common/lan-discovery.nix


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# LAN reachability and mDNS discovery shared by all machines.
{
  config,
  lib,
  ...
}:

let
  cfg = config.lanDiscovery;
in
{
  options.lanDiscovery.interface = lib.mkOption {
    type = lib.types.str;
    description = "Wi-Fi LAN interface used for mDNS discovery.";
  };

  config = {
    # Allow IPv4 ICMP echo requests so hosts can be found with ping.
    networking.firewall.allowPing = true;

    # Avahi/mDNS: publish <hostname>.local and resolve other *.local LAN names.
    # Keep the multicast DNS firewall opening scoped to the host's Wi-Fi LAN interface.
    networking.firewall.interfaces.${cfg.interface}.allowedUDPPorts = [ 5353 ];
    services.avahi = {
      enable = true;
      nssmdns4 = true;
      openFirewall = false;
      allowInterfaces = [ cfg.interface ];
      publish = {
        enable = true;
        addresses = true;
        workstation = true;
      };
    };
  };
}