linux-kernel - Re: [RFC][PATCH 0/9] Make containers kernel objects

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Date:   Tue, 23 May 2017 10:17:26 -0500
From:   ebiederm@...ssion.com (Eric W. Biederman)
To:     David Howells <dhowells@...hat.com>
Cc:     Aleksa Sarai <asarai@...e.de>,
        James Bottomley <James.Bottomley@...senPartnership.com>,
        trondmy@...marydata.com, mszeredi@...hat.com,
        linux-nfs@...r.kernel.org, jlayton@...hat.com,
        Linux Containers <containers@...ts.linux-foundation.org>,
        linux-kernel@...r.kernel.org, viro@...iv.linux.org.uk,
        linux-fsdevel@...r.kernel.org, cgroups@...r.kernel.org
Subject: Re: [RFC][PATCH 0/9] Make containers kernel objects

David Howells <dhowells@...hat.com> writes:

> Eric W. Biederman <ebiederm@...ssion.com> wrote:
>
>> > As an example, I could set up a client machine with two ethernet ports,
>> > set up two DNS+NFS servers, each of which think they're called "foo.bar"
>> > and attach each server to a different port on the client machine.  Then I
>> > could create a pair of containers on the client machine and route the
>> > network in each container to a different port.  Now there's a problem
>> > because the names of the cached DNS records for each port overlap.
>> 
>> Please look at ip netns add.
>
> 	warthog>man ip | grep setns
> 	warthog1>

Not setns netns


>> It does solve this in userspace rather simply.
>
> Ummm...  How?  The kernel DNS resolver is not namespace aware.

But it works fine if called in the proper context and we have a defacto
standard for where to put all of the files (the tricky part) if you are
dealing with multiple network namespaces simultaneously.

Eric