fix: Make sendReady a pointer so the Body can be swapped (#106)

Re-fixes issue fix attempted in #102.

session.go

@@ -64,7 +64,7 @@ type Session struct {
 
 	// sendCh is used to mark a stream as ready to send,
 	// or to send a header out directly.
-	sendCh chan sendReady
+	sendCh chan *sendReady
 
 	// recvDoneCh is closed when recv() exits to avoid a race
 	// between stream registration and stream shutdown
@@ -81,7 +81,7 @@ type Session struct {
 // or to directly send a header
 type sendReady struct {
 	Hdr  []byte
-	mu   *sync.Mutex // Protects Body from unsafe reads.
+	mu   sync.Mutex // Protects Body from unsafe reads.
 	Body []byte
 	Err  chan error
 }
@@ -103,7 +103,7 @@ func newSession(config *Config, conn io.ReadWriteCloser, client bool) *Session {
 		inflight:   make(map[uint32]struct{}),
 		synCh:      make(chan struct{}, config.AcceptBacklog),
 		acceptCh:   make(chan *Stream, config.AcceptBacklog),
-		sendCh:     make(chan sendReady, 64),
+		sendCh:     make(chan *sendReady, 64),
 		recvDoneCh: make(chan struct{}),
 		shutdownCh: make(chan struct{}),
 	}
@@ -375,7 +375,7 @@ func (s *Session) waitForSendErr(hdr header, body []byte, errCh chan error) erro
 		timerPool.Put(t)
 	}()
 
-	ready := sendReady{Hdr: hdr, mu: &sync.Mutex{}, Body: body, Err: errCh}
+	ready := &sendReady{Hdr: hdr, Body: body, Err: errCh}
 	select {
 	case s.sendCh <- ready:
 	case <-s.shutdownCh:
@@ -433,7 +433,7 @@ func (s *Session) sendNoWait(hdr header) error {
 	}()
 
 	select {
-	case s.sendCh <- sendReady{Hdr: hdr}:
+	case s.sendCh <- &sendReady{Hdr: hdr}:
 		return nil
 	case <-s.shutdownCh:
 		return ErrSessionShutdown
@@ -461,24 +461,22 @@ func (s *Session) send() {
 				}
 			}
 
-			if ready.mu != nil {
-				ready.mu.Lock()
-				if ready.Body != nil {
-					// Copy the body into the buffer to avoid
-					// holding a mutex lock during the write.
-					_, err := bodyBuf.Write(ready.Body)
-					if err != nil {
-						ready.Body = nil
-						ready.mu.Unlock()
-						s.logger.Printf("[ERR] yamux: Failed to copy body into buffer: %v", err)
-						asyncSendErr(ready.Err, err)
-						s.exitErr(err)
-						return
-					}
+			ready.mu.Lock()
+			if ready.Body != nil {
+				// Copy the body into the buffer to avoid
+				// holding a mutex lock during the write.
+				_, err := bodyBuf.Write(ready.Body)
+				if err != nil {
 					ready.Body = nil
+					ready.mu.Unlock()
+					s.logger.Printf("[ERR] yamux: Failed to copy body into buffer: %v", err)
+					asyncSendErr(ready.Err, err)
+					s.exitErr(err)
+					return
 				}
-				ready.mu.Unlock()
+				ready.Body = nil
 			}
+			ready.mu.Unlock()
 
 			if bodyBuf.Len() > 0 {
 				// Send data from a body if given