keyforkd: appropriately handle or debug disconnects

crates/daemon/keyforkd/src/server.rs

@@ -1,6 +1,9 @@
 //! A UNIX socket server to run a Tower Service.
 
-use keyfork_frame::asyncext::{try_decode_from, try_encode_to};
+use keyfork_frame::{
+    asyncext::{try_decode_from, try_encode_to},
+    DecodeError, EncodeError,
+};
 use std::{
     io::Error,
     path::{Path, PathBuf},
@@ -17,6 +20,34 @@ pub struct UnixServer {
     listener: UnixListener,
 }
 
+/// This feels like a hack, but this is a convenient way to use the same method to quickly verify
+/// something across two different error types.
+trait IsDisconnect {
+    fn is_disconnect(&self) -> bool;
+}
+
+impl IsDisconnect for DecodeError {
+    fn is_disconnect(&self) -> bool {
+        if let Self::Io(e) = self {
+            if let std::io::ErrorKind::UnexpectedEof = e.kind() {
+                return true;
+            }
+        }
+        false
+    }
+}
+
+impl IsDisconnect for EncodeError {
+    fn is_disconnect(&self) -> bool {
+        if let Self::Io(e) = self {
+            if let std::io::ErrorKind::UnexpectedEof = e.kind() {
+                return true;
+            }
+        }
+        false
+    }
+}
+
 impl UnixServer {
     /// Bind a socket to the given `address` and create a [`UnixServer`]. This function also creates a ctrl_c handler to automatically clean up the socket file.
     ///
@@ -68,11 +99,19 @@ impl UnixServer {
             #[cfg(feature = "tracing")]
             debug!("new socket connected");
             tokio::spawn(async move {
+                let mut has_processed_request = false;
                 // Process requests until an error occurs or a client disconnects
                 loop {
                     let bytes = match try_decode_from(&mut socket).await {
                         Ok(bytes) => bytes,
                         Err(e) => {
+                            if e.is_disconnect() {
+                                #[cfg(feature = "tracing")]
+                                if !has_processed_request {
+                                    debug!("client disconnected before sending any response");
+                                }
+                                return;
+                            }
                             #[cfg(feature = "tracing")]
                             debug!(%e, "Error reading DerivationPath from socket");
                             let content = e.to_string().bytes().collect::<Vec<_>>();
@@ -109,17 +148,36 @@ impl UnixServer {
                             let result = try_encode_to(&content[..], &mut socket).await;
                             #[cfg(feature = "tracing")]
                             if let Err(error) = result {
+                                if error.is_disconnect() {
+                                    #[cfg(feature = "tracing")]
+                                    if has_processed_request {
+                                        debug!("client disconnected while sending error frame");
+                                    }
+                                    return;
+                                }
                                 debug!(%error, "Error sending error to client");
                             }
-                            return;
+                            has_processed_request = true;
+                            // The error has been successfully sent, the client may perform
+                            // another request.
+                            continue;
                         }
                     }
                     .into();
 
                     if let Err(e) = try_encode_to(&response[..], &mut socket).await {
+                        if e.is_disconnect() {
+                            #[cfg(feature = "tracing")]
+                            if has_processed_request {
+                                debug!("client disconnected while sending success frame");
+                            }
+                            return;
+                        }
                         #[cfg(feature = "tracing")]
                         debug!(%e, "Error sending response to client");
                     }
+
+                    has_processed_request = true;
                 }
             });
         }