dnsmasq: set ipv6 autoconfig in "router" mode

dnsmasq is configured to send RA, so the interface it's running on
should not also be accepting RA.

modules/dnsmasq/default.nix

@@ -15,6 +15,7 @@ let
   inherit (pkgs) liminix;
 in
 {
+  imports = [ ../ipv6-autoconfig ];
   options = {
     system.service.dnsmasq = mkOption {
       type = liminix.lib.types.serviceDefn;

modules/dnsmasq/service.nix

@@ -3,6 +3,7 @@
   dnsmasq,
   serviceFns,
   lib,
+  svc,
 }:
 {
   interface,
@@ -30,10 +31,17 @@ let
       v6s = concatStrings (map (a: ",[${a}]") v6);
     in
     "--dhcp-host=${mac},${v4}${v6s},${name},${builtins.toString leasetime}";
+  autoconfig = svc.ipv6.autoconfig.build {
+    inherit interface;
+    role = "router";
+  };
 in
 longrun {
   inherit name;
-  dependencies = [ interface ];
+  dependencies = [
+    interface
+    autoconfig
+  ];
   run = ''
     ${dnsmasq}/bin/dnsmasq \
     --user=${user} \