Ensure the TCP read buffer is fully initialized before handling each packet.

(closes issue #14452)
Reported by: umberto71


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@203779 65c4cc65-6c06-0410-ace0-fbb531ad65f3

channels/chan_sip.c

@@ -2903,6 +2903,8 @@ static void *_sip_tcp_helper_thread(struct sip_pvt *pvt, struct ast_tcptls_sessi
 		reqcpy.data = str_save;
 		ast_str_reset(reqcpy.data);
 
+		memset(buf, 0, sizeof(buf));
+
 		if (tcptls_session->ssl) {
 			set_socket_transport(&req.socket, SIP_TRANSPORT_TLS);
 			req.socket.port = htons(ourport_tls);