You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: tun.go
    path of file: ./repos/sliver/vendor/github.com/tailscale/wireguard-go/device
    
    the code of the file until where you have to start completion: /* SPDX-License-Identifier: MIT
 *
 * Copyright (C) 2017-2023 WireGuard LLC. All Rights Reserved.
 */

package device

import (
	"fmt"

	"github.com/tailscale/wireguard-go/tun"
)

const DefaultMTU = 1420

func (device *Device) RoutineTUNEventReader() {
	device.log.Verbosef("Routine: event worker - started")

	for event := range device.tun.device.Events() {
		if event&tun.EventMTUUpdate != 0 {
			mtu, err := device.tun.device.MTU()
			if err != nil {
				device.log.Errorf("Failed to load updated MTU of device: %v", err)
				continue
			}
			if mtu < 0 {
				device.log.Errorf("MTU not updated to negative value: %v", mtu)
				continue
			}
			var tooLarge string
			if mtu > MaxContentSize {
				tooLarge = fmt.Sprintf(" (too large, capped at %v)", MaxContentSize)
				mtu = MaxContentSize
			}
			old := device.tun.mtu.
    
func (device *Device) RoutineTUNEventReader() {
	device.log.Verbosef("Routine: event worker - started")

	for event := range device.tun.device.Events() {
		if event&tun.EventMTUUpdate != 0 {
			mtu, err := device.tun.device.MTU()
			if err != nil {
				device.log.Errorf("Failed to load updated MTU of device: %v", err)
				continue
			}
			if mtu < 0 {
				device.log.Errorf("MTU not updated to negative value: %v", mtu)
				continue
			}
			var tooLarge string
			if mtu > MaxContentSize {
				tooLarge = fmt.Sprintf(" (too large, capped at %v)", MaxContentSize)
				mtu = MaxContentSize
			}
			old := device.tun.mtu.Swap(int32(mtu))
			if int(old) != mtu {
				device.log.Verbosef("MTU updated: %v%s", mtu, tooLarge)
			}
		}

		if event&tun.EventUp != 0 {
			device.log.Verbosef("Interface up requested")
			device.Up()
		}

		if event&tun.EventDown != 0 {
			device.log.Verbosef("Interface down requested")
			device.Down()
		}
	}

	device.log.Verbosef("Routine: event worker - stopped")
}