Move proxy into pkg

Docker-DCO-1.1-Signed-off-by: Michael Crosby <michael@crosbymichael.com> (github: crosbymichael)

proxy/proxy.go

@@ -0,0 +1,29 @@
+package proxy
+
+import (
+	"fmt"
+	"net"
+)
+
+type Proxy interface {
+	// Start forwarding traffic back and forth the front and back-end
+	// addresses.
+	Run()
+	// Stop forwarding traffic and close both ends of the Proxy.
+	Close()
+	// Return the address on which the proxy is listening.
+	FrontendAddr() net.Addr
+	// Return the proxied address.
+	BackendAddr() net.Addr
+}
+
+func NewProxy(frontendAddr, backendAddr net.Addr) (Proxy, error) {
+	switch frontendAddr.(type) {
+	case *net.UDPAddr:
+		return NewUDPProxy(frontendAddr.(*net.UDPAddr), backendAddr.(*net.UDPAddr))
+	case *net.TCPAddr:
+		return NewTCPProxy(frontendAddr.(*net.TCPAddr), backendAddr.(*net.TCPAddr))
+	default:
+		panic(fmt.Errorf("Unsupported protocol"))
+	}
+}