Prevent force closing channels with fee rate/conf target

[LNBIG-COM]

Background

When i use lnd API for force-closing of channel with target_conf: 36 i see that LND makes transaction with big fee (as target_conf would be 1-2 only).

Your environment

• version of lnd 0.6.1-beta commit=v0.6.1-beta-rc2
• which operating system (uname -a on *Nix) CentOS
• version of btcd, bitcoind, or other backend - 0.17.1

Actual behaviour

For example i do (node.js):

CloseChannel({ channel_point: { funding_txid_str: 'cfcf31ce231918fb69b36c64345b424cd3aa9b2ef38e32160ffa7ed1b58a1082', output_index: 1 }, force: true, target_conf: 36 })

In that time at target bitcoin node i have a fee for 36 blocks as:

$ bitcoin-cli estimatesmartfee 36
{
  "feerate": 0.00011096,
  "blocks": 36
}

So it's about 11 sat/byte

But after the LND does this transaction:

https://www.smartbit.com.au/tx/ee9cac6a8cfed7a37f8929794fe3b21daf781d06b7541b093a399d9a4a66e549

There is 133 sat/byte. I’m sure that in this case the LND does not explicitly follow the target_conf

And i see many same cases now (i did some force closings and checked them)

[wpaulino]

This is the expected behavior. Force closed channels have pre-negotiated closing fees that happen every so often to ensure it can get into the chain at any given point. This will change in the protocol with lightning/bolts#513.

[cfromknecht]

@wpaulino given that this mixup has happened previously, perhaps we should reopen the issue with the goal of having lncli return an immediate failure when trying to force close with a non-zero conf target or fee rate

[wpaulino]

SGTM.