linux-kernel - Re: [PATCH] sysctl: add support for poll()

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Message-ID: <m1ipsoco8r.fsf@fess.ebiederm.org>
Date:	Thu, 02 Jun 2011 07:16:36 -0700
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Alan Cox <alan@...rguk.ukuu.org.uk>
Cc:	Kay Sievers <kay.sievers@...y.org>,
	Lucas De Marchi <lucas.demarchi@...fusion.mobi>,
	linux-kernel@...r.kernel.org, Nick Piggin <npiggin@...nel.dk>,
	Al Viro <viro@...iv.linux.org.uk>,
	Christoph Hellwig <hch@....de>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Howells <dhowells@...hat.com>,
	"Serge E. Hallyn" <serge.hallyn@...onical.com>,
	Daniel Lezcano <daniel.lezcano@...e.fr>,
	Jiri Slaby <jslaby@...e.cz>,
	Greg Kroah-Hartman <gregkh@...e.de>,
	James Morris <jmorris@...ei.org>
Subject: Re: [PATCH] sysctl: add support for poll()

Alan Cox <alan@...rguk.ukuu.org.uk> writes:

>> Host names are dynamic, can change during system runtime by dhcp or
>> similar setups, or just get changed by the user.
>
> I don't actually see what this has to do with utsname. uname historically
> defined nodename as "name within an implementation-defined communications
> network" and actually tended to be the UUCP name. Modern SuS says "`the
> name of the node of the communications network to which this node is
> attached, if any"

>
> The latter unfortunately makes no sense anyway and is a fine example of
> standards body cluelessness as name mapping on IP networks is not one
> name per host, and also because the standard doesn't require the fields
> in the struct are long enough to hold a DNS name!
>
> (Indeed in its usual head up backside manner its technically valid to
> define
>
> 	char nodename[1];
>
> and have only \0 as a valid reply)

However we have conveniently defined sethostname and gethostname to use
the same state in the kernel, as uname.  I believe at least one of these
interfaces that map to the same storage in linux has a usable size
guaranteed by all of the implementations.

Eric


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