Hello Pavel:

We were able to reproduce it under Fedora 23.  Ubuntu and Centos 7 seem to be immune.  We have an alternative patch that is under review and can forward it to you for testing once reviewed.

Our testing here with 4.3.3 under Fedora does confirm an eventual inability to make further OMAPI connections, but the server does continue to service DHCP clients.  The code limits the number of open FDs to 200.  As 4.2* is EOL,  we did not test it, though same patch could be applied to it.

Regards,

Thomas Markwalder
ISC Sofware Engineering