tc-policy: Manuel setup steps via tc cmdline

Yocto build have a problem with loading this via tc

 # tc filter replace dev eth1 egress prio 0xC000 handle 1 bpf da obj tc_txq_policy_kern.o
 Continuing without mounted eBPF fs. Too old kernel?
 mkdir (null)/globals failed: No such file or directory
 Unable to load program

It can be worked around via mounting BPF file-system manually:

 # mount -t bpf bpf /sys/fs/bpf/

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

tc-policy/tc_txq_policy_kern.c

@@ -9,6 +9,20 @@
 //#include <stdbool.h>
 //#include "../include/xdp/parsing_helpers.h"
 
+/* Manuel setup:
+ export DEV=eth1
+
+ tc qdisc  add dev "$DEV" clsact
+ tc filter add dev "$DEV" egress bpf da obj tc_txq_policy_kern.o
+ tc filter list dev "$DEV" egress
+
+ * Quick test reloading with tc:
+ tc filter replace dev "$DEV" egress prio 0xC000 handle 1 bpf da obj tc_txq_policy_kern.o
+
+ * Delete by teardown of clsact
+ tc qdisc delete dev "$DEV" clsact
+
+*/
 SEC("classifier")
 int queue_map_4 (struct __sk_buff *skb)
 {