This patch rides on an existing BPF_PROG_TYPE_CGROUP_SKB test (test_sock_fields.c) to do a TCP end-to-end test on the new bpf_sk_storage_* helpers. Signed-off-by: Martin KaFai Lau <kafai@fb.com> Signed-off-by: Alexei Starovoitov <ast@kernel.org>