netdev - Re: [PATCH v4 for-next 00/12] Add network namespace support in the RDMA-CM

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Message-ID: <20150603195325.GC7902@obsidianresearch.com>
Date:	Wed, 3 Jun 2015 13:53:25 -0600
From:	Jason Gunthorpe <jgunthorpe@...idianresearch.com>
To:	Or Gerlitz <gerlitz.or@...il.com>
Cc:	Doug Ledford <dledford@...hat.com>,
	Haggai Eran <haggaie@...lanox.com>,
	Or Gerlitz <ogerlitz@...lanox.com>,
	"linux-rdma@...r.kernel.org" <linux-rdma@...r.kernel.org>,
	Linux Netdev List <netdev@...r.kernel.org>,
	Liran Liss <liranl@...lanox.com>,
	Guy Shapiro <guysh@...lanox.com>,
	Shachar Raindel <raindel@...lanox.com>,
	Yotam Kenneth <yotamke@...lanox.com>
Subject: Re: [PATCH v4 for-next 00/12] Add network namespace support in the
 RDMA-CM

On Wed, Jun 03, 2015 at 10:05:34PM +0300, Or Gerlitz wrote:

> Indeed the DHCP story isn't working there and to get DHCP work
> something has to be done. But this issue can't serve for blocking the
> existing UAPI and introduce regression to working systems.

It is not DHCP that concerns me, it is the fact we can't combine net
namespaces, RDMA-CM and duplicate GUID IPoIB children together without
adding hacks to the kernel. Searching netdevs by IP is a hack.

I'm mostly fine with it as an optional capability, similar to macvlan,
I just don't see how to cleanly integrate it with RDMA CM and
namespaces. And I don't see what RDMA CM is supposed to do when
it hits this case.

So, any ideas that don't involve the searching for IP hack??

[And yes, as discussed with Haggie, it is not the worst hack in the
 world, and maybe we can live with it, but lets understand the trade
 offs carefully]

Also, now that this has been brought up, I think you need to make a
patch to fix the IPv6 SLAAC breakage this caused. It looks trivial to
modify addrconf_ifid_infiniband to return error if the IPoIB child is
sharing a guid. It was not good at all to push the child patches
forward to 3.6/3.7 if you knew that IPv6 SLAAC was broken by them.

Jason
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