NixOS/hosts/server/network.nix

{
  config,
  lib,
  pkgs,
  ...
}:
let
  qbittorrentRouteTable = 200;
  qbitUser = config.services.qbittorrent.user;
  serverInterface = config.my.interfaces.server;
  wgInterface = "wg0";
  wgServerIp = config.my.ips.wg-server;
in
{
  my.network.firewall = {
    enabledServicePorts = true;
    additionalPorts = [
      2049
      config.my.ports.syncthingGui
      config.my.ports.syncthingRelay
      config.my.ports.sonarqube
      config.my.ports.synapseSsl
      config.my.ports.tdarr
      config.my.ports.mediaMap
      config.my.ports.qbittorrent
    ];
  };
  networking = {
    iproute2.rttablesExtraConfig = ''
      ${toString qbittorrentRouteTable} qbittorrent
    '';
    wireguard.interfaces.${wgInterface} = lib.mkIf config.my.secureHost {
      allowedIPsAsRoutes = false;
      ips = [ "${wgServerIp}/32" ];
      privateKeyFile = config.sops.secrets."server/private".path;
      peers = [
        {
          publicKey = "dFbiSekBwnZomarcS31o5+w6imHjMPNCipkfc2fZ3GY=";
          endpoint = "${config.my.ips.vps}:51820";
          allowedIPs = [
            "0.0.0.0/0"
            "${config.my.ips.wg-vps}/32"
            config.my.subnets.wg-homelab
            config.my.subnets.wg-friends
            config.my.subnets.wg-guests
          ];
          persistentKeepalive = 25;
        }
      ];
    };
    firewall = {
      allowedUDPPorts = config.networking.firewall.allowedTCPPorts;
      interfaces.${wgInterface}.allowedTCPPorts = [ config.my.servers.nextcloud.port ];
    };
  };
  systemd.services.qbittorrent-vpn-routing =
    lib.mkIf (config.my.secureHost && config.services.qbittorrent.enable)
      {
        description = "Route qBittorrent user traffic through the VPS WireGuard tunnel";
        before = [ "qbittorrent.service" ];
        wantedBy = [ "multi-user.target" ];
        after = [
          "network-online.target"
          "wireguard-${wgInterface}.service"
        ];
        wants = [
          "network-online.target"
          "wireguard-${wgInterface}.service"
        ];
        path = with pkgs; [
          coreutils
          gnugrep
          iproute2
          shadow
        ];
        script = ''
          qbit_uid="$(id -u ${qbitUser})"

          for _ in $(seq 1 30); do
            if ip -4 addr show dev ${wgInterface} >/dev/null 2>&1; then
              break
            fi
            sleep 1
          done

          if ! ip -4 addr show dev ${wgInterface} >/dev/null 2>&1; then
            echo "${wgInterface} is not available"
            exit 1
          fi

          ip -4 route replace ${config.my.subnets.wg-homelab} dev ${wgInterface} src ${wgServerIp}
          ip -4 route replace ${config.my.subnets.wg-friends} dev ${wgInterface} src ${wgServerIp}
          ip -4 route replace ${config.my.subnets.wg-guests} dev ${wgInterface} src ${wgServerIp}

          ip -4 route replace table ${toString qbittorrentRouteTable} ${config.my.subnets.wg-homelab} dev ${wgInterface} src ${wgServerIp}
          ip -4 route replace table ${toString qbittorrentRouteTable} ${config.my.subnets.wg-friends} dev ${wgInterface} src ${wgServerIp}
          ip -4 route replace table ${toString qbittorrentRouteTable} ${config.my.subnets.wg-guests} dev ${wgInterface} src ${wgServerIp}
          ip -4 route replace table ${toString qbittorrentRouteTable} 10.88.0.0/16 dev podman0 src 10.88.0.1
          ip -4 route replace table ${toString qbittorrentRouteTable} 192.168.100.0/24 dev ${serverInterface} src ${config.my.ips.server}
          ip -4 route replace table ${toString qbittorrentRouteTable} ${config.my.ips.vps}/32 via ${config.my.ips.router} dev ${serverInterface} src ${config.my.ips.server}
          ip -4 route replace table ${toString qbittorrentRouteTable} default via ${config.my.ips.wg-vps} dev ${wgInterface} src ${wgServerIp}

          while ip -4 rule show | grep -q "uidrange ''${qbit_uid}-''${qbit_uid} lookup ${toString qbittorrentRouteTable}"; do
            ip -4 rule del uidrange "''${qbit_uid}-''${qbit_uid}" lookup ${toString qbittorrentRouteTable}
          done

          while ip -4 rule show | grep -q 'from ${wgServerIp} lookup ${toString qbittorrentRouteTable}'; do
            ip -4 rule del from ${wgServerIp}/32 lookup ${toString qbittorrentRouteTable}
          done

          ip -4 rule add from ${wgServerIp}/32 lookup ${toString qbittorrentRouteTable} priority 9999
          ip -4 rule add uidrange "''${qbit_uid}-''${qbit_uid}" lookup ${toString qbittorrentRouteTable} priority 10000
        '';
        preStop = ''
          qbit_uid="$(id -u ${qbitUser})"

          while ip -4 rule show | grep -q 'from ${wgServerIp} lookup ${toString qbittorrentRouteTable}'; do
            ip -4 rule del from ${wgServerIp}/32 lookup ${toString qbittorrentRouteTable} || true
          done

          while ip -4 rule show | grep -q "uidrange ''${qbit_uid}-''${qbit_uid} lookup ${toString qbittorrentRouteTable}"; do
            ip -4 rule del uidrange "''${qbit_uid}-''${qbit_uid}" lookup ${toString qbittorrentRouteTable} || true
          done

          ip -4 route del ${config.my.subnets.wg-homelab} dev ${wgInterface} || true
          ip -4 route del ${config.my.subnets.wg-friends} dev ${wgInterface} || true
          ip -4 route del ${config.my.subnets.wg-guests} dev ${wgInterface} || true
          ip -4 route flush table ${toString qbittorrentRouteTable} || true
        '';
        serviceConfig = {
          RemainAfterExit = true;
          Type = "oneshot";
        };
      };
}