Lightning Specification Meeting 2022/08/15

[t-bast]

The meeting will take place on Monday 2022/08/15 at 8pm 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

Pull Request Review

• Clarify bolt 4 blinding Bolt4: clarify packet forwarding blinding #1012
• Channel update pruning clarification: Clarify Bolt 7 latest channel update pruning #1014
• Channel update flags BOLT #7: Make channel_update always have htlc_maximum_msat. #996 or Bolt7: add channel update flag for scid alias #999
• Grace period for channel closes gossip: delay considering a channel edge deleted for 12-blocks #1004
• Closing fee range turn-based protocol option_closing_rejected: turn-based fee_range coop close (feature 60/61) #1016
• Route blinding Route Blinding (Feature 24/25) #765
• Onion messages BOLT 7: Onion message support (features 38/39) #759
• Offers Offers #798
• Add dust exposure threshold Add a max_dust_htlc_exposure_msat #919
• Taproot extension-bolt: simple taproot channels (feature 80/81) #995

Waiting for interop

• Dual funding interactive-tx: Add dual-funding flow, using the interactive tx protocol (feature 28/29) #851
• Don't force close until error is received after channel_reestablish Nodes shouldn't publish their commitment when receiving outdated channel_reestablish #934
• Graph dump on gossip_timestamp_filter Inconsistent behavior around graph dump on gossip_timestamp_filter. #980
• Handle update_fee during shutdown BOLT 2: forget the check about update_* messages, and check what must not happens during shutdown #972
• Websocket transport websocket address type: allow transport over RFC6455 #891

Long Term Updates

• Pinning attacks as related to splicing / dynamic commitments: https://lists.linuxfoundation.org/pipermail/lightning-dev/2022-August/003665.html
• Liquidity ads option_will_fund: liquidity ads #878
• Splicing Splice draft (feature 62/63) #863
• 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
• Upfront payments / DoS protection Hold fees #843
• Peer storage backup Peer backup storage (feature 40/41/42/43) #881
• Anonymous gossip

Backlog

The following are topics that we should discuss at some point, so if we have time to discuss them great, otherwise they slip to the next meeting.

• lnprototest (https://github.com/rustyrussell/lnprototest)

[Roasbeef]

Co-op close commentary: #1016 (comment)

[Roasbeef]

Route blinding commentary:

• Originally: mug all errors, turn it into a different error (very opaque)
• More recent ideas: ideally we can propagate well formed errors that are useful (mpp timeout, etc). Important that the error needs to be wrapped in the blinded key rather than your actual key
• Now wrangling the wording in the spec, with the test vectors updated as well.
• CL has updated code, works w/ the test vectors. Now working on doing an e2e test w/ blinded paths for payments
• Future requests: want a persistent fake identity for the final hop as well? Something to be done in the future potentially.
• Blinded payments now also compulsory for BOLT 12, you want to also supply one even if you don't need it. Gives you sort of mandatory payment secrets

[Roasbeef]

Offers commentary:

• Right now you ignore certain numbered fields that store signatures, or are included in signatures
• Some want to have two distinct streams: one stream for the things hashed, and another stream for the sigs
• Might want to add some more distinct layers, some feel like it can be inefficient

[Roasbeef]

web sockets commentary (#891):

• Host name merged in now. Turns out web sockets must always be HTTPs for browsers, so you need a cert, which means you need a host name.
• Now seems we want a new explicit type, to indicate it's web sockets only, with maybe also a bit to set if TLS is required or not. So this would sort of copy over the DNS field information.
• CL supports websockets w/o TLS (can't be accessed from a browser), cuz ppl use JS in weird places

[Roasbeef]

dual funding (#851):

• CL uses anchor outputs always, eclair has implemented but doesn't always have anchors
• related threads re splicing and pinning stuff above

splicing:

• rule 3 for RBF is bad, messes up your bid dynamics
• there're full rbf ppl now, but that just means you don't need to signal
• RBF maximalists want to just destroy the whole thing and replace if you bid higher or not
• new version of package RBF w/ a new tx version: policy: nVersion=3 and Package RBF bitcoin/bitcoin#25038

edit: eclair has already fully implemented dual funding

[niftynei]

CL uses anchor outputs always, eclair starting to implement but doesn't always have anchors

eclair has implemented fwiw! "Dual funding PRs are being merged to master (#2247, #2273, #2274, #2275)"

[t-bast]

Thanks for the summary @Roasbeef, much appreciated!