Check holocene activation based on the parent's timestamp

[mininny]

It seems like, when op-reth is decoding the extraData for holocene gas fee, it is currently using the current block's timestamp to check if the holocene was activated. However, according to the spec, the check should be done on the parent block's timestamp since only holocene-activated parent would have proper extraData.

This PR modifies the behavior to check for the parent block's timestamp.

Please correct me if my understanding of reth codebase is incorrect! :)

[mattsse]

However, according to the spec, the check should be done on the parent

where is this mentioned?

hmm, but yeah I wonder if this is problematic for the transition block

looks like we're missing this edge case where timestamp is the activation block's timestamp @cody-wang-cb ?

[mininny]

However, according to the spec, the check should be done on the parent

where is this mentioned?

hmm, but yeah I wonder if this is problematic for the transition block

looks like we're missing this edge case where timestamp is the activation block's timestamp @cody-wang-cb ?

It's mentioned here:

if Holocene is not active in parent_header.timestamp, the [prior EIP-1559 constants](https://github.com/ethereum-optimism/specs/blob/main/specs/protocol/exec-engine.md#1559-parameters) constants are used. While parent_header.extraData is typically empty prior to Holocene, there are some legacy cases where it may be set arbitrarily, so it must not be assumed to be empty.

I think this is also how geth is implemented

[mattsse]

right, nice find

we haven't Hit this on sepolia yet because I think assume we crossed that transition via p2p blocks and not via derivation

[mattsse]

thanks @mininny after reading the base fee section, this is indeed the right fix, makes sense because we can only extract from parent if holocene is active at parent

[mininny]

thanks @mininny after reading the base fee section, this is indeed the right fix, makes sense because we can only extract from parent if holocene is active at parent

Awesome! glad we found it before mainnet 😄
Do you have any clue on when this could be released? Will it be included in the next regular release?

[mattsse]

definitely, targeted for early next week

[sebastianst]

Could we add a regression test for this? cc @clabby @refcell