Enhancement/ns dial error (#14)

* Include namespace in Vat connection errors to help diagnose misconfigured dial attempts.

* Report dial errors resulting from namespace mismatch.

go.mod

@@ -138,7 +138,7 @@ require (
 	github.com/multiformats/go-multibase v0.0.3 // indirect
 	github.com/multiformats/go-multicodec v0.4.1 // indirect
 	github.com/multiformats/go-multihash v0.1.0 // indirect
-	github.com/multiformats/go-multistream v0.3.0 // indirect
+	github.com/multiformats/go-multistream v0.3.0
 	github.com/multiformats/go-varint v0.0.6 // indirect
 	github.com/nxadm/tail v1.4.8 // indirect
 	github.com/onsi/ginkgo v1.16.5 // indirect

pkg/client/dialer_test.go

@@ -12,6 +12,7 @@ import (
 	swarm "github.com/libp2p/go-libp2p-swarm"
 	inproc "github.com/lthibault/go-libp2p-inproc-transport"
 	ma "github.com/multiformats/go-multiaddr"
+	"github.com/multiformats/go-multistream"
 
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -107,10 +108,46 @@ func TestDialer(t *testing.T) {
 			Boot: boot.StaticAddrs{*host.InfoFromHost(h)},
 		}.Dial(ctx)
 
+		assert.ErrorIs(t, err, multistream.ErrNotSupported)
 		assert.EqualError(t, err, "protocol not supported")
 		assert.Nil(t, n, "should return nil client node")
 	})
 
+	t.Run("NamespaceMismatch", func(t *testing.T) {
+		t.Parallel()
+
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+
+		h, err := libp2p.New(
+			libp2p.NoListenAddrs,
+			libp2p.NoTransports,
+			libp2p.ListenAddrStrings("/inproc/~"),
+			libp2p.Transport(inproc.New()))
+		require.NoError(t, err, "must succeed")
+		defer h.Close()
+
+		clt := newVat()
+		defer clt.Host.Close()
+
+		clt.NS = "wrong.namespace"
+
+		svr := vat.Network{
+			NS:   "test",
+			Host: h,
+		}
+		svr.Export(pubsub.Capability, mockPubSub{})
+		svr.Export(cluster.ViewCapability, mockView{})
+
+		n, err := client.Dialer{
+			Vat:  clt,
+			Boot: boot.StaticAddrs{*host.InfoFromHost(h)},
+		}.Dial(ctx)
+
+		assert.ErrorIs(t, err, vat.ErrInvalidNS)
+		assert.Nil(t, n, "should return nil client node")
+	})
+
 	t.Run("Success", func(t *testing.T) {
 		t.Parallel()
 

pkg/vat/vat.go

@@ -3,17 +3,22 @@ package vat
 
 import (
 	"context"
+	"errors"
+	"strings"
 
 	"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/protocol"
+	"github.com/multiformats/go-multistream"
 	ww "github.com/wetware/ww/pkg"
 
 	"capnproto.org/go/capnp/v3"
 	"capnproto.org/go/capnp/v3/rpc"
 )
 
+var ErrInvalidNS = errors.New("invalid namespace")
+
 type Capability interface {
 	// Protocols returns the IDs for the given capability.
 	// Implementations SHOULD order protocol identifiers in decreasing
@@ -79,7 +84,15 @@ func (n Network) Connect(ctx context.Context, vat peer.AddrInfo, c Capability) (
 
 	s, err := n.Host.NewStream(ctx, vat.ID, n.protocolsFor(c)...)
 	if err != nil {
-		return nil, err
+		if err != multistream.ErrNotSupported {
+			return nil, err
+		}
+
+		if n.isInvalidNS(vat.ID, c) {
+			return nil, ErrInvalidNS
+		}
+
+		return nil, err // TODO:  catch multistream.ErrNotSupported
 	}
 
 	return rpc.NewConn(c.Upgrade(s), &rpc.Options{
@@ -120,6 +133,34 @@ func (n Network) protocolsFor(c Capability) []protocol.ID {
 	return ps
 }
 
+func (n Network) isInvalidNS(id peer.ID, c Capability) bool {
+	ps, err := n.Host.Peerstore().GetProtocols(id)
+	if err != nil {
+		return false
+	}
+
+	for _, proto := range ps {
+		if match(c, proto) {
+			// the remote peer supports the capability, so it
+			// has to be a namespace mismatch.
+			return true
+		}
+	}
+
+	return false // not a ns issue; proto actually unsupported
+}
+
+// match the protocol, ignoring namespace
+func match(c Capability, proto string) bool {
+	for _, p := range c.Protocols() {
+		if strings.HasSuffix(proto, string(p)) {
+			return true
+		}
+	}
+
+	return false
+}
+
 func bootstrapper(c Capability) *capnp.Client {
 	if b, ok := c.(Bootstrapper); ok {
 		return b.Bootstrap()