/*
 * CDDL HEADER START
 *
 * The contents of this file are subject to the terms of the
 * Common Development and Distribution License (the "License").
 * You may not use this file except in compliance with the License.
 *
 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
 * or http://www.opensolaris.org/os/licensing.
 * See the License for the specific language governing permissions
 * and limitations under the License.
 *
 * When distributing Covered Code, include this CDDL HEADER in each
 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
 * If applicable, add the following below this CDDL HEADER, with the
 * fields enclosed by brackets "[]" replaced with your own identifying
 * information: Portions Copyright [yyyy] [name of copyright owner]
 *
 * CDDL HEADER END
 */

/*
 * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
 * Use is subject to license terms.
 */

#include <assert.h>
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <string.h>
#include <syslog.h>
#include <sys/msg.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>

#include "libnwam_impl.h"
#include <libnwam_priv.h>
#include <libnwam.h>

/*
 * Implementation of event notification mechanism used by the GUI and
 * nwamadm.  Clients register for events via nwam_events_init() and
 * unregister via nwam_events_fini().  nwamd sends events via nwam_event_send()
 * and applications block waiting for a new event to be delivered in
 * nwam_event_wait().  Events are implemented as System V message queues,
 * one per event client.  The event mechanism has to be resilient to
 * nwamd restarts so that clients do not lose the event connection.
 */

#define NWAM_EVENT_MSG_DIR              "/etc/svc/volatile/nwam/"
#define NWAM_EVENT_MSG_FILE             "nwam_event_msgs"
#define NWAM_EVENT_MSG_FILE_PREFIX      NWAM_EVENT_MSG_DIR NWAM_EVENT_MSG_FILE
#define NWAM_EVENT_MAX_SIZE             (sizeof (struct nwam_event) + \
        (NWAMD_MAX_NUM_WLANS * sizeof (nwam_wlan_t)))
#define NWAM_EVENT_WAIT_TIME            10
#define NWAM_EVENT_MAX_NUM_PENDING      25

/*
 * This is protecting simultaneous access to the msqid and its configuration.
 */
static pthread_mutex_t event_mutex = PTHREAD_MUTEX_INITIALIZER;
static int event_msqid = -1;

static nwam_error_t
nwam_event_alloc(nwam_event_t *eventp)
{
        assert(eventp != NULL);

        *eventp = calloc(1, NWAM_EVENT_MAX_SIZE);
        if (*eventp == NULL)
                return (NWAM_NO_MEMORY);
        return (NWAM_SUCCESS);
}

void
nwam_event_free(nwam_event_t event)
{
        if (event != NULL)
                free(event);
}

/*
 * Get next event in queue.
 */
nwam_error_t
nwam_event_wait(nwam_event_t *eventp)
{
        nwam_error_t err;
        nwam_event_t event;

        assert(eventp != NULL);

        if ((err = nwam_event_alloc(&event)) != NWAM_SUCCESS)
                return (err);
        while (msgrcv(event_msqid, (struct msgbuf *)event, NWAM_EVENT_MAX_SIZE,
            0, 0) == -1) {
                switch (errno) {
                        case EAGAIN:
                        case EBUSY:
                                /*
                                 * We see this errno eventhough it isn't
                                 * documented.  Try again.  If this causes
                                 * a busy loop then grab a trace otherwise
                                 * it's a brace 'til we can figure out why it
                                 * happens.
                                 */
                                continue;

                        default:
                                nwam_event_free(event);
                                return (nwam_errno_to_nwam_error(errno));
                }
        }

        /* Resize event down from maximum size */
        if ((*eventp = realloc(event, event->nwe_size)) == NULL)
                return (NWAM_NO_MEMORY);

        return (NWAM_SUCCESS);
}

/*
 * Register for receipt of events from nwamd.  Event delivery is
 * done via a System V message queue.
 */
nwam_error_t
nwam_events_init(void)
{
        char eventmsgfile[MAXPATHLEN];
        nwam_error_t err;
        nwam_error_t rc = NWAM_SUCCESS;
        key_t key;

        (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s.%d",
            NWAM_EVENT_MSG_FILE_PREFIX, getpid());

        (void) pthread_mutex_lock(&event_mutex);

        if (event_msqid != -1) {
                rc = NWAM_ENTITY_IN_USE;
                goto exit;
        }

        if ((err = nwam_request_register_unregister
            (NWAM_REQUEST_TYPE_EVENT_REGISTER, eventmsgfile)) != NWAM_SUCCESS) {
                rc = err;
                goto exit;
        }

        if ((key = ftok(eventmsgfile, 0)) == -1) {
                rc = nwam_errno_to_nwam_error(errno);
                goto exit;
        }

        /* Get system-wide message queue ID */
        if ((event_msqid = msgget(key, 0444)) == -1) {
                rc = nwam_errno_to_nwam_error(errno);
                goto exit;
        }

exit:
        (void) pthread_mutex_unlock(&event_mutex);

        return (rc);
}

/*
 * Un-register for receipt of events from nwamd.  Make a request to nwamd
 * to destroy the message queue.
 */
void
nwam_events_fini(void)
{
        char eventmsgfile[MAXPATHLEN];

        (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s.%d",
            NWAM_EVENT_MSG_FILE_PREFIX, getpid());

        (void) pthread_mutex_lock(&event_mutex);

        (void) nwam_request_register_unregister
            (NWAM_REQUEST_TYPE_EVENT_UNREGISTER, eventmsgfile);

        event_msqid = -1;

        (void) pthread_mutex_unlock(&event_mutex);
}

/*
 * Create an event queue.  Called by nwamd to create System V message queues
 * for clients to listen for events.
 */
nwam_error_t
nwam_event_queue_init(const char *eventmsgfile)
{
        int fd;
        key_t key;

        if ((fd = open(eventmsgfile, O_RDWR | O_CREAT | O_TRUNC, 0644)) == -1)
                return (nwam_errno_to_nwam_error(errno));
        (void) close(fd);

        if ((key = ftok(eventmsgfile, 0)) == -1)
                return (nwam_errno_to_nwam_error(errno));

        if (msgget(key, 0644 | IPC_CREAT) == -1)
                return (nwam_errno_to_nwam_error(errno));

        return (NWAM_SUCCESS);
}

/*
 * Send event to registered listeners via the set of registered System V
 * message queues.
 */
nwam_error_t
nwam_event_send(nwam_event_t event)
{
        DIR *dirp;
        struct dirent *dp;
        struct msqid_ds buf;
        key_t key;
        int msqid;
        char eventmsgfile[MAXPATHLEN];
        nwam_error_t err = NWAM_SUCCESS;

        if ((dirp = opendir(NWAM_EVENT_MSG_DIR)) == NULL) {
                return (nwam_errno_to_nwam_error(errno));
        }

        /*
         * For each file matching our event message queue file prefix,
         * check the queue is still being read, and if so send the message.
         */
        while ((dp = readdir(dirp)) != NULL) {
                if (strncmp(dp->d_name, NWAM_EVENT_MSG_FILE,
                    strlen(NWAM_EVENT_MSG_FILE)) != 0)
                        continue;

                (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s/%s",
                    NWAM_EVENT_MSG_DIR, dp->d_name);

                if ((key = ftok(eventmsgfile, 0)) == -1) {
                        int errno_save = errno;
                        syslog(LOG_INFO, "nwam_event_send: ftok: %s",
                            strerror(errno_save));
                        err = nwam_errno_to_nwam_error(errno_save);
                        continue;
                }

                if ((msqid = msgget(key, 0644)) == -1) {
                        int errno_save = errno;
                        syslog(LOG_INFO, "nwam_event_send: msgget: %s",
                            strerror(errno_save));
                        err = nwam_errno_to_nwam_error(errno_save);
                        continue;
                }

                /* Retrieve stats to analyse queue activity */
                if (msgctl(msqid, IPC_STAT, &buf) == -1) {
                        int errno_save = errno;
                        syslog(LOG_INFO, "nwam_event_send: msgctl: %s",
                            strerror(errno_save));
                        err = nwam_errno_to_nwam_error(errno_save);
                        continue;
                }
                /*
                 * If buf.msg_qnum > NWAM_EVENT_MAX_NUM_PENDING
                 * _and_ msg_stime is more than 10s after msg_rtime -
                 * indicating message(s) have been hanging around unclaimed -
                 * we destroy the queue as the client has most likely gone
                 * away. This can happen if a registered client hits Ctrl^C.
                 */
                if (buf.msg_qnum > NWAM_EVENT_MAX_NUM_PENDING &&
                    ((buf.msg_stime + NWAM_EVENT_WAIT_TIME) > buf.msg_rtime)) {
                        nwam_event_queue_fini(eventmsgfile);
                        continue;
                }

                /*
                 * This shouldn't ever block.  If it does then log an error and
                 * clean up the queue.
                 */
                if (msgsnd(msqid, (struct msgbuf *)event, event->nwe_size,
                    IPC_NOWAIT) == -1) {
                        int errno_save = errno;
                        syslog(LOG_ERR, "nwam_event_send: msgsnd: %s, "
                            "destroying message queue %s", strerror(errno_save),
                            eventmsgfile);
                        nwam_event_queue_fini(eventmsgfile);
                        err = nwam_errno_to_nwam_error(errno_save);
                        continue;
                }

        }
        (void) closedir(dirp);

        return (err);
}

/*
 * Destroy an event queue.  Called by nwamd to destroy the associated message
 * queue.
 */
void
nwam_event_queue_fini(const char *eventmsgfile)
{
        key_t key;
        int msqid;

        if ((key = ftok(eventmsgfile, 0)) != -1 &&
            (msqid = msgget(key, 0644)) != -1 &&
            msgctl(msqid, IPC_RMID, NULL) != -1)
                (void) unlink(eventmsgfile);
}

/*
 * Stop sending events.  Called by nwamd to destroy each System V message queue
 * registered.
 */
void
nwam_event_send_fini(void)
{
        DIR *dirp;
        struct dirent *dp;
        char eventmsgfile[MAXPATHLEN];

        (void) pthread_mutex_lock(&event_mutex);

        if ((dirp = opendir(NWAM_EVENT_MSG_DIR)) == NULL) {
                (void) pthread_mutex_unlock(&event_mutex);
                return;
        }

        /*
         * For each file matching our event message queue file prefix,
         * destroy the queue and message file.
         */
        while ((dp = readdir(dirp)) != NULL) {
                if (strncmp(dp->d_name, NWAM_EVENT_MSG_FILE,
                    strlen(NWAM_EVENT_MSG_FILE)) != 0)
                        continue;

                (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s/%s",
                    NWAM_EVENT_MSG_DIR, dp->d_name);

                nwam_event_queue_fini(eventmsgfile);
        }
        (void) pthread_mutex_unlock(&event_mutex);
}