Re: RDMA/CM and multiple QPs

[Sagi Grimberg <sagig-LDSdmyG8hGV8YrgS2mwiifqBs+8SCbDb@public.gmane.org>]

On 9/10/2015 4:29 PM, Christoph Hellwig wrote:
> On Thu, Sep 10, 2015 at 12:50:33PM +0300, Sagi Grimberg wrote:
>>> What I'm more interested in is a way to tell the CM that I only
>>> want routes that are using this ib_device that I got from the first
>>> lookup as all others are useless for me.
>>>
>>
>> I'm not sure I understand what you are aiming for? if you connect to
>> a single address multiple times you will get the same device because
>> it is the same route right?
>
> In testing I do get the same all the time, but I don't see anything that
> gurantees that in code or documentation.

I think it depends on the routing table.

> Think about the case where the routing changes between the calls,
> or we're using multipath TCP for example.

That indeed can happen, in fact, if a bond changes its primary iface
you can see different devices.

But I don't think you should support that anyway. Just fail the session
if you see different devices. I don't think that forcing the CM to a
single device would help you as they will probably fail anyway.

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