[PATCH] member: fix PRNG seed reset in NitroSketch mode

[Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>]

Sketch creation seeded the global PRNG
using the supplied seed for hashing.
The use of this seed by SKETCH set summary was not documented.
SKETCH set summary does not require two independent hash seeds,
unlike other set summary types.
Seeding the global PRNG at sketch creation
does not make the sketch operation deterministic:
it uses rte_rand() later, the PRNG may be seeded again by that point.
On the other hand, seeding the global PRNG with a hash seed,
is likely undesired, because it may be low-entropy or even constant.
Deterministic operation can be achieved by seeding the PRNG externally.

Remove the call to rte_srand() at sketch creation.
Document that hash seeds are not used by SKETCH set summary type.

Fixes: db354bd2e1f8 ("member: add NitroSketch mode")
Cc: leyi.rong@intel.com

Signed-off-by: Dmitry Kozlyuk <dmitry.kozliuk@gmail.com>
---
 lib/member/rte_member.h        | 1 +
 lib/member/rte_member_sketch.c | 1 -
 2 files changed, 1 insertion(+), 1 deletion(-)

diff --git a/lib/member/rte_member.h b/lib/member/rte_member.h
index 072a253c89..d08b143e51 100644
--- a/lib/member/rte_member.h
+++ b/lib/member/rte_member.h
@@ -314,6 +314,7 @@ struct rte_member_parameters {
 	 * for bucket location.
 	 * For vBF type, these two hashes and their combinations are used as
 	 * hash locations to index the bit array.
+	 * For Sketch type, these seeds are not used.
 	 */
 	uint32_t prim_hash_seed;
 
diff --git a/lib/member/rte_member_sketch.c b/lib/member/rte_member_sketch.c
index 524ba77620..d5f35aabe9 100644
--- a/lib/member/rte_member_sketch.c
+++ b/lib/member/rte_member_sketch.c
@@ -227,7 +227,6 @@ rte_member_create_sketch(struct rte_member_setsum *ss,
 		goto error_runtime;
 	}
 
-	rte_srand(ss->prim_hash_seed);
 	for (i = 0; i < ss->num_row; i++)
 		ss->hash_seeds[i] = rte_rand();
 
-- 
2.38.4