From 39ae8ae9f8c809241de2521173c0524bf83d16d1 Mon Sep 17 00:00:00 2001
From: sprites0 <199826320+sprites0@users.noreply.github.com>
Date: Tue, 1 Jul 2025 02:31:29 +0000
Subject: [PATCH] feat: tx forwarder

eth_sendRawTransaction will forward transactions into --upstream-rpc-url, if specified in cli args.
---
 README.md           |  4 ++--
 src/lib.rs          |  1 +
 src/main.rs         | 25 ++++++++++++++++++++++---
 src/node/cli.rs     |  3 +++
 src/tx_forwarder.rs | 44 ++++++++++++++++++++++++++++++++++++++++++++
 5 files changed, 72 insertions(+), 5 deletions(-)
 create mode 100644 src/tx_forwarder.rs

diff --git a/README.md b/README.md
index a97e09ae1..b40d6d7d0 100644
--- a/README.md
+++ b/README.md
@@ -5,10 +5,10 @@ Heavily inspired by [reth-bsc](https://github.com/loocapro/reth-bsc).
 
 ## TODOs
 
-- [ ] Make it compilable
+- [x] Make it compilable
   - [x] EVM
   - [x] Storage
-  - [ ] TX forwarder API
+  - [x] TX forwarder API
 - [x] Decide whether to include system txs, receipts in block or not
 - [x] Downloader
   - [x] S3 format (file)
diff --git a/src/lib.rs b/src/lib.rs
index 1a2b3d4ae..cbfdf5569 100644
--- a/src/lib.rs
+++ b/src/lib.rs
@@ -4,5 +4,6 @@ mod evm;
 mod hardforks;
 pub mod node;
 pub mod pseudo_peer;
+pub mod tx_forwarder;
 
 pub use node::primitives::{HlBlock, HlBlockBody, HlPrimitives};
diff --git a/src/main.rs b/src/main.rs
index da86cdb6d..00c983b5e 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,9 +1,15 @@
 use clap::Parser;
 use reth::builder::NodeHandle;
+use reth_hl::tx_forwarder::{self, EthForwarderApiServer};
 use reth_hl::{
     chainspec::parser::HlChainSpecParser,
-    node::{cli::{Cli, HlNodeArgs}, storage::tables::Tables, HlNode},
+    node::{
+        cli::{Cli, HlNodeArgs},
+        storage::tables::Tables,
+        HlNode,
+    },
 };
+use tracing::info;
 
 // We use jemalloc for performance reasons
 #[cfg(all(feature = "jemalloc", unix))]
@@ -21,8 +27,21 @@ fn main() -> eyre::Result<()> {
     Cli::<HlChainSpecParser, HlNodeArgs>::parse().run(|builder, ext| async move {
         builder.builder.database.create_tables_for::<Tables>()?;
         let (node, engine_handle_tx) = HlNode::new(ext.block_source_args.parse().await?);
-        let NodeHandle { node, node_exit_future: exit_future } =
-            builder.node(node).launch().await?;
+        let NodeHandle { node, node_exit_future: exit_future } = builder
+            .node(node)
+            .extend_rpc_modules(|ctx| {
+                let upstream_rpc_url = ext.upstream_rpc_url;
+                if let Some(upstream_rpc_url) = upstream_rpc_url {
+                    ctx.modules.replace_configured(
+                        tx_forwarder::EthForwarderExt::new(upstream_rpc_url.clone()).into_rpc(),
+                    )?;
+
+                    info!("Transaction forwarding enabled");
+                }
+                Ok(())
+            })
+            .launch()
+            .await?;
 
         engine_handle_tx.send(node.beacon_engine_handle.clone()).unwrap();
 
diff --git a/src/node/cli.rs b/src/node/cli.rs
index b15be7b9b..fc63a4ef2 100644
--- a/src/node/cli.rs
+++ b/src/node/cli.rs
@@ -31,6 +31,9 @@ use tracing::info;
 pub struct HlNodeArgs {
     #[command(flatten)]
     pub block_source_args: BlockSourceArgs,
+
+    #[arg(long, env = "UPSTREAM_RPC_URL")]
+    pub upstream_rpc_url: Option<String>,
 }
 
 /// The main reth_hl cli interface.
diff --git a/src/tx_forwarder.rs b/src/tx_forwarder.rs
new file mode 100644
index 000000000..0d8b2a1f6
--- /dev/null
+++ b/src/tx_forwarder.rs
@@ -0,0 +1,44 @@
+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 trait EthForwarderApi {
+    #[method(name = "sendRawTransaction")]
+    async fn send_raw_transaction(&self, tx: Bytes) -> RpcResult<B256>;
+}
+
+pub struct EthForwarderExt {
+    client: HttpClient,
+}
+
+impl EthForwarderExt {
+    pub 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)
+    }
+}