Re: [PATCH v2 bpf-next 8/8] selftest: add tests for XDP programs in CPUMAP entries

[Andrii Nakryiko <andrii.nakryiko@gmail.com>]

On Fri, Jun 19, 2020 at 9:55 PM Lorenzo Bianconi <lorenzo@kernel.org> wrote:
>
> Similar to what have been done for DEVMAP, introduce tests to verify
> ability to add a XDP program to an entry in a CPUMAP.
> Verify CPUMAP programs can not be attached to devices as a normal
> XDP program, and only programs with BPF_XDP_CPUMAP attach type can
> be loaded in a CPUMAP.
>
> Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
> ---
>  .../bpf/prog_tests/xdp_cpumap_attach.c        | 70 +++++++++++++++++++
>  .../bpf/progs/test_xdp_with_cpumap_helpers.c  | 38 ++++++++++
>  2 files changed, 108 insertions(+)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
> new file mode 100644
> index 000000000000..2baa41689f40
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/xdp_cpumap_attach.c
> @@ -0,0 +1,70 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <uapi/linux/bpf.h>
> +#include <linux/if_link.h>
> +#include <test_progs.h>
> +
> +#include "test_xdp_with_cpumap_helpers.skel.h"
> +
> +#define IFINDEX_LO     1
> +
> +void test_xdp_with_cpumap_helpers(void)
> +{
> +       struct test_xdp_with_cpumap_helpers *skel;
> +       struct bpf_prog_info info = {};
> +       struct bpf_cpumap_val val = {
> +               .qsize = 192,
> +       };
> +       __u32 duration = 0, idx = 0;
> +       __u32 len = sizeof(info);
> +       int err, prog_fd, map_fd;
> +
> +       skel = test_xdp_with_cpumap_helpers__open_and_load();
> +       if (CHECK_FAIL(!skel)) {
> +               perror("test_xdp_with_cpumap_helpers__open_and_load");
> +               return;
> +       }
> +
> +       /* can not attach program with cpumaps that allow programs
> +        * as xdp generic
> +        */
> +       prog_fd = bpf_program__fd(skel->progs.xdp_redir_prog);
> +       err = bpf_set_link_xdp_fd(IFINDEX_LO, prog_fd, XDP_FLAGS_SKB_MODE);
> +       CHECK(err == 0, "Generic attach of program with 8-byte CPUMAP",
> +             "should have failed\n");
> +
> +       prog_fd = bpf_program__fd(skel->progs.xdp_dummy_cm);
> +       map_fd = bpf_map__fd(skel->maps.cpu_map);
> +       err = bpf_obj_get_info_by_fd(prog_fd, &info, &len);
> +       if (CHECK_FAIL(err))
> +               goto out_close;
> +
> +       val.bpf_prog.fd = prog_fd;
> +       err = bpf_map_update_elem(map_fd, &idx, &val, 0);
> +       CHECK(err, "Add program to cpumap entry", "err %d errno %d\n",
> +             err, errno);
> +
> +       err = bpf_map_lookup_elem(map_fd, &idx, &val);
> +       CHECK(err, "Read cpumap entry", "err %d errno %d\n", err, errno);
> +       CHECK(info.id != val.bpf_prog.id, "Expected program id in cpumap entry",
> +             "expected %u read %u\n", info.id, val.bpf_prog.id);
> +
> +       /* can not attach BPF_XDP_CPUMAP program to a device */
> +       err = bpf_set_link_xdp_fd(IFINDEX_LO, prog_fd, XDP_FLAGS_SKB_MODE);
> +       CHECK(err == 0, "Attach of BPF_XDP_CPUMAP program",
> +             "should have failed\n");
> +
> +       val.qsize = 192;
> +       val.bpf_prog.fd = bpf_program__fd(skel->progs.xdp_dummy_prog);
> +       err = bpf_map_update_elem(map_fd, &idx, &val, 0);
> +       CHECK(err == 0, "Add non-BPF_XDP_CPUMAP program to cpumap entry",
> +             "should have failed\n");
> +
> +out_close:
> +       test_xdp_with_cpumap_helpers__destroy(skel);
> +}
> +
> +void test_xdp_cpumap_attach(void)
> +{
> +       if (test__start_subtest("CPUMAP with programs in entries"))

These subtest names are supposed to be short and follow test names
(i.e., being more or less valid C identifiers). It makes it easier to
select or blacklist them (with -t and -b params). So something like
cpumap_with_progs or similar would be better in that regard and would
make it easier for me to maintain a blacklist of tests/subtests for
Travis CI, for instance.

I think there is similarly verbose DEVMAP subtest name, I'd love it to
be "simplified" as well... But can't get my hands on everything,
unfortunately.

> +               test_xdp_with_cpumap_helpers();
> +}
> diff --git a/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c b/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c
> new file mode 100644
> index 000000000000..acbbc62efa55
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_xdp_with_cpumap_helpers.c
> @@ -0,0 +1,38 @@
> +// SPDX-License-Identifier: GPL-2.0
> +
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +
> +struct {
> +       __uint(type, BPF_MAP_TYPE_CPUMAP);
> +       __uint(key_size, sizeof(__u32));
> +       __uint(value_size, sizeof(struct bpf_cpumap_val));
> +       __uint(max_entries, 4);
> +} cpu_map SEC(".maps");
> +
> +SEC("xdp_redir")
> +int xdp_redir_prog(struct xdp_md *ctx)
> +{
> +       return bpf_redirect_map(&cpu_map, 1, 0);
> +}
> +
> +SEC("xdp_dummy")
> +int xdp_dummy_prog(struct xdp_md *ctx)
> +{
> +       return XDP_PASS;
> +}
> +
> +SEC("xdp_cpumap")
> +int xdp_dummy_cm(struct xdp_md *ctx)
> +{
> +       char fmt[] = "devmap redirect: dev %u len %u\n";
> +       void *data_end = (void *)(long)ctx->data_end;
> +       void *data = (void *)(long)ctx->data;
> +       unsigned int len = data_end - data;
> +
> +       bpf_trace_printk(fmt, sizeof(fmt), ctx->ingress_ifindex, len);

Is there any reason to use bpf_trace_printk as opposed to saving
ctx->ingress_ifindex into a global variable? bpf_trace_printk isn't
really testing anything, just pollutes trace_pipe.

> +
> +       return XDP_PASS;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> --
> 2.26.2
>