netdev - Re: [PATCH 0/2] constify nf_hook

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Date:   Sat, 29 Jul 2017 11:56:47 +0200 (CEST)
From:   Julia Lawall <julia.lawall@...6.fr>
To:     Florian Westphal <fw@...len.de>
cc:     Julia Lawall <julia.lawall@...6.fr>,
        linux-decnet-user@...ts.sourceforge.net, bhumirks@...il.com,
        kernel-janitors@...r.kernel.org,
        Pablo Neira Ayuso <pablo@...filter.org>,
        Jozsef Kadlecsik <kadlec@...ckhole.kfki.hu>,
        "David S. Miller" <davem@...emloft.net>,
        netfilter-devel@...r.kernel.org, coreteam@...filter.org,
        netdev@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 0/2] constify nf_hook_ops structures



On Sat, 29 Jul 2017, Florian Westphal wrote:

> Julia Lawall <julia.lawall@...6.fr> wrote:
> > On Sat, 29 Jul 2017, Florian Westphal wrote:
> > > From a quick glance I don't see why we can't e.g. constify
> > > nf_conntrack_l3/4_proto too. It is not going to be as simple
> > > as just placing const everywhere, but I see no requirement for
> > > having these writeable.
> >
> > I will take a look.
>
> Thanks.

For the protos, the functions nf_ct_l3proto_register and
nf_ct_l4proto_register_one update the nla_size field. I don't know how
many structures reach these functions.

julia

>
> nf_logger and nf_loginfo also look like constify candidates.
>
> If there is a way to add "const" qualifier to pointer-to-structs
> that are not modified this would good as well to have IMO, if just
> for purpose of documentation.  For instance:
>
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -1177,8 +1177,8 @@ void nf_conntrack_free(struct nf_conn *ct)
>  static noinline struct nf_conntrack_tuple_hash *
>  init_conntrack(struct net *net, struct nf_conn *tmpl,
>                const struct nf_conntrack_tuple *tuple,
> -              struct nf_conntrack_l3proto *l3proto,
> -              struct nf_conntrack_l4proto *l4proto,
> +              const struct nf_conntrack_l3proto *l3proto,
> +              const struct nf_conntrack_l4proto *l4proto,
>
>
> (its only passed as arg to a function that expects
> "const struct nf_conntrack_x *").
>
> I think we have several (also non-static helpers) that
> take "struct foo *" arg while they could use "const struct foo*"
> instead.
> --
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