Its supposed to be the default.  It doesn't work because I left the
return out of the if in the loop when I rewrote it to go with
the new readipifc interface.  The code should look like:

void
readipinterfaces(void)
{
	Ipifc *nifc;
	Iplifc *lifc;

	ipifcs = readipifc(mntpt, ipifcs, -1);
	for(nifc = ipifcs; nifc; nifc = nifc->next)
		for(lifc = nifc->lifc; lifc; lifc = lifc->next)
			if(ipcmp(lifc->ip, IPnoaddr) != 0){
				ipmove(ipa, lifc->ip);
				sprint(ipaddr, "%I", ipa);
				if(debug)
					syslog(0, "dns", "ipaddr is %s\n", ipaddr);
				return;
			}
	ipmove(ipa, IPnoaddr);
}

Thanks, I'm an idiot.