NixOS/hosts/vps/network.nix

{
  config,
  lib,
  ...
}:
let
  externalInterface = config.my.interfaces.${config.networking.hostName};
  wgInterface = "wg0";
  ips = {
    homeServer = config.my.ips.wg-server;
    wgWorkstation = config.my.ips.wg-workstation;
    wgFriend1 = config.my.ips.wg-friend1;
    wgFriend6 = config.my.ips.wg-friend6;
  };
  subnets = {
    wgFriends = config.my.subnets.wg-friends;
    wgGuests = config.my.subnets.wg-guests;
    wgHomelab = config.my.subnets.wg-homelab;
  };
  ports = {
    inherit (config.my.ports)
      giteaSsh
      qbittorrent
      ssh
      wg
      ;
    web = [
      80
      443
    ];
    syncthing = config.my.ports.syncthingRelay;
    synapseFederation = config.my.ports.synapseSsl;
  };
  portsStr = {
    syncthing = toString config.my.ports.syncthingRelay;
    synapseFederation = toString config.my.ports.synapseSsl;
    synapseClient = toString config.my.servers.synapse.port;
    syncplay = toString config.my.servers.syncplay.port;
    synctube = toString config.my.servers.synctube.port;
    stash = toString config.my.servers.stash.port;
    jellyfin = toString config.my.servers.jellyfin.port;
    audiobookshelf = toString config.my.servers.audiobookshelf.port;
    kavita = toString config.my.servers.kavita.port;
    openWebui = toString config.my.ports.openWebui;
    sillytavern = toString config.my.ports.sillytavern;
    ollama = toString config.my.ports.ollama;
    comfyui = toString config.my.ports.comfyui;
  };
  forwardedPorts = [
    {
      comment = "snat ssh forward";
      port = ports.giteaSsh;
      proto = "tcp";
    }
    {
      comment = "snat qbittorrent tcp forward";
      port = ports.qbittorrent;
      proto = "tcp";
    }
    {
      comment = "snat qbittorrent udp forward";
      port = ports.qbittorrent;
      proto = "udp";
    }
  ];
  mkForwardPort =
    { port, proto, ... }:
    {
      sourcePort = port;
      inherit proto;
      destination = "${ips.homeServer}:${toString port}";
    };
  mkSnatRule =
    {
      comment,
      port,
      proto,
      ...
    }:
    ''iifname "${externalInterface}" oifname "${wgInterface}" ip daddr ${ips.homeServer}/32 ${proto} dport ${toString port} masquerade comment "${comment}"'';
in
{
  networking = {
    nat = {
      inherit externalInterface;
      enable = true;
      internalInterfaces = [ wgInterface ];
      forwardPorts = map mkForwardPort forwardedPorts;
    };
    nftables = {
      enable = true;
      tables.vps-snat = {
        family = "ip";
        content = ''
          chain postrouting {
            type nat hook postrouting priority srcnat;
            iifname "${wgInterface}" oifname "${externalInterface}" ip saddr ${subnets.wgHomelab} masquerade comment "snat homelab egress"
            ${lib.concatStringsSep "\n    " (map mkSnatRule forwardedPorts)}
          }
        '';
      };
    };
    firewall = {
      enable = true;
      filterForward = true;
      checkReversePath = "loose";
      allowedTCPPorts = [
        ports.ssh
        ports.qbittorrent
      ]
      ++ ports.web;
      allowedUDPPorts = [
        ports.wg
        ports.qbittorrent
      ];
      extraForwardRules = ''
        iifname "${wgInterface}" ip saddr ${subnets.wgFriends} ip daddr ${ips.homeServer}/32 tcp dport ${portsStr.syncthing} accept
        iifname "${wgInterface}" ip saddr ${ips.homeServer}/32 ip daddr ${subnets.wgFriends} tcp dport ${portsStr.syncthing} accept

        iifname "${wgInterface}" ip saddr ${subnets.wgFriends} ip daddr ${ips.homeServer}/32 tcp dport { ${portsStr.synapseClient}, ${portsStr.synapseFederation}, ${portsStr.syncplay}, ${portsStr.synctube} } accept

        iifname "${wgInterface}" ip saddr ${subnets.wgFriends} ip daddr ${ips.homeServer}/32 icmp type echo-request accept
        iifname "${wgInterface}" ip saddr ${ips.wgFriend1}/32 ip daddr ${ips.homeServer}/32 tcp dport ${portsStr.stash} accept
        iifname "${wgInterface}" ip saddr ${ips.wgFriend6}/32 ip daddr ${ips.homeServer}/32 tcp dport ${portsStr.stash} accept
        iifname "${wgInterface}" ip saddr ${subnets.wgGuests} ip daddr ${ips.homeServer}/32 tcp dport { ${portsStr.stash}, ${portsStr.jellyfin}, ${portsStr.audiobookshelf}, ${portsStr.kavita} } accept
        iifname "${wgInterface}" ip saddr ${subnets.wgGuests} ip daddr ${ips.homeServer}/32 icmp type echo-request accept

        iifname "${wgInterface}" ip saddr ${subnets.wgHomelab} ip daddr ${ips.homeServer}/32 accept
        iifname "${wgInterface}" ip saddr ${subnets.wgHomelab} ip daddr ${ips.wgWorkstation}/32 tcp dport { ${portsStr.openWebui}, ${portsStr.sillytavern}, ${portsStr.ollama}, ${portsStr.comfyui} } accept
        iifname "${wgInterface}" ip saddr ${ips.wgWorkstation}/32 ip daddr ${subnets.wgHomelab} tcp sport { ${portsStr.openWebui}, ${portsStr.sillytavern}, ${portsStr.ollama}, ${portsStr.comfyui} } accept

        iifname "${wgInterface}" ip saddr ${subnets.wgHomelab} oifname "${externalInterface}" accept
        iifname "${wgInterface}" ip saddr ${subnets.wgFriends} oifname "${externalInterface}" accept
        iifname "${wgInterface}" ip saddr ${subnets.wgGuests} oifname "${externalInterface}" accept

        ip saddr ${subnets.wgFriends} ip daddr ${subnets.wgHomelab} drop
        ip saddr ${subnets.wgHomelab} ip daddr ${subnets.wgFriends} drop
        ip saddr ${subnets.wgGuests} ip daddr ${subnets.wgHomelab} drop
        ip saddr ${subnets.wgHomelab} ip daddr ${subnets.wgGuests} drop
        ip saddr ${subnets.wgGuests} ip daddr ${subnets.wgFriends} drop
        ip saddr ${subnets.wgFriends} ip daddr ${subnets.wgGuests} drop
      '';
    };
  };
}