Re: RDMA subsystem namespace related questions (was Re: Finding the namespace of a struct ib_device)

[Leon Romanovsky <leon@kernel.org>]

On Wed, Oct 07, 2020 at 04:38:45PM +0800, Ka-Cheong Poon wrote:
> On 10/6/20 8:46 PM, Jason Gunthorpe wrote:
> > On Tue, Oct 06, 2020 at 05:36:32PM +0800, Ka-Cheong Poon wrote:
> >
> > > > > > Kernel modules should not be doing networking unless commanded to by
> > > > > > userspace.
> > > > >
> > > > > It is still not clear why this is an issue with RDMA
> > > > > connection, but not with general kernel socket.  It is
> > > > > not random networking.  There is a purpose.
> > > >
> > > > It is a problem with sockets too, how do the socket users trigger
> > > > their socket usages? AFAIK all cases originate with userspace
> > >
> > > A user starts a namespace.  The module is loaded for servicing
> > > requests.  The module starts a listener.  The user deletes
> > > the namespace.  This scenario will have everything cleaned up
> > > properly if the listener is a kernel socket.  This is not the
> > > case with RDMA.
> >
> > Please point to reputable code in upstream doing this
>
>
> It is not clear what "reputable" here really means.  If it just
> means something in kernel, then nearly all, if not all, Internet
> protocols code in kernel create a control kernel socket for every
> network namespaces.  That socket is deleted in the per namespace
> exit function.  If it explicitly means listening socket, AFS and
> TIPC in kernel do that for every namespaces.  That socket is
> deleted in the per namespace exit function.
>
> It is very common for a network protocol to have something like
> this for protocol processing.  It is not clear why RDMA subsystem
> behaves differently and forbids this common practice.  Could you
> please elaborate the issues this practice has such that the RDMA
> subsystem cannot support it?

Just curious, are we talking about theoretical thing here or do you
have concrete and upstream ULP code to present?

Thanks

>
>
>
> --
> K. Poon
> ka-cheong.poon@oracle.com
>
>