`ChannelManager::accept_inbound_channel` doesn't reject channel on error

[mhrheaume]

Recently when running a testnet node with manually_accept_inbound_channels, I encountered the following error when calling accept_inbound_channel_from_trusted_peer_0conf:

Funding amount (287084 sats) can't even pay fee for initial commitment transaction fee of 415006 sats.

This is a reasonable error to return in this scenario, but I was surprised to learn that we don't actually send an error to the peer in this case, which leaves the peer hanging until one of the nodes times out. Other errors in accept_inbound_channel_from_trusted_peer_0conf will send an error to the peer and reject the channel.

IMO we should either:

1. Reject the channel any time there is an error in accept_inbound_channel.
2. In the Err returned by accept_inbound_channel, return some indication for whether or not the channel was rejected, so that the caller can determine whether they want to reject the channel or retry accepting with different parameters.

[shaavan]

Hi @mhrheaume!

Thanks for pointing this out—I looked into the codebase to see if I could confirm the issue.

To do this, I created a branch with a test that simulates how the code behaves in this situation. You can find it here: branch, commit.

While testing, I found that our node does send an error to the peer when the "Funding amount is insufficient..." message is triggered. This makes me think the issue might not be with the LDK codebase itself—could it be something else in your setup?

I’ve documented the test so you can run it yourself and see if it matches the scenario you’re working with. Let me know how it goes or if I can help further!
Thanks!