netdev - Re: [PATCH net-next] ipv6: eliminate ndisc_ops_is

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Message-ID: <CANP3RGd3HNMQi=_gFVjp4JiWxUk3u4V8Xyb5Gy=2W9AZjOKH2g@mail.gmail.com>
Date: Thu, 1 Aug 2024 09:02:22 -0700
From: Maciej Żenczykowski <maze@...gle.com>
To: Paolo Abeni <pabeni@...hat.com>
Cc: Linux Network Development Mailing List <netdev@...r.kernel.org>, "David S . Miller" <davem@...emloft.net>, 
	Eric Dumazet <edumazet@...gle.com>, Jakub Kicinski <kuba@...nel.org>, David Ahern <dsahern@...nel.org>, 
	YOSHIFUJI Hideaki / 吉藤英明 <yoshfuji@...ux-ipv6.org>
Subject: Re: [PATCH net-next] ipv6: eliminate ndisc_ops_is_useropt()

On Thu, Aug 1, 2024 at 6:54 AM Paolo Abeni <pabeni@...hat.com> wrote:
>
> On 7/30/24 02:30, Maciej Żenczykowski wrote:
> > as it doesn't seem to offer anything of value.
> >
> > There's only 1 trivial user:
> >    int lowpan_ndisc_is_useropt(u8 nd_opt_type) {
> >      return nd_opt_type == ND_OPT_6CO;
> >    }
> >
> > but there's no harm to always treating that as
> > a useropt...
>
> AFAICS there will be an user-visible difference, as the user-space could
> start receiving "unexpected" notification for such opt even when the
> kernel is built with CONFIG_6LOWPAN=n.
>
> The user-space should ignore unknown/unexpected notification,so it
> should be safe, but I'm a bit unsettled by the many 'should' ;)

We've added new options to this list in the past.  Even going so far
as shipping those changes via LTS... So IMHO this doesn't seem like a
real concern.  Also the option is very unlikely to be present in
normal non 6lowpan environments.

> Cheers,
>
> Paolo
>