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Gloas -- Networking

Note: This document is a work-in-progress for researchers and implementers.

Introduction

This document contains the consensus-layer networking specification for Gloas.

The specification of these changes continues in the same format as the network specifications of previous upgrades, and assumes them as pre-requisite.

Modification in Gloas

Helper functions

Modified compute_fork_version

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def compute_fork_version(epoch: Epoch) -> Version:
    """
    Return the fork version at the given ``epoch``.
    """
    if epoch >= GLOAS_FORK_EPOCH:
        return GLOAS_FORK_VERSION
    if epoch >= FULU_FORK_EPOCH:
        return FULU_FORK_VERSION
    if epoch >= ELECTRA_FORK_EPOCH:
        return ELECTRA_FORK_VERSION
    if epoch >= DENEB_FORK_EPOCH:
        return DENEB_FORK_VERSION
    if epoch >= CAPELLA_FORK_EPOCH:
        return CAPELLA_FORK_VERSION
    if epoch >= BELLATRIX_FORK_EPOCH:
        return BELLATRIX_FORK_VERSION
    if epoch >= ALTAIR_FORK_EPOCH:
        return ALTAIR_FORK_VERSION
    return GENESIS_FORK_VERSION

Configuration

[New in Gloas:EIP7732]

Name Value Description
MAX_REQUEST_PAYLOADS 2**7 (= 128) Maximum number of execution payload envelopes in a single request

Containers

Modified DataColumnSidecar

Note: The signed_block_header and kzg_commitments_inclusion_proof fields have been removed from DataColumnSidecar in Gloas as header and inclusion proof verifications are no longer required in ePBS. Instead, sidecars are validated by checking that the hash of kzg_commitments matches what's committed in the builder's bid for the corresponding beacon_block_root.

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class DataColumnSidecar(Container):
    index: ColumnIndex
    column: List[Cell, MAX_BLOB_COMMITMENTS_PER_BLOCK]
    kzg_commitments: List[KZGCommitment, MAX_BLOB_COMMITMENTS_PER_BLOCK]
    kzg_proofs: List[KZGProof, MAX_BLOB_COMMITMENTS_PER_BLOCK]
    # [Modified in Gloas:EIP7732]
    # Removed `signed_block_header`
    # [Modified in Gloas:EIP7732]
    # Removed `kzg_commitments_inclusion_proof`
    # [New in Gloas:EIP7732]
    slot: Slot
    # [New in Gloas:EIP7732]
    beacon_block_root: Root

Helpers

Modified verify_data_column_sidecar
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def verify_data_column_sidecar(sidecar: DataColumnSidecar) -> bool:
    """
    Verify if the data column sidecar is valid.
    """
    # The sidecar index must be within the valid range
    if sidecar.index >= NUMBER_OF_COLUMNS:
        return False

    # A sidecar for zero blobs is invalid
    if len(sidecar.kzg_commitments) == 0:
        return False

    # [Modified in Gloas:EIP7732]
    # Check that the sidecar respects the blob limit
    epoch = compute_epoch_at_slot(sidecar.slot)
    if len(sidecar.kzg_commitments) > get_blob_parameters(epoch).max_blobs_per_block:
        return False

    # The column length must be equal to the number of commitments/proofs
    if len(sidecar.column) != len(sidecar.kzg_commitments) or len(sidecar.column) != len(
        sidecar.kzg_proofs
    ):
        return False

    return True

The gossip domain: gossipsub

Some gossip meshes are upgraded in the fork of Gloas to support upgraded types.

Topics and messages

Topics follow the same specification as in prior upgrades.

The beacon_block topic is updated to support the modified type

Name Message Type
beacon_block SignedBeaconBlock

The new topics along with the type of the data field of a gossipsub message are given in this table:

Name Message Type
execution_payload_bid SignedExecutionPayloadBid
execution_payload SignedExecutionPayloadEnvelope
payload_attestation_message PayloadAttestationMessage
Global topics

Gloas introduces new global topics for execution bid, execution payload and payload attestation.

beacon_aggregate_and_proof

Let block be the beacon block corresponding to aggregate.data.beacon_block_root.

The following validations are added:

  • [REJECT] aggregate.data.index < 2.
  • [REJECT] aggregate.data.index == 0 if block.slot == aggregate.data.slot.

The following validations are removed:

  • [REJECT] aggregate.data.index == 0.
beacon_block

[Modified in Gloas:EIP7732]

The type of the payload of this topic changes to the (modified) SignedBeaconBlock found in the Beacon Chain changes.

There are no new validations for this topic. However, all validations with regards to the ExecutionPayload are removed:

  • [REJECT] The length of KZG commitments is less than or equal to the limitation defined in Consensus Layer -- i.e. validate that len(signed_beacon_block.message.body.blob_kzg_commitments) <= get_blob_parameters(get_current_epoch(state)).max_blobs_per_block
  • [REJECT] The block's execution payload timestamp is correct with respect to the slot -- i.e. execution_payload.timestamp == compute_time_at_slot(state, block.slot).
  • If execution_payload verification of block's parent by an execution node is not complete:
  • [REJECT] The block's parent (defined by block.parent_root) passes all validation (excluding execution node verification of the block.body.execution_payload).
  • otherwise:
  • [IGNORE] The block's parent (defined by block.parent_root) passes all validation (including execution node verification of the block.body.execution_payload).

And instead the following validations are set in place with the alias bid = signed_execution_payload_bid.message:

  • If execution_payload verification of block's execution payload parent by an execution node is complete:
  • [REJECT] The block's execution payload parent (defined by bid.parent_block_hash) passes all validation.
  • [REJECT] The bid's parent (defined by bid.parent_block_root) equals the block's parent (defined by block.parent_root).
execution_payload

This topic is used to propagate execution payload messages as SignedExecutionPayloadEnvelope.

The following validations MUST pass before forwarding the signed_execution_payload_envelope on the network, assuming the alias envelope = signed_execution_payload_envelope.message, payload = payload_envelope.payload:

  • [IGNORE] The envelope's block root envelope.block_root has been seen (via gossip or non-gossip sources) (a client MAY queue payload for processing once the block is retrieved).
  • [IGNORE] The node has not seen another valid SignedExecutionPayloadEnvelope for this block root from this builder.
  • [IGNORE] The envelope is from a slot greater than or equal to the latest finalized slot -- i.e. validate that envelope.slot >= compute_start_slot_at_epoch(store.finalized_checkpoint.epoch)

Let block be the block with envelope.beacon_block_root. Let bid alias block.body.signed_execution_payload_bid.message (notice that this can be obtained from the state.latest_execution_payload_bid)

  • [REJECT] block passes validation.
  • [REJECT] block.slot equals envelope.slot.
  • [REJECT] envelope.builder_index == bid.builder_index
  • [REJECT] payload.block_hash == bid.block_hash
  • [REJECT] signed_execution_payload_envelope.signature is valid with respect to the builder's public key.
payload_attestation_message

This topic is used to propagate signed payload attestation message.

The following validations MUST pass before forwarding the payload_attestation_message on the network, assuming the alias data = payload_attestation_message.data:

  • [IGNORE] The message's slot is for the current slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance), i.e. data.slot == current_slot.
  • [IGNORE] The payload_attestation_message is the first valid message received from the validator with index payload_attestation_message.validate_index.
  • [IGNORE] The message's block data.beacon_block_root has been seen (via gossip or non-gossip sources) (a client MAY queue attestation for processing once the block is retrieved. Note a client might want to request payload after).
  • [REJECT] The message's block data.beacon_block_root passes validation.
  • [REJECT] The message's validator index is within the payload committee in get_ptc(state, data.slot). The state is the head state corresponding to processing the block up to the current slot as determined by the fork choice.
  • [REJECT] payload_attestation_message.signature is valid with respect to the validator's public key.
execution_payload_bid

This topic is used to propagate signed bids as SignedExecutionPayloadBid.

The following validations MUST pass before forwarding the signed_execution_payload_bid on the network, assuming the alias bid = signed_execution_payload_bid.message:

  • [REJECT] bid.builder_index is a valid, active, and non-slashed builder index.
  • [REJECT] the builder's withdrawal credentials' prefix is BUILDER_WITHDRAWAL_PREFIX -- i.e. is_builder_withdrawal_credential(state.validators[bid.builder_index].withdrawal_credentials) returns True.
  • [IGNORE] this is the first signed bid seen with a valid signature from the given builder for this slot.
  • [IGNORE] this bid is the highest value bid seen for the corresponding slot and the given parent block hash.
  • [IGNORE] bid.value is less or equal than the builder's excess balance -- i.e. MIN_ACTIVATION_BALANCE + bid.value <= state.balances[bid.builder_index].
  • [IGNORE] bid.parent_block_hash is the block hash of a known execution payload in fork choice.
  • [IGNORE] bid.parent_block_root is the hash tree root of a known beacon block in fork choice.
  • [IGNORE] bid.slot is the current slot or the next slot.
  • [REJECT] signed_execution_payload_bid.signature is valid with respect to the bid.builder_index.
Blob subnets
data_column_sidecar_{subnet_id}

[Modified in Gloas:EIP7732]

This topic is used to propagate column sidecars, where each column maps to some subnet_id.

The type of the payload of this topic is DataColumnSidecar.

The following validations MUST pass before forwarding the sidecar: DataColumnSidecar on the network:

Modified from Fulu:

  • [IGNORE] The sidecar is the first sidecar for the tuple (sidecar.beacon_block_root, sidecar.index) with valid kzg proof.

Added in Gloas:

  • [IGNORE] The sidecar's beacon_block_root has been seen via a valid signed execution payload header (builder's bid).
  • [REJECT] The sidecars's slot matches the slot of the block with root beacon_block_root.
  • [REJECT] The hash of the sidecar's kzg_commitments matches the blob_kzg_commitments_root in the corresponding builder's bid for sidecar.beacon_block_root.

Removed from Fulu:

  • [IGNORE] The sidecar is not from a future slot (with a MAXIMUM_GOSSIP_CLOCK_DISPARITY allowance) -- i.e. validate that block_header.slot <= current_slot (a client MAY queue future sidecars for processing at the appropriate slot).
  • [IGNORE] The sidecar is from a slot greater than the latest finalized slot -- i.e. validate that block_header.slot > compute_start_slot_at_epoch(state.finalized_checkpoint.epoch)
  • [REJECT] The proposer signature of sidecar.signed_block_header, is valid with respect to the block_header.proposer_index pubkey.
  • [IGNORE] The sidecar's block's parent (defined by block_header.parent_root) has been seen (via gossip or non-gossip sources) (a client MAY queue sidecars for processing once the parent block is retrieved).
  • [REJECT] The sidecar's block's parent (defined by block_header.parent_root) passes validation.
  • [REJECT] The sidecar is from a higher slot than the sidecar's block's parent (defined by block_header.parent_root).
  • [REJECT] The current finalized_checkpoint is an ancestor of the sidecar's block -- i.e. get_checkpoint_block(store, block_header.parent_root, store.finalized_checkpoint.epoch) == store.finalized_checkpoint.root.
  • [REJECT] The sidecar's kzg_commitments field inclusion proof is valid as verified by verify_data_column_sidecar_inclusion_proof(sidecar).
  • [REJECT] The sidecar is proposed by the expected proposer_index for the block's slot in the context of the current shuffling (defined by block_header.parent_root/block_header.slot). If the proposer_index cannot immediately be verified against the expected shuffling, the sidecar MAY be queued for later processing while proposers for the block's branch are calculated -- in such a case do not REJECT, instead IGNORE this message.
Attestation subnets
beacon_attestation_{subnet_id}

Let block be the beacon block corresponding to attestation.data.beacon_block_root.

The following validations are added:

  • [REJECT] attestation.data.index < 2.
  • [REJECT] attestation.data.index == 0 if block.slot == attestation.data.slot.

The following validations are removed:

  • [REJECT] attestation.data.index == 0.

The Req/Resp domain

Messages

BeaconBlocksByRange v2

Protocol ID: /eth2/beacon_chain/req/beacon_blocks_by_range/2/

fork_version Chunk SSZ type
GENESIS_FORK_VERSION phase0.SignedBeaconBlock
ALTAIR_FORK_VERSION altair.SignedBeaconBlock
BELLATRIX_FORK_VERSION bellatrix.SignedBeaconBlock
CAPELLA_FORK_VERSION capella.SignedBeaconBlock
DENEB_FORK_VERSION deneb.SignedBeaconBlock
ELECTRA_FORK_VERSION electra.SignedBeaconBlock
FULU_FORK_VERSION fulu.SignedBeaconBlock
GLOAS_FORK_VERSION gloas.SignedBeaconBlock
BeaconBlocksByRoot v2

Protocol ID: /eth2/beacon_chain/req/beacon_blocks_by_root/2/

fork_version Chunk SSZ type
GENESIS_FORK_VERSION phase0.SignedBeaconBlock
ALTAIR_FORK_VERSION altair.SignedBeaconBlock
BELLATRIX_FORK_VERSION bellatrix.SignedBeaconBlock
CAPELLA_FORK_VERSION capella.SignedBeaconBlock
DENEB_FORK_VERSION deneb.SignedBeaconBlock
ELECTRA_FORK_VERSION electra.SignedBeaconBlock
FULU_FORK_VERSION fulu.SignedBeaconBlock
GLOAS_FORK_VERSION gloas.SignedBeaconBlock
ExecutionPayloadEnvelopesByRange v1

Protocol ID: /eth2/beacon_chain/req/execution_payload_envelopes_by_range/1/

[New in Gloas:EIP7732]

Request Content:

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(
  start_slot: Slot
  count: uint64
)

Response Content:

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(
  List[SignedExecutionPayloadEnvelope, MAX_REQUEST_BLOCKS_DENEB]
)

Specifications of req\response methods are equivalent to BeaconBlocksByRange v2, with the only difference being the response content type.

For each successful response_chunk, the ForkDigest context epoch is determined by compute_epoch_at_slot(beacon_block.slot) based on the beacon_block referred to by signed_execution_payload_envelope.message.beacon_block_root.

Per fork_version = compute_fork_version(epoch):

fork_version Chunk SSZ type
GLOAS_FORK_VERSION gloas.SignedExecutionPayloadEnvelope
ExecutionPayloadEnvelopesByRoot v1

Protocol ID: /eth2/beacon_chain/req/execution_payload_envelopes_by_root/1/

For each successful response_chunk, the ForkDigest context epoch is determined by compute_epoch_at_slot(beacon_block.slot) based on the beacon_block referred to by signed_execution_payload_envelope.message.beacon_block_root.

Per fork_version = compute_fork_version(epoch):

fork_version Chunk SSZ type
GLOAS_FORK_VERSION gloas.SignedExecutionPayloadEnvelope

Request Content:

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(
  List[Root, MAX_REQUEST_PAYLOADS]
)

Response Content:

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(
  List[SignedExecutionPayloadEnvelope, MAX_REQUEST_PAYLOADS]
)

Requests execution payload envelopes by signed_execution_payload_envelope.message.block_root. The response is a list of SignedExecutionPayloadEnvelope whose length is less than or equal to the number of requested execution payload envelopes. It may be less in the case that the responding peer is missing payload envelopes.

No more than MAX_REQUEST_PAYLOADS may be requested at a time.

ExecutionPayloadEnvelopesByRoot is primarily used to recover recent execution payload envelopes (e.g. when receiving a payload attestation with revealed status as true but never received a payload).

The request MUST be encoded as an SSZ-field.

The response MUST consist of zero or more response_chunk. Each successful response_chunk MUST contain a single SignedExecutionPayloadEnvelope payload.

Clients MUST support requesting payload envelopes since the latest finalized epoch.

Clients MUST respond with at least one payload envelope, if they have it. Clients MAY limit the number of payload envelopes in the response.