Method Write

conn.go:1348–1415

Write writes data to the connection. As Write calls Handshake, in order to prevent indefinite blocking a deadline must be set for both Read and Write before Write is called when the handshake has not yet completed. See SetDeadline, SetReadDeadline, and SetWriteDeadline.

(b []byte)

// has not yet completed. See SetDeadline, SetReadDeadline, and
// SetWriteDeadline.
func (c *Conn) Write(b []byte) (int, error) {
	if c.DirectOut {
		if s := len(b) - 31; s >= 0 && b[s] == 21 {
			if b[s+1] == 3 && b[s+2] == 3 && b[s+3] == 0 && b[s+4] == 26 {
				if c.SHOW {
					fmt.Println(c.MARK, "discarded 21 3 3 0 26 at s =", s)
				}
				c.conn.Write(b[:s])
				return s + 31, nil
			}
		}
		return c.conn.Write(b)
	}

	// interlock with Close below
	for {
		x := atomic.LoadInt32(&c.activeCall)
		if x&1 != 0 {
			return 0, net.ErrClosed
		}
		if atomic.CompareAndSwapInt32(&c.activeCall, x, x+2) {
			break
		}
	}
	defer atomic.AddInt32(&c.activeCall, -2)

	if err := c.Handshake(); err != nil {
		return 0, err
	}

	c.out.Lock()
	defer c.out.Unlock()

	if err := c.out.err; err != nil {
		return 0, err
	}

	if !c.handshakeComplete() {
		return 0, alertInternalError
	}

	if c.closeNotifySent {
		return 0, errShutdown
	}

	// TLS 1.0 is susceptible to a chosen-plaintext
	// attack when using block mode ciphers due to predictable IVs.
	// This can be prevented by splitting each Application Data
	// record into two records, effectively randomizing the IV.
	//
	// https://www.openssl.org/~bodo/tls-cbc.txt
	// https://bugzilla.mozilla.org/show_bug.cgi?id=665814
	// https://www.imperialviolet.org/2012/01/15/beastfollowup.html

	var m int
	if len(b) > 1 && c.vers == VersionTLS10 {
		if _, ok := c.out.cipher.(cipher.BlockMode); ok {
			n, err := c.writeRecordLocked(recordTypeApplicationData, b[:1])