nix/nixos/router.nix

{
  lib,
  # outputs,
  # config,
  pkgs,
  ...
}: let
  # NOTE: I could turn this into a cool NixOS module?
  # TODO: review https://francis.begyn.be/blog/nixos-home-router
  ip = "192.168.0.1";
  cidr = "${ip}/16";
  netmask = "255.255.0.0"; # see cidr
  dhcp_lease_space = {
    min = "192.168.0.5";
    max = "192.168.0.250";
  };
  wan_if = "wan0";
  lan_if = "lan0";
  hosts = {
    dragon = {
      identifier = "dragon";
      host = "dragon";
      ip = "192.168.0.10";
    };
    beefcake = {
      identifier = "beefcake";
      host = "beefcake";
      ip = "192.168.0.9";
    };
  };
in {
  imports = [
    {
      # hardware
      boot = {
        loader = {
          efi.canTouchEfiVariables = true;
          systemd-boot.enable = true;
        };
        initrd.availableKernelModules = ["xhci_pci"];
        initrd.kernelModules = [];
        kernelModules = ["kvm-intel"];
        extraModulePackages = [];
      };

      nixpkgs.hostPlatform = "x86_64-linux";
      powerManagement.cpuFreqGovernor = "performance";
      hardware.cpu.intel.updateMicrocode = true;
    }
  ];

  boot = {
    kernel = {
      sysctl = {
        "net.ipv4.conf.all.forwarding" = true;
        "net.ipv6.conf.all.forwarding" = true;

        # TODO: may want to disable this once it's working
        # "net.ipv6.conf.all.accept_ra" = 0;
        # "net.ipv6.conf.all.autoconf" = 0;
        # "net.ipv6.conf.all.use_tempaddr" = 0;

        "net.ipv6.conf.wan0.accept_ra" = 2;
        "net.ipv6.conf.wan0.autoconf" = 1;
      };
    };
  };

  # services.fail2ban.enable = true;
  services.radvd = {
    enable = false;
    # NOTE: this config is just the default arch linux config I think and may
    # need tweaking? this is what I had on the arch linux router, though :shrug:
    # config = ''
    #   interface lo
    #   {
    #   	AdvSendAdvert on;
    #   	MinRtrAdvInterval 3;
    #   	MaxRtrAdvInterval 10;
    #   	AdvDefaultPreference low;
    #   	AdvHomeAgentFlag off;

    #   	prefix 2001:db8:1:0::/64
    #   	{
    #   		AdvOnLink on;
    #   		AdvAutonomous on;
    #   		AdvRouterAddr off;
    #   	};

    #   	prefix 0:0:0:1234::/64
    #   	{
    #   		AdvOnLink on;
    #   		AdvAutonomous on;
    #   		AdvRouterAddr off;
    #   		Base6to4Interface ppp0;
    #   		AdvPreferredLifetime 120;
    #   		AdvValidLifetime 300;
    #   	};

    #   	route 2001:db0:fff::/48
    #   	{
    #   		AdvRoutePreference high;
    #   		AdvRouteLifetime 3600;
    #   	};

    #     RDNSS 2001:db8::1 2001:db8::2
    #     {
    #       AdvRDNSSLifetime 30;
    #     };

    #     DNSSL branch.example.com example.com
    #     {
    #       AdvDNSSLLifetime 30;
    #     };
    #   };
    # '';
  };

  # services.resolved = {
  #   enable = true;
  #   extraConfig = ''
  #     [Resolve]
  #     DNSStubListener=no
  #   '';
  # };

  services.dnsmasq = {
    enable = false;
    settings = {
      # server endpoints
      listen-address = "::1,127.0.0.1,${ip}";
      port = "53";

      # DNS cache entries
      cache-size = "10000";

      # local domain entries
      local = "/lan/";
      domain = "lan";
      expand-hosts = true;

      dhcp-authoritative = true;

      conf-file = "/usr/share/dnsmasq/trust-anchors.conf";
      dnssec = true;

      except-interface = "${wan_if}";
      interface = "${lan_if}";

      enable-ra = true;

      # dhcp-option = "121,${cidr},${ip}";

      dhcp-range = [
        "lan,${dhcp_lease_space.min},${dhcp_lease_space.max},${netmask},10m"
        "tag:${lan_if},::1,constructor:${lan_if},ra-names,12h"
      ];

      dhcp-host = [
        "${hosts.dragon.host},${hosts.dragon.ip},12h"
        "${hosts.beefcake.host},${hosts.beefcake.ip},12h"
      ];

      # may need to go in /etc/hosts (networking.extraHosts), too?
      address = [
        "/video.lyte.dev/192.168.0.9"
        "/git.lyte.dev/192.168.0.9"
        "/bw.lyte.dev/192.168.0.9"
        "/files.lyte.dev/192.168.0.9"
        "/vpn.h.lyte.dev/192.168.0.9"
        "/.h.lyte.dev/192.168.0.9"
      ];

      server = [
        "${ip}"
        "8.8.8.8"
        "8.8.4.4"
        "1.1.1.1"
        "1.0.0.1"
      ];
    };
  };

  environment.systemPackages = with pkgs; [
    wpa_supplicant
  ];

  networking = {
    hostName = "router";
    domain = "h.lyte.dev";
    useDHCP = false;
    wireless.enable = true;

    # useDHCP = true;
    # nat.enable = true; # TODO: maybe replace some of the nftables stuff with this module?

    extraHosts = ''
      127.0.0.1 localhost
      ${ip} router.h.lyte.dev router

      ::1 localhost ip6-localhost ip6-loopback
      ff02::1 ip6-allnodes
      ff02::2 ip6-allrouters
    '';

    firewall.enable = true;
    firewall.allowedTCPPorts = [
      2201
      22
    ];

    nftables = {
      enable = false;
      flushRuleset = true;

      tables = {
        filter = {
          family = "inet";
          content = ''
            chain input {
              # type filter hook input priority filter; policy accept;
              type filter hook input priority 0;

              # anything from loopback interface
              iifname "lo" accept

              # accept traffic we originated
              ct state { established, related } counter accept
              ct state invalid counter drop

              # ICMP
              ip6 nexthdr icmpv6 icmpv6 type { echo-request, nd-neighbor-solicit, nd-neighbor-advert, nd-router-solicit, nd-router-advert, mld-listener-query, destination-unreachable, packet-too-big, time-exceeded, parameter-problem } counter accept
              ip protocol icmp icmp type { echo-request, destination-unreachable, router-advertisement, time-exceeded, parameter-problem } counter accept
              ip protocol icmpv6 counter accept
              ip protocol icmp counter accept
              meta l4proto ipv6-icmp counter accept

              udp dport dhcpv6-client counter accept

              tcp dport { 64022, 22, 53, 67, 25565 } counter accept
              udp dport { 64020, 22, 53, 67 } counter accept

              # iifname "iot" ip saddr $iot-ip tcp dport { llmnr } counter accept
              # iifname "iot" ip saddr $iot-ip udp dport { mdns, llmnr } counter accept
              iifname "${lan_if}" tcp dport { llmnr } counter accept
              iifname "${lan_if}" udp dport { mdns, llmnr } counter accept

              counter drop
            }

            # allow all outgoing
            chain output {
              type filter hook output priority 0;
              accept
            }

            chain forward {
              type filter hook forward priority 0;
              accept
            }
          '';
        };

        nat = {
          family = "ip";
          content = ''
            set masq_saddr {
            	type ipv4_addr
            	flags interval
            	elements = { ${cidr} }
            }

            map map_port_ipport {
            	type inet_proto . inet_service : ipv4_addr . inet_service
            }

            chain prerouting {
            	iifname ${lan_if} accept

            	type nat hook prerouting priority dstnat + 1; policy accept;
            	fib daddr type local dnat ip addr . port to meta l4proto . th dport map @map_port_ipport

            	iifname ${wan_if} tcp dport { 22, 80, 443, 25565, 64022 } dnat to ${hosts.beefcake.ip}
            	iifname ${wan_if} udp dport { 64020 } dnat to ${hosts.beefcake.ip}

            	# iifname ${wan_if} tcp dport { 25565 } dnat to 192.168.0.244
            	# iifname ${wan_if} udp dport { 25565 } dnat to 192.168.0.244

            	# router
            	iifname ${wan_if} tcp dport { 2201 } dnat to ${ip}
            }

            chain output {
            	type nat hook output priority -99; policy accept;
            	ip daddr != 127.0.0.0/8 oif "lo" dnat ip addr . port to meta l4proto . th dport map @map_port_ipport
            }

            chain postrouting {
            	type nat hook postrouting priority srcnat + 1; policy accept;
            	oifname ${lan_if} masquerade
            	ip saddr @masq_saddr masquerade
            }
          '';
        };
      };
    };

    dhcpcd = {
      enable = false;
      extraConfig = ''
        duid

        # No way.... https://github.com/NetworkConfiguration/dhcpcd/issues/36#issuecomment-954777644
        # issues caused by guests with oneplus devices
        noarp

        persistent
        vendorclassid

        option domain_name_servers, domain_name, domain_search
        option classless_static_routes
        option interface_mtu
        option host_name
        #option ntp_servers

        require dhcp_server_identifier
        slaac private
        noipv4ll
        noipv6rs

        static domain_name_servers=${ip}

        interface ${wan_if}
        	gateway
        	ipv6rs
        	iaid 1
        	# option rapid_commit
        	# ia_na 1
        	ia_pd 1 ${lan_if}

        interface ${lan_if}
        	static ip_address=${cidr}
        	static routers=${ip}
        	static domain_name_servers=${ip}
      '';
    };
  };

  systemd.services.systemd-networkd-wait-online.enable = lib.mkForce false;

  services.openssh.listenAddresses = [
    {
      addr = "0.0.0.0";
      port = 2201;
    }
    {
      addr = "[::]";
      port = 2201;
    }
  ];

  systemd.network = {
    enable = true;
    networks = {
      wan = {
        networkConfig = {
          DHCP = "yes";
        };
      };
      lan = {
        networkConfig = {
          DHCP = "yes";
        };
      };
    };
    links = {
      "10-${wan_if}" = {
        enable = true;
        matchConfig = {
          MACAddress = "00:01:2e:82:73:59";
        };
        linkConfig = {
          Name = wan_if;
        };
      };
      "10-${lan_if}" = {
        enable = true;
        matchConfig = {
          MACAddress = "00:01:2e:82:73:5a";
        };
        linkConfig = {
          Name = lan_if;
        };
      };
    };
  };

  services.avahi = {
    enable = true;
    reflector = true;
    allowInterfaces = [lan_if];
  };

  system.stateVersion = "24.05";
}