Fix buffer.UDP destination override (#2356)

common/session/session.go

@@ -55,8 +55,9 @@ type Inbound struct {
 // Outbound is the metadata of an outbound connection.
 type Outbound struct {
 	// Target address of the outbound connection.
-	Target      net.Destination
-	RouteTarget net.Destination
+	OriginalTarget net.Destination
+	Target         net.Destination
+	RouteTarget    net.Destination
 	// Gateway address
 	Gateway net.Address
 }