source3/lib/async_req.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    Infrastructure for async requests
   4    Copyright (C) Volker Lendecke 2008
   5
   6    This program is free software; you can redistribute it and/or modify
   7    it under the terms of the GNU General Public License as published by
   8    the Free Software Foundation; either version 3 of the License, or
   9    (at your option) any later version.
  10
  11    This program is distributed in the hope that it will be useful,
  12    but WITHOUT ANY WARRANTY; without even the implied warranty of
  13    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  14    GNU General Public License for more details.
  15
  16    You should have received a copy of the GNU General Public License
  17    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  18 */
  19
  20 #include "includes.h"
  21
  22 /**
  23  * @brief Print an async_req structure
  24  * @param[in] mem_ctx   The memory context for the result
  25  * @param[in] req       The request to be printed
  26  * @retval              Text representation of req
  27  *
  28  * This is a default print function for async requests. Implementations should
  29  * override this with more specific information.
  30  *
  31  * This function should not be used by async API users, this is non-static
  32  * only to allow implementations to easily provide default information in
  33  * their specific functions.
  34  */
  35
  36 char *async_req_print(TALLOC_CTX *mem_ctx, struct async_req *req)
  37 {
  38         return talloc_asprintf(mem_ctx, "async_req: state=%d, status=%s, "
  39                                "priv=%s", req->state, nt_errstr(req->status),
  40                                talloc_get_name(req->private_data));
  41 }
  42
  43 /**
  44  * @brief Create an async request
  45  * @param[in] mem_ctx   The memory context for the result
  46  * @param[in] ev        The event context this async request will be driven by
  47  * @retval              A new async request
  48  *
  49  * The new async request will be initialized in state ASYNC_REQ_IN_PROGRESS
  50  */
  51
  52 struct async_req *async_req_new(TALLOC_CTX *mem_ctx)
  53 {
  54         struct async_req *result;
  55
  56         result = TALLOC_ZERO_P(mem_ctx, struct async_req);
  57         if (result == NULL) {
  58                 return NULL;
  59         }
  60         result->state = ASYNC_REQ_IN_PROGRESS;
  61         result->print = async_req_print;
  62         return result;
  63 }
  64
  65 /**
  66  * @brief An async request has successfully finished
  67  * @param[in] req       The finished request
  68  *
  69  * async_req_done is to be used by implementors of async requests. When a
  70  * request is successfully finished, this function calls the user's completion
  71  * function.
  72  */
  73
  74 void async_req_done(struct async_req *req)
  75 {
  76         req->status = NT_STATUS_OK;
  77         req->state = ASYNC_REQ_DONE;
  78         if (req->async.fn != NULL) {
  79                 req->async.fn(req);
  80         }
  81 }
  82
  83 /**
  84  * @brief An async request has seen an error
  85  * @param[in] req       The request with an error
  86  * @param[in] status    The error code
  87  *
  88  * async_req_done is to be used by implementors of async requests. When a
  89  * request can not successfully completed, the implementation should call this
  90  * function with the appropriate status code.
  91  */
  92
  93 void async_req_error(struct async_req *req, NTSTATUS status)
  94 {
  95         req->status = status;
  96         req->state = ASYNC_REQ_ERROR;
  97         if (req->async.fn != NULL) {
  98                 req->async.fn(req);
  99         }
 100 }
 101
 102 /**
 103  * @brief Timed event callback
 104  * @param[in] ev        Event context
 105  * @param[in] te        The timed event
 106  * @param[in] now       zero time
 107  * @param[in] priv      The async request to be finished
 108  */
 109
 110 static void async_trigger(struct event_context *ev, struct timed_event *te,
 111                           struct timeval now, void *priv)
 112 {
 113         struct async_req *req = talloc_get_type_abort(priv, struct async_req);
 114
 115         TALLOC_FREE(te);
 116         if (NT_STATUS_IS_OK(req->status)) {
 117                 async_req_done(req);
 118         }
 119         else {
 120                 async_req_error(req, req->status);
 121         }
 122 }
 123
 124 /**
 125  * @brief Finish a request before it started processing
 126  * @param[in] req       The finished request
 127  * @param[in] status    The success code
 128  *
 129  * An implementation of an async request might find that it can either finish
 130  * the request without waiting for an external event, or it can't even start
 131  * the engine. To present the illusion of a callback to the user of the API,
 132  * the implementation can call this helper function which triggers an
 133  * immediate timed event. This way the caller can use the same calling
 134  * conventions, independent of whether the request was actually deferred.
 135  */
 136
 137 bool async_post_status(struct async_req *req, struct event_context *ev,
 138                        NTSTATUS status)
 139 {
 140         req->status = status;
 141
 142         if (event_add_timed(ev, req, timeval_zero(),
 143                             async_trigger, req) == NULL) {
 144                 return false;
 145         }
 146         return true;
 147 }
 148
 149 /**
 150  * @brief Helper function for nomem check
 151  * @param[in] p         The pointer to be checked
 152  * @param[in] req       The request being processed
 153  *
 154  * Convenience helper to easily check alloc failure within a callback
 155  * implementing the next step of an async request.
 156  *
 157  * Call pattern would be
 158  * \code
 159  * p = talloc(mem_ctx, bla);
 160  * if (async_req_nomem(p, req)) {
 161  *      return;
 162  * }
 163  * \endcode
 164  */
 165
 166 bool async_req_nomem(const void *p, struct async_req *req)
 167 {
 168         if (p != NULL) {
 169                 return false;
 170         }
 171         async_req_error(req, NT_STATUS_NO_MEMORY);
 172         return true;
 173 }
 174
 175 bool async_req_is_error(struct async_req *req, NTSTATUS *status)
 176 {
 177         if (req->state < ASYNC_REQ_DONE) {
 178                 *status = NT_STATUS_INTERNAL_ERROR;
 179                 return true;
 180         }
 181         if (req->state == ASYNC_REQ_ERROR) {
 182                 *status = req->status;
 183                 return true;
 184         }
 185         return false;
 186 }
 187
 188 NTSTATUS async_req_simple_recv(struct async_req *req)
 189 {
 190         NTSTATUS status;
 191
 192         if (async_req_is_error(req, &status)) {
 193                 return status;
 194         }
 195         return NT_STATUS_OK;
 196 }
 197
 198 static void async_req_timedout(struct event_context *ev,
 199                                struct timed_event *te,
 200                                struct timeval now,
 201                                void *priv)
 202 {
 203         struct async_req *req = talloc_get_type_abort(
 204                 priv, struct async_req);
 205         TALLOC_FREE(te);
 206         async_req_error(req, NT_STATUS_IO_TIMEOUT);
 207 }
 208
 209 bool async_req_set_timeout(struct async_req *req, struct event_context *ev,
 210                            struct timeval to)
 211 {
 212         return (event_add_timed(ev, req,
 213                                 timeval_current_ofs(to.tv_sec, to.tv_usec),
 214                                 async_req_timedout, req)
 215                 != NULL);
 216 }
 217
 218 struct async_req *async_wait_send(TALLOC_CTX *mem_ctx,
 219                                   struct event_context *ev,
 220                                   struct timeval to)
 221 {
 222         struct async_req *result;
 223
 224         result = async_req_new(mem_ctx);
 225         if (result == NULL) {
 226                 return result;
 227         }
 228         if (!async_req_set_timeout(result, ev, to)) {
 229                 TALLOC_FREE(result);
 230                 return NULL;
 231         }
 232         return result;
 233 }
 234
 235 NTSTATUS async_wait_recv(struct async_req *req)
 236 {
 237         return NT_STATUS_OK;
 238 }
 239
 240 struct async_queue_entry {
 241         struct async_queue_entry *prev, *next;
 242         struct async_req_queue *queue;
 243         struct async_req *req;
 244         void (*trigger)(struct async_req *req);
 245 };
 246
 247 struct async_req_queue {
 248         struct async_queue_entry *queue;
 249 };
 250
 251 struct async_req_queue *async_req_queue_init(TALLOC_CTX *mem_ctx)
 252 {
 253         return TALLOC_ZERO_P(mem_ctx, struct async_req_queue);
 254 }
 255
 256 static int async_queue_entry_destructor(struct async_queue_entry *e)
 257 {
 258         struct async_req_queue *queue = e->queue;
 259
 260         DLIST_REMOVE(queue->queue, e);
 261
 262         if (queue->queue != NULL) {
 263                 queue->queue->trigger(queue->queue->req);
 264         }
 265
 266         return 0;
 267 }
 268
 269 static void async_req_immediate_trigger(struct event_context *ev,
 270                                         struct timed_event *te,
 271                                         struct timeval now,
 272                                         void *priv)
 273 {
 274         struct async_queue_entry *e = talloc_get_type_abort(
 275                 priv, struct async_queue_entry);
 276
 277         TALLOC_FREE(te);
 278         e->trigger(e->req);
 279 }
 280
 281 bool async_req_enqueue(struct async_req_queue *queue, struct event_context *ev,
 282                        struct async_req *req,
 283                        void (*trigger)(struct async_req *req))
 284 {
 285         struct async_queue_entry *e;
 286         bool busy;
 287
 288         busy = (queue->queue != NULL);
 289
 290         e = talloc(req, struct async_queue_entry);
 291         if (e == NULL) {
 292                 return false;
 293         }
 294
 295         e->req = req;
 296         e->trigger = trigger;
 297         e->queue = queue;
 298
 299         DLIST_ADD_END(queue->queue, e, struct async_queue_entry *);
 300         talloc_set_destructor(e, async_queue_entry_destructor);
 301
 302         if (!busy) {
 303                 struct timed_event *te;
 304
 305                 te = event_add_timed(ev, e, timeval_zero(),
 306                                      async_req_immediate_trigger,
 307                                      e);
 308                 if (te == NULL) {
 309                         TALLOC_FREE(e);
 310                         return false;
 311                 }
 312         }
 313
 314         return true;
 315 }