Add support for the Avahi daemon.

The daemon starts correctly but, for some reason, clients fail
to connect to it.

svn path=/nixos/trunk/; revision=10999

system/ids.nix

@@ -11,6 +11,8 @@
     vsftpd = 7;
     ftp = 8;
     bitlbee = 9;
+    avahi = 10;
+
     nixbld = 30000; # start of range of uids
     nobody = 65534;
   };
@@ -21,7 +23,9 @@
     haldaemon = 5;
     vsftpd = 7;
     ftp = 8;
+    avahi = 10;
     audio = 17;
+
     users = 100;
     nixbld = 30000;
     nogroup = 65534;

system/options.nix

@@ -914,12 +914,57 @@
 
     };
 
+    avahi = {
+
+      enable = mkOption {
+        default = false;
+	description = ''
+	  Whether to run the Avahi daemon, which allows Avahi clients
+	  to use Avahi's service discovery facilities and also allows
+	  the local machine to advertise its presence and services
+	  (through the mDNS responder implemented by `avahi-daemon').
+	'';
+      };
+
+      hostName = mkOption {
+        default = "nixos";  # XXX: Would be nice to use `networking.hostName'.
+	description = ''Host name advertised on the LAN.'';
+      };
+
+      browseDomains = mkOption {
+        default = [ "0pointer.de" "zeroconf.org" ];
+	description = ''
+	  List of non-local DNS domains to be browsed.
+	'';
+      };
+
+      ipv4 = mkOption {
+        default = true;
+	description = ''Whether to use IPv4'';
+      };
+
+      ipv6 = mkOption {
+        default = false;
+	description = ''Whether to use IPv6'';
+      };
+
+      wideArea = mkOption {
+        default = true;
+	description = ''Whether to enable wide-area service discovery.'';
+      };
+
+      publishing = mkOption {
+        default = true;
+	description = ''Whether to allow publishing.'';
+      };
+    };
+
     bitlbee = {
 
       enable = mkOption {
         default = false;
         description = ''
-          Whether the run the BitlBee IRC to other chat network gateway.
+          Whether to run the BitlBee IRC to other chat network gateway.
           Running it allows you to access the MSN, Jabber, Yahoo! and ICQ chat
           networks via an IRC client.
         '';

upstart-jobs/avahi-daemon.nix

@@ -0,0 +1,44 @@
+{avahi, config, writeText, lib}:
+
+let
+
+  avahiDaemonConf = with config; writeText "avahi-daemon.conf" ''
+    [server]
+    host-name=${hostName}
+    browse-domains=${lib.concatStringsSep ", " browseDomains}
+    use-ipv4=${if ipv4 then "yes" else "no"}
+    use-ipv6=${if ipv6 then "yes" else "no"}
+
+    [wide-area]
+    enable-wide-area=${if wideArea then "yes" else "no"}
+
+    [publish]
+    disable-publishing=${if publishing then "no" else "yes"}
+  '';
+
+  avahiUid = (import ../system/ids.nix).uids.avahi;
+
+in
+
+{
+  name = "avahi-daemon";
+  
+  users = [
+    { name = "avahi";
+      uid = (import ../system/ids.nix).uids.avahi;
+      description = "`avahi-daemon' privilege separation user";
+      home = "/var/empty";
+    }
+  ];
+
+  job = ''
+    start on startup
+    stop on shutdown
+    respawn
+    script
+      export PATH="${avahi}/bin:${avahi}/sbin:$PATH"
+      exec ${avahi}/sbin/avahi-daemon --daemonize -f "${avahiDaemonConf}"
+    end script
+  '';
+
+}

upstart-jobs/default.nix

@@ -157,6 +157,13 @@ let
       servers = config.services.ntp.servers;
     })
 
+  # Avahi daemon.
+  ++ optional config.services.avahi.enable
+    (import ../upstart-jobs/avahi-daemon.nix {
+      inherit (pkgs) avahi writeText lib;
+      config = config.services.avahi;
+    })
+
   # X server.
   ++ optional config.services.xserver.enable
     (import ../upstart-jobs/xserver.nix {