netdev - Re: [PATCH net-next 1/2] netlink: introduce NLA_POLICY_MAX

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Message-ID: <2f528f1a320c55fdc7f3be55095c1f0eacee1032.camel@sipsolutions.net>
Date:   Thu, 27 Oct 2022 22:36:33 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Jakub Kicinski <kuba@...nel.org>, Florian Westphal <fw@...len.de>
Cc:     netdev@...r.kernel.org, netfilter-devel@...r.kernel.org,
        Eric Dumazet <edumazet@...gle.com>,
        "David S. Miller" <davem@...emloft.net>,
        Paolo Abeni <pabeni@...hat.com>
Subject: Re: [PATCH net-next 1/2] netlink: introduce NLA_POLICY_MAX_BE

On Thu, 2022-10-27 at 13:31 -0700, Jakub Kicinski wrote:
> On Mon,  5 Sep 2022 12:09:36 +0200 Florian Westphal wrote:
> >  		struct {
> >  			s16 min, max;
> > +			u8 network_byte_order:1;
> >  		};
> 
> This makes the union 64bit even on 32bit systems.
> Do we care? Should we accept that and start using
> full 64bits in other validation members?
> 
> We can quite easily steal a bit elsewhere, which
> I reckon may be the right thing to do, but I thought
> I'd ask.

Personally, I guess I might have preferred to steal a bit out of the
type or validation_type. We have a lot of these structures... and I'd
guess 32-bit systems are typically more memory constrained.

In fact we could easily just have three extra types NLA_BE16, NLA_BE32
and NLA_BE64 types without even stealing a bit? We already have
NLA_MSECS which is basically the same as NLA_U64 but just with the
additional semantic information, for example.

johannes