nixos avahi-daemon: add new option declarations

Add new option declarations to control what information is published
by the avahi daemon. The default values are chosen to respect the
privacy of the user over the connectivity of the system.

nixos/modules/services/networking/avahi-daemon.nix

···
 # Avahi daemon.
-{ config, lib, pkgs, ... }:
+{ config, lib, utils, pkgs, ... }:
 
 with lib;
 
···
 
   cfg = config.services.avahi;
 
-  inherit (pkgs) avahi;
+  # We must escape interfaces due to the systemd interpretation
+  subsystemDevice = interface:
+    "sys-subsystem-net-devices-${utils.escapeSystemdPath interface}.device";
 
   avahiDaemonConf = with cfg; pkgs.writeText "avahi-daemon.conf" ''
     [server]
···
     browse-domains=${concatStringsSep ", " browseDomains}
     use-ipv4=${if ipv4 then "yes" else "no"}
     use-ipv6=${if ipv6 then "yes" else "no"}
+    ${optionalString (interfaces!=null) "allow-interfaces=${concatStringsSep "," interfaces}"}
 
     [wide-area]
     enable-wide-area=${if wideArea then "yes" else "no"}
 
     [publish]
-    disable-publishing=${if publishing then "no" else "yes"}
+    disable-publishing=${if publish.enable then "no" else "yes"}
+    disable-user-service-publishing=${if publish.userServices then "no" else "yes"}
+    publish-addresses=${if publish.userServices || publish.addresses then "yes" else "no"}
+    publish-hinfo=${if publish.hinfo then "yes" else "no"}
+    publish-workstation=${if publish.workstation then "yes" else "no"}
+    publish-domain=${if publish.domain then "yes" else "no"}
   '';
 
 in
···
         description = ''Whether to use IPv6'';
       };
 
+      interfaces = mkOption {
+        type = types.nullOr (types.listOf types.str);
+        default = null;
+        description = ''
+          List of network interfaces that should be used by the <command>avahi-daemon</command>.
+          Other interfaces will be ignored. If <literal>null</literal> all local interfaces
+          except loopback and point-to-point will be used.
+        '';
+      };
+
       wideArea = mkOption {
         default = true;
         description = ''Whether to enable wide-area service discovery.'';
       };
 
-      publishing = mkOption {
-        default = true;
-        description = ''Whether to allow publishing.'';
+      publish = {
+        enable = mkOption {
+          default = false;
+          description = ''Whether to allow publishing in general.'';
+        };
+
+        userServices = mkOption {
+          default = false;
+          description = ''Whether to publish user services. Will set <literal>addresses=true</literal>.'';
+        };
+
+        addresses = mkOption {
+          default = false;
+          description = ''Whether to register mDNS address records for all local IP addresses.'';
+        };
+
+        hinfo = mkOption {
+          default = false;
+          description = ''
+            Whether to register an mDNS HINFO record which contains information about the
+            local operating system and CPU.
+          '';
+        };
+
+        workstation = mkOption {
+          default = false;
+          description = ''Whether to register a service of type "_workstation._tcp" on the local LAN.'';
+        };
+
+        domain = mkOption {
+          default = false;
+          description = ''Whether to announce the locally used domain name for browsing by other hosts.'';
+        };
+
       };
 
       nssmdns = mkOption {
···
 
     system.nssModules = optional cfg.nssmdns pkgs.nssmdns;
 
-    environment.systemPackages = [ avahi ];
+    environment.systemPackages = [ pkgs.avahi ];
 
-    jobs.avahi_daemon =
-      { name = "avahi-daemon";
+    systemd.services.avahi-daemon =
+      let
+        deps = optionals (cfg.interfaces!=null) (map subsystemDevice cfg.interfaces);
+      in
+      { description = "Avahi daemon";
+        wantedBy = [ "ip-up.target" ];
+        bindsTo = deps;
+        after = deps;
+        before = [ "ip-up.target" ];
+        # Receive restart event after resume
+        partOf = [ "post-resume.target" ];
 
-        startOn = "ip-up";
+        path = [ pkgs.coreutils pkgs.avahi ];
+
+        preStart = "mkdir -p /var/run/avahi-daemon";
 
         script =
           ''
-            export PATH="${avahi}/bin:${avahi}/sbin:$PATH"
-
             # Make NSS modules visible so that `avahi_nss_support ()' can
             # return a sensible value.
             export LD_LIBRARY_PATH="${config.system.nssModules.path}"
 
-            mkdir -p /var/run/avahi-daemon
-
-            exec ${avahi}/sbin/avahi-daemon --syslog -f "${avahiDaemonConf}"
+            exec ${pkgs.avahi}/sbin/avahi-daemon --syslog -f "${avahiDaemonConf}"
           '';
       };
 
     services.dbus.enable = true;
-    services.dbus.packages = [avahi];
+    services.dbus.packages = [ pkgs.avahi ];
 
     # Enabling Avahi without exposing it in the firewall doesn't make
     # sense.