Hello Michael:

The section of code you reported actually comes from within the BIND9 libraries.  The code in question was subsequently changed in BIND9 9.11 and no longer uses get_udpsocket().  Our next feature release, ISC DHCP 4.4.0 is due out early Q1 of 2018 and will ship with BIND9 9.12 libraries, thus eliminating your issue.

Thank you for bringing this issue to our attention.

Regards,

Thomas Markwalder
ISC Software Engineering