Resolve addresses when creating a new stream (#1342)

* Resolve addresses when creating a new stream

BasicHost.NewStream will try to establish a connection if one doesn't already exist.  This will fail if the hosts addresses have not yet been resolved.  This PR resolves the hosts addresses before creating the stream and possible new connection.

Fixes #1302

* Changes from review comments

p2p/host/basic/basic_host.go

@@ -605,6 +605,17 @@ func (h *BasicHost) RemoveStreamHandler(pid protocol.ID) {
 // to create one. If ProtocolID is "", writes no header.
 // (Threadsafe)
 func (h *BasicHost) 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
+	// any addresses for the peer without any prior connections.
+	// If the caller wants to prevent the host from dialing, it should use the NoDial option.
+	if nodial, _ := network.GetNoDial(ctx); !nodial {
+		err := h.Connect(ctx, peer.AddrInfo{ID: p})
+		if err != nil {
+			return nil, err
+		}
+	}
+
 	s, err := h.Network().NewStream(ctx, p)
 	if err != nil {
 		return nil, err

p2p/host/basic/basic_host_test.go

@@ -6,6 +6,7 @@ import (
 	"io"
 	"io/ioutil"
 	"reflect"
+	"strings"
 	"sync"
 	"testing"
 	"time"
@@ -439,6 +440,51 @@ func TestNewDialOld(t *testing.T) {
 	require.Equal(t, s.Protocol(), protocol.ID("/testing"), "should have gotten /testing")
 }
 
+func TestNewStreamResolve(t *testing.T) {
+	h1, err := NewHost(swarmt.GenSwarm(t), nil)
+	require.NoError(t, err)
+	h2, err := NewHost(swarmt.GenSwarm(t), nil)
+	require.NoError(t, err)
+
+	ctx, cancel := context.WithTimeout(context.Background(), time.Second)
+	defer cancel()
+
+	// Get the tcp port that h2 is listening on.
+	h2pi := h2.Peerstore().PeerInfo(h2.ID())
+	var dialAddr string
+	const tcpPrefix = "/ip4/127.0.0.1/tcp/"
+	for _, addr := range h2pi.Addrs {
+		addrStr := addr.String()
+		if strings.HasPrefix(addrStr, tcpPrefix) {
+			port := addrStr[len(tcpPrefix):]
+			dialAddr = "/dns4/localhost/tcp/" + port
+			break
+		}
+	}
+	assert.NotEqual(t, dialAddr, "")
+
+	// Add the DNS multiaddr to h1's peerstore.
+	maddr, err := ma.NewMultiaddr(dialAddr)
+	require.NoError(t, err)
+	h1.Peerstore().AddAddr(h2.ID(), maddr, time.Second)
+
+	connectedOn := make(chan protocol.ID)
+	h2.SetStreamHandler("/testing", func(s network.Stream) {
+		connectedOn <- s.Protocol()
+		s.Close()
+	})
+
+	// NewStream will make a new connection using the DNS address in h1's
+	// peerstore.
+	s, err := h1.NewStream(ctx, h2.ID(), "/testing/1.0.0", "/testing")
+	require.NoError(t, err)
+
+	// force the lazy negotiation to complete
+	_, err = s.Write(nil)
+	require.NoError(t, err)
+	assertWait(t, connectedOn, "/testing")
+}
+
 func TestProtoDowngrade(t *testing.T) {
 	ctx, cancel := context.WithCancel(context.Background())
 	defer cancel()