# Ethereum Protocol Fellowship - The Third Cohort (Update 6)

This is the sixth update for Ethereum Protocol Fellowship - The Third Cohort.

In the past two weeks, I worked on a bunch of different things that needed to be done before continuing with the simulation of user operations (EIP-4337). This was due to finding out that debug endpoint `debug_traceCall` is necessary for bundlers, which is only implemented in [Geth](https://github.com/ethereum/go-ethereum) and [Erigon](https://github.com/ledgerwatch/erigon). Tracing/debug endpoints could also be better supported (at least they are not on free tiers) by major JSON-RPC API providers.

- Description: https://github.com/eth-protocol-fellows/cohort-three/blob/master/projects/4337-bundler-rust.md
- Architecture and specification: https://hackmd.io/@Vid201/aa-bundler-rust
- GitHub repository: https://github.com/Vid201/aa-bundler/

## Updates

List of updates:

1. Added support for `debug_traceCall` in the library [ethers-rs](https://github.com/gakonst/ethers-rs/). Pull request is already merged: https://github.com/gakonst/ethers-rs/pull/1949.
2. Due to needing endpoint `debug_traceCall`, I set up a private Geth node for testing purposes (good repo for that [here](https://github.com/krzkaczor/geth-private-node)).
3. Reviewed Will's [pull request](https://github.com/Vid201/aa-bundler/pull/25) for entrypoint smart contract bindings.
4. Adapted implementation for sanity checks of user operations to use new bindings for entry point smart contract and the first call to simulate user operations. Draft pull request [here](https://github.com/Vid201/aa-bundler/pull/24).
5. Added placeholders for [two new RPC methods](https://github.com/Vid201/aa-bundler/pull/28).
6. Setup integration tests based on Will's [code](https://github.com/Vid201/aa-bundler/pull/26).
7. Joined the EIP-4337 Bundler working group, first meeting in January. :)

## Next steps

After finishing with the setup of integration tests, I can continue with the implementation of the simulation of user operations and additional checks that comes alongside, such as which opcodes are allowed and which are not. After finishing with the private user operation pool, I will continue implementing JSON RPC calls and the bundling itself.