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Date: Wed, 22 May 2019 15:24:38 -0700
From: Stanislav Fomichev <sdf@...ichev.me>
To: Roman Gushchin <guro@...com>
Cc: bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
Daniel Borkmann <daniel@...earbox.net>, netdev@...r.kernel.org,
Tejun Heo <tj@...nel.org>, kernel-team@...com,
cgroups@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next 4/4] selftests/bpf: add auto-detach test
On 05/22, Roman Gushchin wrote:
> Add a kselftest to cover bpf auto-detachment functionality.
> The test creates a cgroup, associates some resources with it,
> attaches a couple of bpf programs and deletes the cgroup.
>
> Then it checks that bpf programs are going away in 5 seconds.
>
> Expected output:
> $ ./test_cgroup_attach
> #override:PASS
> #multi:PASS
> #autodetach:PASS
> test_cgroup_attach:PASS
>
> On a kernel without auto-detaching:
> $ ./test_cgroup_attach
> #override:PASS
> #multi:PASS
> #autodetach:FAIL
> test_cgroup_attach:FAIL
>
> Signed-off-by: Roman Gushchin <guro@...com>
> ---
> .../selftests/bpf/test_cgroup_attach.c | 108 +++++++++++++++++-
> 1 file changed, 107 insertions(+), 1 deletion(-)
>
> diff --git a/tools/testing/selftests/bpf/test_cgroup_attach.c b/tools/testing/selftests/bpf/test_cgroup_attach.c
> index 93d4fe295e7d..36441fd0f392 100644
> --- a/tools/testing/selftests/bpf/test_cgroup_attach.c
> +++ b/tools/testing/selftests/bpf/test_cgroup_attach.c
> @@ -456,9 +456,115 @@ static int test_multiprog(void)
> return rc;
> }
>
> +static int test_autodetach(void)
> +{
> + __u32 prog_cnt = 4, attach_flags;
> + int allow_prog[2] = {0};
> + __u32 prog_ids[2] = {0};
> + int cg = 0, i, rc = -1;
> + void *ptr = NULL;
> + int attempts;
> +
> +
> + for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> + allow_prog[i] = prog_load_cnt(1, 1 << i);
> + if (!allow_prog[i])
> + goto err;
> + }
> +
> + if (setup_cgroup_environment())
> + goto err;
> +
> + /* create a cgroup, attach two programs and remember their ids */
> + cg = create_and_get_cgroup("/cg_autodetach");
> + if (cg < 0)
> + goto err;
> +
> + if (join_cgroup("/cg_autodetach"))
> + goto err;
> +
> + for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> + if (bpf_prog_attach(allow_prog[i], cg, BPF_CGROUP_INET_EGRESS,
> + BPF_F_ALLOW_MULTI)) {
> + log_err("Attaching prog[%d] to cg:egress", i);
> + goto err;
> + }
> + }
> +
> + /* make sure that programs are attached and run some traffic */
> + assert(bpf_prog_query(cg, BPF_CGROUP_INET_EGRESS, 0, &attach_flags,
> + prog_ids, &prog_cnt) == 0);
> + assert(system(PING_CMD) == 0);
> +
> + /* allocate some memory (4Mb) to pin the original cgroup */
> + ptr = malloc(4 * (1 << 20));
> + if (!ptr)
> + goto err;
> +
> + /* close programs and cgroup fd */
> + for (i = 0; i < ARRAY_SIZE(allow_prog); i++) {
> + close(allow_prog[i]);
> + allow_prog[i] = 0;
> + }
> +
> + close(cg);
> + cg = 0;
> +
> + /* leave the cgroup and remove it. don't detach programs */
> + cleanup_cgroup_environment();
> +
[..]
> + /* programs must stay pinned by the allocated memory */
> + for (i = 0; i < ARRAY_SIZE(prog_ids); i++) {
> + int fd = bpf_prog_get_fd_by_id(prog_ids[i]);
> +
> + if (fd < 0)
> + goto err;
> + close(fd);
> + }
This looks a bit flaky. It's essentially the same check you later
do in a for loop. I guess there is a chance that async auto-detach
might happen right after cleanup_cgroup_environment and before this for loop?
> +
> + /* wait for the asynchronous auto-detachment.
> + * wait for no more than 5 sec and give up.
> + */
> + for (i = 0; i < ARRAY_SIZE(prog_ids); i++) {
> + for (attempts = 5; attempts >= 0; attempts--) {
> + int fd = bpf_prog_get_fd_by_id(prog_ids[i]);
> +
> + if (fd < 0)
> + break;
> +
> + /* don't leave the fd open */
> + close(fd);
> +
> + if (!attempts)
> + goto err;
> +
> + sleep(1);
> + }
> + }
> +
> + rc = 0;
> +err:
> + for (i = 0; i < ARRAY_SIZE(allow_prog); i++)
> + if (allow_prog[i] > 0)
> + close(allow_prog[i]);
> + if (cg)
> + close(cg);
> + free(ptr);
> + cleanup_cgroup_environment();
> + if (!rc)
> + printf("#autodetach:PASS\n");
> + else
> + printf("#autodetach:FAIL\n");
> + return rc;
> +}
> +
> int main(int argc, char **argv)
> {
> - int (*tests[])(void) = {test_foo_bar, test_multiprog};
> + int (*tests[])(void) = {
> + test_foo_bar,
> + test_multiprog,
> + test_autodetach,
> + };
> int errors = 0;
> int i;
>
> --
> 2.20.1
>
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