--nolink / -K does not stop dhcpcd from receiving link messages for carrier status

[rronsherifii]

Hi, we are using dhcpcd 10.3.0 and are having problems with the --nolink option not working.

The man page for -K / --nolink states:

│ Don't receive link messages for carrier status. You should only have to use this with buggy device drivers or running dhcpcd through a network manager.

We manage the interface configuration ourselves and use dhcpcd only for DHCPv6 lease acquisition. The interface experiences very brief carrier flaps — in the order of milliseconds — as a side effect of interface reconfiguration. We want
dhcpcd to ignore these and keep the lease alive, which is exactly what --nolink is documented for.

However, passing --nolink either as a command line argument or via the config file has no effect. The syslog still shows dhcpcd reacting to the carrier events and dropping the lease:

dhcpcd[1234]: : carrier lost
dhcpcd[1234]: : carrier acquired
dhcpcd[1234]: : DHCPv6 lease expired

Config file $CFG:

timeout 60
background
release
option domain_name_servers, domain_name, domain_search
option classless_static_routes
option host_name
require dhcp_server_identifier
noipv6rs
ia_na
interface $interface
noipv6rs
ia_na
ia_pd 1 -

Invocation:
dhcpcd --noconfigure --nolink -6 -d -f $CFG -c $SCRIPT_FILE

[perkelix]

Does the issue still exist with 10.3.1 also?

[rronsherifii]

Uplifting to 10.3.1 is a significant effort in its own right and not something that can be done on short notice. In the interim, we will backport the relevant changes as patches to our current version and try the option out with that.

[rronsherifii]

We tried it with 10.3.1, the issue exists in this version also...

[rsmarples]

With --nolink we still process IFF_UP flag coming and going from the interface, which dhcpcd will translate into carrier up/down events.

Is this what you are seeing? Can you verify using ip monitor or similar?

[rronsherifii]

Yes, this is exactly what im seeing.