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/* Copyright (c) 2018, The Tor Project, Inc. */
/* See LICENSE for licensing information */
/**
* \file address_set.c
* \brief Implementation for a set of addresses.
*
* This module was first written on a semi-emergency basis to improve the
* robustness of the anti-DoS module. As such, it's written in a pretty
* conservative way, and should be susceptible to improvement later on.
**/
#include "orconfig.h"
#include "address_set.h"
#include "address.h"
#include "compat.h"
#include "container.h"
#include "crypto.h"
#include "util.h"
#include "siphash.h"
/** How many 64-bit siphash values to extract per address */
#define N_HASHES 2
/** How many bloom-filter bits we set per address. This is twice the N_HASHES
* value, since we split the siphash output into two 32-bit values. */
#define N_BITS_PER_ITEM (N_HASHES * 2)
/* XXXX This code is largely duplicated with digestset_t. We should merge
* them together into a common bloom-filter implementation. I'm keeping
* them separate for now, though, since this module needs to be backported
* all the way to 0.2.9.
*
* The main difference between digestset_t and this code is that we use
* independent siphashes rather than messing around with bit-shifts. The
* approach here is probably more sound, and we should prefer it if&when we
* unify the implementations.
**/
struct address_set_t {
/** siphash keys to make N_HASHES independent hashes for each address. */
struct sipkey key[N_HASHES];
int mask; /**< One less than the number of bits in <b>ba</b>; always one less
* than a power of two. */
bitarray_t *ba; /**< A bit array to implement the Bloom filter. */
};
/**
* Allocate and return an address_set, suitable for holding up to
* <b>max_address_guess</b> distinct values.
*/
address_set_t *
address_set_new(int max_addresses_guess)
{
/* See digestset_new() for rationale on this equation. */
int n_bits = 1u << (tor_log2(max_addresses_guess)+5);
address_set_t *set = tor_malloc_zero(sizeof(address_set_t));
set->mask = n_bits - 1;
set->ba = bitarray_init_zero(n_bits);
crypto_rand((char*) set->key, sizeof(set->key));
return set;
}
/**
* Release all storage associated with <b>set</b>
*/
void
address_set_free(address_set_t *set)
{
if (! set)
return;
bitarray_free(set->ba);
tor_free(set);
}
/** Yield the bit index corresponding to 'val' for set. */
#define BIT(set, val) ((val) & (set)->mask)
/**
* Add <b>addr</b> to <b>set</b>.
*
* All future queries for <b>addr</b> in set will return true. Removing
* items is not possible.
*/
void
address_set_add(address_set_t *set, const struct tor_addr_t *addr)
{
int i;
for (i = 0; i < N_HASHES; ++i) {
uint64_t h = tor_addr_keyed_hash(&set->key[i], addr);
uint32_t high_bits = (uint32_t)(h >> 32);
uint32_t low_bits = (uint32_t)(h);
bitarray_set(set->ba, BIT(set, high_bits));
bitarray_set(set->ba, BIT(set, low_bits));
}
}
/** As address_set_add(), but take an ipv4 address in host order. */
void
address_set_add_ipv4h(address_set_t *set, uint32_t addr)
{
tor_addr_t a;
tor_addr_from_ipv4h(&a, addr);
address_set_add(set, &a);
}
/**
* Return true if <b>addr</b> if a member of <b>set</b>. (And probably,
* return false if <b>addr</b> is not a member of set.)
*/
int
address_set_probably_contains(address_set_t *set,
const struct tor_addr_t *addr)
{
int i, matches = 0;
for (i = 0; i < N_HASHES; ++i) {
uint64_t h = tor_addr_keyed_hash(&set->key[i], addr);
uint32_t high_bits = (uint32_t)(h >> 32);
uint32_t low_bits = (uint32_t)(h);
// Note that !! is necessary here, since bitarray_is_set does not
// necessarily return 1 on true.
matches += !! bitarray_is_set(set->ba, BIT(set, high_bits));
matches += !! bitarray_is_set(set->ba, BIT(set, low_bits));
}
return matches == N_BITS_PER_ITEM;
}
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