added more requirements checks, minor code refactor

- Check kernel configs NET_DIAG_*.
- config.SaveConfiguration() -> config.Save()

daemon/core/system.go

@@ -127,6 +127,18 @@ func CheckSysRequirements() {
             ],
         "Reason": " * NETLINK extensions not supported by this kernel (CONFIG_NETFILTER_NETLINK, CONFIG_NETFILTER_NETLINK_QUEUE, CONFIG_NETFILTER_NETLINK_ACCT)."
     }
+},
+{
+    "Item": "net diagnostics",
+    "Checks": {
+        "Regexps": [
+			"CONFIG_INET_DIAG=[my]",
+			"CONFIG_INET_TCP_DIAG=[my]",
+			"CONFIG_INET_UDP_DIAG=[my]",
+			"CONFIG_INET_DIAG_DESTROY=[my]"
+            ],
+        "Reason": " * One or more socket monitoring interfaces are not enabled (CONFIG_INET_DIAG, CONFIG_INET_TCP_DIAG, CONFIG_INET_UDP_DIAG, CONFIG_DIAG_DESTROY (Reject feature))."
+    }
 }
 ]
 `

daemon/ui/config/config.go

@@ -69,8 +69,8 @@ func Parse(rawConfig interface{}) (conf Config, err error) {
 	return conf, err
 }
 
-// SaveConfiguration saves daemon config to disk.
-func SaveConfiguration(configFile, rawConfig string) (err error) {
+// Save writes daemon configuration to disk.
+func Save(configFile, rawConfig string) (err error) {
 	if _, err = Parse(rawConfig); err != nil {
 		return fmt.Errorf("Error parsing configuration %s: %s", rawConfig, err)
 	}

daemon/ui/notifications.go

@@ -109,7 +109,7 @@ func (c *Client) handleActionChangeConfig(stream protocol.UI_NotificationsClient
 	}
 
 	// this save operation triggers a re-loadConfiguration()
-	err = config.SaveConfiguration(configFile, notification.Data)
+	err = config.Save(configFile, notification.Data)
 	if err != nil {
 		log.Warning("[notification] CHANGE_CONFIG not applied %s", err)
 	}