1 files changed, 55 insertions, 0 deletions
diff --git a/natpmp.go b/natpmp.go
new file mode 100644
index 000000000..489342a4b
--- /dev/null
+++ b/natpmp.go
@@ -0,0 +1,55 @@
+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
+}