[openib-general] [PATCH] IB_CM: Limit the MRA timeout

[Michael S. Tsirkin]

Quoting r. Sean Hefty <mshefty at ichips.intel.com>:
> Subject: Re: [PATCH] IB_CM: Limit the MRA timeout
> 
> Michael S. Tsirkin wrote:
> > For remote cm timeout and service timeout this makes sense - they seem
> > currently mostly taken out of the blue on implementations I've seen.
> > 
> > But since the packet lifetime comes from the SM, it actually has a chance
> > to reflect some knowledge about the network topology.
> > And since we haven't see any practical issues with packet life time yet -
> > maybe a different paremeter for that, with a higher limit?
> 
> I guess the question is how much do we trust the timeout values sent in a CM 
> MAD.  (It's hard for me to imagine a network that requires a 2.5 hour packet 
> life time.  IB to space?)  Having separate timeout values may make sense, but my 
> expectation is for the remote cm timeout and service timeout values to be 
> greater than the packet life time.
> 
> If we go with separate values, then is there a reason not to have separate 
> defaults for each one?  My preference is to try to limit the number of values.

The way I see it, we trust e.g. the SRP target anyway.
So I'm not sure there's much value in range-checking everything.
The only reason we are touching this is because we see a
target reporting an obviously broken service timeout value in MRA -
in the hours range.

So, maybe start small and just use Ishai's patch (with default
set to several seconds or so), and wait with the fix till a problem
surfaces?

-- 
MST