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selftests: bpf: add selftest for __sk_buff context in BPF_PROG_TEST_RUN 

Simple test that sets cb to {1,2,3,4,5} and priority to 6, runs bpf
program that fails if cb is not what we expect and increments cb[i] and
priority. When the test finishes, we check that cb is now {2,3,4,5,6}
and priority is 7.

We also test the sanity checks:
* ctx_in is provided, but ctx_size_in is zero (same for
  ctx_out/ctx_size_out)
* unexpected non-zero fields in __sk_buff return EINVAL

Signed-off-by: Stanislav Fomichev <sdf@google.com>
Acked-by: Martin KaFai Lau <kafai@fb.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
This commit is contained in:
Stanislav Fomichev 2019-04-09 11:49:11 -07:00 committed by Daniel Borkmann
parent 5e903c656b
commit 3daf8e703e
2 changed files with 110 additions and 0 deletions
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89
tools/testing/selftests/bpf/prog_tests/skb_ctx.c Normal file
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@ -0,0 +1,89 @@
// SPDX-License-Identifier: GPL-2.0
#include <test_progs.h>
void test_skb_ctx(void)
{
struct __sk_buff skb = {
.cb[0] = 1,
.cb[1] = 2,
.cb[2] = 3,
.cb[3] = 4,
.cb[4] = 5,
.priority = 6,
};
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;
int i;
err = bpf_prog_load("./test_skb_ctx.o", BPF_PROG_TYPE_SCHED_CLS, &obj,
&tattr.prog_fd);
if (CHECK_ATTR(err, "load", "err %d errno %d\n", err, errno))
return;
/* ctx_in != NULL, ctx_size_in == 0 */
tattr.ctx_size_in = 0;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err == 0, "ctx_size_in", "err %d errno %d\n", err, errno);
tattr.ctx_size_in = sizeof(skb);
/* ctx_out != NULL, ctx_size_out == 0 */
tattr.ctx_size_out = 0;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err == 0, "ctx_size_out", "err %d errno %d\n", err, errno);
tattr.ctx_size_out = sizeof(skb);
/* non-zero [len, tc_index] fields should be rejected*/
skb.len = 1;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err == 0, "len", "err %d errno %d\n", err, errno);
skb.len = 0;
skb.tc_index = 1;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err == 0, "tc_index", "err %d errno %d\n", err, errno);
skb.tc_index = 0;
/* non-zero [hash, sk] fields should be rejected */
skb.hash = 1;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err == 0, "hash", "err %d errno %d\n", err, errno);
skb.hash = 0;
skb.sk = (struct bpf_sock *)1;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err == 0, "sk", "err %d errno %d\n", err, errno);
skb.sk = 0;
err = bpf_prog_test_run_xattr(&tattr);
CHECK_ATTR(err != 0 || tattr.retval,
"run",
"err %d errno %d retval %d\n",
err, errno, tattr.retval);
CHECK_ATTR(tattr.ctx_size_out != sizeof(skb),
"ctx_size_out",
"incorrect output size, want %lu have %u\n",
sizeof(skb), tattr.ctx_size_out);
for (i = 0; i < 5; i++)
CHECK_ATTR(skb.cb[i] != i + 2,
"ctx_out_cb",
"skb->cb[i] == %d, expected %d\n",
skb.cb[i], i + 2);
CHECK_ATTR(skb.priority != 7,
"ctx_out_priority",
"skb->priority == %d, expected %d\n",
skb.priority, 7);
}

21
tools/testing/selftests/bpf/progs/test_skb_ctx.c Normal file
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// SPDX-License-Identifier: GPL-2.0
#include <linux/bpf.h>
#include "bpf_helpers.h"
int _version SEC("version") = 1;
char _license[] SEC("license") = "GPL";
SEC("skb_ctx")
int process(struct __sk_buff *skb)
{
#pragma clang loop unroll(full)
for (int i = 0; i < 5; i++) {
if (skb->cb[i] != i + 1)
return 1;
skb->cb[i]++;
}
skb->priority++;
return 0;
}