add service fir dhcp v4 client

modules/network/default.nix

@@ -20,6 +20,14 @@ in {
         description = "network interface address";
         type = liminix.lib.types.serviceDefn;
       };
+      dhcp = {
+        client = mkOption {
+          # this needs to move to its own service as it has
+          # busybox config
+          description = "DHCP v4 client";
+          type = liminix.lib.types.serviceDefn;
+        };
+      };
     };
   };
   config = {
@@ -49,6 +57,12 @@ in {
           type = types.ints.between 0 128;
         };
       };
+      dhcp.client = liminix.callService ./dhcpc.nix {
+        interface = mkOption {
+          type = liminix.lib.types.service;
+        };
+      };
+
     };
   };
 }

modules/network/dhcpc.nix

@@ -0,0 +1,46 @@
+{
+  liminix
+, writeAshScript
+, serviceFns
+, lib
+} :
+{ interface }:
+let
+  inherit (liminix.services) longrun;
+  name = "${interface.name}.dhcpc";
+  script = writeAshScript "dhcp-notify"  { } ''
+    . ${serviceFns}
+    exec 2>&1
+    action=$1
+
+    set_address() {
+        ip address replace $ip/$mask dev $interface
+        (in_outputs ${name}
+         for i in lease mask ip router siaddr dns serverid subnet opt53 interface ; do
+            printenv $i > $i
+         done)
+    }
+    case $action in
+      deconfig)
+        ip address flush $interface
+        ip link set up dev $interface
+        ;;
+      bound)
+        # this doesn't actually replace, it adds a new address.
+        set_address
+        echo  >/proc/self/fd/10
+        ;;
+      renew)
+        set_address
+        ;;
+      nak)
+        echo "received NAK on $interface"
+        ;;
+    esac
+  '';
+in longrun {
+  inherit name;
+  run = "/bin/udhcpc -f -i $(output ${interface} ifname) -x hostname:$(cat /proc/sys/kernel/hostname) -s ${script}";
+  notification-fd = 10;
+  dependencies = [ interface ];
+}