linux-kernel - Re: [PATCH net-next 3/4] bpf: add support for persistent maps/progs

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Date:	Thu, 22 Oct 2015 14:35:14 -0500
From:	ebiederm@...ssion.com (Eric W. Biederman)
To:	Daniel Borkmann <daniel@...earbox.net>
Cc:	Alexei Starovoitov <ast@...mgrid.com>,
	Hannes Frederic Sowa <hannes@...essinduktion.org>,
	davem@...emloft.net, viro@...IV.linux.org.uk, tgraf@...g.ch,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	Alexei Starovoitov <ast@...nel.org>
Subject: Re: [PATCH net-next 3/4] bpf: add support for persistent maps/progs

Daniel Borkmann <daniel@...earbox.net> writes:

> On 10/20/2015 08:56 PM, Eric W. Biederman wrote:
> ...
>> Just FYI:  Using a device for this kind of interface is pretty
>> much a non-starter as that quickly gets you into situations where
>> things do not work in containers.  If someone gets a version of device
>> namespaces past GregKH it might be up for discussion to use character
>> devices.
>
> Okay, you are referring to this discussion here:
>
>   http://thread.gmane.org/gmane.linux.kernel.containers/26760

That is a piece of it.  It is an old old discussion (which generally has
been handled poorly).  For the forseeable future device namespaces have
a firm NACK by GregKH.  Which means that dynamic character device based
interfaces do not work in containers.  Which means if you are not
talking about physical hardware, character devices are a poor fit.

Making a character based interface for eBPF not workable.

Eric

p.s.  There are plenty of reasons (even if privilege remains a
      requirement) to ask how can this functionality be used in a
      container.  If for no other reason than sandboxing privileged
      applications is typically a good idea.
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