nat, node, example/chat: expose IsPrivateIP() function, and only set …

…the nodes external address to the NAT Traversal-provided one should a `Host` not be configured

examples/chat/main.go

@@ -7,6 +7,7 @@ import (
 	"github.com/perlin-network/noise/cipher/aead"
 	"github.com/perlin-network/noise/handshake/ecdh"
 	"github.com/perlin-network/noise/log"
+	"github.com/perlin-network/noise/nat"
 	"github.com/perlin-network/noise/payload"
 	"github.com/perlin-network/noise/protocol"
 	"github.com/perlin-network/noise/skademlia"
@@ -68,12 +69,14 @@ func setup(node *noise.Node) {
 }
 
 func main() {
+	hostFlag := flag.String("h", "127.0.0.1", "host to listen for peers on")
 	portFlag := flag.Uint("p", 3000, "port to listen for peers on")
 	flag.Parse()
 
 	params := noise.DefaultParams()
-	//params.NAT = nat.NewPMP()
+	params.NAT = nat.NewPMP()
 	params.Keys = skademlia.RandomKeys()
+	params.Host = *hostFlag
 	params.Port = uint16(*portFlag)
 
 	node, err := noise.NewNode(params)

nat/mod.go

@@ -30,8 +30,8 @@ func parseCIDR(s string) *net.IPNet {
 	return block
 }
 
-// isPrivateIP returns whether or not an IP is within a private range.
-func isPrivateIP(ip net.IP) bool {
+// IsPrivateIP returns whether or not an IP is within a private range.
+func IsPrivateIP(ip net.IP) bool {
 	for _, ipnet := range privateBlocks {
 		if ipnet.Contains(ip) {
 			return true
@@ -65,7 +65,7 @@ func activeGateways() ([]net.IP, error) {
 				continue
 			}
 
-			if isPrivateIP(address.IP) {
+			if IsPrivateIP(address.IP) {
 				if ip := address.IP.Mask(address.Mask).To4(); ip != nil {
 					ip[3] = ip[3] | 0x01
 					gateways = append(gateways, ip)

node.go

@@ -294,7 +294,7 @@ func (n *Node) Kill() {
 }
 
 func (n *Node) ExternalAddress() string {
-	if n.nat != nil {
+	if n.nat != nil && nat.IsPrivateIP(net.ParseIP(n.host)) {
 		externalIP, err := n.nat.ExternalIP()
 		if err != nil {
 			panic(err)
@@ -303,5 +303,5 @@ func (n *Node) ExternalAddress() string {
 		return fmt.Sprintf("%s:%d", externalIP.String(), n.externalPort)
 	}
 
-	return fmt.Sprintf("%s:%d", n.host, n.ExternalPort())
+	return fmt.Sprintf("%s:%d", n.host, n.externalPort)
 }