bpf: use per htab salt for bucket hash
All BPF hash and LRU maps currently have a known and global seed
we feed into jhash() which is 0. This is suboptimal, thus fix it
by generating a random seed upon hashtab setup time which we can
later on feed into jhash() on lookup, update and deletions.
Fixes: 0f8e4bd8a1
("bpf: add hashtable type of eBPF maps")
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Alexei Starovoitov <ast@kernel.org>
Acked-by: Song Liu <songliubraving@fb.com>
Reviewed-by: Eduardo Valentin <eduval@amazon.com>
This commit is contained in:
parent
9b2e0388be
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c020347576
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@ -15,6 +15,7 @@
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#include <linux/jhash.h>
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#include <linux/jhash.h>
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#include <linux/filter.h>
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#include <linux/filter.h>
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#include <linux/rculist_nulls.h>
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#include <linux/rculist_nulls.h>
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#include <linux/random.h>
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#include <uapi/linux/btf.h>
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#include <uapi/linux/btf.h>
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#include "percpu_freelist.h"
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#include "percpu_freelist.h"
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#include "bpf_lru_list.h"
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#include "bpf_lru_list.h"
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@ -41,6 +42,7 @@ struct bpf_htab {
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atomic_t count; /* number of elements in this hashtable */
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atomic_t count; /* number of elements in this hashtable */
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u32 n_buckets; /* number of hash buckets */
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u32 n_buckets; /* number of hash buckets */
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u32 elem_size; /* size of each element in bytes */
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u32 elem_size; /* size of each element in bytes */
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u32 hashrnd;
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};
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};
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/* each htab element is struct htab_elem + key + value */
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/* each htab element is struct htab_elem + key + value */
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@ -371,6 +373,7 @@ static struct bpf_map *htab_map_alloc(union bpf_attr *attr)
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if (!htab->buckets)
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if (!htab->buckets)
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goto free_htab;
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goto free_htab;
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htab->hashrnd = get_random_int();
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for (i = 0; i < htab->n_buckets; i++) {
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for (i = 0; i < htab->n_buckets; i++) {
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INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
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INIT_HLIST_NULLS_HEAD(&htab->buckets[i].head, i);
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raw_spin_lock_init(&htab->buckets[i].lock);
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raw_spin_lock_init(&htab->buckets[i].lock);
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@ -402,9 +405,9 @@ free_htab:
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return ERR_PTR(err);
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return ERR_PTR(err);
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}
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}
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static inline u32 htab_map_hash(const void *key, u32 key_len)
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static inline u32 htab_map_hash(const void *key, u32 key_len, u32 hashrnd)
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{
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{
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return jhash(key, key_len, 0);
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return jhash(key, key_len, hashrnd);
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}
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}
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static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
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static inline struct bucket *__select_bucket(struct bpf_htab *htab, u32 hash)
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@ -470,7 +473,7 @@ static void *__htab_map_lookup_elem(struct bpf_map *map, void *key)
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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head = select_bucket(htab, hash);
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head = select_bucket(htab, hash);
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@ -597,7 +600,7 @@ static int htab_map_get_next_key(struct bpf_map *map, void *key, void *next_key)
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if (!key)
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if (!key)
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goto find_first_elem;
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goto find_first_elem;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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head = select_bucket(htab, hash);
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head = select_bucket(htab, hash);
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@ -824,7 +827,7 @@ static int htab_map_update_elem(struct bpf_map *map, void *key, void *value,
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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b = __select_bucket(htab, hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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head = &b->head;
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@ -880,7 +883,7 @@ static int htab_lru_map_update_elem(struct bpf_map *map, void *key, void *value,
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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b = __select_bucket(htab, hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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head = &b->head;
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@ -945,7 +948,7 @@ static int __htab_percpu_map_update_elem(struct bpf_map *map, void *key,
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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b = __select_bucket(htab, hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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head = &b->head;
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@ -998,7 +1001,7 @@ static int __htab_lru_percpu_map_update_elem(struct bpf_map *map, void *key,
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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b = __select_bucket(htab, hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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head = &b->head;
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@ -1071,7 +1074,7 @@ static int htab_map_delete_elem(struct bpf_map *map, void *key)
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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b = __select_bucket(htab, hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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head = &b->head;
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@ -1103,7 +1106,7 @@ static int htab_lru_map_delete_elem(struct bpf_map *map, void *key)
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key_size = map->key_size;
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key_size = map->key_size;
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hash = htab_map_hash(key, key_size);
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hash = htab_map_hash(key, key_size, htab->hashrnd);
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b = __select_bucket(htab, hash);
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b = __select_bucket(htab, hash);
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head = &b->head;
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head = &b->head;
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