Txpool: Enforce minimum gas fee on tx entry

[sieniven]

Summary

• This PR fixes the issue - [txpool] Miss a threshold gas price to restrict txs from entering the txpool. #764
• Also guards against the initial base fee issue raised on - Base fee calculation error on pre-london fork #773
• Adds minimum gas price enforcement on both addLocalTxs and addRemoteTxs to safeguard against undesired gasless txs
• Allow enforced gas fee to be configurable, defaulting at 1gwei
• RPC will return an error for txs that get rejected from the txpool from low gas prices

Context

• The issue with the current txpool with the zkevm node is that the pool is designed for post-london fork supporting EIP1559 transactions (baseFee subpool design)
• However, zkevm node is currently set to pre-london fork, and all EIP1559 transactions are rejected form the mempool (

  cdk-erigon/zk/txpool/pool.go

  Lines 710 to 713 in 4796359

  	isLondon := p.isLondon()
  	if !isLondon && txn.Type == 0x2 {
  	return UnsupportedTx
  	}

  )
• With the correct fixes that forkguards the base fee calculation for pre-london fork, we will need to enforce minimum fee tip on transactions entering the txpool

[mandrigin]

quick question -- will that produce an immediate error for user trying to use eth_sendRawTransaction?

Because the last thing we want is for a tx to be accepted and just disappear.

[sieniven]

quick question -- will that produce an immediate error for user trying to use eth_sendRawTransaction?

Because the last thing we want is for a tx to be accepted and just disappear.

@mandrigin This PR enforces the correct behaviour which resolves this issue. More context: #774 (comment)

This PR rejects txs on the RPC end entirely on validateTx, and returns an txpool rejection error on the RPC.

[mandrigin]

will it break gasless (that come with 0 fee)?

[sieniven]

Thanks for the spot. I think it might, let me resolve this.

[mandrigin]

question about gasless -- it must keep working if allow-free-transactions is set to true

[sonarcloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarCloud

[sieniven]

@mandrigin I am making some assumptions here, but it seems like the zkevm node on your side will only allow gasless txs if they were submitted locally. In this case this check is skipped entirely, since there isnt any other checks on gasless txs on the validate tx pipeline on tx entry into the pool. I have reverted the min gasprice check to only happen for non-local txs in commit - 3b33c6e