Move regex DHT integration from mesh to regex

git-svn-id: https://gnunet.org/svn/gnunet@25819 140774ce-b5e7-0310-ab8b-a85725594a96

1 files changed, 754 insertions, 0 deletions

diff --git a/src/regex/regex_dht.c b/src/regex/regex_dht.c
new file mode 100644
index 0000000000..ce9d4e2a16
--- /dev/null
+++ b/src/regex/regex_dht.c
@@ -0,0 +1,754 @@
+/*
+     This file is part of GNUnet
+     (C) 2012 Christian Grothoff (and other contributing authors)
+
+     GNUnet is free software; you can redistribute it and/or modify
+     it under the terms of the GNU General Public License as published
+     by the Free Software Foundation; either version 3, or (at your
+     option) any later version.
+
+     GNUnet is distributed in the hope that it will be useful, but
+     WITHOUT ANY WARRANTY; without even the implied warranty of
+     MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+     General Public License for more details.
+
+     You should have received a copy of the GNU General Public License
+     along with GNUnet; see the file COPYING.  If not, write to the
+     Free Software Foundation, Inc., 59 Temple Place - Suite 330,
+     Boston, MA 02111-1307, USA.
+*/
+/**
+ * @file src/regex/regex_dht.c
+ * @brief library to announce regexes in the network and match strings
+ * against published regexes.
+ * @author Bartlomiej Polot
+ */
+#include "platform.h"
+#include "gnunet_regex_lib.h"
+#include "regex_block_lib.h"
+#include "gnunet_dht_service.h"
+#include "gnunet_statistics_service.h"
+
+#define DHT_REPLICATION 5
+#define DHT_TTL         GNUNET_TIME_UNIT_HOURS
+
+struct GNUNET_REGEX_announce_handle
+{
+  /**
+   * DHT handle to use, must be initialized externally.
+   */
+  struct GNUNET_DHT_Handle *dht;
+
+  /**
+   * Regular expression.
+   */
+  const char *regex;
+
+  /**
+   * Automaton representation of the regex (expensive to build).
+   */
+  struct GNUNET_REGEX_Automaton* dfa;
+
+  /**
+   * Identity under which to announce the regex.
+   */
+  struct GNUNET_PeerIdentity *id;
+
+  /**
+   * Optional statistics handle to report usage. Can be NULL.
+   */
+  struct GNUNET_STATISTICS_Handle *stats;
+};
+
+
+/**
+ * Regex callback iterator to store own service description in the DHT.
+ *
+ * @param cls closure.
+ * @param key hash for current state.
+ * @param proof proof for current state.
+ * @param accepting GNUNET_YES if this is an accepting state, GNUNET_NO if not.
+ * @param num_edges number of edges leaving current state.
+ * @param edges edges leaving current state.
+ */
+static void
+regex_iterator (void *cls,
+                const struct GNUNET_HashCode *key,
+                const char *proof,
+                int accepting,
+                unsigned int num_edges,
+                const struct GNUNET_REGEX_Edge *edges)
+{
+  struct GNUNET_REGEX_announce_handle *h = cls;
+  struct RegexBlock *block;
+  struct RegexEdge *block_edge;
+  enum GNUNET_DHT_RouteOption opt;
+  size_t size;
+  size_t len;
+  unsigned int i;
+  unsigned int offset;
+  char *aux;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "  regex dht put for state %s\n",
+              GNUNET_h2s (key));
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "   proof: %s\n",
+              proof);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "   num edges: %u\n",
+              num_edges);
+
+  opt = GNUNET_DHT_RO_DEMULTIPLEX_EVERYWHERE;
+  if (GNUNET_YES == accepting)
+  {
+    struct RegexAccept block;
+
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "   state %s is accepting, putting own id\n",
+                GNUNET_h2s(key));
+    size = sizeof (block);
+    block.key = *key;
+    block.id = *(h->id);
+    GNUNET_STATISTICS_update (h->stats, "# regex accepting blocks stored",
+                              1, GNUNET_NO);
+    GNUNET_STATISTICS_update (h->stats, "# regex accepting block bytes stored",
+                              sizeof (block), GNUNET_NO);
+    (void)
+    GNUNET_DHT_put (h->dht, key,
+                    2, /* FIXME option */
+                    opt /* | GNUNET_DHT_RO_RECORD_ROUTE*/,
+                    GNUNET_BLOCK_TYPE_REGEX_ACCEPT,
+                    size,
+                    (char *) &block,
+                    GNUNET_TIME_relative_to_absolute (GNUNET_TIME_UNIT_HOURS), /* FIXME: expiration time should be option */
+                    GNUNET_TIME_UNIT_HOURS, /* FIXME option */
+                    NULL, NULL);
+  }
+  len = strlen(proof);
+  size = sizeof (struct RegexBlock) + len;
+  block = GNUNET_malloc (size);
+
+  block->key = *key;
+  block->n_proof = htonl (len);
+  block->n_edges = htonl (num_edges);
+  block->accepting = htonl (accepting);
+
+  /* Store the proof at the end of the block. */
+  aux = (char *) &block[1];
+  memcpy (aux, proof, len);
+  aux = &aux[len];
+
+  /* Store each edge in a variable length MeshEdge struct at the
+   * very end of the MeshRegexBlock structure.
+   */
+  for (i = 0; i < num_edges; i++)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+                "    edge %s towards %s\n",
+                edges[i].label,
+                GNUNET_h2s(&edges[i].destination));
+
+    /* aux points at the end of the last block */
+    len = strlen (edges[i].label);
+    size += sizeof (struct RegexEdge) + len;
+    // Calculate offset FIXME is this ok? use size instead?
+    offset = aux - (char *) block;
+    block = GNUNET_realloc (block, size);
+    aux = &((char *) block)[offset];
+    block_edge = (struct RegexEdge *) aux;
+    block_edge->key = edges[i].destination;
+    block_edge->n_token = htonl (len);
+    aux = (char *) &block_edge[1];
+    memcpy (aux, edges[i].label, len);
+    aux = &aux[len];
+  }
+  (void)
+  GNUNET_DHT_put(h->dht, key,
+                 DHT_REPLICATION, /* FIXME OPTION */
+                 opt,
+                 GNUNET_BLOCK_TYPE_REGEX, size,
+                 (char *) block,
+                 GNUNET_TIME_relative_to_absolute (DHT_TTL), /* FIXME: this should be an option */
+                 DHT_TTL,
+                 NULL, NULL);
+  GNUNET_STATISTICS_update (h->stats, "# regex blocks stored",
+                            1, GNUNET_NO);
+  GNUNET_STATISTICS_update (h->stats, "# regex block bytes stored",
+                            size, GNUNET_NO);
+  
+  GNUNET_free (block);
+}
+
+
+struct GNUNET_REGEX_announce_handle *
+GNUNET_REGEX_announce (struct GNUNET_DHT_Handle *dht,
+                       struct GNUNET_PeerIdentity *id,
+                       const char *regex,
+                       uint16_t compression,
+                       struct GNUNET_STATISTICS_Handle *stats)
+{
+  struct GNUNET_REGEX_announce_handle *h;
+
+  GNUNET_assert (NULL == dht);
+  h = GNUNET_malloc (sizeof (struct GNUNET_REGEX_announce_handle));
+  h->regex = regex;
+  h->dht = dht;
+  h->stats = stats;
+  h->id = id;
+  h->dfa = GNUNET_REGEX_construct_dfa (regex,
+                                       strlen (regex),
+                                       compression);
+  GNUNET_REGEX_reannounce (h);
+  return h;
+}
+
+void
+GNUNET_REGEX_reannounce (struct GNUNET_REGEX_announce_handle *h)
+{
+  GNUNET_REGEX_iterate_all_edges (h->dfa, &regex_iterator, h);
+}
+
+void
+GNUNET_REGEX_announce_cancel (struct GNUNET_REGEX_announce_handle *h)
+{
+  GNUNET_REGEX_automaton_destroy (h->dfa);
+  GNUNET_free (h);
+}
+
+
+/******************************************************************************/
+
+
+/**
+ * Struct to keep state of running searches that have consumed a part of
+ * the inital string.
+ */
+struct RegexSearchContext
+{
+    /**
+     * Part of the description already consumed by
+     * this particular search branch.
+     */
+  size_t position;
+
+    /**
+     * Information about the search.
+     */
+  struct GNUNET_REGEX_search_handle *info;
+
+    /**
+     * We just want to look for one edge, the longer the better.
+     * Keep its length.
+     */
+  unsigned int longest_match;
+
+    /**
+     * Destination hash of the longest match.
+     */
+  struct GNUNET_HashCode hash;
+};
+
+
+/**
+ * Struct to keep information of searches of services described by a regex
+ * using a user-provided string service description.
+ */
+struct GNUNET_REGEX_search_handle
+{
+    /**
+     * DHT handle to use, must be initialized externally.
+     */
+  struct GNUNET_DHT_Handle *dht;
+
+    /**
+     * Optional statistics handle to report usage. Can be NULL.
+     */
+  struct GNUNET_STATISTICS_Handle *stats;
+
+    /**
+     * User provided description of the searched service.
+     */
+  char *description;
+
+    /**
+     * Running DHT GETs.
+     */
+  struct GNUNET_CONTAINER_MultiHashMap *dht_get_handles;
+
+    /**
+     * Results from running DHT GETs.
+     */
+  struct GNUNET_CONTAINER_MultiHashMap *dht_get_results;
+
+    /**
+     * Contexts, for each running DHT GET. Free all on end of search.
+     */
+  struct RegexSearchContext **contexts;
+
+    /**
+     * Number of contexts (branches/steps in search).
+     */
+  unsigned int n_contexts;
+  
+  /**
+   * @param callback Callback for found peers.
+   */
+  GNUNET_REGEX_Found callback;
+
+  /**
+   * @param callback_cls Closure for @c callback.
+   */
+  void *callback_cls;
+};
+
+
+
+/**
+ * Jump to the next edge, with the longest matching token.
+ *
+ * @param block Block found in the DHT.
+ * @param size Size of the block.
+ * @param ctx Context of the search.
+ *
+ * @return GNUNET_YES if should keep iterating, GNUNET_NO otherwise.
+ */
+static void
+regex_next_edge (const struct RegexBlock *block,
+                 size_t size,
+                 struct RegexSearchContext *ctx);
+
+
+/**
+ * Function to process DHT string to regex matching.
+ * Called on each result obtained for the DHT search.
+ *
+ * @param cls Closure (search context).
+ * @param exp When will this value expire.
+ * @param key Key of the result.
+ * @param get_path Path of the get request.
+ * @param get_path_length Lenght of get_path.
+ * @param put_path Path of the put request.
+ * @param put_path_length Length of the put_path.
+ * @param type Type of the result.
+ * @param size Number of bytes in data.
+ * @param data Pointer to the result data.
+ */
+static void
+dht_get_string_accept_handler (void *cls, struct GNUNET_TIME_Absolute exp,
+                               const struct GNUNET_HashCode * key,
+                               const struct GNUNET_PeerIdentity *get_path,
+                               unsigned int get_path_length,
+                               const struct GNUNET_PeerIdentity *put_path,
+                               unsigned int put_path_length,
+                               enum GNUNET_BLOCK_Type type,
+                               size_t size, const void *data)
+{
+  const struct RegexAccept *block = data;
+  struct RegexSearchContext *ctx = cls;
+  struct GNUNET_REGEX_search_handle *info = ctx->info;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Got regex results from DHT!\n");
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "  for %s\n", info->description);
+
+  GNUNET_STATISTICS_update (info->stats, "# regex accepting blocks found",
+                            1, GNUNET_NO);
+  GNUNET_STATISTICS_update (info->stats, "# regex accepting block bytes found",
+                            size, GNUNET_NO);
+
+  info->callback (info->callback_cls,
+                  &block->id,
+                  get_path, get_path_length,
+                  put_path, put_path_length);
+
+  return;
+}
+
+/**
+ * Find a path to a peer that offers a regex servcie compatible
+ * with a given string.
+ * 
+ * @param key The key of the accepting state.
+ * @param ctx Context containing info about the string, tunnel, etc.
+ */
+static void
+regex_find_path (const struct GNUNET_HashCode *key,
+                 struct RegexSearchContext *ctx)
+{
+  struct GNUNET_DHT_GetHandle *get_h;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "Found peer by service\n");
+  get_h = GNUNET_DHT_get_start (ctx->info->dht,    /* handle */
+                                GNUNET_BLOCK_TYPE_REGEX_ACCEPT, /* type */
+                                key,     /* key to search */
+                                DHT_REPLICATION, /* replication level */
+                                GNUNET_DHT_RO_DEMULTIPLEX_EVERYWHERE |
+                                GNUNET_DHT_RO_RECORD_ROUTE,
+                                NULL,       /* xquery */ // FIXME BLOOMFILTER
+                                0,     /* xquery bits */ // FIXME BLOOMFILTER SIZE
+                                &dht_get_string_accept_handler, ctx);
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_put(ctx->info->dht_get_handles,
+                                                  key,
+                                                  get_h,
+                                                  GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
+}
+
+
+/**
+ * Function to process DHT string to regex matching.
+ * Called on each result obtained for the DHT search.
+ *
+ * @param cls closure (search context)
+ * @param exp when will this value expire
+ * @param key key of the result
+ * @param get_path path of the get request (not used)
+ * @param get_path_length lenght of get_path (not used)
+ * @param put_path path of the put request (not used)
+ * @param put_path_length length of the put_path (not used)
+ * @param type type of the result
+ * @param size number of bytes in data
+ * @param data pointer to the result data
+ *
+ * TODO: re-issue the request after certain time? cancel after X results?
+ */
+static void
+dht_get_string_handler (void *cls, struct GNUNET_TIME_Absolute exp,
+                        const struct GNUNET_HashCode * key,
+                        const struct GNUNET_PeerIdentity *get_path,
+                        unsigned int get_path_length,
+                        const struct GNUNET_PeerIdentity *put_path,
+                        unsigned int put_path_length,
+                        enum GNUNET_BLOCK_Type type,
+                        size_t size, const void *data)
+{
+  const struct RegexBlock *block = data;
+  struct RegexSearchContext *ctx = cls;
+  struct GNUNET_REGEX_search_handle *info = ctx->info;
+  void *copy;
+  size_t len;
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "DHT GET STRING RETURNED RESULTS\n");
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG,
+              "  key: %s\n", GNUNET_h2s (key));
+
+  copy = GNUNET_malloc (size);
+  memcpy (copy, data, size);
+  GNUNET_break (GNUNET_OK ==
+                GNUNET_CONTAINER_multihashmap_put(info->dht_get_results, key, copy,
+                                                  GNUNET_CONTAINER_MULTIHASHMAPOPTION_MULTIPLE));
+  len = ntohl (block->n_proof);
+  {
+    char proof[len + 1];
+
+    memcpy (proof, &block[1], len);
+    proof[len] = '\0';
+    if (GNUNET_OK != GNUNET_REGEX_check_proof (proof, key))
+    {
+      GNUNET_break_op (0);
+      return;
+    }
+  }
+  len = strlen (info->description);
+  if (len == ctx->position) // String processed
+  {
+    if (GNUNET_YES == ntohl (block->accepting))
+    {
+      regex_find_path(key, ctx);
+    }
+    else
+    {
+      GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "  block not accepting!\n");
+      // FIXME REGEX this block not successful, wait for more? start timeout?
+    }
+    return;
+  }
+
+  regex_next_edge (block, size, ctx);
+
+  return;
+}
+
+
+/**
+ * Iterator over found existing mesh regex blocks that match an ongoing search.
+ *
+ * @param cls closure
+ * @param key current key code
+ * @param value value in the hash map
+ * @return GNUNET_YES if we should continue to iterate,
+ *         GNUNET_NO if not.
+ */
+static int
+regex_result_iterator (void *cls,
+                       const struct GNUNET_HashCode * key,
+                       void *value)
+{
+  struct RegexBlock *block = value;
+  struct RegexSearchContext *ctx = cls;
+
+  if (GNUNET_YES == ntohl(block->accepting) &&
+      ctx->position == strlen (ctx->info->description))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "* Found accepting known block\n");
+    regex_find_path (key, ctx);
+    return GNUNET_YES; // We found an accept state!
+  }
+  else
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "* %u, %u, [%u]\n",
+                ctx->position, strlen(ctx->info->description),
+                ntohl(block->accepting));
+
+  }
+  regex_next_edge(block, SIZE_MAX, ctx);
+
+  GNUNET_STATISTICS_update (ctx->info->stats, "# regex mesh blocks iterated",
+                            1, GNUNET_NO);
+
+  return GNUNET_YES;
+}
+
+
+/**
+ * Iterator over edges in a regex block retrieved from the DHT.
+ *
+ * @param cls Closure (context of the search).
+ * @param token Token that follows to next state.
+ * @param len Lenght of token.
+ * @param key Hash of next state.
+ *
+ * @return GNUNET_YES if should keep iterating, GNUNET_NO otherwise.
+ */
+static int
+regex_edge_iterator (void *cls,
+                     const char *token,
+                     size_t len,
+                     const struct GNUNET_HashCode *key)
+{
+  struct RegexSearchContext *ctx = cls;
+  struct GNUNET_REGEX_search_handle *info = ctx->info;
+  const char *current;
+  size_t current_len;
+
+  GNUNET_STATISTICS_update (info->stats, "# regex edges iterated",
+                            1, GNUNET_NO);
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*    Start of regex edge iterator\n");
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     descr : %s\n", info->description);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     posit : %u\n", ctx->position);
+  current = &info->description[ctx->position];
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     currt : %s\n", current);
+  current_len = strlen (info->description) - ctx->position;
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     ctlen : %u\n", current_len);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     tklen : %u\n", len);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     token : %.*s\n", len, token);
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     nextk : %s\n", GNUNET_h2s(key));
+  if (len > current_len)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     Token too long, END\n");
+    return GNUNET_YES; // Token too long, wont match
+  }
+  if (0 != strncmp (current, token, len))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     Token doesn't match, END\n");
+    return GNUNET_YES; // Token doesn't match
+  }
+
+  if (len > ctx->longest_match)
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     Token is longer, KEEP\n");
+    ctx->longest_match = len;
+    ctx->hash = *key;
+  }
+  else
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     Token is not longer, IGNORE\n");
+  }
+
+  GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*    End of regex edge iterator\n");
+  return GNUNET_YES;
+}
+
+
+/**
+ * Jump to the next edge, with the longest matching token.
+ *
+ * @param block Block found in the DHT.
+ * @param size Size of the block.
+ * @param ctx Context of the search.
+ *
+ * @return GNUNET_YES if should keep iterating, GNUNET_NO otherwise.
+ */
+static void
+regex_next_edge (const struct RegexBlock *block,
+                 size_t size,
+                 struct RegexSearchContext *ctx)
+{
+  struct RegexSearchContext *new_ctx;
+  struct GNUNET_REGEX_search_handle *info = ctx->info;
+  struct GNUNET_DHT_GetHandle *get_h;
+  const char *rest;
+  int result;
+
+  /* Find the longest match for the current string position, 
+   * among tokens in the given block */
+  ctx->longest_match = 0;
+  result = GNUNET_REGEX_block_iterate (block, size,
+                                       &regex_edge_iterator, ctx);
+  GNUNET_break (GNUNET_OK == result);
+
+  /* Did anything match? */
+  if (0 == ctx->longest_match)
+    return;
+
+  new_ctx = GNUNET_malloc (sizeof (struct RegexSearchContext));
+  new_ctx->info = info;
+  new_ctx->position = ctx->position + ctx->longest_match;
+  GNUNET_array_append (info->contexts, info->n_contexts, new_ctx);
+
+  /* Check whether we already have a DHT GET running for it */
+  if (GNUNET_YES ==
+      GNUNET_CONTAINER_multihashmap_contains(info->dht_get_handles, &ctx->hash))
+  {
+    GNUNET_log (GNUNET_ERROR_TYPE_DEBUG, "*     GET running, END\n");
+    GNUNET_CONTAINER_multihashmap_get_multiple (info->dht_get_results,
+                                                &ctx->hash,
+                                                &regex_result_iterator,
+                                                new_ctx);
+    // FIXME: "leaks" new_ctx? avoid keeping it around?
+    return; // We are already looking for it
+  }
+
+  GNUNET_STATISTICS_update (info->stats, "# regex nodes traversed",
+                            1, GNUNET_NO);
+
+  /* Start search in DHT */
+  rest = &new_ctx->info->description[new_ctx->position];
+  get_h = 
+      GNUNET_DHT_get_start (info->dht,    /* handle */
+                            GNUNET_BLOCK_TYPE_REGEX, /* type */
+                            &ctx->hash,     /* key to search */
+                            DHT_REPLICATION, /* replication level */
+                            GNUNET_DHT_RO_DEMULTIPLEX_EVERYWHERE,
+                            rest, /* xquery */
+                            // FIXME add BLOOMFILTER to exclude filtered peers
+                            strlen(rest) + 1,     /* xquery bits */
+                            // FIXME add BLOOMFILTER SIZE
+                            &dht_get_string_handler, new_ctx);
+  if (GNUNET_OK !=
+      GNUNET_CONTAINER_multihashmap_put(info->dht_get_handles,
+                                        &ctx->hash,
+                                        get_h,
+                                        GNUNET_CONTAINER_MULTIHASHMAPOPTION_UNIQUE_FAST))
+  {
+    GNUNET_break (0);
+    return;
+  }
+}
+
+
+struct GNUNET_REGEX_search_handle *
+GNUNET_REGEX_search (struct GNUNET_DHT_Handle *dht,
+                     const char *string,
+                     GNUNET_REGEX_Found callback,
+                     void *callback_cls,
+                     struct GNUNET_STATISTICS_Handle *stats)
+{
+  struct GNUNET_REGEX_search_handle *h;
+
+  GNUNET_assert (NULL == dht);
+  h = GNUNET_malloc (sizeof (struct GNUNET_REGEX_search_handle));
+  h->dht = dht;
+  h->description = GNUNET_strdup (string);
+  h->callback = callback;
+  h->callback_cls = callback_cls;
+  h->stats = stats;
+  
+  h->dht_get_handles = GNUNET_CONTAINER_multihashmap_create (32, GNUNET_YES);
+  h->dht_get_results = GNUNET_CONTAINER_multihashmap_create (32, GNUNET_YES);
+  return h;
+}
+
+
+/**
+ * Iterator over hash map entries to cancel DHT GET requests after a
+ * successful connect_by_string.
+ *
+ * @param cls Closure (unused).
+ * @param key Current key code (unused).
+ * @param value Value in the hash map (get handle).
+ * @return GNUNET_YES if we should continue to iterate,
+ *         GNUNET_NO if not.
+ */
+static int
+regex_cancel_dht_get (void *cls,
+                      const struct GNUNET_HashCode * key,
+                      void *value)
+{
+  struct GNUNET_DHT_GetHandle *h = value;
+
+  GNUNET_DHT_get_stop (h);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Iterator over hash map entries to free MeshRegexBlocks stored during the
+ * search for connect_by_string.
+ *
+ * @param cls Closure (unused).
+ * @param key Current key code (unused).
+ * @param value MeshRegexBlock in the hash map.
+ * @return GNUNET_YES if we should continue to iterate,
+ *         GNUNET_NO if not.
+ */
+static int
+regex_free_result (void *cls,
+                   const struct GNUNET_HashCode * key,
+                   void *value)
+{
+
+  GNUNET_free (value);
+  return GNUNET_YES;
+}
+
+
+/**
+ * Cancel an ongoing regex search in the DHT and free all resources.
+ *
+ * @param ctx The search context.
+ */
+static void
+regex_cancel_search (struct GNUNET_REGEX_search_handle *ctx)
+{
+  GNUNET_free (ctx->description);
+  GNUNET_CONTAINER_multihashmap_iterate (ctx->dht_get_handles,
+                                         &regex_cancel_dht_get, NULL);
+  GNUNET_CONTAINER_multihashmap_iterate (ctx->dht_get_results,
+                                         &regex_free_result, NULL);
+  GNUNET_CONTAINER_multihashmap_destroy (ctx->dht_get_results);
+  GNUNET_CONTAINER_multihashmap_destroy (ctx->dht_get_handles);
+  if (0 < ctx->n_contexts)
+  {
+    int i;
+
+    for (i = 0; i < ctx->n_contexts; i++)
+    {
+      GNUNET_free (ctx->contexts[i]);
+    }
+    GNUNET_free (ctx->contexts);
+  }
+}
+
+void
+GNUNET_REGEX_search_cancel (struct GNUNET_REGEX_search_handle *h)
+{
+  regex_cancel_search (h);
+  GNUNET_free (h);
+}
+
+
+
+/* end of regex_dht.c */
\ No newline at end of file