Add EIP: Uncouple blob count between CL and EL

[ralexstokes]

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[eth-bot]

✅ All reviewers have approved.

[github-actions]

The commit 965c047 (as a parent of e4a8338) contains errors.
Please inspect the Run Summary for details.

[mkalinin]

IMHO, this should be moved to Motivation or partially to Rationale

[mkalinin]

AFAICS, target_blob_gas_per_block is used to compute excess_blob_gas. Would it be possible to send the target as a part of PayloadAttributes so the EL can compute the excess and make CL validate that the excess is computed correctly given the target and parent’s excess?

[ralexstokes]

the CL part of this change is here: ethereum/consensus-specs#3800 where the target is sent w/ the payload attributes

[mkalinin]

Sorry, i wasn’t clear enough on the CL validation part, it seems to be possible to me to not include target_blob_gas_per_block into EL block by doing the following:

1. Send this parameter to payload build process so EL can correctly compute excess_blob_gas
2. Make CL validate that the computation was done correctly by utilising a simple math: assert payload.excess_blob_gas == min(0, state.latest_execution_payload_header.excess_blob_gas + target_blob_gas_per_block - blob_gas_used)

[ralexstokes]

would you still commit the target_blob_gas in the EL header?

it seems to break the ability for the EL to independently verify the excess_blob_gas (and by extension the blob base fee) if it doesn't have access to the target value

if we keep the header extension then your change is just moving this check from the EL to the CL, which is fine in principle although I could argue violates the separation of concerns of "blob (max) limit check on the CL for DoS reasons" and "blob fee accounting on the EL"

[mkalinin]

it seems to break the ability for the EL to independently verify the excess_blob_gas (and by extension the blob base fee) if it doesn't have access to the target value

I’d argue that EL doesn’t need to have this ability as long as CL is responsible for verifying the excess_blob_gas computation. If we put it this way then we have no change to the EL block structure with a bit of cross-layer logic duplication: EL and CL will have to compute excess_blob_gas. But I think this duplication is fine as the excess_blob_gas formula is unlikely to change.

[eth-bot]

All Reviewers Have Approved; Performing Automatic Merge...