funding: don't negotiate on known types

funding/commitment_type_negotiation.go

@@ -8,12 +8,6 @@ import (
 )
 
 var (
-	// errUnsupportedExplicitNegotiation is an error returned when explicit
-	// channel commitment negotiation is attempted but either peer of the
-	// channel does not support it.
-	errUnsupportedExplicitNegotiation = errors.New("explicit channel " +
-		"type negotiation not supported")
-
 	// errUnsupportedCommitmentType is an error returned when a specific
 	// channel commitment type is being explicitly negotiated but either
 	// peer of the channel does not support it.
@@ -29,12 +23,13 @@ func negotiateCommitmentType(channelType *lnwire.ChannelType,
 	local, remote *lnwire.FeatureVector) (lnwallet.CommitmentType, error) {
 
 	if channelType != nil {
-		if !hasFeatures(local, remote, lnwire.ExplicitChannelTypeOptional) {
-			return 0, errUnsupportedExplicitNegotiation
+		// If the peer does know explicit negotiation, let's attempt
+		// that now.
+		if hasFeatures(local, remote, lnwire.ExplicitChannelTypeOptional) {
+			return explicitNegotiateCommitmentType(
+				*channelType, local, remote,
+			)
 		}
-		return explicitNegotiateCommitmentType(
-			*channelType, local, remote,
-		)
 	}
 
 	return implicitNegotiateCommitmentType(local, remote), nil

funding/commitment_type_negotiation_test.go

@@ -36,7 +36,8 @@ func TestCommitmentTypeNegotiation(t *testing.T) {
 				lnwire.StaticRemoteKeyOptional,
 				lnwire.AnchorsZeroFeeHtlcTxOptional,
 			),
-			expectsErr: errUnsupportedExplicitNegotiation,
+			expectsRes: lnwallet.CommitmentTypeAnchorsZeroFeeHtlcTx,
+			expectsErr: nil,
 		},
 		{
 			name: "explicit missing remote commitment feature",
@@ -181,8 +182,14 @@ func TestCommitmentTypeNegotiation(t *testing.T) {
 				return
 			}
 
-			require.Equal(t, testCase.expectsRes, localType)
-			require.Equal(t, testCase.expectsRes, remoteType)
+			require.Equal(
+				t, testCase.expectsRes, localType,
+				testCase.name,
+			)
+			require.Equal(
+				t, testCase.expectsRes, remoteType,
+				testCase.name,
+			)
 		})
 		if !ok {
 			return