On Tue, Dec 22, 2020 at 8:23 AM Jesper Dangaard Brouer
<brouer@xxxxxxxxxx> wrote:
>
> Adding selftest for BPF-helper bpf_check_mtu(). Making sure
> it can be used from both XDP and TC.
>
> V10:
> - Remove errno non-zero test in CHECK_ATTR()
> - Addresse comments from Andrii Nakryiko
>
> Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
> ---
Looks good, few minor nits below, feel free to address if you end up
with another revision.
Acked-by: Andrii Nakryiko <andrii@xxxxxxxxxx>
> tools/testing/selftests/bpf/prog_tests/check_mtu.c | 218 ++++++++++++++++++++
> tools/testing/selftests/bpf/progs/test_check_mtu.c | 199 ++++++++++++++++++
> 2 files changed, 417 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/prog_tests/check_mtu.c
> create mode 100644 tools/testing/selftests/bpf/progs/test_check_mtu.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/check_mtu.c b/tools/testing/selftests/bpf/prog_tests/check_mtu.c
> new file mode 100644
> index 000000000000..63f01c9e08d8
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/prog_tests/check_mtu.c
> @@ -0,0 +1,218 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/* Copyright (c) 2020 Jesper Dangaard Brouer */
> +
> +#include <linux/if_link.h> /* before test_progs.h, avoid bpf_util.h redefines */
> +
> +#include <test_progs.h>
> +#include "test_check_mtu.skel.h"
> +#include <network_helpers.h>
bit: test_progs and network_helpers should be included with "", not <>
> +
> +#include <stdlib.h>
> +#include <inttypes.h>
> +
> +#define IFINDEX_LO 1
> +
> +static __u32 duration; /* Hint: needed for CHECK macro */
> +
> +static int read_mtu_device_lo(void)
> +{
> + const char *filename = "/sys/class/net/lo/mtu";
> + char buf[11] = {};
> + int value;
> + int fd;
> +
> + fd = open(filename, 0, O_RDONLY);
> + if (fd == -1)
> + return -1;
> +
> + if (read(fd, buf, sizeof(buf)) == -1) {
> + close(fd);
> + return -2;
> + }
> + close(fd);
nit: imo, simpler to write:
err = read(...);
close(fd);
if (err == -1)
return -2;
This way you don't need to close twice. But it's very minor.
> +
> + value = strtoimax(buf, NULL, 10);
> + if (errno == ERANGE)
> + return -3;
> +
> + return value;
> +}
> +
[...]
> + CHECK(link_info.type != BPF_LINK_TYPE_XDP, "link_type",
> + "got %u != exp %u\n", link_info.type, BPF_LINK_TYPE_XDP);
> + CHECK(link_info.xdp.ifindex != IFINDEX_LO, "link_ifindex",
> + "got %u != exp %u\n", link_info.xdp.ifindex, IFINDEX_LO);
> +
> + err = bpf_link__detach(link);
> + CHECK(err, "link_detach", "failed %d\n", err);
> +
unless you explicitly want to test this force-detach, destroying the
link (through destroying skeleton) would detach the program just fine.
> +out:
> + test_check_mtu__destroy(skel);
> +}
> +
[...]
> +
> +SEC("xdp")
> +int xdp_exceed_mtu(struct xdp_md *ctx)
> +{
> + void *data_end = (void *)(long)ctx->data_end;
> + void *data = (void *)(long)ctx->data;
> + __u32 ifindex = GLOBAL_USER_IFINDEX;
> + __u32 data_len = data_end - data;
> + int retval = XDP_ABORTED; /* Fail */
> + __u32 mtu_len = 0;
> +
nit: unnecessary empty line inside variable declaration block
> + int delta;
> + int err;
> +
> + /* Exceed MTU with 1 via delta adjust */
> + delta = GLOBAL_USER_MTU - (data_len - ETH_HLEN) + 1;
> +
> + err = bpf_check_mtu(ctx, ifindex, &mtu_len, delta, 0);
> + if (err) {
> + retval = XDP_PASS; /* Success in exceeding MTU check */
> + if (err != BPF_MTU_CHK_RET_FRAG_NEEDED)
> + retval = XDP_DROP;
> + }
> +
> + global_bpf_mtu_xdp = mtu_len;
> + return retval;
> +}
> +
[...]
