nimbus-eth2/beacon_chain/gossip_processing

Gossip Processing

This folders hold a collection of modules to:

• validate raw gossip data before
  • rebroadcasting them (potentially aggregated)
  • sending it to one of the consensus object pool

Validation

Gossip Validation is different from consensus verification in particular for blocks.

• Blocks: https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#beacon_block
• Attestations (aggregate): https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#beacon_aggregate_and_proof
• Attestations (single): https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#attestation-subnets
• Exits: https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#voluntary_exit
• Proposer slashings: https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#proposer_slashing
• Attester slashing: https://github.com/ethereum/eth2.0-specs/blob/v1.0.1/specs/phase0/p2p-interface.md#attester_slashing

There are 2 consumers of validated consensus objects:

• a ValidationResult.Accept output triggers rebroadcasting in libp2p
  • method validate(PubSub, message) in libp2p/protocols/pubsub/pubsub.nim in the
  • which was called by rpcHandler(GossipSub, PubSubPeer, RPCMsg)
• a xyzValidator message enqueues the validated object in one of the processing queue in eth2_processor
  • blocksQueue: AsyncQueue[BlockEntry], (shared with request_manager and sync_manager)
  • attestationsQueue: AsyncQueue[AttestationEntry]
  • aggregatesQueue: AsyncQueue[AggregateEntry]

Those queues are then regularly processed to be made available to the consensus object pools.

Security concerns

As the first line of defense in Nimbus, modules must be able to handle burst of data that may come:

• from malicious nodes trying to DOS us
• from long periods of non-finality, creating lots of forks, attestations, forks