static int atif_ioctl(int cmd, void __user *arg)
{
	static char aarp_mcast[6] = { 0x09, 0x00, 0x00, 0xFF, 0xFF, 0xFF };
	struct ifreq atreq;
	struct atalk_netrange *nr;
	struct sockaddr_at *sa;
	struct net_device *dev;
	struct atalk_iface *atif;
	int ct;
	int limit;
	struct rtentry rtdef;
	int add_route;

	if (copy_from_user(&atreq, arg, sizeof(atreq)))
		return -EFAULT;

	dev = __dev_get_by_name(&init_net, atreq.ifr_name);
	if (!dev)
		return -ENODEV;

	sa = (struct sockaddr_at *)&atreq.ifr_addr;
	atif = atalk_find_dev(dev);

	switch (cmd) {
		case SIOCSIFADDR:
			if (!capable(CAP_NET_ADMIN))
				return -EPERM;
			if (sa->sat_family != AF_APPLETALK)
				return -EINVAL;
			if (dev->type != ARPHRD_ETHER &&
			    dev->type != ARPHRD_LOOPBACK &&
			    dev->type != ARPHRD_LOCALTLK &&
			    dev->type != ARPHRD_PPP)
				return -EPROTONOSUPPORT;

			nr = (struct atalk_netrange *)&sa->sat_zero[0];
			add_route = 1;

			/*
			 * if this is a point-to-point iface, and we already
			 * have an iface for this AppleTalk address, then we
			 * should not add a route
			 */
			if ((dev->flags & IFF_POINTOPOINT) &&
			    atalk_find_interface(sa->sat_addr.s_net,
						 sa->sat_addr.s_node)) {
				printk(KERN_DEBUG "AppleTalk: point-to-point "
						  "interface added with "
						  "existing address\n");
				add_route = 0;
			}

			/*
			 * Phase 1 is fine on LocalTalk but we don't do
			 * EtherTalk phase 1. Anyone wanting to add it go ahead.
			 */
			if (dev->type == ARPHRD_ETHER && nr->nr_phase != 2)
				return -EPROTONOSUPPORT;
			if (sa->sat_addr.s_node == ATADDR_BCAST ||
			    sa->sat_addr.s_node == 254)
				return -EINVAL;
			if (atif) {
				/* Already setting address */
				if (atif->status & ATIF_PROBE)
					return -EBUSY;

				atif->address.s_net  = sa->sat_addr.s_net;
				atif->address.s_node = sa->sat_addr.s_node;
				atrtr_device_down(dev);	/* Flush old routes */
			} else {
				atif = atif_add_device(dev, &sa->sat_addr);
				if (!atif)
					return -ENOMEM;
			}
			atif->nets = *nr;

			/*
			 * Check if the chosen address is used. If so we
			 * error and atalkd will try another.
			 */

			if (!(dev->flags & IFF_LOOPBACK) &&
			    !(dev->flags & IFF_POINTOPOINT) &&
			    atif_probe_device(atif) < 0) {
				atif_drop_device(dev);
				return -EADDRINUSE;
			}

			/* Hey it worked - add the direct routes */
			sa = (struct sockaddr_at *)&rtdef.rt_gateway;
			sa->sat_family = AF_APPLETALK;
			sa->sat_addr.s_net  = atif->address.s_net;
			sa->sat_addr.s_node = atif->address.s_node;
			sa = (struct sockaddr_at *)&rtdef.rt_dst;
			rtdef.rt_flags = RTF_UP;
			sa->sat_family = AF_APPLETALK;
			sa->sat_addr.s_node = ATADDR_ANYNODE;
			if (dev->flags & IFF_LOOPBACK ||
			    dev->flags & IFF_POINTOPOINT)
				rtdef.rt_flags |= RTF_HOST;

			/* Routerless initial state */
			if (nr->nr_firstnet == htons(0) &&
			    nr->nr_lastnet == htons(0xFFFE)) {
				sa->sat_addr.s_net = atif->address.s_net;
				atrtr_create(&rtdef, dev);
				atrtr_set_default(dev);
			} else {
				limit = ntohs(nr->nr_lastnet);
				if (limit - ntohs(nr->nr_firstnet) > 4096) {
					printk(KERN_WARNING "Too many routes/"
							    "iface.\n");
					return -EINVAL;
				}
				if (add_route)
					for (ct = ntohs(nr->nr_firstnet);
					     ct <= limit; ct++) {
						sa->sat_addr.s_net = htons(ct);
						atrtr_create(&rtdef, dev);
					}
			}
			dev_mc_add(dev, aarp_mcast, 6, 1);
			return 0;

		case SIOCGIFADDR:
			if (!atif)
				return -EADDRNOTAVAIL;

			sa->sat_family = AF_APPLETALK;
			sa->sat_addr = atif->address;
			break;

		case SIOCGIFBRDADDR:
			if (!atif)
				return -EADDRNOTAVAIL;

			sa->sat_family = AF_APPLETALK;
			sa->sat_addr.s_net = atif->address.s_net;
			sa->sat_addr.s_node = ATADDR_BCAST;
			break;

		case SIOCATALKDIFADDR:
		case SIOCDIFADDR:
			if (!capable(CAP_NET_ADMIN))
				return -EPERM;
			if (sa->sat_family != AF_APPLETALK)
				return -EINVAL;
			atalk_dev_down(dev);
			break;

		case SIOCSARP:
			if (!capable(CAP_NET_ADMIN))
				return -EPERM;
			if (sa->sat_family != AF_APPLETALK)
				return -EINVAL;
			/*
			 * for now, we only support proxy AARP on ELAP;
			 * we should be able to do it for LocalTalk, too.
			 */
			if (dev->type != ARPHRD_ETHER)
				return -EPROTONOSUPPORT;

			/*
			 * atif points to the current interface on this network;
			 * we aren't concerned about its current status (at
			 * least for now), but it has all the settings about
			 * the network we're going to probe. Consequently, it
			 * must exist.
			 */
			if (!atif)
				return -EADDRNOTAVAIL;

			nr = (struct atalk_netrange *)&(atif->nets);
			/*
			 * Phase 1 is fine on Localtalk but we don't do
			 * Ethertalk phase 1. Anyone wanting to add it go ahead.
			 */
			if (dev->type == ARPHRD_ETHER && nr->nr_phase != 2)
				return -EPROTONOSUPPORT;

			if (sa->sat_addr.s_node == ATADDR_BCAST ||
			    sa->sat_addr.s_node == 254)
				return -EINVAL;

			/*
			 * Check if the chosen address is used. If so we
			 * error and ATCP will try another.
			 */
			if (atif_proxy_probe_device(atif, &(sa->sat_addr)) < 0)
				return -EADDRINUSE;

			/*
			 * We now have an address on the local network, and
			 * the AARP code will defend it for us until we take it
			 * down. We don't set up any routes right now, because
			 * ATCP will install them manually via SIOCADDRT.
			 */
			break;

		case SIOCDARP:
			if (!capable(CAP_NET_ADMIN))
				return -EPERM;
			if (sa->sat_family != AF_APPLETALK)
				return -EINVAL;
			if (!atif)
				return -EADDRNOTAVAIL;

			/* give to aarp module to remove proxy entry */
			aarp_proxy_remove(atif->dev, &(sa->sat_addr));
			return 0;
	}

	return copy_to_user(arg, &atreq, sizeof(atreq)) ? -EFAULT : 0;
}