pkt_sched: fq: change classification of control packets

[ Upstream commit 2abc2f07 ]

Initial sch_fq implementation copied code from pfifo_fast to classify
a packet as a high prio packet.

This clashes with setups using PRIO with say 7 bands, as one of the
band could be incorrectly (mis)classified by FQ.

Packets would be queued in the 'internal' queue, and no pacing ever
happen for this special queue.

Fixes: afe4fd06 ("pkt_sched: fq: Fair Queue packet scheduler")
Signed-off-by: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Stephen Hemminger <stephen@networkplumber.org>
Cc: Willem de Bruijn <willemb@google.com>
Cc: Yuchung Cheng <ycheng@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

net/sched/sch_fq.c

@@ -209,21 +209,15 @@ static void fq_gc(struct fq_sched_data *q,
 	}
 }
 
-static const u8 prio2band[TC_PRIO_MAX + 1] = {
-	1, 2, 2, 2, 1, 2, 0, 0 , 1, 1, 1, 1, 1, 1, 1, 1
-};
-
 static struct fq_flow *fq_classify(struct sk_buff *skb, struct fq_sched_data *q)
 {
 	struct rb_node **p, *parent;
 	struct sock *sk = skb->sk;
 	struct rb_root *root;
 	struct fq_flow *f;
-	int band;
 
 	/* warning: no starvation prevention... */
-	band = prio2band[skb->priority & TC_PRIO_MAX];
-	if (unlikely(band == 0))
+	if (unlikely((skb->priority & TC_PRIO_MAX) == TC_PRIO_CONTROL))
 		return &q->internal;
 
 	if (unlikely(!sk)) {