dial: Connect() does not cancel by context if no i/o

NetDialer, GreetingDialer, AuthDialer and ProtocolDialer may not
cancel Dial() on context expiration when network connection hangs.

The issue occurred because context wasn't properly handled during
network I/O operations, potentially causing infinite waiting.

Part of TNTP-2018

Author: oleg-jukovec

CHANGELOG.md

@@ -14,14 +14,17 @@ Versioning](http://semver.org/spec/v2.0.0.html) except to the first release.
 
 ### Fixed
 
+- Connect() may not cancel Dial() call on context expiration if network
+  connection hangs (#443).
+
 ## [v2.3.1] - 2025-04-03
 
 The patch releases fixes expected Connect() behavior and reduces allocations.
 
 ### Added
 
 - A usage of sync.Pool of msgpack.Decoder saves 2 object allocations per
-  a response decoding.
+  a response decoding (#440).
 
 ### Changed
 

connection.go

@@ -489,7 +489,7 @@ func (conn *Connection) dial(ctx context.Context) error {
 		}
 
 		req := newWatchRequest(key.(string))
-		if err = writeRequest(c, req); err != nil {
+		if err = writeRequest(ctx, c, req); err != nil {
 			st <- state
 			return false
 		}

dial.go

@@ -289,6 +289,7 @@ func (d AuthDialer) Dial(ctx context.Context, opts DialOpts) (Conn, error) {
 	if err != nil {
 		return conn, err
 	}
+
 	greeting := conn.Greeting()
 	if greeting.Salt == "" {
 		conn.Close()
@@ -309,7 +310,7 @@ func (d AuthDialer) Dial(ctx context.Context, opts DialOpts) (Conn, error) {
 		}
 	}
 
-	if err := authenticate(conn, d.Auth, d.Username, d.Password,
+	if err := authenticate(ctx, conn, d.Auth, d.Username, d.Password,
 		conn.Greeting().Salt); err != nil {
 		conn.Close()
 		return nil, fmt.Errorf("failed to authenticate: %w", err)
@@ -340,7 +341,7 @@ func (d ProtocolDialer) Dial(ctx context.Context, opts DialOpts) (Conn, error) {
 		protocolInfo: d.RequiredProtocolInfo,
 	}
 
-	protocolConn.protocolInfo, err = identify(&protocolConn)
+	protocolConn.protocolInfo, err = identify(ctx, &protocolConn)
 	if err != nil {
 		protocolConn.Close()
 		return nil, fmt.Errorf("failed to identify: %w", err)
@@ -372,11 +373,12 @@ func (d GreetingDialer) Dial(ctx context.Context, opts DialOpts) (Conn, error) {
 	greetingConn := greetingConn{
 		Conn: conn,
 	}
-	version, salt, err := readGreeting(greetingConn)
+	version, salt, err := readGreeting(ctx, &greetingConn)
 	if err != nil {
 		greetingConn.Close()
 		return nil, fmt.Errorf("failed to read greeting: %w", err)
 	}
+
 	greetingConn.greeting = Greeting{
 		Version: version,
 		Salt:    salt,
@@ -410,31 +412,67 @@ func parseAddress(address string) (string, string) {
 	return network, address
 }
 
+// ioWaiter waits in a background until an io operation done or a context
+// is expired. It closes the connection and writes a context error into the
+// output channel on context expiration.
+//
+// A user of the helper should close the first output channel after an IO
+// operation done and read an error from a second channel to get the result
+// of waiting.
+func ioWaiter(ctx context.Context, conn Conn) (chan<- struct{}, <-chan error) {
+	doneIO   := make(chan struct{})
+	doneWait := make(chan error, 1)
+
+	go func() {
+		defer close(doneWait)
+
+		select {
+		case <-ctx.Done():
+			conn.Close()
+			<-doneIO
+			doneWait <- ctx.Err()
+		case <-doneIO:
+			doneWait <- nil
+		}
+	}()
+
+	return doneIO, doneWait
+}
+
 // readGreeting reads a greeting message.
-func readGreeting(reader io.Reader) (string, string, error) {
+func readGreeting(ctx context.Context, conn Conn) (string, string, error) {
 	var version, salt string
 
+	doneRead, doneWait := ioWaiter(ctx, conn)
+
 	data := make([]byte, 128)
-	_, err := io.ReadFull(reader, data)
+	_, err := io.ReadFull(conn, data)
+
+	close(doneRead)
+
 	if err == nil {
 		version = bytes.NewBuffer(data[:64]).String()
 		salt = bytes.NewBuffer(data[64:108]).String()
 	}
 
+	if waitErr := <-doneWait; waitErr != nil {
+		err = waitErr
+	}
+
 	return version, salt, err
 }
 
 // identify sends info about client protocol, receives info
 // about server protocol in response and stores it in the connection.
-func identify(conn Conn) (ProtocolInfo, error) {
+func identify(ctx context.Context, conn Conn) (ProtocolInfo, error) {
 	var info ProtocolInfo
 
 	req := NewIdRequest(clientProtocolInfo)
-	if err := writeRequest(conn, req); err != nil {
+	if err := writeRequest(ctx, conn, req); err != nil {
 		return info, err
 	}
 
-	resp, err := readResponse(conn, req)
+	resp, err := readResponse(ctx, conn, req)
 	if err != nil {
 		if resp != nil &&
 			resp.Header().Error == iproto.ER_UNKNOWN_REQUEST_TYPE {
@@ -495,7 +533,7 @@ func checkProtocolInfo(required ProtocolInfo, actual ProtocolInfo) error {
 }
 
 // authenticate authenticates for a connection.
-func authenticate(c Conn, auth Auth, user string, pass string, salt string) error {
+func authenticate(ctx context.Context, c Conn, auth Auth, user, pass, salt string) error {
 	var req Request
 	var err error
 
@@ -511,37 +549,73 @@ func authenticate(c Conn, auth Auth, user string, pass string, salt string) erro
 		return errors.New("unsupported method " + auth.String())
 	}
 
-	if err = writeRequest(c, req); err != nil {
+	if err = writeRequest(ctx, c, req); err != nil {
 		return err
 	}
-	if _, err = readResponse(c, req); err != nil {
+	if _, err = readResponse(ctx, c, req); err != nil {
 		return err
 	}
 	return nil
 }
 
 // writeRequest writes a request to the writer.
-func writeRequest(w writeFlusher, req Request) error {
+func writeRequest(ctx context.Context, conn Conn, req Request) error {
 	var packet smallWBuf
 	err := pack(&packet, msgpack.NewEncoder(&packet), 0, req, ignoreStreamId, nil)
 
 	if err != nil {
 		return fmt.Errorf("pack error: %w", err)
 	}
-	if _, err = w.Write(packet.b); err != nil {
+
+	doneWrite, doneWait := ioWaiter(ctx, conn)
+
+	_, err = conn.Write(packet.b)
+
+	close(doneWrite)
+
+	if waitErr := <-doneWait; waitErr != nil {
+		err = waitErr
+	}
+
+	if err != nil {
 		return fmt.Errorf("write error: %w", err)
 	}
-	if err = w.Flush(); err != nil {
+
+	doneWrite, doneWait = ioWaiter(ctx, conn)
+
+	err = conn.Flush()
+
+	close(doneWrite)
+
+	if waitErr := <-doneWait; waitErr != nil {
+		err = waitErr
+	}
+
+	if err != nil {
 		return fmt.Errorf("flush error: %w", err)
 	}
+
+	if waitErr := <-doneWait; waitErr != nil {
+		err = waitErr
+	}
+
 	return err
 }
 
 // readResponse reads a response from the reader.
-func readResponse(r io.Reader, req Request) (Response, error) {
+func readResponse(ctx context.Context, conn Conn, req Request) (Response, error) {
 	var lenbuf [packetLengthBytes]byte
 
-	respBytes, err := read(r, lenbuf[:])
+	doneRead, doneWait := ioWaiter(ctx, conn)
+
+	respBytes, err := read(conn, lenbuf[:])
+
+	close(doneRead)
+
+	if waitErr := <-doneWait; waitErr != nil {
+		err = waitErr
+	}
+
 	if err != nil {
 		return nil, fmt.Errorf("read error: %w", err)
 	}
@@ -555,10 +629,12 @@ func readResponse(r io.Reader, req Request) (Response, error) {
 	if err != nil {
 		return nil, fmt.Errorf("decode response header error: %w", err)
 	}
+
 	resp, err := req.Response(header, &buf)
 	if err != nil {
 		return nil, fmt.Errorf("creating response error: %w", err)
 	}
+
 	_, err = resp.Decode()
 	if err != nil {
 		switch err.(type) {
@@ -568,5 +644,6 @@ func readResponse(r io.Reader, req Request) (Response, error) {
 			return resp, fmt.Errorf("decode response body error: %w", err)
 		}
 	}
+
 	return resp, nil
 }