1 files changed, 58 insertions, 0 deletions
diff --git a/tun.go b/tun.go
new file mode 100644
index 0000000..6259f33
--- /dev/null
+++ b/tun.go
@@ -0,0 +1,58 @@
+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 && !device.isUp.Get() {
+			logInfo.Println("Interface set up")
+			device.Up()
+		}
+
+		if event&TUNEventDown != 0 && device.isUp.Get() {
+			logInfo.Println("Interface set down")
+			device.Down()
+		}
+	}
+}