linux-kernel - Re: [PATCH] samples/bpf: Add sample usage for BPF_PROG_TYPE

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Message-ID: <87wmx5ovv0.fsf@toke.dk>
Date:   Tue, 05 Sep 2023 10:41:23 +0200
From:   Toke Høiland-Jørgensen <toke@...nel.org>
To:     David Wang <00107082@....com>,
        Alexei Starovoitov <alexei.starovoitov@...il.com>
Cc:     Florian Westphal <fw@...len.de>,
        Alexei Starovoitov <ast@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Andrii Nakryiko <andrii@...nel.org>,
        Martin KaFai Lau <martin.lau@...ux.dev>,
        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@...gle.com>,
        Hao Luo <haoluo@...gle.com>, Jiri Olsa <jolsa@...nel.org>,
        LKML <linux-kernel@...r.kernel.org>, bpf <bpf@...r.kernel.org>
Subject: Re: [PATCH] samples/bpf: Add sample usage for BPF_PROG_TYPE_NETFILTER

"David Wang" <00107082@....com> writes:

> At 2023-09-05 05:01:14, "Alexei Starovoitov" <alexei.starovoitov@...il.com> wrote:
>>On Mon, Sep 4, 2023 at 3:49 AM Florian Westphal <fw@...len.de> wrote:
>>>
>>> David Wang <00107082@....com> wrote:
>>> > This sample code implements a simple ipv4
>>> > blacklist via the new bpf type BPF_PROG_TYPE_NETFILTER,
>>> > which was introduced in 6.4.
>>> >
>>> > The bpf program drops package if destination ip address
>>> > hits a match in the map of type BPF_MAP_TYPE_LPM_TRIE,
>>> >
>>> > The userspace code would load the bpf program,
>>> > attach it to netfilter's FORWARD/OUTPUT hook,
>>> > and then write ip patterns into the bpf map.
>>>
>>> Thanks, I think its good to have this.
>>
>>Yes, but only in selftests/bpf.
>>samples/bpf/ are not tested and bit rot heavily.
>
> My purpose is to demonstrate the basic usage of BPF_PROG_TYPE_NETFILTER ,  showing what bpf program and userspace program should do to make it work.
> The code is neither  thorough  enough to make a valid test suite,  nor  detailed enough to make out a tool (Could be a start for a tool)
>
> samples/bpf is a good  place to start for  beginners to get along  with bpf quickly,   those  sample/bpf codes do help me a lot,
>   but selftests/bpf is not that  friendly, at least not friendly for beginners, I think.   
> There are already test codes for   BPF_PROG_TYPE_NETFILTER in selftests/bpf,  actually I did refer to those code  when I made this sample.
>
> Get a feeling samples/bpf would be deprecated sooner or later, hope that would not happen.
>
> Anyway, this sample code is not meant to test. 

FYI, we maintain a Github repository with BPF example programs of
various types at https://github.com/xdp-project/bpf-examples

Happy to include this example there as an alternative to the in-tree
samples/bpf :)

-Toke