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

[Caitlin Bestler]

Expanding slightly on Hal's response, the correct method to correlate
an *IP* address with a device is to consult the *IP* routing tables.

While there are exceptions where you want to control the local
address, it is far more common that you need to reach a remote
address (or be reachable from a remote address), as pointed out
in Roland's response. So the general algorithm is to check the
local routing tables to see what device would be the first hop.
>From there it is merely a matter of connecting the device
declared for purposes of IP routing with the device that provides
RDMA services.

As for the differences between *IP* and *IB* addresses, that
boils down to a determination of who is responsible for reconciling
the difference: the network stack or the application.


 
On 6/20/05, Kevin Reilly <kjreilly at us.ibm.com> wrote:
> 
> 
> 
> 
> Maybe somebody could help me understand the proper way to map between an IP
> address assigned to a port to the
> "device  name" and "port number" in the gen2 architecture.  If I have an IP
> address can I map it to a name that i get back
> from ibv_get_device_name() or pass to ibv_open_device().
>      Here  is  the  problem.  Let's  say  there  is  a  subsystem that used
> heartbeating over IP interfaces to ascertain the adapters
> and  ports  state,  up  or  down.   The  data  actively  maintained be this
> heartbeating subsystem is used by a job scheduler that
> desires  to  only schedule tasks on HCAs that are UP and have active ports.
> The job scheduler does not want to launch jobs
> on adapters that are broken, not connected to a switch or not configured.
>       The  job  scheduler  needs a way to map an IP address into a name and
> port number sitable to be passed to the job to
> use   when   ibv_open_device()   is  called  or  to  match  the  output  of
> ibv_get_device_name().
> 
> Kevin J. Reilly
> STSM, HPC Architecture
> -Federation/HPS  Chief Engineer
> -HPC interconnect architect
> (office) 845-433-7976  (tieline) 8-293-7976
> 
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