linux-kernel - Re: [RFC nf-next v5 0/2] netfilter: bpf: support prog update

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Message-ID: <70114fff-43bd-4e27-9abf-45345624042c@naccy.de>
Date: Wed, 14 Feb 2024 17:10:46 +0100
From: Quentin Deslandes <qde@...cy.de>
To: "D. Wythe" <alibuda@...ux.alibaba.com>, pablo@...filter.org,
 kadlec@...filter.org, fw@...len.de
Cc: bpf@...r.kernel.org, linux-kernel@...r.kernel.org,
 netdev@...r.kernel.org, coreteam@...filter.org,
 netfilter-devel@...r.kernel.org, davem@...emloft.net, edumazet@...gle.com,
 kuba@...nel.org, pabeni@...hat.com, ast@...nel.org
Subject: Re: [RFC nf-next v5 0/2] netfilter: bpf: support prog update

On 2024-01-02 07:11, D. Wythe wrote:
> From: "D. Wythe" <alibuda@...ux.alibaba.com>
> 
> This patches attempt to implements updating of progs within
> bpf netfilter link, allowing user update their ebpf netfilter
> prog in hot update manner.
> 
> Besides, a corresponding test case has been added to verify
> whether the update works.
> --
> v1:
> 1. remove unnecessary context, access the prog directly via rcu.
> 2. remove synchronize_rcu(), dealloc the nf_link via kfree_rcu.
> 3. check the dead flag during the update.
> --
> v1->v2:
> 1. remove unnecessary nf_prog, accessing nf_link->link.prog in direct.
> --
> v2->v3:
> 1. access nf_link->link.prog via rcu_dereference_raw to avoid warning.
> --
> v3->v4:
> 1. remove mutex for link update, as it is unnecessary and can be replaced
> by atomic operations.
> --
> v4->v5:
> 1. fix error retval check on cmpxhcg
> 
> D. Wythe (2):
>   netfilter: bpf: support prog update
>   selftests/bpf: Add netfilter link prog update test
> 
>  net/netfilter/nf_bpf_link.c                        | 50 ++++++++-----
>  .../bpf/prog_tests/netfilter_link_update_prog.c    | 83 ++++++++++++++++++++++
>  .../bpf/progs/test_netfilter_link_update_prog.c    | 24 +++++++
>  3 files changed, 141 insertions(+), 16 deletions(-)
>  create mode 100644 tools/testing/selftests/bpf/prog_tests/netfilter_link_update_prog.c
>  create mode 100644 tools/testing/selftests/bpf/progs/test_netfilter_link_update_prog.c
> 

It seems this patch has been forgotten, hopefully this answer
will give it more visibility.

I've applied this change on 6.8.0-rc4 and tested BPF_LINK_UPDATE
with bpfilter and everything seems alright.

Thanks,
Quentin