* Rewrite tendermint's message handling loop to much more clearly match the paper
No longer checks relevant branches upon messages, yet all branches upon any
state change. This is slower, yet easier to review and likely without one or
two rare edge cases.
When reviewing, please see page 5 of https://arxiv.org/pdf/1807.04938.pdf.
Lines from the specified algorithm can be found in the code by searching for
"// L".
* Sane rebroadcasting of consensus messages
Instead of broadcasting the last n messages on the Tributary side of things, we
now have the machine rebroadcast the message tape for the current block.
* Only rebroadcast messages which didn't error in some way
* Only rebroadcast our own messages for tendermint
Instead of saving, for every sent message, if it was sent or not, we track the
latest block/round participated in. These two keys are comprehensive to all
prior block/rounds. We then use three keys for the latest round's
proposal/prevote/precommit, enabling tracking current state as necessary to
prevent equivocations with just 5 keys.
The storage of the latest three messages also enables proper rebroadcasting of
the current round (not implemented in this commit).
Online validators should inherently have them. Offline validators will receive
from the sync protocol.
This does somewhat eliminate the class of nodes who would follow the blockchain
(without validating it), yet that's fine for the performance benefit.
Part of https://github.com/serai-dex/serai/issues/345.
The lack of full DB persistence does mean enough nodes rebooting at the same
time may cause a halt. This will prevent slashes.
* complete various todos
* fix pr comments
* Document bounds on unique hashes in TransactionKind
---------
Co-authored-by: Luke Parker <lukeparker5132@gmail.com>
* report_slashes plumbing in Substrate
Notably delays the SetRetired event until it provides a slash report or the set
after it becomes the set to report its slashes.
* Add dedicated AcceptedHandover event
* Add SlashReport TX to Tributary
* Create SlashReport TXs
* Handle SlashReport TXs
* Add logic to generate a SlashReport to the coordinator
* Route SlashReportSigner into the processor
* Finish routing the SlashReport signing/TX publication
* Add serai feature to processor's serai-client
Not only is this more performant, the definition of retired won't be if a newer
session is active. It will be if the session has posted a slash report or the
stake for that session has unlocked.
Initial commit towards implementing SlashReports.
