linux-kernel - Re: Add PGM protocol support to the IP stack

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Date:	Mon, 22 Mar 2010 17:36:09 +0100
From:	Andi Kleen <andi@...stfloor.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
Cc:	Andi Kleen <andi@...stfloor.org>,
	David Miller <davem@...emloft.net>, netdev@...r.kernel.org,
	linux-kernel@...r.kernel.org
Subject: Re: Add PGM protocol support to the IP stack

On Mon, Mar 22, 2010 at 09:20:42AM -0500, Christoph Lameter wrote:
> On Fri, 19 Mar 2010, Andi Kleen wrote:
> 
> > Christoph Lameter <cl@...ux-foundation.org> writes:
> > >
> > > I know about the openpgm implementation. Openpbm does this at the user
> > > level and requires linking to a library. It is essentially a communication
> > > protocol done in user space. It has privilege issues because it has to
> > > create PGM packets via a raw socket.
> >
> > That seems like a poor reason alone to put something into the kernel
> > Perhaps you rather need some way to have unpriviledged raw sockets?
> 
> Not the only reason. There are also performance implications. NAKing and
> other control messages from user space are a pain and the available
> implementations add numerous threads just to control the timing of control
> messages and the expiration of data etc. Its difficult to listen to a PGM
> port from user space. You have to get all messages for the PGM protocol
> and then filter in each process.

Ok that sounds like a good reason to have a kernel protocol.
Thanks.

Multicast reliable kernel protocols are somewhat new, I guess one
would need to make sure to come up with a clean generic interface 
for them first.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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