fix(muxer): Return better error message when the peer closes the connection

connection.go

@@ -285,9 +285,10 @@ func (c *Connection) setupConnection() error {
 			if !ok {
 				return
 			}
-			if errors.Is(err, io.EOF) || errors.Is(err, io.ErrUnexpectedEOF) {
-				// Return a bare io.EOF error if error is EOF/ErrUnexpectedEOF
-				c.errorChan <- io.EOF
+			var connErr *muxer.ConnectionClosedError
+			if errors.As(err, &connErr) {
+				// Pass through ConnectionClosedError from muxer
+				c.errorChan <- err
 			} else {
 				// Wrap error message to denote it comes from the muxer
 				c.errorChan <- fmt.Errorf("muxer error: %w", err)
@@ -354,7 +355,7 @@ func (c *Connection) setupConnection() error {
 	select {
 	case <-c.doneChan:
 		// Return an error if we're shutting down
-		return io.EOF
+		return fmt.Errorf("connection shutdown initiated: %w", io.EOF)
 	case err := <-c.protoErrorChan:
 		// Shutdown the connection and return the error
 		c.Close()

muxer/muxer.go

@@ -69,6 +69,19 @@ type Muxer struct {
 	onceStop               sync.Once
 }
 
+type ConnectionClosedError struct {
+	Context string
+	Err     error
+}
+
+func (e *ConnectionClosedError) Error() string {
+	return fmt.Sprintf("peer closed the connection while %s: %v", e.Context, e.Err)
+}
+
+func (e *ConnectionClosedError) Unwrap() error {
+	return e.Err
+}
+
 // New creates a new Muxer object and starts the read loop
 func New(conn net.Conn) *Muxer {
 	m := &Muxer{
@@ -287,7 +300,11 @@ func (m *Muxer) readLoop() {
 			if errors.Is(err, io.ErrClosedPipe) {
 				err = io.EOF
 			}
-			m.sendError(err)
+			if errors.Is(err, io.EOF) {
+				m.sendError(&ConnectionClosedError{Context: "reading header", Err: err})
+			} else {
+				m.sendError(err)
+			}
 			return
 		}
 		msg := &Segment{
@@ -300,7 +317,11 @@ func (m *Muxer) readLoop() {
 			if errors.Is(err, io.ErrClosedPipe) {
 				err = io.EOF
 			}
-			m.sendError(err)
+			if errors.Is(err, io.EOF) {
+				m.sendError(&ConnectionClosedError{Context: "reading payload", Err: err})
+			} else {
+				m.sendError(err)
+			}
 			return
 		}
 		// Check for message from initiator when we're not configured as a responder