use the host black hole detector to check for dialability

config/config.go

@@ -216,6 +216,12 @@ func (cfg *Config) makeAutoNATHost() (*blankhost.BlankHost, error) {
 		PeerKey:            autonatPrivKey,
 		Peerstore:          ps,
 		DialRanker:         swarm.NoDelayDialRanker,
+		SwarmOpts: []swarm.Option{
+			// Disable black hole detection on autonat dialers
+			// It is better to attempt a dial and fail for AutoNAT use cases
+			swarm.WithUDPBlackHoleConfig(false, 0, 0),
+			swarm.WithIPv6BlackHoleConfig(false, 0, 0),
+		},
 	}
 
 	dialer, err := autoNatCfg.makeSwarm(eventbus.NewBus(), false)

core/network/network.go

@@ -152,6 +152,20 @@ type Network interface {
 	ResourceManager() ResourceManager
 }
 
+// Dialability indicates how dialable a (peer, addr) combination is.
+type Dialability int
+
+const (
+	// DialabilityUnknown indicates that the dialer cannot dial the (peer, addr) combination
+	DialabilityUnknown Dialability = iota
+
+	// DialabilityDialable indicates that the dialer can dial the (peer, addr) combination
+	DialabilityDialable
+
+	// DialabilityUndialable indicates that the dialer cannot dial the (peer, addr) combinaton
+	DialabilityUndialable
+)
+
 // Dialer represents a service that can dial out to peers
 // (this is usually just a Network, but other services may not need the whole
 // stack, and thus it becomes easier to mock)
@@ -186,8 +200,8 @@ type Dialer interface {
 	Notify(Notifiee)
 	StopNotify(Notifiee)
 
-	// CanDial returns whether an address is dialable
-	CanDial(a ma.Multiaddr) bool
+	// CanDial returns whether the dialer can dial peer p at addr
+	CanDial(p peer.ID, addr ma.Multiaddr) Dialability
 }
 
 // AddrDelay provides an address along with the delay after which the address

p2p/net/mock/mock_peernet.go

@@ -435,6 +435,6 @@ func (pn *peernet) ResourceManager() network.ResourceManager {
 	return &network.NullResourceManager{}
 }
 
-func (pn *peernet) CanDial(addr ma.Multiaddr) bool {
-	return true
+func (pn *peernet) CanDial(p peer.ID, addr ma.Multiaddr) network.Dialability {
+	return network.DialabilityUnknown
 }

p2p/net/swarm/black_hole_detector.go

@@ -144,6 +144,13 @@ func (b *blackHoleFilter) updateState() {
 	}
 }
 
+func (b *blackHoleFilter) State() blackHoleState {
+	b.mu.Lock()
+	defer b.mu.Unlock()
+
+	return b.state
+}
+
 func (b *blackHoleFilter) trackMetrics() {
 	if b.metricsTracer == nil {
 		return
@@ -244,6 +251,27 @@ func (d *blackHoleDetector) RecordResult(addr ma.Multiaddr, success bool) {
 	}
 }
 
+func (d *blackHoleDetector) State(addr ma.Multiaddr) blackHoleState {
+	if !manet.IsPublicAddr(addr) {
+		return blackHoleStateAllowed
+	}
+
+	if d.udp != nil && isProtocolAddr(addr, ma.P_UDP) {
+		udpState := d.udp.State()
+		if udpState != blackHoleStateAllowed {
+			return udpState
+		}
+	}
+
+	if d.ipv6 != nil && isProtocolAddr(addr, ma.P_IP6) {
+		ipv6State := d.ipv6.State()
+		if ipv6State != blackHoleStateAllowed {
+			return ipv6State
+		}
+	}
+	return blackHoleStateAllowed
+}
+
 // blackHoleConfig is the config used for black hole detection
 type blackHoleConfig struct {
 	// Enabled enables black hole detection

p2p/net/swarm/black_hole_detector_test.go

@@ -17,6 +17,9 @@ func TestBlackHoleFilterReset(t *testing.T) {
 		if bhf.HandleRequest() != blackHoleResultProbing {
 			t.Fatalf("expected calls up to n to be probes")
 		}
+		if bhf.State() != blackHoleStateProbing {
+			t.Fatalf("expected state to be probing got %s", bhf.State())
+		}
 		bhf.RecordResult(false)
 	}
 
@@ -26,6 +29,9 @@ func TestBlackHoleFilterReset(t *testing.T) {
 		if (i%n == 0 && result != blackHoleResultProbing) || (i%n != 0 && result != blackHoleResultBlocked) {
 			t.Fatalf("expected every nth dial to be a probe")
 		}
+		if bhf.State() != blackHoleStateBlocked {
+			t.Fatalf("expected state to be blocked, got %s", bhf.State())
+		}
 	}
 
 	bhf.RecordResult(true)
@@ -34,12 +40,18 @@ func TestBlackHoleFilterReset(t *testing.T) {
 		if bhf.HandleRequest() != blackHoleResultProbing {
 			t.Fatalf("expected black hole detector state to reset after success")
 		}
+		if bhf.State() != blackHoleStateProbing {
+			t.Fatalf("expected state to be probing got %s", bhf.State())
+		}
 		bhf.RecordResult(false)
 	}
 
 	// next call should be blocked
 	if bhf.HandleRequest() != blackHoleResultBlocked {
 		t.Fatalf("expected dial to be blocked")
+		if bhf.State() != blackHoleStateBlocked {
+			t.Fatalf("expected state to be blocked, got %s", bhf.State())
+		}
 	}
 }
 

p2p/net/swarm/swarm.go

@@ -111,7 +111,7 @@ func WithDialRanker(d network.DialRanker) Option {
 	}
 }
 
-// WithUDPBlackHoleConfig configures swarm to use c as the config for UDP black hole detection
+// WithUDPBlackHoleConfig configures swarm to use the provided config for UDP black hole detection
 // n is the size of the sliding window used to evaluate black hole state
 // min is the minimum number of successes out of n required to not block requests
 func WithUDPBlackHoleConfig(enabled bool, n, min int) Option {
@@ -121,7 +121,7 @@ func WithUDPBlackHoleConfig(enabled bool, n, min int) Option {
 	}
 }
 
-// WithIPv6BlackHoleConfig configures swarm to use c as the config for IPv6 black hole detection
+// WithIPv6BlackHoleConfig configures swarm to use the provided config for IPv6 black hole detection
 // n is the size of the sliding window used to evaluate black hole state
 // min is the minimum number of successes out of n required to not block requests
 func WithIPv6BlackHoleConfig(enabled bool, n, min int) Option {

p2p/net/swarm/swarm_dial.go

@@ -417,9 +417,24 @@ func (s *Swarm) dialNextAddr(ctx context.Context, p peer.ID, addr ma.Multiaddr,
 	return nil
 }
 
-func (s *Swarm) CanDial(addr ma.Multiaddr) bool {
-	t := s.TransportForDialing(addr)
-	return t != nil && t.CanDial(addr)
+func (s *Swarm) CanDial(p peer.ID, addr ma.Multiaddr) network.Dialability {
+	dialable, _ := s.filterKnownUndialables(p, []ma.Multiaddr{addr})
+	if len(dialable) == 0 {
+		return network.DialabilityUndialable
+	}
+
+	bhState := s.bhd.State(addr)
+	switch bhState {
+	case blackHoleStateAllowed:
+		return network.DialabilityDialable
+	case blackHoleStateProbing:
+		return network.DialabilityUnknown
+	case blackHoleStateBlocked:
+		return network.DialabilityUndialable
+	default:
+		log.Errorf("SWARM BUG: unhandled black hole state for dilability check %s", bhState)
+		return network.DialabilityUnknown
+	}
 }
 
 func (s *Swarm) nonProxyAddr(addr ma.Multiaddr) bool {

p2p/protocol/autonatv2/autonat.go

@@ -87,7 +87,9 @@ type AutoNAT struct {
 
 // New returns a new AutoNAT instance. The returned instance runs the server when the provided host
 // is publicly reachable.
-func New(h host.Host, dialer host.Host, opts ...AutoNATOption) (*AutoNAT, error) {
+// host and dialerHost should have the same dialing capabilities. In case the host doesn't support
+// a transport, dial back requests for address for that transport will be ignored.
+func New(host host.Host, dialerHost host.Host, opts ...AutoNATOption) (*AutoNAT, error) {
 	s := defaultSettings()
 	for _, o := range opts {
 		if err := o(s); err != nil {
@@ -108,7 +110,7 @@ func New(h host.Host, dialer host.Host, opts ...AutoNATOption) (*AutoNAT, error)
 	// (https://github.com/libp2p/go-libp2p/issues/2229)(to be implemented in a future release)
 	// to determine reachability using v2 client and send this event from Address Pipeline, if
 	// we are publicly reachable.
-	sub, err := h.EventBus().Subscribe([]interface{}{
+	sub, err := host.EventBus().Subscribe([]interface{}{
 		new(event.EvtLocalReachabilityChanged),
 		new(event.EvtPeerProtocolsUpdated),
 		new(event.EvtPeerConnectednessChanged),
@@ -120,12 +122,12 @@ func New(h host.Host, dialer host.Host, opts ...AutoNATOption) (*AutoNAT, error)
 
 	ctx, cancel := context.WithCancel(context.Background())
 	an := &AutoNAT{
-		host:          h,
+		host:          host,
 		ctx:           ctx,
 		cancel:        cancel,
 		sub:           sub,
-		srv:           newServer(h, dialer, s),
-		cli:           newClient(h),
+		srv:           newServer(host, dialerHost, s),
+		cli:           newClient(host),
 		allowAllAddrs: s.allowAllAddrs,
 		peers:         newPeersMap(),
 	}

p2p/protocol/autonatv2/server.go

@@ -23,6 +23,9 @@ type dataRequestPolicyFunc = func(s network.Stream, dialAddr ma.Multiaddr) bool
 // server implements the AutoNATv2 server.
 // It can ask client to provide dial data before attempting the requested dial.
 // It rate limits requests on a global level, per peer level and on whether the request requires dial data.
+//
+// This uses the host's dialer as well as the dialerHost's dialer to determine whether an address is
+// dialable.
 type server struct {
 	host       host.Host
 	dialerHost host.Host
@@ -112,7 +115,13 @@ func (as *server) handleDialRequest(s network.Stream) {
 			continue
 		}
 		if (!as.allowAllAddrs && !manet.IsPublicAddr(a)) ||
-			(!as.dialerHost.Network().CanDial(a)) {
+			(as.dialerHost.Network().CanDial(p, a) != network.DialabilityDialable) {
+			continue
+		}
+		// Check if the host can dial the address. This check ensures that we do not
+		// attempt dialing an IPv6 address if we have no IPv6 connectivity as the host dialer's
+		// black hole detector is likely to be more accurate.
+		if as.host.Network().CanDial(p, a) != network.DialabilityDialable {
 			continue
 		}
 		dialAddr = a