Guix,

While testing #35563, I found that "dhcp-client" does not work on a
kernel that has CONFIG_IPV6_SIT=y.

The reason is that the system has a virtual "sit0" interface that is not
capable of ARP traffic, which dhclient does not approve of:

May  9 16:18:37 localhost dhclient: Unsupported device type 776 for "sit0"

You can `modprobe sit` on your system if you want to reproduce the
failure.

The attached patch solves it for me.