[openib-general] Re: [PATCH] CMA and iWARP

[Tom Tucker]

On Tue, 2006-01-24 at 08:02 -0800, Roland Dreier wrote:
>     Caitlin> It is important to separate two issues here: L2-L3
>     Caitlin> coordination and L4 coordination.
> 
>     Caitlin> The patches that Tom recently posted address the L2-L3
>     Caitlin> coordination.  They ensure that the TCP/IP stack used by
>     Caitlin> the RNIC is consistent in its L2-L3 configuration with
>     Caitlin> the host stack. For example, it will route packets to the
>     Caitlin> same destination IP address the same way as the host
>     Caitlin> stack, use the same MAC addresses for first hops, etc.
> 
> But the patches don't provide full L2 coordination.  For example if I
> install a netfilter rule that discards packets from a particular
> source MAC (a completely, 100% L2 notion), the RNIC will still happily
> accept connections from that MAC, right?

The intended behavior is to provide "full coordination". For the example
you give, I would expect that rdma_resolve_addr would fail due to to a
timeout waiting for an ARP reply. 

> 
>     Caitlin> Those will be compicated give and takes. There is no
>     Caitlin> reason to hold up the L2-L3 work because of it. If it
>     Caitlin> were, then SDP/IB should have been deferred until
>     Caitlin> complete consistency was achieved. Updating one step at a
>     Caitlin> time makes more sense.
> 
> SDP/IB is not in the upstream kernel.  And I agree that there are many
> issues with respect to network stack integration to work out before
> SDP is suitable for merging.
> 
>  - R.
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