RoutedHost: Embed the underlying host instead of hiding it

When using a libp2p host with routing, the underlying concrete type is RoutedHost.
This type wraps the original Host type and hides it into a private field,
which makes it hard to make interface type assertions on the host.

E.g. sometimes it's useful to have access to the underlying instance of the IDService,
which is exposed by BasicHost as a method `IDService() identityIDService`, but is inaccessible
for type assertions because RoutedHost hides the BasicHost in its private field.

This commit uses type embedding, instead of a private field to fix it.

p2p/host/routed/routed.go

@@ -5,13 +5,12 @@ import (
 	"fmt"
 	"time"
 
-	"github.com/libp2p/go-libp2p/core/connmgr"
-	"github.com/libp2p/go-libp2p/core/event"
 	"github.com/libp2p/go-libp2p/core/host"
 	"github.com/libp2p/go-libp2p/core/network"
 	"github.com/libp2p/go-libp2p/core/peer"
 	"github.com/libp2p/go-libp2p/core/peerstore"
 	"github.com/libp2p/go-libp2p/core/protocol"
+	"github.com/libp2p/go-libp2p/core/routing"
 
 	logging "github.com/ipfs/go-log/v2"
 
@@ -28,10 +27,12 @@ const AddressTTL = time.Second * 10
 // This allows the Host to find the addresses for peers when
 // it does not have them.
 type RoutedHost struct {
-	host  host.Host // embedded other host.
-	route Routing
+	host.Host // Embedding the underlying host.
+	route     routing.PeerRouting
 }
 
+// Routing is an interface for peer routing.
+// Deprecated: use [routing.PeerRouting] instead.
 type Routing interface {
 	FindPeer(context.Context, peer.ID) (peer.AddrInfo, error)
 }
@@ -109,7 +110,7 @@ func (rh *RoutedHost) Connect(ctx context.Context, pi peer.AddrInfo) error {
 
 	// if we're here, we got some addrs. let's use our wrapped host to connect.
 	pi.Addrs = addrs
-	if cerr := rh.host.Connect(ctx, pi); cerr != nil {
+	if cerr := rh.Host.Connect(ctx, pi); cerr != nil {
 		// We couldn't connect. Let's check if we have the most
 		// up-to-date addresses for the given peer. If there
 		// are addresses we didn't know about previously, we
@@ -135,7 +136,7 @@ func (rh *RoutedHost) Connect(ctx context.Context, pi peer.AddrInfo) error {
 			}
 
 			pi.Addrs = newAddrs
-			return rh.host.Connect(ctx, pi)
+			return rh.Host.Connect(ctx, pi)
 		}
 		// No appropriate new address found.
 		// Return the original dial error.
@@ -163,42 +164,6 @@ func (rh *RoutedHost) findPeerAddrs(ctx context.Context, id peer.ID) ([]ma.Multi
 	return pi.Addrs, nil
 }
 
-func (rh *RoutedHost) ID() peer.ID {
-	return rh.host.ID()
-}
-
-func (rh *RoutedHost) Peerstore() peerstore.Peerstore {
-	return rh.host.Peerstore()
-}
-
-func (rh *RoutedHost) Addrs() []ma.Multiaddr {
-	return rh.host.Addrs()
-}
-
-func (rh *RoutedHost) Network() network.Network {
-	return rh.host.Network()
-}
-
-func (rh *RoutedHost) Mux() protocol.Switch {
-	return rh.host.Mux()
-}
-
-func (rh *RoutedHost) EventBus() event.Bus {
-	return rh.host.EventBus()
-}
-
-func (rh *RoutedHost) SetStreamHandler(pid protocol.ID, handler network.StreamHandler) {
-	rh.host.SetStreamHandler(pid, handler)
-}
-
-func (rh *RoutedHost) SetStreamHandlerMatch(pid protocol.ID, m func(protocol.ID) bool, handler network.StreamHandler) {
-	rh.host.SetStreamHandlerMatch(pid, m, handler)
-}
-
-func (rh *RoutedHost) RemoveStreamHandler(pid protocol.ID) {
-	rh.host.RemoveStreamHandler(pid)
-}
-
 func (rh *RoutedHost) NewStream(ctx context.Context, p peer.ID, pids ...protocol.ID) (network.Stream, error) {
 	// Ensure we have a connection, with peer addresses resolved by the routing system (#207)
 	// It is not sufficient to let the underlying host connect, it will most likely not have
@@ -211,14 +176,17 @@ func (rh *RoutedHost) NewStream(ctx context.Context, p peer.ID, pids ...protocol
 		}
 	}
 
-	return rh.host.NewStream(ctx, p, pids...)
+	return rh.Host.NewStream(ctx, p, pids...)
+}
+
+// Routing exposes the underlying routing system.
+func (rh *RoutedHost) Routing() routing.PeerRouting {
+	return rh.route
 }
+
 func (rh *RoutedHost) Close() error {
 	// no need to close IpfsRouting. we dont own it.
-	return rh.host.Close()
-}
-func (rh *RoutedHost) ConnManager() connmgr.ConnManager {
-	return rh.host.ConnManager()
+	return rh.Host.Close()
 }
 
 var _ (host.Host) = (*RoutedHost)(nil)

p2p/host/routed/routed_test.go

@@ -5,14 +5,15 @@ import (
 	"testing"
 
 	"github.com/libp2p/go-libp2p/core/peer"
+	"github.com/libp2p/go-libp2p/core/routing"
 	basic "github.com/libp2p/go-libp2p/p2p/host/basic"
 	swarmt "github.com/libp2p/go-libp2p/p2p/net/swarm/testing"
 
 	ma "github.com/multiformats/go-multiaddr"
 	"github.com/stretchr/testify/require"
 )
 
-var _ Routing = (*mockRouting)(nil)
+var _ routing.PeerRouting = (*mockRouting)(nil)
 
 type mockRouting struct {
 	callCount  int