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3 Copyright (C) 2017 GNUnet e.V.
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13 Affero General Public License for more details.
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20 * @brief implementation of a block group using a Bloom filter
21 * to drop duplicate blocks
22 * @author Christian Grothoff
25 #include "gnunet_util_lib.h"
26 #include "gnunet_block_group_lib.h"
27 #include "gnunet_block_plugin.h"
31 * Internal data structure for a block group.
33 struct BfGroupInternals
36 * A Bloom filter to weed out duplicate replies probabilistically.
38 struct GNUNET_CONTAINER_BloomFilter *bf;
41 * Set from the nonce to mingle the hashes before going into the @e bf.
54 * Serialize state of a block group.
56 * @param bg group to serialize
57 * @param[out] nonce set to the nonce of the @a bg
58 * @param[out] raw_data set to the serialized state
59 * @param[out] raw_data_size set to the number of bytes in @a raw_data
60 * @return #GNUNET_OK on success, #GNUNET_NO if serialization is not
61 * supported, #GNUNET_SYSERR on error
64 bf_group_serialize_cb (struct GNUNET_BLOCK_Group *bg,
67 size_t *raw_data_size)
69 struct BfGroupInternals *gi = bg->internal_cls;
72 raw = GNUNET_malloc (gi->bf_size);
74 GNUNET_CONTAINER_bloomfilter_get_raw_data (gi->bf,
82 *nonce = gi->bf_mutator;
84 *raw_data_size = gi->bf_size;
90 * Mark elements as "seen" using a hash of the element. Not supported
91 * by all block plugins.
93 * @param bg group to update
94 * @param seen_results results already seen
95 * @param seen_results_count number of entries in @a seen_results
98 bf_group_mark_seen_cb (struct GNUNET_BLOCK_Group *bg,
99 const struct GNUNET_HashCode *seen_results,
100 unsigned int seen_results_count)
102 struct BfGroupInternals *gi = bg->internal_cls;
104 for (unsigned int i=0;i<seen_results_count;i++)
106 struct GNUNET_HashCode mhash;
108 GNUNET_BLOCK_mingle_hash (&seen_results[i],
111 GNUNET_CONTAINER_bloomfilter_add (gi->bf,
118 * Merge two groups, if possible. Not supported by all block plugins,
119 * can also fail if the nonces were different.
121 * @param bg1 group to update
122 * @param bg2 group to merge into @a bg1
123 * @return #GNUNET_OK on success, #GNUNET_NO if the nonces were different and thus
127 bf_group_merge_cb (struct GNUNET_BLOCK_Group *bg1,
128 const struct GNUNET_BLOCK_Group *bg2)
130 struct BfGroupInternals *gi1 = bg1->internal_cls;
131 struct BfGroupInternals *gi2 = bg2->internal_cls;
133 if (gi1->bf_mutator != gi2->bf_mutator)
135 if (gi1->bf_size != gi2->bf_size)
137 GNUNET_CONTAINER_bloomfilter_or2 (gi1->bf,
144 * Destroy resources used by a block group.
146 * @param bg group to destroy, NULL is allowed
149 bf_group_destroy_cb (struct GNUNET_BLOCK_Group *bg)
151 struct BfGroupInternals *gi = bg->internal_cls;
153 GNUNET_CONTAINER_bloomfilter_free (gi->bf);
160 * Create a new block group that filters duplicates using a Bloom filter.
162 * @param ctx block context in which the block group is created
163 * @param bf_size size of the Bloom filter
164 * @param bf_k K-value for the Bloom filter
165 * @param type block type
166 * @param nonce random value used to seed the group creation
167 * @param raw_data optional serialized prior state of the group, NULL if unavailable/fresh
168 * @param raw_data_size number of bytes in @a raw_data, 0 if unavailable/fresh
169 * @return block group handle, NULL if block groups are not supported
170 * by this @a type of block (this is not an error)
172 struct GNUNET_BLOCK_Group *
173 GNUNET_BLOCK_GROUP_bf_create (void *cls,
176 enum GNUNET_BLOCK_Type type,
178 const void *raw_data,
179 size_t raw_data_size)
181 struct BfGroupInternals *gi;
182 struct GNUNET_BLOCK_Group *bg;
184 gi = GNUNET_new (struct BfGroupInternals);
185 gi->bf = GNUNET_CONTAINER_bloomfilter_init ((bf_size != raw_data_size) ? NULL : raw_data,
188 gi->bf_mutator = nonce;
189 gi->bf_size = bf_size;
190 bg = GNUNET_new (struct GNUNET_BLOCK_Group);
192 bg->serialize_cb = &bf_group_serialize_cb;
193 bg->mark_seen_cb = &bf_group_mark_seen_cb;
194 bg->merge_cb = &bf_group_merge_cb;
195 bg->destroy_cb = &bf_group_destroy_cb;
196 bg->internal_cls = gi;
202 * Test if @a hc is contained in the Bloom filter of @a bg. If so,
203 * return #GNUNET_YES. If not, add @a hc to the Bloom filter and
206 * @param bg block group to use for testing
207 * @param hc hash of element to evaluate
208 * @return #GNUNET_YES if @a hc is (likely) a duplicate
209 * #GNUNET_NO if @a hc was definitively not in @bg (but now is)
212 GNUNET_BLOCK_GROUP_bf_test_and_set (struct GNUNET_BLOCK_Group *bg,
213 const struct GNUNET_HashCode *hc)
215 struct BfGroupInternals *gi;
216 struct GNUNET_HashCode mhash;
220 gi = bg->internal_cls;
221 GNUNET_BLOCK_mingle_hash (hc,
225 GNUNET_CONTAINER_bloomfilter_test (gi->bf,
228 GNUNET_CONTAINER_bloomfilter_add (gi->bf,
235 * How many bytes should a bloomfilter be if we have already seen
236 * entry_count responses? Sized so that do not have to
237 * re-size the filter too often (to keep it cheap).
239 * Since other peers will also add entries but not resize the filter,
240 * we should generally pick a slightly larger size than what the
241 * strict math would suggest.
243 * @param entry_count expected number of entries in the Bloom filter
244 * @param k number of bits set per entry
245 * @return must be a power of two and smaller or equal to 2^15.
248 GNUNET_BLOCK_GROUP_compute_bloomfilter_size (unsigned int entry_count,
252 unsigned int ideal = (entry_count * k) / 4;
253 uint16_t max = 1 << 15;
255 if (entry_count > max)
258 while ((size < max) && (size < ideal))