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selftests/bpf: Add a BPF selftest for bpf_skb_change_tail()

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As requested by Daniel, we need to add a selftest to cover
bpf_skb_change_tail() cases in skb_verdict. Here we test trimming,
growing and error cases, and validate its expected return values and the
expected sizes of the payload.

Signed-off-by: Cong Wang <cong.wang@bytedance.com>
Signed-off-by: Daniel Borkmann <daniel@iogearbox.net>
Acked-by: John Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241213034057.246437-3-xiyou.wangcong@gmail.com
This commit is contained in:
Cong Wang 2024-12-12 19:40:55 -08:00 committed by Daniel Borkmann
parent 9ecc4d858b
commit 9ee0c7b865
2 changed files with 91 additions and 0 deletions
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51
tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
View File

@ -12,6 +12,7 @@
#include "test_sockmap_progs_query.skel.h"
#include "test_sockmap_pass_prog.skel.h"
#include "test_sockmap_drop_prog.skel.h"
#include "test_sockmap_change_tail.skel.h"
#include "bpf_iter_sockmap.skel.h"
#include "sockmap_helpers.h"
@ -643,6 +644,54 @@ static void test_sockmap_skb_verdict_fionread(bool pass_prog)
test_sockmap_drop_prog__destroy(drop);
}
static void test_sockmap_skb_verdict_change_tail(void)
{
struct test_sockmap_change_tail *skel;
int err, map, verdict;
int c1, p1, sent, recvd;
int zero = 0;
char buf[2];
skel = test_sockmap_change_tail__open_and_load();
if (!ASSERT_OK_PTR(skel, "open_and_load"))
return;
verdict = bpf_program__fd(skel->progs.prog_skb_verdict);
map = bpf_map__fd(skel->maps.sock_map_rx);
err = bpf_prog_attach(verdict, map, BPF_SK_SKB_STREAM_VERDICT, 0);
if (!ASSERT_OK(err, "bpf_prog_attach"))
goto out;
err = create_pair(AF_INET, SOCK_STREAM, &c1, &p1);
if (!ASSERT_OK(err, "create_pair()"))
goto out;
err = bpf_map_update_elem(map, &zero, &c1, BPF_NOEXIST);
if (!ASSERT_OK(err, "bpf_map_update_elem(c1)"))
goto out_close;
sent = xsend(p1, "Tr", 2, 0);
ASSERT_EQ(sent, 2, "xsend(p1)");
recvd = recv(c1, buf, 2, 0);
ASSERT_EQ(recvd, 1, "recv(c1)");
ASSERT_EQ(skel->data->change_tail_ret, 0, "change_tail_ret");
sent = xsend(p1, "G", 1, 0);
ASSERT_EQ(sent, 1, "xsend(p1)");
recvd = recv(c1, buf, 2, 0);
ASSERT_EQ(recvd, 2, "recv(c1)");
ASSERT_EQ(skel->data->change_tail_ret, 0, "change_tail_ret");
sent = xsend(p1, "E", 1, 0);
ASSERT_EQ(sent, 1, "xsend(p1)");
recvd = recv(c1, buf, 1, 0);
ASSERT_EQ(recvd, 1, "recv(c1)");
ASSERT_EQ(skel->data->change_tail_ret, -EINVAL, "change_tail_ret");
out_close:
close(c1);
close(p1);
out:
test_sockmap_change_tail__destroy(skel);
}
static void test_sockmap_skb_verdict_peek_helper(int map)
{
int err, c1, p1, zero = 0, sent, recvd, avail;
@ -1058,6 +1107,8 @@ void test_sockmap_basic(void)
test_sockmap_skb_verdict_fionread(true);
if (test__start_subtest("sockmap skb_verdict fionread on drop"))
test_sockmap_skb_verdict_fionread(false);
if (test__start_subtest("sockmap skb_verdict change tail"))
test_sockmap_skb_verdict_change_tail();
if (test__start_subtest("sockmap skb_verdict msg_f_peek"))
test_sockmap_skb_verdict_peek();
if (test__start_subtest("sockmap skb_verdict msg_f_peek with link"))

40
tools/testing/selftests/bpf/progs/test_sockmap_change_tail.c Normal file
View File

@ -0,0 +1,40 @@
// SPDX-License-Identifier: GPL-2.0
/* Copyright (c) 2024 ByteDance */
#include <linux/bpf.h>
#include <bpf/bpf_helpers.h>
struct {
__uint(type, BPF_MAP_TYPE_SOCKMAP);
__uint(max_entries, 1);
__type(key, int);
__type(value, int);
} sock_map_rx SEC(".maps");
long change_tail_ret = 1;
SEC("sk_skb")
int prog_skb_verdict(struct __sk_buff *skb)
{
char *data, *data_end;
bpf_skb_pull_data(skb, 1);
data = (char *)(unsigned long)skb->data;
data_end = (char *)(unsigned long)skb->data_end;
if (data + 1 > data_end)
return SK_PASS;
if (data[0] == 'T') { /* Trim the packet */
change_tail_ret = bpf_skb_change_tail(skb, skb->len - 1, 0);
return SK_PASS;
} else if (data[0] == 'G') { /* Grow the packet */
change_tail_ret = bpf_skb_change_tail(skb, skb->len + 1, 0);
return SK_PASS;
} else if (data[0] == 'E') { /* Error */
change_tail_ret = bpf_skb_change_tail(skb, 65535, 0);
return SK_PASS;
}
return SK_PASS;
}
char _license[] SEC("license") = "GPL";