internal/ethapi: Set basefee for AccessList based on given block, not chain tip

[jwasinger]

totally WIP, and I'm not sure this is correct. I need to further validate this tomorrow.

Should close #30145 . The problem is that for AccessList, we are filling transaction fields with TransactionArgs.setDefaults which afaict is meant to validate provided fields and give proper values to missing fields based on the state at the current chain tip.

eth_call-like methods seem to populate fields using TransactionArgs.CallDefaults, which also seems appropriate for eth_accessList as it is eth_call-like under the hood: it can be executed against historical blocks.

The referenced issue reflects this: if we calculate defaults for the transaction's dynamic fee fields based on the chain tip, but re-execute against a historical block, then we can encounter a situation where the calculated default for the gas tip is below the base fee of the historical block.

[s1na]

Yeah I think it makes sense. We shouldn't need to estimate actual gas prices or gas limit. Sure those can influence EVM execution but the user can pass in those if they care/their contract depends on it.

Only one thing I noticed: not filling the nonce causes the To address computation possibly wrong for create txes.

[jwasinger]

Only one thing I noticed: not filling the nonce causes the To address computation possibly wrong for create txes.

So this would mean that this is broken in all eth_call variants?

[jwasinger]

It's not broken. The reason is that the nonce during creation is sourced from the state of the account, not what's in the transaction args.

[s1na]

It's not broken. The reason is that the nonce during creation is sourced from the state of the account, not what's in the transaction args.

Yep for eth_call it's not broken but here it will be when using CallDefaults. It's because CreateAccessList uses the nonce from tx args and passes that to the tracer. We could either here use account state, or modify the tracer to use OnEnter && level == 0 to get the to address.

[jwasinger]

If the provided nonce was not correct, the transaction will fail in TransactionArgs.TransitionDb. So I think the current code should be okay (?)

[holiman]

the setDefaults has a lot of logic handling blobs that are passed in the args, and that will become broken if we just change this

[fjl]

We could just call setBlobTxSidecar in CallDefaults. But I'd say it's OK not to support them here.

[holiman]

But setDefaults will set the fee defaults on the latest block.

	if err := args.setFeeDefaults(ctx, b); err != nil {
		return err
	}

And regardless of what order we invoke it, it will use the latest header, and do

	if err := args.setCancunFeeDefaults(ctx, head, b); err != nil {
		return err
	}

SO it will apply cancun checks according to tip, regardless of what the given block is.

[holiman]

How about something like this

// setFeeDefaults fills in default fee values for unspecified tx fields.
func (args *TransactionArgs) setFeeDefaults(ctx context.Context, b Backend) error {
	return setFeeDefaultsUsingThisHeader(b.CurrentHeader())
}
func (args *TransactionArgs) setFeeDefaultsUsingThisHeader(ctx context.Context, b Backend, head *types.Header) error {
	// Sanity check the EIP-4844 fee parameters.

[s1na]

the setDefaults has a lot of logic handling blobs that are passed in the args, and that will become broken if we just change this

The logic there is to fill in blob proofs and commitments if they were not provided. Those matter only when submitting a tx. Since for a simulation all that can be accessed via evm is blob hashes (which still can be passed in via TransactionArgs).

All in all I think I agree with @jwasinger that CallDefaults is a better validation function to use here. All the methods that involve signing and submitting a tx use setDefaults while all the "simulation" methods use CallDefaults.