netdev - Re: [PATCH bpf-next 10/10] bpf: Add sample for raw syncookie helpers

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Date:   Thu, 21 Oct 2021 20:31:06 +0300
From:   Maxim Mikityanskiy <maximmi@...dia.com>
To:     Alexei Starovoitov <alexei.starovoitov@...il.com>
CC:     Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <kafai@...com>,
        Song Liu <songliubraving@...com>, Yonghong Song <yhs@...com>,
        John Fastabend <john.fastabend@...il.com>,
        KP Singh <kpsingh@...nel.org>,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Jakub Kicinski <kuba@...nel.org>,
        Hideaki YOSHIFUJI <yoshfuji@...ux-ipv6.org>,
        David Ahern <dsahern@...nel.org>,
        "Jesper Dangaard Brouer" <hawk@...nel.org>,
        Nathan Chancellor <nathan@...nel.org>,
        "Nick Desaulniers" <ndesaulniers@...gle.com>,
        Brendan Jackman <jackmanb@...gle.com>,
        Florent Revest <revest@...omium.org>,
        Joe Stringer <joe@...ium.io>,
        "Lorenz Bauer" <lmb@...udflare.com>,
        Tariq Toukan <tariqt@...dia.com>, <netdev@...r.kernel.org>,
        <bpf@...r.kernel.org>, <clang-built-linux@...glegroups.com>
Subject: Re: [PATCH bpf-next 10/10] bpf: Add sample for raw syncookie helpers

On 2021-10-21 04:06, Alexei Starovoitov wrote:
> On Tue, Oct 19, 2021 at 05:46:55PM +0300, Maxim Mikityanskiy wrote:
>> This commit adds a sample for the new BPF helpers: bpf_ct_lookup_tcp,
>> bpf_tcp_raw_gen_syncookie and bpf_tcp_raw_check_syncookie.
>>
>> samples/bpf/syncookie_kern.c is a BPF program that generates SYN cookies
>> on allowed TCP ports and sends SYNACKs to clients, accelerating synproxy
>> iptables module.
>>
>> samples/bpf/syncookie_user.c is a userspace control application that
>> allows to configure the following options in runtime: list of allowed
>> ports, MSS, window scale, TTL.
>>
>> samples/bpf/syncookie_test.sh is a script that demonstrates the setup of
>> synproxy with XDP acceleration.
>>
>> Signed-off-by: Maxim Mikityanskiy <maximmi@...dia.com>
>> Reviewed-by: Tariq Toukan <tariqt@...dia.com>
>> ---
>>   samples/bpf/.gitignore        |   1 +
>>   samples/bpf/Makefile          |   3 +
>>   samples/bpf/syncookie_kern.c  | 591 ++++++++++++++++++++++++++++++++++
>>   samples/bpf/syncookie_test.sh |  55 ++++
>>   samples/bpf/syncookie_user.c  | 388 ++++++++++++++++++++++
>>   5 files changed, 1038 insertions(+)
>>   create mode 100644 samples/bpf/syncookie_kern.c
>>   create mode 100755 samples/bpf/syncookie_test.sh
>>   create mode 100644 samples/bpf/syncookie_user.c
> 
> Tests should be in selftests/bpf.
> Samples are for samples only.

It's not a test, please don't be confused by the name of 
syncookie_test.sh - it's more like a demo script.

syncookie_user.c and syncookie_kern.c are 100% a sample, they show how 
to use the new helpers and are themselves a more or less 
feature-complete solution to protect from SYN flood. syncookie_test.sh 
should probably be named syncookie_demo.sh, it demonstrates how to bring 
pieces together.

These files aren't aimed to be a unit test for the new helpers, their 
purpose is to show the usage.

> 
>> +// SPDX-License-Identifier: GPL-2.0 OR Linux-OpenIB
> 
> Isn't it deprecated?
> LICENSES/deprecated/Linux-OpenIB

Honestly, I had no idea, I just used our template. I'll ask whoever is 
responsible for the license.

If it's deprecated, what should be used instead?

> 
>> +	// Don't combine additions to avoid 32-bit overflow.
> 
> c++ style comment?
> did you run checkpatch?

Sure I did, and it doesn't complain on such comments. If such comments 
are a problem, please tell me, but I also saw them in other BPF samples.

Thanks for reviewing!