1 /* tcp_input.c 1.46 82/01/07 */ 2 3 #include "../h/param.h" 4 #include "../h/systm.h" 5 #include "../h/mbuf.h" 6 #include "../h/protosw.h" 7 #include "../h/socket.h" 8 #include "../h/socketvar.h" 9 #include "../net/in.h" 10 #include "../net/in_pcb.h" 11 #include "../net/in_systm.h" 12 #include "../net/if.h" 13 #include "../net/ip.h" 14 #include "../net/ip_var.h" 15 #include "../net/tcp.h" 16 #include "../net/tcp_fsm.h" 17 #include "../net/tcp_seq.h" 18 #include "../net/tcp_timer.h" 19 #include "../net/tcp_var.h" 20 #include "../net/tcpip.h" 21 #include "../net/tcp_debug.h" 22 #include "../errno.h" 23 24 int tcpprintfs = 0; 25 int tcpcksum = 1; 26 struct sockaddr_in tcp_in = { AF_INET }; 27 struct tcpiphdr tcp_saveti; 28 29 struct tcpcb *tcp_newtcpcb(); 30 /* 31 * TCP input routine, follows pages 65-76 of the 32 * protocol specification dated September, 1981 very closely. 33 */ 34 tcp_input(m0) 35 struct mbuf *m0; 36 { 37 register struct tcpiphdr *ti; 38 struct inpcb *inp; 39 register struct mbuf *m; 40 int len, tlen, off; 41 register struct tcpcb *tp; 42 register int tiflags; 43 struct socket *so; 44 int todrop, acked; 45 short ostate; 46 47 COUNT(TCP_INPUT); 48 /* 49 * Get IP and TCP header together in first mbuf. 50 * Note: IP leaves IP header in first mbuf. 51 */ 52 m = m0; 53 ti = mtod(m, struct tcpiphdr *); 54 if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 55 ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 56 if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 57 if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 58 tcpstat.tcps_hdrops++; 59 return; 60 } 61 ti = mtod(m, struct tcpiphdr *); 62 } 63 64 /* 65 * Checksum extended TCP header and data. 66 */ 67 tlen = ((struct ip *)ti)->ip_len; 68 len = sizeof (struct ip) + tlen; 69 if (tcpcksum) { 70 ti->ti_next = ti->ti_prev = 0; 71 ti->ti_x1 = 0; 72 ti->ti_len = (u_short)tlen; 73 #if vax 74 ti->ti_len = htons(ti->ti_len); 75 #endif 76 if (ti->ti_sum = in_cksum(m, len)) { 77 tcpstat.tcps_badsum++; 78 printf("tcp cksum %x\n", ti->ti_sum); 79 goto drop; 80 } 81 } 82 83 /* 84 * Check that TCP offset makes sense, 85 * process TCP options and adjust length. 86 */ 87 off = ti->ti_off << 2; 88 if (off < sizeof (struct tcphdr) || off > tlen) { 89 tcpstat.tcps_badoff++; 90 goto drop; 91 } 92 ti->ti_len = tlen - off; 93 #if 0 94 if (off > sizeof (struct tcphdr)) 95 tcp_options(ti); 96 #endif 97 tiflags = ti->ti_flags; 98 99 #if vax 100 /* 101 * Convert TCP protocol specific fields to host format. 102 */ 103 ti->ti_seq = ntohl(ti->ti_seq); 104 ti->ti_ack = ntohl(ti->ti_ack); 105 ti->ti_win = ntohs(ti->ti_win); 106 ti->ti_urp = ntohs(ti->ti_urp); 107 #endif 108 109 /* 110 * Locate pcb for segment. 111 */ 112 inp = in_pcblookup 113 (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport); 114 115 /* 116 * If the state is CLOSED (i.e., TCB does not exist) then 117 * all data in the incoming segment is discarded. 118 */ 119 if (inp == 0) 120 goto dropwithreset; 121 tp = intotcpcb(inp); 122 if (tp == 0) 123 goto dropwithreset; 124 so = inp->inp_socket; 125 if (so->so_options & SO_DEBUG) { 126 ostate = tp->t_state; 127 tcp_saveti = *ti; 128 } 129 130 /* 131 * Segment received on connection. 132 * Reset idle time and keep-alive timer. 133 */ 134 tp->t_idle = 0; 135 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 136 137 /* 138 * Calculate amount of space in receive window, 139 * and then do TCP input processing. 140 */ 141 tp->rcv_wnd = sbspace(&so->so_rcv); 142 if (tp->rcv_wnd < 0) 143 tp->rcv_wnd = 0; 144 145 switch (tp->t_state) { 146 147 /* 148 * If the state is LISTEN then ignore segment if it contains an RST. 149 * If the segment contains an ACK then it is bad and send a RST. 150 * If it does not contain a SYN then it is not interesting; drop it. 151 * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 152 * tp->iss, and send a segment: 153 * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 154 * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 155 * Fill in remote peer address fields if not previously specified. 156 * Enter SYN_RECEIVED state, and process any other fields of this 157 * segment in this state. 158 */ 159 case TCPS_LISTEN: 160 if (tiflags & TH_RST) 161 goto drop; 162 if (tiflags & TH_ACK) 163 goto dropwithreset; 164 if ((tiflags & TH_SYN) == 0) 165 goto drop; 166 tcp_in.sin_addr = ti->ti_src; 167 tcp_in.sin_port = ti->ti_sport; 168 if (in_pcbconnect(inp, (struct sockaddr *)&tcp_in)) 169 goto drop; 170 tp->t_template = tcp_template(tp); 171 if (tp->t_template == 0) { 172 in_pcbdisconnect(inp); 173 goto drop; 174 } 175 tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 176 tp->irs = ti->ti_seq; 177 tcp_sendseqinit(tp); 178 tcp_rcvseqinit(tp); 179 tp->t_state = TCPS_SYN_RECEIVED; 180 tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 181 goto trimthenstep6; 182 183 /* 184 * If the state is SYN_SENT: 185 * if seg contains an ACK, but not for our SYN, drop the input. 186 * if seg contains a RST, then drop the connection. 187 * if seg does not contain SYN, then drop it. 188 * Otherwise this is an acceptable SYN segment 189 * initialize tp->rcv_nxt and tp->irs 190 * if seg contains ack then advance tp->snd_una 191 * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 192 * arrange for segment to be acked (eventually) 193 * continue processing rest of data/controls, beginning with URG 194 */ 195 case TCPS_SYN_SENT: 196 if ((tiflags & TH_ACK) && 197 /* this should be SEQ_LT; is SEQ_LEQ for BBN vax TCP only */ 198 (SEQ_LT(ti->ti_ack, tp->iss) || 199 SEQ_GT(ti->ti_ack, tp->snd_max))) 200 goto dropwithreset; 201 if (tiflags & TH_RST) { 202 if (tiflags & TH_ACK) 203 tcp_drop(tp, ECONNREFUSED); 204 goto drop; 205 } 206 if ((tiflags & TH_SYN) == 0) 207 goto drop; 208 tp->snd_una = ti->ti_ack; 209 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 210 tp->snd_nxt = tp->snd_una; 211 tp->t_timer[TCPT_REXMT] = 0; 212 tp->irs = ti->ti_seq; 213 tcp_rcvseqinit(tp); 214 tp->t_flags |= TF_ACKNOW; 215 if (SEQ_GT(tp->snd_una, tp->iss)) { 216 so->so_state |= SS_CONNAWAITING; 217 soisconnected(so); 218 tp->t_state = TCPS_ESTABLISHED; 219 (void) tcp_reass(tp, (struct tcpiphdr *)0); 220 } else 221 tp->t_state = TCPS_SYN_RECEIVED; 222 goto trimthenstep6; 223 224 trimthenstep6: 225 /* 226 * Advance ti->ti_seq to correspond to first data byte. 227 * If data, trim to stay within window, 228 * dropping FIN if necessary. 229 */ 230 ti->ti_seq++; 231 if (ti->ti_len > tp->rcv_wnd) { 232 todrop = ti->ti_len - tp->rcv_wnd; 233 m_adj(m, -todrop); 234 ti->ti_len = tp->rcv_wnd; 235 ti->ti_flags &= ~TH_FIN; 236 } 237 tp->snd_wl1 = ti->ti_seq - 1; 238 goto step6; 239 } 240 241 /* 242 * States other than LISTEN or SYN_SENT. 243 * First check that at least some bytes of segment are within 244 * receive window. 245 */ 246 if (tp->rcv_wnd == 0) { 247 /* 248 * If window is closed can only take segments at 249 * window edge, and have to drop data and PUSH from 250 * incoming segments. 251 */ 252 if (tp->rcv_nxt != ti->ti_seq) 253 goto dropafterack; 254 if (ti->ti_len > 0) { 255 ti->ti_len = 0; 256 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 257 } 258 } else { 259 /* 260 * If segment begins before rcv_nxt, drop leading 261 * data (and SYN); if nothing left, just ack. 262 */ 263 if (SEQ_GT(tp->rcv_nxt, ti->ti_seq)) { 264 todrop = tp->rcv_nxt - ti->ti_seq; 265 if (tiflags & TH_SYN) { 266 tiflags &= ~TH_SYN; 267 ti->ti_seq++; 268 if (ti->ti_urp > 1) 269 ti->ti_urp--; 270 else 271 tiflags &= ~TH_URG; 272 todrop--; 273 } 274 if (todrop > ti->ti_len) 275 goto dropafterack; 276 m_adj(m, todrop); 277 ti->ti_seq += todrop; 278 ti->ti_len -= todrop; 279 if (ti->ti_urp > todrop) 280 ti->ti_urp -= todrop; 281 else { 282 tiflags &= ~TH_URG; 283 /* ti->ti_flags &= ~TH_URG; */ 284 /* ti->ti_urp = 0; */ 285 } 286 /* tiflags &= ~TH_SYN; */ 287 /* ti->ti_flags &= ~TH_SYN; */ 288 } 289 /* 290 * If segment ends after window, drop trailing data 291 * (and PUSH and FIN); if nothing left, just ACK. 292 */ 293 if (SEQ_GT(ti->ti_seq+ti->ti_len, tp->rcv_nxt+tp->rcv_wnd)) { 294 todrop = 295 ti->ti_seq+ti->ti_len - (tp->rcv_nxt+tp->rcv_wnd); 296 if (todrop > ti->ti_len) 297 goto dropafterack; 298 m_adj(m, -todrop); 299 ti->ti_len -= todrop; 300 ti->ti_flags &= ~(TH_PUSH|TH_FIN); 301 } 302 } 303 304 /* 305 * If the RST bit is set examine the state: 306 * SYN_RECEIVED STATE: 307 * If passive open, return to LISTEN state. 308 * If active open, inform user that connection was refused. 309 * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 310 * Inform user that connection was reset, and close tcb. 311 * CLOSING, LAST_ACK, TIME_WAIT STATES 312 * Close the tcb. 313 */ 314 if (tiflags&TH_RST) switch (tp->t_state) { 315 316 case TCPS_SYN_RECEIVED: 317 if (inp->inp_socket->so_options & SO_ACCEPTCONN) { 318 /* a miniature tcp_close, but invisible to user */ 319 (void) m_free(dtom(tp->t_template)); 320 (void) m_free(dtom(tp)); 321 inp->inp_ppcb = 0; 322 tp = tcp_newtcpcb(inp); 323 tp->t_state = TCPS_LISTEN; 324 goto drop; 325 } 326 tcp_drop(tp, ECONNREFUSED); 327 goto drop; 328 329 case TCPS_ESTABLISHED: 330 case TCPS_FIN_WAIT_1: 331 case TCPS_FIN_WAIT_2: 332 case TCPS_CLOSE_WAIT: 333 tcp_drop(tp, ECONNRESET); 334 goto drop; 335 336 case TCPS_CLOSING: 337 case TCPS_LAST_ACK: 338 case TCPS_TIME_WAIT: 339 tcp_close(tp); 340 goto drop; 341 } 342 343 /* 344 * If a SYN is in the window, then this is an 345 * error and we send an RST and drop the connection. 346 */ 347 if (tiflags & TH_SYN) { 348 tcp_drop(tp, ECONNRESET); 349 goto dropwithreset; 350 } 351 352 /* 353 * If the ACK bit is off we drop the segment and return. 354 */ 355 if ((tiflags & TH_ACK) == 0) 356 goto drop; 357 358 /* 359 * Ack processing. 360 */ 361 switch (tp->t_state) { 362 363 /* 364 * In SYN_RECEIVED state if the ack ACKs our SYN then enter 365 * ESTABLISHED state and continue processing, othewise 366 * send an RST. 367 */ 368 case TCPS_SYN_RECEIVED: 369 if (SEQ_GT(tp->snd_una, ti->ti_ack) || 370 SEQ_GT(ti->ti_ack, tp->snd_max)) 371 goto dropwithreset; 372 tp->snd_una++; /* SYN acked */ 373 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 374 tp->snd_nxt = tp->snd_una; 375 tp->t_timer[TCPT_REXMT] = 0; 376 so->so_state |= SS_CONNAWAITING; 377 soisconnected(so); 378 tp->t_state = TCPS_ESTABLISHED; 379 (void) tcp_reass(tp, (struct tcpiphdr *)0); 380 tp->snd_wl1 = ti->ti_seq - 1; 381 /* fall into ... */ 382 383 /* 384 * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 385 * ACKs. If the ack is in the range 386 * tp->snd_una < ti->ti_ack <= tp->snd_max 387 * then advance tp->snd_una to ti->ti_ack and drop 388 * data from the retransmission queue. If this ACK reflects 389 * more up to date window information we update our window information. 390 */ 391 case TCPS_ESTABLISHED: 392 case TCPS_FIN_WAIT_1: 393 case TCPS_FIN_WAIT_2: 394 case TCPS_CLOSE_WAIT: 395 case TCPS_CLOSING: 396 case TCPS_LAST_ACK: 397 case TCPS_TIME_WAIT: 398 #define ourfinisacked (acked > 0) 399 400 if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 401 break; 402 if (SEQ_GT(ti->ti_ack, tp->snd_max)) 403 goto dropafterack; 404 acked = ti->ti_ack - tp->snd_una; 405 if (ti->ti_ack == tp->snd_max) 406 tp->t_timer[TCPT_REXMT] = 0; 407 else { 408 TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 409 tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 410 tp->t_rtt = 0; 411 tp->t_rxtshift = 0; 412 } 413 if (acked > so->so_snd.sb_cc) { 414 sbdrop(&so->so_snd, so->so_snd.sb_cc); 415 tp->snd_wnd -= so->so_snd.sb_cc; 416 } else { 417 sbdrop(&so->so_snd.sb_cc, acked); 418 tp->snd_wnd -= acked; 419 acked = 0; 420 } 421 if (so->so_snd.sb_flags & SB_WAIT) 422 sowwakeup(so); 423 tp->snd_una = ti->ti_ack; 424 if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 425 tp->snd_nxt = tp->snd_una; 426 427 /* 428 * If transmit timer is running and timed sequence 429 * number was acked, update smoothed round trip time. 430 */ 431 if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 432 if (tp->t_srtt == 0) 433 tp->t_srtt = tp->t_rtt; 434 else 435 tp->t_srtt = 436 tcp_alpha * tp->t_srtt + 437 (1 - tcp_alpha) * tp->t_rtt; 438 tp->t_rtt = 0; 439 } 440 441 switch (tp->t_state) { 442 443 /* 444 * In FIN_WAIT_1 STATE in addition to the processing 445 * for the ESTABLISHED state if our FIN is now acknowledged 446 * then enter FIN_WAIT_2. 447 */ 448 case TCPS_FIN_WAIT_1: 449 if (ourfinisacked) 450 tp->t_state = TCPS_FIN_WAIT_2; 451 break; 452 453 /* 454 * In CLOSING STATE in addition to the processing for 455 * the ESTABLISHED state if the ACK acknowledges our FIN 456 * then enter the TIME-WAIT state, otherwise ignore 457 * the segment. 458 */ 459 case TCPS_CLOSING: 460 if (ourfinisacked) { 461 tp->t_state = TCPS_TIME_WAIT; 462 tcp_canceltimers(tp); 463 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 464 soisdisconnected(so); 465 } 466 break; 467 468 /* 469 * The only thing that can arrive in LAST_ACK state 470 * is an acknowledgment of our FIN. If our FIN is now 471 * acknowledged, delete the TCB, enter the closed state 472 * and return. 473 */ 474 case TCPS_LAST_ACK: 475 if (ourfinisacked) 476 tcp_close(tp); 477 goto drop; 478 479 /* 480 * In TIME_WAIT state the only thing that should arrive 481 * is a retransmission of the remote FIN. Acknowledge 482 * it and restart the finack timer. 483 */ 484 case TCPS_TIME_WAIT: 485 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 486 goto dropafterack; 487 } 488 #undef ourfinisacked 489 } 490 491 step6: 492 /* 493 * Update window information. 494 */ 495 if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 496 (SEQ_LEQ(tp->snd_wl2, ti->ti_ack) || 497 tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { 498 tp->snd_wnd = ti->ti_win; 499 tp->snd_wl1 = ti->ti_seq; 500 tp->snd_wl2 = ti->ti_ack; 501 if (tp->snd_wnd > 0) 502 tp->t_timer[TCPT_PERSIST] = 0; 503 } 504 505 /* 506 * If an URG bit is set in the segment and is greater than the 507 * current known urgent pointer, then signal the user that the 508 * remote side has out of band data. This should not happen 509 * in CLOSE_WAIT, CLOSING, LAST-ACK or TIME_WAIT STATES since 510 * a FIN has been received from the remote side. In these states 511 * we ignore the URG. 512 */ 513 if ((tiflags & TH_URG) == 0 && TCPS_HAVERCVDFIN(tp->t_state) == 0) 514 if (SEQ_GT(ti->ti_urp, tp->rcv_up)) { 515 tp->rcv_up = ti->ti_urp; 516 #if 0 517 sohasoutofband(so); /* XXX */ 518 #endif 519 } 520 521 /* 522 * Process the segment text, merging it into the TCP sequencing queue, 523 * and arranging for acknowledgment of receipt if necessary. 524 * This process logically involves adjusting tp->rcv_wnd as data 525 * is presented to the user (this happens in tcp_usrreq.c, 526 * case PRU_RCVD). If a FIN has already been received on this 527 * connection then we just ignore the text. 528 */ 529 if ((ti->ti_len || (tiflags&TH_FIN)) && 530 TCPS_HAVERCVDFIN(tp->t_state) == 0) { 531 off += sizeof (struct ip); /* drop IP header */ 532 m->m_off += off; 533 m->m_len -= off; 534 tiflags = tcp_reass(tp, ti); 535 { extern tcpdelack; 536 if (tcpdelack) tp->t_flags |= TF_DELACK; else 537 tp->t_flags |= TF_ACKNOW; /* XXX TF_DELACK */ 538 } 539 } else { 540 m_freem(m); 541 tiflags &= ~TH_FIN; 542 } 543 544 /* 545 * If FIN is received ACK the FIN and let the user know 546 * that the connection is closing. 547 */ 548 if (tiflags & TH_FIN) { 549 if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 550 socantrcvmore(so); 551 tp->t_flags |= TF_ACKNOW; 552 tp->rcv_nxt++; 553 } 554 switch (tp->t_state) { 555 556 /* 557 * In SYN_RECEIVED and ESTABLISHED STATES 558 * enter the CLOSE_WAIT state. 559 */ 560 case TCPS_SYN_RECEIVED: 561 case TCPS_ESTABLISHED: 562 tp->t_state = TCPS_CLOSE_WAIT; 563 break; 564 565 /* 566 * If still in FIN_WAIT_1 STATE FIN has not been acked so 567 * enter the CLOSING state. 568 */ 569 case TCPS_FIN_WAIT_1: 570 tp->t_state = TCPS_CLOSING; 571 break; 572 573 /* 574 * In FIN_WAIT_2 state enter the TIME_WAIT state, 575 * starting the time-wait timer, turning off the other 576 * standard timers. 577 */ 578 case TCPS_FIN_WAIT_2: 579 tp->t_state = TCPS_TIME_WAIT; 580 tcp_canceltimers(tp); 581 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 582 soisdisconnected(so); 583 break; 584 585 /* 586 * In TIME_WAIT state restart the 2 MSL time_wait timer. 587 */ 588 case TCPS_TIME_WAIT: 589 tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 590 break; 591 } 592 } 593 if (so->so_options & SO_DEBUG) 594 tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 595 596 /* 597 * Return any desired output. 598 */ 599 tcp_output(tp); 600 return; 601 602 dropafterack: 603 /* 604 * Generate an ACK dropping incoming segment. 605 * Make ACK reflect our state. 606 */ 607 if (tiflags & TH_RST) 608 goto drop; 609 tcp_respond(ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 610 return; 611 612 dropwithreset: 613 /* 614 * Generate a RST, dropping incoming segment. 615 * Make ACK acceptable to originator of segment. 616 */ 617 if (tiflags & TH_RST) 618 goto drop; 619 if (tiflags & TH_ACK) 620 tcp_respond(ti, (tcp_seq)0, ti->ti_ack, TH_RST); 621 else { 622 if (tiflags & TH_SYN) 623 ti->ti_len++; 624 tcp_respond(ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, TH_RST|TH_ACK); 625 } 626 return; 627 628 drop: 629 /* 630 * Drop space held by incoming segment and return. 631 */ 632 m_freem(m); 633 return; 634 } 635 636 /* 637 * Insert segment ti into reassembly queue of tcp with 638 * control block tp. Return TH_FIN if reassembly now includes 639 * a segment with FIN. 640 */ 641 tcp_reass(tp, ti) 642 register struct tcpcb *tp; 643 register struct tcpiphdr *ti; 644 { 645 register struct tcpiphdr *q; 646 struct socket *so = tp->t_inpcb->inp_socket; 647 struct mbuf *m; 648 int flags; 649 COUNT(TCP_REASS); 650 651 /* 652 * Call with ti==0 after become established to 653 * force pre-ESTABLISHED data up to user socket. 654 */ 655 if (ti == 0) 656 goto present; 657 658 /* 659 * Find a segment which begins after this one does. 660 */ 661 for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 662 q = (struct tcpiphdr *)q->ti_next) 663 if (SEQ_GT(q->ti_seq, ti->ti_seq)) 664 break; 665 666 /* 667 * If there is a preceding segment, it may provide some of 668 * our data already. If so, drop the data from the incoming 669 * segment. If it provides all of our data, drop us. 670 */ 671 if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 672 register int i; 673 q = (struct tcpiphdr *)(q->ti_prev); 674 /* conversion to int (in i) handles seq wraparound */ 675 i = q->ti_seq + q->ti_len - ti->ti_seq; 676 if (i > 0) { 677 if (i >= ti->ti_len) 678 goto drop; 679 m_adj(dtom(tp), i); 680 ti->ti_len -= i; 681 ti->ti_seq += i; 682 } 683 q = (struct tcpiphdr *)(q->ti_next); 684 } 685 686 /* 687 * While we overlap succeeding segments trim them or, 688 * if they are completely covered, dequeue them. 689 */ 690 while (q != (struct tcpiphdr *)tp && 691 SEQ_GT(ti->ti_seq + ti->ti_len, q->ti_seq)) { 692 register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 693 if (i < q->ti_len) { 694 q->ti_len -= i; 695 m_adj(dtom(q), i); 696 break; 697 } 698 q = (struct tcpiphdr *)q->ti_next; 699 m_freem(dtom(q->ti_prev)); 700 remque(q->ti_prev); 701 } 702 703 /* 704 * Stick new segment in its place. 705 */ 706 insque(ti, q->ti_prev); 707 708 present: 709 /* 710 * Present data to user, advancing rcv_nxt through 711 * completed sequence space. 712 */ 713 if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 714 return (0); 715 ti = tp->seg_next; 716 if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 717 return (0); 718 if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 719 return (0); 720 do { 721 tp->rcv_nxt += ti->ti_len; 722 flags = ti->ti_flags & TH_FIN; 723 remque(ti); 724 m = dtom(ti); 725 ti = (struct tcpiphdr *)ti->ti_next; 726 if (so->so_state & SS_CANTRCVMORE) 727 (void) m_freem(m); 728 else 729 sbappend(&so->so_rcv, m); 730 } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 731 sorwakeup(so); 732 return (flags); 733 drop: 734 m_freem(dtom(ti)); 735 return (0); 736 } 737