Ethereum relayer server

Causes send test to pass for the processor.

coins/ethereum/relayer/Cargo.toml

@@ -0,0 +1,30 @@
+[package]
+name = "serai-ethereum-relayer"
+version = "0.1.0"
+description = "A relayer for Serai's Ethereum transactions"
+license = "AGPL-3.0-only"
+repository = "https://github.com/serai-dex/serai/tree/develop/coins/ethereum/relayer"
+authors = ["Luke Parker <lukeparker5132@gmail.com>"]
+keywords = []
+edition = "2021"
+publish = false
+
+[package.metadata.docs.rs]
+all-features = true
+rustdoc-args = ["--cfg", "docsrs"]
+
+[lints]
+workspace = true
+
+[dependencies]
+log = { version = "0.4", default-features = false, features = ["std"] }
+env_logger = { version = "0.10", default-features = false, features = ["humantime"] }
+
+tokio = { version = "1", default-features = false, features = ["rt", "time", "io-util", "net", "macros"] }
+
+serai-env = { path = "../../../common/env" }
+serai-db = { path = "../../../common/db" }
+
+[features]
+parity-db = ["serai-db/parity-db"]
+rocksdb = ["serai-db/rocksdb"]

coins/ethereum/relayer/LICENSE

@@ -0,0 +1,15 @@
+AGPL-3.0-only license
+
+Copyright (c) 2023-2024 Luke Parker
+
+This program is free software: you can redistribute it and/or modify
+it under the terms of the GNU Affero General Public License Version 3 as
+published by the Free Software Foundation.
+
+This program is distributed in the hope that it will be useful,
+but WITHOUT ANY WARRANTY; without even the implied warranty of
+MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
+GNU Affero General Public License for more details.
+
+You should have received a copy of the GNU Affero General Public License
+along with this program. If not, see <http://www.gnu.org/licenses/>.

coins/ethereum/relayer/README.md

@@ -0,0 +1,4 @@
+# Ethereum Transaction Relayer
+
+This server collects Ethereum router commands to be published, offering an RPC
+to fetch them.

coins/ethereum/relayer/src/main.rs

@@ -0,0 +1,100 @@
+pub(crate) use tokio::{
+  io::{AsyncReadExt, AsyncWriteExt},
+  net::TcpListener,
+};
+
+use serai_db::{Get, DbTxn, Db as DbTrait};
+
+#[tokio::main(flavor = "current_thread")]
+async fn main() {
+  // Override the panic handler with one which will panic if any tokio task panics
+  {
+    let existing = std::panic::take_hook();
+    std::panic::set_hook(Box::new(move |panic| {
+      existing(panic);
+      const MSG: &str = "exiting the process due to a task panicking";
+      println!("{MSG}");
+      log::error!("{MSG}");
+      std::process::exit(1);
+    }));
+  }
+
+  if std::env::var("RUST_LOG").is_err() {
+    std::env::set_var("RUST_LOG", serai_env::var("RUST_LOG").unwrap_or_else(|| "info".to_string()));
+  }
+  env_logger::init();
+
+  log::info!("Starting Ethereum relayer server...");
+
+  // Open the DB
+  #[allow(unused_variables, unreachable_code)]
+  let db = {
+    #[cfg(all(feature = "parity-db", feature = "rocksdb"))]
+    panic!("built with parity-db and rocksdb");
+    #[cfg(all(feature = "parity-db", not(feature = "rocksdb")))]
+    let db =
+      serai_db::new_parity_db(&serai_env::var("DB_PATH").expect("path to DB wasn't specified"));
+    #[cfg(feature = "rocksdb")]
+    let db =
+      serai_db::new_rocksdb(&serai_env::var("DB_PATH").expect("path to DB wasn't specified"));
+    db
+  };
+
+  // Start command recipience server
+  // This should not be publicly exposed
+  // TODO: Add auth
+  tokio::spawn({
+    let db = db.clone();
+    async move {
+      // 5132 ^ ((b'E' << 8) | b'R')
+      let server = TcpListener::bind("0.0.0.0:20830").await.unwrap();
+      loop {
+        let (mut socket, _) = server.accept().await.unwrap();
+        let db = db.clone();
+        tokio::spawn(async move {
+          let mut db = db.clone();
+          loop {
+            let Ok(msg_len) = socket.read_u32_le().await else { break };
+            let mut buf = vec![0; usize::try_from(msg_len).unwrap()];
+            let Ok(_) = socket.read_exact(&mut buf).await else { break };
+
+            if buf.len() < 5 {
+              break;
+            }
+            let nonce = u32::from_le_bytes(buf[.. 4].try_into().unwrap());
+            let mut txn = db.txn();
+            txn.put(nonce.to_le_bytes(), &buf[4 ..]);
+            txn.commit();
+
+            let Ok(()) = socket.write_all(&[1]).await else { break };
+
+            log::info!("received signed command #{nonce}");
+          }
+        });
+      }
+    }
+  });
+
+  // Start command fetch server
+  // 5132 ^ ((b'E' << 8) | b'R') + 1
+  let server = TcpListener::bind("0.0.0.0:20831").await.unwrap();
+  loop {
+    let (mut socket, _) = server.accept().await.unwrap();
+    let db = db.clone();
+    tokio::spawn(async move {
+      let db = db.clone();
+      loop {
+        // Nonce to get the router comamnd for
+        let mut buf = vec![0; 4];
+        let Ok(_) = socket.read_exact(&mut buf).await else { break };
+
+        let command = db.get(&buf[.. 4]).unwrap_or(vec![]);
+        let Ok(()) = socket.write_all(&u32::try_from(command.len()).unwrap().to_le_bytes()).await
+        else {
+          break;
+        };
+        let Ok(()) = socket.write_all(&command).await else { break };
+      }
+    });
+  }
+}