nixos/dhcpcd: optimize exitHook

  enableDHCP = config.networking.dhcpcd.enable &&

        (config.networking.useDHCP || any (i: i.useDHCP == true) interfaces);

  enableNTPService = (config.services.ntp.enable || config.services.ntpd-rs.enable || config.services.openntpd.enable || config.services.chrony.enable);

  # Don't start dhcpcd on explicitly configured interfaces or on

  # interfaces that are part of a bridge, bond or sit device.

  ignoredInterfaces =

      ${cfg.extraConfig}

    '';

  exitHook = pkgs.writeText "dhcpcd.exit-hook"

    ''

  exitHook = pkgs.writeText "dhcpcd.exit-hook" ''

    ${optionalString enableNTPService ''

      if [ "$reason" = BOUND -o "$reason" = REBOOT ]; then

          # Restart ntpd.  We need to restart it to make sure that it

          # will actually do something: if ntpd cannot resolve the

          # server hostnames in its config file, then it will never do

          # anything ever again ("couldn't resolve ..., giving up on

          # it"), so we silently lose time synchronisation. This also

          # applies to openntpd.

          /run/current-system/systemd/bin/systemctl try-reload-or-restart ntpd.service openntpd.service chronyd.service ntpd-rs.service || true

        # Restart ntpd. We need to restart it to make sure that it will actually do something:

        # if ntpd cannot resolve the server hostnames in its config file, then it will never do

        # anything ever again ("couldn't resolve ..., giving up on it"), so we silently lose

        # time synchronisation. This also applies to openntpd.

        ${optionalString config.services.ntp.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart ntpd.service || true"}

        ${optionalString config.services.ntpd-rs.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart ntpd-rs.service || true"}

        ${optionalString config.services.openntpd.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart openntpd.service || true"}

        ${optionalString config.services.chrony.enable "/run/current-system/systemd/bin/systemctl try-reload-or-restart chronyd.service || true"}

      fi

    ''}

    ${cfg.runHook}

  '';

        wants = [ "network.target" ];

        before = [ "network-online.target" ];

        restartTriggers = [ exitHook ];

        restartTriggers = optional (enableNTPService || cfg.runHook != "") [ exitHook ];

        # Stopping dhcpcd during a reconfiguration is undesirable

        # because it brings down the network interfaces configured by

    environment.systemPackages = [ dhcpcd ];

    environment.etc."dhcpcd.exit-hook".source = exitHook;

    environment.etc."dhcpcd.exit-hook" = mkIf (enableNTPService || cfg.runHook != "") {

      source = exitHook;

    };

    powerManagement.resumeCommands = mkIf config.systemd.services.dhcpcd.enable

      ''