/*
 *      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
 *
 *              This program is free software; you can redistribute it and/or
 *              modify it under the terms of the GNU General Public License
 *              as published by the Free Software Foundation; either version
 *              2 of the License, or (at your option) any later version.
 *
 */

#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;
        }
        case SIOCGSTAMP:
                rc = sock_get_timestamp(sk, argp);
                break;
        case SIOCGSTAMPNS:
                rc = sock_get_timestampns(sk, 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,
#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);

static const char atalk_err_snap[] __initconst =
        KERN_CRIT "Unable to register DDP with SNAP.\n";

/* Called by proto.c on kernel start up */
static int __init atalk_init(void)
{
        int rc = proto_register(&ddp_proto, 0);

        if (rc != 0)
                goto out;

        (void)sock_register(&atalk_family_ops);
        ddp_dl = register_snap_client(ddp_snap_id, atalk_rcv);
        if (!ddp_dl)
                printk(atalk_err_snap);

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

        register_netdevice_notifier(&ddp_notifier);
        aarp_proto_init();
        atalk_proc_init();
        atalk_register_sysctl();
out:
        return rc;
}
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);