(struct tcpcb *tp, u_int offer) 1704 { 1705 struct socket *so = tp->t_socket; 1706 int mss; 1707 1708 DEBUG_CALL("tcp_mss"); 1709 DEBUG_ARG("tp = %lx", (long)tp); 1710 DEBUG_ARG("offer = %d", offer); 1711 1712 mss = min(IF_MTU, IF_MRU) - sizeof(struct tcpiphdr); 1713 if (offer) 1714 mss = min(mss, offer); 1715 mss = max(mss, 32); 1716 if (mss < tp->t_maxseg || offer != 0) 1717 tp->t_maxseg = mss; 1718 1719 tp->snd_cwnd = mss; 1720 1721 sbreserve(&so->so_snd, TCP_SNDSPACE + ((TCP_SNDSPACE % mss) ? 1722 (mss - (TCP_SNDSPACE % mss)) : 1723 0)); 1724 sbreserve(&so->so_rcv, TCP_RCVSPACE + ((TCP_RCVSPACE % mss) ? 1725 (mss - (TCP_RCVSPACE % mss)) : 1726 0)); 1727 1728 DEBUG_MISC((dfd, " returning mss = %d\n", mss)); 1729 1730 return mss; 1731 } 1732
