net/fq_impl: use skb_get_hash instead of skb_get_hash_perturb

This avoids unnecessarily regenerating the skb flow hash
Signed-off-by: Felix Fietkau <nbd@nbd.name>
Link: https://lore.kernel.org/r/20200726130947.88145-1-nbd@nbd.name
[small commit message fixup]
Signed-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/fq.h

@@ -69,7 +69,6 @@ struct fq {
 	struct list_head backlogs;
 	spinlock_t lock;
 	u32 flows_cnt;
-	siphash_key_t	perturbation;
 	u32 limit;
 	u32 memory_limit;
 	u32 memory_usage;

include/net/fq_impl.h

@@ -108,7 +108,7 @@ static struct sk_buff *fq_tin_dequeue(struct fq *fq,
 
 static u32 fq_flow_idx(struct fq *fq, struct sk_buff *skb)
 {
-	u32 hash = skb_get_hash_perturb(skb, &fq->perturbation);
+	u32 hash = skb_get_hash(skb);
 
 	return reciprocal_scale(hash, fq->flows_cnt);
 }
@@ -308,7 +308,6 @@ static int fq_init(struct fq *fq, int flows_cnt)
 	INIT_LIST_HEAD(&fq->backlogs);
 	spin_lock_init(&fq->lock);
 	fq->flows_cnt = max_t(u32, flows_cnt, 1);
-	get_random_bytes(&fq->perturbation, sizeof(fq->perturbation));
 	fq->quantum = 300;
 	fq->limit = 8192;
 	fq->memory_limit = 16 << 20; /* 16 MBytes */