Implement geth-embedded builder API

Author: Ruteri

README.md

@@ -1,18 +1,12 @@
-## Go Ethereum
+[geth readme](README.original.md)
 
 Official Golang execution layer implementation of the Ethereum protocol.
 
-[![API Reference](
-https://camo.githubusercontent.com/915b7be44ada53c290eb157634330494ebe3e30a/68747470733a2f2f676f646f632e6f72672f6769746875622e636f6d2f676f6c616e672f6764646f3f7374617475732e737667
-)](https://pkg.go.dev/github.com/ethereum/go-ethereum?tab=doc)
-[![Go Report Card](https://goreportcard.com/badge/github.com/ethereum/go-ethereum)](https://goreportcard.com/report/github.com/ethereum/go-ethereum)
-[![Travis](https://travis-ci.com/ethereum/go-ethereum.svg?branch=master)](https://travis-ci.com/ethereum/go-ethereum)
-[![Discord](https://img.shields.io/badge/discord-join%20chat-blue.svg)](https://discord.gg/nthXNEv)
+Builder API implementing [builder spec](https://github.com/ethereum/builder-specs), making geth into a standalone block builder. 
 
-Automated builds are available for stable releases and the unstable master branch. Binary
-archives are published at https://geth.ethereum.org/downloads/.
+Run on your favorite network, including Kiln and local devnet.
 
-## Building the source
+Requires forkchoice update to be sent for block building, on public testnets run beacon node modified to send forkchoice update on every slot [example modified beacon client (lighthouse)](https://github.com/flashbots/lighthouse)
 
 For prerequisites and detailed build instructions please read the [Installation Instructions](https://geth.ethereum.org/docs/getting-started/installing-geth).
 
@@ -132,33 +126,40 @@ called [*Rinkeby*](https://www.rinkeby.io) which is operated by members of the c
 $ geth --rinkeby console
 ```
 
-### Configuration
+### Full node on the Ropsten test network
 
-As an alternative to passing the numerous flags to the `geth` binary, you can also pass a
-configuration file via:
+In addition to Görli and Rinkeby, Geth also supports the ancient Ropsten testnet. The
+Ropsten test network is based on the Ethash proof-of-work consensus algorithm. As such,
+it has certain extra overhead and is more susceptible to reorganization attacks due to the
+network's low difficulty/security.
 
-```shell
-$ geth --config /path/to/your_config.toml
-```
+Builder API has two hooks into geth:
+* On forkchoice update, changing the payload attributes feeRecipient to the one registered for next slot's validator
+* On new sealed block, consuming the block as the next slot's proposed payload
 
-To get an idea of how the file should look like you can use the `dumpconfig` subcommand to
-export your existing configuration:
+## Limitations
 
-```shell
-$ geth --your-favourite-flags dumpconfig
-```
+* Blocks are only built on forkchoice update call from beacon node
+* Only works post-Bellatrix, fork version is static
+* Does not accept external blocks
+* Does not have payload cache, only the latest block is available
 
-*Note: This works only with `geth` v1.6.0 and above.*
+## Usage
 
-#### Docker quick start
-
-One of the quickest ways to get Ethereum up and running on your machine is by using
-Docker:
+To get an idea of how the file should look like you can use the `dumpconfig` subcommand to
+export your existing configuration:
 
-```shell
-docker run -d --name ethereum-node -v /Users/alice/ethereum:/root \
-           -p 8545:8545 -p 30303:30303 \
-           ethereum/client-go
+Builder API options:
+```
+$ geth --help
+BUILDER API OPTIONS:
+  --builder.validator_checks               Enable the validator checks
+  --builder.secret_key value               Builder API key used for signing headers (default: "0x2fc12ae741f29701f8e30f5de6350766c020cb80768a0ff01e6838ffd2431e11") [$BUILDER_SECRET_KEY]
+  --builder.listen_addr value              Listening address for builder endpoint (default: ":28545") [$BUILDER_LISTEN_ADDR]
+  --builder.genesis_fork_version value     Gensis fork version (default: "0x02000000") [$BUILDER_GENESIS_FORK_VERSION]
+  --builder.bellatrix_fork_version value   Bellatrix fork version (default: "0x02000000") [$BUILDER_BELLATRIX_FORK_VERSION]
+  --builder.genesis_validators_root value  Genesis validators root of the network (static). For kiln use 0x99b09fcd43e5905236c370f184056bec6e6638cfc31a323b304fc4aa789cb4ad (default: "0x0000000000000000000000000000000000000000000000000000000000000000") [$BUILDER_GENESIS_VALIDATORS_ROOT]
+  --builder.beacon_endpoint value          Beacon endpoint to connect to for beacon chain data (default: "http://127.0.0.1:5052") [$BUILDER_BEACON_ENDPOINT]
 ```
 
 This will start `geth` in snap-sync mode with a DB memory allowance of 1GB, as the