From 074607004079b2c7f5f61ad3f046e310ae899675 Mon Sep 17 00:00:00 2001
From: Anthony Green <agreen@starry.com>
Date: Tue, 30 Nov 2021 09:12:16 -0500
Subject: [PATCH] examples: update uds example to use tokio UnixListenerStream

tokio-stream packages a UnixListenerStream that implements
futures_core::Stream. Using this cuts down on consumer boilerplate
when using UnixStreams with a tonic server.

Refs: #856

Signed-off-by: Anthony Green <agreen@starry.com>
---
 examples/src/uds/server.rs | 93 ++++++--------------------------------
 1 file changed, 15 insertions(+), 78 deletions(-)

diff --git a/examples/src/uds/server.rs b/examples/src/uds/server.rs
index 8ffe4fa0a..187d5894f 100644
--- a/examples/src/uds/server.rs
+++ b/examples/src/uds/server.rs
@@ -1,10 +1,14 @@
 #![cfg_attr(not(unix), allow(unused_imports))]
 
-use futures::TryFutureExt;
 use std::path::Path;
 #[cfg(unix)]
 use tokio::net::UnixListener;
-use tonic::{transport::Server, Request, Response, Status};
+#[cfg(unix)]
+use tokio_stream::wrappers::UnixListenerStream;
+use tonic::{
+    transport::{server::UdsConnectInfo, Server},
+    Request, Response, Status,
+};
 
 pub mod hello_world {
     tonic::include_proto!("helloworld");
@@ -26,8 +30,13 @@ impl Greeter for MyGreeter {
     ) -> Result<Response<HelloReply>, Status> {
         #[cfg(unix)]
         {
-            let conn_info = request.extensions().get::<unix::UdsConnectInfo>().unwrap();
+            let conn_info = request.extensions().get::<UdsConnectInfo>().unwrap();
             println!("Got a request {:?} with info {:?}", request, conn_info);
+
+            // Client-side unix sockets are unnamed.
+            assert!(conn_info.peer_addr.as_ref().unwrap().is_unnamed());
+            // This should contain process credentials for the client socket.
+            assert!(conn_info.peer_cred.as_ref().is_some());
         }
 
         let reply = hello_world::HelloReply {
@@ -46,89 +55,17 @@ async fn main() -> Result<(), Box<dyn std::error::Error>> {
 
     let greeter = MyGreeter::default();
 
-    let incoming = {
-        let uds = UnixListener::bind(path)?;
-
-        async_stream::stream! {
-            loop {
-                let item = uds.accept().map_ok(|(st, _)| unix::UnixStream(st)).await;
-
-                yield item;
-            }
-        }
-    };
+    let uds = UnixListener::bind(path)?;
+    let uds_stream = UnixListenerStream::new(uds);
 
     Server::builder()
         .add_service(GreeterServer::new(greeter))
-        .serve_with_incoming(incoming)
+        .serve_with_incoming(uds_stream)
         .await?;
 
     Ok(())
 }
 
-#[cfg(unix)]
-mod unix {
-    use std::{
-        pin::Pin,
-        sync::Arc,
-        task::{Context, Poll},
-    };
-
-    use tokio::io::{AsyncRead, AsyncWrite, ReadBuf};
-    use tonic::transport::server::Connected;
-
-    #[derive(Debug)]
-    pub struct UnixStream(pub tokio::net::UnixStream);
-
-    impl Connected for UnixStream {
-        type ConnectInfo = UdsConnectInfo;
-
-        fn connect_info(&self) -> Self::ConnectInfo {
-            UdsConnectInfo {
-                peer_addr: self.0.peer_addr().ok().map(Arc::new),
-                peer_cred: self.0.peer_cred().ok(),
-            }
-        }
-    }
-
-    #[derive(Clone, Debug)]
-    pub struct UdsConnectInfo {
-        pub peer_addr: Option<Arc<tokio::net::unix::SocketAddr>>,
-        pub peer_cred: Option<tokio::net::unix::UCred>,
-    }
-
-    impl AsyncRead for UnixStream {
-        fn poll_read(
-            mut self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &mut ReadBuf<'_>,
-        ) -> Poll<std::io::Result<()>> {
-            Pin::new(&mut self.0).poll_read(cx, buf)
-        }
-    }
-
-    impl AsyncWrite for UnixStream {
-        fn poll_write(
-            mut self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-            buf: &[u8],
-        ) -> Poll<std::io::Result<usize>> {
-            Pin::new(&mut self.0).poll_write(cx, buf)
-        }
-
-        fn poll_flush(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<std::io::Result<()>> {
-            Pin::new(&mut self.0).poll_flush(cx)
-        }
-
-        fn poll_shutdown(
-            mut self: Pin<&mut Self>,
-            cx: &mut Context<'_>,
-        ) -> Poll<std::io::Result<()>> {
-            Pin::new(&mut self.0).poll_shutdown(cx)
-        }
-    }
-}
-
 #[cfg(not(unix))]
 fn main() {
     panic!("The `uds` example only works on unix systems!");