1: /* 2: * Copyright (c) 1982, 1986 Regents of the University of California. 3: * All rights reserved. The Berkeley software License Agreement 4: * specifies the terms and conditions for redistribution. 5: * 6: * @(#)tcp_input.c 7.1 (Berkeley) 6/5/86 7: */ 8: 9: #include "param.h" 10: #include "systm.h" 11: #include "mbuf.h" 12: #include "protosw.h" 13: #include "socket.h" 14: #include "socketvar.h" 15: #include "errno.h" 16: 17: #include "../net/if.h" 18: #include "../net/route.h" 19: 20: #include "in.h" 21: #include "in_pcb.h" 22: #include "in_systm.h" 23: #include "ip.h" 24: #include "ip_var.h" 25: #include "tcp.h" 26: #include "tcp_fsm.h" 27: #include "tcp_seq.h" 28: #include "tcp_timer.h" 29: #include "tcp_var.h" 30: #include "tcpip.h" 31: #include "tcp_debug.h" 32: 33: int tcpprintfs = 0; 34: int tcpcksum = 1; 35: struct tcpiphdr tcp_saveti; 36: extern tcpnodelack; 37: 38: struct tcpcb *tcp_newtcpcb(); 39: 40: /* 41: * Insert segment ti into reassembly queue of tcp with 42: * control block tp. Return TH_FIN if reassembly now includes 43: * a segment with FIN. The macro form does the common case inline 44: * (segment is the next to be received on an established connection, 45: * and the queue is empty), avoiding linkage into and removal 46: * from the queue and repetition of various conversions. 47: */ 48: #define TCP_REASS(tp, ti, m, so, flags) { \ 49: if ((ti)->ti_seq == (tp)->rcv_nxt && \ 50: (tp)->seg_next == (struct tcpiphdr *)(tp) && \ 51: (tp)->t_state == TCPS_ESTABLISHED) { \ 52: (tp)->rcv_nxt += (ti)->ti_len; \ 53: flags = (ti)->ti_flags & TH_FIN; \ 54: sbappend(&(so)->so_rcv, (m)); \ 55: sorwakeup(so); \ 56: } else \ 57: (flags) = tcp_reass((tp), (ti)); \ 58: } 59: 60: tcp_reass(tp, ti) 61: register struct tcpcb *tp; 62: register struct tcpiphdr *ti; 63: { 64: register struct tcpiphdr *q; 65: struct socket *so = tp->t_inpcb->inp_socket; 66: struct mbuf *m; 67: int flags; 68: 69: /* 70: * Call with ti==0 after become established to 71: * force pre-ESTABLISHED data up to user socket. 72: */ 73: if (ti == 0) 74: goto present; 75: 76: /* 77: * Find a segment which begins after this one does. 78: */ 79: for (q = tp->seg_next; q != (struct tcpiphdr *)tp; 80: q = (struct tcpiphdr *)q->ti_next) 81: if (SEQ_GT(q->ti_seq, ti->ti_seq)) 82: break; 83: 84: /* 85: * If there is a preceding segment, it may provide some of 86: * our data already. If so, drop the data from the incoming 87: * segment. If it provides all of our data, drop us. 88: */ 89: if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { 90: register int i; 91: q = (struct tcpiphdr *)q->ti_prev; 92: /* conversion to int (in i) handles seq wraparound */ 93: i = q->ti_seq + q->ti_len - ti->ti_seq; 94: if (i > 0) { 95: if (i >= ti->ti_len) 96: goto drop; 97: m_adj(dtom(ti), i); 98: ti->ti_len -= i; 99: ti->ti_seq += i; 100: } 101: q = (struct tcpiphdr *)(q->ti_next); 102: } 103: 104: /* 105: * While we overlap succeeding segments trim them or, 106: * if they are completely covered, dequeue them. 107: */ 108: while (q != (struct tcpiphdr *)tp) { 109: register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; 110: if (i <= 0) 111: break; 112: if (i < q->ti_len) { 113: q->ti_seq += i; 114: q->ti_len -= i; 115: m_adj(dtom(q), i); 116: break; 117: } 118: q = (struct tcpiphdr *)q->ti_next; 119: m = dtom(q->ti_prev); 120: remque(q->ti_prev); 121: m_freem(m); 122: } 123: 124: /* 125: * Stick new segment in its place. 126: */ 127: insque(ti, q->ti_prev); 128: 129: present: 130: /* 131: * Present data to user, advancing rcv_nxt through 132: * completed sequence space. 133: */ 134: if (TCPS_HAVERCVDSYN(tp->t_state) == 0) 135: return (0); 136: ti = tp->seg_next; 137: if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) 138: return (0); 139: if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) 140: return (0); 141: do { 142: tp->rcv_nxt += ti->ti_len; 143: flags = ti->ti_flags & TH_FIN; 144: remque(ti); 145: m = dtom(ti); 146: ti = (struct tcpiphdr *)ti->ti_next; 147: if (so->so_state & SS_CANTRCVMORE) 148: m_freem(m); 149: else 150: sbappend(&so->so_rcv, m); 151: } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); 152: sorwakeup(so); 153: return (flags); 154: drop: 155: m_freem(dtom(ti)); 156: return (0); 157: } 158: 159: /* 160: * TCP input routine, follows pages 65-76 of the 161: * protocol specification dated September, 1981 very closely. 162: */ 163: tcp_input(m0) 164: struct mbuf *m0; 165: { 166: register struct tcpiphdr *ti; 167: struct inpcb *inp; 168: register struct mbuf *m; 169: struct mbuf *om = 0; 170: int len, tlen, off; 171: register struct tcpcb *tp = 0; 172: register int tiflags; 173: struct socket *so; 174: int todrop, acked, needoutput = 0; 175: short ostate; 176: struct in_addr laddr; 177: int dropsocket = 0; 178: 179: /* 180: * Get IP and TCP header together in first mbuf. 181: * Note: IP leaves IP header in first mbuf. 182: */ 183: m = m0; 184: ti = mtod(m, struct tcpiphdr *); 185: if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) 186: ip_stripoptions((struct ip *)ti, (struct mbuf *)0); 187: if (m->m_off > MMAXOFF || m->m_len < sizeof (struct tcpiphdr)) { 188: if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { 189: tcpstat.tcps_hdrops++; 190: return; 191: } 192: ti = mtod(m, struct tcpiphdr *); 193: } 194: 195: /* 196: * Checksum extended TCP header and data. 197: */ 198: tlen = ((struct ip *)ti)->ip_len; 199: len = sizeof (struct ip) + tlen; 200: if (tcpcksum) { 201: ti->ti_next = ti->ti_prev = 0; 202: ti->ti_x1 = 0; 203: ti->ti_len = (u_short)tlen; 204: ti->ti_len = htons((u_short)ti->ti_len); 205: if (ti->ti_sum = in_cksum(m, len)) { 206: if (tcpprintfs) 207: printf("tcp sum: src %x\n", ti->ti_src); 208: tcpstat.tcps_badsum++; 209: goto drop; 210: } 211: } 212: 213: /* 214: * Check that TCP offset makes sense, 215: * pull out TCP options and adjust length. 216: */ 217: off = ti->ti_off << 2; 218: if (off < sizeof (struct tcphdr) || off > tlen) { 219: if (tcpprintfs) 220: printf("tcp off: src %x off %d\n", ti->ti_src, off); 221: tcpstat.tcps_badoff++; 222: goto drop; 223: } 224: tlen -= off; 225: ti->ti_len = tlen; 226: if (off > sizeof (struct tcphdr)) { 227: if (m->m_len < sizeof(struct ip) + off) { 228: if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { 229: tcpstat.tcps_hdrops++; 230: return; 231: } 232: ti = mtod(m, struct tcpiphdr *); 233: } 234: om = m_get(M_DONTWAIT, MT_DATA); 235: if (om == 0) 236: goto drop; 237: om->m_len = off - sizeof (struct tcphdr); 238: { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); 239: bcopy(op, mtod(om, caddr_t), (unsigned)om->m_len); 240: m->m_len -= om->m_len; 241: bcopy(op+om->m_len, op, 242: (unsigned)(m->m_len-sizeof (struct tcpiphdr))); 243: } 244: } 245: tiflags = ti->ti_flags; 246: 247: /* 248: * Drop TCP and IP headers; TCP options were dropped above. 249: */ 250: m->m_off += sizeof(struct tcpiphdr); 251: m->m_len -= sizeof(struct tcpiphdr); 252: 253: /* 254: * Convert TCP protocol specific fields to host format. 255: */ 256: ti->ti_seq = ntohl(ti->ti_seq); 257: ti->ti_ack = ntohl(ti->ti_ack); 258: ti->ti_win = ntohs(ti->ti_win); 259: ti->ti_urp = ntohs(ti->ti_urp); 260: 261: /* 262: * Locate pcb for segment. 263: */ 264: inp = in_pcblookup 265: (&tcb, ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport, 266: INPLOOKUP_WILDCARD); 267: 268: /* 269: * If the state is CLOSED (i.e., TCB does not exist) then 270: * all data in the incoming segment is discarded. 271: */ 272: if (inp == 0) 273: goto dropwithreset; 274: tp = intotcpcb(inp); 275: if (tp == 0) 276: goto dropwithreset; 277: so = inp->inp_socket; 278: if (so->so_options & SO_DEBUG) { 279: ostate = tp->t_state; 280: tcp_saveti = *ti; 281: } 282: if (so->so_options & SO_ACCEPTCONN) { 283: so = sonewconn(so); 284: if (so == 0) 285: goto drop; 286: /* 287: * This is ugly, but .... 288: * 289: * Mark socket as temporary until we're 290: * committed to keeping it. The code at 291: * ``drop'' and ``dropwithreset'' check the 292: * flag dropsocket to see if the temporary 293: * socket created here should be discarded. 294: * We mark the socket as discardable until 295: * we're committed to it below in TCPS_LISTEN. 296: */ 297: dropsocket++; 298: inp = (struct inpcb *)so->so_pcb; 299: inp->inp_laddr = ti->ti_dst; 300: inp->inp_lport = ti->ti_dport; 301: inp->inp_options = ip_srcroute(); 302: tp = intotcpcb(inp); 303: tp->t_state = TCPS_LISTEN; 304: } 305: 306: /* 307: * Segment received on connection. 308: * Reset idle time and keep-alive timer. 309: */ 310: tp->t_idle = 0; 311: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 312: 313: /* 314: * Process options if not in LISTEN state, 315: * else do it below (after getting remote address). 316: */ 317: if (om && tp->t_state != TCPS_LISTEN) { 318: tcp_dooptions(tp, om, ti); 319: om = 0; 320: } 321: 322: /* 323: * Calculate amount of space in receive window, 324: * and then do TCP input processing. 325: * Receive window is amount of space in rcv queue, 326: * but not less than advertised window. 327: */ 328: { int win; 329: 330: win = sbspace(&so->so_rcv); 331: if (win < 0) 332: win = 0; 333: tp->rcv_wnd = MAX(win, (int)(tp->rcv_adv - tp->rcv_nxt)); 334: } 335: 336: switch (tp->t_state) { 337: 338: /* 339: * If the state is LISTEN then ignore segment if it contains an RST. 340: * If the segment contains an ACK then it is bad and send a RST. 341: * If it does not contain a SYN then it is not interesting; drop it. 342: * Don't bother responding if the destination was a broadcast. 343: * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial 344: * tp->iss, and send a segment: 345: * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> 346: * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. 347: * Fill in remote peer address fields if not previously specified. 348: * Enter SYN_RECEIVED state, and process any other fields of this 349: * segment in this state. 350: */ 351: case TCPS_LISTEN: { 352: struct mbuf *am; 353: register struct sockaddr_in *sin; 354: 355: if (tiflags & TH_RST) 356: goto drop; 357: if (tiflags & TH_ACK) 358: goto dropwithreset; 359: if ((tiflags & TH_SYN) == 0) 360: goto drop; 361: if (in_broadcast(ti->ti_dst)) 362: goto drop; 363: am = m_get(M_DONTWAIT, MT_SONAME); 364: if (am == NULL) 365: goto drop; 366: am->m_len = sizeof (struct sockaddr_in); 367: sin = mtod(am, struct sockaddr_in *); 368: sin->sin_family = AF_INET; 369: sin->sin_addr = ti->ti_src; 370: sin->sin_port = ti->ti_sport; 371: laddr = inp->inp_laddr; 372: if (inp->inp_laddr.s_addr == INADDR_ANY) 373: inp->inp_laddr = ti->ti_dst; 374: if (in_pcbconnect(inp, am)) { 375: inp->inp_laddr = laddr; 376: (void) m_free(am); 377: goto drop; 378: } 379: (void) m_free(am); 380: tp->t_template = tcp_template(tp); 381: if (tp->t_template == 0) { 382: tp = tcp_drop(tp, ENOBUFS); 383: dropsocket = 0; /* socket is already gone */ 384: goto drop; 385: } 386: if (om) { 387: tcp_dooptions(tp, om, ti); 388: om = 0; 389: } 390: tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; 391: tp->irs = ti->ti_seq; 392: tcp_sendseqinit(tp); 393: tcp_rcvseqinit(tp); 394: tp->t_flags |= TF_ACKNOW; 395: tp->t_state = TCPS_SYN_RECEIVED; 396: tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; 397: dropsocket = 0; /* committed to socket */ 398: goto trimthenstep6; 399: } 400: 401: /* 402: * If the state is SYN_SENT: 403: * if seg contains an ACK, but not for our SYN, drop the input. 404: * if seg contains a RST, then drop the connection. 405: * if seg does not contain SYN, then drop it. 406: * Otherwise this is an acceptable SYN segment 407: * initialize tp->rcv_nxt and tp->irs 408: * if seg contains ack then advance tp->snd_una 409: * if SYN has been acked change to ESTABLISHED else SYN_RCVD state 410: * arrange for segment to be acked (eventually) 411: * continue processing rest of data/controls, beginning with URG 412: */ 413: case TCPS_SYN_SENT: 414: if ((tiflags & TH_ACK) && 415: (SEQ_LEQ(ti->ti_ack, tp->iss) || 416: SEQ_GT(ti->ti_ack, tp->snd_max))) 417: goto dropwithreset; 418: if (tiflags & TH_RST) { 419: if (tiflags & TH_ACK) 420: tp = tcp_drop(tp, ECONNREFUSED); 421: goto drop; 422: } 423: if ((tiflags & TH_SYN) == 0) 424: goto drop; 425: tp->snd_una = ti->ti_ack; 426: if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 427: tp->snd_nxt = tp->snd_una; 428: tp->t_timer[TCPT_REXMT] = 0; 429: tp->irs = ti->ti_seq; 430: tcp_rcvseqinit(tp); 431: tp->t_flags |= TF_ACKNOW; 432: if (SEQ_GT(tp->snd_una, tp->iss)) { 433: soisconnected(so); 434: tp->t_state = TCPS_ESTABLISHED; 435: tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 436: (void) tcp_reass(tp, (struct tcpiphdr *)0); 437: } else 438: tp->t_state = TCPS_SYN_RECEIVED; 439: goto trimthenstep6; 440: 441: trimthenstep6: 442: /* 443: * Advance ti->ti_seq to correspond to first data byte. 444: * If data, trim to stay within window, 445: * dropping FIN if necessary. 446: */ 447: ti->ti_seq++; 448: if (ti->ti_len > tp->rcv_wnd) { 449: todrop = ti->ti_len - tp->rcv_wnd; 450: m_adj(m, -todrop); 451: ti->ti_len = tp->rcv_wnd; 452: tiflags &= ~TH_FIN; 453: } 454: tp->snd_wl1 = ti->ti_seq - 1; 455: tp->rcv_up = ti->ti_seq; 456: goto step6; 457: } 458: 459: /* 460: * If data is received on a connection after the 461: * user processes are gone, then RST the other end. 462: */ 463: if ((so->so_state & SS_NOFDREF) && tp->t_state > TCPS_CLOSE_WAIT && 464: ti->ti_len) { 465: tp = tcp_close(tp); 466: goto dropwithreset; 467: } 468: 469: /* 470: * States other than LISTEN or SYN_SENT. 471: * First check that at least some bytes of segment are within 472: * receive window. 473: */ 474: if (tp->rcv_wnd == 0) { 475: /* 476: * If window is closed can only take segments at 477: * window edge, and have to drop data and PUSH from 478: * incoming segments. 479: */ 480: if (tp->rcv_nxt != ti->ti_seq) 481: goto dropafterack; 482: if (ti->ti_len > 0) { 483: m_adj(m, ti->ti_len); 484: ti->ti_len = 0; 485: tiflags &= ~(TH_PUSH|TH_FIN); 486: } 487: } else { 488: /* 489: * If segment begins before rcv_nxt, drop leading 490: * data (and SYN); if nothing left, just ack. 491: */ 492: todrop = tp->rcv_nxt - ti->ti_seq; 493: if (todrop > 0) { 494: if (tiflags & TH_SYN) { 495: tiflags &= ~TH_SYN; 496: ti->ti_seq++; 497: if (ti->ti_urp > 1) 498: ti->ti_urp--; 499: else 500: tiflags &= ~TH_URG; 501: todrop--; 502: } 503: if (todrop > ti->ti_len || 504: todrop == ti->ti_len && (tiflags&TH_FIN) == 0) 505: goto dropafterack; 506: m_adj(m, todrop); 507: ti->ti_seq += todrop; 508: ti->ti_len -= todrop; 509: if (ti->ti_urp > todrop) 510: ti->ti_urp -= todrop; 511: else { 512: tiflags &= ~TH_URG; 513: ti->ti_urp = 0; 514: } 515: } 516: /* 517: * If segment ends after window, drop trailing data 518: * (and PUSH and FIN); if nothing left, just ACK. 519: */ 520: todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); 521: if (todrop > 0) { 522: if (todrop >= ti->ti_len) 523: goto dropafterack; 524: m_adj(m, -todrop); 525: ti->ti_len -= todrop; 526: tiflags &= ~(TH_PUSH|TH_FIN); 527: } 528: } 529: 530: /* 531: * If the RST bit is set examine the state: 532: * SYN_RECEIVED STATE: 533: * If passive open, return to LISTEN state. 534: * If active open, inform user that connection was refused. 535: * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: 536: * Inform user that connection was reset, and close tcb. 537: * CLOSING, LAST_ACK, TIME_WAIT STATES 538: * Close the tcb. 539: */ 540: if (tiflags&TH_RST) switch (tp->t_state) { 541: 542: case TCPS_SYN_RECEIVED: 543: tp = tcp_drop(tp, ECONNREFUSED); 544: goto drop; 545: 546: case TCPS_ESTABLISHED: 547: case TCPS_FIN_WAIT_1: 548: case TCPS_FIN_WAIT_2: 549: case TCPS_CLOSE_WAIT: 550: tp = tcp_drop(tp, ECONNRESET); 551: goto drop; 552: 553: case TCPS_CLOSING: 554: case TCPS_LAST_ACK: 555: case TCPS_TIME_WAIT: 556: tp = tcp_close(tp); 557: goto drop; 558: } 559: 560: /* 561: * If a SYN is in the window, then this is an 562: * error and we send an RST and drop the connection. 563: */ 564: if (tiflags & TH_SYN) { 565: tp = tcp_drop(tp, ECONNRESET); 566: goto dropwithreset; 567: } 568: 569: /* 570: * If the ACK bit is off we drop the segment and return. 571: */ 572: if ((tiflags & TH_ACK) == 0) 573: goto drop; 574: 575: /* 576: * Ack processing. 577: */ 578: switch (tp->t_state) { 579: 580: /* 581: * In SYN_RECEIVED state if the ack ACKs our SYN then enter 582: * ESTABLISHED state and continue processing, othewise 583: * send an RST. 584: */ 585: case TCPS_SYN_RECEIVED: 586: if (SEQ_GT(tp->snd_una, ti->ti_ack) || 587: SEQ_GT(ti->ti_ack, tp->snd_max)) 588: goto dropwithreset; 589: tp->snd_una++; /* SYN acked */ 590: if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 591: tp->snd_nxt = tp->snd_una; 592: tp->t_timer[TCPT_REXMT] = 0; 593: soisconnected(so); 594: tp->t_state = TCPS_ESTABLISHED; 595: tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 596: (void) tcp_reass(tp, (struct tcpiphdr *)0); 597: tp->snd_wl1 = ti->ti_seq - 1; 598: /* fall into ... */ 599: 600: /* 601: * In ESTABLISHED state: drop duplicate ACKs; ACK out of range 602: * ACKs. If the ack is in the range 603: * tp->snd_una < ti->ti_ack <= tp->snd_max 604: * then advance tp->snd_una to ti->ti_ack and drop 605: * data from the retransmission queue. If this ACK reflects 606: * more up to date window information we update our window information. 607: */ 608: case TCPS_ESTABLISHED: 609: case TCPS_FIN_WAIT_1: 610: case TCPS_FIN_WAIT_2: 611: case TCPS_CLOSE_WAIT: 612: case TCPS_CLOSING: 613: case TCPS_LAST_ACK: 614: case TCPS_TIME_WAIT: 615: #define ourfinisacked (acked > 0) 616: 617: if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) 618: break; 619: if (SEQ_GT(ti->ti_ack, tp->snd_max)) 620: goto dropafterack; 621: acked = ti->ti_ack - tp->snd_una; 622: 623: /* 624: * If transmit timer is running and timed sequence 625: * number was acked, update smoothed round trip time. 626: */ 627: if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { 628: if (tp->t_srtt == 0) 629: tp->t_srtt = tp->t_rtt; 630: else 631: tp->t_srtt = 632: tcp_alpha * tp->t_srtt + 633: (1 - tcp_alpha) * tp->t_rtt; 634: tp->t_rtt = 0; 635: } 636: 637: /* 638: * If all outstanding data is acked, stop retransmit 639: * timer and remember to restart (more output or persist). 640: * If there is more data to be acked, restart retransmit 641: * timer. 642: */ 643: if (ti->ti_ack == tp->snd_max) { 644: tp->t_timer[TCPT_REXMT] = 0; 645: needoutput = 1; 646: } else if (tp->t_timer[TCPT_PERSIST] == 0) { 647: TCPT_RANGESET(tp->t_timer[TCPT_REXMT], 648: tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); 649: tp->t_rxtshift = 0; 650: } 651: /* 652: * When new data is acked, open the congestion window a bit. 653: */ 654: if (acked > 0) 655: tp->snd_cwnd = MIN(11 * tp->snd_cwnd / 10, 65535); 656: if (acked > so->so_snd.sb_cc) { 657: tp->snd_wnd -= so->so_snd.sb_cc; 658: sbdrop(&so->so_snd, (int)so->so_snd.sb_cc); 659: } else { 660: sbdrop(&so->so_snd, acked); 661: tp->snd_wnd -= acked; 662: acked = 0; 663: } 664: if ((so->so_snd.sb_flags & SB_WAIT) || so->so_snd.sb_sel) 665: sowwakeup(so); 666: tp->snd_una = ti->ti_ack; 667: if (SEQ_LT(tp->snd_nxt, tp->snd_una)) 668: tp->snd_nxt = tp->snd_una; 669: 670: switch (tp->t_state) { 671: 672: /* 673: * In FIN_WAIT_1 STATE in addition to the processing 674: * for the ESTABLISHED state if our FIN is now acknowledged 675: * then enter FIN_WAIT_2. 676: */ 677: case TCPS_FIN_WAIT_1: 678: if (ourfinisacked) { 679: /* 680: * If we can't receive any more 681: * data, then closing user can proceed. 682: * Starting the timer is contrary to the 683: * specification, but if we don't get a FIN 684: * we'll hang forever. 685: */ 686: if (so->so_state & SS_CANTRCVMORE) { 687: soisdisconnected(so); 688: tp->t_timer[TCPT_2MSL] = TCPTV_MAXIDLE; 689: } 690: tp->t_state = TCPS_FIN_WAIT_2; 691: } 692: break; 693: 694: /* 695: * In CLOSING STATE in addition to the processing for 696: * the ESTABLISHED state if the ACK acknowledges our FIN 697: * then enter the TIME-WAIT state, otherwise ignore 698: * the segment. 699: */ 700: case TCPS_CLOSING: 701: if (ourfinisacked) { 702: tp->t_state = TCPS_TIME_WAIT; 703: tcp_canceltimers(tp); 704: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 705: soisdisconnected(so); 706: } 707: break; 708: 709: /* 710: * The only thing that can arrive in LAST_ACK state 711: * is an acknowledgment of our FIN. If our FIN is now 712: * acknowledged, delete the TCB, enter the closed state 713: * and return. 714: */ 715: case TCPS_LAST_ACK: 716: if (ourfinisacked) 717: tp = tcp_close(tp); 718: goto drop; 719: 720: /* 721: * In TIME_WAIT state the only thing that should arrive 722: * is a retransmission of the remote FIN. Acknowledge 723: * it and restart the finack timer. 724: */ 725: case TCPS_TIME_WAIT: 726: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 727: goto dropafterack; 728: } 729: #undef ourfinisacked 730: } 731: 732: step6: 733: /* 734: * Update window information. 735: * Don't look at window if no ACK: TAC's send garbage on first SYN. 736: */ 737: if ((tiflags & TH_ACK) && 738: (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && 739: (SEQ_LT(tp->snd_wl2, ti->ti_ack) || 740: tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd))) { 741: tp->snd_wnd = ti->ti_win; 742: tp->snd_wl1 = ti->ti_seq; 743: tp->snd_wl2 = ti->ti_ack; 744: if (tp->snd_wnd > tp->max_sndwnd) 745: tp->max_sndwnd = tp->snd_wnd; 746: needoutput = 1; 747: } 748: 749: /* 750: * Process segments with URG. 751: */ 752: if ((tiflags & TH_URG) && ti->ti_urp && 753: TCPS_HAVERCVDFIN(tp->t_state) == 0) { 754: /* 755: * This is a kludge, but if we receive and accept 756: * random urgent pointers, we'll crash in 757: * soreceive. It's hard to imagine someone 758: * actually wanting to send this much urgent data. 759: */ 760: if (ti->ti_urp + so->so_rcv.sb_cc > SB_MAX) { 761: ti->ti_urp = 0; /* XXX */ 762: tiflags &= ~TH_URG; /* XXX */ 763: goto dodata; /* XXX */ 764: } 765: /* 766: * If this segment advances the known urgent pointer, 767: * then mark the data stream. This should not happen 768: * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since 769: * a FIN has been received from the remote side. 770: * In these states we ignore the URG. 771: * 772: * According to RFC961 (Assigned Protocols), 773: * the urgent pointer points to the last octet 774: * of urgent data. We continue, however, 775: * to consider it to indicate the first octet 776: * of data past the urgent section 777: * as the original spec states. 778: */ 779: if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { 780: tp->rcv_up = ti->ti_seq + ti->ti_urp; 781: so->so_oobmark = so->so_rcv.sb_cc + 782: (tp->rcv_up - tp->rcv_nxt) - 1; 783: if (so->so_oobmark == 0) 784: so->so_state |= SS_RCVATMARK; 785: sohasoutofband(so); 786: tp->t_oobflags &= ~(TCPOOB_HAVEDATA | TCPOOB_HADDATA); 787: } 788: /* 789: * Remove out of band data so doesn't get presented to user. 790: * This can happen independent of advancing the URG pointer, 791: * but if two URG's are pending at once, some out-of-band 792: * data may creep in... ick. 793: */ 794: if (ti->ti_urp <= ti->ti_len && 795: (so->so_options & SO_OOBINLINE) == 0) 796: tcp_pulloutofband(so, ti); 797: } else 798: /* 799: * If no out of band data is expected, 800: * pull receive urgent pointer along 801: * with the receive window. 802: */ 803: if (SEQ_GT(tp->rcv_nxt, tp->rcv_up)) 804: tp->rcv_up = tp->rcv_nxt; 805: dodata: /* XXX */ 806: 807: /* 808: * Process the segment text, merging it into the TCP sequencing queue, 809: * and arranging for acknowledgment of receipt if necessary. 810: * This process logically involves adjusting tp->rcv_wnd as data 811: * is presented to the user (this happens in tcp_usrreq.c, 812: * case PRU_RCVD). If a FIN has already been received on this 813: * connection then we just ignore the text. 814: */ 815: if ((ti->ti_len || (tiflags&TH_FIN)) && 816: TCPS_HAVERCVDFIN(tp->t_state) == 0) { 817: TCP_REASS(tp, ti, m, so, tiflags); 818: if (tcpnodelack == 0) 819: tp->t_flags |= TF_DELACK; 820: else 821: tp->t_flags |= TF_ACKNOW; 822: /* 823: * Note the amount of data that peer has sent into 824: * our window, in order to estimate the sender's 825: * buffer size. 826: */ 827: len = so->so_rcv.sb_hiwat - (tp->rcv_nxt - tp->rcv_adv); 828: if (len > tp->max_rcvd) 829: tp->max_rcvd = len; 830: } else { 831: m_freem(m); 832: tiflags &= ~TH_FIN; 833: } 834: 835: /* 836: * If FIN is received ACK the FIN and let the user know 837: * that the connection is closing. 838: */ 839: if (tiflags & TH_FIN) { 840: if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { 841: socantrcvmore(so); 842: tp->t_flags |= TF_ACKNOW; 843: tp->rcv_nxt++; 844: } 845: switch (tp->t_state) { 846: 847: /* 848: * In SYN_RECEIVED and ESTABLISHED STATES 849: * enter the CLOSE_WAIT state. 850: */ 851: case TCPS_SYN_RECEIVED: 852: case TCPS_ESTABLISHED: 853: tp->t_state = TCPS_CLOSE_WAIT; 854: break; 855: 856: /* 857: * If still in FIN_WAIT_1 STATE FIN has not been acked so 858: * enter the CLOSING state. 859: */ 860: case TCPS_FIN_WAIT_1: 861: tp->t_state = TCPS_CLOSING; 862: break; 863: 864: /* 865: * In FIN_WAIT_2 state enter the TIME_WAIT state, 866: * starting the time-wait timer, turning off the other 867: * standard timers. 868: */ 869: case TCPS_FIN_WAIT_2: 870: tp->t_state = TCPS_TIME_WAIT; 871: tcp_canceltimers(tp); 872: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 873: soisdisconnected(so); 874: break; 875: 876: /* 877: * In TIME_WAIT state restart the 2 MSL time_wait timer. 878: */ 879: case TCPS_TIME_WAIT: 880: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; 881: break; 882: } 883: } 884: if (so->so_options & SO_DEBUG) 885: tcp_trace(TA_INPUT, ostate, tp, &tcp_saveti, 0); 886: 887: /* 888: * Return any desired output. 889: */ 890: if (needoutput || (tp->t_flags & TF_ACKNOW)) 891: (void) tcp_output(tp); 892: return; 893: 894: dropafterack: 895: /* 896: * Generate an ACK dropping incoming segment if it occupies 897: * sequence space, where the ACK reflects our state. 898: */ 899: if (tiflags & TH_RST) 900: goto drop; 901: if (tp->t_inpcb->inp_socket->so_options & SO_DEBUG) 902: tcp_trace(TA_RESPOND, ostate, tp, &tcp_saveti, 0); 903: tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); 904: return; 905: 906: dropwithreset: 907: if (om) { 908: (void) m_free(om); 909: om = 0; 910: } 911: /* 912: * Generate a RST, dropping incoming segment. 913: * Make ACK acceptable to originator of segment. 914: * Don't bother to respond if destination was broadcast. 915: */ 916: if ((tiflags & TH_RST) || in_broadcast(ti->ti_dst)) 917: goto drop; 918: if (tiflags & TH_ACK) 919: tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); 920: else { 921: if (tiflags & TH_SYN) 922: ti->ti_len++; 923: tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, 924: TH_RST|TH_ACK); 925: } 926: /* destroy temporarily created socket */ 927: if (dropsocket) 928: (void) soabort(so); 929: return; 930: 931: drop: 932: if (om) 933: (void) m_free(om); 934: /* 935: * Drop space held by incoming segment and return. 936: */ 937: if (tp && (tp->t_inpcb->inp_socket->so_options & SO_DEBUG)) 938: tcp_trace(TA_DROP, ostate, tp, &tcp_saveti, 0); 939: m_freem(m); 940: /* destroy temporarily created socket */ 941: if (dropsocket) 942: (void) soabort(so); 943: return; 944: } 945: 946: tcp_dooptions(tp, om, ti) 947: struct tcpcb *tp; 948: struct mbuf *om; 949: struct tcpiphdr *ti; 950: { 951: register u_char *cp; 952: int opt, optlen, cnt; 953: 954: cp = mtod(om, u_char *); 955: cnt = om->m_len; 956: for (; cnt > 0; cnt -= optlen, cp += optlen) { 957: opt = cp[0]; 958: if (opt == TCPOPT_EOL) 959: break; 960: if (opt == TCPOPT_NOP) 961: optlen = 1; 962: else { 963: optlen = cp[1]; 964: if (optlen <= 0) 965: break; 966: } 967: switch (opt) { 968: 969: default: 970: break; 971: 972: case TCPOPT_MAXSEG: 973: if (optlen != 4) 974: continue; 975: if (!(ti->ti_flags & TH_SYN)) 976: continue; 977: tp->t_maxseg = *(u_short *)(cp + 2); 978: tp->t_maxseg = ntohs((u_short)tp->t_maxseg); 979: tp->t_maxseg = MIN(tp->t_maxseg, tcp_mss(tp)); 980: break; 981: } 982: } 983: (void) m_free(om); 984: } 985: 986: /* 987: * Pull out of band byte out of a segment so 988: * it doesn't appear in the user's data queue. 989: * It is still reflected in the segment length for 990: * sequencing purposes. 991: */ 992: tcp_pulloutofband(so, ti) 993: struct socket *so; 994: struct tcpiphdr *ti; 995: { 996: register struct mbuf *m; 997: int cnt = ti->ti_urp - 1; 998: 999: m = dtom(ti); 1000: while (cnt >= 0) { 1001: if (m->m_len > cnt) { 1002: char *cp = mtod(m, caddr_t) + cnt; 1003: struct tcpcb *tp = sototcpcb(so); 1004: 1005: tp->t_iobc = *cp; 1006: tp->t_oobflags |= TCPOOB_HAVEDATA; 1007: bcopy(cp+1, cp, (unsigned)(m->m_len - cnt - 1)); 1008: m->m_len--; 1009: return; 1010: } 1011: cnt -= m->m_len; 1012: m = m->m_next; 1013: if (m == 0) 1014: break; 1015: } 1016: panic("tcp_pulloutofband"); 1017: } 1018: 1019: /* 1020: * Determine a reasonable value for maxseg size. 1021: * If the route is known, use one that can be handled 1022: * on the given interface without forcing IP to fragment. 1023: * If bigger than a page (CLBYTES), round down to nearest pagesize 1024: * to utilize pagesize mbufs. 1025: * If interface pointer is unavailable, or the destination isn't local, 1026: * use a conservative size (512 or the default IP max size, but no more 1027: * than the mtu of the interface through which we route), 1028: * as we can't discover anything about intervening gateways or networks. 1029: * 1030: * This is ugly, and doesn't belong at this level, but has to happen somehow. 1031: */ 1032: tcp_mss(tp) 1033: register struct tcpcb *tp; 1034: { 1035: struct route *ro; 1036: struct ifnet *ifp; 1037: int mss; 1038: struct inpcb *inp; 1039: 1040: inp = tp->t_inpcb; 1041: ro = &inp->inp_route; 1042: if ((ro->ro_rt == (struct rtentry *)0) || 1043: (ifp = ro->ro_rt->rt_ifp) == (struct ifnet *)0) { 1044: /* No route yet, so try to acquire one */ 1045: if (inp->inp_faddr.s_addr != INADDR_ANY) { 1046: ro->ro_dst.sa_family = AF_INET; 1047: ((struct sockaddr_in *) &ro->ro_dst)->sin_addr = 1048: inp->inp_faddr; 1049: rtalloc(ro); 1050: } 1051: if ((ro->ro_rt == 0) || (ifp = ro->ro_rt->rt_ifp) == 0) 1052: return (TCP_MSS); 1053: } 1054: 1055: mss = ifp->if_mtu - sizeof(struct tcpiphdr); 1056: #if (CLBYTES & (CLBYTES - 1)) == 0 1057: if (mss > CLBYTES) 1058: mss &= ~(CLBYTES-1); 1059: #else 1060: if (mss > CLBYTES) 1061: mss = mss / CLBYTES * CLBYTES; 1062: #endif 1063: if (in_localaddr(inp->inp_faddr)) 1064: return (mss); 1065: return (MIN(mss, TCP_MSS)); 1066: }
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