Re: [bpf-next PATCH v3 5/5] bpf: selftests, test probe_* helpers from SCHED_CLS

[Yonghong Song <yhs@fb.com>]

On 5/21/20 7:36 AM, John Fastabend wrote:
> Lets test using probe* in SCHED_CLS network programs as well just
> to be sure these keep working. Its cheap to add the extra test
> and provides a second context to test outside of sk_msg after
> we generalized probe* helpers to all networking types.
> 
> Signed-off-by: John Fastabend <john.fastabend@gmail.com>

Ack with a minor nit below.

Acked-by: Yonghong Song <yhs@fb.com>

> ---
>   .../testing/selftests/bpf/prog_tests/skb_helpers.c |   30 ++++++++++++++++++
>   .../testing/selftests/bpf/progs/test_skb_helpers.c |   33 ++++++++++++++++++++
>   2 files changed, 63 insertions(+)
>   create mode 100644 tools/testing/selftests/bpf/prog_tests/skb_helpers.c
>   create mode 100644 tools/testing/selftests/bpf/progs/test_skb_helpers.c
> 
> diff --git a/tools/testing/selftests/bpf/prog_tests/skb_helpers.c b/tools/testing/selftests/bpf/prog_tests/skb_helpers.c
> new file mode 100644
> index 0000000..5a865c4
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/skb_helpers.c
> @@ -0,0 +1,30 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <test_progs.h>
> +#include <network_helpers.h>
> +
> +void test_skb_helpers(void)
> +{
> +	struct __sk_buff skb = {
> +		.wire_len = 100,
> +		.gso_segs = 8,
> +		.gso_size = 10,
> +	};
> +	struct bpf_prog_test_run_attr tattr = {
> +		.data_in = &pkt_v4,
> +		.data_size_in = sizeof(pkt_v4),
> +		.ctx_in = &skb,
> +		.ctx_size_in = sizeof(skb),
> +		.ctx_out = &skb,
> +		.ctx_size_out = sizeof(skb),
> +	};
> +	struct bpf_object *obj;
> +	int err;
> +
> +	err = bpf_prog_load("./test_skb_helpers.o", BPF_PROG_TYPE_SCHED_CLS, &obj,
> +			    &tattr.prog_fd);
> +	if (CHECK_ATTR(err, "load", "err %d errno %d\n", err, errno))
> +		return;
> +
> +	err = bpf_prog_test_run_xattr(&tattr);
> +	CHECK_ATTR(err != 0, "len", "err %d errno %d\n", err, errno);
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_skb_helpers.c b/tools/testing/selftests/bpf/progs/test_skb_helpers.c
> new file mode 100644
> index 0000000..05a1260
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_skb_helpers.c
> @@ -0,0 +1,33 @@
> +// SPDX-License-Identifier: GPL-2.0-only
> +#include "vmlinux.h"
> +#include <bpf/bpf_helpers.h>
> +#include <bpf/bpf_endian.h>
> +
> +int _version SEC("version") = 1;
> +
> +#define TEST_COMM_LEN 10
> +
> +struct bpf_map_def SEC("maps") cgroup_map = {
> +	.type			= BPF_MAP_TYPE_CGROUP_ARRAY,
> +	.key_size		= sizeof(u32),
> +	.value_size		= sizeof(u32),
> +	.max_entries	= 1,
> +};
> +
> +char _license[] SEC("license") = "GPL";
> +
> +SEC("classifier/test_skb_helpers")
> +int test_skb_helpers(struct __sk_buff *skb)
> +{
> +	struct task_struct *task;
> +	char *comm[TEST_COMM_LEN];
> +	__u32 tpid;
> +	int ctask;
> +
> +	ctask = bpf_current_task_under_cgroup(&cgroup_map, 0);

ctask is not used. Could you test ctask against expected value?

> +	task = (struct task_struct *)bpf_get_current_task();
> +
> +	bpf_probe_read_kernel(&tpid , sizeof(tpid), &task->tgid);
> +	bpf_probe_read_kernel_str(&comm, sizeof(comm), &task->comm);
> +	return 0;
> +}
>