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selftests/bpf: Tests using bpf_check_mtu BPF-helper
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Adding selftest for BPF-helper bpf_check_mtu(). Making sure
it can be used from both XDP and TC.

V16:
 - Fix 'void' function definition

V11:
 - Addresse nitpicks from Andrii Nakryiko

V10:
 - Remove errno non-zero test in CHECK_ATTR()
 - Addresse comments from Andrii Nakryiko

Signed-off-by: Jesper Dangaard Brouer <brouer@redhat.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: Andrii Nakryiko <andrii@kernel.org>
Link: https://lore.kernel.org/bpf/161287791989.790810.13612620012522164562.stgit@firesoul
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@netoptimizer @borkmann
netoptimizer authored and borkmann committed Feb 13, 2021
1 parent 6b8838b commit b62eba5
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216 changes: 216 additions & 0 deletions tools/testing/selftests/bpf/prog_tests/check_mtu.c
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// 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"

#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, n, fd;

fd = open(filename, 0, O_RDONLY);
if (fd == -1)
return -1;

n = read(fd, buf, sizeof(buf));
close(fd);

if (n == -1)
return -2;

value = strtoimax(buf, NULL, 10);
if (errno == ERANGE)
return -3;

return value;
}

static void test_check_mtu_xdp_attach(void)
{
struct bpf_link_info link_info;
__u32 link_info_len = sizeof(link_info);
struct test_check_mtu *skel;
struct bpf_program *prog;
struct bpf_link *link;
int err = 0;
int fd;

skel = test_check_mtu__open_and_load();
if (CHECK(!skel, "open and load skel", "failed"))
return; /* Exit if e.g. helper unknown to kernel */

prog = skel->progs.xdp_use_helper_basic;

link = bpf_program__attach_xdp(prog, IFINDEX_LO);
if (CHECK(IS_ERR(link), "link_attach", "failed: %ld\n", PTR_ERR(link)))
goto out;
skel->links.xdp_use_helper_basic = link;

memset(&link_info, 0, sizeof(link_info));
fd = bpf_link__fd(link);
err = bpf_obj_get_info_by_fd(fd, &link_info, &link_info_len);
if (CHECK(err, "link_info", "failed: %d\n", err))
goto out;

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);

out:
test_check_mtu__destroy(skel);
}

static void test_check_mtu_run_xdp(struct test_check_mtu *skel,
struct bpf_program *prog,
__u32 mtu_expect)
{
const char *prog_name = bpf_program__name(prog);
int retval_expect = XDP_PASS;
__u32 mtu_result = 0;
char buf[256] = {};
int err;
struct bpf_prog_test_run_attr tattr = {
.repeat = 1,
.data_in = &pkt_v4,
.data_size_in = sizeof(pkt_v4),
.data_out = buf,
.data_size_out = sizeof(buf),
.prog_fd = bpf_program__fd(prog),
};

err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err != 0, "bpf_prog_test_run",
"prog_name:%s (err %d errno %d retval %d)\n",
prog_name, err, errno, tattr.retval);

CHECK(tattr.retval != retval_expect, "retval",
"progname:%s unexpected retval=%d expected=%d\n",
prog_name, tattr.retval, retval_expect);

/* Extract MTU that BPF-prog got */
mtu_result = skel->bss->global_bpf_mtu_xdp;
ASSERT_EQ(mtu_result, mtu_expect, "MTU-compare-user");
}


static void test_check_mtu_xdp(__u32 mtu, __u32 ifindex)
{
struct test_check_mtu *skel;
int err;

skel = test_check_mtu__open();
if (CHECK(!skel, "skel_open", "failed"))
return;

/* Update "constants" in BPF-prog *BEFORE* libbpf load */
skel->rodata->GLOBAL_USER_MTU = mtu;
skel->rodata->GLOBAL_USER_IFINDEX = ifindex;

err = test_check_mtu__load(skel);
if (CHECK(err, "skel_load", "failed: %d\n", err))
goto cleanup;

test_check_mtu_run_xdp(skel, skel->progs.xdp_use_helper, mtu);
test_check_mtu_run_xdp(skel, skel->progs.xdp_exceed_mtu, mtu);
test_check_mtu_run_xdp(skel, skel->progs.xdp_minus_delta, mtu);

cleanup:
test_check_mtu__destroy(skel);
}

static void test_check_mtu_run_tc(struct test_check_mtu *skel,
struct bpf_program *prog,
__u32 mtu_expect)
{
const char *prog_name = bpf_program__name(prog);
int retval_expect = BPF_OK;
__u32 mtu_result = 0;
char buf[256] = {};
int err;
struct bpf_prog_test_run_attr tattr = {
.repeat = 1,
.data_in = &pkt_v4,
.data_size_in = sizeof(pkt_v4),
.data_out = buf,
.data_size_out = sizeof(buf),
.prog_fd = bpf_program__fd(prog),
};

err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err != 0, "bpf_prog_test_run",
"prog_name:%s (err %d errno %d retval %d)\n",
prog_name, err, errno, tattr.retval);

CHECK(tattr.retval != retval_expect, "retval",
"progname:%s unexpected retval=%d expected=%d\n",
prog_name, tattr.retval, retval_expect);

/* Extract MTU that BPF-prog got */
mtu_result = skel->bss->global_bpf_mtu_tc;
ASSERT_EQ(mtu_result, mtu_expect, "MTU-compare-user");
}


static void test_check_mtu_tc(__u32 mtu, __u32 ifindex)
{
struct test_check_mtu *skel;
int err;

skel = test_check_mtu__open();
if (CHECK(!skel, "skel_open", "failed"))
return;

/* Update "constants" in BPF-prog *BEFORE* libbpf load */
skel->rodata->GLOBAL_USER_MTU = mtu;
skel->rodata->GLOBAL_USER_IFINDEX = ifindex;

err = test_check_mtu__load(skel);
if (CHECK(err, "skel_load", "failed: %d\n", err))
goto cleanup;

test_check_mtu_run_tc(skel, skel->progs.tc_use_helper, mtu);
test_check_mtu_run_tc(skel, skel->progs.tc_exceed_mtu, mtu);
test_check_mtu_run_tc(skel, skel->progs.tc_exceed_mtu_da, mtu);
test_check_mtu_run_tc(skel, skel->progs.tc_minus_delta, mtu);
cleanup:
test_check_mtu__destroy(skel);
}

void test_check_mtu(void)
{
__u32 mtu_lo;

if (test__start_subtest("bpf_check_mtu XDP-attach"))
test_check_mtu_xdp_attach();

mtu_lo = read_mtu_device_lo();
if (CHECK(mtu_lo < 0, "reading MTU value", "failed (err:%d)", mtu_lo))
return;

if (test__start_subtest("bpf_check_mtu XDP-run"))
test_check_mtu_xdp(mtu_lo, 0);

if (test__start_subtest("bpf_check_mtu XDP-run ifindex-lookup"))
test_check_mtu_xdp(mtu_lo, IFINDEX_LO);

if (test__start_subtest("bpf_check_mtu TC-run"))
test_check_mtu_tc(mtu_lo, 0);

if (test__start_subtest("bpf_check_mtu TC-run ifindex-lookup"))
test_check_mtu_tc(mtu_lo, IFINDEX_LO);
}
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