Lightning Specification Meeting 2023/03/13

[t-bast]

The meeting will take place on Monday 2023/03/13 at 7pm UTC (5:30am Adelaide time) on Libera Chat IRC #lightning-dev. It is open to the public.

A video link is available for higher bandwidth communication: https://meet.jit.si/Lightning-Spec-Meeting

Recently Updated Proposals / Seeking Review

This section contains changes that have been opened or updated recently and need feedback from the meeting participants.

• Dual funding interactive-tx: Add dual-funding flow, using the interactive tx protocol (feature 28/29) #851
• Route blinding Route Blinding (Feature 24/25) #765
• Add dust exposure threshold Add a max_dust_htlc_exposure_msat #919
• Onion messages BOLT 7: Onion message support (features 38/39) #759
• Offers Offers #798
• Taproot extension-bolt: simple taproot channels (feature 80/81) #995
• Fat errors Attributable errors (feature 36/37) #1044
• Splicing Splice draft (feature 62/63) #863
• Clarify channel_reestablish requirements Clarify channel_reestablish requirements #1049 or Rework channel_reestablish requirements #1051
• Peer storage backup Peer backup storage (feature 40/41/42/43) #881

Stale Proposals

This section contains pending changes that may not need feedback from the meeting participants, unless someone explicitly asks for it during the meeting. These changes are usually waiting for implementation work to happen to drive more feedback.

• Inbound fees Inbound routing fees blips#18 and Add a bLIP for backwards-compatible inbound fees blips#22
• Closing fee range turn-based protocol option_closing_rejected: turn-based fee_range coop close (feature 60/61) #1016
• Update static channel parameters zzz-extension-bolt: dynamic commitments #1026
• Liquidity ads option_will_fund: liquidity ads #878
• Sign commitments at various feerates Add option to sign commitments at various feerates (FEAT 32/33) #1036

Waiting for interop

This section contains changes that have been conceptually ACKed and are waiting for at least two implementations to fully interoperate.
They most likely don't need to be covered during the meeting, unless someone asks for updates.

• Don't force close until error is received after channel_reestablish Nodes shouldn't publish their commitment when receiving outdated channel_reestablish #934
• Websocket transport websocket address type: allow transport over RFC6455 #891

Long Term Updates

This section contains long-term changes that need review, but require a substantial implementation effort.

• Channel jamming draft: Staking Credentials token issuance/redemption #1043 draft: Upfront Fees to Mitigate Channel Jamming #1052
• Pinning attacks as related to splicing / dynamic commitments: https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-August/003665.html
• Quiescence BOLT 2: quiescence protocol (feature 34/35) option_quiesce #869
• Simplified commitment Feature 106/107: option_simplified_update. #867
• Hold htlcs before forwarding Add the ability to hold HTLCs before forwarding (FEAT 52/53) #989
• Trampoline routing Trampoline Routing (2021 edition) (Feature 56/57) #829 and Trampoline onion format (Feature 56/57) #836
• Anonymous gossip
• lnprototest (https://github.com/rustyrussell/lnprototest)

[t-bast]

I won't be able to attend this spec meeting, I'll be traveling at that time.

On route blinding, I'd like feedback from the crowd on this comment: should this feature bit be marked as an invoice feature bit or not? It is conceptually an invoice feature, so it bothers me a bit to only mark it IN, even though nobody plans on supporting route blinding with Bolt 11 invoices for now.

On dual funding, we have found an issue with how interactive-tx is used (actually more of an issue for splicing, but we believe we should fix it for dual funding as well). The issue is described here, and I'd like feedback from other implementers on this before we merge the dual funding PR, as I think it would improve dual funding (in a backwards-incompatible way) if we fix this.

[Roasbeef]

Won't be able to attend due to a conflict, so here're some updates on my end:

• The last PR in the taproot saga for lnd is up. This covers all the on-chain logic (HTLC redemption, breaches, second level handling, etc). From here on we'll be adding more unit and integration tests, to increase confidence in all the new code.
  • I need to update the spec in response to comments, and also add in those script changes mentioned a few meetings ago (my PR above was pinned to the spec snapshot so I could have a static target).
  • We're still in a waiting-for-interop holding pattern.
• We've started to explore the design space for "Gossip 1.5" (gateway drug to PLTCs, needed so taproot chans can be advertised. @ellemouton has posted a public spec draft here: https://github.com/ellemouton/bolts/pull/2/files -- mostly in place, but a few open questions and other things to be filled in.
  • The most immediate effect here is that we need yet-another-set-of-nonces to be able to sign the announcement_signatures_2 message. Open question here is: where should we piggy back this? In the normal chan open message, or later in funding_locked/chanel_ready?
• We've done more exploration re a dynamic commitments carve out to aide in upgrade to taproot chans, but no concrete updates here beyond the existing draft spec PR (tho that only does params like max_htlc and needs to be updated to handle the new off-chain layer of indirection to go from segwit v0 to v1).

[carlaKC]

Transcript: bitcointranscripts/bitcointranscripts#236