selftests/bpf: No need to drop the packet when there is no geneve opt

selftests/bpf: No need to drop the packet when there is no geneve opt

commit 557c223b643a35effec9654958d8edc62fd2603a upstream.

In bpf geneve tunnel test we set geneve option on tx side. On rx side we
only call bpf_skb_get_tunnel_opt(). Since commit 9c2e14b48119 ("ip_tunnels:
Set tunnel option flag when tunnel metadata is present") geneve_rx() will
not add TUNNEL_GENEVE_OPT flag if there is no geneve option, which cause
bpf_skb_get_tunnel_opt() return ENOENT and _geneve_get_tunnel() in
test_tunnel_kern.c drop the packet.

As it should be valid that bpf_skb_get_tunnel_opt() return error when
there is not tunnel option, there is no need to drop the packet and
break all geneve rx traffic. Just set opt_class to 0 in this test and
keep returning TC_ACT_OK.

Fixes: 933a741e3b82 ("selftests/bpf: bpf tunnel test.")
Signed-off-by: Hangbin Liu <liuhangbin@gmail.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: William Tu <u9012063@gmail.com>
Link: https://lore.kernel.org/bpf/20210224081403.1425474-1-liuhangbin@gmail.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>