Before the switch to WIDE dhcp6c , adding and deleting nameservers and search domains from the lease was done by isc-dhcp-client dhclient-script. This has custom hooks (make_resolv_conf and a post script) that do the necessary updating of nameservers via vyos-hostsd.
Since switching to WIDE dhcp6c for T421 these scripts aren't ran any more. WIDE dhcp6c does support running scripts, but after comparing the two, they aren't compatible, so it isn't a simple case of running the existing isc-dhcp scripts with wide.
most notably from 'man dhcp6c':
Configuration Script
When receives a reply message, it will invoke a supplementary configuration script specified in the dhcp6c.conf5 file. The daemon will provide the script with configuration parameters as environment variables, which include:
REASON
The reason why the script is invoked. As of this writing, the value is always "NBI" and thus meaningless.
new_domain_name_servers
A list of available DNS servers, each of which is an IPv6 numeric address and is separated by a white space character.
new_domain_name
A list of DNS names, which provides DNS name search path.
new_ntp_servers
A list of available NTP servers, each of which is an IPv6 numeric address and is separated by a white space character.
new_sip_servers
A list of available SIP server addresses, each of which is an IPv6 numeric address and is separated by a white space character.
new_sip_name
A list of SIP server domain names.
new_nis_servers
A list of available NIS server addresses, each of which is an IPv6 numeric address and is separated by a white space character.
new_nis_name
A list of NIS domain names.
new_nisp_servers
A list of available NIS+ server addresses, each of which is an IPv6 numeric address and is separated by a white space character.
new_nisp_name
A list of NIS+ domain names.
new_bcmcs_servers
A list of available BCMCS server addresses, each of which is an IPv6 numeric address and is separated by a white space character.
new_bcmcs_name
A list of BCMCS server domain names.So the critical differences are:
- REASON is never set to the real reason (isc-dhcp does set it)
- new_domain_name_servers is used for v6, whereas isc-dhcp uses it for v4 and has a separate new_dhcp6_name_servers variable for v6
- new_domain_name is the equivalent of isc-dhcp new_dhcp6_domain_search
So to fix this with wide-dhcp6, we'd need to make a completely new script that does the same things the existing pre/post hooks for dhclient-script do, but suitable for wide.
(if anyone wants to start working on this, note there is a pending vyos-1x PR for the whole vyos-hostsd/dhclient hooks so please wait until it's merged)