add a function to convert a IP:port string to a WebTransport multiaddr

p2p/transport/webtransport/multiaddr.go

@@ -3,6 +3,7 @@ package libp2pwebtransport
 import (
 	"errors"
 	"net"
+	"strconv"
 
 	ma "github.com/multiformats/go-multiaddr"
 	mafmt "github.com/multiformats/go-multiaddr-fmt"
@@ -23,3 +24,19 @@ func toWebtransportMultiaddr(na net.Addr) (ma.Multiaddr, error) {
 	}
 	return addr.Encapsulate(webtransportMA), nil
 }
+
+func stringToWebtransportMultiaddr(str string) (ma.Multiaddr, error) {
+	host, portStr, err := net.SplitHostPort(str)
+	if err != nil {
+		return nil, err
+	}
+	port, err := strconv.ParseInt(portStr, 10, 32)
+	if err != nil {
+		return nil, err
+	}
+	ip := net.ParseIP(host)
+	if ip == nil {
+		return nil, errors.New("failed to parse IP")
+	}
+	return toWebtransportMultiaddr(&net.UDPAddr{IP: ip, Port: int(port)})
+}

p2p/transport/webtransport/multiaddr_test.go

@@ -19,3 +19,23 @@ func TestWebtransportMultiaddr(t *testing.T) {
 		require.EqualError(t, err, "not a UDP address")
 	})
 }
+
+func TestWebtransportMultiaddrFromString(t *testing.T) {
+	t.Run("valid", func(t *testing.T) {
+		addr, err := stringToWebtransportMultiaddr("1.2.3.4:60042")
+		require.NoError(t, err)
+		require.Equal(t, "/ip4/1.2.3.4/udp/60042/quic/webtransport", addr.String())
+	})
+
+	t.Run("invalid", func(t *testing.T) {
+		for _, addr := range [...]string{
+			"1.2.3.4",        // missing port
+			"1.2.3.4:123456", // invalid port
+			":1234",          // missing IP
+			"foobar",
+		} {
+			_, err := stringToWebtransportMultiaddr(addr)
+			require.Error(t, err)
+		}
+	})
+}