net/appletalk/ddp.c

// SPDX-License-Identifier: GPL-2.0-or-later
/*
 *	DDP:	An implementation of the AppleTalk DDP protocol for
 *		Ethernet 'ELAP'.
 *
 *		Alan Cox  <alan@lxorguk.ukuu.org.uk>
 *
 *		With more than a little assistance from
 *
 *		Wesley Craig <netatalk@umich.edu>
 *
 *	Fixes:
 *		Neil Horman		:	Added missing device ioctls
 *		Michael Callahan	:	Made routing work
 *		Wesley Craig		:	Fix probing to listen to a
 *						passed node id.
 *		Alan Cox		:	Added send/recvmsg support
 *		Alan Cox		:	Moved at. to protinfo in
 *						socket.
 *		Alan Cox		:	Added firewall hooks.
 *		Alan Cox		:	Supports new ARPHRD_LOOPBACK
 *		Christer Weinigel	: 	Routing and /proc fixes.
 *		Bradford Johnson	:	LocalTalk.
 *		Tom Dyas		:	Module support.
 *		Alan Cox		:	Hooks for PPP (based on the
 *						LocalTalk hook).
 *		Alan Cox		:	Posix bits
 *		Alan Cox/Mike Freeman	:	Possible fix to NBP problems
 *		Bradford Johnson	:	IP-over-DDP (experimental)
 *		Jay Schulist		:	Moved IP-over-DDP to its own
 *						driver file. (ipddp.c & ipddp.h)
 *		Jay Schulist		:	Made work as module with
 *						AppleTalk drivers, cleaned it.
 *		Rob Newberry		:	Added proxy AARP and AARP
 *						procfs, moved probing to AARP
 *						module.
 *              Adrian Sun/
 *              Michael Zuelsdorff      :       fix for net.0 packets. don't
 *                                              allow illegal ether/tokentalk
 *                                              port assignment. we lose a
 *                                              valid localtalk port as a
 *                                              result.
 *		Arnaldo C. de Melo	:	Cleanup, in preparation for
 *						shared skb support 8)
 *		Arnaldo C. de Melo	:	Move proc stuff to atalk_proc.c,
 *						use seq_file
 */

#include <linux/capability.h>
#include <linux/module.h>
#include <linux/if_arp.h>
#include <linux/termios.h>	/* For TIOCOUTQ/INQ */
#include <linux/compat.h>
#include <linux/slab.h>
#include <net/datalink.h>
#include <net/psnap.h>
#include <net/sock.h>
#include <net/tcp_states.h>
#include <net/route.h>
#include <linux/atalk.h>
#include <linux/highmem.h>

struct datalink_proto *ddp_dl, *aarp_dl;
static const struct proto_ops atalk_dgram_ops;

/**************************************************************************\
*                                                                          *
* Handlers for the socket list.                                            *
*                                                                          *
\**************************************************************************/

HLIST_HEAD(atalk_sockets);
DEFINE_RWLOCK(atalk_sockets_lock);

static inline void __atalk_insert_socket(struct sock *sk)
{
	sk_add_node(sk, &atalk_sockets);
}

static inline void atalk_remove_socket(struct sock *sk)
{
	write_lock_bh(&atalk_sockets_lock);
	sk_del_node_init(sk);
	write_unlock_bh(&atalk_sockets_lock);
}

static struct sock *atalk_search_socket(struct sockaddr_at *to,
					struct atalk_iface *atif)
{
	struct sock *s;

	read_lock_bh(&atalk_sockets_lock);
	sk_for_each(s, &atalk_sockets) {
		struct atalk_sock *at = at_sk(s);

		if (to->sat_port != at->src_port)
			continue;

		if (to->sat_addr.s_net == ATADDR_ANYNET &&
		    to->sat_addr.s_node == ATADDR_BCAST)
			goto found;

		if (to->sat_addr.s_net == at->src_net &&
		    (to->sat_addr.s_node == at->src_node ||
		     to->sat_addr.s_node == ATADDR_BCAST ||
		     to->sat_addr.s_node == ATADDR_ANYNODE))
			goto found;

		/* XXXX.0 -- we got a request for this router. make sure
		 * that the node is appropriately set. */
		if (to->sat_addr.s_node == ATADDR_ANYNODE &&
		    to->sat_addr.s_net != ATADDR_ANYNET &&
		    atif->address.s_node == at->src_node) {
			to->sat_addr.s_node = atif->address.s_node;
			goto found;
		}
	}
	s = NULL;
found:
	read_unlock_bh(&atalk_sockets_lock);
	return s;
}

/**
 * atalk_find_or_insert_socket - Try to find a socket matching ADDR
 * @sk: socket to insert in the list if it is not there already
 * @sat: address to search for
 *
 * Try to find a socket matching ADDR in the socket list, if found then return
 * it. If not, insert SK into the socket list.
 *
 * This entire operation must execute atomically.
 */
static struct sock *atalk_find_or_insert_socket(struct sock *sk,
						struct sockaddr_at *sat)
{
	struct sock *s;
	struct atalk_sock *at;

	write_lock_bh(&atalk_sockets_lock);
	sk_for_each(s, &atalk_sockets) {
		at = at_sk(s);

		if (at->src_net == sat->sat_addr.s_net &&
		    at->src_node == sat->sat_addr.s_node &&
		    at->src_port == sat->sat_port)
			goto found;
	}
	s = NULL;
	__atalk_insert_socket(sk); /* Wheee, it's free, assign and insert. */
found:
	write_unlock_bh(&atalk_sockets_lock);
	return s;
}

static void atalk_destroy_timer(struct timer_list *t)
{
	struct sock *sk = from_timer(sk, t, sk_timer);

	if (sk_has_allocations(sk)) {
		sk->sk_timer.expires = jiffies + SOCK_DESTROY_TIME;
		add_timer(&sk->sk_timer);
	} else
		sock_put(sk);
}

static inline void atalk_destroy_socket(struct sock *sk)
{
	atalk_remove_socket(sk);
	skb_queue_purge(&sk->sk_receive_queue);

	if (sk_has_allocations(sk)) {
		timer_setup(&sk->sk_timer, atalk_destroy_timer, 0);
		sk->sk_timer.expires	= jiffies + SOCK_DESTROY_TIME;
		add_timer(&sk->sk_timer);
	} else
		sock_put(sk);
}

/**************************************************************************\
*                                                                          *
* Routing tables for the AppleTalk socket layer.                           *
*                                                                          *
\**************************************************************************/

/* Anti-deadlock ordering is atalk_routes_lock --> iface_lock -DaveM */
struct atalk_route *atalk_routes;
DEFINE_RWLOCK(atalk_routes_lock);

struct atalk_iface *atalk_interfaces;
DEFINE_RWLOCK(atalk_interfaces_lock);

/* For probing devices or in a routerless network */
struct atalk_route atrtr_default;

/* AppleTalk interface control */
/*
 * Drop a device. Doesn't drop any of its routes - that is the caller's
 * problem. Called when we down the interface or delete the address.
 */
static void atif_drop_device(struct net_device *dev)
{
	struct atalk_iface **iface = &atalk_interfaces;
	struct atalk_iface *tmp;

	write_lock_bh(&atalk_interfaces_lock);
	while ((tmp = *iface) != NULL) {
		if (tmp->dev == dev) {
			*iface = tmp->next;
			dev_put(dev);
			kfree(tmp);
			dev->atalk_ptr = NULL;
		} else
			iface = &tmp->next;
	}
	write_unlock_bh(&atalk_interfaces_lock);
}

static struct atalk_iface *atif_add_device(struct net_device *dev,
					   struct atalk_addr *sa)
{
	struct atalk_iface *iface = kzalloc(sizeof(*iface), GFP_KERNEL);

	if (!iface)
		goto out;

	dev_hold(dev);
	iface->dev = dev;
	dev->atalk_ptr = iface;
	iface->address = *sa;
	iface->status = 0;

	write_lock_bh(&atalk_interfaces_lock);
	iface->next = atalk_interfaces;
	atalk_interfaces = iface;
	write_unlock_bh(&atalk_interfaces_lock);
out:
	return iface;
}

/* Perform phase 2 AARP probing on our tentative address */
static int atif_probe_device(struct atalk_iface *atif)
{
	int netrange = ntohs(atif->nets.nr_lastnet) -
			ntohs(atif->nets.nr_firstnet) + 1;
	int probe_net = ntohs(atif->address.s_net);
	int probe_node = atif->address.s_node;
	int netct, nodect;

	/* Offset the network we start probing with */
	if (probe_net == ATADDR_ANYNET) {
		probe_net = ntohs(atif->nets.nr_firstnet);
		if (netrange)
			probe_net += jiffies % netrange;
	}
	if (probe_node == ATADDR_ANYNODE)
		probe_node = jiffies & 0xFF;

	/* Scan the networks */
	atif->status |= ATIF_PROBE;
	for (netct = 0; netct <= netrange; netct++) {
		/* Sweep the available nodes from a given start */
		atif->address.s_net = htons(probe_net);
		for (nodect = 0; nodect < 256; nodect++) {
			atif->address.s_node = (nodect + probe_node) & 0xFF;
			if (atif->address.s_node > 0 &&
			    atif->address.s_node < 254) {
				/* Probe a proposed address */
				aarp_probe_network(atif);

				if (!(atif->status & ATIF_PROBE_FAIL)) {
					atif->status &= ~ATIF_PROBE;
					return 0;
				}
			}
			atif->status &= ~ATIF_PROBE_FAIL;
		}
		probe_net++;
		if (probe_net > ntohs(atif->nets.nr_lastnet))
			probe_net = ntohs(atif->nets.nr_firstnet);
	}
	atif->status &= ~ATIF_PROBE;

	return -EADDRINUSE;	/* Network is full... */
}


/* Perform AARP probing for a proxy address */
static int atif_proxy_probe_device(struct atalk_iface *atif,
				   struct atalk_addr *proxy_addr)
{
	int netrange = ntohs(atif->nets.nr_lastnet) -
			ntohs(atif->nets.nr_firstnet) + 1;
	/* we probe the interface's network */
	int probe_net = ntohs(atif->address.s_net);
	int probe_node = ATADDR_ANYNODE;	    /* we'll take anything */
	int netct, nodect;

	/* Offset the network we start probing with */
	if (probe_net == ATADDR_ANYNET) {
		probe_net = ntohs(atif->nets.nr_firstnet);
		if (netrange)
			probe_net += jiffies % netrange;
	}

	if (probe_node == ATADDR_ANYNODE)
		probe_node = jiffies & 0xFF;

	/* Scan the networks */
	for (netct = 0; netct <= netrange; netct++) {
		/* Sweep the available nodes from a given start */
		proxy_addr->s_net = htons(probe_net);
		for (nodect = 0; nodect < 256; nodect++) {
			proxy_addr->s_node = (nodect + probe_node) & 0xFF;
			if (proxy_addr->s_node > 0 &&
			    proxy_addr->s_node < 254) {
				/* Tell AARP to probe a proposed address */
				int ret = aarp_proxy_probe_network(atif,
								    proxy_addr);

				if (ret != -EADDRINUSE)
					return ret;
			}
		}
		probe_net++;
		if (probe_net > ntohs(atif->nets.nr_lastnet))
			probe_net = ntohs(atif->nets.nr_firstnet);
	}

	return -EADDRINUSE;	/* Network is full... */
}


struct atalk_addr *atalk_find_dev_addr(struct net_device *dev)
{
	struct atalk_iface *iface = dev->atalk_ptr;
	return iface ? &iface->address : NULL;
}

static struct atalk_addr *atalk_find_primary(void)
{
	struct atalk_iface *fiface = NULL;
	struct atalk_addr *retval;
	struct atalk_iface *iface;

	/*
	 * Return a point-to-point interface only if
	 * there is no non-ptp interface available.
	 */
	read_lock_bh(&atalk_interfaces_lock);
	for (iface = atalk_interfaces; iface; iface = iface->next) {
		if (!fiface && !(iface->dev->flags & IFF_LOOPBACK))
			fiface = iface;
		if (!(iface->dev->flags & (IFF_LOOPBACK | IFF_POINTOPOINT))) {
			retval = &iface->address;
			goto out;
		}
	}

	if (fiface)
		retval = &fiface->address;
	else if (atalk_interfaces)
		retval = &atalk_interfaces->address;
	else
		retval = NULL;
out:
	read_unlock_bh(&atalk_interfaces_lock);
	return retval;
}

/*
 * Find a match for 'any network' - ie any of our interfaces with that
 * node number will do just nicely.
 */
static struct atalk_iface *atalk_find_anynet(int node, struct net_device *dev)
{
	struct atalk_iface *iface = dev->atalk_ptr;

	if (!iface || iface->status & ATIF_PROBE)
		goto out_err;

	if (node != ATADDR_BCAST &&
	    iface->address.s_node != node &&
	    node != ATADDR_ANYNODE)
		goto out_err;
out:
	return iface;
out_err:
	iface = NULL;
	goto out;
}

/* Find a match for a specific network:node pair */
static struct atalk_iface *atalk_find_interface(__be16 net, int node)
{
	struct atalk_iface *iface;

	read_lock_bh(&atalk_interfaces_lock);
	for (iface = atalk_interfaces; iface; iface = iface->next) {
		if ((node == ATADDR_BCAST ||
		     node == ATADDR_ANYNODE ||
		     iface->address.s_node == node) &&
		    iface->address.s_net == net &&
		    !(iface->status & ATIF_PROBE))
			break;

		/* XXXX.0 -- net.0 returns the iface associated with net */
		if (node == ATADDR_ANYNODE && net != ATADDR_ANYNET &&
		    ntohs(iface->nets.nr_firstnet) <= ntohs(net) &&
		    ntohs(net) <= ntohs(iface->nets.nr_lastnet))
			break;
	}
	read_unlock_bh(&atalk_interfaces_lock);
	return iface;
}


/*
 * Find a route for an AppleTalk packet. This ought to get cached in
 * the socket (later on...). We know about host routes and the fact
 * that a route must be direct to broadcast.
 */
static struct atalk_route *atrtr_find(struct atalk_addr *target)
{
	/*
	 * we must search through all routes unless we find a
	 * host route, because some host routes might overlap
	 * network routes
	 */
	struct atalk_route *net_route = NULL;
	struct atalk_route *r;

	read_lock_bh(&atalk_routes_lock);
	for (r = atalk_routes; r; r = r->next) {
		if (!(r->flags & RTF_UP))
			continue;

		if (r->target.s_net == target->s_net) {
			if (r->flags & RTF_HOST) {
				/*
				 * if this host route is for the target,
				 * the we're done
				 */
				if (r->target.s_node == target->s_node)
					goto out;
			} else
				/*
				 * this route will work if there isn't a
				 * direct host route, so cache it
				 */
				net_route = r;
		}
	}

	/*
	 * if we found a network route but not a direct host
	 * route, then return it
	 */
	if (net_route)
		r = net_route;
	else if (atrtr_default.dev)
		r = &atrtr_default;
	else /* No route can be found */
		r = NULL;
out:
	read_unlock_bh(&atalk_routes_lock);
	return r;
}


/*
 * Given an AppleTalk network, find the device to use. This can be
 * a simple lookup.
 */
struct net_device *atrtr_get_dev(struct atalk_addr *sa)
{
	struct atalk_route *atr = atrtr_find(sa);
	return atr ? atr->dev : NULL;
}

/* Set up a default router */
static void atrtr_set_default(struct net_device *dev)
{
	atrtr_default.dev	     = dev;
	atrtr_default.flags	     = RTF_UP;
	atrtr_default.gateway.s_net  = htons(0);
	atrtr_default.gateway.s_node = 0;
}

/*
 * Add a router. Basically make sure it looks valid and stuff the
 * entry in the list. While it uses netranges we always set them to one
 * entry to work like netatalk.
 */
static int atrtr_create(struct rtentry *r, struct net_device *devhint)
{
	struct sockaddr_at *ta = (struct sockaddr_at *)&r->rt_dst;
	struct sockaddr_at *ga = (struct sockaddr_at *)&r->rt_gateway;
	struct atalk_route *rt;
	struct atalk_iface *iface, *riface;
	int retval = -EINVAL;

	/*
	 * Fixme: Raise/Lower a routing change semaphore for these
	 * operations.
	 */

	/* Validate the request */
	if (ta->sat_family != AF_APPLETALK ||
	    (!devhint && ga->sat_family != AF_APPLETALK))
		goto out;

	/* Now walk the routing table and make our decisions */
	write_lock_bh(&atalk_routes_lock);
	for (rt = atalk_routes; rt; rt = rt->next) {
		if (r->rt_flags != rt->flags)
			continue;

		if (ta->sat_addr.s_net == rt->target.s_net) {
			if (!(rt->flags & RTF_HOST))
				break;
			if (ta->sat_addr.s_node == rt->target.s_node)
				break;
		}
	}

	if (!devhint) {
		riface = NULL;

		read_lock_bh(&atalk_interfaces_lock);
		for (iface = atalk_interfaces; iface; iface = iface->next) {
			if (!riface &&
			    ntohs(ga->sat_addr.s_net) >=
					ntohs(iface->nets.nr_firstnet) &&
			    ntohs(ga->sat_addr.s_net) <=
					ntohs(iface->nets.nr_lastnet))
				riface = iface;

			if (ga->sat_addr.s_net == iface->address.s_net &&
			    ga->sat_addr.s_node == iface->address.s_node)
				riface = iface;
		}
		read_unlock_bh(&atalk_interfaces_lock);

		retval = -ENETUNREACH;
		if (!riface)
			goto out_unlock;

		devhint = riface->dev;
	}

	if (!rt) {
		rt = kzalloc(sizeof(*rt), GFP_ATOMIC);

		retval = -ENOBUFS;
		if (!rt)
			goto out_unlock;

		rt->next = atalk_routes;
		atalk_routes = rt;
	}

	/* Fill in the routing entry */
	rt->target  = ta->sat_addr;
	dev_hold(devhint);
	rt->dev     = devhint;
	rt->flags   = r->rt_flags;
	rt->gateway = ga->sat_addr;

	retval = 0;
out_unlock:
	write_unlock_bh(&atalk_routes_lock);
out:
	return retval;
}

/* Delete a route. Find it and discard it */
static int atrtr_delete(struct atalk_addr *addr)
{
	struct atalk_route **r = &atalk_routes;
	int retval = 0;
	struct atalk_route *tmp;

	write_lock_bh(&atalk_routes_lock);
	while ((tmp = *r) != NULL) {
		if (tmp->target.s_net == addr->s_net &&
		    (!(tmp->flags&RTF_GATEWAY) ||
		     tmp->target.s_node == addr->s_node)) {
			*r = tmp->next;
			dev_put(tmp->dev);
			kfree(tmp);
			goto out;
		}
		r = &tmp->next;
	}
	retval = -ENOENT;
out:
	write_unlock_bh(&atalk_routes_lock);
	return retval;
}

/*
 * Called when a device is downed. Just throw away any routes
 * via it.
 */
static void atrtr_device_down(struct net_device *dev)
{
	struct atalk_route **r = &atalk_routes;
	struct atalk_route *tmp;

	write_lock_bh(&atalk_routes_lock);
	while ((tmp = *r) != NULL) {
		if (tmp->dev == dev) {
			*r = tmp->next;
			dev_put(dev);
			kfree(tmp);
		} else
			r = &tmp->next;
	}
	write_unlock_bh(&atalk_routes_lock);

	if (atrtr_default.dev == dev)
		atrtr_set_default(NULL);
}

/* Actually down the interface */
static inline void atalk_dev_down(struct net_device *dev)
{
	atrtr_device_down(dev);	/* Remove all routes for the device */
	aarp_device_down(dev);	/* Remove AARP entries for the device */
	atif_drop_device(dev);	/* Remove the device */
}

/*
 * A device event has occurred. Watch for devices going down and
 * delete our use of them (iface and route).
 */
static int ddp_device_event(struct notifier_block *this, unsigned long event,
			    void *ptr)
{
	struct net_device *dev = netdev_notifier_info_to_dev(ptr);

	if (!net_eq(dev_net(dev), &init_net))
		return NOTIFY_DONE;

	if (event == NETDEV_DOWN)
		/* Discard any use of this */
		atalk_dev_down(dev);

	return NOTIFY_DONE;
}

/* ioctl calls. Shouldn't even need touching */
/* Device configuration ioctl calls */
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_global(dev, aarp_mcast);
		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;
}

/* Routing ioctl() calls */
static int atrtr_ioctl(unsigned int cmd, void __user *arg)
{
	struct rtentry rt;

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

	switch (cmd) {
	case SIOCDELRT:
		if (rt.rt_dst.sa_family != AF_APPLETALK)
			return -EINVAL;
		return atrtr_delete(&((struct sockaddr_at *)
				      &rt.rt_dst)->sat_addr);

	case SIOCADDRT: {
		struct net_device *dev = NULL;
		if (rt.rt_dev) {
			char name[IFNAMSIZ];
			if (copy_from_user(name, rt.rt_dev, IFNAMSIZ-1))
				return -EFAULT;
			name[IFNAMSIZ-1] = '\0';
			dev = __dev_get_by_name(&init_net, name);
			if (!dev)
				return -ENODEV;
		}
		return atrtr_create(&rt, dev);
	}
	}
	return -EINVAL;
}

/**************************************************************************\
*                                                                          *
* Handling for system calls applied via the various interfaces to an       *
* AppleTalk socket object.                                                 *
*                                                                          *
\**************************************************************************/

/*
 * Checksum: This is 'optional'. It's quite likely also a good
 * candidate for assembler hackery 8)
 */
static unsigned long atalk_sum_partial(const unsigned char *data,
				       int len, unsigned long sum)
{
	/* This ought to be unwrapped neatly. I'll trust gcc for now */
	while (len--) {
		sum += *data++;
		sum = rol16(sum, 1);
	}
	return sum;
}

/*  Checksum skb data --  similar to skb_checksum  */
static unsigned long atalk_sum_skb(const struct sk_buff *skb, int offset,
				   int len, unsigned long sum)
{
	int start = skb_headlen(skb);
	struct sk_buff *frag_iter;
	int i, copy;

	/* checksum stuff in header space */
	if ((copy = start - offset) > 0) {
		if (copy > len)
			copy = len;
		sum = atalk_sum_partial(skb->data + offset, copy, sum);
		if ((len -= copy) == 0)
			return sum;

		offset += copy;
	}

	/* checksum stuff in frags */
	for (i = 0; i < skb_shinfo(skb)->nr_frags; i++) {
		int end;
		const skb_frag_t *frag = &skb_shinfo(skb)->frags[i];
		WARN_ON(start > offset + len);

		end = start + skb_frag_size(frag);
		if ((copy = end - offset) > 0) {
			u8 *vaddr;

			if (copy > len)
				copy = len;
			vaddr = kmap_atomic(skb_frag_page(frag));
			sum = atalk_sum_partial(vaddr + frag->page_offset +
						  offset - start, copy, sum);
			kunmap_atomic(vaddr);

			if (!(len -= copy))
				return sum;
			offset += copy;
		}
		start = end;
	}

	skb_walk_frags(skb, frag_iter) {
		int end;

		WARN_ON(start > offset + len);

		end = start + frag_iter->len;
		if ((copy = end - offset) > 0) {
			if (copy > len)
				copy = len;
			sum = atalk_sum_skb(frag_iter, offset - start,
					    copy, sum);
			if ((len -= copy) == 0)
				return sum;
			offset += copy;
		}
		start = end;
	}

	BUG_ON(len > 0);

	return sum;
}

static __be16 atalk_checksum(const struct sk_buff *skb, int len)
{
	unsigned long sum;

	/* skip header 4 bytes */
	sum = atalk_sum_skb(skb, 4, len-4, 0);

	/* Use 0xFFFF for 0. 0 itself means none */
	return sum ? htons((unsigned short)sum) : htons(0xFFFF);
}

static struct proto ddp_proto = {
	.name	  = "DDP",
	.owner	  = THIS_MODULE,
	.obj_size = sizeof(struct atalk_sock),
};

/*
 * Create a socket. Initialise the socket, blank the addresses
 * set the state.
 */
static int atalk_create(struct net *net, struct socket *sock, int protocol,
			int kern)
{
	struct sock *sk;
	int rc = -ESOCKTNOSUPPORT;

	if (!net_eq(net, &init_net))
		return -EAFNOSUPPORT;

	/*
	 * We permit SOCK_DGRAM and RAW is an extension. It is trivial to do
	 * and gives you the full ELAP frame. Should be handy for CAP 8)
	 */
	if (sock->type != SOCK_RAW && sock->type != SOCK_DGRAM)
		goto out;
	rc = -ENOMEM;
	sk = sk_alloc(net, PF_APPLETALK, GFP_KERNEL, &ddp_proto, kern);
	if (!sk)
		goto out;
	rc = 0;
	sock->ops = &atalk_dgram_ops;
	sock_init_data(sock, sk);

	/* Checksums on by default */
	sock_set_flag(sk, SOCK_ZAPPED);
out:
	return rc;
}

/* Free a socket. No work needed */
static int atalk_release(struct socket *sock)
{
	struct sock *sk = sock->sk;

	if (sk) {
		sock_hold(sk);
		lock_sock(sk);

		sock_orphan(sk);
		sock->sk = NULL;
		atalk_destroy_socket(sk);

		release_sock(sk);
		sock_put(sk);
	}
	return 0;
}

/**
 * atalk_pick_and_bind_port - Pick a source port when one is not given
 * @sk: socket to insert into the tables
 * @sat: address to search for
 *
 * Pick a source port when one is not given. If we can find a suitable free
 * one, we insert the socket into the tables using it.
 *
 * This whole operation must be atomic.
 */
static int atalk_pick_and_bind_port(struct sock *sk, struct sockaddr_at *sat)
{
	int retval;

	write_lock_bh(&atalk_sockets_lock);

	for (sat->sat_port = ATPORT_RESERVED;
	     sat->sat_port < ATPORT_LAST;
	     sat->sat_port++) {
		struct sock *s;

		sk_for_each(s, &atalk_sockets) {
			struct atalk_sock *at = at_sk(s);

			if (at->src_net == sat->sat_addr.s_net &&
			    at->src_node == sat->sat_addr.s_node &&
			    at->src_port == sat->sat_port)
				goto try_next_port;
		}

		/* Wheee, it's free, assign and insert. */
		__atalk_insert_socket(sk);
		at_sk(sk)->src_port = sat->sat_port;
		retval = 0;
		goto out;

try_next_port:;
	}

	retval = -EBUSY;
out:
	write_unlock_bh(&atalk_sockets_lock);
	return retval;
}

static int atalk_autobind(struct sock *sk)
{
	struct atalk_sock *at = at_sk(sk);
	struct sockaddr_at sat;
	struct atalk_addr *ap = atalk_find_primary();
	int n = -EADDRNOTAVAIL;

	if (!ap || ap->s_net == htons(ATADDR_ANYNET))
		goto out;

	at->src_net  = sat.sat_addr.s_net  = ap->s_net;
	at->src_node = sat.sat_addr.s_node = ap->s_node;

	n = atalk_pick_and_bind_port(sk, &sat);
	if (!n)
		sock_reset_flag(sk, SOCK_ZAPPED);
out:
	return n;
}

/* Set the address 'our end' of the connection */
static int atalk_bind(struct socket *sock, struct sockaddr *uaddr, int addr_len)
{
	struct sockaddr_at *addr = (struct sockaddr_at *)uaddr;
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);
	int err;

	if (!sock_flag(sk, SOCK_ZAPPED) ||
	    addr_len != sizeof(struct sockaddr_at))
		return -EINVAL;

	if (addr->sat_family != AF_APPLETALK)
		return -EAFNOSUPPORT;

	lock_sock(sk);
	if (addr->sat_addr.s_net == htons(ATADDR_ANYNET)) {
		struct atalk_addr *ap = atalk_find_primary();

		err = -EADDRNOTAVAIL;
		if (!ap)
			goto out;

		at->src_net  = addr->sat_addr.s_net = ap->s_net;
		at->src_node = addr->sat_addr.s_node = ap->s_node;
	} else {
		err = -EADDRNOTAVAIL;
		if (!atalk_find_interface(addr->sat_addr.s_net,
					  addr->sat_addr.s_node))
			goto out;

		at->src_net  = addr->sat_addr.s_net;
		at->src_node = addr->sat_addr.s_node;
	}

	if (addr->sat_port == ATADDR_ANYPORT) {
		err = atalk_pick_and_bind_port(sk, addr);

		if (err < 0)
			goto out;
	} else {
		at->src_port = addr->sat_port;

		err = -EADDRINUSE;
		if (atalk_find_or_insert_socket(sk, addr))
			goto out;
	}

	sock_reset_flag(sk, SOCK_ZAPPED);
	err = 0;
out:
	release_sock(sk);
	return err;
}

/* Set the address we talk to */
static int atalk_connect(struct socket *sock, struct sockaddr *uaddr,
			 int addr_len, int flags)
{
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);
	struct sockaddr_at *addr;
	int err;

	sk->sk_state   = TCP_CLOSE;
	sock->state = SS_UNCONNECTED;

	if (addr_len != sizeof(*addr))
		return -EINVAL;

	addr = (struct sockaddr_at *)uaddr;

	if (addr->sat_family != AF_APPLETALK)
		return -EAFNOSUPPORT;

	if (addr->sat_addr.s_node == ATADDR_BCAST &&
	    !sock_flag(sk, SOCK_BROADCAST)) {
#if 1
		pr_warn("atalk_connect: %s is broken and did not set SO_BROADCAST.\n",
			current->comm);
#else
		return -EACCES;
#endif
	}

	lock_sock(sk);
	err = -EBUSY;
	if (sock_flag(sk, SOCK_ZAPPED))
		if (atalk_autobind(sk) < 0)
			goto out;

	err = -ENETUNREACH;
	if (!atrtr_get_dev(&addr->sat_addr))
		goto out;

	at->dest_port = addr->sat_port;
	at->dest_net  = addr->sat_addr.s_net;
	at->dest_node = addr->sat_addr.s_node;

	sock->state  = SS_CONNECTED;
	sk->sk_state = TCP_ESTABLISHED;
	err = 0;
out:
	release_sock(sk);
	return err;
}

/*
 * Find the name of an AppleTalk socket. Just copy the right
 * fields into the sockaddr.
 */
static int atalk_getname(struct socket *sock, struct sockaddr *uaddr,
			 int peer)
{
	struct sockaddr_at sat;
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);
	int err;

	lock_sock(sk);
	err = -ENOBUFS;
	if (sock_flag(sk, SOCK_ZAPPED))
		if (atalk_autobind(sk) < 0)
			goto out;

	memset(&sat, 0, sizeof(sat));

	if (peer) {
		err = -ENOTCONN;
		if (sk->sk_state != TCP_ESTABLISHED)
			goto out;

		sat.sat_addr.s_net  = at->dest_net;
		sat.sat_addr.s_node = at->dest_node;
		sat.sat_port	    = at->dest_port;
	} else {
		sat.sat_addr.s_net  = at->src_net;
		sat.sat_addr.s_node = at->src_node;
		sat.sat_port	    = at->src_port;
	}

	sat.sat_family = AF_APPLETALK;
	memcpy(uaddr, &sat, sizeof(sat));
	err = sizeof(struct sockaddr_at);

out:
	release_sock(sk);
	return err;
}

#if IS_ENABLED(CONFIG_IPDDP)
static __inline__ int is_ip_over_ddp(struct sk_buff *skb)
{
	return skb->data[12] == 22;
}

static int handle_ip_over_ddp(struct sk_buff *skb)
{
	struct net_device *dev = __dev_get_by_name(&init_net, "ipddp0");
	struct net_device_stats *stats;

	/* This needs to be able to handle ipddp"N" devices */
	if (!dev) {
		kfree_skb(skb);
		return NET_RX_DROP;
	}

	skb->protocol = htons(ETH_P_IP);
	skb_pull(skb, 13);
	skb->dev   = dev;
	skb_reset_transport_header(skb);

	stats = netdev_priv(dev);
	stats->rx_packets++;
	stats->rx_bytes += skb->len + 13;
	return netif_rx(skb);  /* Send the SKB up to a higher place. */
}
#else
/* make it easy for gcc to optimize this test out, i.e. kill the code */
#define is_ip_over_ddp(skb) 0
#define handle_ip_over_ddp(skb) 0
#endif

static int atalk_route_packet(struct sk_buff *skb, struct net_device *dev,
			      struct ddpehdr *ddp, __u16 len_hops, int origlen)
{
	struct atalk_route *rt;
	struct atalk_addr ta;

	/*
	 * Don't route multicast, etc., packets, or packets sent to "this
	 * network"
	 */
	if (skb->pkt_type != PACKET_HOST || !ddp->deh_dnet) {
		/*
		 * FIXME:
		 *
		 * Can it ever happen that a packet is from a PPP iface and
		 * needs to be broadcast onto the default network?
		 */
		if (dev->type == ARPHRD_PPP)
			printk(KERN_DEBUG "AppleTalk: didn't forward broadcast "
					  "packet received from PPP iface\n");
		goto free_it;
	}

	ta.s_net  = ddp->deh_dnet;
	ta.s_node = ddp->deh_dnode;

	/* Route the packet */
	rt = atrtr_find(&ta);
	/* increment hops count */
	len_hops += 1 << 10;
	if (!rt || !(len_hops & (15 << 10)))
		goto free_it;

	/* FIXME: use skb->cb to be able to use shared skbs */

	/*
	 * Route goes through another gateway, so set the target to the
	 * gateway instead.
	 */

	if (rt->flags & RTF_GATEWAY) {
		ta.s_net  = rt->gateway.s_net;
		ta.s_node = rt->gateway.s_node;
	}

	/* Fix up skb->len field */
	skb_trim(skb, min_t(unsigned int, origlen,
			    (rt->dev->hard_header_len +
			     ddp_dl->header_length + (len_hops & 1023))));

	/* FIXME: use skb->cb to be able to use shared skbs */
	ddp->deh_len_hops = htons(len_hops);

	/*
	 * Send the buffer onwards
	 *
	 * Now we must always be careful. If it's come from LocalTalk to
	 * EtherTalk it might not fit
	 *
	 * Order matters here: If a packet has to be copied to make a new
	 * headroom (rare hopefully) then it won't need unsharing.
	 *
	 * Note. ddp-> becomes invalid at the realloc.
	 */
	if (skb_headroom(skb) < 22) {
		/* 22 bytes - 12 ether, 2 len, 3 802.2 5 snap */
		struct sk_buff *nskb = skb_realloc_headroom(skb, 32);
		kfree_skb(skb);
		skb = nskb;
	} else
		skb = skb_unshare(skb, GFP_ATOMIC);

	/*
	 * If the buffer didn't vanish into the lack of space bitbucket we can
	 * send it.
	 */
	if (skb == NULL)
		goto drop;

	if (aarp_send_ddp(rt->dev, skb, &ta, NULL) == NET_XMIT_DROP)
		return NET_RX_DROP;
	return NET_RX_SUCCESS;
free_it:
	kfree_skb(skb);
drop:
	return NET_RX_DROP;
}

/**
 *	atalk_rcv - Receive a packet (in skb) from device dev
 *	@skb - packet received
 *	@dev - network device where the packet comes from
 *	@pt - packet type
 *
 *	Receive a packet (in skb) from device dev. This has come from the SNAP
 *	decoder, and on entry skb->transport_header is the DDP header, skb->len
 *	is the DDP header, skb->len is the DDP length. The physical headers
 *	have been extracted. PPP should probably pass frames marked as for this
 *	layer.  [ie ARPHRD_ETHERTALK]
 */
static int atalk_rcv(struct sk_buff *skb, struct net_device *dev,
		     struct packet_type *pt, struct net_device *orig_dev)
{
	struct ddpehdr *ddp;
	struct sock *sock;
	struct atalk_iface *atif;
	struct sockaddr_at tosat;
	int origlen;
	__u16 len_hops;

	if (!net_eq(dev_net(dev), &init_net))
		goto drop;

	/* Don't mangle buffer if shared */
	if (!(skb = skb_share_check(skb, GFP_ATOMIC)))
		goto out;

	/* Size check and make sure header is contiguous */
	if (!pskb_may_pull(skb, sizeof(*ddp)))
		goto drop;

	ddp = ddp_hdr(skb);

	len_hops = ntohs(ddp->deh_len_hops);

	/* Trim buffer in case of stray trailing data */
	origlen = skb->len;
	skb_trim(skb, min_t(unsigned int, skb->len, len_hops & 1023));

	/*
	 * Size check to see if ddp->deh_len was crap
	 * (Otherwise we'll detonate most spectacularly
	 * in the middle of atalk_checksum() or recvmsg()).
	 */
	if (skb->len < sizeof(*ddp) || skb->len < (len_hops & 1023)) {
		pr_debug("AppleTalk: dropping corrupted frame (deh_len=%u, "
			 "skb->len=%u)\n", len_hops & 1023, skb->len);
		goto drop;
	}

	/*
	 * Any checksums. Note we don't do htons() on this == is assumed to be
	 * valid for net byte orders all over the networking code...
	 */
	if (ddp->deh_sum &&
	    atalk_checksum(skb, len_hops & 1023) != ddp->deh_sum)
		/* Not a valid AppleTalk frame - dustbin time */
		goto drop;

	/* Check the packet is aimed at us */
	if (!ddp->deh_dnet)	/* Net 0 is 'this network' */
		atif = atalk_find_anynet(ddp->deh_dnode, dev);
	else
		atif = atalk_find_interface(ddp->deh_dnet, ddp->deh_dnode);

	if (!atif) {
		/* Not ours, so we route the packet via the correct
		 * AppleTalk iface
		 */
		return atalk_route_packet(skb, dev, ddp, len_hops, origlen);
	}

	/* if IP over DDP is not selected this code will be optimized out */
	if (is_ip_over_ddp(skb))
		return handle_ip_over_ddp(skb);
	/*
	 * Which socket - atalk_search_socket() looks for a *full match*
	 * of the <net, node, port> tuple.
	 */
	tosat.sat_addr.s_net  = ddp->deh_dnet;
	tosat.sat_addr.s_node = ddp->deh_dnode;
	tosat.sat_port	      = ddp->deh_dport;

	sock = atalk_search_socket(&tosat, atif);
	if (!sock) /* But not one of our sockets */
		goto drop;

	/* Queue packet (standard) */
	if (sock_queue_rcv_skb(sock, skb) < 0)
		goto drop;

	return NET_RX_SUCCESS;

drop:
	kfree_skb(skb);
out:
	return NET_RX_DROP;

}

/*
 * Receive a LocalTalk frame. We make some demands on the caller here.
 * Caller must provide enough headroom on the packet to pull the short
 * header and append a long one.
 */
static int ltalk_rcv(struct sk_buff *skb, struct net_device *dev,
		     struct packet_type *pt, struct net_device *orig_dev)
{
	if (!net_eq(dev_net(dev), &init_net))
		goto freeit;

	/* Expand any short form frames */
	if (skb_mac_header(skb)[2] == 1) {
		struct ddpehdr *ddp;
		/* Find our address */
		struct atalk_addr *ap = atalk_find_dev_addr(dev);

		if (!ap || skb->len < sizeof(__be16) || skb->len > 1023)
			goto freeit;

		/* Don't mangle buffer if shared */
		if (!(skb = skb_share_check(skb, GFP_ATOMIC)))
			return 0;

		/*
		 * The push leaves us with a ddephdr not an shdr, and
		 * handily the port bytes in the right place preset.
		 */
		ddp = skb_push(skb, sizeof(*ddp) - 4);

		/* Now fill in the long header */

		/*
		 * These two first. The mac overlays the new source/dest
		 * network information so we MUST copy these before
		 * we write the network numbers !
		 */

		ddp->deh_dnode = skb_mac_header(skb)[0];     /* From physical header */
		ddp->deh_snode = skb_mac_header(skb)[1];     /* From physical header */

		ddp->deh_dnet  = ap->s_net;	/* Network number */
		ddp->deh_snet  = ap->s_net;
		ddp->deh_sum   = 0;		/* No checksum */
		/*
		 * Not sure about this bit...
		 */
		/* Non routable, so force a drop if we slip up later */
		ddp->deh_len_hops = htons(skb->len + (DDP_MAXHOPS << 10));
	}
	skb_reset_transport_header(skb);

	return atalk_rcv(skb, dev, pt, orig_dev);
freeit:
	kfree_skb(skb);
	return 0;
}

static int atalk_sendmsg(struct socket *sock, struct msghdr *msg, size_t len)
{
	struct sock *sk = sock->sk;
	struct atalk_sock *at = at_sk(sk);
	DECLARE_SOCKADDR(struct sockaddr_at *, usat, msg->msg_name);
	int flags = msg->msg_flags;
	int loopback = 0;
	struct sockaddr_at local_satalk, gsat;
	struct sk_buff *skb;
	struct net_device *dev;
	struct ddpehdr *ddp;
	int size;
	struct atalk_route *rt;
	int err;

	if (flags & ~(MSG_DONTWAIT|MSG_CMSG_COMPAT))
		return -EINVAL;

	if (len > DDP_MAXSZ)
		return -EMSGSIZE;

	lock_sock(sk);
	if (usat) {
		err = -EBUSY;
		if (sock_flag(sk, SOCK_ZAPPED))
			if (atalk_autobind(sk) < 0)
				goto out;

		err = -EINVAL;
		if (msg->msg_namelen < sizeof(*usat) ||
		    usat->sat_family != AF_APPLETALK)
			goto out;

		err = -EPERM;
		/* netatalk didn't implement this check */
		if (usat->sat_addr.s_node == ATADDR_BCAST &&
		    !sock_flag(sk, SOCK_BROADCAST)) {
			goto out;
		}
	} else {
		err = -ENOTCONN;
		if (sk->sk_state != TCP_ESTABLISHED)
			goto out;
		usat = &local_satalk;
		usat->sat_family      = AF_APPLETALK;
		usat->sat_port	      = at->dest_port;
		usat->sat_addr.s_node = at->dest_node;
		usat->sat_addr.s_net  = at->dest_net;
	}

	/* Build a packet */
	SOCK_DEBUG(sk, "SK %p: Got address.\n", sk);

	/* For headers */
	size = sizeof(struct ddpehdr) + len + ddp_dl->header_length;

	if (usat->sat_addr.s_net || usat->sat_addr.s_node == ATADDR_ANYNODE) {
		rt = atrtr_find(&usat->sat_addr);
	} else {
		struct atalk_addr at_hint;

		at_hint.s_node = 0;
		at_hint.s_net  = at->src_net;

		rt = atrtr_find(&at_hint);
	}
	err = -ENETUNREACH;
	if (!rt)
		goto out;

	dev = rt->dev;

	SOCK_DEBUG(sk, "SK %p: Size needed %d, device %s\n",
			sk, size, dev->name);

	size += dev->hard_header_len;
	release_sock(sk);
	skb = sock_alloc_send_skb(sk, size, (flags & MSG_DONTWAIT), &err);
	lock_sock(sk);
	if (!skb)
		goto out;

	skb_reserve(skb, ddp_dl->header_length);
	skb_reserve(skb, dev->hard_header_len);
	skb->dev = dev;

	SOCK_DEBUG(sk, "SK %p: Begin build.\n", sk);

	ddp = skb_put(skb, sizeof(struct ddpehdr));
	ddp->deh_len_hops  = htons(len + sizeof(*ddp));
	ddp->deh_dnet  = usat->sat_addr.s_net;
	ddp->deh_snet  = at->src_net;
	ddp->deh_dnode = usat->sat_addr.s_node;
	ddp->deh_snode = at->src_node;
	ddp->deh_dport = usat->sat_port;
	ddp->deh_sport = at->src_port;

	SOCK_DEBUG(sk, "SK %p: Copy user data (%zd bytes).\n", sk, len);

	err = memcpy_from_msg(skb_put(skb, len), msg, len);
	if (err) {
		kfree_skb(skb);
		err = -EFAULT;
		goto out;
	}

	if (sk->sk_no_check_tx)
		ddp->deh_sum = 0;
	else
		ddp->deh_sum = atalk_checksum(skb, len + sizeof(*ddp));

	/*
	 * Loopback broadcast packets to non gateway targets (ie routes
	 * to group we are in)
	 */
	if (ddp->deh_dnode == ATADDR_BCAST &&
	    !(rt->flags & RTF_GATEWAY) && !(dev->flags & IFF_LOOPBACK)) {
		struct sk_buff *skb2 = skb_copy(skb, GFP_KERNEL);

		if (skb2) {
			loopback = 1;
			SOCK_DEBUG(sk, "SK %p: send out(copy).\n", sk);
			/*
			 * If it fails it is queued/sent above in the aarp queue
			 */
			aarp_send_ddp(dev, skb2, &usat->sat_addr, NULL);
		}
	}

	if (dev->flags & IFF_LOOPBACK || loopback) {
		SOCK_DEBUG(sk, "SK %p: Loop back.\n", sk);
		/* loop back */
		skb_orphan(skb);
		if (ddp->deh_dnode == ATADDR_BCAST) {
			struct atalk_addr at_lo;

			at_lo.s_node = 0;
			at_lo.s_net  = 0;

			rt = atrtr_find(&at_lo);
			if (!rt) {
				kfree_skb(skb);
				err = -ENETUNREACH;
				goto out;
			}
			dev = rt->dev;
			skb->dev = dev;
		}
		ddp_dl->request(ddp_dl, skb, dev->dev_addr);
	} else {
		SOCK_DEBUG(sk, "SK %p: send out.\n", sk);
		if (rt->flags & RTF_GATEWAY) {
		    gsat.sat_addr = rt->gateway;
		    usat = &gsat;
		}

		/*
		 * If it fails it is queued/sent above in the aarp queue
		 */
		aarp_send_ddp(dev, skb, &usat->sat_addr, NULL);
	}
	SOCK_DEBUG(sk, "SK %p: Done write (%zd).\n", sk, len);

out:
	release_sock(sk);
	return err ? : len;
}

static int atalk_recvmsg(struct socket *sock, struct msghdr *msg, size_t size,
			 int flags)
{
	struct sock *sk = sock->sk;
	struct ddpehdr *ddp;
	int copied = 0;
	int offset = 0;
	int err = 0;
	struct sk_buff *skb;

	skb = skb_recv_datagram(sk, flags & ~MSG_DONTWAIT,
						flags & MSG_DONTWAIT, &err);
	lock_sock(sk);

	if (!skb)
		goto out;

	/* FIXME: use skb->cb to be able to use shared skbs */
	ddp = ddp_hdr(skb);
	copied = ntohs(ddp->deh_len_hops) & 1023;

	if (sk->sk_type != SOCK_RAW) {
		offset = sizeof(*ddp);
		copied -= offset;
	}

	if (copied > size) {
		copied = size;
		msg->msg_flags |= MSG_TRUNC;
	}
	err = skb_copy_datagram_msg(skb, offset, msg, copied);

	if (!err && msg->msg_name) {
		DECLARE_SOCKADDR(struct sockaddr_at *, sat, msg->msg_name);
		sat->sat_family      = AF_APPLETALK;
		sat->sat_port        = ddp->deh_sport;
		sat->sat_addr.s_node = ddp->deh_snode;
		sat->sat_addr.s_net  = ddp->deh_snet;
		msg->msg_namelen     = sizeof(*sat);
	}

	skb_free_datagram(sk, skb);	/* Free the datagram. */

out:
	release_sock(sk);
	return err ? : copied;
}


/*
 * AppleTalk ioctl calls.
 */
static int atalk_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
	int rc = -ENOIOCTLCMD;
	struct sock *sk = sock->sk;
	void __user *argp = (void __user *)arg;

	switch (cmd) {
	/* Protocol layer */
	case TIOCOUTQ: {
		long amount = sk->sk_sndbuf - sk_wmem_alloc_get(sk);

		if (amount < 0)
			amount = 0;
		rc = put_user(amount, (int __user *)argp);
		break;
	}
	case TIOCINQ: {
		/*
		 * These two are safe on a single CPU system as only
		 * user tasks fiddle here
		 */
		struct sk_buff *skb = skb_peek(&sk->sk_receive_queue);
		long amount = 0;

		if (skb)
			amount = skb->len - sizeof(struct ddpehdr);
		rc = put_user(amount, (int __user *)argp);
		break;
	}
	/* Routing */
	case SIOCADDRT:
	case SIOCDELRT:
		rc = -EPERM;
		if (capable(CAP_NET_ADMIN))
			rc = atrtr_ioctl(cmd, argp);
		break;
	/* Interface */
	case SIOCGIFADDR:
	case SIOCSIFADDR:
	case SIOCGIFBRDADDR:
	case SIOCATALKDIFADDR:
	case SIOCDIFADDR:
	case SIOCSARP:		/* proxy AARP */
	case SIOCDARP:		/* proxy AARP */
		rtnl_lock();
		rc = atif_ioctl(cmd, argp);
		rtnl_unlock();
		break;
	}

	return rc;
}


#ifdef CONFIG_COMPAT
static int atalk_compat_ioctl(struct socket *sock, unsigned int cmd, unsigned long arg)
{
	/*
	 * SIOCATALKDIFADDR is a SIOCPROTOPRIVATE ioctl number, so we
	 * cannot handle it in common code. The data we access if ifreq
	 * here is compatible, so we can simply call the native
	 * handler.
	 */
	if (cmd == SIOCATALKDIFADDR)
		return atalk_ioctl(sock, cmd, (unsigned long)compat_ptr(arg));

	return -ENOIOCTLCMD;
}
#endif


static const struct net_proto_family atalk_family_ops = {
	.family		= PF_APPLETALK,
	.create		= atalk_create,
	.owner		= THIS_MODULE,
};

static const struct proto_ops atalk_dgram_ops = {
	.family		= PF_APPLETALK,
	.owner		= THIS_MODULE,
	.release	= atalk_release,
	.bind		= atalk_bind,
	.connect	= atalk_connect,
	.socketpair	= sock_no_socketpair,
	.accept		= sock_no_accept,
	.getname	= atalk_getname,
	.poll		= datagram_poll,
	.ioctl		= atalk_ioctl,
	.gettstamp	= sock_gettstamp,
#ifdef CONFIG_COMPAT
	.compat_ioctl	= atalk_compat_ioctl,
#endif
	.listen		= sock_no_listen,
	.shutdown	= sock_no_shutdown,
	.setsockopt	= sock_no_setsockopt,
	.getsockopt	= sock_no_getsockopt,
	.sendmsg	= atalk_sendmsg,
	.recvmsg	= atalk_recvmsg,
	.mmap		= sock_no_mmap,
	.sendpage	= sock_no_sendpage,
};

static struct notifier_block ddp_notifier = {
	.notifier_call	= ddp_device_event,
};

static struct packet_type ltalk_packet_type __read_mostly = {
	.type		= cpu_to_be16(ETH_P_LOCALTALK),
	.func		= ltalk_rcv,
};

static struct packet_type ppptalk_packet_type __read_mostly = {
	.type		= cpu_to_be16(ETH_P_PPPTALK),
	.func		= atalk_rcv,
};

static unsigned char ddp_snap_id[] = { 0x08, 0x00, 0x07, 0x80, 0x9B };

/* Export symbols for use by drivers when AppleTalk is a module */
EXPORT_SYMBOL(atrtr_get_dev);
EXPORT_SYMBOL(atalk_find_dev_addr);

/* Called by proto.c on kernel start up */
static int __init atalk_init(void)
{
	int rc;

	rc = proto_register(&ddp_proto, 0);
	if (rc)
		goto out;

	rc = sock_register(&atalk_family_ops);
	if (rc)
		goto out_proto;

	ddp_dl = register_snap_client(ddp_snap_id, atalk_rcv);
	if (!ddp_dl) {
		pr_crit("Unable to register DDP with SNAP.\n");
		rc = -ENOMEM;
		goto out_sock;
	}

	dev_add_pack(&ltalk_packet_type);
	dev_add_pack(&ppptalk_packet_type);

	rc = register_netdevice_notifier(&ddp_notifier);
	if (rc)
		goto out_snap;

	rc = aarp_proto_init();
	if (rc)
		goto out_dev;

	rc = atalk_proc_init();
	if (rc)
		goto out_aarp;

	rc = atalk_register_sysctl();
	if (rc)
		goto out_proc;
out:
	return rc;
out_proc:
	atalk_proc_exit();
out_aarp:
	aarp_cleanup_module();
out_dev:
	unregister_netdevice_notifier(&ddp_notifier);
out_snap:
	dev_remove_pack(&ppptalk_packet_type);
	dev_remove_pack(&ltalk_packet_type);
	unregister_snap_client(ddp_dl);
out_sock:
	sock_unregister(PF_APPLETALK);
out_proto:
	proto_unregister(&ddp_proto);
	goto out;
}
module_init(atalk_init);

/*
 * No explicit module reference count manipulation is needed in the
 * protocol. Socket layer sets module reference count for us
 * and interfaces reference counting is done
 * by the network device layer.
 *
 * Ergo, before the AppleTalk module can be removed, all AppleTalk
 * sockets be closed from user space.
 */
static void __exit atalk_exit(void)
{
#ifdef CONFIG_SYSCTL
	atalk_unregister_sysctl();
#endif /* CONFIG_SYSCTL */
	atalk_proc_exit();
	aarp_cleanup_module();	/* General aarp clean-up. */
	unregister_netdevice_notifier(&ddp_notifier);
	dev_remove_pack(&ltalk_packet_type);
	dev_remove_pack(&ppptalk_packet_type);
	unregister_snap_client(ddp_dl);
	sock_unregister(PF_APPLETALK);
	proto_unregister(&ddp_proto);
}
module_exit(atalk_exit);

MODULE_LICENSE("GPL");
MODULE_AUTHOR("Alan Cox <alan@lxorguk.ukuu.org.uk>");
MODULE_DESCRIPTION("AppleTalk 0.20\n");
MODULE_ALIAS_NETPROTO(PF_APPLETALK);