netdev - Re: [PATCH bpf-next v7 07/13] net: netfilter: Add kfuncs to allocate and insert CT

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Date:   Sat, 23 Jul 2022 09:50:50 +0200
From:   Pablo Neira Ayuso <pablo@...filter.org>
To:     Kumar Kartikeya Dwivedi <memxor@...il.com>
Cc:     bpf@...r.kernel.org, Lorenzo Bianconi <lorenzo@...nel.org>,
        Alexei Starovoitov <ast@...nel.org>,
        Andrii Nakryiko <andrii@...nel.org>,
        Daniel Borkmann <daniel@...earbox.net>,
        Florian Westphal <fw@...len.de>,
        Jesper Dangaard Brouer <brouer@...hat.com>,
        Toke Høiland-Jørgensen <toke@...hat.com>,
        netdev@...r.kernel.org, netfilter-devel@...r.kernel.org
Subject: Re: [PATCH bpf-next v7 07/13] net: netfilter: Add kfuncs to allocate
 and insert CT

On Fri, Jul 22, 2022 at 11:39:49AM +0200, Kumar Kartikeya Dwivedi wrote:
> On Fri, 22 Jul 2022 at 11:02, Pablo Neira Ayuso <pablo@...filter.org> wrote:
> >
> > Hi,
> >
> > On Thu, Jul 21, 2022 at 03:42:39PM +0200, Kumar Kartikeya Dwivedi wrote:
> > > diff --git a/include/net/netfilter/nf_conntrack_core.h b/include/net/netfilter/nf_conntrack_core.h
> > > index 37866c8386e2..83a60c684e6c 100644
> > > --- a/include/net/netfilter/nf_conntrack_core.h
> > > +++ b/include/net/netfilter/nf_conntrack_core.h
> > > @@ -84,4 +84,19 @@ void nf_conntrack_lock(spinlock_t *lock);
> > >
> > >  extern spinlock_t nf_conntrack_expect_lock;
> > >
> > > +/* ctnetlink code shared by both ctnetlink and nf_conntrack_bpf */
> > > +
> > > +#if (IS_BUILTIN(CONFIG_NF_CONNTRACK) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF)) || \
> > > +    (IS_MODULE(CONFIG_NF_CONNTRACK) && IS_ENABLED(CONFIG_DEBUG_INFO_BTF_MODULES) || \
> > > +    IS_ENABLED(CONFIG_NF_CT_NETLINK))
> >
> > There must be a better way to do this without ifdef pollution?
> >
> > Could you fix this?
> 
> I can just remove the ifdefs completely. The first part of the ifdef
> is the correct way to detect BPF support for nf_conntrack, the second
> is for ct netlink. These are the only two users. But it's not a lot of
> code, so until it grows too much we can compile it unconditionally.

I would suggest to compile in these small functions unconditionally.

> Or do you have anything else in mind (like defining a macro for the
> bpf one and making the ifdef look less ugly)?

it's the ifdef pollution that it would be good to avoid IMO.