>>This cannot possibly work, the client can't find the
lladdr of the gateway
Oops, I now see my experiment was not valid: dhcpcd adds route to router but
can't reach it.
I added alias and it now works, thank you.
So, dhcp client assumes that router anounced by server is always reachable
interface that got configuration via dhcp.
Something that is not written explicitly in RFC, but seems to be de-facto
and it now supported by openbsd, thanks to this patch.