selftests: bpf: add check for ip XDP redirect

Kernel test robot reports error when running test_xdp_redirect.sh.
Check if ip tool supports xdpgeneric, if not, skip the test.

Signed-off-by: William Tu <[e-mail]>
Acked-by: Daniel Borkmann <[e-mail]>
Cc: John Fastabend <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

tools/testing/selftests/bpf/test_xdp_redirect.sh

···
 	ip netns del ns2 2> /dev/null
 }
 
+ip link set dev lo xdpgeneric off 2>/dev/null > /dev/null
+if [ $? -ne 0 ];then
+	echo "selftests: [SKIP] Could not run test without the ip xdpgeneric support"
+	exit 0
+fi
 set -e
 
 ip netns add ns1