/etc/dhcp/dhclient-enter-hooks.d/samba is in samba-common 2:3.6.25-0ubuntu0.12.04.10.
This file is owned by root:root, with mode 0o777.
It is a symlink to /etc/dhcp/dhclient-enter-hooks.d/../../dhcp3/dhclient-enter-hooks.d/samba