netconn: Disable read limit on WebSocket

Closes #245

Author: nhooyr

Diff for: netconn.go

@@ -38,7 +38,11 @@ import (
 //
 // A received StatusNormalClosure or StatusGoingAway close frame will be translated to
 // io.EOF when reading.
+//
+// Furthermore, the ReadLimit is set to -1 to disable it.
 func NetConn(ctx context.Context, c *Conn, msgType MessageType) net.Conn {
+	c.SetReadLimit(-1)
+
 	nc := &netConn{
 		c:       c,
 		msgType: msgType,

Diff for: read.go

@@ -69,10 +69,16 @@ func (c *Conn) CloseRead(ctx context.Context) context.Context {
 // By default, the connection has a message read limit of 32768 bytes.
 //
 // When the limit is hit, the connection will be closed with StatusMessageTooBig.
+//
+// Set to -1 to disable.
 func (c *Conn) SetReadLimit(n int64) {
-	// We add read one more byte than the limit in case
-	// there is a fin frame that needs to be read.
-	c.msgReader.limitReader.limit.Store(n + 1)
+	if n >= 0 {
+		// We read one more byte than the limit in case
+		// there is a fin frame that needs to be read.
+		n++
+	}
+
+	c.msgReader.limitReader.limit.Store(n)
 }
 
 const defaultReadLimit = 32768
@@ -450,7 +456,11 @@ func (lr *limitReader) reset(r io.Reader) {
 }
 
 func (lr *limitReader) Read(p []byte) (int, error) {
-	if lr.n <= 0 {
+	if lr.n < 0 {
+		return lr.r.Read(p)
+	}
+
+	if lr.n == 0 {
 		err := fmt.Errorf("read limited at %v bytes", lr.limit.Load())
 		lr.c.writeError(StatusMessageTooBig, err)
 		return 0, err
@@ -461,6 +471,9 @@ func (lr *limitReader) Read(p []byte) (int, error) {
 	}
 	n, err := lr.r.Read(p)
 	lr.n -= int64(n)
+	if lr.n < 0 {
+		lr.n = 0
+	}
 	return n, err
 }