feature request: let `lncli stop` wait until there are no HTLCs pending

[antonilol]

Background

Describe your issue here.

imagine i stoppen lnd with lncli stop but there was a pending HTLC in one of the channels, when the remote party wants to fulfill it, it cant so force closes the channel.

Your environment

• version of lnd lnd version 0.14.2-beta commit=v0.14.2-beta
• which operating system (uname -a on *Nix) Linux 5600g 5.17.2-arch3-1 #1 SMP PREEMPT Sun, 10 Apr 2022 11:18:32 +0000 x86_64 GNU/Linux
• version of btcd, bitcoind, or other backend
• any other relevant environment details

Steps to reproduce

Tell us how to reproduce this issue. Please provide stacktraces and links to code in question.

not really a bug, but lncli stop when a channel has a pending HTLC the other can fulfill and it will force close to fulfill it on chain

Feature request:

an rpc and lncli argument to lncli stop to let it wait until all channels are 'clean'

[alexbosworth]

you can use the HtlcInterceptor API to start refusing HTLCs before shutdown. Another mitigation here could be to increase your CLTV delta if you are simply restarting and don't have enough time to complete a restart. If you are bringing your node down for more extended periods of time, you can minimize HTLC attachment by making private channels. A normal lncli stop wouldn't result in force closed channels even with attached HTLCs, so long as you are able to restart within a reasonable amount of time.