[openib-general] mapping between IP address and device name

[Libor Michalek]

On Mon, Jun 20, 2005 at 08:40:47PM -0700, Roland Dreier wrote:
>     Kevin> Maybe somebody could help me understand the proper way to
>     Kevin> map between an IP address assigned to a port to the "device
>     Kevin> name" and "port number" in the gen2 architecture.  If I
>     Kevin> have an IP address can I map it to a name that i get back
>     Kevin> from ibv_get_device_name() or pass to ibv_open_device().
> 
> It _is_ valid to ask, for a given remote IP address, which network
> interface will be used to reach it based on the local host's routing
> configuration.
> 
> In the IB world, we can hope that the network interface chosen by the
> route table is an IPoIB device.  From the IPoIB device, we can work
> backwards to get a local IB port. For example the network device's
> hardware address contains the associated port GID, and by searching
> the GID tables of all the known IB devices, we can find which port has
> that GID.
> 
> There was some discussion a while ago about an "IB address
> translation" service proposed by the Voltaire crew, which would
> encapsulate some of this.  However, we didn't make much progress
> towards a good API design, and the discussion fizzled out.

  Also, if you want to look at an example of how this is done using the
IPoIB network device and Linux routing code you can look here:

  src/linux-kernel/infiniband/ulp/sdp/sdp_link.[ch] 

The SDP code needed this functionality, so I put together a fairly simple
version that's private to SDP, as MST pointed out locking is still missing
from the code. Eventually this type of code should become a central
service, since there's a number of modules that would want this info.

-Libor