dotfiles/example/microvm/interfaces.nix

{
  config,
  lib,
  pkgs,
  ...
}:

let
  interfacesByType =
    wantedType: builtins.filter ({ type, ... }: type == wantedType) config.microvm.interfaces;

  tapInterfaces = interfacesByType "tap";
  macvtapInterfaces = interfacesByType "macvtap";

  tapFlags = lib.concatStringsSep " " (
    [ "vnet_hdr" ] ++ lib.optional config.microvm.declaredRunner.passthru.tapMultiQueue "multi_queue"
  );

  # TODO: don't hardcode but obtain from host config
  user = "microvm";
  group = "kvm";
in
{
  microvm.binScripts = lib.mkMerge [
    (lib.mkIf (tapInterfaces != [ ]) {
      tap-up = ''
        set -eou pipefail
      ''
      + lib.concatMapStrings (
        { id, ... }:
        ''
          if [ -e /sys/class/net/${id} ]; then
            ${lib.getExe' pkgs.iproute2 "ip"} link delete '${id}'
          fi

          ${lib.getExe' pkgs.iproute2 "ip"} tuntap add name '${id}' mode tap user '${user}' ${tapFlags}
          ${lib.getExe' pkgs.iproute2 "ip"} link set '${id}' up
        ''
      ) tapInterfaces;

      tap-down = ''
        set -ou pipefail
      ''
      + lib.concatMapStrings (
        { id, ... }:
        ''
          ${lib.getExe' pkgs.iproute2 "ip"} link delete '${id}'
        ''
      ) tapInterfaces;
    })
    (lib.mkIf (macvtapInterfaces != [ ]) {
      macvtap-up = ''
        set -eou pipefail
      ''
      + lib.concatMapStrings (
        {
          id,
          mac,
          macvtap,
          ...
        }:
        ''
          if [ -e /sys/class/net/${id} ]; then
            ${lib.getExe' pkgs.iproute2 "ip"} link delete '${id}'
          fi
          ${lib.getExe' pkgs.iproute2 "ip"} link add link '${macvtap.link}' name '${id}' address '${mac}' type macvtap mode '${macvtap.mode}'
          ${lib.getExe' pkgs.iproute2 "ip"} link set '${id}' allmulticast on
          if [ -f "/proc/sys/net/ipv6/conf/${id}/disable_ipv6" ]; then
            echo 1 > "/proc/sys/net/ipv6/conf/${id}/disable_ipv6"
          fi
          ${lib.getExe' pkgs.iproute2 "ip"} link set '${id}' up
          ${pkgs.coreutils-full}/bin/chown '${user}:${group}' /dev/tap$(< "/sys/class/net/${id}/ifindex")
        ''
      ) macvtapInterfaces;

      macvtap-down = ''
        set -ou pipefail
      ''
      + lib.concatMapStrings (
        { id, ... }:
        ''
          ${lib.getExe' pkgs.iproute2 "ip"} link delete '${id}'
        ''
      ) macvtapInterfaces;
    })
  ];
}