bundles/unbound: automatically restart unbound if dns resolution fails for more than five minutes

bundles/unbound/files/unbound-auto-restart

@@ -0,0 +1,25 @@
+#!/bin/bash
+
+now="$(date +%s)"
+
+resolved="$(dig +short kunbox.net)"
+
+if [[ -n "$resolved" ]]
+then
+    echo "$now" > /var/tmp/unbound_last_resolved
+    exit 0
+fi
+
+last_resolved="$(cat /var/tmp/unbound_last_resolved)"
+five_min_ago="$(expr $now - 300)"
+
+if [[ "$last_resolved" -lt "$five_min_ago" ]]
+then
+    systemctl restart unbound
+
+    # Write "in 25 minutes" timestamp to /var/tmp/unbound_last_resolved.
+    # If resolving gets fixed by the restart, this will get re-written
+    # on the next run of this script. If not, this script will restart
+    # unbound again in half an hour (25min plus 5min grace time).
+    echo "$(expr $now + 1500)" > /var/tmp/unbound_last_resolved
+fi