Fix race in writeFrame

nhooyr · nhooyr · commit ee6f7187ed8e · 2019-06-07T18:25:58.000-04:00
diff --git a/websocket.go b/websocket.go
@@ -632,14 +632,14 @@ func (c *Conn) writeFrame(ctx context.Context, fin bool, opcode opcode, p []byte
 		}
 	}
 
-	headerBytes := writeHeader(c.writeHeaderBuf, h)
-
 	err := c.acquireLock(ctx, c.writeFrameLock)
 	if err != nil {
 		return 0, err
 	}
 	defer c.releaseLock(c.writeFrameLock)
 
+	headerBytes := writeHeader(c.writeHeaderBuf, h)
+
 	select {
 	case <-c.closed:
 		return 0, c.closeErr

Original file line number	Diff line number	Diff line change
`@@ -632,14 +632,14 @@ func (c *Conn) writeFrame(ctx context.Context, fin bool, opcode opcode, p []byte`
`632`	`632`	`}`
`633`	`633`	`}`
`634`	`634`
`635`		`- headerBytes := writeHeader(c.writeHeaderBuf, h)`
`636`		`-`
`637`	`635`	`err := c.acquireLock(ctx, c.writeFrameLock)`
`638`	`636`	`if err != nil {`
`639`	`637`	`return 0, err`
`640`	`638`	`}`
`641`	`639`	`defer c.releaseLock(c.writeFrameLock)`
`642`	`640`
	`641`	`+ headerBytes := writeHeader(c.writeHeaderBuf, h)`
	`642`	`+`
`643`	`643`	`select {`
`644`	`644`	`case <-c.closed:`
`645`	`645`	`return 0, c.closeErr`