tcp_input.c

VxWorks BSP框架源代码包含头文件和驱动

		if ((tiflags & TH_SYN) == 0)
			goto drop;
		if (tiflags & TH_ACK) {
			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 (tiflags & TH_ACK ) {
			tcpstat.tcps_connects++;

#ifdef WV_INSTRUMENTATION
#ifdef INCLUDE_WVNET    /* WV_NET_INFO event */
            WV_NET_PORTIN_EVENT_3 (NET_AUX_EVENT, WV_NET_INFO, 30, 12,
                                   ti->ti_sport, ti->ti_dport,
                                   WV_NETEVENT_TCPIN_CONNECT, WV_NET_RECV, 
                                   so->so_fd, tp->snd_nxt, tp->rcv_nxt)
#endif  /* INCLUDE_WVNET */
#endif

			soisconnected(so);
			tp->t_state = TCPS_ESTABLISHED;
			/* Do window scaling on this connection? */
			if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
				(TF_RCVD_SCALE|TF_REQ_SCALE)) {
				tp->snd_scale = tp->requested_s_scale;
				tp->rcv_scale = tp->request_r_scale;
			}
			(void) tcp_reass(tp, (struct tcpiphdr *)0,
				(struct mbuf *)0);
			/*
			 * if we didn't have to retransmit the SYN,
			 * use its rtt as our initial srtt & rtt var.
			 */
			if (tp->t_rtt)
				tcp_xmit_timer(tp, tp->t_rtt);
		} else
			tp->t_state = TCPS_SYN_RECEIVED;

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;
			tiflags &= ~TH_FIN;
			tcpstat.tcps_rcvpackafterwin++;
			tcpstat.tcps_rcvbyteafterwin += todrop;
		}
		tp->snd_wl1 = ti->ti_seq - 1;
		tp->rcv_up = ti->ti_seq;
		goto step6;
	}

	/*
	 * States other than LISTEN or SYN_SENT.
	 * First check timestamp, if present.
	 * Then check that at least some bytes of segment are within 
	 * receive window.  If segment begins before rcv_nxt,
	 * drop leading data (and SYN); if nothing left, just ack.
	 * 
	 * RFC 1323 PAWS: If we have a timestamp reply on this segment
	 * and it's less than ts_recent, drop it.
	 */
	if (ts_present && (tiflags & TH_RST) == 0 && tp->ts_recent &&
	    TSTMP_LT(ts_val, tp->ts_recent)) {

		/* Check to see if ts_recent is over 24 days old.  */
		if ((int)(tcp_now - tp->ts_recent_age) > TCP_PAWS_IDLE) {
			/*
			 * Invalidate ts_recent.  If this segment updates
			 * ts_recent, the age will be reset later and ts_recent
			 * will get a valid value.  If it does not, setting
			 * ts_recent to zero will at least satisfy the
			 * requirement that zero be placed in the timestamp
			 * echo reply when ts_recent isn't valid.  The
			 * age isn't reset until we get a valid ts_recent
			 * because we don't want out-of-order segments to be
			 * dropped when ts_recent is old.
			 */
			tp->ts_recent = 0;
		} else {
			tcpstat.tcps_rcvduppack++;
			tcpstat.tcps_rcvdupbyte += ti->ti_len;
			tcpstat.tcps_pawsdrop++;
			goto dropafterack;
		}
	}

	todrop = tp->rcv_nxt - ti->ti_seq;
	if (todrop > 0) {
		if (tiflags & TH_SYN) {
			tiflags &= ~TH_SYN;
			ti->ti_seq++;
			if (ti->ti_urp > 1) 
				ti->ti_urp--;
			else
				tiflags &= ~TH_URG;
			todrop--;
		}
#if 0  /* simultaneous open bug  */              
		if (todrop >= ti->ti_len) {
			tcpstat.tcps_rcvduppack++;
			tcpstat.tcps_rcvdupbyte += ti->ti_len;
			/*
			 * If segment is just one to the left of the window,
			 * check two special cases:
			 * 1. Don't toss RST in response to 4.2-style keepalive.
			 * 2. If the only thing to drop is a FIN, we can drop
			 *    it, but check the ACK or we will get into FIN
			 *    wars if our FINs crossed (both CLOSING).
			 * In either case, send ACK to resynchronize,
			 * but keep on processing for RST or ACK.
			 */
			if ((tiflags & TH_FIN && todrop == ti->ti_len + 1)
#ifdef TCP_COMPAT_42
			  || (tiflags & TH_RST && ti->ti_seq == tp->rcv_nxt - 1)
#endif
			   ) {
				todrop = ti->ti_len;
				tiflags &= ~TH_FIN;
			} else {
				/*
				 * Handle the case when a bound socket connects
				 * to itself. Allow packets with a SYN and
				 * an ACK to continue with the processing.
				 */
				if (todrop != 0 || (tiflags & TH_ACK) == 0)
					goto dropafterack;
			}
			tp->t_flags |= TF_ACKNOW;
		} else {
			tcpstat.tcps_rcvpartduppack++;
			tcpstat.tcps_rcvpartdupbyte += todrop;
		}
#else /* XXX  simultaneous open bug fix Steven vol II sec 28.8 fig 28.30 */
                if (todrop > ti->ti_len ||
                    (todrop == ti->ti_len && (tiflags & TH_FIN) == 0)) {

                    /*
                     * Any valid Fin must be to the left of the window.
                     * At this point the FIN must be a duplicate or
                     * out of sequence; drop it.
                     */
                     tiflags &= ~TH_FIN;

                    /*
                     * Send an ACK to resynchronize and drop any data.
                     * But keep on processing for RST or ACK.
                     */
                    tp->t_flags |= TF_ACKNOW;
                    todrop = ti->ti_len;
                }
                tcpstat.tcps_rcvdupbyte += todrop;
                tcpstat.tcps_rcvduppack++;
#endif /* simultaneous open bug fix */                   
		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_urp = 0;
		}
	}

	/*
	 * If new data are received on a connection after the
	 * user processes are gone, then RST the other end.
	 */
	if ((so->so_state & SS_NOFDREF) &&
	    tp->t_state > TCPS_CLOSE_WAIT && ti->ti_len) {
		tp = tcp_close(tp);
		tcpstat.tcps_rcvafterclose++;

#ifdef WV_INSTRUMENTATION
#ifdef INCLUDE_WVNET    /* WV_NET_INFO event */
        WV_NET_PORTIN_EVENT_3 (NET_CORE_EVENT, WV_NET_INFO, 31, 13,
                               ti->ti_sport, ti->ti_dport,
                               WV_NETEVENT_TCPIN_DATACLOSED, WV_NET_RECV, 
                               so->so_fd, ti->ti_seq, ti->ti_len)
#endif  /* INCLUDE_WVNET */
#endif

		goto dropwithreset;
	}

	/*
	 * 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) {
		tcpstat.tcps_rcvpackafterwin++;
		if (todrop >= ti->ti_len) {
			tcpstat.tcps_rcvbyteafterwin += ti->ti_len;
			/*
			 * If a new connection request is received
			 * while in TIME_WAIT, drop the old connection
			 * and start over if the sequence numbers
			 * are above the previous ones.
			 */
			if (tiflags & TH_SYN &&
			    tp->t_state == TCPS_TIME_WAIT &&
			    SEQ_GT(ti->ti_seq, tp->rcv_nxt)) {
				iss = tp->snd_nxt + TCP_ISSINCR;
				tp = tcp_close(tp);
				goto findpcb;
			}
			/*
			 * If window is closed can only take segments at
			 * window edge, and have to drop data and PUSH from
			 * incoming segments.  Continue processing, but
			 * remember to ack.  Otherwise, drop segment
			 * and ack.
			 */
			if (tp->rcv_wnd == 0 && ti->ti_seq == tp->rcv_nxt) {
				tp->t_flags |= TF_ACKNOW;
				tcpstat.tcps_rcvwinprobe++;
			} else
				goto dropafterack;
		} else
			tcpstat.tcps_rcvbyteafterwin += todrop;
		m_adj(m, -todrop);
		ti->ti_len -= todrop;
		tiflags &= ~(TH_PUSH|TH_FIN);
	}

	/*
	 * If last ACK falls within this segment's sequence numbers,
	 * record its timestamp.
	 */
	if (ts_present && TSTMP_GEQ(ts_val, tp->ts_recent) &&
            SEQ_LEQ(ti->ti_seq, tp->last_ack_sent)) {
		tp->ts_recent_age = tcp_now;
		tp->ts_recent = ts_val;
	}

	/*
	 * 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_SYN_RECEIVED:
		so->so_error = ECONNREFUSED;
		goto close;

	case TCPS_ESTABLISHED:
	case TCPS_FIN_WAIT_1:
	case TCPS_FIN_WAIT_2:
	case TCPS_CLOSE_WAIT:
		so->so_error = ECONNRESET;
	close:
#ifdef WV_INSTRUMENTATION
#ifdef INCLUDE_WVNET    /* WV_NET_INFO event */
        WV_NET_PORTIN_EVENT_1 (NET_AUX_EVENT, WV_NET_INFO, 32, 14,
                               ti->ti_sport, ti->ti_dport,
                               WV_NETEVENT_TCPIN_RESET, WV_NET_RECV, 
                               so->so_fd)
#endif  /* INCLUDE_WVNET */
#endif

		tp->t_state = TCPS_CLOSED;
		tcpstat.tcps_drops++;
		tp = tcp_close(tp);
		goto drop;

	case TCPS_CLOSING:
	case TCPS_LAST_ACK:
	case TCPS_TIME_WAIT:
		tp = tcp_close(tp);
		goto drop;
	}

	/*
	 * 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) {
#ifdef WV_INSTRUMENTATION
#ifdef INCLUDE_WVNET    /* WV_NET_WARNING event */
        WV_NET_PORTIN_EVENT_1 (NET_CORE_EVENT, WV_NET_WARNING, 12, 5,
                               ti->ti_sport, ti->ti_dport,
                               WV_NETEVENT_TCPIN_BADSYNC, WV_NET_RECV, 
                               so->so_fd)
#endif  /* INCLUDE_WVNET */
#endif

		tp = tcp_drop(tp, ECONNRESET);
		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, otherwise
	 * send an RST.
	 */
	case TCPS_SYN_RECEIVED:
		if (SEQ_GT(tp->snd_una, ti->ti_ack) ||
		    SEQ_GT(ti->ti_ack, tp->snd_max))
			goto dropwithreset;

#ifdef WV_INSTRUMENTATION
#ifdef INCLUDE_WVNET    /* WV_NET_INFO event */
            WV_NET_PORTIN_EVENT_3 (NET_AUX_EVENT, WV_NET_INFO, 30, 12,
                                   ti->ti_sport, ti->ti_dport,
                                   WV_NETEVENT_TCPIN_CONNECT, WV_NET_RECV, 
                                   so->so_fd, tp->snd_nxt, tp->rcv_nxt)
#endif  /* INCLUDE_WVNET */
#endif

		tcpstat.tcps_connects++;
		soisconnected(so);
		tp->t_state = TCPS_ESTABLISHED;
		/* Do window scaling? */
		if ((tp->t_flags & (TF_RCVD_SCALE|TF_REQ_SCALE)) ==
			(TF_RCVD_SCALE|TF_REQ_SCALE)) {
			tp->snd_scale = tp->requested_s_scale;
			tp->rcv_scale = tp->request_r_scale;
		}
		(void) tcp_reass(tp, (struct tcpiphdr *)0, (struct mbuf *)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:

		if (SEQ_LEQ(ti->ti_ack, tp->snd_una)) {
			if (ti->ti_len == 0 && tiwin == tp->snd_wnd) {
				tcpstat.tcps_rcvdupack++;
				/*
				 * If we have outstanding data (other than
				 * a window probe), this is a completely
				 * duplicate ack (ie, window info didn't
				 * change), the ack is the biggest we've
				 * seen and we've seen exactly our rexmt
				 * threshhold of them, assume a packet
				 * has been dropped and retransmit it.
				 * Kludge snd_nxt & the congestion
				 * window so we send only this one
				 * packet.
				 *
				 * We know we're losing at the current
				 * window size so do congestion avoidance
				 * (set ssthresh to half the current window
				 * and pull our congestion window back to
				 * the new ssthresh).
				 *
				 * Dup acks mean that packets have left the
				 * network (they're now cached at the receiver) 
				 * so bump cwnd by the amount in the receiver
				 * to keep a constant cwnd packets in the
				 * network.
				 */
				if (tp->t_timer[TCPT_REXMT] == 0 ||
				    ti->ti_ack != tp->snd_una)
					tp->t_dupacks = 0;
				else if (++tp->t_dupacks == tcprexmtthresh) {
					tcp_seq onxt = tp->snd_nxt;
					u_int win =
					    min(tp->snd_wnd, tp->snd_cwnd) / 2 /
						tp->t_maxseg;

					if (win < 2)
						win = 2;
					tp->snd_ssthresh = win * tp->t_maxseg;
					tp->t_timer[TCPT_REXMT] = 0;
					tp->t_rtt = 0;
					tp->snd_nxt = ti->ti_ack;
					tp->snd_cwnd = tp->t_maxseg;

#ifdef WV_INSTRUMENTATION
#ifdef INCLUDE_WVNET    /* WV_NET_WARNING event */
            WV_NET_PORTOUT_EVENT_2 (NET_CORE_EVENT, WV_NET_WARNING, 13, 6,
                              tp->t_inpcb->inp_lport, tp->t_inpcb->inp_fport,
                                   WV_NETEVENT_TCPIN_SENDFAIL, WV_NET_RECV, 
                                   so->so_fd, tp->t_dupacks)
#endif  /* INCLUDE_WVNET */
#endif