selftests/bpf: Add test for detachment on empty mprog entry

Add a detachment test case with miniq present to assert that with and
without the miniq we get the same error.

  # ./test_progs -t tc_opts
  #244     tc_opts_after:OK
  #245     tc_opts_append:OK
  #246     tc_opts_basic:OK
  #247     tc_opts_before:OK
  #248     tc_opts_chain_classic:OK
  #249     tc_opts_delete_empty:OK
  #250     tc_opts_demixed:OK
  #251     tc_opts_detach:OK
  #252     tc_opts_detach_after:OK
  #253     tc_opts_detach_before:OK
  #254     tc_opts_dev_cleanup:OK
  #255     tc_opts_invalid:OK
  #256     tc_opts_mixed:OK
  #257     tc_opts_prepend:OK
  #258     tc_opts_replace:OK
  #259     tc_opts_revision:OK
  Summary: 16/0 PASSED, 0 SKIPPED, 0 FAILED

Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>

tools/testing/selftests/bpf/prog_tests/tc_opts.c

@@ -2237,3 +2237,34 @@ void serial_test_tc_opts_detach_after(void)
 	test_tc_opts_detach_after_target(BPF_TCX_INGRESS);
 	test_tc_opts_detach_after_target(BPF_TCX_EGRESS);
 }
+
+static void test_tc_opts_delete_empty(int target, bool chain_tc_old)
+{
+	LIBBPF_OPTS(bpf_tc_hook, tc_hook, .ifindex = loopback);
+	LIBBPF_OPTS(bpf_prog_detach_opts, optd);
+	int err;
+
+	assert_mprog_count(target, 0);
+	if (chain_tc_old) {
+		tc_hook.attach_point = target == BPF_TCX_INGRESS ?
+				       BPF_TC_INGRESS : BPF_TC_EGRESS;
+		err = bpf_tc_hook_create(&tc_hook);
+		ASSERT_OK(err, "bpf_tc_hook_create");
+		__assert_mprog_count(target, 0, true, loopback);
+	}
+	err = bpf_prog_detach_opts(0, loopback, target, &optd);
+	ASSERT_EQ(err, -ENOENT, "prog_detach");
+	if (chain_tc_old) {
+		tc_hook.attach_point = BPF_TC_INGRESS | BPF_TC_EGRESS;
+		bpf_tc_hook_destroy(&tc_hook);
+	}
+	assert_mprog_count(target, 0);
+}
+
+void serial_test_tc_opts_delete_empty(void)
+{
+	test_tc_opts_delete_empty(BPF_TCX_INGRESS, false);
+	test_tc_opts_delete_empty(BPF_TCX_EGRESS, false);
+	test_tc_opts_delete_empty(BPF_TCX_INGRESS, true);
+	test_tc_opts_delete_empty(BPF_TCX_EGRESS, true);
+}