lib/pmp: Add NAT-PMP support (ref #698)

GitHub-Pull-Request: https://github.com/syncthing/syncthing/pull/2968

vendor/github.com/AudriusButkevicius/go-nat-pmp/natpmp.go

@@ -0,0 +1,189 @@
+package natpmp
+
+import (
+	"fmt"
+	"net"
+	"time"
+
+	"github.com/jackpal/gateway"
+)
+
+// Implement the NAT-PMP protocol, typically supported by Apple routers and open source
+// routers such as DD-WRT and Tomato.
+//
+// See http://tools.ietf.org/html/draft-cheshire-nat-pmp-03
+//
+// Usage:
+//
+//    client := natpmp.NewClient(gatewayIP)
+//    response, err := client.GetExternalAddress()
+
+const nAT_PMP_PORT = 5351
+
+// The recommended mapping lifetime for AddPortMapping
+const RECOMMENDED_MAPPING_LIFETIME_SECONDS = 3600
+
+// Client is a NAT-PMP protocol client.
+type Client struct {
+	gateway net.IP
+	timeout time.Duration
+}
+
+// Create a NAT-PMP client for the NAT-PMP server at the gateway.
+func NewClient(gateway net.IP, timeout time.Duration) (nat *Client) {
+	return &Client{gateway, timeout}
+}
+
+// Create a NAT-PMP client for the NAT-PMP server at the default gateway.
+func NewClientForDefaultGateway(timeout time.Duration) (nat *Client, err error) {
+	var g net.IP
+	g, err = gateway.DiscoverGateway()
+	if err != nil {
+		return
+	}
+	nat = NewClient(g, timeout)
+	return
+}
+
+// Results of the NAT-PMP GetExternalAddress operation
+type GetExternalAddressResult struct {
+	SecondsSinceStartOfEpoc uint32
+	ExternalIPAddress       [4]byte
+}
+
+// Get the external address of the router.
+func (n *Client) GetExternalAddress() (result *GetExternalAddressResult, err error) {
+	msg := make([]byte, 2)
+	msg[0] = 0 // Version 0
+	msg[1] = 0 // OP Code 0
+	response, err := n.rpc(msg, 12)
+	if err != nil {
+		return
+	}
+	result = &GetExternalAddressResult{}
+	result.SecondsSinceStartOfEpoc = readNetworkOrderUint32(response[4:8])
+	copy(result.ExternalIPAddress[:], response[8:12])
+	return
+}
+
+// Results of the NAT-PMP AddPortMapping operation
+type AddPortMappingResult struct {
+	SecondsSinceStartOfEpoc      uint32
+	InternalPort                 uint16
+	MappedExternalPort           uint16
+	PortMappingLifetimeInSeconds uint32
+}
+
+// Add (or delete) a port mapping. To delete a mapping, set the requestedExternalPort and lifetime to 0
+func (n *Client) AddPortMapping(protocol string, internalPort, requestedExternalPort int, lifetime int) (result *AddPortMappingResult, err error) {
+	var opcode byte
+	if protocol == "udp" {
+		opcode = 1
+	} else if protocol == "tcp" {
+		opcode = 2
+	} else {
+		err = fmt.Errorf("unknown protocol %v", protocol)
+		return
+	}
+	msg := make([]byte, 12)
+	msg[0] = 0 // Version 0
+	msg[1] = opcode
+	writeNetworkOrderUint16(msg[4:6], uint16(internalPort))
+	writeNetworkOrderUint16(msg[6:8], uint16(requestedExternalPort))
+	writeNetworkOrderUint32(msg[8:12], uint32(lifetime))
+	response, err := n.rpc(msg, 16)
+	if err != nil {
+		return
+	}
+	result = &AddPortMappingResult{}
+	result.SecondsSinceStartOfEpoc = readNetworkOrderUint32(response[4:8])
+	result.InternalPort = readNetworkOrderUint16(response[8:10])
+	result.MappedExternalPort = readNetworkOrderUint16(response[10:12])
+	result.PortMappingLifetimeInSeconds = readNetworkOrderUint32(response[12:16])
+	return
+}
+
+func (n *Client) rpc(msg []byte, resultSize int) (result []byte, err error) {
+	var server net.UDPAddr
+	server.IP = n.gateway
+	server.Port = nAT_PMP_PORT
+	conn, err := net.DialUDP("udp", nil, &server)
+	if err != nil {
+		return
+	}
+	defer conn.Close()
+
+	result = make([]byte, resultSize)
+
+	timeout := time.Now().Add(n.timeout)
+
+	err = conn.SetDeadline(timeout)
+	if err != nil {
+		return
+	}
+
+	var bytesRead int
+	var remoteAddr *net.UDPAddr
+	for time.Now().Before(timeout) {
+		_, err = conn.Write(msg)
+		if err != nil {
+			return
+		}
+
+		bytesRead, remoteAddr, err = conn.ReadFromUDP(result)
+		if err != nil {
+			if err.(net.Error).Timeout() {
+				continue
+			}
+			return
+		}
+
+		if !remoteAddr.IP.Equal(n.gateway) {
+			// Ignore this packet.
+			continue
+		}
+		if bytesRead != resultSize {
+			err = fmt.Errorf("unexpected result size %d, expected %d", bytesRead, resultSize)
+			return
+		}
+		if result[0] != 0 {
+			err = fmt.Errorf("unknown protocol version %d", result[0])
+			return
+		}
+		expectedOp := msg[1] | 0x80
+		if result[1] != expectedOp {
+			err = fmt.Errorf("Unexpected opcode %d. Expected %d", result[1], expectedOp)
+			return
+		}
+		resultCode := readNetworkOrderUint16(result[2:4])
+		if resultCode != 0 {
+			err = fmt.Errorf("Non-zero result code %d", resultCode)
+			return
+		}
+		// If we got here the RPC is good.
+		return
+	}
+
+	err = fmt.Errorf("Timed out trying to contact gateway")
+	return
+}
+
+func writeNetworkOrderUint16(buf []byte, d uint16) {
+	buf[0] = byte(d >> 8)
+	buf[1] = byte(d)
+}
+
+func writeNetworkOrderUint32(buf []byte, d uint32) {
+	buf[0] = byte(d >> 24)
+	buf[1] = byte(d >> 16)
+	buf[2] = byte(d >> 8)
+	buf[3] = byte(d)
+}
+
+func readNetworkOrderUint16(buf []byte) uint16 {
+	return (uint16(buf[0]) << 8) | uint16(buf[1])
+}
+
+func readNetworkOrderUint32(buf []byte) uint32 {
+	return (uint32(buf[0]) << 24) | (uint32(buf[1]) << 16) | (uint32(buf[2]) << 8) | uint32(buf[3])
+}