1 files changed, 89 insertions, 0 deletions
diff --git a/users/picnoir/tvix-daemon/src/main.rs b/users/picnoir/tvix-daemon/src/main.rs
new file mode 100644
index 000000000000..d41369e1b199
--- /dev/null
+++ b/users/picnoir/tvix-daemon/src/main.rs
@@ -0,0 +1,89 @@
+use anyhow::anyhow;
+use clap::Parser;
+use tokio::io::{AsyncReadExt, AsyncWriteExt};
+use tokio_listener::{self, SystemOptions, UserOptions};
+use tracing::{error, info, instrument};
+
+use nix_compat::wire::primitive;
+
+#[derive(Parser, Debug)]
+struct Cli {
+    /// Listening unix socket path
+    #[arg(short, long)]
+    socket: Option<String>,
+}
+
+#[tokio::main]
+#[instrument()]
+async fn main() {
+    tracing_subscriber::fmt().compact().try_init().unwrap();
+    let args = Cli::parse();
+
+    info!("Started Tvix daemon");
+    let addr = args
+        .socket
+        .unwrap_or_else(|| "sd_listen_unix".to_string())
+        .parse()
+        .expect("Invalid listening socket address");
+    let system_options: SystemOptions = Default::default();
+    let user_options: UserOptions = Default::default();
+    let mut listener = tokio_listener::Listener::bind(&addr, &system_options, &user_options)
+        .await
+        .unwrap();
+    info!("Listening for incoming connections on {:?}", listener);
+    while let Ok((conn, addr)) = listener.accept().await {
+        info!("Incoming connection from {addr}");
+        tokio::spawn(async move { worker(conn).await });
+    }
+}
+
+/// Worker in charge to respond a Nix client using the Nix wire
+/// protocol.
+#[instrument()]
+async fn worker<R>(mut conn: R)
+where
+    R: AsyncReadExt + AsyncWriteExt + Unpin + std::fmt::Debug,
+{
+    match perform_init_handshake(&mut conn).await {
+        Ok(_) => {
+            // TODO: process request here, dispatch to operation
+            // handler.
+            info!("Handshake done, bye now");
+        }
+        Err(e) => error!("Client handshake failed: {}", e),
+    }
+}
+
+/// Performs the initial handshake. During the handshake, the client
+/// will first send a magic u64, to which the daemon needs to respond
+/// with another magic u64.
+async fn perform_init_handshake<'a, R: 'a>(mut conn: &'a mut R) -> anyhow::Result<()>
+where
+    &'a mut R: AsyncReadExt + AsyncWriteExt + Unpin,
+{
+    let mut magic_hello = vec![0; 8];
+    conn.read(&mut magic_hello).await?;
+    if magic_hello != primitive::MAGIC_HELLO {
+        Err(anyhow!(
+            "Invalid client hello received: {:?}, expected {:?}",
+            magic_hello,
+            primitive::MAGIC_HELLO
+        ))
+    } else {
+        conn.write(&primitive::MAGIC_HELLO_RESPONSE).await?;
+        Ok(())
+    }
+}
+
+#[cfg(test)]
+mod integration_tests {
+    use nix_compat::wire::primitive;
+    #[tokio::test]
+    async fn test_init_handshake() {
+        let mut test_conn = tokio_test::io::Builder::new()
+            .read(&primitive::MAGIC_HELLO)
+            .write(&primitive::MAGIC_HELLO_RESPONSE)
+            .build();
+        crate::worker(&mut test_conn).await;
+    }
+}