fix dtls connection

listener/tun/metadata.go

@@ -10,11 +10,13 @@ import (
 )
 
 const (
-	DefaultMTU = 1350
+	defaultMTU            = 1350
+	defaultReadBufferSize = 4096
 )
 
 type metadata struct {
-	config *tun_util.Config
+	config         *tun_util.Config
+	readBufferSize int
 }
 
 func (l *tunListener) parseMetadata(md mdata.Metadata) (err error) {
@@ -28,13 +30,18 @@ func (l *tunListener) parseMetadata(md mdata.Metadata) (err error) {
 		gateway = "gw"
 	)
 
+	l.md.readBufferSize = mdutil.GetInt(md, "tun.rbuf", "rbuf", "readBufferSize")
+	if l.md.readBufferSize <= 0 {
+		l.md.readBufferSize = defaultReadBufferSize
+	}
+
 	config := &tun_util.Config{
 		Name: mdutil.GetString(md, name),
 		Peer: mdutil.GetString(md, peer),
 		MTU:  mdutil.GetInt(md, mtu),
 	}
 	if config.MTU <= 0 {
-		config.MTU = DefaultMTU
+		config.MTU = defaultMTU
 	}
 	if gw := mdutil.GetString(md, gateway); gw != "" {
 		config.Gateway = net.ParseIP(gw)

listener/tun/tun.go

@@ -12,11 +12,16 @@ const (
 )
 
 type tunDevice struct {
-	dev tun.Device
+	dev            tun.Device
+	readBufferSize int
 }
 
 func (d *tunDevice) Read(p []byte) (n int, err error) {
-	b := bufpool.Get(tunOffsetBytes + 65535)
+	rbuf := d.readBufferSize
+	if rbuf <= tunOffsetBytes {
+		rbuf = defaultReadBufferSize
+	}
+	b := bufpool.Get(rbuf)
 	defer bufpool.Put(b)
 
 	n, err = d.dev.Read(*b, tunOffsetBytes)
@@ -51,7 +56,8 @@ func (l *tunListener) createTunDevice() (dev io.ReadWriteCloser, name string, er
 	}
 
 	dev = &tunDevice{
-		dev: ifce,
+		dev:            ifce,
+		readBufferSize: l.md.readBufferSize,
 	}
 	name, err = ifce.Name()