snmplib/snmp_alarm.c - vendor/opensource/netsnmp - Git at Google

 /*
  * snmp_alarm.c:
  */
 /* Portions of this file are subject to the following copyright(s).  See
  * the Net-SNMP's COPYING file for more details and other copyrights
  * that may apply:
  */
 /*
  * Portions of this file are copyrighted by:
  * Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
  * Use is subject to license terms specified in the COPYING file
  * distributed with the Net-SNMP package.
  */
 /** @defgroup snmp_alarm  generic library based alarm timers for various parts of an application
  *  @ingroup library
  *
  *  @{
  */
 #include <net-snmp/net-snmp-config.h>

 #if HAVE_UNISTD_H
 #include <unistd.h>
 #endif
 #include <signal.h>
 #if HAVE_STDLIB_H
 #include <stdlib.h>
 #endif
 #include <sys/types.h>
 #if HAVE_NETINET_IN_H
 #include <netinet/in.h>
 #endif
 #if HAVE_STRING_H
 #include <string.h>
 #endif

 #if TIME_WITH_SYS_TIME
 # include <sys/time.h>
 # include <time.h>
 #else
 # if HAVE_SYS_TIME_H
 #  include <sys/time.h>
 # else
 #  include <time.h>
 # endif
 #endif

 #if HAVE_DMALLOC_H
 #include <dmalloc.h>
 #endif

 #include <net-snmp/types.h>
 #include <net-snmp/output_api.h>
 #include <net-snmp/config_api.h>
 #include <net-snmp/utilities.h>

 #include <net-snmp/library/snmp_api.h>
 #include <net-snmp/library/callback.h>
 #include <net-snmp/library/snmp_alarm.h>

 static struct snmp_alarm *thealarms = NULL;
 static int      start_alarms = 0;
 static unsigned int regnum = 1;

 int
 init_alarm_post_config(int majorid, int minorid, void *serverarg,
                        void *clientarg)
 {
     start_alarms = 1;
     set_an_alarm();
     return SNMPERR_SUCCESS;
 }

 void
 init_snmp_alarm(void)
 {
     start_alarms = 0;
     snmp_register_callback(SNMP_CALLBACK_LIBRARY,
                            SNMP_CALLBACK_POST_READ_CONFIG,
                            init_alarm_post_config, NULL);
 }

 void
 sa_update_entry(struct snmp_alarm *a)
 {
     if (!timerisset(&a->t_lastM)) {
         /*
          * First call of sa_update_entry() for alarm a: set t_lastM and t_nextM.
          */
         netsnmp_get_monotonic_clock(&a->t_lastM);
         NETSNMP_TIMERADD(&a->t_lastM, &a->t, &a->t_nextM);
     } else if (!timerisset(&a->t_nextM)) {
         /*
          * We've been called but not reset for the next call.
          */
         if (a->flags & SA_REPEAT) {
             if (timerisset(&a->t)) {
                 NETSNMP_TIMERADD(&a->t_lastM, &a->t, &a->t_nextM);
             } else {
                 DEBUGMSGTL(("snmp_alarm",
                             "update_entry: illegal interval specified\n"));
                 snmp_alarm_unregister(a->clientreg);
             }
         } else {
             /*
              * Single time call, remove it.
              */
             snmp_alarm_unregister(a->clientreg);
         }
     }
 }

 /**
  * This function removes the callback function from a list of registered
  * alarms, unregistering the alarm.
  *
  * @param clientreg is a unique unsigned integer representing a registered
  *	alarm which the client wants to unregister.
  *
  * @return void
  *
  * @see snmp_alarm_register
  * @see snmp_alarm_register_hr
  * @see snmp_alarm_unregister_all
  */
 void
 snmp_alarm_unregister(unsigned int clientreg)
 {
     struct snmp_alarm *sa_ptr, **prevNext = &thealarms;

     for (sa_ptr = thealarms;
          sa_ptr != NULL && sa_ptr->clientreg != clientreg;
          sa_ptr = sa_ptr->next) {
         prevNext = &(sa_ptr->next);
     }

     if (sa_ptr != NULL) {
         *prevNext = sa_ptr->next;
         DEBUGMSGTL(("snmp_alarm", "unregistered alarm %d\n",
 		    sa_ptr->clientreg));
         /*
          * Note: do not free the clientarg, it's the client's responsibility
          */
         free(sa_ptr);
     } else {
         DEBUGMSGTL(("snmp_alarm", "no alarm %d to unregister\n", clientreg));
     }
 }

 /**
  * This function unregisters all alarms currently stored.
  *
  * @return void
  *
  * @see snmp_alarm_register
  * @see snmp_alarm_register_hr
  * @see snmp_alarm_unregister
  */
 void
 snmp_alarm_unregister_all(void)
 {
   struct snmp_alarm *sa_ptr, *sa_tmp;

   for (sa_ptr = thealarms; sa_ptr != NULL; sa_ptr = sa_tmp) {
     sa_tmp = sa_ptr->next;
     free(sa_ptr);
   }
   DEBUGMSGTL(("snmp_alarm", "ALL alarms unregistered\n"));
   thealarms = NULL;
 }

 struct snmp_alarm *
 sa_find_next(void)
 {
     struct snmp_alarm *a, *lowest = NULL;

     for (a = thealarms; a != NULL; a = a->next)
         if (!(a->flags & SA_FIRED)
             && (lowest == NULL || timercmp(&a->t_nextM, &lowest->t_nextM, <)))
             lowest = a;

     return lowest;
 }

 NETSNMP_IMPORT struct snmp_alarm *sa_find_specific(unsigned int clientreg);
 struct snmp_alarm *
 sa_find_specific(unsigned int clientreg)
 {
     struct snmp_alarm *sa_ptr;
     for (sa_ptr = thealarms; sa_ptr != NULL; sa_ptr = sa_ptr->next) {
         if (sa_ptr->clientreg == clientreg) {
             return sa_ptr;
         }
     }
     return NULL;
 }

 void
 run_alarms(void)
 {
     struct snmp_alarm *a;
     unsigned int    clientreg;
     struct timeval  t_now;

     /*
      * Loop through everything we have repeatedly looking for the next thing to
      * call until all events are finally in the future again.
      */

     while ((a = sa_find_next()) != NULL) {
         netsnmp_get_monotonic_clock(&t_now);

         if (timercmp(&a->t_nextM, &t_now, >))
             return;

         clientreg = a->clientreg;
         a->flags |= SA_FIRED;
         DEBUGMSGTL(("snmp_alarm", "run alarm %d\n", clientreg));
         (*(a->thecallback)) (clientreg, a->clientarg);
         DEBUGMSGTL(("snmp_alarm", "alarm %d completed\n", clientreg));

         a = sa_find_specific(clientreg);
         if (a) {
             a->t_lastM = t_now;
             timerclear(&a->t_nextM);
             a->flags &= ~SA_FIRED;
             sa_update_entry(a);
         } else {
             DEBUGMSGTL(("snmp_alarm", "alarm %d deleted itself\n",
                         clientreg));
         }
     }
 }


 RETSIGTYPE
 alarm_handler(int a)
 {
     run_alarms();
     set_an_alarm();
 }


 /**
  * Look up the time at which the next alarm will fire.
  *
  * @param[out] alarm_tm Time at which the next alarm will fire.
  * @param[in] now Earliest time that should be written into *alarm_tm.
  *
  * @return Zero if no alarms are scheduled; non-zero 'clientreg' value
  *   identifying the first alarm that will fire if one or more alarms are
  *   scheduled.
  */
 int
 netsnmp_get_next_alarm_time(struct timeval *alarm_tm, const struct timeval *now)
 {
     struct snmp_alarm *sa_ptr;

     sa_ptr = sa_find_next();

     if (sa_ptr) {
         netsnmp_assert(alarm_tm);
         netsnmp_assert(timerisset(&sa_ptr->t_nextM));
         if (timercmp(&sa_ptr->t_nextM, now, >))
             *alarm_tm = sa_ptr->t_nextM;
         else
             *alarm_tm = *now;
         return sa_ptr->clientreg;
     } else {
         return 0;
     }
 }

 /**
  * Get the time until the next alarm will fire.
  *
  * @param[out] delta Time until the next alarm.
  *
  * @return Zero if no alarms are scheduled; non-zero 'clientreg' value
  *   identifying the first alarm that will fire if one or more alarms are
  *   scheduled.
  */
 int
 get_next_alarm_delay_time(struct timeval *delta)
 {
     struct timeval t_now, alarm_tm;
     int res;

     netsnmp_get_monotonic_clock(&t_now);
     res = netsnmp_get_next_alarm_time(&alarm_tm, &t_now);
     if (res)
         NETSNMP_TIMERSUB(&alarm_tm, &t_now, delta);
     return res;
 }


 void
 set_an_alarm(void)
 {
     struct timeval  delta;
     int             nextalarm = get_next_alarm_delay_time(&delta);

     /*
      * We don't use signals if they asked us nicely not to.  It's expected
      * they'll check the next alarm time and do their own calling of
      * run_alarms().
      */

     if (nextalarm && !netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID,
 					NETSNMP_DS_LIB_ALARM_DONT_USE_SIG)) {
 #ifndef WIN32
 # ifdef HAVE_SETITIMER
         struct itimerval it;

         it.it_value = delta;
         timerclear(&it.it_interval);

         signal(SIGALRM, alarm_handler);
         setitimer(ITIMER_REAL, &it, NULL);
         DEBUGMSGTL(("snmp_alarm", "schedule alarm %d in %ld.%03ld seconds\n",
                     nextalarm, (long) delta.tv_sec, (long)(delta.tv_usec / 1000)));
 # else  /* HAVE_SETITIMER */
 #  ifdef SIGALRM
         signal(SIGALRM, alarm_handler);
         alarm(delta.tv_sec);
         DEBUGMSGTL(("snmp_alarm",
                     "schedule alarm %d in roughly %ld seconds\n", nextalarm,
                     delta.tv_sec));
 #  endif  /* SIGALRM */
 # endif  /* HAVE_SETITIMER */
 #endif  /* WIN32 */

     } else {
         DEBUGMSGTL(("snmp_alarm", "no alarms found to schedule\n"));
     }
 }


 /**
  * This function registers function callbacks to occur at a specific time
  * in the future.
  *
  * @param when is an unsigned integer specifying when the callback function
  *             will be called in seconds.
  *
  * @param flags is an unsigned integer that specifies how frequent the callback
  *	function is called in seconds.  Should be SA_REPEAT or 0.  If
  *	flags  is  set with SA_REPEAT, then the registered callback function
  *	will be called every SA_REPEAT seconds.  If flags is 0 then the
  *	function will only be called once and then removed from the
  *	registered alarm list.
  *
  * @param thecallback is a pointer SNMPAlarmCallback which is the callback
  *	function being stored and registered.
  *
  * @param clientarg is a void pointer used by the callback function.  This
  *	pointer is assigned to snmp_alarm->clientarg and passed into the
  *	callback function for the client's specific needs.
  *
  * @return Returns a unique unsigned integer(which is also passed as the first
  *	argument of each callback), which can then be used to remove the
  *	callback from the list at a later point in the future using the
  *	snmp_alarm_unregister() function.  If memory could not be allocated
  *	for the snmp_alarm struct 0 is returned.
  *
  * @see snmp_alarm_unregister
  * @see snmp_alarm_register_hr
  * @see snmp_alarm_unregister_all
  */
 unsigned int
 snmp_alarm_register(unsigned int when, unsigned int flags,
                     SNMPAlarmCallback * thecallback, void *clientarg)
 {
     struct timeval  t;

     if (0 == when) {
         t.tv_sec = 0;
         t.tv_usec = 1;
     } else {
         t.tv_sec = when;
         t.tv_usec = 0;
     }

     return snmp_alarm_register_hr(t, flags, thecallback, clientarg);
 }


 /**
  * This function offers finer granularity as to when the callback
  * function is called by making use of t->tv_usec value forming the
  * "when" aspect of snmp_alarm_register().
  *
  * @param t is a timeval structure used to specify when the callback
  *	function(alarm) will be called.  Adds the ability to specify
  *	microseconds.  t.tv_sec and t.tv_usec are assigned
  *	to snmp_alarm->tv_sec and snmp_alarm->tv_usec respectively internally.
  *	The snmp_alarm_register function only assigns seconds(it's when
  *	argument).
  *
  * @param flags is an unsigned integer that specifies how frequent the callback
  *	function is called in seconds.  Should be SA_REPEAT or NULL.  If
  *	flags  is  set with SA_REPEAT, then the registered callback function
  *	will be called every SA_REPEAT seconds.  If flags is NULL then the
  *	function will only be called once and then removed from the
  *	registered alarm list.
  *
  * @param cb is a pointer SNMPAlarmCallback which is the callback
  *	function being stored and registered.
  *
  * @param cd is a void pointer used by the callback function.  This
  *	pointer is assigned to snmp_alarm->clientarg and passed into the
  *	callback function for the client's specific needs.
  *
  * @return Returns a unique unsigned integer(which is also passed as the first
  *	argument of each callback), which can then be used to remove the
  *	callback from the list at a later point in the future using the
  *	snmp_alarm_unregister() function.  If memory could not be allocated
  *	for the snmp_alarm struct 0 is returned.
  *
  * @see snmp_alarm_register
  * @see snmp_alarm_unregister
  * @see snmp_alarm_unregister_all
  */
 unsigned int
 snmp_alarm_register_hr(struct timeval t, unsigned int flags,
                        SNMPAlarmCallback * cb, void *cd)
 {
     struct snmp_alarm **s = NULL;

     for (s = &(thealarms); *s != NULL; s = &((*s)->next));

     *s = SNMP_MALLOC_STRUCT(snmp_alarm);
     if (*s == NULL) {
         return 0;
     }

     (*s)->t = t;
     (*s)->flags = flags;
     (*s)->clientarg = cd;
     (*s)->thecallback = cb;
     (*s)->clientreg = regnum++;
     (*s)->next = NULL;

     sa_update_entry(*s);

     DEBUGMSGTL(("snmp_alarm",
                 "registered alarm %d, t = %ld.%03ld, flags=0x%02x\n",
                 (*s)->clientreg, (long) (*s)->t.tv_sec, (long)((*s)->t.tv_usec / 1000),
                 (*s)->flags));

     if (start_alarms) {
         set_an_alarm();
     }

     return (*s)->clientreg;
 }

 /**
  * This function resets an existing alarm.
  *
  * @param clientreg is a unique unsigned integer representing a registered
  *	alarm which the client wants to unregister.
  *
  * @return 0 on success, -1 if the alarm was not found
  *
  * @see snmp_alarm_register
  * @see snmp_alarm_register_hr
  * @see snmp_alarm_unregister
  */
 int
 snmp_alarm_reset(unsigned int clientreg)
 {
     struct snmp_alarm *a;
     struct timeval  t_now;
     if ((a = sa_find_specific(clientreg)) != NULL) {
         netsnmp_get_monotonic_clock(&t_now);
         a->t_lastM.tv_sec = t_now.tv_sec;
         a->t_lastM.tv_usec = t_now.tv_usec;
         a->t_nextM.tv_sec = 0;
         a->t_nextM.tv_usec = 0;
         NETSNMP_TIMERADD(&t_now, &a->t, &a->t_nextM);
         return 0;
     }
     DEBUGMSGTL(("snmp_alarm_reset", "alarm %d not found\n",
                 clientreg));
     return -1;
 }
 /**  @} */
	/*
	* snmp_alarm.c:
	*/
	/* Portions of this file are subject to the following copyright(s). See
	* the Net-SNMP's COPYING file for more details and other copyrights
	* that may apply:
	*/
	/*
	* Portions of this file are copyrighted by:
	* Copyright © 2003 Sun Microsystems, Inc. All rights reserved.
	* Use is subject to license terms specified in the COPYING file
	* distributed with the Net-SNMP package.
	*/
	/** @defgroup snmp_alarm generic library based alarm timers for various parts of an application
	* @ingroup library
	*
	* @{
	*/
	#include <net-snmp/net-snmp-config.h>

	#if HAVE_UNISTD_H
	#include <unistd.h>
	#endif
	#include <signal.h>
	#if HAVE_STDLIB_H
	#include <stdlib.h>
	#endif
	#include <sys/types.h>
	#if HAVE_NETINET_IN_H
	#include <netinet/in.h>
	#endif
	#if HAVE_STRING_H
	#include <string.h>
	#endif

	#if TIME_WITH_SYS_TIME
	# include <sys/time.h>
	# include <time.h>
	#else
	# if HAVE_SYS_TIME_H
	# include <sys/time.h>
	# else
	# include <time.h>
	# endif
	#endif

	#if HAVE_DMALLOC_H
	#include <dmalloc.h>
	#endif

	#include <net-snmp/types.h>
	#include <net-snmp/output_api.h>
	#include <net-snmp/config_api.h>
	#include <net-snmp/utilities.h>

	#include <net-snmp/library/snmp_api.h>
	#include <net-snmp/library/callback.h>
	#include <net-snmp/library/snmp_alarm.h>

	static struct snmp_alarm *thealarms = NULL;
	static int start_alarms = 0;
	static unsigned int regnum = 1;

	int
	init_alarm_post_config(int majorid, int minorid, void *serverarg,
	void *clientarg)
	{
	start_alarms = 1;
	set_an_alarm();
	return SNMPERR_SUCCESS;
	}

	void
	init_snmp_alarm(void)
	{
	start_alarms = 0;
	snmp_register_callback(SNMP_CALLBACK_LIBRARY,
	SNMP_CALLBACK_POST_READ_CONFIG,
	init_alarm_post_config, NULL);
	}

	void
	sa_update_entry(struct snmp_alarm *a)
	{
	if (!timerisset(&a->t_lastM)) {
	/*
	* First call of sa_update_entry() for alarm a: set t_lastM and t_nextM.
	*/
	netsnmp_get_monotonic_clock(&a->t_lastM);
	NETSNMP_TIMERADD(&a->t_lastM, &a->t, &a->t_nextM);
	} else if (!timerisset(&a->t_nextM)) {
	/*
	* We've been called but not reset for the next call.
	*/
	if (a->flags & SA_REPEAT) {
	if (timerisset(&a->t)) {
	NETSNMP_TIMERADD(&a->t_lastM, &a->t, &a->t_nextM);
	} else {
	DEBUGMSGTL(("snmp_alarm",
	"update_entry: illegal interval specified\n"));
	snmp_alarm_unregister(a->clientreg);
	}
	} else {
	/*
	* Single time call, remove it.
	*/
	snmp_alarm_unregister(a->clientreg);
	}
	}
	}

	/**
	* This function removes the callback function from a list of registered
	* alarms, unregistering the alarm.
	*
	* @param clientreg is a unique unsigned integer representing a registered
	* alarm which the client wants to unregister.
	*
	* @return void
	*
	* @see snmp_alarm_register
	* @see snmp_alarm_register_hr
	* @see snmp_alarm_unregister_all
	*/
	void
	snmp_alarm_unregister(unsigned int clientreg)
	{
	struct snmp_alarm sa_ptr, *prevNext = &thealarms;

	for (sa_ptr = thealarms;
	sa_ptr != NULL && sa_ptr->clientreg != clientreg;
	sa_ptr = sa_ptr->next) {
	prevNext = &(sa_ptr->next);
	}

	if (sa_ptr != NULL) {
	*prevNext = sa_ptr->next;
	DEBUGMSGTL(("snmp_alarm", "unregistered alarm %d\n",
	sa_ptr->clientreg));
	/*
	* Note: do not free the clientarg, it's the client's responsibility
	*/
	free(sa_ptr);
	} else {
	DEBUGMSGTL(("snmp_alarm", "no alarm %d to unregister\n", clientreg));
	}
	}

	/**
	* This function unregisters all alarms currently stored.
	*
	* @return void
	*
	* @see snmp_alarm_register
	* @see snmp_alarm_register_hr
	* @see snmp_alarm_unregister
	*/
	void
	snmp_alarm_unregister_all(void)
	{
	struct snmp_alarm sa_ptr, sa_tmp;

	for (sa_ptr = thealarms; sa_ptr != NULL; sa_ptr = sa_tmp) {
	sa_tmp = sa_ptr->next;
	free(sa_ptr);
	}
	DEBUGMSGTL(("snmp_alarm", "ALL alarms unregistered\n"));
	thealarms = NULL;
	}

	struct snmp_alarm *
	sa_find_next(void)
	{
	struct snmp_alarm a, lowest = NULL;

	for (a = thealarms; a != NULL; a = a->next)
	if (!(a->flags & SA_FIRED)
	&& (lowest == NULL \|\| timercmp(&a->t_nextM, &lowest->t_nextM, <)))
	lowest = a;

	return lowest;
	}

	NETSNMP_IMPORT struct snmp_alarm *sa_find_specific(unsigned int clientreg);
	struct snmp_alarm *
	sa_find_specific(unsigned int clientreg)
	{
	struct snmp_alarm *sa_ptr;
	for (sa_ptr = thealarms; sa_ptr != NULL; sa_ptr = sa_ptr->next) {
	if (sa_ptr->clientreg == clientreg) {
	return sa_ptr;
	}
	}
	return NULL;
	}

	void
	run_alarms(void)
	{
	struct snmp_alarm *a;
	unsigned int clientreg;
	struct timeval t_now;

	/*
	* Loop through everything we have repeatedly looking for the next thing to
	* call until all events are finally in the future again.
	*/

	while ((a = sa_find_next()) != NULL) {
	netsnmp_get_monotonic_clock(&t_now);

	if (timercmp(&a->t_nextM, &t_now, >))
	return;

	clientreg = a->clientreg;
	a->flags \|= SA_FIRED;
	DEBUGMSGTL(("snmp_alarm", "run alarm %d\n", clientreg));
	(*(a->thecallback)) (clientreg, a->clientarg);
	DEBUGMSGTL(("snmp_alarm", "alarm %d completed\n", clientreg));

	a = sa_find_specific(clientreg);
	if (a) {
	a->t_lastM = t_now;
	timerclear(&a->t_nextM);
	a->flags &= ~SA_FIRED;
	sa_update_entry(a);
	} else {
	DEBUGMSGTL(("snmp_alarm", "alarm %d deleted itself\n",
	clientreg));
	}
	}
	}



	RETSIGTYPE
	alarm_handler(int a)
	{
	run_alarms();
	set_an_alarm();
	}



	/**
	* Look up the time at which the next alarm will fire.
	*
	* @param[out] alarm_tm Time at which the next alarm will fire.
	* @param[in] now Earliest time that should be written into *alarm_tm.
	*
	* @return Zero if no alarms are scheduled; non-zero 'clientreg' value
	* identifying the first alarm that will fire if one or more alarms are
	* scheduled.
	*/
	int
	netsnmp_get_next_alarm_time(struct timeval alarm_tm, const struct timeval now)
	{
	struct snmp_alarm *sa_ptr;

	sa_ptr = sa_find_next();

	if (sa_ptr) {
	netsnmp_assert(alarm_tm);
	netsnmp_assert(timerisset(&sa_ptr->t_nextM));
	if (timercmp(&sa_ptr->t_nextM, now, >))
	*alarm_tm = sa_ptr->t_nextM;
	else
	alarm_tm = now;
	return sa_ptr->clientreg;
	} else {
	return 0;
	}
	}

	/**
	* Get the time until the next alarm will fire.
	*
	* @param[out] delta Time until the next alarm.
	*
	* @return Zero if no alarms are scheduled; non-zero 'clientreg' value
	* identifying the first alarm that will fire if one or more alarms are
	* scheduled.
	*/
	int
	get_next_alarm_delay_time(struct timeval *delta)
	{
	struct timeval t_now, alarm_tm;
	int res;

	netsnmp_get_monotonic_clock(&t_now);
	res = netsnmp_get_next_alarm_time(&alarm_tm, &t_now);
	if (res)
	NETSNMP_TIMERSUB(&alarm_tm, &t_now, delta);
	return res;
	}


	void
	set_an_alarm(void)
	{
	struct timeval delta;
	int nextalarm = get_next_alarm_delay_time(&delta);

	/*
	* We don't use signals if they asked us nicely not to. It's expected
	* they'll check the next alarm time and do their own calling of
	* run_alarms().
	*/

	if (nextalarm && !netsnmp_ds_get_boolean(NETSNMP_DS_LIBRARY_ID,
	NETSNMP_DS_LIB_ALARM_DONT_USE_SIG)) {
	#ifndef WIN32
	# ifdef HAVE_SETITIMER
	struct itimerval it;

	it.it_value = delta;
	timerclear(&it.it_interval);

	signal(SIGALRM, alarm_handler);
	setitimer(ITIMER_REAL, &it, NULL);
	DEBUGMSGTL(("snmp_alarm", "schedule alarm %d in %ld.%03ld seconds\n",
	nextalarm, (long) delta.tv_sec, (long)(delta.tv_usec / 1000)));
	# else /* HAVE_SETITIMER */
	# ifdef SIGALRM
	signal(SIGALRM, alarm_handler);
	alarm(delta.tv_sec);
	DEBUGMSGTL(("snmp_alarm",
	"schedule alarm %d in roughly %ld seconds\n", nextalarm,
	delta.tv_sec));
	# endif /* SIGALRM */
	# endif /* HAVE_SETITIMER */
	#endif /* WIN32 */

	} else {
	DEBUGMSGTL(("snmp_alarm", "no alarms found to schedule\n"));
	}
	}


	/**
	* This function registers function callbacks to occur at a specific time
	* in the future.
	*
	* @param when is an unsigned integer specifying when the callback function
	* will be called in seconds.
	*
	* @param flags is an unsigned integer that specifies how frequent the callback
	* function is called in seconds. Should be SA_REPEAT or 0. If
	* flags is set with SA_REPEAT, then the registered callback function
	* will be called every SA_REPEAT seconds. If flags is 0 then the
	* function will only be called once and then removed from the
	* registered alarm list.
	*
	* @param thecallback is a pointer SNMPAlarmCallback which is the callback
	* function being stored and registered.
	*
	* @param clientarg is a void pointer used by the callback function. This
	* pointer is assigned to snmp_alarm->clientarg and passed into the
	* callback function for the client's specific needs.
	*
	* @return Returns a unique unsigned integer(which is also passed as the first
	* argument of each callback), which can then be used to remove the
	* callback from the list at a later point in the future using the
	* snmp_alarm_unregister() function. If memory could not be allocated
	* for the snmp_alarm struct 0 is returned.
	*
	* @see snmp_alarm_unregister
	* @see snmp_alarm_register_hr
	* @see snmp_alarm_unregister_all
	*/
	unsigned int
	snmp_alarm_register(unsigned int when, unsigned int flags,
	SNMPAlarmCallback * thecallback, void *clientarg)
	{
	struct timeval t;

	if (0 == when) {
	t.tv_sec = 0;
	t.tv_usec = 1;
	} else {
	t.tv_sec = when;
	t.tv_usec = 0;
	}

	return snmp_alarm_register_hr(t, flags, thecallback, clientarg);
	}


	/**
	* This function offers finer granularity as to when the callback
	* function is called by making use of t->tv_usec value forming the
	* "when" aspect of snmp_alarm_register().
	*
	* @param t is a timeval structure used to specify when the callback
	* function(alarm) will be called. Adds the ability to specify
	* microseconds. t.tv_sec and t.tv_usec are assigned
	* to snmp_alarm->tv_sec and snmp_alarm->tv_usec respectively internally.
	* The snmp_alarm_register function only assigns seconds(it's when
	* argument).
	*
	* @param flags is an unsigned integer that specifies how frequent the callback
	* function is called in seconds. Should be SA_REPEAT or NULL. If
	* flags is set with SA_REPEAT, then the registered callback function
	* will be called every SA_REPEAT seconds. If flags is NULL then the
	* function will only be called once and then removed from the
	* registered alarm list.
	*
	* @param cb is a pointer SNMPAlarmCallback which is the callback
	* function being stored and registered.
	*
	* @param cd is a void pointer used by the callback function. This
	* pointer is assigned to snmp_alarm->clientarg and passed into the
	* callback function for the client's specific needs.
	*
	* @return Returns a unique unsigned integer(which is also passed as the first
	* argument of each callback), which can then be used to remove the
	* callback from the list at a later point in the future using the
	* snmp_alarm_unregister() function. If memory could not be allocated
	* for the snmp_alarm struct 0 is returned.
	*
	* @see snmp_alarm_register
	* @see snmp_alarm_unregister
	* @see snmp_alarm_unregister_all
	*/
	unsigned int
	snmp_alarm_register_hr(struct timeval t, unsigned int flags,
	SNMPAlarmCallback * cb, void *cd)
	{
	struct snmp_alarm **s = NULL;

	for (s = &(thealarms); s != NULL; s = &((s)->next));

	*s = SNMP_MALLOC_STRUCT(snmp_alarm);
	if (*s == NULL) {
	return 0;
	}

	(*s)->t = t;
	(*s)->flags = flags;
	(*s)->clientarg = cd;
	(*s)->thecallback = cb;
	(*s)->clientreg = regnum++;
	(*s)->next = NULL;

	sa_update_entry(*s);

	DEBUGMSGTL(("snmp_alarm",
	"registered alarm %d, t = %ld.%03ld, flags=0x%02x\n",
	(s)->clientreg, (long) (s)->t.tv_sec, (long)((*s)->t.tv_usec / 1000),
	(*s)->flags));

	if (start_alarms) {
	set_an_alarm();
	}

	return (*s)->clientreg;
	}

	/**
	* This function resets an existing alarm.
	*
	* @param clientreg is a unique unsigned integer representing a registered
	* alarm which the client wants to unregister.
	*
	* @return 0 on success, -1 if the alarm was not found
	*
	* @see snmp_alarm_register
	* @see snmp_alarm_register_hr
	* @see snmp_alarm_unregister
	*/
	int
	snmp_alarm_reset(unsigned int clientreg)
	{
	struct snmp_alarm *a;
	struct timeval t_now;
	if ((a = sa_find_specific(clientreg)) != NULL) {
	netsnmp_get_monotonic_clock(&t_now);
	a->t_lastM.tv_sec = t_now.tv_sec;
	a->t_lastM.tv_usec = t_now.tv_usec;
	a->t_nextM.tv_sec = 0;
	a->t_nextM.tv_usec = 0;
	NETSNMP_TIMERADD(&t_now, &a->t, &a->t_nextM);
	return 0;
	}
	DEBUGMSGTL(("snmp_alarm_reset", "alarm %d not found\n",
	clientreg));
	return -1;
	}
	/** @} */