usr/src/lib/libnwam/common/libnwam_events.c

   1 /*
   2  * CDDL HEADER START
   3  *
   4  * The contents of this file are subject to the terms of the
   5  * Common Development and Distribution License (the "License").
   6  * You may not use this file except in compliance with the License.
   7  *
   8  * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
   9  * or http://www.opensolaris.org/os/licensing.
  10  * See the License for the specific language governing permissions
  11  * and limitations under the License.
  12  *
  13  * When distributing Covered Code, include this CDDL HEADER in each
  14  * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
  15  * If applicable, add the following below this CDDL HEADER, with the
  16  * fields enclosed by brackets "[]" replaced with your own identifying
  17  * information: Portions Copyright [yyyy] [name of copyright owner]
  18  *
  19  * CDDL HEADER END
  20  */
  21
  22 /*
  23  * Copyright 2010 Sun Microsystems, Inc.  All rights reserved.
  24  * Use is subject to license terms.
  25  */
  26
  27 #include <assert.h>
  28 #include <dirent.h>
  29 #include <errno.h>
  30 #include <fcntl.h>
  31 #include <pthread.h>
  32 #include <stdio.h>
  33 #include <stdlib.h>
  34 #include <strings.h>
  35 #include <string.h>
  36 #include <syslog.h>
  37 #include <sys/msg.h>
  38 #include <sys/stat.h>
  39 #include <sys/types.h>
  40 #include <unistd.h>
  41
  42 #include "libnwam_impl.h"
  43 #include <libnwam_priv.h>
  44 #include <libnwam.h>
  45
  46 /*
  47  * Implementation of event notification mechanism used by the GUI and
  48  * nwamadm.  Clients register for events via nwam_events_init() and
  49  * unregister via nwam_events_fini().  nwamd sends events via nwam_event_send()
  50  * and applications block waiting for a new event to be delivered in
  51  * nwam_event_wait().  Events are implemented as System V message queues,
  52  * one per event client.  The event mechanism has to be resilient to
  53  * nwamd restarts so that clients do not lose the event connection.
  54  */
  55
  56 #define NWAM_EVENT_MSG_DIR              "/etc/svc/volatile/nwam/"
  57 #define NWAM_EVENT_MSG_FILE             "nwam_event_msgs"
  58 #define NWAM_EVENT_MSG_FILE_PREFIX      NWAM_EVENT_MSG_DIR NWAM_EVENT_MSG_FILE
  59 #define NWAM_EVENT_MAX_SIZE             (sizeof (struct nwam_event) + \
  60         (NWAMD_MAX_NUM_WLANS * sizeof (nwam_wlan_t)))
  61 #define NWAM_EVENT_WAIT_TIME            10
  62 #define NWAM_EVENT_MAX_NUM_PENDING      25
  63
  64 /*
  65  * This is protecting simultaneous access to the msqid and its configuration.
  66  */
  67 static pthread_mutex_t event_mutex = PTHREAD_MUTEX_INITIALIZER;
  68 static int event_msqid = -1;
  69
  70 static nwam_error_t
  71 nwam_event_alloc(nwam_event_t *eventp)
  72 {
  73         assert(eventp != NULL);
  74
  75         *eventp = calloc(1, NWAM_EVENT_MAX_SIZE);
  76         if (*eventp == NULL)
  77                 return (NWAM_NO_MEMORY);
  78         return (NWAM_SUCCESS);
  79 }
  80
  81 void
  82 nwam_event_free(nwam_event_t event)
  83 {
  84         free(event);
  85 }
  86
  87 /*
  88  * Get next event in queue.
  89  */
  90 nwam_error_t
  91 nwam_event_wait(nwam_event_t *eventp)
  92 {
  93         nwam_error_t err;
  94         nwam_event_t event;
  95
  96         assert(eventp != NULL);
  97
  98         if ((err = nwam_event_alloc(&event)) != NWAM_SUCCESS)
  99                 return (err);
 100         while (msgrcv(event_msqid, (struct msgbuf *)event, NWAM_EVENT_MAX_SIZE,
 101             0, 0) == -1) {
 102                 switch (errno) {
 103                         case EAGAIN:
 104                         case EBUSY:
 105                                 /*
 106                                  * We see this errno eventhough it isn't
 107                                  * documented.  Try again.  If this causes
 108                                  * a busy loop then grab a trace otherwise
 109                                  * it's a brace 'til we can figure out why it
 110                                  * happens.
 111                                  */
 112                                 continue;
 113
 114                         default:
 115                                 nwam_event_free(event);
 116                                 return (nwam_errno_to_nwam_error(errno));
 117                 }
 118         }
 119
 120         /* Resize event down from maximum size */
 121         if ((*eventp = realloc(event, event->nwe_size)) == NULL)
 122                 return (NWAM_NO_MEMORY);
 123
 124         return (NWAM_SUCCESS);
 125 }
 126
 127 /*
 128  * Register for receipt of events from nwamd.  Event delivery is
 129  * done via a System V message queue.
 130  */
 131 nwam_error_t
 132 nwam_events_init(void)
 133 {
 134         char eventmsgfile[MAXPATHLEN];
 135         nwam_error_t err;
 136         nwam_error_t rc = NWAM_SUCCESS;
 137         key_t key;
 138
 139         (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s.%d",
 140             NWAM_EVENT_MSG_FILE_PREFIX, getpid());
 141
 142         (void) pthread_mutex_lock(&event_mutex);
 143
 144         if (event_msqid != -1) {
 145                 rc = NWAM_ENTITY_IN_USE;
 146                 goto exit;
 147         }
 148
 149         if ((err = nwam_request_register_unregister
 150             (NWAM_REQUEST_TYPE_EVENT_REGISTER, eventmsgfile)) != NWAM_SUCCESS) {
 151                 rc = err;
 152                 goto exit;
 153         }
 154
 155         if ((key = ftok(eventmsgfile, 0)) == -1) {
 156                 rc = nwam_errno_to_nwam_error(errno);
 157                 goto exit;
 158         }
 159
 160         /* Get system-wide message queue ID */
 161         if ((event_msqid = msgget(key, 0444)) == -1) {
 162                 rc = nwam_errno_to_nwam_error(errno);
 163                 goto exit;
 164         }
 165
 166 exit:
 167         (void) pthread_mutex_unlock(&event_mutex);
 168
 169         return (rc);
 170 }
 171
 172 /*
 173  * Un-register for receipt of events from nwamd.  Make a request to nwamd
 174  * to destroy the message queue.
 175  */
 176 void
 177 nwam_events_fini(void)
 178 {
 179         char eventmsgfile[MAXPATHLEN];
 180
 181         (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s.%d",
 182             NWAM_EVENT_MSG_FILE_PREFIX, getpid());
 183
 184         (void) pthread_mutex_lock(&event_mutex);
 185
 186         (void) nwam_request_register_unregister
 187             (NWAM_REQUEST_TYPE_EVENT_UNREGISTER, eventmsgfile);
 188
 189         event_msqid = -1;
 190
 191         (void) pthread_mutex_unlock(&event_mutex);
 192 }
 193
 194 /*
 195  * Create an event queue.  Called by nwamd to create System V message queues
 196  * for clients to listen for events.
 197  */
 198 nwam_error_t
 199 nwam_event_queue_init(const char *eventmsgfile)
 200 {
 201         int fd;
 202         key_t key;
 203
 204         if ((fd = open(eventmsgfile, O_RDWR | O_CREAT | O_TRUNC, 0644)) == -1)
 205                 return (nwam_errno_to_nwam_error(errno));
 206         (void) close(fd);
 207
 208         if ((key = ftok(eventmsgfile, 0)) == -1)
 209                 return (nwam_errno_to_nwam_error(errno));
 210
 211         if (msgget(key, 0644 | IPC_CREAT) == -1)
 212                 return (nwam_errno_to_nwam_error(errno));
 213
 214         return (NWAM_SUCCESS);
 215 }
 216
 217 /*
 218  * Send event to registered listeners via the set of registered System V
 219  * message queues.
 220  */
 221 nwam_error_t
 222 nwam_event_send(nwam_event_t event)
 223 {
 224         DIR *dirp;
 225         struct dirent *dp;
 226         struct msqid_ds buf;
 227         key_t key;
 228         int msqid;
 229         char eventmsgfile[MAXPATHLEN];
 230         nwam_error_t err = NWAM_SUCCESS;
 231
 232         if ((dirp = opendir(NWAM_EVENT_MSG_DIR)) == NULL) {
 233                 return (nwam_errno_to_nwam_error(errno));
 234         }
 235
 236         /*
 237          * For each file matching our event message queue file prefix,
 238          * check the queue is still being read, and if so send the message.
 239          */
 240         while ((dp = readdir(dirp)) != NULL) {
 241                 if (strncmp(dp->d_name, NWAM_EVENT_MSG_FILE,
 242                     strlen(NWAM_EVENT_MSG_FILE)) != 0)
 243                         continue;
 244
 245                 (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s/%s",
 246                     NWAM_EVENT_MSG_DIR, dp->d_name);
 247
 248                 if ((key = ftok(eventmsgfile, 0)) == -1) {
 249                         int errno_save = errno;
 250                         syslog(LOG_INFO, "nwam_event_send: ftok: %s",
 251                             strerror(errno_save));
 252                         err = nwam_errno_to_nwam_error(errno_save);
 253                         continue;
 254                 }
 255
 256                 if ((msqid = msgget(key, 0644)) == -1) {
 257                         int errno_save = errno;
 258                         syslog(LOG_INFO, "nwam_event_send: msgget: %s",
 259                             strerror(errno_save));
 260                         err = nwam_errno_to_nwam_error(errno_save);
 261                         continue;
 262                 }
 263
 264                 /* Retrieve stats to analyse queue activity */
 265                 if (msgctl(msqid, IPC_STAT, &buf) == -1) {
 266                         int errno_save = errno;
 267                         syslog(LOG_INFO, "nwam_event_send: msgctl: %s",
 268                             strerror(errno_save));
 269                         err = nwam_errno_to_nwam_error(errno_save);
 270                         continue;
 271                 }
 272                 /*
 273                  * If buf.msg_qnum > NWAM_EVENT_MAX_NUM_PENDING
 274                  * _and_ msg_stime is more than 10s after msg_rtime -
 275                  * indicating message(s) have been hanging around unclaimed -
 276                  * we destroy the queue as the client has most likely gone
 277                  * away. This can happen if a registered client hits Ctrl^C.
 278                  */
 279                 if (buf.msg_qnum > NWAM_EVENT_MAX_NUM_PENDING &&
 280                     ((buf.msg_stime + NWAM_EVENT_WAIT_TIME) > buf.msg_rtime)) {
 281                         nwam_event_queue_fini(eventmsgfile);
 282                         continue;
 283                 }
 284
 285                 /*
 286                  * This shouldn't ever block.  If it does then log an error and
 287                  * clean up the queue.
 288                  */
 289                 if (msgsnd(msqid, (struct msgbuf *)event, event->nwe_size,
 290                     IPC_NOWAIT) == -1) {
 291                         int errno_save = errno;
 292                         syslog(LOG_ERR, "nwam_event_send: msgsnd: %s, "
 293                             "destroying message queue %s", strerror(errno_save),
 294                             eventmsgfile);
 295                         nwam_event_queue_fini(eventmsgfile);
 296                         err = nwam_errno_to_nwam_error(errno_save);
 297                         continue;
 298                 }
 299
 300         }
 301         (void) closedir(dirp);
 302
 303         return (err);
 304 }
 305
 306 /*
 307  * Destroy an event queue.  Called by nwamd to destroy the associated message
 308  * queue.
 309  */
 310 void
 311 nwam_event_queue_fini(const char *eventmsgfile)
 312 {
 313         key_t key;
 314         int msqid;
 315
 316         if ((key = ftok(eventmsgfile, 0)) != -1 &&
 317             (msqid = msgget(key, 0644)) != -1 &&
 318             msgctl(msqid, IPC_RMID, NULL) != -1)
 319                 (void) unlink(eventmsgfile);
 320 }
 321
 322 /*
 323  * Stop sending events.  Called by nwamd to destroy each System V message queue
 324  * registered.
 325  */
 326 void
 327 nwam_event_send_fini(void)
 328 {
 329         DIR *dirp;
 330         struct dirent *dp;
 331         char eventmsgfile[MAXPATHLEN];
 332
 333         (void) pthread_mutex_lock(&event_mutex);
 334
 335         if ((dirp = opendir(NWAM_EVENT_MSG_DIR)) == NULL) {
 336                 (void) pthread_mutex_unlock(&event_mutex);
 337                 return;
 338         }
 339
 340         /*
 341          * For each file matching our event message queue file prefix,
 342          * destroy the queue and message file.
 343          */
 344         while ((dp = readdir(dirp)) != NULL) {
 345                 if (strncmp(dp->d_name, NWAM_EVENT_MSG_FILE,
 346                     strlen(NWAM_EVENT_MSG_FILE)) != 0)
 347                         continue;
 348
 349                 (void) snprintf(eventmsgfile, sizeof (eventmsgfile), "%s/%s",
 350                     NWAM_EVENT_MSG_DIR, dp->d_name);
 351
 352                 nwam_event_queue_fini(eventmsgfile);
 353         }
 354         (void) pthread_mutex_unlock(&event_mutex);
 355 }