low pending handshake limit

["Moritz Wanzenböck" <moritz.wanzenboeck@linbit.com>]

Hi all,

I'm currently working on enabling TLS support for DRBD, so I'm very 
keen to use the handshake infrastructure. During testing I noticed that 
the allowed number of pending handshakes is quite low. This seems to 
stem from the following calculation:

 /*
  * Arbitrary limit to prevent handshakes that do not make
  * progress from clogging up the system. The cap scales up
  * with the amount of physical memory on the system.
  */
 si_meminfo(&si);
 tmp = si.totalram / (25 * si.mem_unit);
 hn->hn_pending_max = clamp(tmp, 3UL, 50UL);

Which, for the typical VMs I use for testing (1Gi RAM), ends up being 
just 3 handshakes. The limits in general seem too low also in the best 
case. If a node just booted, and would start connecting to all 
configured DRBD devices, we could easily hit even the upper limit of 50.

Also the calculation used doesn't seem to make too much sense to me. It 
allows more handshakes when using a smaller page size?

Would it be possible to increase the number of pending handshakes?

Best regards,
Moritz