+
+/*
+ * Time to shut down the link because there is nothing out there.
+ */
+
+static
+void LcpLinkFailure (f)
+ fsm *f;
+{
+ if (f->state == OPENED) {
+ syslog(LOG_INFO, "No response to %d echo-requests", lcp_echos_pending);
+ syslog(LOG_NOTICE, "Serial link appears to be disconnected.");
+ lcp_close(f->unit, "Peer not responding");
+ }
+}
+
+/*
+ * Timer expired for the LCP echo requests from this process.
+ */
+
+static void
+LcpEchoCheck (f)
+ fsm *f;
+{
+ LcpSendEchoRequest (f);
+
+ /*
+ * Start the timer for the next interval.
+ */
+ assert (lcp_echo_timer_running==0);
+ TIMEOUT (LcpEchoTimeout, f, lcp_echo_interval);
+ lcp_echo_timer_running = 1;
+}
+
+/*
+ * LcpEchoTimeout - Timer expired on the LCP echo
+ */
+
+static void
+LcpEchoTimeout (arg)
+ void *arg;
+{
+ if (lcp_echo_timer_running != 0) {
+ lcp_echo_timer_running = 0;
+ LcpEchoCheck ((fsm *) arg);
+ }
+}
+
+/*
+ * LcpEchoReply - LCP has received a reply to the echo
+ */
+
+static void
+lcp_received_echo_reply (f, id, inp, len)
+ fsm *f;
+ int id; u_char *inp; int len;
+{
+ u_int32_t magic;
+
+ /* Check the magic number - don't count replies from ourselves. */
+ if (len < 4) {
+ syslog(LOG_DEBUG, "lcp: received short Echo-Reply, length %d", len);
+ return;
+ }
+ GETLONG(magic, inp);
+ if (lcp_gotoptions[f->unit].neg_magicnumber
+ && magic == lcp_gotoptions[f->unit].magicnumber) {
+ syslog(LOG_WARNING, "appear to have received our own echo-reply!");
+ return;
+ }
+
+ /* Reset the number of outstanding echo frames */
+ lcp_echos_pending = 0;
+}
+
+/*
+ * LcpSendEchoRequest - Send an echo request frame to the peer
+ */
+
+static void
+LcpSendEchoRequest (f)
+ fsm *f;
+{
+ u_int32_t lcp_magic;
+ u_char pkt[4], *pktp;
+
+ /*
+ * Detect the failure of the peer at this point.
+ */
+ if (lcp_echo_fails != 0) {
+ if (lcp_echos_pending >= lcp_echo_fails) {
+ LcpLinkFailure(f);
+ lcp_echos_pending = 0;
+ }
+ }
+
+ /*
+ * Make and send the echo request frame.
+ */
+ if (f->state == OPENED) {
+ lcp_magic = lcp_gotoptions[f->unit].magicnumber;
+ pktp = pkt;
+ PUTLONG(lcp_magic, pktp);
+ fsm_sdata(f, ECHOREQ, lcp_echo_number++ & 0xFF, pkt, pktp - pkt);
+ ++lcp_echos_pending;
+ }
+}
+
+/*
+ * lcp_echo_lowerup - Start the timer for the LCP frame
+ */
+
+static void
+lcp_echo_lowerup (unit)
+ int unit;
+{
+ fsm *f = &lcp_fsm[unit];
+
+ /* Clear the parameters for generating echo frames */
+ lcp_echos_pending = 0;
+ lcp_echo_number = 0;
+ lcp_echo_timer_running = 0;
+
+ /* If a timeout interval is specified then start the timer */
+ if (lcp_echo_interval != 0)
+ LcpEchoCheck (f);
+}
+
+/*
+ * lcp_echo_lowerdown - Stop the timer for the LCP frame
+ */
+
+static void
+lcp_echo_lowerdown (unit)
+ int unit;
+{
+ fsm *f = &lcp_fsm[unit];
+
+ if (lcp_echo_timer_running != 0) {
+ UNTIMEOUT (LcpEchoTimeout, f);
+ lcp_echo_timer_running = 0;
+ }
+}