selftests/bpf: Add tracing tests for walking skb and req.

Add tracing tests for walking skb->sk and req->sk.
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Signed-off-by: Andrii Nakryiko <andrii@kernel.org>
Acked-by: David Vernet <void@manifault.com>
Link: https://lore.kernel.org/bpf/20230404045029.82870-9-alexei.starovoitov@gmail.com

tools/testing/selftests/bpf/progs/test_sk_storage_tracing.c

@@ -92,4 +92,20 @@ int BPF_PROG(inet_csk_accept, struct sock *sk, int flags, int *err, bool kern,
 	return 0;
 }
 
+SEC("tp_btf/tcp_retransmit_synack")
+int BPF_PROG(tcp_retransmit_synack, struct sock* sk, struct request_sock* req)
+{
+	/* load only test */
+	bpf_sk_storage_get(&sk_stg_map, sk, 0, 0);
+	bpf_sk_storage_get(&sk_stg_map, req->sk, 0, 0);
+	return 0;
+}
+
+SEC("tp_btf/tcp_bad_csum")
+int BPF_PROG(tcp_bad_csum, struct sk_buff* skb)
+{
+	bpf_sk_storage_get(&sk_stg_map, skb->sk, 0, 0);
+	return 0;
+}
+
 char _license[] SEC("license") = "GPL";