netdev - Re: [PATCH bpf-next v5 0/6] Support direct writes to nf

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Date:   Sun, 11 Sep 2022 11:26:36 -0600
From:   Daniel Xu <dxu@...uu.xyz>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     bpf@...r.kernel.org, ast@...nel.org, daniel@...earbox.net,
        andrii@...nel.org, pablo@...filter.org, fw@...len.de,
        toke@...nel.org, martin.lau@...ux.dev,
        netfilter-devel@...r.kernel.org, netdev@...r.kernel.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH bpf-next v5 0/6] Support direct writes to nf_conn:mark

Hi Kumar,

On Sat, Sep 10, 2022 at 02:27:38AM +0200, Kumar Kartikeya Dwivedi wrote:
> On Wed, 7 Sept 2022 at 18:41, Daniel Xu <dxu@...uu.xyz> wrote:
> >
> > Support direct writes to nf_conn:mark from TC and XDP prog types. This
> > is useful when applications want to store per-connection metadata. This
> > is also particularly useful for applications that run both bpf and
> > iptables/nftables because the latter can trivially access this metadata.
> >
> > One example use case would be if a bpf prog is responsible for advanced
> > packet classification and iptables/nftables is later used for routing
> > due to pre-existing/legacy code.
> >
> 
> There are a couple of compile time warnings when conntrack is disabled,
> 
> ../net/core/filter.c:8608:1: warning: symbol 'nf_conn_btf_access_lock'
> was not declared. Should it be static?
> ../net/core/filter.c:8611:5: warning: symbol 'nfct_bsa' was not
> declared. Should it be static?
> 
> Most likely because extern declaration is guarded by ifdefs. So just
> moving those out of ifdef should work.
> I guess you can send that as a follow up fix, or roll it in if you end
> up respinning.

Hmm, I don't see how filter.c ever #include's nf_conntrack_bpf.h. So
you'd think that the warning would always be present regardless of
CONFIG_NF_CONNTRACK setting.

FWIW I can't reproduce the warning even with CONFIG_NF_CONNTRACK=n.

Maybe the extern declarations should be in include/linux/filter.h
anyways? Might be cleaner. WDYT?

> Otherwise, for the series:
> Acked-by: Kumar Kartikeya Dwivedi <memxor@...il.com>

Thanks!

Daniel