tonic: implement the server Connected trait for tokio UnixStream

This impl is needed in order to use a tokio UnixStream as the
`incoming` argument in methods like
`tonic::transport::server::Router::serve_with_incoming_shutdown`

Fixes: hyperium#856

Signed-off-by: Anthony Green <agreen@starry.com>

tonic/src/request.rs

@@ -202,8 +202,8 @@ impl<T> Request<T> {
     /// Get the remote address of this connection.
     ///
     /// This will return `None` if the `IO` type used
-    /// does not implement `Connected`. This currently,
-    /// only works on the server side.
+    /// does not implement `Connected` or when using a unix domain socket.
+    /// This currently only works on the server side.
     pub fn remote_addr(&self) -> Option<SocketAddr> {
         #[cfg(feature = "transport")]
         {

tonic/src/transport/server/mod.rs

@@ -6,6 +6,8 @@ mod recover_error;
 #[cfg(feature = "tls")]
 #[cfg_attr(docsrs, doc(cfg(feature = "tls")))]
 mod tls;
+#[cfg(unix)]
+mod unix;
 
 pub use conn::{Connected, TcpConnectInfo};
 #[cfg(feature = "tls")]
@@ -17,6 +19,9 @@ pub use conn::TlsConnectInfo;
 #[cfg(feature = "tls")]
 use super::service::TlsAcceptor;
 
+#[cfg(unix)]
+pub use unix::UdsConnectInfo;
+
 use incoming::TcpIncoming;
 
 #[cfg(feature = "tls")]

tonic/src/transport/server/unix.rs

@@ -0,0 +1,31 @@
+use super::Connected;
+use std::sync::Arc;
+
+/// Connection info for Unix domain socket streams.
+///
+/// This type will be accessible through [request extensions][ext] if you're using
+/// a unix stream.
+///
+/// See [Connected] for more details.
+///
+/// [ext]: crate::Request::extensions
+/// [Connected]: crate::transport::server::Connected
+#[cfg_attr(docsrs, doc(cfg(unix)))]
+#[derive(Clone, Debug)]
+pub struct UdsConnectInfo {
+    /// Peer address. This will be "unnamed" for client unix sockets.
+    pub peer_addr: Option<Arc<tokio::net::unix::SocketAddr>>,
+    /// Process credentials for the unix socket.
+    pub peer_cred: Option<tokio::net::unix::UCred>,
+}
+
+impl Connected for tokio::net::UnixStream {
+    type ConnectInfo = UdsConnectInfo;
+
+    fn connect_info(&self) -> Self::ConnectInfo {
+        UdsConnectInfo {
+            peer_addr: self.peer_addr().ok().map(Arc::new),
+            peer_cred: self.peer_cred().ok(),
+        }
+    }
+}