* An Upstart job for ifplugd, which monitors Ethernet interfaces

for cables being plugged in or unplugged.  When this occurs, the
  dhclient service is restarted to automatically obtain a new IP 
  address.  This is useful for roaming users (laptops).

svn path=/nixos/trunk/; revision=9124

system/options.nix

@@ -310,6 +310,29 @@
   }
 
 
+  {
+    name = ["networking" "interfaceMonitor" "enable"];
+    default = false;
+    description = "
+      If <literal>true</literal>, monitor Ethernet interfaces for
+      cables being plugged in or unplugged.  When this occurs, the
+      <optional>dhclient</optional> service is restarted to
+      automatically obtain a new IP address.  This is useful for
+      roaming users (laptops).
+    ";
+  }
+
+
+  {
+    name = ["networking" "interfaceMonitor" "beep"];
+    default = false;
+    description = "
+      If <literal>true</literal>, beep when an Ethernet cable is
+      plugged in or unplugged.
+    ";
+  }
+
+
   {
     name = ["fileSystems"];
     default = [];

upstart-jobs/default.nix

@@ -119,6 +119,13 @@ import ../upstart-jobs/gather.nix {
       interfaces = config.get ["networking" "interfaces"];
     })
 
+  # ifplugd daemon for monitoring Ethernet cables.
+  ++ optional ["networking" "interfaceMonitor" "enable"]
+    (import ../upstart-jobs/ifplugd.nix {
+      inherit (pkgs) ifplugd writeScript bash;
+      inherit config;
+    })
+
   # DHCP server.
   ++ optional ["services" "dhcpd" "enable"]
     (import ../upstart-jobs/dhcpd.nix {

upstart-jobs/dhclient.nix

@@ -12,6 +12,8 @@ in
 
 {
   name = "dhclient";
+
+  extraPath = [dhcp];
   
   job = "
 description \"DHCP client\"

upstart-jobs/ifplugd.nix

@@ -0,0 +1,34 @@
+{ifplugd, config, writeScript, bash}:
+
+let
+
+  # The ifplugd action script, which is called whenever the link
+  # status changes (i.e., a cable is plugged in or unplugged).  We do
+  # nothing when a cable is unplugged.  When a cable is plugged in, we
+  # restart dhclient, which will hopefully give us a new IP address
+  # if appropriate.
+  plugScript = writeScript "ifplugd.action" "#! ${bash}/bin/sh
+    if test \"$2\" = up; then
+      initctl stop dhclient
+      initctl start dhclient
+    fi
+  ";
+
+in 
+
+{
+  name = "ifplugd";
+
+  extraPath = [ifplugd];
+  
+  job = "
+description \"Network interface connectivity monitor\"
+
+start on network-interfaces/started
+stop on network-interfaces/stop
+
+respawn ${ifplugd}/sbin/ifplugd --no-daemon --no-startup --no-shutdown \\
+    ${if config.get ["networking" "interfaceMonitor" "beep"] then "" else "--no-beep"} \\
+    --run ${plugScript}";
+  
+}