Subject: Re: [PATCH bpf-next v2 2/2] bpf, selftests: Add test case for cgroup skb to get net_cls classid helpers

From: Martin KaFai Lau <[email-masked]>
Date: Mon, 30 Sep 2024 18:58:03 -0700

On 9/18/24 12:45 AM, Feng zhou wrote:
> From: Feng Zhou <[email-masked]>
> 
> This patch adds a test for cgroup skb to get classid.
> 
> Signed-off-by: Feng Zhou <[email-masked]>
> ---
>   .../bpf/prog_tests/cg_skb_get_classid.c       | 87 +++++++++++++++++++
>   .../selftests/bpf/progs/cg_skb_get_classid.c  | 19 ++++
>   2 files changed, 106 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c
>   create mode 100644 tools/testing/selftests/bpf/progs/cg_skb_get_classid.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c b/tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c
> new file mode 100644
> index 000000000000..13a5943c387d
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/cg_skb_get_classid.c
> @@ -0,0 +1,87 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +
> +/*
> + * Copyright 2024 Bytedance.
> + */
> +
> +#include <test_progs.h>
> +
> +#include "cg_skb_get_classid.skel.h"
> +
> +#include "cgroup_helpers.h"
> +#include "network_helpers.h"
> +
> +static int run_test(int cgroup_fd, int server_fd)
> +{
> +	struct cg_skb_get_classid *skel;
> +	int fd, err = 0;
> +
> +	skel = cg_skb_get_classid__open_and_load();
> +	if (!ASSERT_OK_PTR(skel, "skel_open"))
> +		return -1;
> +
> +	skel->links.cg_skb_classid =
> +		bpf_program__attach_cgroup(skel->progs.cg_skb_classid,
> +					   cgroup_fd);
> +	if (!ASSERT_OK_PTR(skel->links.cg_skb_classid, "prog_attach")) {
> +		err = -1;
> +		goto out;
> +	}
> +
> +	if (!ASSERT_OK(join_classid(), "join_classid")) {
> +		err = -1;
> +		goto out;
> +	}
> +
> +	errno = 0;
> +	fd = connect_to_fd_opts(server_fd, NULL);
> +	if (fd >= 0) {
> +		if (skel->bss->classid != getpid()) {
> +			log_err("Get unexpected classid");
> +			err = -1;
> +		}
> +
> +		close(fd);
> +	} else {
> +		log_err("Unexpected errno from connect to server");
> +		err = -1;
> +	}
> +out:
> +	cg_skb_get_classid__destroy(skel);
> +	return err;
> +}
> +
> +void test_cg_skb_get_classid(void)
> +{
> +	struct network_helper_opts opts = {};
> +	int server_fd, client_fd, cgroup_fd;
> +	static const int port = 60120;

Running a test with a specific port without netns could fail when test_progs is 
run in parallel (-j). e.g. cgroup_v1v2 is using the same port.

> +
> +	/* Step 1: Check base connectivity works without any BPF. */
> +	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, port, 0);
> +	if (!ASSERT_GE(server_fd, 0, "server_fd"))
> +		return;
> +	client_fd = connect_to_fd_opts(server_fd, &opts);
> +	if (!ASSERT_GE(client_fd, 0, "client_fd")) {
> +		close(server_fd);
> +		return;
> +	}
> +	close(client_fd);
> +	close(server_fd);

imo, this connection pre-test is unnecessary. I would remove it.

> +
> +	/* Step 2: Check BPF prog attached to cgroups. */
> +	cgroup_fd = test__join_cgroup("/cg_skb_get_classid");
> +	if (!ASSERT_GE(cgroup_fd, 0, "cgroup_fd"))
> +		return;
> +	server_fd = start_server(AF_INET, SOCK_STREAM, NULL, port, 0);
> +	if (!ASSERT_GE(server_fd, 0, "server_fd")) {
> +		close(cgroup_fd);
> +		return;
> +	}
> +	setup_classid_environment();
> +	set_classid();
> +	ASSERT_OK(run_test(cgroup_fd, server_fd), "cg_skb_get_classid");

Please run this test under a netns and without specifying a particular port. 
connect_to_fd_opts will figure out the port used in server_fd.

Patch 1 lgtm.

Please add a few words to the cover letter also.

pw-bot: cr