[#522] network: Fix issue with empty endpoint in multiaddr

Before fix `:8080` host address was parsed as `/dns4/tcp/8080`
multiaddress. However such multiaddress is not correct. In this
case `dns4` section should be omitted, but it breaks `manet.DialArgs`.

To solve this issue we explicitly set 0.0.0.0 address.

Signed-off-by: Alex Vanin <alexey@nspcc.ru>

pkg/network/address.go

@@ -83,6 +83,13 @@ func multiaddrStringFromHostAddr(host string) (string, error) {
 		return "", err
 	}
 
+	// Empty address in host `:8080` generates `/dns4//tcp/8080` multiaddr
+	// which is invalid. It could be `/tcp/8080` but this breaks
+	// `manet.DialArgs`. The solution is to manually parse it as 0.0.0.0
+	if endpoint == "" {
+		return "/ip4/0.0.0.0/tcp/" + port, nil
+	}
+
 	var (
 		prefix = "/dns4"
 		addr   = endpoint

pkg/network/address_test.go

@@ -29,6 +29,26 @@ func TestAddress_NetAddr(t *testing.T) {
 	require.Equal(t, ip+":"+port, netAddr)
 }
 
+func TestAddressFromString(t *testing.T) {
+	t.Run("valid addresses", func(t *testing.T) {
+		testcases := []struct {
+			inp string
+			exp multiaddr.Multiaddr
+		}{
+			{":8080", buildMultiaddr("/ip4/0.0.0.0/tcp/8080", t)},
+			{"example.com:7070", buildMultiaddr("/dns4/example.com/tcp/7070", t)},
+			{"213.44.87.1:32512", buildMultiaddr("/ip4/213.44.87.1/tcp/32512", t)},
+			{"[2004:eb1::1]:8080", buildMultiaddr("/ip6/2004:eb1::1/tcp/8080", t)},
+		}
+
+		for _, testcase := range testcases {
+			addr, err := AddressFromString(testcase.inp)
+			require.NoError(t, err)
+			require.Equal(t, testcase.exp, addr.ma, testcase.inp)
+		}
+	})
+}
+
 func TestAddress_HostAddrString(t *testing.T) {
 	t.Run("valid addresses", func(t *testing.T) {
 		testcases := []struct {