linux-kernel - Re: [PATCH v4 bpf 2/2] bpf: selftests: add lwt redirect regression test cases

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Date:   Fri, 28 Jul 2023 15:47:40 -0700
From:   Martin KaFai Lau <martin.lau@...ux.dev>
To:     Yan Zhai <yan@...udflare.com>
Cc:     bpf@...r.kernel.org, Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Song Liu <song@...nel.org>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Stanislav Fomichev <sdf@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        "David S. Miller" <davem@...emloft.net>,
        Eric Dumazet <edumazet@...gle.com>,
        Jakub Kicinski <kuba@...nel.org>,
        Paolo Abeni <pabeni@...hat.com>,
        Mykola Lysenko <mykolal@...com>, Shuah Khan <shuah@...nel.org>,
        linux-kernel@...r.kernel.org, netdev@...r.kernel.org,
        linux-kselftest@...r.kernel.org, kernel-team@...udflare.com,
        Jordan Griege <jgriege@...udflare.com>,
        Markus Elfring <Markus.Elfring@....de>,
        Jakub Sitnicki <jakub@...udflare.com>
Subject: Re: [PATCH v4 bpf 2/2] bpf: selftests: add lwt redirect regression
 test cases

On 7/25/23 6:09 PM, Yan Zhai wrote:
> diff --git a/tools/testing/selftests/bpf/progs/test_lwt_redirect.c b/tools/testing/selftests/bpf/progs/test_lwt_redirect.c
> new file mode 100644
> index 000000000000..3674e101f68f
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/progs/test_lwt_redirect.c
> @@ -0,0 +1,66 @@
> +// SPDX-License-Identifier: GPL-2.0
> +#include <linux/bpf.h>
> +#include <bpf/bpf_helpers.h>
> +#include "bpf_tracing_net.h"
> +
> +/* We don't care about whether the packet can be received by network stack.
> + * Just care if the packet is sent to the correct device at correct direction
> + * and not panic the kernel.
> + */
> +static __always_inline int prepend_dummy_mac(struct __sk_buff *skb)
> +{

__always_inline is no longer a must for a long time.

> +	char mac[] = {0x1, 0x2, 0x3, 0x4, 0x5, 0x6, 0xf,
> +		      0xe, 0xd, 0xc, 0xb, 0xa, 0x08, 0x00};
> +
> +	if (bpf_skb_change_head(skb, ETH_HLEN, 0)) {
> +		bpf_printk("%s: fail to change head", __func__);

Avoid using bpf_printk(). The bpf CI runs other tests also.

> +		return -1;
> +	}
> +
> +	if (bpf_skb_store_bytes(skb, 0, mac, sizeof(mac), 0)) {
> +		bpf_printk("%s: fail to update mac", __func__);
> +		return -1;
> +	}
> +
> +	return 0;
> +}
> +
> +SEC("redir_ingress")

Use SEC("lwt_xmit"). Then the libbpf will figure out the prog type.

> +int test_lwt_redirect_in(struct __sk_buff *skb)
> +{
> +	if (prepend_dummy_mac(skb))
> +		return BPF_DROP;
> +
> +	bpf_printk("Redirect skb to link %d ingress", skb->mark);
> +	return bpf_redirect(skb->mark, BPF_F_INGRESS);
> +}
> +
> +SEC("redir_egress")
> +int test_lwt_redirect_out(struct __sk_buff *skb)
> +{
> +	if (prepend_dummy_mac(skb))
> +		return BPF_DROP;
> +
> +	bpf_printk("Redirect skb to link %d egress", skb->mark);
> +	return bpf_redirect(skb->mark, 0);
> +}
> +
> +SEC("redir_egress_nomac")
> +int test_lwt_redirect_out_nomac(struct __sk_buff *skb)
> +{
> +	int ret = bpf_redirect(skb->mark, 0);
> +
> +	bpf_printk("Redirect skb to link %d egress nomac: %d", skb->mark, ret);
> +	return ret;
> +}
> +
> +SEC("redir_ingress_nomac")
> +int test_lwt_redirect_in_nomac(struct __sk_buff *skb)
> +{
> +	int ret = bpf_redirect(skb->mark, BPF_F_INGRESS);
> +
> +	bpf_printk("Redirect skb to link %d ingress nomac: %d", skb->mark, ret);
> +	return ret;
> +}
> +
> +char _license[] SEC("license") = "GPL";
> diff --git a/tools/testing/selftests/bpf/test_lwt_redirect.sh b/tools/testing/selftests/bpf/test_lwt_redirect.sh
> new file mode 100755
> index 000000000000..1b7b78b48174
> --- /dev/null
> +++ b/tools/testing/selftests/bpf/test_lwt_redirect.sh

This has to be written in the test_progs infrastructure in C. Only test_progs is 
run by the BPF CI. Take a look at other tests in prog_tests/. For example, 
tc_redirect.c and xdp_metadata.c which are having setup in netns/link/...etc. It 
currently has helpers to add tc qdisc and filter but not adding route yet which 
could be a useful addition.

--
pw-bot: cr