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Message-ID: <67a0fb14-f791-4499-8751-01bbbd1cafcb@bytedance.com>
Date: Thu, 7 Nov 2024 16:02:19 -0800
From: Zijian Zhang <zijianzhang@...edance.com>
To: Cong Wang <xiyou.wangcong@...il.com>, netdev@...r.kernel.org
Cc: bpf@...r.kernel.org, Cong Wang <cong.wang@...edance.com>,
John Fastabend <john.fastabend@...il.com>,
Daniel Borkmann <daniel@...earbox.net>
Subject: Re: [External] [Patch bpf 2/2] selftests/bpf: Add a BPF selftest for
bpf_skb_change_tail()
On 11/6/24 7:41 PM, Cong Wang wrote:
> From: Cong Wang <cong.wang@...edance.com>
>
> 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.
>
> Cc: John Fastabend <john.fastabend@...il.com>
> Cc: Daniel Borkmann <daniel@...earbox.net>
> Cc: Zijian Zhang <zijianzhang@...edance.com>
> Signed-off-by: Cong Wang <cong.wang@...edance.com>
> ---
> .../selftests/bpf/prog_tests/sockmap_basic.c | 51 +++++++++++++++++++
> .../bpf/progs/test_sockmap_change_tail.c | 40 +++++++++++++++
> 2 files changed, 91 insertions(+)
> create mode 100644 tools/testing/selftests/bpf/progs/test_sockmap_change_tail.c
>
> diff --git a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> index 82bfb266741c..fe735fced836 100644
> --- a/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> +++ b/tools/testing/selftests/bpf/prog_tests/sockmap_basic.c
> @@ -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"
> @@ -562,6 +563,54 @@ 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 b[3];
> +
> + 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, b, 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, b, 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, b, 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;
> @@ -927,6 +976,8 @@ 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"))
> diff --git a/tools/testing/selftests/bpf/progs/test_sockmap_change_tail.c b/tools/testing/selftests/bpf/progs/test_sockmap_change_tail.c
> new file mode 100644
> index 000000000000..2796dd8545eb
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_sockmap_change_tail.c
> @@ -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";
LGTM!
I think it will be better if the test could also cover the case you
indicated in the first patch, where skb_transport_offset is a negative
value.
Thanks,
Zijian
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