linux-kernel - Re: [PATCH bpf-next v4 4/4] selftests/bpf: convert test_skb_cgroup_id_user to test

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Message-ID: <b3329b35-a41b-4f21-9b7b-8fc9b04eedd2@bootlin.com>
Date: Thu, 15 Aug 2024 10:17:03 +0200
From: Alexis Lothoré <alexis.lothore@...tlin.com>
To: Martin KaFai Lau <martin.lau@...ux.dev>
Cc: Alexei Starovoitov <ast@...nel.org>,
 Daniel Borkmann <daniel@...earbox.net>, Andrii Nakryiko <andrii@...nel.org>,
 Eduard Zingerman <eddyz87@...il.com>, Song Liu <song@...nel.org>,
 Yonghong Song <yonghong.song@...ux.dev>,
 John Fastabend <john.fastabend@...il.com>, KP Singh <kpsingh@...nel.org>,
 Stanislav Fomichev <sdf@...ichev.me>, Hao Luo <haoluo@...gle.com>,
 Jiri Olsa <jolsa@...nel.org>, Mykola Lysenko <mykolal@...com>,
 Shuah Khan <shuah@...nel.org>, ebpf@...uxfoundation.org,
 Thomas Petazzoni <thomas.petazzoni@...tlin.com>,
 linux-kernel@...r.kernel.org, bpf@...r.kernel.org,
 linux-kselftest@...r.kernel.org, Alan Maguire <alan.maguire@...cle.com>
Subject: Re: [PATCH bpf-next v4 4/4] selftests/bpf: convert
 test_skb_cgroup_id_user to test_progs

Hello Martin,

On 8/15/24 04:20, Martin KaFai Lau wrote:
> On 8/13/24 5:45 AM, Alexis Lothoré (eBPF Foundation) wrote:
> 
>> +#define DST_ADDR "ff02::1"
> 
> [ ... ]
> 
>> +static int wait_local_ip(void)
>> +{
>> +    char *ping_cmd = ping_command(AF_INET6);
>> +    int i, err;
>> +
>> +    for (i = 0; i < WAIT_AUTO_IP_MAX_ATTEMPT; i++) {
>> +        err = SYS_NOFAIL("%s -c 1 -W 1 %s%%%s", ping_cmd, DST_ADDR,
>> +                 VETH_1);
> 
> I tried in my qemu. This loop takes at least 3-4 iteration to get the ping
> through. This test could become flaky if the CI is busy.
> 
> I have been always wondering why some of the (non) test_progs has this practice.
> I traced a little. I think it has something to do with the "ff02::1" used in the
> test and/or the local link address is not ready. I have not further nailed it
> down but I think it is close enough.
> 
> It will be easier to use a nodad configured v6 addr.
> 
> I take this chance to use an easier "::1" address for the test here instead of
> ff02::1. This also removed the need to add veth pair and no need to ping first.
> 
> Applied with the "::1" changes mentioned above.

Thanks for the improvement. So far I tried to preserve as much as possible the
original test behavior to avoid accidentally removing some important features,
but I guess the more tests I work on, the more confident I will be to
"challenge" some parts ;)

> Thanks for migrating the tests to test_progs. This is long overdue.

For the record, the next test I am targeting is test_xdp_features.sh. I have
undertaken the conversion and have a working base but it still needs some work.

Thanks,

Alexis


-- 
Alexis Lothoré, Bootlin
Embedded Linux and Kernel engineering
https://bootlin.com