just check the uplink

bash/ethlnkchk

@@ -0,0 +1,26 @@
+#!/bin/bash
+
+if [ "$( /usr/bin/id --user )" -ne 0 ] ; then
+  printf "U have to be root\\!"
+  exit 1
+fi
+
+if [ ! -x "/sbin/ethtool" ] ; then
+  printf "U have to install ethtool first\\!"
+  exit 2
+fi
+
+ETH="eth0"
+CNT=0
+
+while true ; do
+  if ! /sbin/ethtool "${ETH}" 2>/dev/null | /bin/grep "Link detected: yes" 1>/dev/null ; then
+    (( CNT++ ))
+  else
+    CNT=0
+  fi
+  if [ "${CNT}" -gt 6 ] ; then /home/pi/bin/sesame close ; fi
+  sleep 6
+done
+
+exit 0