/*
 * Copyright (c) 2008, Stefan Walter
 * All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 *
 *     * Redistributions of source code must retain the above
 *       copyright notice, this list of conditions and the
 *       following disclaimer.
 *     * Redistributions in binary form must reproduce the
 *       above copyright notice, this list of conditions and
 *       the following disclaimer in the documentation and/or
 *       other materials provided with the distribution.
 *     * The names of contributors to this software may not be
 *       used to endorse or promote products derived from this
 *       software without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
 * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
 * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
 * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
 * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
 * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
 * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
 * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
 * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF
 * THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH
 * DAMAGE.
 */

#include "config.h"

#include "plugin.h"

#include <sys/wait.h>

#include <stdarg.h>
#include <string.h>
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
#include <errno.h>
#include <unistd.h>
#include <signal.h>
#include <ctype.h>

/*----------------------------------------------------------------------------------
 * DECLARATIONS
 */

static const char *dnsnotify_soa_attribute = "sOARecord";
static const char *dnsnotify_ns_attribute = "nSRecord";
static const char *dnsnotify_zone_attribute = "associatedDomain";
static int dnsnotify_enable = 1;
static int dnsnotify_delay = 5;

static Slapi_Mutex *dnsnotify_mutex = NULL;
static int dnsnotify_pipe = -1;
static pid_t dnsnotify_pid = -1;


/* ---------------------------------------------------------------------------------
 * OPERATIONS
 */

static int
load_zone_attributes (const char *dn, char **zone_result, char ***ns_result)
{
	Slapi_Entry **entries;
	struct berval **values, **v;
	Slapi_PBlock *pb;
	Slapi_Attr *attr;
	LDAPControl *ctrl;
	char *attrs[4];
	char *zone, **ns;
	int rc, code, num, i;

	trace (dn);
	assert (dn && dn[0]);
	assert (dnsnotify_ns_attribute);
	assert (dnsnotify_zone_attribute);

	ctrl = NULL; /* No controls */
	attrs[0] = (char*)dnsnotify_zone_attribute;
	attrs[1] = (char*)dnsnotify_ns_attribute;
	attrs[2] = NULL;

	trace ("performing internal search");

	/* Do the actual search */
	pb = slapi_search_internal ((char*)dn, LDAP_SCOPE_BASE, "(objectClass=*)", &ctrl, attrs, 0);
	return_val_if_fail (pb, 0);

	/* Was it successful? */
	code = -1;
	rc = slapi_pblock_get (pb, SLAPI_PLUGIN_INTOP_RESULT, &code);
	return_val_if_fail (rc >= 0, 0);
	if (code != LDAP_SUCCESS) {
		log_plugin ("error loading attribute %s from %s (code %d)", dnsnotify_zone_attribute, dn, code);
		slapi_pblock_destroy (pb);
		trace ("failure");
		return 0;
	}

	/* Dig out all the entries */
	entries = NULL;
	slapi_pblock_get (pb, SLAPI_PLUGIN_INTOP_SEARCH_ENTRIES, &entries);
	return_val_if_fail (entries, 0);

	zone = NULL;
	ns = NULL;
	if (entries[0]) {
		if (slapi_entry_attr_find (entries[0], (char*)dnsnotify_zone_attribute, &attr) >= 0 && attr &&
		    slapi_attr_get_values (attr, &values) >= 0 && values && values[0]) {

			/* Convert the berval into a string */
			zone = slapi_ch_malloc (values[0]->bv_len + 1);
			if (values[0]->bv_len)
				memcpy (zone, values[0]->bv_val, values[0]->bv_len);
			zone[values[0]->bv_len] = 0;
		}

		if (slapi_entry_attr_find (entries[0], (char*)dnsnotify_ns_attribute, &attr) >= 0 && attr &&
		    slapi_attr_get_values (attr, &values) >= 0 && values) {

			num = 0;
			for (v = values; *v; ++v)
				++num;

			ns = (char**)slapi_ch_calloc (num + 1, sizeof (char*));
			for (i = 0; i < num; ++i) {
				ns[i] = slapi_ch_malloc (values[i]->bv_len + 1);
				if (values[i]->bv_len)
					memcpy (ns[i], values[i]->bv_val, values[i]->bv_len);
				ns[i][values[i]->bv_len] = 0;
			}

			/* Null terminate */
			ns[i] = NULL;
		}
	}

	slapi_pblock_destroy (pb);

	/* Only proceed if we have all the data we need */
	if (zone && zone[0] && ns && ns[0]) {
		*zone_result = zone;
		*ns_result = ns;
		return 1;
	}

	slapi_ch_free_string (&zone);
	slapi_ch_array_free (ns);

	return 0;
}

static void
kill_notify_process (void)
{
	int status;

	if (dnsnotify_pipe != -1)
		close (dnsnotify_pipe);
	dnsnotify_pipe = -1;

	if (dnsnotify_pid != -1) {
		if (waitpid (dnsnotify_pid, &status, WNOHANG) == 0) {
			/* We can play rough, because we know process can take it */
			if (kill (dnsnotify_pid, SIGKILL) >= 0)
				waitpid (dnsnotify_pid, &status, 0);
		}
		dnsnotify_pid = -1;
	}
}

static int
fork_notify_process (void)
{
	int open_max, fd;
	int commpipe[2];
	char *args[5];
	char delay[16];
	pid_t pid;

	if (pipe (commpipe) < 0) {
		log_plugin ("couldn't create communication pipe for child process: %s", strerror (errno));
		return -1;
	}

	pid = fork();
	switch (pid) {
	case -1:
		log_plugin ("couldn't fork for child notify process: %s", strerror (errno));
		close (commpipe[0]);
		close (commpipe[1]);
		return -1;

	/* The child, continues below */
	case 0:
		break;

	/* The parent */
	default:

		/* close read end */
		close (commpipe[0]);

		/* Kill any previous process */
		kill_notify_process ();

		/* hang onto write end, and new pid */
		dnsnotify_pipe = commpipe[1];
		dnsnotify_pid = pid;

		return 0;
	};

	/* The child process, here */
	close (commpipe[1]);

	/* Dup the pipe into stdin of the process */
	if (dup2 (commpipe[0], 0) < 0)
		log_plugin ("couldn't setup stdin on notify child process: %s", strerror (errno));

	/* Close all other file descriptors */
	open_max = sysconf (_SC_OPEN_MAX);
	for (fd = 3; fd < open_max; ++fd)
		close (fd);

	snprintf (delay, sizeof (delay), "-w%d", dnsnotify_delay);

	args[0] = DNS_NOTIFY_PATH;
	args[1] = "-s";
	args[2] = delay;
	args[3] = NULL;

	execv (args[0], args);
	log_plugin ("couldn't launch '%s' process: %s", DNS_NOTIFY_PATH, strerror (errno));
	_exit (1);
}

static ssize_t
write_all (int fd, const void *b, size_t len)
{
	const unsigned char *buf = (const unsigned char*)b;
	ssize_t l, left = len;

	while (left > 0) {
		l = write (fd, buf, len);
		if (l < 0) {
			if (errno == EINTR && errno == EAGAIN)
				continue;
			return -1;
		} else {
			left -= l;
			buf += l;
		}
	}

	return len;
}

static void
notify_dns_slaves (char *zone, char **ns)
{
	int i, complete = 1;
	char *n;

	trace (zone);

	assert (ns);
	assert (zone && zone[0]);

	if (!*ns)
		return;

	slapi_lock_mutex (dnsnotify_mutex);

		/* Try this twice in case things have closed up shop */
		for (i = 0; i < 2; ++i) {

			if (dnsnotify_pipe < 0 || i > 0)
				if (fork_notify_process () < 0)
					break;

			assert (dnsnotify_pipe >= 0);

			for (; *ns; ++ns) {
				n = *ns;

				/* An empty string ? */
				while (n[0] && isspace (n[0]))
					++n;
				if (!n[0])
					continue;

				if (write_all (dnsnotify_pipe, "NOTIFY: ", 8) < 0 ||
				    write_all (dnsnotify_pipe, zone, strlen (zone)) < 0 ||
				    write_all (dnsnotify_pipe, " ", 1) < 0 ||
				    write_all (dnsnotify_pipe, n, strlen (n)) < 0 ||
				    write_all (dnsnotify_pipe, "\n", 1) < 0) {
					if (errno == EPIPE) {
						complete = 0;
						break;
					}
					log_plugin ("couldn't write data to child notify process: %s", strerror (errno));
				}
			}

			if (complete)
				break;
		}

	slapi_unlock_mutex (dnsnotify_mutex);
}

void
dnsnotify_post_modify (const char *dn, LDAPMod **mods)
{
	LDAPMod **m, *mod;
	char *zone, **ns;

	return_if_fail (dn && dn[0]);
	return_if_fail (mods);

	if (!dnsnotify_enable)
		return;

	for (m = mods; *m; ++m) {
		mod = *m;
		if (mod->mod_type &&
		    strcasecmp (mod->mod_type, dnsnotify_soa_attribute) == 0) {
			if (load_zone_attributes (dn, &zone, &ns)) {
				notify_dns_slaves (zone, ns);
				slapi_ch_array_free (ns);
				slapi_ch_free_string (&zone);
			}
			break;
		}
	}
}

void
dnsnotify_post_add (const char *dn)
{
	char *zone, **ns;

	return_if_fail (dn);

	if (!dnsnotify_enable)
		return;

	/* A DN that is an SOA? */
	if (load_zone_attributes (dn, &zone, &ns)) {
		notify_dns_slaves (zone, ns);
		slapi_ch_free_string (&zone);
		slapi_ch_array_free (ns);
	}
}

int
dnsnotify_config (const char *name, const char *value)
{
	return_val_if_fail (name, 0);

	if (strcmp (name, "soa-attribute") == 0 && value) {
		dnsnotify_soa_attribute = value;
		return 1;

	} else if (strcmp (name, "ns-attribute") == 0 && value) {
		dnsnotify_ns_attribute = value;
		return 1;

	} else if (strcmp (name, "zone-attribute") == 0 && value) {
		dnsnotify_zone_attribute = value;
		return 1;
	}

	else if (strcmp (name, "notify-delay") == 0 && value) {
		dnsnotify_delay = atoi (value);
		return 1;
	}

	else if (strcmp (name, "disable-notify") == 0 && !value) {
		dnsnotify_enable = 0;
		return 1;
	}

	return 0;
}

int
dnsnotify_init (void)
{
	if (!dnsnotify_ns_attribute || !dnsnotify_ns_attribute[0]) {
		log_plugin ("SOA or NS attribute specified for plugin is empty");
		return -1;
	}

	assert (!dnsnotify_mutex);
	dnsnotify_mutex = slapi_new_mutex ();
	return_val_if_fail (dnsnotify_mutex, -1);

	return 0;
}


void
dnsnotify_destroy (void)
{
	if (dnsnotify_mutex)
		slapi_lock_mutex (dnsnotify_mutex);

	kill_notify_process ();

	if (dnsnotify_mutex) {
		slapi_unlock_mutex (dnsnotify_mutex);
		slapi_destroy_mutex (dnsnotify_mutex);
		dnsnotify_mutex = NULL;
	}
}