That patch I attached is of course nonsense, but there are some others 
in the wild trying to solve the same problem, for example:

https://community.ubnt.com/ubnt/attachments/ubnt/EdgeMAX/29126/1/bind_fb_iface_4.2.4-P2_1.patch
from
https://community.ubnt.com/t5/EdgeMAX/WAN-dropped-DHCP-renew-fixes-it/m-p/783774

or

https://github.com/greearb/dhcp-ct/commit/8cf011981ce6e99f7ef891b24c4a6f637686c13f
https://github.com/greearb/dhcp-ct/commit/d642491539b6a0fc8b6c14eb9169755e172ddab2

see also:
https://lists.isc.org/pipermail/dhcp-hackers/2014-December/002103.html
https://lists.isc.org/pipermail/dhcp-users/2014-April/017835.html
https://bugzilla.redhat.com/show_bug.cgi?id=1177351

With regards,
--
Jiri