netdev - Re: [PATCH 2/2] net: Implement SO_PASSCGROUP to enable passing cgroup path

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Message-ID: <1397603340.19767.362.camel@willson.li.ssimo.org>
Date:	Tue, 15 Apr 2014 19:09:00 -0400
From:	Simo Sorce <ssorce@...hat.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Vivek Goyal <vgoyal@...hat.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	cgroups@...r.kernel.org,
	Network Development <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>, Tejun Heo <tj@...nel.org>,
	lpoetter@...hat.com, kay@...hat.com, dwalsh@...hat.com
Subject: Re: [PATCH 2/2] net: Implement SO_PASSCGROUP to enable passing
 cgroup path

On Tue, 2014-04-15 at 14:53 -0700, Andy Lutomirski wrote:
> On Tue, Apr 15, 2014 at 2:15 PM, Vivek Goyal <vgoyal@...hat.com> wrote:
> > This patch implements socket option SO_PASSCGROUP along the lines of
> > SO_PASSCRED.
> >
> > If SO_PASSCGROUP is set, then recvmsg() will get a control message
> > SCM_CGROUP which will contain the cgroup path of sender. This cgroup
> > belongs to first mounted hierarchy in the sytem.
> >
> > SCM_CGROUP control message can only be received and sender can not send
> > a SCM_CGROUP message. Kernel automatically generates one if receiver
> > chooses to receive one.
> >
> > This works both for unix stream and datagram sockets.
> >
> > cgroup information is passed only if either the sender or receiver has
> > SO_PASSCGROUP option set. This means for existing workloads they should
> > not see any significant performance impact of this change.
> 
> This is odd.  Shouldn't an SCM_CGROUP cmsg be generated when the
> receiver has SO_PASSCGROUP set and the sender passes SCM_CGROUP to
> sendmsg?

What would be the point ?

Simo.


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