tighten multiaddr conversion logic

p2p/transport/webtransport/multiaddr.go

@@ -1,6 +1,7 @@
 package libp2pwebtransport
 
 import (
+	"errors"
 	"net"
 
 	ma "github.com/multiformats/go-multiaddr"
@@ -13,9 +14,12 @@ var webtransportMA = ma.StringCast("/quic/webtransport")
 var webtransportMatcher = mafmt.And(mafmt.IP, mafmt.Base(ma.P_UDP), mafmt.Base(ma.P_QUIC), mafmt.Base(ma.P_WEBTRANSPORT))
 
 func toWebtransportMultiaddr(na net.Addr) (ma.Multiaddr, error) {
-	udpMA, err := manet.FromNetAddr(na)
+	addr, err := manet.FromNetAddr(na)
 	if err != nil {
 		return nil, err
 	}
-	return udpMA.Encapsulate(webtransportMA), nil
+	if _, err := addr.ValueForProtocol(ma.P_UDP); err != nil {
+		return nil, errors.New("not a UDP address")
+	}
+	return addr.Encapsulate(webtransportMA), nil
 }

p2p/transport/webtransport/multiaddr_test.go

@@ -0,0 +1,21 @@
+package libp2pwebtransport
+
+import (
+	"net"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestWebtransportMultiaddr(t *testing.T) {
+	t.Run("valid", func(t *testing.T) {
+		addr, err := toWebtransportMultiaddr(&net.UDPAddr{IP: net.IPv4(127, 0, 0, 1), Port: 1337})
+		require.NoError(t, err)
+		require.Equal(t, "/ip4/127.0.0.1/udp/1337/quic/webtransport", addr.String())
+	})
+
+	t.Run("invalid", func(t *testing.T) {
+		_, err := toWebtransportMultiaddr(&net.TCPAddr{IP: net.IPv4(127, 0, 0, 1), Port: 1337})
+		require.EqualError(t, err, "not a UDP address")
+	})
+}