Minor flipcall refactoring.

PiperOrigin-RevId: 342768550

1 files changed, 58 insertions, 25 deletions

diff --git a/pkg/flipcall/ctrl_futex.go b/pkg/flipcall/ctrl_futex.go
index e7c3a3a0b..2e8452a02 100644
--- a/pkg/flipcall/ctrl_futex.go
+++ b/pkg/flipcall/ctrl_futex.go
@@ -40,17 +40,41 @@ func (ep *Endpoint) ctrlInit(opts ...EndpointOption) error {
 	return nil
 }
 
-type ctrlHandshakeRequest struct{}
-
-type ctrlHandshakeResponse struct{}
-
 func (ep *Endpoint) ctrlConnect() error {
 	if err := ep.enterFutexWait(); err != nil {
 		return err
 	}
-	_, err := ep.futexConnect(&ctrlHandshakeRequest{})
-	ep.exitFutexWait()
-	return err
+	defer ep.exitFutexWait()
+
+	// Write the connection request.
+	w := ep.NewWriter()
+	if err := json.NewEncoder(w).Encode(struct{}{}); err != nil {
+		return fmt.Errorf("error writing connection request: %v", err)
+	}
+	*ep.dataLen() = w.Len()
+
+	// Exchange control with the server.
+	if err := ep.futexSetPeerActive(); err != nil {
+		return err
+	}
+	if err := ep.futexWakePeer(); err != nil {
+		return err
+	}
+	if err := ep.futexWaitUntilActive(); err != nil {
+		return err
+	}
+
+	// Read the connection response.
+	var resp struct{}
+	respLen := atomic.LoadUint32(ep.dataLen())
+	if respLen > ep.dataCap {
+		return fmt.Errorf("invalid connection response length %d (maximum %d)", respLen, ep.dataCap)
+	}
+	if err := json.NewDecoder(ep.NewReader(respLen)).Decode(&resp); err != nil {
+		return fmt.Errorf("error reading connection response: %v", err)
+	}
+
+	return nil
 }
 
 func (ep *Endpoint) ctrlWaitFirst() error {
@@ -59,52 +83,61 @@ func (ep *Endpoint) ctrlWaitFirst() error {
 	}
 	defer ep.exitFutexWait()
 
-	// Wait for the handshake request.
-	if err := ep.futexSwitchFromPeer(); err != nil {
+	// Wait for the connection request.
+	if err := ep.futexWaitUntilActive(); err != nil {
 		return err
 	}
 
-	// Read the handshake request.
+	// Read the connection request.
 	reqLen := atomic.LoadUint32(ep.dataLen())
 	if reqLen > ep.dataCap {
-		return fmt.Errorf("invalid handshake request length %d (maximum %d)", reqLen, ep.dataCap)
+		return fmt.Errorf("invalid connection request length %d (maximum %d)", reqLen, ep.dataCap)
 	}
-	var req ctrlHandshakeRequest
+	var req struct{}
 	if err := json.NewDecoder(ep.NewReader(reqLen)).Decode(&req); err != nil {
-		return fmt.Errorf("error reading handshake request: %v", err)
+		return fmt.Errorf("error reading connection request: %v", err)
 	}
 
-	// Write the handshake response.
+	// Write the connection response.
 	w := ep.NewWriter()
-	if err := json.NewEncoder(w).Encode(ctrlHandshakeResponse{}); err != nil {
-		return fmt.Errorf("error writing handshake response: %v", err)
+	if err := json.NewEncoder(w).Encode(struct{}{}); err != nil {
+		return fmt.Errorf("error writing connection response: %v", err)
 	}
 	*ep.dataLen() = w.Len()
 
 	// Return control to the client.
 	raceBecomeInactive()
-	if err := ep.futexSwitchToPeer(); err != nil {
+	if err := ep.futexSetPeerActive(); err != nil {
+		return err
+	}
+	if err := ep.futexWakePeer(); err != nil {
 		return err
 	}
 
-	// Wait for the first non-handshake message.
-	return ep.futexSwitchFromPeer()
+	// Wait for the first non-connection message.
+	return ep.futexWaitUntilActive()
 }
 
 func (ep *Endpoint) ctrlRoundTrip() error {
-	if err := ep.futexSwitchToPeer(); err != nil {
+	if err := ep.enterFutexWait(); err != nil {
 		return err
 	}
-	if err := ep.enterFutexWait(); err != nil {
+	defer ep.exitFutexWait()
+
+	if err := ep.futexSetPeerActive(); err != nil {
 		return err
 	}
-	err := ep.futexSwitchFromPeer()
-	ep.exitFutexWait()
-	return err
+	if err := ep.futexWakePeer(); err != nil {
+		return err
+	}
+	return ep.futexWaitUntilActive()
 }
 
 func (ep *Endpoint) ctrlWakeLast() error {
-	return ep.futexSwitchToPeer()
+	if err := ep.futexSetPeerActive(); err != nil {
+		return err
+	}
+	return ep.futexWakePeer()
 }
 
 func (ep *Endpoint) enterFutexWait() error {