I have a linux box with two interfaces and a ppp
connection.  I routinely connect to a commercial intranet
via ppp.  I have a local net for which I have a static
(private) IP address.  I am also connected to RoadRunner
which requires DHCP nic configuration.  Roadrunner and the
ppp intranet both use split DNS configurations, i.e. DNS
resolution from the root down will not yield correct
information for inside these intranets.  In addition, I have
a private network.  To handle this I configure a local
nameserver which is a secondary to the ppp intranet servers,
and forwards to the Roadrunner servers.

  dhcpcd and pump both overwrite /etc/resolv.conf directly
from the binaries which prevents me from disabling the
behavior.  dhcpcd at least uses /etc/dhcpcd/resolv.conf
whereas pump does not.  They should allow this behavior to
be suppressed.