p2p/nat: managed by host now.

Exposing the NAT to the core is unnecessary. The Host can take
care of it. If a need emerges, we can address it then.

host/basic/basic_host.go

 package basichost
 
 import (
+	"sync"
+
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
+	ma "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
+	goprocess "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/goprocess"
 
 	eventlog "github.com/jbenet/go-ipfs/thirdparty/eventlog"
 
+	inat "github.com/jbenet/go-ipfs/p2p/nat"
 	inet "github.com/jbenet/go-ipfs/p2p/net"
 	peer "github.com/jbenet/go-ipfs/p2p/peer"
 	protocol "github.com/jbenet/go-ipfs/p2p/protocol"
@@ -14,20 +19,35 @@ import (
 
 var log = eventlog.Logger("p2p/host/basic")
 
+type Option int
+
+const (
+	NATPortMap Option = iota
+)
+
 type BasicHost struct {
 	network inet.Network
 	mux     *protocol.Mux
 	ids     *identify.IDService
 	relay   *relay.RelayService
+
+	natmu sync.Mutex
+	nat   *inat.NAT
+
+	proc goprocess.Process
 }
 
 // New constructs and sets up a new *BasicHost with given Network
-func New(net inet.Network) *BasicHost {
+func New(net inet.Network, opts ...Option) *BasicHost {
 	h := &BasicHost{
 		network: net,
 		mux:     protocol.NewMux(),
 	}
 
+	h.proc = goprocess.WithTeardown(func() error {
+		return h.Network().Close()
+	})
+
 	// setup host services
 	h.ids = identify.NewIDService(h)
 	h.relay = relay.NewRelayService(h, h.Mux().HandleSync)
@@ -35,9 +55,48 @@ func New(net inet.Network) *BasicHost {
 	net.SetConnHandler(h.newConnHandler)
 	net.SetStreamHandler(h.newStreamHandler)
 
+	for _, o := range opts {
+		switch o {
+		case NATPortMap:
+			h.setupNATPortMap()
+		}
+	}
+
 	return h
 }
 
+func (h *BasicHost) setupNATPortMap() {
+	// do this asynchronously to avoid blocking daemon startup
+
+	h.proc.Go(func(worker goprocess.Process) {
+		nat := inat.DiscoverNAT()
+		if nat == nil { // no nat, or failed to get it.
+			return
+		}
+
+		select {
+		case <-worker.Closing():
+			nat.Close()
+			return
+		default:
+		}
+
+		// wire up the nat to close when proc closes.
+		h.proc.AddChild(nat.Process())
+
+		h.natmu.Lock()
+		h.nat = nat
+		h.natmu.Unlock()
+
+		addrs := h.Network().ListenAddresses()
+		nat.PortMapAddrs(addrs)
+		mapAddrs := nat.ExternalAddrs()
+		if len(mapAddrs) > 0 {
+			log.Infof("NAT mapping addrs: %s", mapAddrs)
+		}
+	})
+}
+
 // newConnHandler is the remote-opened conn handler for inet.Network
 func (h *BasicHost) newConnHandler(c inet.Conn) {
 	h.ids.IdentifyConn(c)
@@ -143,7 +202,23 @@ func (h *BasicHost) dialPeer(ctx context.Context, p peer.ID) error {
 	return nil
 }
 
+func (h *BasicHost) Addrs() []ma.Multiaddr {
+	addrs, err := h.Network().InterfaceListenAddresses()
+	if err != nil {
+		log.Debug("error retrieving network interface addrs")
+	}
+
+	h.natmu.Lock()
+	nat := h.nat
+	h.natmu.Unlock()
+	if nat != nil {
+		addrs = append(addrs, nat.ExternalAddrs()...)
+	}
+
+	return addrs
+}
+
 // Close shuts down the Host's services (network, etc).
 func (h *BasicHost) Close() error {
-	return h.Network().Close()
+	return h.proc.Close()
 }

host/host.go

@@ -2,6 +2,7 @@ package host
 
 import (
 	context "github.com/jbenet/go-ipfs/Godeps/_workspace/src/code.google.com/p/go.net/context"
+	ma "github.com/jbenet/go-ipfs/Godeps/_workspace/src/github.com/jbenet/go-multiaddr"
 
 	inet "github.com/jbenet/go-ipfs/p2p/net"
 	peer "github.com/jbenet/go-ipfs/p2p/peer"
@@ -23,6 +24,9 @@ type Host interface {
 	// Peerstore returns the Host's repository of Peer Addresses and Keys.
 	Peerstore() peer.Peerstore
 
+	// Returns the listen addresses of the Host
+	Addrs() []ma.Multiaddr
+
 	// Networks returns the Network interface of the Host
 	Network() inet.Network
 

nat/nat.go

@@ -29,9 +29,9 @@ var log = eventlog.Logger("nat")
 // Port mappings are renewed every (MappingDuration / 3)
 const MappingDuration = time.Second * 60
 
-// DiscoverGateway looks for a NAT device in the network and
+// DiscoverNAT looks for a NAT device in the network and
 // returns an object that can manage port mappings.
-func DiscoverGateway() *NAT {
+func DiscoverNAT() *NAT {
 	nat, err := nat.DiscoverGateway()
 	if err != nil {
 		log.Debug("DiscoverGateway error:", err)
@@ -72,6 +72,12 @@ func (nat *NAT) Close() error {
 	return nat.proc.Close()
 }
 
+// Process returns the nat's life-cycle manager, for making it listen
+// to close signals.
+func (nat *NAT) Process() goprocess.Process {
+	return nat.proc
+}
+
 // Notifier is an object that assists NAT in notifying listeners.
 // It is implemented using github.com/jbenet/go-ipfs/thirdparty/notifier
 type Notifier struct {