From 86ce34c2e398c21ee2ed888ccb7b93e1997ffcb3 Mon Sep 17 00:00:00 2001
From: sprites0 <199826320+sprites0@users.noreply.github.com>
Date: Sat, 1 Mar 2025 17:30:08 +0000
Subject: [PATCH] feat: Forward incoming txs to upstream server

---
 Cargo.lock                |  1 +
 bin/reth/Cargo.toml       |  1 +
 bin/reth/src/forwarder.rs | 45 +++++++++++++++++++++++++++++++++++++++
 bin/reth/src/main.rs      | 41 ++++++++++++++++++++++++++---------
 4 files changed, 78 insertions(+), 10 deletions(-)
 create mode 100644 bin/reth/src/forwarder.rs

diff --git a/Cargo.lock b/Cargo.lock
index 685ee41de..1cbcfa7a6 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -6659,6 +6659,7 @@ dependencies = [
  "eyre",
  "futures",
  "jsonrpsee",
+ "jsonrpsee-core",
  "lz4_flex",
  "once_cell",
  "parking_lot",
diff --git a/bin/reth/Cargo.toml b/bin/reth/Cargo.toml
index 1bbef6495..22bbdeaf6 100644
--- a/bin/reth/Cargo.toml
+++ b/bin/reth/Cargo.toml
@@ -97,6 +97,7 @@ reth-e2e-test-utils.workspace = true
 once_cell.workspace = true
 reth-ethereum-forks.workspace = true
 jsonrpsee.workspace = true
+jsonrpsee-core.workspace = true
 reth-rpc-layer.workspace = true
 
 [dev-dependencies]
diff --git a/bin/reth/src/forwarder.rs b/bin/reth/src/forwarder.rs
new file mode 100644
index 000000000..4f8e2ab46
--- /dev/null
+++ b/bin/reth/src/forwarder.rs
@@ -0,0 +1,45 @@
+use alloy_primitives::{Bytes, B256};
+use jsonrpsee::{
+    http_client::{HttpClient, HttpClientBuilder},
+    proc_macros::rpc,
+    types::{error::INTERNAL_ERROR_CODE, ErrorObject},
+};
+use jsonrpsee_core::{async_trait, client::ClientT, ClientError, RpcResult};
+
+#[rpc(server, namespace = "eth")]
+pub(crate) trait EthForwarderApi {
+    /// Returns block 0.
+    #[method(name = "sendRawTransaction")]
+    async fn send_raw_transaction(&self, tx: Bytes) -> RpcResult<B256>;
+}
+
+pub(crate) struct EthForwarderExt {
+    client: HttpClient,
+}
+
+impl EthForwarderExt {
+    pub(crate) fn new(upstream_rpc_url: String) -> Self {
+        let client =
+            HttpClientBuilder::default().build(upstream_rpc_url).expect("Failed to build client");
+
+        Self { client }
+    }
+}
+
+#[async_trait]
+impl EthForwarderApiServer for EthForwarderExt {
+    async fn send_raw_transaction(&self, tx: Bytes) -> RpcResult<B256> {
+        let txhash =
+            self.client.clone().request("eth_sendRawTransaction", vec![tx]).await.map_err(|e| {
+                match e {
+                    ClientError::Call(e) => e,
+                    _ => ErrorObject::owned(
+                        INTERNAL_ERROR_CODE,
+                        format!("Failed to send transaction: {:?}", e),
+                        Some(()),
+                    ),
+                }
+            })?;
+        Ok(txhash)
+    }
+}
diff --git a/bin/reth/src/main.rs b/bin/reth/src/main.rs
index 9409c5799..1d26d1e5a 100644
--- a/bin/reth/src/main.rs
+++ b/bin/reth/src/main.rs
@@ -4,22 +4,28 @@
 static ALLOC: reth_cli_util::allocator::Allocator = reth_cli_util::allocator::new_allocator();
 
 mod block_ingest;
+mod forwarder;
 mod serialized;
 
 use std::path::PathBuf;
 
 use block_ingest::BlockIngest;
 use clap::{Args, Parser};
+use forwarder::EthForwarderApiServer;
 use reth::cli::Cli;
 use reth_ethereum_cli::chainspec::EthereumChainSpecParser;
 use reth_node_ethereum::EthereumNode;
 use tracing::info;
 
 #[derive(Args, Debug, Clone)]
-struct IngestArgs {
+struct HyperliquidExtArgs {
     /// EVM blocks base directory
-    #[arg(long, default_value="/tmp/evm-blocks")]
+    #[arg(long, default_value = "/tmp/evm-blocks")]
     pub ingest_dir: PathBuf,
+
+    /// Upstream RPC URL to forward incoming transactions.
+    #[arg(long, default_value = "https://rpc.hyperliquid.xyz/evm")]
+    pub upstream_rpc_url: String,
 }
 
 fn main() {
@@ -30,15 +36,30 @@ fn main() {
         std::env::set_var("RUST_BACKTRACE", "1");
     }
 
-    if let Err(err) = Cli::<EthereumChainSpecParser, IngestArgs>::parse().run(|builder, ingest_args| async move {
-        info!(target: "reth::cli", "Launching node");
-        let handle = builder.launch_node(EthereumNode::default()).await?;
+    if let Err(err) = Cli::<EthereumChainSpecParser, HyperliquidExtArgs>::parse().run(
+        |builder, ingest_args| async move {
+            info!(target: "reth::cli", "Launching node");
+            let handle = builder
+                .node(EthereumNode::default())
+                .extend_rpc_modules(move |ctx| {
+                    let upstream_rpc_url = ingest_args.upstream_rpc_url.clone();
+                    ctx.modules.remove_method_from_configured("eth_sendRawTransaction");
+                    ctx.modules.merge_configured(
+                        forwarder::EthForwarderExt::new(upstream_rpc_url).into_rpc(),
+                    )?;
 
-        let ingest_dir = ingest_args.ingest_dir;
-        let ingest = BlockIngest(ingest_dir);
-        ingest.run(handle.node).await.unwrap();
-        handle.node_exit_future.await
-    }) {
+                    info!("Transaction forwarder extension enabled");
+                    Ok(())
+                })
+                .launch()
+                .await?;
+
+            let ingest_dir = ingest_args.ingest_dir;
+            let ingest = BlockIngest(ingest_dir);
+            ingest.run(handle.node).await.unwrap();
+            handle.node_exit_future.await
+        },
+    ) {
         eprintln!("Error: {err:?}");
         std::process::exit(1);
     }