os/kay/modules/router.nix


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{ ... }: let
  wanInterface = "ppp0";

  lanInterface = "enp8s0f3u1";
  subnet = "10.0.0.0";
  prefix = 24;
  host = "10.0.0.1";
  leaseRangeStart = "10.0.0.100";
  leaseRangeEnd = "10.0.0.254";
in {
  imports = [
    ./wireguard.nix
    ./iperf3.nix
  ];

  networking = {
    nat = {
      enable = true;
      externalInterface = wanInterface;
      internalInterfaces = [ lanInterface ];
    };
    interfaces."${lanInterface}" = {
      ipv4.addresses = [{ 
        address = host;
        prefixLength  = prefix;
      }];
    };
    firewall = {
      allowedUDPPorts = [ 53 67 ];
      allowedTCPPorts = [ 53 ];
      extraCommands = ''
        iptables -t nat -I POSTROUTING 1 \
            -s ${subnet}/${toString prefix} \
            -o ${wanInterface} \
            -j MASQUERADE
        iptables -t mangle -A FORWARD -p tcp --tcp-flags SYN,RST SYN \
            -o ${wanInterface} \
            -j TCPMSS --clamp-mss-to-pmtu
      '';
    };
  };

  services.dnsmasq.settings = {
    dhcp-range = [ "${leaseRangeStart},${leaseRangeEnd}" ];
    interface = [ lanInterface ];
  };
}