/*

 * callback.c: A generic callback mechanism 

 */

/* 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 callback A generic callback mechanism 

 *  @ingroup library

 * 

 *  @{

 */

#include <net-snmp/net-snmp-config.h>

#include <net-snmp/net-snmp-features.h>

#include <sys/types.h>

#include <stdio.h>

#ifdef HAVE_STDLIB_H

#include <stdlib.h>

#endif

#ifdef HAVE_NETINET_IN_H

#include <netinet/in.h>

#endif

#ifdef HAVE_STRING_H

#include <string.h>

#else

#include <strings.h>

#endif

#ifdef HAVE_UNISTD_H

#include <unistd.h>

#endif

#ifdef HAVE_SYS_SOCKET_H

#include <sys/socket.h>

#endif

#if !defined(mingw32) && defined(HAVE_SYS_TIME_H)

#include <sys/time.h>

#endif

#include <net-snmp/types.h>

#include <net-snmp/output_api.h>

#include <net-snmp/utilities.h>

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

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

netsnmp_feature_child_of(callbacks_all, libnetsnmp);

netsnmp_feature_child_of(callback_count, callbacks_all);

netsnmp_feature_child_of(callback_list, callbacks_all);

/*

 * the inline callback methods use major/minor to index into arrays.

 * all users in this function do range checking before calling these

 * functions, so it is redundant for them to check again. But if you

 * want to be paranoid, define this var, and additional range checks

 * will be performed.

 * #define NETSNMP_PARANOID_LEVEL_HIGH 1 

 */

static int _callback_need_init = 1;

static struct snmp_gen_callback

               *thecallbacks[MAX_CALLBACK_IDS][MAX_CALLBACK_SUBIDS];

#define CALLBACK_NAME_LOGGING 1

#ifdef CALLBACK_NAME_LOGGING

static const char *types[MAX_CALLBACK_IDS] = { "LIB", "APP" };

static const char *lib[MAX_CALLBACK_SUBIDS] = {

    "POST_READ_CONFIG", /* 0 */

    "STORE_DATA", /* 1 */

    "SHUTDOWN", /* 2 */

    "POST_PREMIB_READ_CONFIG", /* 3 */

    "LOGGING", /* 4 */

    "SESSION_INIT", /* 5 */

    NULL, /* 6 */

    NULL, /* 7 */

    NULL, /* 8 */

    NULL, /* 9 */

    NULL, /* 10 */

    NULL, /* 11 */

    NULL, /* 12 */

    NULL, /* 13 */

    NULL, /* 14 */

    NULL /* 15 */

};

#endif

/*

 * extremely simplistic locking, just to find problems were the

 * callback list is modified while being traversed. Not intended

 * to do any real protection, or in any way imply that this code

 * has been evaluated for use in a multi-threaded environment.

 * In 5.2, it was a single lock. For 5.3, it has been updated to

 * a lock per callback, since a particular callback may trigger

 * registration/unregistration of other callbacks (eg AgentX

 * subagents do this).

 */

#define LOCK_PER_CALLBACK_SUBID 1

#ifdef LOCK_PER_CALLBACK_SUBID

static int _locks[MAX_CALLBACK_IDS][MAX_CALLBACK_SUBIDS];

#define CALLBACK_LOCK(maj,min) ++_locks[maj][min]

#define CALLBACK_UNLOCK(maj,min) --_locks[maj][min]

#define CALLBACK_LOCK_COUNT(maj,min) _locks[maj][min]

#else

static int _lock;

#define CALLBACK_LOCK(maj,min) ++_lock

#define CALLBACK_UNLOCK(maj,min) --_lock

#define CALLBACK_LOCK_COUNT(maj,min) _lock

#endif

NETSNMP_STATIC_INLINE int

_callback_lock(int major, int minor, const char* warn, int do_assert)

{

    int lock_holded=0;

    NETSNMP_SELECT_TIMEVAL lock_time;

#ifdef NETSNMP_PARANOID_LEVEL_HIGH

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {

        netsnmp_assert("bad callback id");

        return 1;

    }

#endif

#ifdef CALLBACK_NAME_LOGGING

    DEBUGMSGTL(("9:callback:lock", "locked (%s,%s)\n",

                types[major], (SNMP_CALLBACK_LIBRARY == major) ?

                SNMP_STRORNULL(lib[minor]) : "null"));

#endif

    while (CALLBACK_LOCK_COUNT(major,minor) >= 1 && ++lock_holded < 100) {

  lock_time.tv_sec = 0;

  lock_time.tv_usec = 1000;

  select(0, NULL, NULL, NULL, &lock_time);

    }

    if(lock_holded >= 100) {

        if (NULL != warn)

            snmp_log(LOG_WARNING,

                     "lock in _callback_lock sleeps more than 100 milliseconds in %s\n", warn);

        if (do_assert)

            netsnmp_assert(lock_holded < 100);

        return 1;

    }

    CALLBACK_LOCK(major,minor);

    return 0;

}

NETSNMP_STATIC_INLINE void

_callback_unlock(int major, int minor)

{

#ifdef NETSNMP_PARANOID_LEVEL_HIGH

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {

        netsnmp_assert("bad callback id");

        return;

    }

#endif

    CALLBACK_UNLOCK(major,minor);

    if (CALLBACK_LOCK_COUNT(major,minor) == 0) {

        struct snmp_gen_callback *scp, **prevNext;

        scp = thecallbacks[major][minor];

        prevNext = &(thecallbacks[major][minor]);

        while (scp != NULL) {

            if (scp->sc_callback == NULL) {

                *prevNext = scp->next;

                SNMP_FREE(scp);

                scp = *prevNext;

            } else {

                prevNext = &(scp->next);

                scp = scp->next;

            }

        }

    }

#ifdef CALLBACK_NAME_LOGGING

    DEBUGMSGTL(("9:callback:lock", "unlocked (%s,%s)\n",

                types[major], (SNMP_CALLBACK_LIBRARY == major) ?

                SNMP_STRORNULL(lib[minor]) : "null"));

#endif

}

/*

 * the chicken. or the egg.  You pick. 

 */

void

init_callbacks(void)

{

    /*

     * (poses a problem if you put init_callbacks() inside of

     * init_snmp() and then want the app to register a callback before

     * init_snmp() is called in the first place.  -- Wes 

     */

    if (0 == _callback_need_init)

        return;

    _callback_need_init = 0;

    memset(thecallbacks, 0, sizeof(thecallbacks)); 

#ifdef LOCK_PER_CALLBACK_SUBID

    memset(_locks, 0, sizeof(_locks));

#else

    _lock = 0;

#endif

    DEBUGMSGTL(("callback", "initialized\n"));

}

/**

 * This function registers a generic callback function.  The major and

 * minor values are used to set the new_callback function into a global 

 * static multi-dimensional array of type struct snmp_gen_callback.  

 * The function makes sure to append this callback function at the end

 * of the link list, snmp_gen_callback->next.

 *

 * @param major is the SNMP callback major type used

 *    - SNMP_CALLBACK_LIBRARY

 *              - SNMP_CALLBACK_APPLICATION

 *

 * @param minor is the SNMP callback minor type used

 *    - SNMP_CALLBACK_POST_READ_CONFIG

 *    - SNMP_CALLBACK_STORE_DATA          

 *    - SNMP_CALLBACK_SHUTDOWN            

 *    - SNMP_CALLBACK_POST_PREMIB_READ_CONFIG 

 *    - SNMP_CALLBACK_LOGGING     

 *    - SNMP_CALLBACK_SESSION_INIT         

 *

 * @param new_callback is the callback function that is registered.

 *

 * @param arg when not NULL is a void pointer used whenever new_callback 

 *  function is exercised. Ownership is transferred to the twodimensional

 *      thecallbacks[][] array. The function clear_callback() will deallocate

 *      the memory pointed at by calling free().

 *

 * @return 

 *  Returns SNMPERR_GENERR if major is >= MAX_CALLBACK_IDS or minor is >=

 *  MAX_CALLBACK_SUBIDS or a snmp_gen_callback pointer could not be 

 *  allocated, otherwise SNMPERR_SUCCESS is returned.

 *  - \#define MAX_CALLBACK_IDS    2

 *  - \#define MAX_CALLBACK_SUBIDS 16

 *

 * @see snmp_call_callbacks

 * @see snmp_unregister_callback

 */

int

snmp_register_callback(int major, int minor, SNMPCallback * new_callback,

                       void *arg)

{

    return netsnmp_register_callback( major, minor, new_callback, arg,

                                      NETSNMP_CALLBACK_DEFAULT_PRIORITY);

}

/**

 * Register a callback function.

 *

 * @param major        Major callback event type.

 * @param minor        Minor callback event type.

 * @param new_callback Callback function being registered.

 * @param arg          Argument that will be passed to the callback function.

 * @param priority     Handler invocation priority. When multiple handlers have

 *   been registered for the same (major, minor) callback event type, handlers

 *   with the numerically lowest priority will be invoked first. Handlers with

 *   identical priority are invoked in the order they have been registered.

 *

 * @see snmp_register_callback

 */

int

netsnmp_register_callback(int major, int minor, SNMPCallback * new_callback,

                          void *arg, int priority)

{

    struct snmp_gen_callback *newscp = NULL, *scp = NULL;

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {

        return SNMPERR_GENERR;

    }

    if (_callback_need_init)

        init_callbacks();

    _callback_lock(major,minor, "netsnmp_register_callback", 1);

    if ((newscp = SNMP_MALLOC_STRUCT(snmp_gen_callback)) == NULL) {

        _callback_unlock(major,minor);

        return SNMPERR_GENERR;

    } else {

        struct snmp_gen_callback **prevNext = &(thecallbacks[major][minor]);

        newscp->priority = priority;

        newscp->sc_client_arg = arg;

        newscp->sc_callback = new_callback;

        newscp->next = NULL;

        for (scp = thecallbacks[major][minor]; scp != NULL;

             scp = scp->next) {

            if (newscp->priority < scp->priority) {

                newscp->next = scp;

                break;

            }

            prevNext = &(scp->next);

        }

        *prevNext = newscp;

        DEBUGMSGTL(("callback", "registered (%d,%d) at %p with priority %d\n",

                    major, minor, newscp, priority));

        _callback_unlock(major,minor);

        return SNMPERR_SUCCESS;

    }

}

/**

 * This function calls the callback function for each registered callback of

 * type major and minor.

 *

 * @param major is the SNMP callback major type used

 *

 * @param minor is the SNMP callback minor type used

 *

 * @param caller_arg is a void pointer which is sent in as the callback's 

 *  serverarg parameter, if needed.

 *

 * @return Returns SNMPERR_GENERR if major is >= MAX_CALLBACK_IDS or

 * minor is >= MAX_CALLBACK_SUBIDS, otherwise SNMPERR_SUCCESS is returned.

 *

 * @see snmp_register_callback

 * @see snmp_unregister_callback

 */

int

snmp_call_callbacks(int major, int minor, void *caller_arg)

{

    struct snmp_gen_callback *scp;

    unsigned int    count = 0;

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {

        return SNMPERR_GENERR;

    }

    if (_callback_need_init)

        init_callbacks();

#ifdef LOCK_PER_CALLBACK_SUBID

    _callback_lock(major,minor,"snmp_call_callbacks", 1);

#else

    /*

     * Notes:

     * - this gets hit the first time a trap is sent after a new trap

     *   destination has been added (session init cb during send trap cb)

     */

    _callback_lock(major,minor, NULL, 0);

#endif

    DEBUGMSGTL(("callback", "START calling callbacks for maj=%d min=%d\n",

                major, minor));

    /*

     * for each registered callback of type major and minor 

     */

    for (scp = thecallbacks[major][minor]; scp != NULL; scp = scp->next) {

        /*

         * skip unregistered callbacks

         */

        if(NULL == scp->sc_callback)

            continue;

        DEBUGMSGTL(("callback", "calling a callback for maj=%d min=%d\n",

                    major, minor));

        /*

         * call them 

         */

        (*(scp->sc_callback)) (major, minor, caller_arg,

                               scp->sc_client_arg);

        count++;

    }

    DEBUGMSGTL(("callback",

                "END calling callbacks for maj=%d min=%d (%d called)\n",

                major, minor, count));

    _callback_unlock(major,minor);

    return SNMPERR_SUCCESS;

}

#ifndef NETSNMP_FEATURE_REMOVE_CALLBACK_COUNT

int

snmp_count_callbacks(int major, int minor)

{

    int             count = 0;

    struct snmp_gen_callback *scp;

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {

        return SNMPERR_GENERR;

    }

    if (_callback_need_init)

        init_callbacks();

    for (scp = thecallbacks[major][minor]; scp != NULL; scp = scp->next) {

        count++;

    }

    return count;

}

#endif /* NETSNMP_FEATURE_REMOVE_CALLBACK_COUNT */

int

snmp_callback_available(int major, int minor)

{

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS) {

        return SNMPERR_GENERR;

    }

    if (_callback_need_init)

        init_callbacks();

    if (thecallbacks[major][minor] != NULL) {

        return SNMPERR_SUCCESS;

    }

    return SNMPERR_GENERR;

}

/**

 * This function unregisters a specified callback function given a major

 * and minor type.

 *

 * Note: no bound checking on major and minor.

 *

 * @param major is the SNMP callback major type used

 *

 * @param minor is the SNMP callback minor type used

 *

 * @param target is the callback function that will be unregistered.

 *

 * @param arg is a void pointer used for comparison against the registered 

 *  callback's sc_client_arg variable.

 *

 * @param matchargs is an integer used to bypass the comparison of arg and the

 *  callback's sc_client_arg variable only when matchargs is set to 0.

 *

 *

 * @return

 *        Returns the number of callbacks that were unregistered.

 *

 * @see snmp_register_callback

 * @see snmp_call_callbacks

 */

int

snmp_unregister_callback(int major, int minor, SNMPCallback * target,

                         void *arg, int matchargs)

{

    struct snmp_gen_callback *scp;

    struct snmp_gen_callback **prevNext;

    int             count = 0;

    int             lock_failed;

    if (major >= MAX_CALLBACK_IDS || minor >= MAX_CALLBACK_SUBIDS)

        return SNMPERR_GENERR;

    scp = thecallbacks[major][minor];

    prevNext = &(thecallbacks[major][minor]);

    if (_callback_need_init)

        init_callbacks();

#ifdef LOCK_PER_CALLBACK_SUBID

    lock_failed = _callback_lock(major,minor,"snmp_unregister_callback", 1);

#else

    /*

     * Notes;

     * - this gets hit at shutdown, during cleanup. No easy fix.

     */

    lock_failed = _callback_lock(major,minor,"snmp_unregister_callback", 0);

#endif

    while (scp != NULL) {

        if ((scp->sc_callback == target) &&

            (!matchargs || (scp->sc_client_arg == arg))) {

            DEBUGMSGTL(("callback", "unregistering (%d,%d) at %p\n", major,

                        minor, scp));

            if(!lock_failed && 1 == CALLBACK_LOCK_COUNT(major,minor)) {

                *prevNext = scp->next;

                SNMP_FREE(scp);

                scp = *prevNext;

            }

            else {

                scp->sc_callback = NULL;

                /** set cleanup flag? */

            }

            count++;

        } else {

            prevNext = &(scp->next);

            scp = scp->next;

        }

    }

    if (!lock_failed)

        _callback_unlock(major,minor);

    return count;

}

/**

 * find and clear client args that match ptr

 *

 * @param ptr  pointer to search for

 * @param i    callback id to start at

 * @param j    callback subid to start at

 */

int

netsnmp_callback_clear_client_arg(void *ptr, int i, int j)

{

    struct snmp_gen_callback *scp = NULL;

    int rc = 0;

    /*

     * don't init i and j before loop, since the caller specified

     * the starting point explicitly. But *after* the i loop has

     * finished executing once, init j to 0 for the next pass

     * through the subids.

     */

    for (; i < MAX_CALLBACK_IDS; i++,j=0) {

        for (; j < MAX_CALLBACK_SUBIDS; j++) {

            scp = thecallbacks[i][j]; 

            while (scp != NULL) {

                if ((NULL != scp->sc_callback) &&

                    (scp->sc_client_arg != NULL) &&

                    (scp->sc_client_arg == ptr)) {

                    DEBUGMSGTL(("9:callback", "  clearing %p at [%d,%d]\n", ptr, i, j));

                    scp->sc_client_arg = NULL;

                    ++rc;

                }

                scp = scp->next;

            }

        }

    }

    if (0 != rc) {

        DEBUGMSGTL(("callback", "removed %d client args\n", rc));

    }

    return rc;

}

void

clear_callback(void)

{

    unsigned int i = 0, j = 0;

    struct snmp_gen_callback *scp = NULL;

    if (_callback_need_init)

        init_callbacks();

    DEBUGMSGTL(("callback", "clear callback\n"));

    for (i = 0; i < MAX_CALLBACK_IDS; i++) {

        for (j = 0; j < MAX_CALLBACK_SUBIDS; j++) {

            _callback_lock(i,j, "clear_callback", 1);

            scp = thecallbacks[i][j];

            while (scp != NULL) {

                thecallbacks[i][j] = scp->next;

                /*

                 * if there is a client arg, check for duplicates

                 * and then free it.

                 */

                if ((NULL != scp->sc_callback) &&

                    (scp->sc_client_arg != NULL)) {

                    void *tmp_arg;

                    /*

                     * save the client arg, then set it to null so that it

                     * won't look like a duplicate, then check for duplicates

                     * starting at the current i,j (earlier dups should have

                     * already been found) and free the pointer.

                     */

                    tmp_arg = scp->sc_client_arg;

                    scp->sc_client_arg = NULL;

                    DEBUGMSGTL(("9:callback", "  freeing %p at [%d,%d]\n", tmp_arg, i, j));

                    (void)netsnmp_callback_clear_client_arg(tmp_arg, i, j);

                    free(tmp_arg);

                }

                SNMP_FREE(scp);

                scp = thecallbacks[i][j];

            }

            _callback_unlock(i,j);

        }

    }

}

#ifndef NETSNMP_FEATURE_REMOVE_CALLBACK_LIST

struct snmp_gen_callback *

snmp_callback_list(int major, int minor)

{

    if (_callback_need_init)

        init_callbacks();

    return (thecallbacks[major][minor]);

}

#endif /* NETSNMP_FEATURE_REMOVE_CALLBACK_LIST */

/**  @} */