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In order to avoid full replays when validating attestations hailing from untaken forks, it's better to keep shufflings separate from `EpochRef` and perform a lookahead on the shuffling when processing the block that determines them. This also helps performance in the case where REST clients are trying to perform lookahead on attestation duties and decreases memory usage by sharing shufflings between EpochRef instances of the same dependent root.
Gossip Processing
This folder holds a collection of modules to:
- validate raw gossip data before
- rebroadcasting it (potentially aggregated)
- sending it to one of the consensus object pools
Validation
Gossip validation is different from consensus verification in particular for blocks.
- Blocks: https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/p2p-interface.md#beacon_block
- Attestations (aggregated): https://github.com/ethereum/consensus-specs/blob/v1.1.10/specs/phase0/p2p-interface.md#beacon_aggregate_and_proof
- Attestations (unaggregated): https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.2/specs/phase0/p2p-interface.md#attestation-subnets
- Voluntary exits: https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.2/specs/phase0/p2p-interface.md#voluntary_exit
- Proposer slashings: https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.2/specs/phase0/p2p-interface.md#proposer_slashing
- Attester slashing: https://github.com/ethereum/consensus-specs/blob/v1.2.0-rc.2/specs/phase0/p2p-interface.md#attester_slashing
There are multiple consumers of validated consensus objects:
- a
ValidationResult.Accept
output triggers rebroadcasting in libp2p- We jump into method
validate(PubSub, Message)
in libp2p/protocols/pubsub/pubsub.nim - which was called by
rpcHandler(GossipSub, PubSubPeer, RPCMsg)
- We jump into method
- a
blockValidator
message enqueues the validated object to the processing queue inblock_processor
blockQueue: AsyncQueue[BlockEntry]
(shared with request_manager and sync_manager)- This queue is then regularly processed to be made available to the consensus object pools.
- a
xyzValidator
message adds the validated object to a pool in eth2_processor- Attestations (unaggregated and aggregated) get collected into batches.
- Once a threshold is exceeded or after a timeout, they get validated together using BatchCrypto.
Security concerns
As the first line of defense in Nimbus, modules must be able to handle bursts of data that may come:
- from malicious nodes trying to DOS us
- from long periods of non-finality, creating lots of forks, attestations