145 lines
3.9 KiB
Go
145 lines
3.9 KiB
Go
package natpmp
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import (
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"fmt"
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"net"
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)
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// Implement the NAT-PMP protocol, typically supported by Apple routers and open source
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// routers such as DD-WRT and Tomato.
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//
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// See http://tools.ietf.org/html/draft-cheshire-nat-pmp-03
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//
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// Usage:
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//
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// client := natpmp.NewClient(gatewayIP)
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// response, err := client.GetExternalAddress()
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// The recommended mapping lifetime for AddPortMapping
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const RECOMMENDED_MAPPING_LIFETIME_SECONDS = 3600
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// Interface used to make remote procedure calls.
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type caller interface {
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call(msg []byte) (result []byte, err error)
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}
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// Client is a NAT-PMP protocol client.
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type Client struct {
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caller caller
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}
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// Create a NAT-PMP client for the NAT-PMP server at the gateway.
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func NewClient(gateway net.IP) (nat *Client) {
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return &Client{&network{gateway}}
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}
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// Results of the NAT-PMP GetExternalAddress operation.
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type GetExternalAddressResult struct {
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SecondsSinceStartOfEpoc uint32
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ExternalIPAddress [4]byte
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}
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// Get the external address of the router.
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func (n *Client) GetExternalAddress() (result *GetExternalAddressResult, err error) {
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msg := make([]byte, 2)
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msg[0] = 0 // Version 0
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msg[1] = 0 // OP Code 0
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response, err := n.rpc(msg, 12)
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if err != nil {
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return
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}
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result = &GetExternalAddressResult{}
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result.SecondsSinceStartOfEpoc = readNetworkOrderUint32(response[4:8])
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copy(result.ExternalIPAddress[:], response[8:12])
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return
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}
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// Results of the NAT-PMP AddPortMapping operation
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type AddPortMappingResult struct {
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SecondsSinceStartOfEpoc uint32
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InternalPort uint16
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MappedExternalPort uint16
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PortMappingLifetimeInSeconds uint32
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}
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// Add (or delete) a port mapping. To delete a mapping, set the requestedExternalPort and lifetime to 0
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func (n *Client) AddPortMapping(protocol string, internalPort, requestedExternalPort int, lifetime int) (result *AddPortMappingResult, err error) {
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var opcode byte
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if protocol == "udp" {
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opcode = 1
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} else if protocol == "tcp" {
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opcode = 2
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} else {
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err = fmt.Errorf("unknown protocol %v", protocol)
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return
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}
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msg := make([]byte, 12)
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msg[0] = 0 // Version 0
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msg[1] = opcode
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writeNetworkOrderUint16(msg[4:6], uint16(internalPort))
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writeNetworkOrderUint16(msg[6:8], uint16(requestedExternalPort))
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writeNetworkOrderUint32(msg[8:12], uint32(lifetime))
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response, err := n.rpc(msg, 16)
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if err != nil {
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return
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}
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result = &AddPortMappingResult{}
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result.SecondsSinceStartOfEpoc = readNetworkOrderUint32(response[4:8])
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result.InternalPort = readNetworkOrderUint16(response[8:10])
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result.MappedExternalPort = readNetworkOrderUint16(response[10:12])
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result.PortMappingLifetimeInSeconds = readNetworkOrderUint32(response[12:16])
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return
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}
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func (n *Client) rpc(msg []byte, resultSize int) (result []byte, err error) {
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result, err = n.caller.call(msg)
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if err != nil {
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return
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}
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err = protocolChecks(msg, resultSize, result)
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return
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}
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func protocolChecks(msg []byte, resultSize int, result []byte) (err error) {
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if len(result) != resultSize {
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err = fmt.Errorf("unexpected result size %d, expected %d", len(result), resultSize)
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return
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}
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if result[0] != 0 {
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err = fmt.Errorf("unknown protocol version %d", result[0])
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return
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}
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expectedOp := msg[1] | 0x80
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if result[1] != expectedOp {
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err = fmt.Errorf("Unexpected opcode %d. Expected %d", result[1], expectedOp)
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return
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}
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resultCode := readNetworkOrderUint16(result[2:4])
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if resultCode != 0 {
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err = fmt.Errorf("Non-zero result code %d", resultCode)
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return
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}
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// If we got here the RPC is good.
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return
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}
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func writeNetworkOrderUint16(buf []byte, d uint16) {
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buf[0] = byte(d >> 8)
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buf[1] = byte(d)
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}
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func writeNetworkOrderUint32(buf []byte, d uint32) {
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buf[0] = byte(d >> 24)
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buf[1] = byte(d >> 16)
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buf[2] = byte(d >> 8)
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buf[3] = byte(d)
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}
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func readNetworkOrderUint16(buf []byte) uint16 {
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return (uint16(buf[0]) << 8) | uint16(buf[1])
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}
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func readNetworkOrderUint32(buf []byte) uint32 {
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return (uint32(buf[0]) << 24) | (uint32(buf[1]) << 16) | (uint32(buf[2]) << 8) | uint32(buf[3])
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}
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