diff --git a/lnwallet/channel.go b/lnwallet/channel.go index 1301d83f..56991bd3 100644 --- a/lnwallet/channel.go +++ b/lnwallet/channel.go @@ -4940,13 +4940,22 @@ func (lc *LightningChannel) MayAddOutgoingHtlc() error { lc.Lock() defer lc.Unlock() + // As this is a mock HTLC, we'll attempt to add the smallest possible + // HTLC permitted in the channel. However certain implementations may + // set this value to zero, so we'll catch that and increment things so + // we always use a non-zero value. + mockHtlcAmt := lc.channelState.LocalChanCfg.MinHTLC + if mockHtlcAmt == 0 { + mockHtlcAmt++ + } + // Create a "mock" outgoing htlc, using the smallest amount we can add // to the commitment so that we validate commitment slots rather than // available balance, since our actual htlc amount is unknown at this // stage. pd := lc.htlcAddDescriptor( &lnwire.UpdateAddHTLC{ - Amount: lc.channelState.LocalChanCfg.MinHTLC, + Amount: mockHtlcAmt, }, &channeldb.CircuitKey{}, ) diff --git a/lnwallet/channel_test.go b/lnwallet/channel_test.go index 6de8b2ac..6f190ade 100644 --- a/lnwallet/channel_test.go +++ b/lnwallet/channel_test.go @@ -9648,3 +9648,24 @@ func TestChannelSignedAckRegression(t *testing.T) { err = aliceChannel.ReceiveNewCommitment(bobSig, bobHtlcSigs) require.NoError(t, err) } + +// TestMayAddOutgoingHtlcZeroValue tests that if the minHTLC value of the +// channel is zero, then the MayAddOutgoingHtlc doesn't exit early due to +// running into a zero valued HTLC. +func TestMayAddOutgoingHtlcZeroValue(t *testing.T) { + t.Parallel() + + // The default channel created as a part of the test fixture already + // has a MinHTLC value of zero, so we don't need to do anything here + // other than create it. + aliceChannel, bobChannel, cleanUp, err := CreateTestChannels( + channeldb.SingleFunderTweaklessBit, + ) + require.NoError(t, err) + defer cleanUp() + + // The channels start out with a 50/50 balance, so both sides should be + // able to add an outgoing HTLC. + require.NoError(t, aliceChannel.MayAddOutgoingHtlc()) + require.NoError(t, bobChannel.MayAddOutgoingHtlc()) +}