[bug]: LND-CLN err=update_fee XXXXXX unaffordable

[Impa10r]

Background

Running an LND node, have a non-anchor channel with a CLN peer. After the chain fees jumped, the two nodes can no longer maintain connection: state update from LND causes CLN to reply with warning "err=update_fee XXXXXX unaffordable" and hang up. A pending HTLC is at risk to cause an FC.

Log from my side:

2024-04-22 18:18:24.550 [INF] HSWC: ChannelLink(bf4d148a934a62fd02df33a0f57bb2d07bce16c45f37d4feb21f8acda6b529a3:3): Attempting to re-synchronize channel: SCID=827627:1245:3, status=ChanStatusDefault, initiator=true, pending=false, local commitment has height=32100, local_htlc_index=14878, local_log_index=16976, remote_htlc_index=330, remote_log_index=15207, remote commitment has height=32111, local_htlc_index=14878, local_log_index=16976, remote_htlc_index=330, remote_log_index=15207
2024-04-22 18:18:24.781 [INF] HSWC: ChannelLink(bf4d148a934a62fd02df33a0f57bb2d07bce16c45f37d4feb21f8acda6b529a3:3): received re-establishment message from remote side
2024-04-22 18:18:24.782 [INF] DISC: GossipSyncer(031633471d005f37252ede8114c6f4203e0a668270532f0f11a1e4072eb2eef272): applying new update horizon: start=2106-02-07 06:28:15 +0000 UTC, end=2242-03-16 12:56:30 +0000 UTC, backlog_size=0
2024-04-22 18:18:27.752 [INF] HSWC: ChannelLink(bf4d148a934a62fd02df33a0f57bb2d07bce16c45f37d4feb21f8acda6b529a3:3): sending 2 updates to synchronize the state
2024-04-22 18:18:28.006 [WRN] HSWC: ChannelLink(bf4d148a934a62fd02df33a0f57bb2d07bce16c45f37d4feb21f8acda6b529a3:3): received warning message from peer: chan_id=a329b5a6cd8a1fb2fed4375fc416ce7bd0b27bf5a033df02fd624a938a144dbc, err=update_fee 448000 unaffordable
2024-04-22 18:18:28.029 [INF] PEER: Peer(031633471d005f37252ede8114c6f4203e0a668270532f0f11a1e4072eb2eef272): unable to read message from peer: read next header: EOF
2024-04-22 18:18:28.029 [INF] PEER: Peer(031633471d005f37252ede8114c6f4203e0a668270532f0f11a1e4072eb2eef272): disconnecting

On CLN side:

"status": [
                  "CHANNELD_NORMAL:update_fee 448000 unaffordable",
                  "CHANNELD_NORMAL:Will attempt reconnect in 300 seconds"
               ],

The error persists since the halving and the update fee stays at 448000.

Your environment

• version of lnd LND 0.17.4-beta
• which operating system (uname -a on *Nix) Umbrel
• version of btcd, bitcoind, or other backend Bitcoin Core 26.0.0
• any other relevant environment details

Steps to reproduce

Chain fees go to 1000+ then back to 100+

Expected behaviour

The channel between nodes continue to work

Actual behaviour

The channel between nodes keeps disconnecting

I reported to both CLN and LND devs, but no one wants to take responsibility for this bug...

[saubyk]

This appears to be a duplicate of https://github.com/lightningnetwork/lnd/issues/7756 Has been fixed with https://github.com/lightningnetwork/lnd/pull/7805

Will be available with 0.18

[Impa10r]

This appears to be a duplicate of #7756 Has been fixed with #7805

Will be available with 0.18

Anything I can do today to avoid expensive FC?

[saubyk]

cc @ziggie1984 in case he has any ideas

[ziggie1984]

The only way for this to recover is to wait until fees go down, or ask your CLN node to run a setting which discards the fee check.

CLN Setting:

--ignore-fee-limits=BOOL

[JaviLib]

The only way for this to recover is to wait until fees go down, or ask your CLN node to run a setting which discards the fee check.

CLN Setting:

--ignore-fee-limits=BOOL

I'm been told in the Telegram group that modifying this setting doesn't help. Is that right?

[Impa10r]

The only way for this to recover is to wait until fees go down, or ask your CLN node to run a setting which discards the fee check.

CLN Setting:

--ignore-fee-limits=BOOL

My CLN peer says he tried running with that setting. Fees at 100 are not that high. I use feeurl to feed more realistic estimates, not bitcoin core. Maybe CLN gets too high estimates (my bitcoin core thinks the fees are 1150 still), because they don't have such a setting.

[JaviLib]

CLN related bug: https://github.com/ElementsProject/lightning/issues/7254

[ziggie1984]

From CLN Docs:

ignore-fee-limits=BOOL

Allow nodes which establish channels to us to set any fee they want. This may result in a channel which cannot be closed, should fees increase, but make channels far more reliable since we never close it due to unreasonable fees. Note that this can be set on a per-channel basis with lightning-setchannel(7).

see: https://github.com/ElementsProject/lightning/blob/master/doc/lightningd-config.5.md

[Impa10r]

From CLN Docs:

ignore-fee-limits=BOOL

Allow nodes which establish channels to us to set any fee they want. This may result in a channel which cannot be closed, should fees increase, but make channels far more reliable since we never close it due to unreasonable fees. Note that this can be set on a per-channel basis with lightning-setchannel(7).

see: https://github.com/ElementsProject/lightning/blob/master/doc/lightningd-config.5.md

Made no difference, same error ((

[ziggie1984]

Can you report detailed logs of both nodes while this setting is active.

[Roasbeef]

Asked for some node details here: https://github.com/ElementsProject/lightning/issues/7254#issuecomment-2073832114

[Impa10r]

Can you report detailed logs of both nodes while this setting is active.

My CLN peer did not send me his logs. My LND logs did not show anything different. The HTLC just expired and the channel FCd (((

[JaviLib]

Asked for some node details here: ElementsProject/lightning#7254 (comment)

I answered you there: https://github.com/ElementsProject/lightning/issues/7254#issuecomment-2076920748

BTW I think we may have found another related bug in LND: when feeurl cannot be retrived, it seems it defaults to 253sat/kw, which is ridiculous. This might be the problem, plus unable to renegotiate with CLN once the new low fee is stablished.

I will open another issue.