[openib-general] Port reuse issue for rdma_cm/iwarp

[Caitlin Bestler]

openib-general-bounces at openib.org wrote:
> Hi,
>  We are facing a problem while running back-to-back
> applications using the same port number for rdma_cm over
> iwarp (Ammasso). The port seems to be busy for about 60
> seconds after each disconnect.
> 
> The first execution finishes without any problems or errors.
> When the execution is repeated immediately, we see a
> RDMA_CM_EVENT_REJECTED event on the active connect side.
> However, if we use a different port or if we include a delay
> of more than 60 seconds between the runs, we do not see this problem.
> 
> Is this a known issue? Is there anyway to force a immediate
> reuse of the port?
> 

TCP restricts prompt re-use of the same Source/Destination
Address/Port pair while old traffic could still be in-flight.
This is generally not an issue because prompt re-use of the
exact four tuple is rare.

Is there a special reason why your application needs to
reuse the same port from the active side? If the port number
is being used to identify the rank, could private data be
used instead?