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package main
import (
"os"
"sync/atomic"
)
const DefaultMTU = 1420
type TUNEvent int
const (
TUNEventUp = 1 << iota
TUNEventDown
TUNEventMTUUpdate
)
type TUNDevice interface {
File() *os.File // returns the file descriptor of the device
Read([]byte, int) (int, error) // read a packet from the device (without any additional headers)
Write([]byte, int) (int, error) // writes a packet to the device (without any additional headers)
MTU() (int, error) // returns the MTU of the device
Name() string // returns the current name
Events() chan TUNEvent // returns a constant channel of events related to the device
Close() error // stops the device and closes the event channel
}
func (device *Device) RoutineTUNEventReader() {
logInfo := device.log.Info
logError := device.log.Error
for event := range device.tun.device.Events() {
if event&TUNEventMTUUpdate != 0 {
mtu, err := device.tun.device.MTU()
old := atomic.LoadInt32(&device.tun.mtu)
if err != nil {
logError.Println("Failed to load updated MTU of device:", err)
} else if int(old) != mtu {
if mtu+MessageTransportSize > MaxMessageSize {
logInfo.Println("MTU updated:", mtu, "(too large)")
} else {
logInfo.Println("MTU updated:", mtu)
}
atomic.StoreInt32(&device.tun.mtu, int32(mtu))
}
}
if event&TUNEventUp != 0 {
if !device.tun.isUp.Get() {
// begin listening for incomming datagrams
logInfo.Println("Interface set up")
device.tun.isUp.Set(true)
updateBind(device)
}
}
if event&TUNEventDown != 0 {
if device.tun.isUp.Get() {
// stop listening for incomming datagrams
logInfo.Println("Interface set down")
device.tun.isUp.Set(false)
closeBind(device)
}
}
}
}
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