flake/modules/services/wgautomesh.nix

{
  config,
  pkgs,
  lib,
  cfg,
  ...
}: let
  prefix = "lyn";

  # decrypt gossip secret
  # change this to comply with you secret management
  gossip_secret_path = config.sops.secrets."all/meshnetwork/gossip_secret".path;

  # function to make a peerlist suitable for wgautomesh
  buildPeerlist = version: hosts: let
    #filter out hosts that have wg.enabled set to false
    wgEnabledHosts = lib.filterAttrs (_: host: host.wg.enabled or false) hosts;
    #filter out hosts that don't support IP{$version}
    filteredHosts = lib.filterAttrs (_: host: host.${version} != null) wgEnabledHosts;
  in
    lib.mapAttrsToList (name: host: {
      pubkey = host.wg.pubkey;
      #if there is no public IP, make endpoint null so wgautomesh knows it unknown
      endpoint =
        if host.${version}.public == ""
        then null
        else "${host.${version}.public}:${toString host.wg.port}";
      address = host.${version}.internal;
    })
    filteredHosts;

  # helper vars to prettify
  meshnetwork = config.${prefix}.network;
  currentHost = meshnetwork.hosts.${config.networking.hostName};
  wireguardPort = currentHost.wg.port;
in {
  opt.useIPv6 = lib.mkOption {
    type = lib.types.bool;
    description = "Whether to use IPv6. Defaults to true";
    default = true;
  };
  config = {
    networking.firewall = {
      allowedUDPPorts = [
        wireguardPort
      ];
      extraCommands = ''
        # Allow UDP packets comming from port 1900 from a local address,
        # these are necessary for UPnP/IGD
        iptables -A INPUT -s 192.168.0.0/16 -p udp --sport 1900 -j ACCEPT
      '';
      extraStopCommands = ''
        iptables -D INPUT -s 192.168.0.0/16 -p udp --sport 1900 -j ACCEPT
      '';
    };

    networking.wireguard.interfaces.wg0 = {
      ips =
        if cfg.useIPv6
        then ["${currentHost.IPv6}/64"]
        else ["${currentHost.IPv4}/24"];
      listenPort = wireguardPort;
      privateKeyFile = "/var/lib/wireguard-keys/private";
      mtu = 1200;
    };

    services.wgautomesh = {
      enable = true;
      settings = {
        interface = "wg0";
        peers =
          if cfg.useIPv6
          then buildPeerlist "IPv6" meshnetwork.hosts
          else buildPeerlist "IPv4" meshnetwork.hosts;
        upnp_forward_external_port = wireguardPort;
      };
      gossipSecretFile = gossip_secret_path;

      #DEBUG
      logLevel = "trace";
    };
  };
}