Peer storage

[thomash-acinq]

Implements lightning/bolts#1110

[t-bast]

I thought this was an easy PR, but as I dived into it I think there are many subtle aspects that have a big impact on scenarios where users restore from seed. That's why I have multiple comments that aren't trivial, for which we need to decide how we'd like eclair to behave.

[codecov-commenter]

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Codecov Report

Attention: Patch coverage is 73.07692% with 35 lines in your changes missing coverage. Please review.

Project coverage is 86.03%. Comparing base (5410146) to head (df24044).
Report is 15 commits behind head on master.

Files with missing lines	Patch %	Lines
...-core/src/main/scala/fr/acinq/eclair/io/Peer.scala	67.50%	13 Missing ⚠️
.../main/scala/fr/acinq/eclair/db/DualDatabases.scala	0.00%	6 Missing ⚠️
...cala/fr/acinq/eclair/db/sqlite/SqlitePeersDb.scala	81.81%	6 Missing ⚠️
.../scala/fr/acinq/eclair/db/PeerStorageCleaner.scala	0.00%	5 Missing ⚠️
...c/main/scala/fr/acinq/eclair/db/pg/PgPeersDb.scala	86.66%	4 Missing ⚠️
...ir-core/src/main/scala/fr/acinq/eclair/Setup.scala	50.00%	1 Missing ⚠️

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Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2888      +/-   ##
==========================================
- Coverage   86.19%   86.03%   -0.16%     
==========================================
  Files         224      227       +3     
  Lines       20074    20276     +202     
  Branches      813      826      +13     
==========================================
+ Hits        17302    17445     +143     
- Misses       2772     2831      +59     

Files with missing lines	Coverage Δ
...core/src/main/scala/fr/acinq/eclair/Features.scala	100.00% <100.00%> (ø)
...re/src/main/scala/fr/acinq/eclair/NodeParams.scala	91.82% <100.00%> (+0.09%)	⬆️
.../eclair/wire/protocol/LightningMessageCodecs.scala	99.47% <100.00%> (+0.01%)	⬆️
...q/eclair/wire/protocol/LightningMessageTypes.scala	99.14% <ø> (ø)
...fr/acinq/eclair/wire/protocol/PeerStorageTlv.scala	100.00% <100.00%> (ø)
...ir-core/src/main/scala/fr/acinq/eclair/Setup.scala	75.00% <50.00%> (-0.30%)	⬇️
...c/main/scala/fr/acinq/eclair/db/pg/PgPeersDb.scala	85.86% <86.66%> (+0.15%)	⬆️
.../scala/fr/acinq/eclair/db/PeerStorageCleaner.scala	0.00% <0.00%> (ø)
.../main/scala/fr/acinq/eclair/db/DualDatabases.scala	9.60% <0.00%> (-0.34%)	⬇️
...cala/fr/acinq/eclair/db/sqlite/SqlitePeersDb.scala	89.65% <81.81%> (-3.21%)	⬇️
... and 1 more

... and 12 files with indirect coverage changes

[t-bast]

I'm a bit afraid of the DoS risks associated with this feature: our node will be a very likely target (everyone will want to store some data with us), so we must be very careful that this cannot be exploited.

[t-bast]

Thanks for the back and forth, it all looks safe to me now (after the couple of changes from my follow-up PR).

What's the status for the other implementations? Can you check and test basic cross-compatibility (by sending a peer_storage_store message from a modified eclair and verifying whether it's correctly returned to us on reconnection)? We'd need to check this before merging it since the spec PR hasn't been merged yet. I'll ping the other implementers during the next spec meeting to see if we can merge.

[thomash-acinq]

Thanks, I've added your fixes. I'll look at the other implementations and do some compat tests.

[thomash-acinq]

I've found pending PRs to implement it in LND (lightningnetwork/lnd#8490) and LDK (lightningdevkit/rust-lightning#2943) but they don't seem to be ready yet.

[t-bast]

Indeed, that doesn't seem to be ready at all! But IIRC cln should already have support merged to their master branch that we can test against?

[t-bast]

@thomash-acinq I asked during the spec meeting, and cln has support for peer storage on their master branch. You simply need to enable experimental features, and cln will automatically send us a small blob for storage and will store ours. You should be able to work on interop tests based on this.

[thomash-acinq]

There doesn't seem to be any progress with LND or LDK but it works with CLN (they just send their blob too early but I'm assuming it's just to test, and they store our blob well).
I've also rebased to fix a conflict.

[t-bast]

they just send their blob too early

What do you mean exactly here, when do they send it? Is it worth opening an issue on their repository?

[thomash-acinq]

I've opened an issue on their repository: ElementsProject/lightning#7931

[t-bast]

Thanks, let's wait for the result of that discussion before merging. I'll raise it during the next spec meeting as well.

[thomash-acinq]

I've changed a bit our behavior to accept peer storage updates from peers without an active channel but not persist it. If a channel becomes active, we then persist it.

[t-bast]

Good idea, with that change I believe we can merge right now to our master branch. We'll wait for the spec PR to be merged to the BOLTs before merging the lightning-kmp PR though, because at that point we would be screwed if we shipped Phoenix using this and the spec changed afterwards, but I hope the spec shouldn't take too long to be added to the BOLTs now that we have cross-compatibility with cln.