7.5.1 Checking for an alert

This is a function that checks if an alert has been received in the current session.

/* This example code is placed in the public domain. */

#ifdef HAVE_CONFIG_H
#include <config.h>
#endif

#include <stdio.h>
#include <stdlib.h>
#include <gnutls/gnutls.h>

#include "examples.h"

/* This function will check whether the given return code from
 * a gnutls function (recv/send), is an alert, and will print
 * that alert.
 */
void check_alert(gnutls_session_t session, int ret)
{
	int last_alert;

	if (ret == GNUTLS_E_WARNING_ALERT_RECEIVED ||
	    ret == GNUTLS_E_FATAL_ALERT_RECEIVED) {
		last_alert = gnutls_alert_get(session);

		/* The check for renegotiation is only useful if we are 
		 * a server, and we had requested a rehandshake.
		 */
		if (last_alert == GNUTLS_A_NO_RENEGOTIATION &&
		    ret == GNUTLS_E_WARNING_ALERT_RECEIVED)
			printf("* Received NO_RENEGOTIATION alert. "
			       "Client Does not support renegotiation.\n");
		else
			printf("* Received alert '%d': %s.\n", last_alert,
			       gnutls_alert_get_name(last_alert));
	}
}