Re: nfsrdma broken on 2.6.34-rc1?

[Jason Gunthorpe <jgunthorpe-ePGOBjL8dl3ta4EC/59zMFaTQe2KTcn/@public.gmane.org>]

On Mon, Mar 29, 2010 at 12:01:07PM -0700, Roland Dreier wrote:
>  > > The rdma_cm might be able to support this if the port space were separated based
>  > > on the address family, depending on how PS IB ends up.
>  > 
>  > I think separate port spaces is the correct solution.
> 
> This gets a bit tricky -- for normal IP stuff, there's the "bindv6only"
> sysctl (and the IPV6_V6ONLY socket option).  Without that, you can't
> bind an IPv4 socket to the same port as an IPv6 socket, since the IPv6
> socket will accept IPv4 connections via an v4->v6 mapped address.  (You
> can look at inet_csk_bind_conflict() to see the full complexity of the
> checking done when binding an IPv4 socket)

Yeah, exactly, it is very complex and there is a real need for
things pretending to be IP to capture all this subtlety. The details
can't just be skipped over, people will notice :(

Though, I'm also not entirely certain that NFS-RDMA is right to bind
to both AFs, generally speaking on Linux for a multi-protocol app you
only want to bind to v6 addresses.. Or is it using IPV6_V6ONLY or alike?

> I wonder what the right way from the RDMA CM to stay close to Linux
> sockets semantics without adding too much horror is.  (Adding Jason to
> the CC list since he usually has an opinion about things like this :)

Clearly the best way is to figure out some way to work with the
existing routines in the kernel. This stuff is complex and duplicating
all of it in rdma_cm would be annoying..

To match the semantics each CM ID would still register to one SID but
an incoming connection request on a v4 PF SID could be matched to a v6
SID, etc.

I don't think new port spaces in the API are desirable.

Jason
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