Force the use of DHCP, whatever RA says?

[bortzmeyer]

I tried to configure dhcpcd for DHCPv6 only (no DHCP IPv4, no RA/RS):

# Only DHCP v6
ipv6only
ipv6ra_noautoconf
noipv6rs

But, with this configuration, dhcpcd does not display "eth1: requesting DHCPv6 information" and tcpdump shows it does not send DHCPv6 queries. It makes sense, there is a RFC somewhere that says that DHCPv6 must be used only when RA tells it. I tried on a network without a RA router and dhcpd does not DHCP requests. Is there a way to force the use of DHCP, to have a network without RA? I tried several options as mentioned above but without success.

% dhcpcd --version
dhcpcd 10.3.0
Copyright (c) 2006-2025 Roy Marples
Compiled in features: INET ARP ARPing IPv4LL INET6 DHCPv6 AUTH PRIVSEP

On a Linux box, compiled by myself.