Add consensus version to submitBlindedBlock request header

[jimmygchen]

Description

Consider providing fork name via a Eth-Consensus-Version HTTP header when sending submitBlindedBlock request to remote builder. (or potentially all remote builder requests?)

This change has been included in builder-specs v0.3.0, although it's an optional tag:

https://github.com/ethereum/builder-specs/blob/7b269305e1e54f22ddb84b3da2f222e20adf6e4f/apis/builder/blinded_blocks.yaml#L15

This header would help the endpoint provider (relays) discriminate the type the request payload when decoding.

[Gua00va]

hey @jimmygchen , is this related to #4525 ?

[jimmygchen]

This is a different one, this is for the submitBlindedBlock request from the Beacon Node to the Builder in the builder block proposal flow, i.e. POST /eth/v2/builder/blinded_blocks in the below diagram.

We currently don't send this HTTP header in the request, and is an optional header in the spec that would make it easier for the builder to deserialize the request body.

sequenceDiagram
    participant validator
    participant beacon_node
    participant mev_boost
    Title: Block Proposal with Builder API
    validator->>beacon_node: GET v2/validator/blinded_blocks/{slot}
    beacon_node->>mev_boost: GET v1/builder/header/{slot}/{parent_hash}/{pubkey}
    mev_boost-->>beacon_node: returns bid & blinded payload
    beacon_node-->>validator: returns blinded block
    Note over validator: signs the blinded block
    validator->>beacon_node: POST beacon/blinded_blocks
    beacon_node->>mev_boost: POST /eth/v2/builder/blinded_blocks
    Note right of beacon_node: sends signed blinded beacon block
    mev_boost-->>beacon_node: returns revealed payload
    Note over beacon_node: construct block and broadcast block

Loading

[Gua00va]

hey @jimmygchen, how do I get access to some object of ChainSpec type here:

lighthouse/beacon_node/builder_client/src/lib.rs

Line 141 in dfcb336

pub async fn post_builder_blinded_blocks<E: EthSpec>(

It is required to get fork version here:

lighthouse/consensus/types/src/signed_beacon_block.rs

Line 89 in dfcb336

pub fn fork_name(&self, spec: &ChainSpec) -> Result<ForkName, InconsistentFork> {

[jimmygchen]

Hi @Gua00va

ChainSpec is available on the BeaconChain object, you should be able to obtain the fork_name when constructing the block, perhaps here:

lighthouse/beacon_node/http_api/src/publish_blocks.rs

Lines 267 to 277 in 071dd4c

	late_block_logging(
	&chain,
	timestamp_now(),
	block.message(),
	block_root,
	"builder",
	&log,
	);
	let full_payload = el
	.propose_blinded_beacon_block(block_root, &block)

and then pass it to the post_builder_blinded_blocks function.

[jimmygchen]

I think this is probably not super useful unless the header is mandatory, perhaps revisit this if a new v2 version of the endpoint is added with SSZ support.

[jimmygchen]

Closing this. See comment above.

[michaelsproul]

I think we actually implemented this header recently off the back of a bug report by JGM:

• POST to eth/v1/builder/blinded_blocks missing header #5405

Impl in:

• Add missing header to eth/v1/builder/blinded_blocks #5407

[jimmygchen]

Nice!