tls1_heartbeat(SSL *s)
	{
	unsigned char *buf, *p;
	int ret;
	unsigned int payload = 18; /* Sequence number + random bytes */
	unsigned int padding = 16; /* Use minimum padding */

	/* Only send if peer supports and accepts HB requests... */
	if (!(s->tlsext_heartbeat & SSL_TLSEXT_HB_ENABLED) ||
	    s->tlsext_heartbeat & SSL_TLSEXT_HB_DONT_SEND_REQUESTS)
		{
		SSLerr(SSL_F_TLS1_HEARTBEAT,SSL_R_TLS_HEARTBEAT_PEER_DOESNT_ACCEPT);
		return -1;
		}

	/* ...and there is none in flight yet... */
	if (s->tlsext_hb_pending)
		{
		SSLerr(SSL_F_TLS1_HEARTBEAT,SSL_R_TLS_HEARTBEAT_PENDING);
		return -1;
		}
		
	/* ...and no handshake in progress. */
	if (SSL_in_init(s) || s->in_handshake)
		{
		SSLerr(SSL_F_TLS1_HEARTBEAT,SSL_R_UNEXPECTED_MESSAGE);
		return -1;
		}
		
	/* Check if padding is too long, payload and padding
	 * must not exceed 2^14 - 3 = 16381 bytes in total.
	 */
	OPENSSL_assert(payload + padding <= 16381);

	/* Create HeartBeat message, we just use a sequence number
	 * as payload to distuingish different messages and add
	 * some random stuff.
	 *  - Message Type, 1 byte
	 *  - Payload Length, 2 bytes (unsigned int)
	 *  - Payload, the sequence number (2 bytes uint)
	 *  - Payload, random bytes (16 bytes uint)
	 *  - Padding
	 */
	buf = OPENSSL_malloc(1 + 2 + payload + padding);
	p = buf;
	/* Message Type */
	*p++ = TLS1_HB_REQUEST;
	/* Payload length (18 bytes here) */
	s2n(payload, p);
	/* Sequence number */
	s2n(s->tlsext_hb_seq, p);
	/* 16 random bytes */
	RAND_pseudo_bytes(p, 16);
	p += 16;
	/* Random padding */
	RAND_pseudo_bytes(p, padding);

	ret = ssl3_write_bytes(s, TLS1_RT_HEARTBEAT, buf, 3 + payload + padding);
	if (ret >= 0)
		{
		if (s->msg_callback)
			s->msg_callback(1, s->version, TLS1_RT_HEARTBEAT,
				buf, 3 + payload + padding,
				s, s->msg_callback_arg);

		s->tlsext_hb_pending = 1;
		}
		
	OPENSSL_free(buf);

	return ret;
	}

Unknown