nixos-config/machines/shinobu/services/router/default.nix

# Home network configuration
#
#     +----------+ +------------+
#     |          | |            | (clients)#  (guests)
#     |          | |         +--|--|--|--|-#+-|--|--|-|-unused|
# +---+----+   +-+-+-+-+-+   | 01 02 …… 12 # 13 …… 24 | 25 26 |
# |upstream|   | 1 2 3 4 |   | aruba Instant On 1830  | (SFP) |
# +--------+   | shinobu |   +------------------------+-------+
#              +---------+
#
# It consists of shinobu as a router (this configuration),
# connected to a aruba (HPE) Instant ON 1830 24-port 1GbE switch.
# The upstream comes (for now) from a PŸUR “WLAN-Kabelbox” (Compal CH7467CE).
# Sadly, I could not enable bridge mode on it, so the packets now go through (at least) three layers of NAT:
# device → NAT on shinobu → NAT on plastic router → PŸUR CGNAT
#
# Because of issues with the NICs operating at 2.5GbE,
# all clients are connected to the switch,
# even if they have a 2.5GbE NIC.
#
# Wireless is configured by providing the whole hostapd configuration file as a secret.
# Once nixpkgs PR 222536 is merged, I will migrate to using the NixOS module.
# Thanks to Intel’s wisdom, it’s not possible to use 5GHz in AP mode.
{ config, lib, pkgs, ... }:
let
  cfg = pkgs.callPackage ./common.nix { };
in
{
  imports = [
    ./dnsmasq.nix
    ./nft.nix
    ./tc.nix
  ];

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

  environment.systemPackages = with pkgs; [
    ethtool
  ];

  networking.useDHCP = false;

  systemd.network = {
    enable = true;
    # not all interfaces need to be up
    wait-online.extraArgs = [ "--any" ];
    netdevs = lib.mkMerge [
      (lib.mapAttrs
        (name: config: {
          netdevConfig = {
            Kind = "vlan";
            Name = name;
          };
          vlanConfig = {
            Id = config.id;
          };
        })
        cfg.vlan)
      (lib.mapAttrs'
        (name: config: lib.nameValuePair "br-${name}" {
          netdevConfig = {
            Name = "br-${name}";
            Kind = "bridge";
          };
        })
        cfg.vlan)
    ];
    networks = lib.mkMerge [
      (lib.mapAttrs
        (name: config: {
          inherit name;
          matchConfig = {
            Type = "vlan";
          };
          bridge = [ "br-${name}" ];
        })
        cfg.vlan)
      (lib.mapAttrs'
        (name: config: lib.nameValuePair "br-${name}" {
          name = "br-${name}";
          domains = [ config.domain ];
          address = lib.mapAttrsToList (family: familyConfig: familyConfig.gatewayCidr) config.subnet;
          networkConfig = {
            IPv6AcceptRA = false;
          };
        })
        cfg.vlan)
      {
        wan = {
          name = "enp1s0";
          DHCP = "ipv4";
          networkConfig = {
            IPv6AcceptRA = "yes";
          };
          dhcpV4Config = {
            UseDNS = "no";
          };
          ipv6AcceptRAConfig = {
            # Only use RA
            DHCPv6Client = false;
            UseDNS = "no";
          };
        };
        physical-lan = {
          name = "enp2s0";
          vlan = lib.attrNames cfg.vlan;
          # no autoconfiguration needed, only tagged VLAN
          networkConfig = {
            LinkLocalAddressing = "no";
            LLDP = "no";
            EmitLLDP = "no";
            IPv6AcceptRA = "no";
            IPv6SendRA = "no";
          };
        };
        lan2 = {
          name = "enp3s0";
          bridge = [ "br-lan" ];
        };
        lan3 = {
          name = "enp4s0";
          bridge = [ "br-lan" ];
        };
      }
    ];
  };
  services.resolved.enable = false;
}