src/dht/dht_api.c

   1 /*
   2      This file is part of GNUnet.
   3      (C) 2009, 2010 Christian Grothoff (and other contributing authors)
   4
   5      GNUnet is free software; you can redistribute it and/or modify
   6      it under the terms of the GNU General Public License as published
   7      by the Free Software Foundation; either version 3, or (at your
   8      option) any later version.
   9
  10      GNUnet is distributed in the hope that it will be useful, but
  11      WITHOUT ANY WARRANTY; without even the implied warranty of
  12      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13      General Public License for more details.
  14
  15      You should have received a copy of the GNU General Public License
  16      along with GNUnet; see the file COPYING.  If not, write to the
  17      Free Software Foundation, Inc., 59 Temple Place - Suite 330,
  18      Boston, MA 02111-1307, USA.
  19 */
  20
  21 /**
  22  * @file dht/dht_api.c
  23  * @brief library to access the DHT service
  24  * @author Christian Grothoff
  25  * @author Nathan Evans
  26  */
  27
  28 #include "platform.h"
  29 #include "gnunet_bandwidth_lib.h"
  30 #include "gnunet_client_lib.h"
  31 #include "gnunet_constants.h"
  32 #include "gnunet_container_lib.h"
  33 #include "gnunet_arm_service.h"
  34 #include "gnunet_hello_lib.h"
  35 #include "gnunet_protocols.h"
  36 #include "gnunet_server_lib.h"
  37 #include "gnunet_time_lib.h"
  38 #include "gnunet_dht_service.h"
  39 #include "dht.h"
  40
  41 #define DEBUG_DHT_API GNUNET_NO
  42
  43 /**
  44  * Entry in our list of messages to be (re-)transmitted.
  45  */
  46 struct PendingMessage
  47 {
  48   /**
  49    * This is a doubly-linked list.
  50    */
  51   struct PendingMessage *prev;
  52
  53   /**
  54    * This is a doubly-linked list.
  55    */
  56   struct PendingMessage *next;
  57
  58   /**
  59    * Message that is pending, allocated at the end
  60    * of this struct.
  61    */
  62   const struct GNUNET_MessageHeader *msg;
  63
  64   /**
  65    * Handle to the DHT API context.
  66    */
  67   struct GNUNET_DHT_Handle *handle;
  68
  69   /**
  70    * Continuation to call when the request has been
  71    * transmitted (for the first time) to the service; can be NULL.
  72    */
  73   GNUNET_SCHEDULER_Task cont;
  74
  75   /**
  76    * Closure for 'cont'.
  77    */
  78   void *cont_cls;
  79
  80   /**
  81    * Timeout task for this message
  82    */
  83   GNUNET_SCHEDULER_TaskIdentifier timeout_task;
  84
  85   /**
  86    * Unique ID for this request
  87    */
  88   uint64_t unique_id;
  89
  90   /**
  91    * Free the saved message once sent, set to GNUNET_YES for messages
  92    * that do not receive responses; GNUNET_NO if this pending message
  93    * is aliased from a 'struct GNUNET_DHT_RouteHandle' and will be freed
  94    * from there.
  95    */
  96   int free_on_send;
  97
  98   /**
  99    * GNUNET_YES if this message is in our pending queue right now.
 100    */
 101   int in_pending_queue;
 102
 103 };
 104
 105
 106 /**
 107  * Handle to a route request
 108  */
 109 struct GNUNET_DHT_RouteHandle
 110 {
 111
 112   /**
 113    * Iterator to call on data receipt
 114    */
 115   GNUNET_DHT_ReplyProcessor iter;
 116
 117   /**
 118    * Closure for the iterator callback
 119    */
 120   void *iter_cls;
 121
 122   /**
 123    * Main handle to this DHT api
 124    */
 125   struct GNUNET_DHT_Handle *dht_handle;
 126
 127   /**
 128    * The actual message sent for this request,
 129    * used for retransmitting requests on service
 130    * failure/reconnect.  Freed on route_stop.
 131    */
 132   struct PendingMessage *message;
 133
 134   /**
 135    * Key that this get request is for
 136    */
 137   GNUNET_HashCode key;
 138
 139   /**
 140    * Unique identifier for this request (for key collisions). FIXME: redundant!?
 141    */
 142   uint64_t uid;
 143
 144 };
 145
 146
 147 /**
 148  * Connection to the DHT service.
 149  */
 150 struct GNUNET_DHT_Handle
 151 {
 152   /**
 153    * Our scheduler.
 154    */
 155   struct GNUNET_SCHEDULER_Handle *sched;
 156
 157   /**
 158    * Configuration to use.
 159    */
 160   const struct GNUNET_CONFIGURATION_Handle *cfg;
 161
 162   /**
 163    * Socket (if available).
 164    */
 165   struct GNUNET_CLIENT_Connection *client;
 166
 167   /**
 168    * Currently pending transmission request (or NULL).
 169    */
 170   struct GNUNET_CLIENT_TransmitHandle *th;
 171
 172   /**
 173    * Head of linked list of messages we would like to transmit.
 174    */
 175   struct PendingMessage *pending_head;
 176
 177   /**
 178    * Tail of linked list of messages we would like to transmit.
 179    */
 180   struct PendingMessage *pending_tail;
 181
 182   /**
 183    * Hash map containing the current outstanding unique requests
 184    * (values are of type 'struct GNUNET_DHT_RouteHandle').
 185    */
 186   struct GNUNET_CONTAINER_MultiHashMap *active_requests;
 187
 188   /**
 189    * Generator for unique ids.
 190    */
 191   uint64_t uid_gen;
 192
 193 };
 194
 195
 196 /**
 197  * Transmit the next pending message, called by notify_transmit_ready
 198  */
 199 static size_t
 200 transmit_pending (void *cls,
 201                   size_t size,
 202                   void *buf);
 203
 204
 205 /**
 206  * Handler for messages received from the DHT service
 207  * a demultiplexer which handles numerous message types
 208  *
 209  */
 210 static void
 211 service_message_handler (void *cls,
 212                          const struct GNUNET_MessageHeader *msg);
 213
 214
 215
 216
 217 /**
 218  * Try to (re)connect to the DHT service.
 219  *
 220  * @return GNUNET_YES on success, GNUNET_NO on failure.
 221  */
 222 static int
 223 try_connect (struct GNUNET_DHT_Handle *handle)
 224 {
 225   if (handle->client != NULL)
 226     return GNUNET_OK;
 227   handle->client = GNUNET_CLIENT_connect (handle->sched, "dht", handle->cfg);
 228   if (handle->client == NULL)
 229     {
 230       GNUNET_log (GNUNET_ERROR_TYPE_WARNING,
 231                   _("Failed to connect to the DHT service!\n"));
 232       return GNUNET_NO;
 233     }
 234   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 235               "Starting to process replies from DHT\n");
 236   GNUNET_CLIENT_receive (handle->client,
 237                          &service_message_handler,
 238                          handle,
 239                          GNUNET_TIME_UNIT_FOREVER_REL);
 240   return GNUNET_YES;
 241 }
 242
 243
 244 /**
 245  * Add the request corresponding to the given route handle
 246  * to the pending queue (if it is not already in there).
 247  *
 248  * @param cls the 'struct GNUNET_DHT_Handle*'
 249  * @param key key for the request (not used)
 250  * @param value the 'struct GNUNET_DHT_RouteHandle*'
 251  * @return GNUNET_YES (always)
 252  */
 253 static int
 254 add_request_to_pending (void *cls,
 255                         const GNUNET_HashCode *key,
 256                         void *value)
 257 {
 258   struct GNUNET_DHT_Handle *handle = cls;
 259   struct GNUNET_DHT_RouteHandle *rh = value;
 260
 261   if (GNUNET_NO == rh->message->in_pending_queue)
 262     {
 263       GNUNET_CONTAINER_DLL_insert (handle->pending_head,
 264                                    handle->pending_tail,
 265                                    rh->message);
 266       rh->message->in_pending_queue = GNUNET_YES;
 267     }
 268   return GNUNET_YES;
 269 }
 270
 271
 272 /**
 273  * Re-connect to the DHT, re-issue all pending requests if needed.
 274  */
 275 static void
 276 reconnect (struct GNUNET_DHT_Handle *handle)
 277 {
 278   if (handle->client != NULL)
 279     {
 280       GNUNET_CLIENT_disconnect (handle->client,
 281                                 GNUNET_NO);
 282       handle->client = NULL;
 283     }
 284   if (GNUNET_YES != try_connect (handle))
 285     return;
 286   GNUNET_CONTAINER_multihashmap_iterate (handle->active_requests,
 287                                          &add_request_to_pending,
 288                                          handle);
 289   if (handle->pending_head == NULL)
 290     return;
 291   GNUNET_CLIENT_notify_transmit_ready (handle->client,
 292                                        ntohs(handle->pending_head->msg->size),
 293                                        GNUNET_TIME_UNIT_FOREVER_REL,
 294                                        GNUNET_NO,
 295                                        &transmit_pending,
 296                                        handle);
 297
 298 }
 299
 300
 301 /**
 302  * Try to send messages from list of messages to send
 303  */
 304 static void
 305 process_pending_messages (struct GNUNET_DHT_Handle *handle)
 306 {
 307   struct PendingMessage *head;
 308
 309   if (GNUNET_YES != try_connect (handle))
 310     return;
 311   if (handle->th != NULL)
 312     return;
 313   if (NULL == (head = handle->pending_head))
 314     return;
 315   handle->th = GNUNET_CLIENT_notify_transmit_ready (handle->client,
 316                                                     ntohs (head->msg->size),
 317                                                     GNUNET_TIME_UNIT_FOREVER_REL,
 318                                                     GNUNET_YES,
 319                                                     &transmit_pending,
 320                                                     handle);
 321   if (NULL == handle->th)
 322     {
 323       reconnect (handle);
 324       return;
 325     }
 326 }
 327
 328
 329 /**
 330  * Transmit the next pending message, called by notify_transmit_ready
 331  */
 332 static size_t
 333 transmit_pending (void *cls,
 334                   size_t size,
 335                   void *buf)
 336 {
 337   struct GNUNET_DHT_Handle *handle = cls;
 338   struct PendingMessage *head;
 339   size_t tsize;
 340
 341   handle->th = NULL;
 342   if (buf == NULL)
 343     {
 344       reconnect (handle);
 345       return 0;
 346     }
 347   if (NULL == (head = handle->pending_head))
 348     return 0;
 349
 350   tsize = ntohs (head->msg->size);
 351   if (size < tsize)
 352     {
 353       process_pending_messages (handle);
 354       return 0;
 355     }
 356   memcpy (buf, head->msg, tsize);
 357   GNUNET_CONTAINER_DLL_remove (handle->pending_head,
 358                                handle->pending_tail,
 359                                head);
 360   if (head->timeout_task != GNUNET_SCHEDULER_NO_TASK)
 361     {
 362       GNUNET_SCHEDULER_cancel (handle->sched,
 363                                head->timeout_task);
 364       head->timeout_task = GNUNET_SCHEDULER_NO_TASK;
 365     }
 366   if (NULL != head->cont)
 367     {
 368       GNUNET_SCHEDULER_add_continuation (handle->sched,
 369                                          head->cont,
 370                                          head->cont_cls,
 371                                          GNUNET_SCHEDULER_REASON_PREREQ_DONE);
 372       head->cont = NULL;
 373       head->cont_cls = NULL;
 374     }
 375   head->in_pending_queue = GNUNET_NO;
 376   if (GNUNET_YES == head->free_on_send)
 377     GNUNET_free (head);
 378   process_pending_messages (handle);
 379   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 380               "Forwarded request of %u bytes to DHT service\n",
 381               (unsigned int) tsize);
 382   return tsize;
 383 }
 384
 385
 386
 387
 388 /**
 389  * Process a given reply that might match the given
 390  * request.
 391  */
 392 static int
 393 process_reply (void *cls,
 394                const GNUNET_HashCode *key,
 395                void *value)
 396 {
 397   const struct GNUNET_DHT_RouteResultMessage *dht_msg = cls;
 398   struct GNUNET_DHT_RouteHandle *rh = value;
 399   const struct GNUNET_MessageHeader *enc_msg;
 400   size_t enc_size;
 401   uint64_t uid;
 402   const struct GNUNET_PeerIdentity **get_path;
 403   const struct GNUNET_PeerIdentity **put_path;
 404   const struct GNUNET_PeerIdentity *pos;
 405   uint16_t gpl;
 406   uint16_t ppl;
 407   unsigned int i;
 408
 409   uid = GNUNET_ntohll (dht_msg->unique_id);
 410   if (uid != rh->uid)
 411     {
 412       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 413                   "Reply UID did not match request UID\n");
 414       return GNUNET_YES;
 415     }
 416   enc_size = ntohs (dht_msg->header.size) - sizeof (struct GNUNET_DHT_RouteResultMessage);
 417   if (enc_size < sizeof (struct GNUNET_MessageHeader))
 418     {
 419       GNUNET_break (0);
 420       return GNUNET_NO;
 421     }
 422   pos = (const struct GNUNET_PeerIdentity *) &dht_msg[1];
 423   ppl = ntohs (dht_msg->put_path_length);
 424   gpl = ntohs (dht_msg->get_path_length);
 425   if ( (ppl + gpl) * sizeof (struct GNUNET_PeerIdentity) > enc_size)
 426     {
 427       GNUNET_break (0);
 428       return GNUNET_NO;
 429     }
 430   if (ppl > 0)
 431     {
 432       put_path = GNUNET_malloc ((ppl+1) * sizeof (struct GNUNET_PeerIdentity*));
 433       for (i=0;i<ppl;i++)
 434         {
 435           put_path[i] = pos;
 436           pos++;
 437         }
 438       put_path[ppl] = NULL;
 439     }
 440   else
 441     put_path = NULL;
 442   if (gpl > 0)
 443     {
 444       get_path = GNUNET_malloc ((gpl+1) * sizeof (struct GNUNET_PeerIdentity*));
 445       for (i=0;i<gpl;i++)
 446         {
 447           get_path[i] = pos;
 448           pos++;
 449         }
 450       get_path[gpl] = NULL;
 451     }
 452   else
 453     get_path = NULL;
 454   enc_size -= (ppl + gpl) * sizeof (struct GNUNET_PeerIdentity);
 455   enc_msg = (const struct GNUNET_MessageHeader *) pos;
 456   if (enc_size != ntohs (enc_msg->size))
 457     {
 458       GNUNET_break (0);
 459       GNUNET_free_non_null (get_path);
 460       GNUNET_free_non_null (put_path);
 461       return GNUNET_NO;
 462     }
 463   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 464               "Processing reply.\n");
 465   rh->iter (rh->iter_cls,
 466             &rh->key,
 467             get_path,
 468             put_path,
 469             enc_msg);
 470   GNUNET_free_non_null (get_path);
 471   GNUNET_free_non_null (put_path);
 472   return GNUNET_YES;
 473 }
 474
 475
 476 /**
 477  * Handler for messages received from the DHT service
 478  * a demultiplexer which handles numerous message types
 479  *
 480  * @param cls the 'struct GNUNET_DHT_Handle'
 481  * @param msg the incoming message
 482  */
 483 static void
 484 service_message_handler (void *cls,
 485                          const struct GNUNET_MessageHeader *msg)
 486 {
 487   struct GNUNET_DHT_Handle *handle = cls;
 488   const struct GNUNET_DHT_RouteResultMessage *dht_msg;
 489
 490   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 491               "%s called\n",
 492               __FUNCTION__);
 493   if (msg == NULL)
 494     {
 495       GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 496                   "Error receiving data from DHT service, reconnecting\n");
 497       reconnect (handle);
 498       return;
 499     }
 500   if (ntohs (msg->type) != GNUNET_MESSAGE_TYPE_DHT_LOCAL_ROUTE_RESULT)
 501     {
 502       GNUNET_break (0);
 503       reconnect (handle);
 504       return;
 505     }
 506   if (ntohs (msg->size) < sizeof (struct GNUNET_DHT_RouteResultMessage))
 507     {
 508       GNUNET_break (0);
 509       reconnect (handle);
 510       return;
 511     }
 512   dht_msg = (const struct GNUNET_DHT_RouteResultMessage *) msg;
 513   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 514               "Comparing reply `%s' against %u pending requests.\n",
 515               GNUNET_h2s (&dht_msg->key),
 516               GNUNET_CONTAINER_multihashmap_size (handle->active_requests));
 517   GNUNET_CONTAINER_multihashmap_get_multiple (handle->active_requests,
 518                                               &dht_msg->key,
 519                                               &process_reply,
 520                                               (void*) dht_msg);
 521   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 522               "Continuing to process replies from DHT\n");
 523   GNUNET_CLIENT_receive (handle->client,
 524                          &service_message_handler,
 525                          handle, GNUNET_TIME_UNIT_FOREVER_REL);
 526
 527 }
 528
 529
 530 /**
 531  * Initialize the connection with the DHT service.
 532  *
 533  * @param sched scheduler to use
 534  * @param cfg configuration to use
 535  * @param ht_len size of the internal hash table to use for
 536  *               processing multiple GET/FIND requests in parallel
 537  *
 538  * @return handle to the DHT service, or NULL on error
 539  */
 540 struct GNUNET_DHT_Handle *
 541 GNUNET_DHT_connect (struct GNUNET_SCHEDULER_Handle *sched,
 542                     const struct GNUNET_CONFIGURATION_Handle *cfg,
 543                     unsigned int ht_len)
 544 {
 545   struct GNUNET_DHT_Handle *handle;
 546
 547   handle = GNUNET_malloc (sizeof (struct GNUNET_DHT_Handle));
 548   handle->cfg = cfg;
 549   handle->sched = sched;
 550   handle->uid_gen = GNUNET_CRYPTO_random_u64(GNUNET_CRYPTO_QUALITY_WEAK, UINT64_MAX);
 551   handle->active_requests = GNUNET_CONTAINER_multihashmap_create (ht_len);
 552   if (GNUNET_NO == try_connect (handle))
 553     {
 554       GNUNET_DHT_disconnect (handle);
 555       return NULL;
 556     }
 557   return handle;
 558 }
 559
 560
 561 /**
 562  * Shutdown connection with the DHT service.
 563  *
 564  * @param handle handle of the DHT connection to stop
 565  */
 566 void
 567 GNUNET_DHT_disconnect (struct GNUNET_DHT_Handle *handle)
 568 {
 569   struct PendingMessage *pm;
 570
 571   GNUNET_assert (0 == GNUNET_CONTAINER_multihashmap_size(handle->active_requests));
 572   if (handle->th != NULL)
 573     {
 574       GNUNET_CLIENT_notify_transmit_ready_cancel (handle->th);
 575       handle->th = NULL;
 576     }
 577   while (NULL != (pm = handle->pending_head))
 578     {
 579       GNUNET_CONTAINER_DLL_remove (handle->pending_head,
 580                                    handle->pending_tail,
 581                                    pm);
 582       GNUNET_assert (GNUNET_YES == pm->free_on_send);
 583       if (GNUNET_SCHEDULER_NO_TASK != pm->timeout_task)
 584         GNUNET_SCHEDULER_cancel (handle->sched,
 585                                  pm->timeout_task);
 586       if (NULL != pm->cont)
 587         GNUNET_SCHEDULER_add_continuation (handle->sched,
 588                                            pm->cont,
 589                                            pm->cont_cls,
 590                                            GNUNET_SCHEDULER_REASON_TIMEOUT);
 591       pm->in_pending_queue = GNUNET_NO;
 592       GNUNET_free (pm);
 593     }
 594   if (handle->client != NULL)
 595     {
 596       GNUNET_CLIENT_disconnect (handle->client, GNUNET_YES);
 597       handle->client = NULL;
 598     }
 599   GNUNET_CONTAINER_multihashmap_destroy(handle->active_requests);
 600   GNUNET_free (handle);
 601 }
 602
 603
 604
 605
 606 /* ***** Special low-level API providing generic routing abstraction ***** */
 607
 608
 609 /**
 610  * Timeout for the transmission of a fire&forget-request.  Clean it up.
 611  *
 612  * @param cls the 'struct PendingMessage'
 613  * @param tc scheduler context
 614  */
 615 static void
 616 timeout_route_request (void *cls,
 617                        const struct GNUNET_SCHEDULER_TaskContext *tc)
 618 {
 619   struct PendingMessage *pending = cls;
 620   struct GNUNET_DHT_Handle *handle;
 621
 622   if (pending->free_on_send != GNUNET_YES)
 623     {
 624       /* timeouts should only apply to fire & forget requests! */
 625       GNUNET_break (0);
 626       return;
 627     }
 628   handle = pending->handle;
 629   GNUNET_CONTAINER_DLL_remove (handle->pending_head,
 630                                handle->pending_tail,
 631                                pending);
 632   if (pending->cont != NULL)
 633     pending->cont (pending->cont_cls,
 634                    tc);
 635   GNUNET_free (pending);
 636 }
 637
 638
 639 /**
 640  * Initiate a generic DHT route operation.
 641  *
 642  * @param handle handle to the DHT service
 643  * @param key the key to look up
 644  * @param desired_replication_level how many peers should ultimately receive
 645  *                this message (advisory only, target may be too high for the
 646  *                given DHT or not hit exactly).
 647  * @param options options for routing
 648  * @param enc send the encapsulated message to a peer close to the key
 649  * @param iter function to call on each result, NULL if no replies are expected
 650  * @param iter_cls closure for iter
 651  * @param timeout when to abort with an error if we fail to get
 652  *                a confirmation for the request (when necessary) or how long
 653  *                to wait for tramission to the service; only applies
 654  *                if 'iter' is NULL
 655  * @param cont continuation to call when the request has been transmitted
 656  *             the first time to the service
 657  * @param cont_cls closure for cont
 658  * @return handle to stop the request, NULL if the request is "fire and forget"
 659  */
 660 struct GNUNET_DHT_RouteHandle *
 661 GNUNET_DHT_route_start (struct GNUNET_DHT_Handle *handle,
 662                         const GNUNET_HashCode *key,
 663                         uint32_t desired_replication_level,
 664                         enum GNUNET_DHT_RouteOption options,
 665                         const struct GNUNET_MessageHeader *enc,
 666                         struct GNUNET_TIME_Relative timeout,
 667                         GNUNET_DHT_ReplyProcessor iter,
 668                         void *iter_cls,
 669                         GNUNET_SCHEDULER_Task cont,
 670                         void *cont_cls)
 671 {
 672   struct PendingMessage *pending;
 673   struct GNUNET_DHT_RouteMessage *message;
 674   struct GNUNET_DHT_RouteHandle *route_handle;
 675   uint16_t msize;
 676   uint16_t esize;
 677
 678   esize = ntohs (enc->size);
 679   if (sizeof (struct GNUNET_DHT_RouteMessage) + esize >= GNUNET_SERVER_MAX_MESSAGE_SIZE)
 680     {
 681       GNUNET_break (0);
 682       return NULL;
 683     }
 684   msize = sizeof (struct GNUNET_DHT_RouteMessage) + esize;
 685   pending = GNUNET_malloc (sizeof (struct PendingMessage) + msize);
 686   message = (struct GNUNET_DHT_RouteMessage*) &pending[1];
 687   pending->msg = &message->header;
 688   pending->handle = handle;
 689   pending->cont = cont;
 690   pending->cont_cls = cont_cls;
 691
 692   message->header.size = htons (msize);
 693   message->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_LOCAL_ROUTE);
 694   message->key = *key;
 695   message->options = htonl ((uint32_t) options);
 696   message->desired_replication_level = htonl (desired_replication_level);
 697   memcpy (&message[1], enc, esize);
 698   if (iter != NULL)
 699     {
 700       route_handle = GNUNET_malloc (sizeof (struct GNUNET_DHT_RouteHandle));
 701       route_handle->key = *key;
 702       route_handle->iter = iter;
 703       route_handle->iter_cls = iter_cls;
 704       route_handle->dht_handle = handle;
 705       route_handle->uid = handle->uid_gen++;
 706       route_handle->message = pending;
 707       message->unique_id = GNUNET_htonll (route_handle->uid);
 708       GNUNET_CONTAINER_multihashmap_put (handle->active_requests,
 709                                          key,
 710                                          route_handle,
 711                                          GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE);
 712     }
 713   else
 714     {
 715       route_handle = NULL;
 716       pending->free_on_send = GNUNET_YES;
 717       pending->timeout_task = GNUNET_SCHEDULER_add_delayed (handle->sched,
 718                                                             timeout,
 719                                                             &timeout_route_request,
 720                                                             pending);
 721     }
 722   GNUNET_CONTAINER_DLL_insert (handle->pending_head,
 723                                handle->pending_tail,
 724                                pending);
 725   pending->in_pending_queue = GNUNET_YES;
 726   process_pending_messages (handle);
 727   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 728               "DHT route start request processed, returning %p\n",
 729               route_handle);
 730   return route_handle;
 731 }
 732
 733
 734 /**
 735  * Stop a previously issued routing request
 736  *
 737  * @param route_handle handle to the request to stop
 738  */
 739 void
 740 GNUNET_DHT_route_stop (struct GNUNET_DHT_RouteHandle *route_handle)
 741 {
 742   struct GNUNET_DHT_Handle *handle;
 743   struct PendingMessage *pending;
 744   struct GNUNET_DHT_StopMessage *message;
 745   size_t msize;
 746
 747   handle = route_handle->dht_handle;
 748   if (GNUNET_NO == route_handle->message->in_pending_queue)
 749     {
 750       /* need to send stop message */
 751       msize = sizeof (struct GNUNET_DHT_StopMessage);
 752       pending = GNUNET_malloc (sizeof (struct PendingMessage) +
 753                                msize);
 754       message = (struct GNUNET_DHT_StopMessage*) &pending[1];
 755       pending->msg = &message->header;
 756       message->header.size = htons (msize);
 757       message->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_LOCAL_ROUTE_STOP);
 758       message->unique_id = GNUNET_htonll (route_handle->uid);
 759       message->key = route_handle->key;
 760       pending->handle = handle;
 761       pending->free_on_send = GNUNET_YES;
 762       pending->in_pending_queue = GNUNET_YES;
 763       GNUNET_CONTAINER_DLL_insert (handle->pending_head,
 764                                    handle->pending_tail,
 765                                    pending);
 766       process_pending_messages (handle);
 767     }
 768   else
 769     {
 770       /* simply remove pending request from message queue before
 771          transmission, no need to transmit STOP request! */
 772       GNUNET_CONTAINER_DLL_remove (handle->pending_head,
 773                                    handle->pending_tail,
 774                                    route_handle->message);
 775     }
 776   GNUNET_assert (GNUNET_YES ==
 777                  GNUNET_CONTAINER_multihashmap_remove (route_handle->dht_handle->active_requests,
 778                                                        &route_handle->key,
 779                                                        route_handle));
 780   GNUNET_free(route_handle->message);
 781   GNUNET_free(route_handle);
 782   GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
 783               "DHT route stop request processed\n");
 784 }
 785
 786
 787
 788 /* ***** Special API for controlling DHT routing maintenance ******* */
 789
 790
 791 /**
 792  * Send a control message to the DHT.
 793  *
 794  * @param handle handle to the DHT service
 795  * @param command command
 796  * @param variable variable to the command
 797  * @param cont continuation to call when done (transmitting request to service)
 798  * @param cont_cls closure for cont
 799  */
 800 static void
 801 send_control_message (struct GNUNET_DHT_Handle *handle,
 802                       uint16_t command,
 803                       uint16_t variable,
 804                       GNUNET_SCHEDULER_Task cont,
 805                       void *cont_cls)
 806 {
 807   struct GNUNET_DHT_ControlMessage *msg;
 808   struct PendingMessage *pending;
 809
 810   pending = GNUNET_malloc (sizeof (struct PendingMessage) +
 811                            sizeof(struct GNUNET_DHT_ControlMessage));
 812   msg = (struct GNUNET_DHT_ControlMessage*) &pending[1];
 813   pending->msg = &msg->header;
 814   msg->header.size = htons (sizeof(struct GNUNET_DHT_ControlMessage));
 815   msg->header.type = htons (GNUNET_MESSAGE_TYPE_DHT_CONTROL);
 816   msg->command = htons (command);
 817   msg->variable = htons (variable);
 818   pending->free_on_send = GNUNET_YES;
 819   pending->cont = cont;
 820   pending->cont_cls = cont_cls;
 821   pending->in_pending_queue = GNUNET_YES;
 822   GNUNET_CONTAINER_DLL_insert (handle->pending_head,
 823                                handle->pending_tail,
 824                                pending);
 825   process_pending_messages (handle);
 826 }
 827
 828
 829 /**
 830  * Send a message to the DHT telling it to issue a single find
 831  * peer request using the peers unique identifier as key.  This
 832  * is used to fill the routing table, and is normally controlled
 833  * by the DHT itself.  However, for testing and perhaps more
 834  * close control over the DHT, this can be explicitly managed.
 835  *
 836  * @param handle handle to the DHT service
 837  * @param cont continuation to call when done (transmitting request to service)
 838  * @param cont_cls closure for cont
 839  */
 840 void
 841 GNUNET_DHT_find_peers (struct GNUNET_DHT_Handle *handle,
 842                        GNUNET_SCHEDULER_Task cont,
 843                        void *cont_cls)
 844 {
 845   send_control_message (handle,
 846                         GNUNET_MESSAGE_TYPE_DHT_FIND_PEER, 0,
 847                         cont, cont_cls);
 848 }
 849
 850
 851
 852 #if HAVE_MALICIOUS
 853
 854 /**
 855  * Send a message to the DHT telling it to start issuing random GET
 856  * requests every 'frequency' milliseconds.
 857  *
 858  * @param handle handle to the DHT service
 859  * @param frequency delay between sending malicious messages
 860  */
 861 void
 862 GNUNET_DHT_set_malicious_getter (struct GNUNET_DHT_Handle *handle,
 863                                  struct GNUNET_TIME_Relative frequency)
 864 {
 865   if (frequency.value > UINT16_MAX)
 866     {
 867       GNUNET_break (0);
 868       return;
 869     }
 870   send_control_message (handle,
 871                         GNUNET_MESSAGE_TYPE_DHT_MALICIOUS_GET, frequency.value,
 872                         NULL, NULL);
 873 }
 874
 875 /**
 876  * Send a message to the DHT telling it to start issuing random PUT
 877  * requests every 'frequency' milliseconds.
 878  *
 879  * @param handle handle to the DHT service
 880  * @param frequency delay between sending malicious messages
 881  */
 882 void
 883 GNUNET_DHT_set_malicious_putter (struct GNUNET_DHT_Handle *handle,
 884                                  struct GNUNET_TIME_Relative frequency)
 885 {
 886   if (frequency.value > UINT16_MAX)
 887     {
 888       GNUNET_break (0);
 889       return;
 890     }
 891   send_control_message (handle,
 892                         GNUNET_MESSAGE_TYPE_DHT_MALICIOUS_PUT, frequency.value,
 893                         NULL, NULL);
 894 }
 895
 896
 897 /**
 898  * Send a message to the DHT telling it to start dropping
 899  * all requests received.
 900  *
 901  * @param handle handle to the DHT service
 902  */
 903 void
 904 GNUNET_DHT_set_malicious_dropper (struct GNUNET_DHT_Handle *handle)
 905 {
 906   send_control_message (handle,
 907                         GNUNET_MESSAGE_TYPE_DHT_MALICIOUS_DROP, 0,
 908                         NULL, NULL);
 909 }
 910
 911 #endif
 912
 913 /* end of dht_api.c */