/* queue.c --
 * Copyright 2007,2013,2015 Red Hat Inc., Durham, North Carolina.
 * All Rights Reserved.
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
 *
 * Authors:
 *      Steve Grubb <sgrubb@redhat.com>
 */

#include "config.h"
#include <pthread.h>
#include <stdlib.h>
#include <unistd.h>
#include <syslog.h>
#include "queue.h"

static volatile event_t **q;
static pthread_mutex_t queue_lock;
static pthread_cond_t queue_nonempty;
static unsigned int q_next, q_last, q_depth, processing_suspended;
static const char *SINGLE = "1";
static const char *HALT = "0";
static int queue_full_warning = 0;
extern volatile int hup;
#define QUEUE_FULL_LIMIT 5

void reset_suspended(void)
{
	processing_suspended = 0;
	queue_full_warning = 0;
}

int init_queue(unsigned int size)
{
	unsigned int i;

	processing_suspended = 0;
	q_next = 0;
	q_last = 0;
	q_depth = size;
	q = malloc(q_depth * sizeof(event_t *));
	if (q == NULL)
		return -1;

	for (i=0; i<q_depth; i++) 
		q[i] = NULL;

	/* Setup IPC mechanisms */
	pthread_mutex_init(&queue_lock, NULL);
	pthread_cond_init(&queue_nonempty, NULL);

	return 0;
}

static void change_runlevel(const char *level)
{
	char *argv[3];
	int pid;
	static const char *init_pgm = "/sbin/init";

	pid = fork();
	if (pid < 0) {
		syslog(LOG_ALERT, "Audispd failed to fork switching runlevels");
		return;
	}
	if (pid)	/* Parent */
		return;
	/* Child */
	argv[0] = (char *)init_pgm;
	argv[1] = (char *)level;
	argv[2] = NULL;
	execve(init_pgm, argv, NULL);
	syslog(LOG_ALERT, "Audispd failed to exec %s", init_pgm);
	exit(1);
}

static void do_overflow_action(struct daemon_conf *config)
{
        switch (config->overflow_action)
        {
                case O_IGNORE:
			break;
                case O_SYSLOG:
			if (queue_full_warning < QUEUE_FULL_LIMIT) {
				syslog(LOG_ERR,
					"queue is full - dropping event");
				queue_full_warning++;
				if (queue_full_warning == QUEUE_FULL_LIMIT)
					syslog(LOG_ERR,
						"audispd queue full reporting "
						"limit reached - ending "
						"dropped event notifications");
			}
                        break;
                case O_SUSPEND:
                        syslog(LOG_ALERT,
                            "Audispd is suspending event processing due to overflowing its queue.");
                        processing_suspended = 1;
                        break;
                case O_SINGLE:
                        syslog(LOG_ALERT,
                                "Audisp is now changing the system to single user mode due to overflowing its queue");
                        change_runlevel(SINGLE);
                        break;
                case O_HALT:
                        syslog(LOG_ALERT,
                                "Audispd is now halting the system due to overflowing its queue");
                        change_runlevel(HALT);
                        break;
                default:
                        syslog(LOG_ALERT, "Unknown overflow action requested");
                        break;
        }
}

void enqueue(event_t *e, struct daemon_conf *config)
{
	unsigned int n, retry_cnt = 0;

	if (processing_suspended) {
		free(e);
		return;
	}

retry:
	// We allow 3 retries and then its over
	if (retry_cnt > 3) {
		do_overflow_action(config);
		free(e);
		return;
	}
	pthread_mutex_lock(&queue_lock);

	// OK, have lock add event
	n = q_next%q_depth;
	if (q[n] == NULL) {
		q[n] = e;
		q_next = (n+1) % q_depth;
		pthread_cond_signal(&queue_nonempty);
		pthread_mutex_unlock(&queue_lock);
	} else {
		pthread_mutex_unlock(&queue_lock);
		struct timespec ts;
		ts.tv_sec = 0;
		ts.tv_nsec = 2 * 1000 * 1000; // 2 milliseconds
		nanosleep(&ts, NULL); /* Let other thread try to log it. */
		retry_cnt++;
		goto retry;
	}
}

event_t *dequeue(void)
{
	event_t *e;
	unsigned int n;

	// Wait until its got something in it
	pthread_mutex_lock(&queue_lock);
	if (hup) {
		pthread_mutex_unlock(&queue_lock);
		return NULL;
	}
	n = q_last%q_depth;
	if (q[n] == NULL) {
		pthread_cond_wait(&queue_nonempty, &queue_lock);
		n = q_last%q_depth;
	}

	// OK, grab the next event
	if (q[n] != NULL) {
		e = (event_t *)q[n];
		q[n] = NULL;
		q_last = (n+1) % q_depth;
	} else
		e = NULL;

	pthread_mutex_unlock(&queue_lock);

	// Process the event
	return e;
}

void nudge_queue(void)
{
	pthread_cond_signal(&queue_nonempty);
}

void increase_queue_depth(unsigned int size)
{
	pthread_mutex_lock(&queue_lock);
	if (size > q_depth) {
		int i;
		void *tmp_q;

		tmp_q = realloc(q, size * sizeof(event_t *));
		q = tmp_q;
		for (i=q_depth; i<size; i++)
			q[i] = NULL;
		q_depth = size;
	}
	pthread_mutex_unlock(&queue_lock);
}

void destroy_queue(void)
{
	unsigned int i;

	for (i=0; i<q_depth; i++)
		free((void *)q[i]);

	free(q);
}