Commit 9ee0c7b8 authored by Cong Wang's avatar Cong Wang Committed by Daniel Borkmann
Browse files

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



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: default avatarCong Wang <cong.wang@bytedance.com>
Signed-off-by: default avatarDaniel Borkmann <daniel@iogearbox.net>
Acked-by: default avatarJohn Fastabend <john.fastabend@gmail.com>
Link: https://lore.kernel.org/bpf/20241213034057.246437-3-xiyou.wangcong@gmail.com
parent 9ecc4d85

tools/testing/selftests/bpf/prog_tests/sockmap_basic.c

+51 −0
Original line number Diff line number Diff line
@@ -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"))

tools/testing/selftests/bpf/progs/test_sockmap_change_tail.c

0 → 100644
+40 −0
Original line number Diff line number Diff line 
// 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";