Turns out this is something directly in klibc in the case of xenial: since xenial is not yet using isc-dhcp for IPv4 DHCP, since that was deemed too intrusive a change for xenial.
In other words, while DHCPv6 is done via isc-dhcp, DHCPv4 is done via ipconfig (klibc); which will need to be fixed to follow the same logic as isc-dhcp w.r.t DOMAINSEARCH handling.
In general, I think having DOMAINSEARCH contain the existing DNS domain if it's not otherwise set by the DHCP server is sensible.
I set the xenial task to High since it might actually impact a lot of people, but it's not as high for artful/zesty given that isc-dhcp is used instead (still ought to land there since people might want to use ipconfig on their own, etc.).
Turns out this is something directly in klibc in the case of xenial: since xenial is not yet using isc-dhcp for IPv4 DHCP, since that was deemed too intrusive a change for xenial.
In other words, while DHCPv6 is done via isc-dhcp, DHCPv4 is done via ipconfig (klibc); which will need to be fixed to follow the same logic as isc-dhcp w.r.t DOMAINSEARCH handling.
In general, I think having DOMAINSEARCH contain the existing DNS domain if it's not otherwise set by the DHCP server is sensible.
I set the xenial task to High since it might actually impact a lot of people, but it's not as high for artful/zesty given that isc-dhcp is used instead (still ought to land there since people might want to use ipconfig on their own, etc.).