tc-policy: Take into account locally generated traffic

The BPF-prog "not_txq_zero" also needed to take into account
that skb->queue_mapping usually isn't set for locally
generated traffic.

I worry that sockets can set another queue id that could
override our (BPF choice) in netdev_pick_tx().
See sk_tx_queue_set() and sk_tx_queue_get().

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>

Author: netoptimizer

tc-policy/monitor_txq_usage.bt

@@ -7,7 +7,7 @@
 
 tracepoint:net:net_dev_start_xmit {
 	$qm = args->queue_mapping;
-	$dev = str(args->name, 15);
+	$dev = str(args->name, 16);
 
 	@stat_txq_usage[$dev] = lhist($qm, 0,32,1);
 }

tc-policy/tc_txq_policy_kern.c

@@ -70,5 +70,11 @@ int not_txq_zero (struct __sk_buff *skb)
 	if (skb->queue_mapping == 1)
 		skb->queue_mapping = 4;
 
+	/* If queue_mapping was not set by skb_record_rx_queue(),
+	 * e.g. locally generated traffic
+	 */
+	if (skb->queue_mapping == 0)
+		skb->queue_mapping = 3;
+
 	return TC_ACT_OK;
 }