Add fee cap for transactions submitted via RPC.

[AbdelStark]

PR description

This PR adds a new CLI option that enables the user to define the maximum fees (gas price) accepted for transactions submitted via RPC(eth_sendRawTransaction).

Changes summary

• Added --rpc-tx-feecap command line flag.
  • Maximum transaction fees (in Wei) accepted for transaction submitted through RPC.
  • Defaulted to 1 ether.
• Updated TransactionPool.addLocalTransaction method: performs an additional check to verify if transaction fees don't exceed user defined fee cap (if cap is set to 0 then it is ignored and means no cap).

Testing

Unit tests

Command line

• BesuCommandTest.transactionPoolTxFeeCap: Assert that specified CLI flag value is used (different from default).
• BesuCommandTest.invalidTansactionPoolTxFeeCapShouldFail: Assert that invalid value causes an error with proper message.

Transaction pool

• TransactionPoolTest.shouldIgnoreFeeCapIfSetZero: Assert that no fee cap is applied if set to 0.
• TransactionPoolTest.shouldRejectLocalTransactionIfFeeCapExceeded: Assert that local transaction is rejected if gasPrice is higher than defined fee cap.

Manual tests

Steps

• Run Besu with --rpc-tx-feecap=2000000000000000005
• Submit transaction with nonce set to 1 and gasPrice set to 2000000000000000005
• Submit transaction with nonce set to 2 and gasPrice set to 2000000000000000006

Results

First transaction is accepted.
Seconds transaction is rejected with response:

{
  "jsonrpc": "2.0",
  "id": 1,
  "error": {
    "code": -32000,
    "message": "Transaction fee cap exceeded"
  }
}

Signed-off-by: Abdelhamid Bakhta abdelhamid.bakhta@consensys.net

[matkt]

LGTM
Just read the code on Github.