/* tcp_input.c 6.1 83/07/29 */ #include "tcp.h" #if NTCP > 0 #include "../h/param.h" #include "../h/systm.h" #include "../h/stream.h" #include "../h/inet/mbuf.h" #include "../h/inet/in.h" #include "../h/inet/ip.h" #include "../h/inet/ip_var.h" #include "../h/inet/tcp.h" #include "../h/inet/tcp_fsm.h" #include "../h/inet/tcp_seq.h" #include "../h/inet/tcp_timer.h" #include "../h/inet/tcp_var.h" #include "../h/inet/tcpip.h" #include "../h/inet/socket.h" int tcpprintfs = 0; int itcpcksum = 0; int tcp_dropcode = 0; extern tcpnodelack; extern int tcp_maxseg; /* * TCP input routine, follows pages 65-76 of the * protocol specification dated September, 1981 very closely. */ tcp_input(m0) struct mbuf *m0; { register struct tcpiphdr *ti; register struct mbuf *m; struct mbuf *om = 0; int len, tlen, off; register struct tcpcb *tp = 0; register struct socket *so; register int tiflags; int todrop, acked; int dropsocket = 0; /* * Get IP and TCP header together in first mbuf. * Note: IP leaves IP header in first mbuf. */ m = m0; ti = mtod(m, struct tcpiphdr *); if (((struct ip *)ti)->ip_hl > (sizeof (struct ip) >> 2)) ip_stripoptions((struct ip *)ti, (struct mbuf *)0); if (BLEN(m) < sizeof (struct tcpiphdr)) { if ((m = m_pullup(m, sizeof (struct tcpiphdr))) == 0) { tcpstat.tcps_hdrops++; return; } ti = mtod(m, struct tcpiphdr *); } /* * Checksum extended TCP header and data. */ tlen = ((struct ip *)ti)->ip_len; len = sizeof (struct ip) + tlen; ti->ti_src = htonl(ti->ti_src); ti->ti_dst = htonl(ti->ti_dst); ti->ti_len = (u_short)tlen; ti->ti_len = htons((u_short)ti->ti_len); ti->ti_next = ti->ti_prev = 0; ti->ti_x1 = 0; tcp_debug(ti, 0); if (itcpcksum) { if (ti->ti_sum = in_cksum(m, len)) { if (tcpprintfs) printf("tcp sum: src %x, len %d\n", ti->ti_src, len); tcpstat.tcps_badsum++; goto drop; } } /* * Check that TCP offset makes sense, * pull out TCP options and adjust length. */ off = ti->ti_off << 2; if (off < sizeof (struct tcphdr) || off > tlen) { if (tcpprintfs) printf("tcp off: src %x off %d\n", ti->ti_src, off); tcpstat.tcps_badoff++; goto drop; } tlen -= off; ti->ti_len = tlen; if (off > sizeof (struct tcphdr)) { if ((m = m_pullup(m, sizeof (struct ip) + off)) == 0) { tcpstat.tcps_hdrops++; return; } ti = mtod(m, struct tcpiphdr *); om = m_get(M_DONTWAIT, MT_DATA); if (om == 0) goto drop; om->next = 0; om->wptr += off - sizeof (struct tcphdr); { caddr_t op = mtod(m, caddr_t) + sizeof (struct tcpiphdr); bcopy(op, mtod(om, caddr_t), (unsigned)BLEN(om)); m->wptr -= BLEN(om); bcopy(op+BLEN(om), op, (unsigned)(BLEN(m)-sizeof (struct tcpiphdr))); } } tiflags = ti->ti_flags; /* * Drop TCP and IP headers. */ m->rptr += sizeof(struct tcpiphdr); /* * Convert TCP protocol specific fields to host format. */ ti->ti_seq = ntohl(ti->ti_seq); ti->ti_ack = ntohl(ti->ti_ack); ti->ti_win = ntohs(ti->ti_win); ti->ti_urp = ntohs(ti->ti_urp); ti->ti_src = ntohl(ti->ti_src); ti->ti_dst = ntohl(ti->ti_dst); ti->ti_sport = ntohs(ti->ti_sport); ti->ti_dport = ntohs(ti->ti_dport); /* * Locate pcb for segment. * If the state is CLOSED (i.e., TCB does not exist) then * all data in the incoming segment is discarded. */ so = so_lookup(ti->ti_src, ti->ti_sport, ti->ti_dst, ti->ti_dport); if (so == 0) { tcp_dropcode = 1; goto dropwithreset; } tp = so->so_tcpcb; if(tp == 0) { tcp_dropcode = 2; goto dropwithreset; } if (so->so_options & SO_ACCEPTCONN) { so = sonewconn(so); if (so == 0) goto drop; /* * This is ugly, but .... * * Mark socket as temporary until we're * committed to keeping it. The code at * ``drop'' and ``dropwithreset'' check the * flag dropsocket to see if the temporary * socket created here should be discarded. * We mark the socket as discardable until * we're committed to it below in TCPS_LISTEN. */ dropsocket++; so->so_laddr = ti->ti_dst; so->so_lport = ti->ti_dport; so->so_faddr = ti->ti_src; so->so_fport = ti->ti_sport; tp = sototcpcb(so); tp->t_state = TCPS_LISTEN; } /* * If the RST bit is set examine the state: * SYN_RECEIVED STATE: * If passive open, return to LISTEN state. * If active open, inform user that connection was refused. * ESTABLISHED, FIN_WAIT_1, FIN_WAIT2, CLOSE_WAIT STATES: * Inform user that connection was reset, and close tcb. * CLOSING, LAST_ACK, TIME_WAIT STATES * Close the tcb. */ if (tiflags&TH_RST) switch (tp->t_state) { case TCPS_LISTEN: goto drop; case TCPS_SYN_RECEIVED: tp = tcp_drop(tp); goto drop; case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: tp = tcp_drop(tp); goto drop; case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: tp = tcp_close(tp); goto drop; } /* * Segment received on connection. * Reset idle time and keep-alive timer. */ tp->t_idle = 0; tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; /* * Process options. */ if (om) { tcp_dooptions(tp, om); om = 0; } /* * Calculate amount of space in receive window, * and then do TCP input processing. */ tp->rcv_wnd = sbrcvspace(so); if (tp->rcv_wnd < 0) tp->rcv_wnd = 0; switch (tp->t_state) { /* * If the state is LISTEN then ignore segment if it contains an RST. * If the segment contains an ACK then it is bad and send a RST. * If it does not contain a SYN then it is not interesting; drop it. * Otherwise initialize tp->rcv_nxt, and tp->irs, select an initial * tp->iss, and send a segment: * <SEQ=ISS><ACK=RCV_NXT><CTL=SYN,ACK> * Also initialize tp->snd_nxt to tp->iss+1 and tp->snd_una to tp->iss. * Fill in remote peer address fields if not previously specified. * Enter SYN_RECEIVED state, and process any other fields of this * segment in this state. */ case TCPS_LISTEN: { if (tiflags & TH_ACK) { tcp_dropcode = 3; goto dropwithreset; } if ((tiflags & TH_SYN) == 0) goto drop; tp->t_template = tcp_template(tp); if (tp->t_template == 0) { tp = 0; goto drop; } tp->iss = tcp_iss; tcp_iss += TCP_ISSINCR/2; tp->irs = ti->ti_seq; tcp_sendseqinit(tp); tcp_rcvseqinit(tp); tp->t_state = TCPS_SYN_RECEIVED; tp->t_timer[TCPT_KEEP] = TCPTV_KEEP; dropsocket = 0; /* committed to socket */ goto trimthenstep6; } /* * If the state is SYN_SENT: * if seg contains an ACK, but not for our SYN, drop the input. * if seg contains a RST, then drop the connection. * if seg does not contain SYN, then drop it. * Otherwise this is an acceptable SYN segment * initialize tp->rcv_nxt and tp->irs * if seg contains ack then advance tp->snd_una * if SYN has been acked change to ESTABLISHED else SYN_RCVD state * arrange for segment to be acked (eventually) * continue processing rest of data/controls, beginning with URG */ case TCPS_SYN_SENT: if ((tiflags & TH_ACK) && /* this should be SEQ_LT; is SEQ_LEQ for BBN vax TCP only */ (SEQ_LT(ti->ti_ack, tp->iss) || SEQ_GT(ti->ti_ack, tp->snd_max))) { tcp_dropcode = 4; goto dropwithreset; } if (tiflags & TH_RST) { if (tiflags & TH_ACK) tp = tcp_drop(tp); goto drop; } if ((tiflags & TH_SYN) == 0) goto drop; tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; tp->t_timer[TCPT_REXMT] = 0; tp->irs = ti->ti_seq; tcp_rcvseqinit(tp); tp->t_flags |= TF_ACKNOW; if (SEQ_GT(tp->snd_una, tp->iss)) { soisconnected(so); tp->t_state = TCPS_ESTABLISHED; (void) tcp_reass(tp, (struct tcpiphdr *)0); } else tp->t_state = TCPS_SYN_RECEIVED; goto trimthenstep6; trimthenstep6: /* * Advance ti->ti_seq to correspond to first data byte. * If data, trim to stay within window, * dropping FIN if necessary. */ ti->ti_seq++; if (ti->ti_len > tp->rcv_wnd) { todrop = ti->ti_len - tp->rcv_wnd; m_adj(m, -todrop); ti->ti_len = tp->rcv_wnd; ti->ti_flags &= ~TH_FIN; } tp->snd_wl1 = ti->ti_seq - 1; goto step6; } /* * States other than LISTEN or SYN_SENT. * First check that at least some bytes of segment are within * receive window. */ if (tp->rcv_wnd == 0) { /* * If window is closed can only take segments at * window edge, and have to drop data and PUSH from * incoming segments. */ if (tp->rcv_nxt != ti->ti_seq) goto dropafterack; if (ti->ti_len > 0) { m_adj(m, ti->ti_len); ti->ti_len = 0; ti->ti_flags &= ~(TH_PUSH|TH_FIN); } } else { /* * smb proofing; this disables most of the funtionality * of the reassembly queue. Doesn't seem to hurt performance * under normal circs. */ if(ti->ti_seq > tp->rcv_nxt) goto dropafterack; /* * If segment begins before rcv_nxt, drop leading * data (and SYN); if nothing left, just ack. */ todrop = tp->rcv_nxt - ti->ti_seq; if (todrop > 0) { if (tiflags & TH_SYN) { tiflags &= ~TH_SYN; ti->ti_flags &= ~TH_SYN; ti->ti_seq++; if (ti->ti_urp > 1) ti->ti_urp--; else tiflags &= ~TH_URG; todrop--; } if (todrop > ti->ti_len || todrop == ti->ti_len && (tiflags&TH_FIN) == 0) goto dropafterack; m_adj(m, todrop); ti->ti_seq += todrop; ti->ti_len -= todrop; if (ti->ti_urp > todrop) ti->ti_urp -= todrop; else { tiflags &= ~TH_URG; ti->ti_flags &= ~TH_URG; ti->ti_urp = 0; } } /* * If segment ends after window, drop trailing data * (and PUSH and FIN); if nothing left, just ACK. */ todrop = (ti->ti_seq+ti->ti_len) - (tp->rcv_nxt+tp->rcv_wnd); if (todrop > 0) { if (todrop >= ti->ti_len) goto dropafterack; m_adj(m, -todrop); ti->ti_len -= todrop; ti->ti_flags &= ~(TH_PUSH|TH_FIN); } } /* * If data is received on a connection after the * user processes are gone, then RST the other end. */ if ((so->so_state & SS_OPEN)==0 && tp->t_state > TCPS_CLOSE_WAIT && tlen) { tp = tcp_close(tp); tcp_dropcode = 5; goto dropwithreset; } /* * If a SYN is in the window, then this is an * error and we send an RST and drop the connection. */ if (tiflags & TH_SYN) { tp = tcp_drop(tp); tcp_dropcode = 6; goto dropwithreset; } /* * If the ACK bit is off we drop the segment and return. */ if ((tiflags & TH_ACK) == 0) goto drop; /* * Ack processing. */ switch (tp->t_state) { /* * In SYN_RECEIVED state if the ack ACKs our SYN then enter * ESTABLISHED state and continue processing, othewise * send an RST. */ case TCPS_SYN_RECEIVED: if (SEQ_GT(tp->snd_una, ti->ti_ack) || SEQ_GT(ti->ti_ack, tp->snd_max)) { tcp_dropcode = 7; goto dropwithreset; } tp->snd_una++; /* SYN acked */ if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; tp->t_timer[TCPT_REXMT] = 0; soisconnected(so); tp->t_state = TCPS_ESTABLISHED; (void) tcp_reass(tp, (struct tcpiphdr *)0); tp->snd_wl1 = ti->ti_seq - 1; /* fall into ... */ /* * In ESTABLISHED state: drop duplicate ACKs; ACK out of range * ACKs. If the ack is in the range * tp->snd_una < ti->ti_ack <= tp->snd_max * then advance tp->snd_una to ti->ti_ack and drop * data from the retransmission queue. If this ACK reflects * more up to date window information we update our window information. */ case TCPS_ESTABLISHED: case TCPS_FIN_WAIT_1: case TCPS_FIN_WAIT_2: case TCPS_CLOSE_WAIT: case TCPS_CLOSING: case TCPS_LAST_ACK: case TCPS_TIME_WAIT: #define ourfinisacked (acked > 0) if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) break; if (SEQ_GT(ti->ti_ack, tp->snd_max)) goto dropafterack; acked = ti->ti_ack - tp->snd_una; /* * If transmit timer is running and timed sequence * number was acked, update smoothed round trip time. */ if (tp->t_rtt && SEQ_GT(ti->ti_ack, tp->t_rtseq)) { if (tp->t_srtt == 0) tp->t_srtt = tp->t_rtt; else tp->t_srtt = tcp_alpha * tp->t_srtt + (1 - tcp_alpha) * tp->t_rtt; tp->t_rtt = 0; } if (ti->ti_ack == tp->snd_max) tp->t_timer[TCPT_REXMT] = 0; else { TCPT_RANGESET(tp->t_timer[TCPT_REXMT], tcp_beta * tp->t_srtt, TCPTV_MIN, TCPTV_MAX); tp->t_rtt = 1; tp->t_rxtshift = 0; } if (acked > sosndcc(so)) { tp->snd_wnd -= sosndcc(so); sbsnddrop(so, sosndcc(so)); } else { sbsnddrop(so, acked); tp->snd_wnd -= acked; acked = 0; } tp->snd_una = ti->ti_ack; if (SEQ_LT(tp->snd_nxt, tp->snd_una)) tp->snd_nxt = tp->snd_una; switch (tp->t_state) { /* * In FIN_WAIT_1 STATE in addition to the processing * for the ESTABLISHED state if our FIN is now acknowledged * then enter FIN_WAIT_2. */ case TCPS_FIN_WAIT_1: if (ourfinisacked) { /* * If we can't receive any more * data, then closing user can proceed. */ tp->t_state = TCPS_FIN_WAIT_2; } break; /* * In CLOSING STATE in addition to the processing for * the ESTABLISHED state if the ACK acknowledges our FIN * then enter the TIME-WAIT state, otherwise ignore * the segment. */ case TCPS_CLOSING: if (ourfinisacked) { tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; soisdisconnected(so); } break; /* * The only thing that can arrive in LAST_ACK state * is an acknowledgment of our FIN. If our FIN is now * acknowledged, delete the TCB, enter the closed state * and return. */ case TCPS_LAST_ACK: if (ourfinisacked) tp = tcp_close(tp); goto drop; /* * In TIME_WAIT state the only thing that should arrive * is a retransmission of the remote FIN. Acknowledge * it and restart the finack timer. */ case TCPS_TIME_WAIT: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; goto dropafterack; } #undef ourfinisacked } step6: /* * Update window information. */ if (SEQ_LT(tp->snd_wl1, ti->ti_seq) || tp->snd_wl1 == ti->ti_seq && (SEQ_LT(tp->snd_wl2, ti->ti_ack) || tp->snd_wl2 == ti->ti_ack && ti->ti_win > tp->snd_wnd)) { tp->snd_wnd = ti->ti_win; tp->snd_wl1 = ti->ti_seq; tp->snd_wl2 = ti->ti_ack; if (tp->snd_wnd != 0) tp->t_timer[TCPT_PERSIST] = 0; } /* * Process segments with URG. */ if ((tiflags & TH_URG) && ti->ti_urp && TCPS_HAVERCVDFIN(tp->t_state) == 0) { /* * This is a kludge, but if we receive accept * random urgent pointers, we'll crash in * soreceive. It's hard to imagine someone * actually wanting to send this much urgent data. */ if (ti->ti_urp > tp->t_maxseg) { /* XXX */ ti->ti_urp = 0; /* XXX */ tiflags &= ~TH_URG; /* XXX */ ti->ti_flags &= ~TH_URG; /* XXX */ goto badurp; /* XXX */ } /* * If this segment advances the known urgent pointer, * then mark the data stream. This should not happen * in CLOSE_WAIT, CLOSING, LAST_ACK or TIME_WAIT STATES since * a FIN has been received from the remote side. * In these states we ignore the URG. */ if (SEQ_GT(ti->ti_seq+ti->ti_urp, tp->rcv_up)) { /* M_CTL, maybe? looks like it's put in the data stream */ tp->rcv_up = ti->ti_seq + ti->ti_urp; so->so_oobmark = 0 + (tp->rcv_up - tp->rcv_nxt) - 1; if (so->so_oobmark == 0) so->so_state |= SS_RCVATMARK; sohasoutofband(so); tp->t_oobflags &= ~TCPOOB_HAVEDATA; } /* * Remove out of band data so doesn't get presented to user. * This can happen independent of advancing the URG pointer, * but if two URG's are pending at once, some out-of-band * data may creep in... ick. */ if (ti->ti_urp <= ti->ti_len) tcp_pulloutofband(so, ti); } badurp: /* XXX */ /* * Process the segment text, merging it into the TCP sequencing queue, * and arranging for acknowledgment of receipt if necessary. * This process logically involves adjusting tp->rcv_wnd as data * is presented to the user (this happens in tcp_usrreq.c, * case PRU_RCVD). If a FIN has already been received on this * connection then we just ignore the text. */ if ((ti->ti_len || (tiflags&TH_FIN)) && TCPS_HAVERCVDFIN(tp->t_state) == 0) { tiflags = tcp_reass(tp, ti); if (tcpnodelack == 0) tp->t_flags |= TF_DELACK; else tp->t_flags |= TF_ACKNOW; } else { m_freem(m); tiflags &= ~TH_FIN; } /* * If FIN is received ACK the FIN and let the user know * that the connection is closing. */ if (tiflags & TH_FIN) { if (TCPS_HAVERCVDFIN(tp->t_state) == 0) { socantrcvmore(so); tp->t_flags |= TF_ACKNOW; tp->rcv_nxt++; } switch (tp->t_state) { /* * In SYN_RECEIVED and ESTABLISHED STATES * enter the CLOSE_WAIT state. */ case TCPS_SYN_RECEIVED: tp->t_state = TCPS_CLOSE_WAIT; soisdisconnected(so); break; case TCPS_ESTABLISHED: tp->t_state = TCPS_CLOSE_WAIT; break; /* * If still in FIN_WAIT_1 STATE FIN has not been acked so * enter the CLOSING state. */ case TCPS_FIN_WAIT_1: tp->t_state = TCPS_CLOSING; break; /* * In FIN_WAIT_2 state enter the TIME_WAIT state, * starting the time-wait timer, turning off the other * standard timers. */ case TCPS_FIN_WAIT_2: tp->t_state = TCPS_TIME_WAIT; tcp_canceltimers(tp); tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; soisdisconnected(so); break; /* * In TIME_WAIT state restart the 2 MSL time_wait timer. */ case TCPS_TIME_WAIT: tp->t_timer[TCPT_2MSL] = 2 * TCPTV_MSL; break; } } /* * Return any desired output. */ (void) tcp_output(tp); return; dropafterack: /* * Generate an ACK dropping incoming segment if it occupies * sequence space, where the ACK reflects our state. */ if ((tiflags&TH_RST) || tlen == 0 && (tiflags&(TH_SYN|TH_FIN)) == 0) goto drop; tcp_respond(tp, ti, tp->rcv_nxt, tp->snd_nxt, TH_ACK); return; dropwithreset: if (om) { (void) m_free(om); om = 0; } /* * Generate a RST, dropping incoming segment. * Make ACK acceptable to originator of segment. */ if (tiflags & TH_RST) goto drop; if (tiflags & TH_ACK) tcp_respond(tp, ti, (tcp_seq)0, ti->ti_ack, TH_RST); else { if (tiflags & TH_SYN) ti->ti_len++; tcp_respond(tp, ti, ti->ti_seq+ti->ti_len, (tcp_seq)0, TH_RST|TH_ACK); } /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; drop: if (om) (void) m_free(om); /* * Drop space held by incoming segment and return. */ m_freem(m); /* destroy temporarily created socket */ if (dropsocket) (void) soabort(so); return; } tcp_dooptions(tp, om) struct tcpcb *tp; struct mbuf *om; { register u_char *cp; int opt, optlen, cnt; cp = mtod(om, u_char *); cnt = BLEN(om); for (; cnt > 0; cnt -= optlen, cp += optlen) { opt = cp[0]; if (opt == TCPOPT_EOL) break; if (opt == TCPOPT_NOP) optlen = 1; else { optlen = cp[1]; if (optlen <= 0) break; } switch (opt) { default: break; case TCPOPT_MAXSEG: if (optlen != 4) continue; tp->t_maxseg = *(u_short *)(cp + 2); tp->t_maxseg = ntohs((u_short)tp->t_maxseg); if (tp->t_maxseg > tcp_maxseg) tp->t_maxseg = tcp_maxseg; break; } } (void) m_free(om); } /* * Pull out of band byte out of a segment so * it doesn't appear in the user's data queue. * It is still reflected in the segment length for * sequencing purposes. */ tcp_pulloutofband(so, ti) struct socket *so; struct tcpiphdr *ti; { register struct mbuf *m; int cnt = ti->ti_urp - 1; m = dtom(ti); while (cnt >= 0) { if (BLEN(m) > cnt) { char *cp = mtod(m, caddr_t) + cnt; struct tcpcb *tp = sototcpcb(so); tp->t_iobc = *cp; tp->t_oobflags |= TCPOOB_HAVEDATA; bcopy(cp+1, cp, (unsigned)(BLEN(m) - cnt - 1)); m->wptr--; return; } cnt -= BLEN(m); m = m->m_next; if (m == 0) break; } panic("tcp_pulloutofband"); } /* * Insert segment ti into reassembly queue of tcp with * control block tp. Return TH_FIN if reassembly now includes * a segment with FIN. */ tcp_reass(tp, ti) register struct tcpcb *tp; register struct tcpiphdr *ti; { register struct tcpiphdr *q; struct socket *so = tp->t_socket; struct mbuf *m; int flags; /* * Call with ti==0 after become established to * force pre-ESTABLISHED data up to user socket. */ if (ti == 0) goto present; /* * Find a segment which begins after this one does. */ for (q = tp->seg_next; q != (struct tcpiphdr *)tp; q = (struct tcpiphdr *)q->ti_next) if (SEQ_GT(q->ti_seq, ti->ti_seq)) break; /* * If there is a preceding segment, it may provide some of * our data already. If so, drop the data from the incoming * segment. If it provides all of our data, drop us. */ if ((struct tcpiphdr *)q->ti_prev != (struct tcpiphdr *)tp) { register int i; q = (struct tcpiphdr *)q->ti_prev; /* conversion to int (in i) handles seq wraparound */ i = q->ti_seq + q->ti_len - ti->ti_seq; if (i > 0) { tcpstat.tcps_duplicates++; if (i >= ti->ti_len) goto drop; m_adj(dtom(ti), i); ti->ti_len -= i; ti->ti_seq += i; } q = (struct tcpiphdr *)(q->ti_next); } /* * While we overlap succeeding segments trim them or, * if they are completely covered, dequeue them. */ while (q != (struct tcpiphdr *)tp) { register int i = (ti->ti_seq + ti->ti_len) - q->ti_seq; if (i <= 0) break; tcpstat.tcps_delayed++; if (i < q->ti_len) { q->ti_seq += i; q->ti_len -= i; m_adj(dtom(q), i); break; } q = (struct tcpiphdr *)q->ti_next; m = dtom(q->ti_prev); remque(q->ti_prev); m_freem(m); } /* * Stick new segment in its place. */ insque(ti, q->ti_prev); present: /* * Present data to user, advancing rcv_nxt through * completed sequence space. */ if (TCPS_HAVERCVDSYN(tp->t_state) == 0) return (0); ti = tp->seg_next; if (ti == (struct tcpiphdr *)tp || ti->ti_seq != tp->rcv_nxt) return (0); if (tp->t_state == TCPS_SYN_RECEIVED && ti->ti_len) return (0); do { tp->rcv_nxt += ti->ti_len; flags = ti->ti_flags & TH_FIN; remque(ti); m = dtom(ti); ti = (struct tcpiphdr *)ti->ti_next; if (so->so_state & SS_OPEN) tcpdrint(m, so); else m_freem(m); } while (ti != (struct tcpiphdr *)tp && ti->ti_seq == tp->rcv_nxt); return (flags); drop: m_freem(dtom(ti)); return (0); } #endif