Is my dhcpcd.conf(5) valid?

[zacknewman]

I use dhcpcd(8) for both DHCP, DHCPv6-NA, and DHCPv6-PD. I also run my own recursive DNS server and NTP server. The only information I want dhcpcd(8) to control are the IP addresses for the interface and default routes. The below is my config:

noipv6rs
denyinterfaces !(ixl2)
allowinterfaces ixl2
script ""
link_rcvbuf 65536
interface ixl2
	duid
	iaid 0
	ia_na 0
	ia_pd 0/::/60 -
	ipv6rs
	nooption domain_name,domain_name_servers,domain_search,fqdn,host_name,interface_mtu,mtu,ntp_servers,time_offset,time_servers
	option rapid_commit
	persistent
	require dhcp_server_identifier
	static interface_mtu=1500
	static mtu=1500
	waitip 64

script "" is used to prevent dhcpcd from running any hooks. Because I won't use any non-IP-based information from my ISP's server, I specify a lot of noptions to reduce the payload. As you can see from those options, there seems to be a lot of overlapping ones (e.g., interface_mtu and mtu, ntp_servers and time_servers, etc.). Are all of those necessary? Are any invalid? I'm going purely off of the output of dhcpcd -V. All of the options are DHCP or DHCPv6 options except for mtu which is listed as an "ND option". Is it fine to list ND options or are only DHCP and DHCPv6 options valid?

In my case my ISP has misconfigured their IPv6 router advertisements such that an MTU of 9192 is advertised which is incorrect; thus I want to hardcode a 1500 MTU. Is it necessary to specify both static interface_mtu and static mtu?

[rsmarples]

I would use nooption nd_mtu as it belongs to the ND option parsing and not DHCP (the default).
This should be documented in the option section in dhcpcd.conf(5).

Does this answer your question?

[zacknewman]

Ah, didn't see that. It would be nice if there were a "parse config file" option for dhcpcd. I'm getting an "unknown option" error now. Per dhcpcd.conf(5), DHCPv6 options can have dhcp6_ prepended like ND options have nd_ prepended:

May 10 09:30:34 router dhcpcd[65177]: unknown option: dhcp6_name_servers,dhcp6_domain_search,dhcp6_sntp_servers,dhcp6_fqdn,d
hcp6_posix_timezone,dhcp6_tzdb_timezone,dhcp6_ntp_server,nd_mtu,nd_rdnss,nd_dnssl,time_offset,time_servers,ien116_name_serve
rs,domain_name_servers,host_name,domain_name,interface_mtu,ntp_servers,fqdn,posix_timezone,tzdb_timezone,name_service_search
,domain_search
May 10 09:30:34 router dhcpcd[65177]: unknown option: dhcp6_server_id,dhcp_message_type,dhcp_server_identifier

All of those options were copy and pasted from dhcpcd -V, so I'm not sure why there is an error.

router$ cat /etc/dhcpcd.conf
noipv6rs
denyinterfaces !(ixl2)
allowinterfaces ixl2
script ""
link_rcvbuf 65536
interface ixl2
	duid
	fqdn disable
	iaid 0
	ia_na 0
	ia_pd 0/::/60 -
	ipv6rs
	nooption dhcp6_name_servers,dhcp6_domain_search,dhcp6_sntp_servers,dhcp6_fqdn,dhcp6_posix_timezone,dhcp6_tzdb_timezone,dhcp6_ntp_server,nd_mtu,nd_rdnss,nd_dnssl,time_offset,time_servers,ien116_name_servers,domain_name_servers,host_name,domain_name,interface_mtu,ntp_servers,fqdn,posix_timezone,tzdb_timezone,name_service_search,domain_search
	option dhcp6_rapid_commit,rapid_commit
	persistent
	require dhcp6_server_id,dhcp_message_type,dhcp_server_identifier
	waitip 64

I also tried using the numerical values. When I do that, I still get the errors and I get another error for the option line (i.e., option dhcp6_00014,080 errs while option dhcp6_rapid_commit,rapid_commit does not).

[rsmarples]

dhcp6_ntp_server isn't valid. If there is any invalid option I think it just spits out the whole line.

[zacknewman]

dhcpcd -V shows: 00056 ntp_server encap under DHCPv6 options though.

[zacknewman]

OK, after trial-and-error, it looks like dhcpcd (at least sometimes) requires DHCPv6 options to be on a separate line from DHCP options. As stated above, dhcp6_ntp_server is valid per dhcpcd and IANA. The following config does not log any errors. Additionally it no longer warns about a misconfigured MTU from my ISP:

noipv6rs
denyinterfaces !(ixl2)
allowinterfaces ixl2
script ""
link_rcvbuf 65536
interface ixl2
	duid
	fqdn disable
	iaid 0
	ia_na 0
	ia_pd 0/::/60 -
	ipv6rs
	nooption dhcp6_name_servers,dhcp6_domain_search,dhcp6_sntp_servers,dhcp6_fqdn,dhcp6_posix_timezone,dhcp6_tzdb_timezone,dhcp6_ntp_server
	nooption nd_mtu,nd_rdnss,nd_dnssl
	nooption time_offset,time_servers,ien116_name_servers,domain_name_servers,host_name,domain_name,interface_mtu,ntp_servers,fqdn,posix_timezone,tzdb_timezone,name_service_search,domain_search
	option dhcp6_rapid_commit
	option rapid_commit
	persistent
	require dhcp6_server_id
	require dhcp_message_type,dhcp_server_identifier
	waitip 64

When the require lines are merged, dhcpcd complains about an unknown option. When the noption lines are merged, dhcpcd complains about an unknown option. I suspect this is a bug.