Add network monitor script as plugin

Author: rramkumar1

config/network-problem-monitor.json

@@ -0,0 +1,18 @@
+{
+  "plugin": "custom",
+  "pluginConfig": {
+    "invoke_interval": "30s",
+    "timeout": "5s",
+    "max_output_length": 80,
+    "concurrency": 3
+  },
+  "source": "network-custom-plugin-monitor",
+  "rules": [
+    {
+      "type": "temporary",
+      "reason": "ConntrackFull",
+      "path": "./config/plugin/network_problem.sh",
+      "timeout": "3s"
+    }
+  ]
+}

config/plugin/network_problem.sh

@@ -0,0 +1,15 @@
+#!/bin/bash
+
+# This plugin checks for common network issues. Currently, it only checks
+# if the conntrack table is full. 
+
+conntrack_max=$(cat /proc/sys/net/ipv4/netfilter/ip_conntrack_max)
+conntrack_count=$(cat /proc/sys/net/ipv4/netfilter/ip_conntrack_count)
+if (( conntrack_count >= conntrack_max )); then
+  echo "Conntrack table full"
+  exit 1
+fi
+
+echo "Conntrack table available"
+exit 0
+