Add UDP port exposure

Signed-off-by: Vasyl Gello <vasek.gello@gmail.com>

src/types/mapping.go

@@ -66,3 +66,63 @@ func (m *TCPMappings) Set(value string) error {
 	*m = append(*m, mapping)
 	return nil
 }
+
+type UDPMapping struct {
+	Listen *net.UDPAddr
+	Mapped *net.UDPAddr
+}
+
+type UDPMappings []UDPMapping
+
+func (m *UDPMappings) String() string {
+	return ""
+}
+
+func (m *UDPMappings) Set(value string) error {
+	tokens := strings.Split(value, ":")
+	if len(tokens) > 2 {
+		tokens = strings.SplitN(value, ":", 2)
+		host, port, err := net.SplitHostPort(tokens[1])
+		if err != nil {
+			return fmt.Errorf("failed to split host and port: %w", err)
+		}
+		tokens = append(tokens[:1], host, port)
+	}
+	listenport, err := strconv.Atoi(tokens[0])
+	if err != nil {
+		return fmt.Errorf("listen port is invalid: %w", err)
+	}
+	if listenport == 0 {
+		return fmt.Errorf("listen port must not be zero")
+	}
+	mapping := UDPMapping{
+		Listen: &net.UDPAddr{
+			Port: listenport,
+		},
+		Mapped: &net.UDPAddr{
+			IP:   net.IPv6loopback,
+			Port: listenport,
+		},
+	}
+	tokens = tokens[1:]
+	if len(tokens) > 0 {
+		mappedaddr := net.ParseIP(tokens[0])
+		if mappedaddr == nil {
+			return fmt.Errorf("invalid mapped address %q", tokens[0])
+		}
+		mapping.Mapped.IP = mappedaddr
+		tokens = tokens[1:]
+	}
+	if len(tokens) > 0 {
+		mappedport, err := strconv.Atoi(tokens[0])
+		if err != nil {
+			return fmt.Errorf("mapped port is invalid: %w", err)
+		}
+		if mappedport == 0 {
+			return fmt.Errorf("mapped port must not be zero")
+		}
+		mapping.Mapped.Port = mappedport
+	}
+	*m = append(*m, mapping)
+	return nil
+}

src/types/mapping_test.go

@@ -3,26 +3,48 @@ package types
 import "testing"
 
 func TestEndpointMappings(t *testing.T) {
-	var mappings TCPMappings
-	if err := mappings.Set("1234"); err != nil {
+	var tcpMappings TCPMappings
+	if err := tcpMappings.Set("1234"); err != nil {
 		t.Fatal(err)
 	}
-	if err := mappings.Set("1234:192.168.1.1"); err != nil {
+	if err := tcpMappings.Set("1234:192.168.1.1"); err != nil {
 		t.Fatal(err)
 	}
-	if err := mappings.Set("1234:192.168.1.1:4321"); err != nil {
+	if err := tcpMappings.Set("1234:192.168.1.1:4321"); err != nil {
 		t.Fatal(err)
 	}
-	if err := mappings.Set("1234:[2000::1]:4321"); err != nil {
+	if err := tcpMappings.Set("1234:[2000::1]:4321"); err != nil {
 		t.Fatal(err)
 	}
-	if err := mappings.Set("a"); err == nil {
+	if err := tcpMappings.Set("a"); err == nil {
 		t.Fatal("'a' should be an invalid exposed port")
 	}
-	if err := mappings.Set("1234:localhost"); err == nil {
+	if err := tcpMappings.Set("1234:localhost"); err == nil {
 		t.Fatal("mapped address must be an IP literal")
 	}
-	if err := mappings.Set("1234:localhost:a"); err == nil {
+	if err := tcpMappings.Set("1234:localhost:a"); err == nil {
+		t.Fatal("'a' should be an invalid mapped port")
+	}
+	var udpMappings UDPMappings
+	if err := udpMappings.Set("1234"); err != nil {
+		t.Fatal(err)
+	}
+	if err := udpMappings.Set("1234:192.168.1.1"); err != nil {
+		t.Fatal(err)
+	}
+	if err := udpMappings.Set("1234:192.168.1.1:4321"); err != nil {
+		t.Fatal(err)
+	}
+	if err := udpMappings.Set("1234:[2000::1]:4321"); err != nil {
+		t.Fatal(err)
+	}
+	if err := udpMappings.Set("a"); err == nil {
+		t.Fatal("'a' should be an invalid exposed port")
+	}
+	if err := udpMappings.Set("1234:localhost"); err == nil {
+		t.Fatal("mapped address must be an IP literal")
+	}
+	if err := udpMappings.Set("1234:localhost:a"); err == nil {
 		t.Fatal("'a' should be an invalid mapped port")
 	}
 }

src/types/udpproxy.go

@@ -0,0 +1,22 @@
+package types
+
+import (
+	"net"
+)
+
+func ReverseProxyUDP(mtu uint64, dst net.PacketConn, dstAddr net.Addr, src net.UDPConn) error {
+	buf := make([]byte, mtu)
+	for {
+		n, err := src.Read(buf[:])
+		if err != nil {
+			return err
+		}
+		if n > 0 {
+			n, err = dst.WriteTo(buf[:n], dstAddr)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	return nil
+}