linux-kernel - Re: [PATCH] vsprintf: do not append unset Scope ID to IPv6

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Message-ID: <CAHmME9qmdM6t8Gk6Ypw+OYFbYP7w4fRKT_44dKnmXbm93JF77g@mail.gmail.com>
Date:	Wed, 3 Feb 2016 22:14:22 +0100
From:	"Jason A. Donenfeld" <Jason@...c4.com>
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux@...musvillemoes.dk, andriy.shevchenko@...ux.intel.com,
	LKML <linux-kernel@...r.kernel.org>,
	Joe Perches <joe@...ches.com>
Subject: Re: [PATCH] vsprintf: do not append unset Scope ID to IPv6

On Wed, Feb 3, 2016 at 10:07 PM, Daniel Borkmann <daniel@...earbox.net> wrote:
> I don't see an "issue" here. I.e. if the developer requested to append 's'
> to the specifier, then it's expected to dump what is in the scope id, even
> if that is 0 meaning "unset" scope.
>
> It would be principle of least surprise -- I could imagine if not dumped,
> then a developer would check the source code to find out whether he did a
> mistake or it's expected behavior, just to make sure. That's what I would
> do probably.

Showing something that's "unset" seems counter-intuitive.

The idea here is to be able to printk a sockaddr_in6, and have it show
something that looks like what the user would naturally pass to
getaddrinfo(3), which is entirely complete.

However, I could be convinced that this kind of behavior belongs in
it's own flag. Maybe I'll cook up a flag for that instead.

>
> Is this causing a _real_ issue somewhere (I couldn't parse one out of your
> commit message other than 'it would be nice to have')?

Nice to have.