net: TCPConn.SetNoDelay, back by popular demand

R=r
CC=golang-dev
https://golang.org/cl/1880047

src/pkg/net/sock.go

@@ -129,6 +129,12 @@ func setKeepAlive(fd *netFD, keepalive bool) os.Error {
 	return setsockoptInt(fd.sysfd, syscall.SOL_SOCKET, syscall.SO_KEEPALIVE, boolint(keepalive))
 }
 
+func setNoDelay(fd *netFD, noDelay bool) os.Error {
+	fd.incref()
+	defer fd.decref()
+	return setsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_NODELAY, boolint(noDelay))
+}
+
 func setLinger(fd *netFD, sec int) os.Error {
 	var l syscall.Linger
 	if sec >= 0 {

src/pkg/net/tcpsock.go

@@ -73,7 +73,7 @@ type TCPConn struct {
 
 func newTCPConn(fd *netFD) *TCPConn {
 	c := &TCPConn{fd}
-	setsockoptInt(fd.sysfd, syscall.IPPROTO_TCP, syscall.TCP_NODELAY, 1)
+	c.SetNoDelay(true)
 	return c
 }
 
@@ -192,6 +192,17 @@ func (c *TCPConn) SetKeepAlive(keepalive bool) os.Error {
 	return setKeepAlive(c.fd, keepalive)
 }
 
+// SetNoDelay controls whether the operating system should delay
+// packet transmission in hopes of sending fewer packets
+// (Nagle's algorithm).  The default is true (no delay), meaning
+// that data is sent as soon as possible after a Write.
+func (c *TCPConn) SetNoDelay(noDelay bool) os.Error {
+	if !c.ok() {
+		return os.EINVAL
+	}
+	return setNoDelay(c.fd, noDelay)
+}
+
 // DialTCP is like Dial but can only connect to TCP networks
 // and returns a TCPConn structure.
 func DialTCP(net string, laddr, raddr *TCPAddr) (c *TCPConn, err os.Error) {