linux-kernel - Re: [PATCH 0/2] constify nf_hook

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Message-ID: <20170729094136.GG28392@breakpoint.cc>
Date:   Sat, 29 Jul 2017 11:41:36 +0200
From:   Florian Westphal <fw@...len.de>
To:     Julia Lawall <julia.lawall@...6.fr>
Cc:     Florian Westphal <fw@...len.de>,
        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

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.

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.