Remove origin check for peer UDP packets

Checking source IP address is far from enough to ensure authenticity, it
is better to simply remove this and let the higher layer to worry about
peer authentication.

transport/udp/udp.go

@@ -32,16 +32,7 @@ func New(local, remote string) (*Conn, error) {
 
 // Read reads data from the peer.
 func (c *Conn) Read(b []byte) (int, error) {
-	n, addr, err := c.ReadFromUDP(b)
-	if err != nil {
-		return n, err
-	}
-
-	// Discard packets not from the peer
-	if addr.String() != c.remoteAddr.String() {
-		return 0, nil
-	}
-
+	n, _, err := c.ReadFromUDP(b)
 	return n, err
 }