[dpdk-dev] [PATCH v2] hash: fix incorrect lookup if key is all zero

[Pablo de Lara <pablo.de.lara.guarch@intel.com>]

If user has not added an all zero key in the hash table,
and tries to look it up, it results in an incorrect hit,
as dummy slot in the key table has all zero as well.

Fixes: 48a399119619 ("hash: replace with cuckoo hash implementation") 

Signed-off-by: Pablo de Lara <pablo.de.lara.guarch@intel.com>
---
Changes in v2:
- Include Fixes: tag in commit message

 doc/guides/rel_notes/release_2_2.rst |  5 +++++
 lib/librte_hash/rte_cuckoo_hash.c    | 27 +++++++++++++++++----------
 2 files changed, 22 insertions(+), 10 deletions(-)

diff --git a/doc/guides/rel_notes/release_2_2.rst b/doc/guides/rel_notes/release_2_2.rst
index 682f468..e4460f7 100644
--- a/doc/guides/rel_notes/release_2_2.rst
+++ b/doc/guides/rel_notes/release_2_2.rst
@@ -8,6 +8,11 @@ New Features
 Resolved Issues
 ---------------
 
+* **hash: Fixed incorrect lookup if key is all zero. **
+
+Fixed issue in hash library that occurred if an all zero
+key was not added in the table and the key was looked up,
+resulting in an incorrect hit.
 
 Known Issues
 ------------
diff --git a/lib/librte_hash/rte_cuckoo_hash.c b/lib/librte_hash/rte_cuckoo_hash.c
index 7019763..62d7143 100644
--- a/lib/librte_hash/rte_cuckoo_hash.c
+++ b/lib/librte_hash/rte_cuckoo_hash.c
@@ -861,15 +861,22 @@ lookup_stage2(unsigned idx, hash_sig_t prim_hash, hash_sig_t sec_hash,
 /* Lookup bulk stage 3: Check if key matches, update hit mask and return data */
 static inline void
 lookup_stage3(unsigned idx, const struct rte_hash_key *key_slot, const void * const *keys,
-		void *data[], uint64_t *hits, const struct rte_hash *h)
+		const int32_t *positions, void *data[], uint64_t *hits,
+		const struct rte_hash *h)
 {
 	unsigned hit;
+	unsigned key_idx;
 
 	hit = !h->rte_hash_cmp_eq(key_slot->key, keys[idx], h->key_len);
 	if (data != NULL)
 		data[idx] = key_slot->pdata;
 
-	*hits |= (uint64_t)(hit) << idx;
+	key_idx = positions[idx] + 1;
+	/*
+	 * If key index is 0, force hit to be 0, in case key to be looked up
+	 * is all zero (as in the dummy slot), which would result in a wrong hit
+	 */
+	*hits |= (uint64_t)(hit && !!key_idx)  << idx;
 }
 
 static inline void
@@ -961,8 +968,8 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 		lookup_stage2(idx21, primary_hash21, secondary_hash21,
 			primary_bkt21, secondary_bkt21,	&k_slot21, positions,
 			&extra_hits_mask, key_store, h);
-		lookup_stage3(idx30, k_slot30, keys, data, &hits, h);
-		lookup_stage3(idx31, k_slot31, keys, data, &hits, h);
+		lookup_stage3(idx30, k_slot30, keys, positions, data, &hits, h);
+		lookup_stage3(idx31, k_slot31, keys, positions, data, &hits, h);
 	}
 
 	k_slot30 = k_slot20, k_slot31 = k_slot21;
@@ -988,8 +995,8 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 	lookup_stage2(idx21, primary_hash21, secondary_hash21, primary_bkt21,
 		secondary_bkt21, &k_slot21, positions, &extra_hits_mask,
 		key_store, h);
-	lookup_stage3(idx30, k_slot30, keys, data, &hits, h);
-	lookup_stage3(idx31, k_slot31, keys, data, &hits, h);
+	lookup_stage3(idx30, k_slot30, keys, positions, data, &hits, h);
+	lookup_stage3(idx31, k_slot31, keys, positions, data, &hits, h);
 
 	k_slot30 = k_slot20, k_slot31 = k_slot21;
 	idx30 = idx20, idx31 = idx21;
@@ -1009,14 +1016,14 @@ __rte_hash_lookup_bulk(const struct rte_hash *h, const void **keys,
 	lookup_stage2(idx21, primary_hash21, secondary_hash21, primary_bkt21,
 		secondary_bkt21, &k_slot21, positions, &extra_hits_mask,
 		key_store, h);
-	lookup_stage3(idx30, k_slot30, keys, data, &hits, h);
-	lookup_stage3(idx31, k_slot31, keys, data, &hits, h);
+	lookup_stage3(idx30, k_slot30, keys, positions, data, &hits, h);
+	lookup_stage3(idx31, k_slot31, keys, positions, data, &hits, h);
 
 	k_slot30 = k_slot20, k_slot31 = k_slot21;
 	idx30 = idx20, idx31 = idx21;
 
-	lookup_stage3(idx30, k_slot30, keys, data, &hits, h);
-	lookup_stage3(idx31, k_slot31, keys, data, &hits, h);
+	lookup_stage3(idx30, k_slot30, keys, positions, data, &hits, h);
+	lookup_stage3(idx31, k_slot31, keys, positions, data, &hits, h);
 
 	/* ignore any items we have already found */
 	extra_hits_mask &= ~hits;
-- 
2.4.2