path: root/natpmp.go

package eth

import (
    "fmt"
    "net"

    natpmp "github.com/jackpal/go-nat-pmp"
)

// Adapt the NAT-PMP protocol to the NAT interface

// TODO:
//  + Register for changes to the external address.
//  + Re-register port mapping when router reboots.
//  + A mechanism for keeping a port mapping registered.

type natPMPClient struct {
    client *natpmp.Client
}

func NewNatPMP(gateway net.IP) (nat NAT) {
    return &natPMPClient{natpmp.NewClient(gateway)}
}

func (n *natPMPClient) GetExternalAddress() (addr net.IP, err error) {
    response, err := n.client.GetExternalAddress()
    if err != nil {
        return
    }
    ip := response.ExternalIPAddress
    addr = net.IPv4(ip[0], ip[1], ip[2], ip[3])
    return
}

func (n *natPMPClient) AddPortMapping(protocol string, externalPort, internalPort int,
    description string, timeout int) (mappedExternalPort int, err error) {
    if timeout <= 0 {
        err = fmt.Errorf("timeout must not be <= 0")
        return
    }
    // Note order of port arguments is switched between our AddPortMapping and the client's AddPortMapping.
    response, err := n.client.AddPortMapping(protocol, internalPort, externalPort, timeout)
    if err != nil {
        return
    }
    mappedExternalPort = int(response.MappedExternalPort)
    return
}

func (n *natPMPClient) DeletePortMapping(protocol string, externalPort, internalPort int) (err error) {
    // To destroy a mapping, send an add-port with
    // an internalPort of the internal port to destroy, an external port of zero and a time of zero.
    _, err = n.client.AddPortMapping(protocol, internalPort, 0, 0)
    return
}