[openib-general] [PATCH ] RFC IB/cm do not track remote QPN in timewait state

[Sean Hefty]

Michael S. Tsirkin wrote:
> And so can RTU, in which case again QP will be in RTR. So it seems
> lost CM packets aren't protected by timewait.

Maybe we just try to deal with this the best that we can and make the HCA driver 
responsible for not re-allocating QPs for a duration of local_ack_timeout once 
they've entered RTS.

If connections are made through the IB CM, it seems unlikely that stale packets 
will float around the subnet longer than it takes to establish a new connection. 
  We just need to be able to detect stale connections, which requires that users 
use the CM when connecting.

> At least in case of mthca, I think we do have the last PSN.
> So I guess we could have a special wildcard PSN value that let's low
> level driver select it. What would a good value for the PSN be?

I'm not sure about this idea now.  A random starting PSN is easy.  How much 
better off are we trying to be clever?

Btw, have you been able to determine why your patch leads to a crash under 
stress?  It looks to me like it would work.

- Sean