/*
 * DECnet       An implementation of the DECnet protocol suite for the LINUX
 *              operating system.  DECnet is implemented using the  BSD Socket
 *              interface as the means of communication with the user level.
 *
 *              DECnet Routing Functions (Endnode and Router)
 *
 * Authors:     Steve Whitehouse <SteveW@ACM.org>
 *              Eduardo Marcelo Serrat <emserrat@geocities.com>
 *
 * Changes:
 *              Steve Whitehouse : Fixes to allow "intra-ethernet" and
 *                                 "return-to-sender" bits on outgoing
 *                                 packets.
 *              Steve Whitehouse : Timeouts for cached routes.
 *              Steve Whitehouse : Use dst cache for input routes too.
 *              Steve Whitehouse : Fixed error values in dn_send_skb.
 *              Steve Whitehouse : Rework routing functions to better fit
 *                                 DECnet routing design
 *              Alexey Kuznetsov : New SMP locking
 *              Steve Whitehouse : More SMP locking changes & dn_cache_dump()
 *              Steve Whitehouse : Prerouting NF hook, now really is prerouting.
 *                                 Fixed possible skb leak in rtnetlink funcs.
 *              Steve Whitehouse : Dave Miller's dynamic hash table sizing and
 *                                 Alexey Kuznetsov's finer grained locking
 *                                 from ipv4/route.c.
 *              Steve Whitehouse : Routing is now starting to look like a
 *                                 sensible set of code now, mainly due to
 *                                 my copying the IPv4 routing code. The
 *                                 hooks here are modified and will continue
 *                                 to evolve for a while.
 *              Steve Whitehouse : Real SMP at last :-) Also new netfilter
 *                                 stuff. Look out raw sockets your days
 *                                 are numbered!
 *              Steve Whitehouse : Added return-to-sender functions. Added
 *                                 backlog congestion level return codes.
 *              Steve Whitehouse : Fixed bug where routes were set up with
 *                                 no ref count on net devices.
 *              Steve Whitehouse : RCU for the route cache
 *              Steve Whitehouse : Preparations for the flow cache
 *              Steve Whitehouse : Prepare for nonlinear skbs
 */

/******************************************************************************
    (c) 1995-1998 E.M. Serrat           emserrat@geocities.com

    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
    any later version.

    This program is distributed in the hope that it will be useful,
    but WITHOUT ANY WARRANTY; without even the implied warranty of
    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
    GNU General Public License for more details.
*******************************************************************************/

#include <linux/errno.h>
#include <linux/types.h>
#include <linux/socket.h>
#include <linux/in.h>
#include <linux/kernel.h>
#include <linux/sockios.h>
#include <linux/net.h>
#include <linux/netdevice.h>
#include <linux/inet.h>
#include <linux/route.h>
#include <linux/in_route.h>
#include <linux/slab.h>
#include <net/sock.h>
#include <linux/mm.h>
#include <linux/proc_fs.h>
#include <linux/seq_file.h>
#include <linux/init.h>
#include <linux/rtnetlink.h>
#include <linux/string.h>
#include <linux/netfilter_decnet.h>
#include <linux/rcupdate.h>
#include <linux/times.h>
#include <asm/errno.h>
#include <net/net_namespace.h>
#include <net/netlink.h>
#include <net/neighbour.h>
#include <net/dst.h>
#include <net/flow.h>
#include <net/fib_rules.h>
#include <net/dn.h>
#include <net/dn_dev.h>
#include <net/dn_nsp.h>
#include <net/dn_route.h>
#include <net/dn_neigh.h>
#include <net/dn_fib.h>

struct dn_rt_hash_bucket
{
        struct dn_route __rcu *chain;
        spinlock_t lock;
};

extern struct neigh_table dn_neigh_table;


static unsigned char dn_hiord_addr[6] = {0xAA,0x00,0x04,0x00,0x00,0x00};

static const int dn_rt_min_delay = 2 * HZ;
static const int dn_rt_max_delay = 10 * HZ;
static const int dn_rt_mtu_expires = 10 * 60 * HZ;

static unsigned long dn_rt_deadline;

static int dn_dst_gc(struct dst_ops *ops);
static struct dst_entry *dn_dst_check(struct dst_entry *, __u32);
static unsigned int dn_dst_default_advmss(const struct dst_entry *dst);
static unsigned int dn_dst_default_mtu(const struct dst_entry *dst);
static struct dst_entry *dn_dst_negative_advice(struct dst_entry *);
static void dn_dst_link_failure(struct sk_buff *);
static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu);
static int dn_route_input(struct sk_buff *);
static void dn_run_flush(unsigned long dummy);

static struct dn_rt_hash_bucket *dn_rt_hash_table;
static unsigned dn_rt_hash_mask;

static struct timer_list dn_route_timer;
static DEFINE_TIMER(dn_rt_flush_timer, dn_run_flush, 0, 0);
int decnet_dst_gc_interval = 2;

static struct dst_ops dn_dst_ops = {
        .family =               PF_DECnet,
        .protocol =             cpu_to_be16(ETH_P_DNA_RT),
        .gc_thresh =            128,
        .gc =                   dn_dst_gc,
        .check =                dn_dst_check,
        .default_advmss =       dn_dst_default_advmss,
        .default_mtu =          dn_dst_default_mtu,
        .negative_advice =      dn_dst_negative_advice,
        .link_failure =         dn_dst_link_failure,
        .update_pmtu =          dn_dst_update_pmtu,
};

static __inline__ unsigned dn_hash(__le16 src, __le16 dst)
{
        __u16 tmp = (__u16 __force)(src ^ dst);
        tmp ^= (tmp >> 3);
        tmp ^= (tmp >> 5);
        tmp ^= (tmp >> 10);
        return dn_rt_hash_mask & (unsigned)tmp;
}

static inline void dnrt_free(struct dn_route *rt)
{
        call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free);
}

static inline void dnrt_drop(struct dn_route *rt)
{
        dst_release(&rt->dst);
        call_rcu_bh(&rt->dst.rcu_head, dst_rcu_free);
}

static void dn_dst_check_expire(unsigned long dummy)
{
        int i;
        struct dn_route *rt;
        struct dn_route __rcu **rtp;
        unsigned long now = jiffies;
        unsigned long expire = 120 * HZ;

        for (i = 0; i <= dn_rt_hash_mask; i++) {
                rtp = &dn_rt_hash_table[i].chain;

                spin_lock(&dn_rt_hash_table[i].lock);
                while ((rt = rcu_dereference_protected(*rtp,
                                                lockdep_is_held(&dn_rt_hash_table[i].lock))) != NULL) {
                        if (atomic_read(&rt->dst.__refcnt) ||
                                        (now - rt->dst.lastuse) < expire) {
                                rtp = &rt->dst.dn_next;
                                continue;
                        }
                        *rtp = rt->dst.dn_next;
                        rt->dst.dn_next = NULL;
                        dnrt_free(rt);
                }
                spin_unlock(&dn_rt_hash_table[i].lock);

                if ((jiffies - now) > 0)
                        break;
        }

        mod_timer(&dn_route_timer, now + decnet_dst_gc_interval * HZ);
}

static int dn_dst_gc(struct dst_ops *ops)
{
        struct dn_route *rt;
        struct dn_route __rcu **rtp;
        int i;
        unsigned long now = jiffies;
        unsigned long expire = 10 * HZ;

        for (i = 0; i <= dn_rt_hash_mask; i++) {

                spin_lock_bh(&dn_rt_hash_table[i].lock);
                rtp = &dn_rt_hash_table[i].chain;

                while ((rt = rcu_dereference_protected(*rtp,
                                                lockdep_is_held(&dn_rt_hash_table[i].lock))) != NULL) {
                        if (atomic_read(&rt->dst.__refcnt) ||
                                        (now - rt->dst.lastuse) < expire) {
                                rtp = &rt->dst.dn_next;
                                continue;
                        }
                        *rtp = rt->dst.dn_next;
                        rt->dst.dn_next = NULL;
                        dnrt_drop(rt);
                        break;
                }
                spin_unlock_bh(&dn_rt_hash_table[i].lock);
        }

        return 0;
}

/*
 * The decnet standards don't impose a particular minimum mtu, what they
 * do insist on is that the routing layer accepts a datagram of at least
 * 230 bytes long. Here we have to subtract the routing header length from
 * 230 to get the minimum acceptable mtu. If there is no neighbour, then we
 * assume the worst and use a long header size.
 *
 * We update both the mtu and the advertised mss (i.e. the segment size we
 * advertise to the other end).
 */
static void dn_dst_update_pmtu(struct dst_entry *dst, u32 mtu)
{
        u32 min_mtu = 230;
        struct dn_dev *dn = dst->neighbour ?
                            rcu_dereference_raw(dst->neighbour->dev->dn_ptr) : NULL;

        if (dn && dn->use_long == 0)
                min_mtu -= 6;
        else
                min_mtu -= 21;

        if (dst_metric(dst, RTAX_MTU) > mtu && mtu >= min_mtu) {
                if (!(dst_metric_locked(dst, RTAX_MTU))) {
                        dst_metric_set(dst, RTAX_MTU, mtu);
                        dst_set_expires(dst, dn_rt_mtu_expires);
                }
                if (!(dst_metric_locked(dst, RTAX_ADVMSS))) {
                        u32 mss = mtu - DN_MAX_NSP_DATA_HEADER;
                        u32 existing_mss = dst_metric_raw(dst, RTAX_ADVMSS);
                        if (!existing_mss || existing_mss > mss)
                                dst_metric_set(dst, RTAX_ADVMSS, mss);
                }
        }
}

/*
 * When a route has been marked obsolete. (e.g. routing cache flush)
 */
static struct dst_entry *dn_dst_check(struct dst_entry *dst, __u32 cookie)
{
        return NULL;
}

static struct dst_entry *dn_dst_negative_advice(struct dst_entry *dst)
{
        dst_release(dst);
        return NULL;
}

static void dn_dst_link_failure(struct sk_buff *skb)
{
}

static inline int compare_keys(struct flowi *fl1, struct flowi *fl2)
{
        return ((fl1->fld_dst ^ fl2->fld_dst) |
                (fl1->fld_src ^ fl2->fld_src) |
                (fl1->mark ^ fl2->mark) |
                (fl1->fld_scope ^ fl2->fld_scope) |
                (fl1->oif ^ fl2->oif) |
                (fl1->iif ^ fl2->iif)) == 0;
}

static int dn_insert_route(struct dn_route *rt, unsigned hash, struct dn_route **rp)
{
        struct dn_route *rth;
        struct dn_route __rcu **rthp;
        unsigned long now = jiffies;

        rthp = &dn_rt_hash_table[hash].chain;

        spin_lock_bh(&dn_rt_hash_table[hash].lock);
        while ((rth = rcu_dereference_protected(*rthp,
                                                lockdep_is_held(&dn_rt_hash_table[hash].lock))) != NULL) {
                if (compare_keys(&rth->fl, &rt->fl)) {
                        /* Put it first */
                        *rthp = rth->dst.dn_next;
                        rcu_assign_pointer(rth->dst.dn_next,
                                           dn_rt_hash_table[hash].chain);
                        rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth);

                        dst_use(&rth->dst, now);
                        spin_unlock_bh(&dn_rt_hash_table[hash].lock);

                        dnrt_drop(rt);
                        *rp = rth;
                        return 0;
                }
                rthp = &rth->dst.dn_next;
        }

        rcu_assign_pointer(rt->dst.dn_next, dn_rt_hash_table[hash].chain);
        rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt);

        dst_use(&rt->dst, now);
        spin_unlock_bh(&dn_rt_hash_table[hash].lock);
        *rp = rt;
        return 0;
}

static void dn_run_flush(unsigned long dummy)
{
        int i;
        struct dn_route *rt, *next;

        for (i = 0; i < dn_rt_hash_mask; i++) {
                spin_lock_bh(&dn_rt_hash_table[i].lock);

                if ((rt = xchg((struct dn_route **)&dn_rt_hash_table[i].chain, NULL)) == NULL)
                        goto nothing_to_declare;

                for(; rt; rt = next) {
                        next = rcu_dereference_raw(rt->dst.dn_next);
                        RCU_INIT_POINTER(rt->dst.dn_next, NULL);
                        dst_free((struct dst_entry *)rt);
                }

nothing_to_declare:
                spin_unlock_bh(&dn_rt_hash_table[i].lock);
        }
}

static DEFINE_SPINLOCK(dn_rt_flush_lock);

void dn_rt_cache_flush(int delay)
{
        unsigned long now = jiffies;
        int user_mode = !in_interrupt();

        if (delay < 0)
                delay = dn_rt_min_delay;

        spin_lock_bh(&dn_rt_flush_lock);

        if (del_timer(&dn_rt_flush_timer) && delay > 0 && dn_rt_deadline) {
                long tmo = (long)(dn_rt_deadline - now);

                if (user_mode && tmo < dn_rt_max_delay - dn_rt_min_delay)
                        tmo = 0;

                if (delay > tmo)
                        delay = tmo;
        }

        if (delay <= 0) {
                spin_unlock_bh(&dn_rt_flush_lock);
                dn_run_flush(0);
                return;
        }

        if (dn_rt_deadline == 0)
                dn_rt_deadline = now + dn_rt_max_delay;

        dn_rt_flush_timer.expires = now + delay;
        add_timer(&dn_rt_flush_timer);
        spin_unlock_bh(&dn_rt_flush_lock);
}

/**
 * dn_return_short - Return a short packet to its sender
 * @skb: The packet to return
 *
 */
static int dn_return_short(struct sk_buff *skb)
{
        struct dn_skb_cb *cb;
        unsigned char *ptr;
        __le16 *src;
        __le16 *dst;

        /* Add back headers */
        skb_push(skb, skb->data - skb_network_header(skb));

        if ((skb = skb_unshare(skb, GFP_ATOMIC)) == NULL)
                return NET_RX_DROP;

        cb = DN_SKB_CB(skb);
        /* Skip packet length and point to flags */
        ptr = skb->data + 2;
        *ptr++ = (cb->rt_flags & ~DN_RT_F_RQR) | DN_RT_F_RTS;

        dst = (__le16 *)ptr;
        ptr += 2;
        src = (__le16 *)ptr;
        ptr += 2;
        *ptr = 0; /* Zero hop count */

        swap(*src, *dst);

        skb->pkt_type = PACKET_OUTGOING;
        dn_rt_finish_output(skb, NULL, NULL);
        return NET_RX_SUCCESS;
}

/**
 * dn_return_long - Return a long packet to its sender
 * @skb: The long format packet to return
 *
 */
static int dn_return_long(struct sk_buff *skb)
{
        struct dn_skb_cb *cb;
        unsigned char *ptr;
        unsigned char *src_addr, *dst_addr;
        unsigned char tmp[ETH_ALEN];

        /* Add back all headers */
        skb_push(skb, skb->data - skb_network_header(skb));

        if ((skb = skb_unshare(skb, GFP_ATOMIC)) == NULL)
                return NET_RX_DROP;

        cb = DN_SKB_CB(skb);
        /* Ignore packet length and point to flags */
        ptr = skb->data + 2;

        /* Skip padding */
        if (*ptr & DN_RT_F_PF) {
                char padlen = (*ptr & ~DN_RT_F_PF);
                ptr += padlen;
        }

        *ptr++ = (cb->rt_flags & ~DN_RT_F_RQR) | DN_RT_F_RTS;
        ptr += 2;
        dst_addr = ptr;
        ptr += 8;
        src_addr = ptr;
        ptr += 6;
        *ptr = 0; /* Zero hop count */

        /* Swap source and destination */
        memcpy(tmp, src_addr, ETH_ALEN);
        memcpy(src_addr, dst_addr, ETH_ALEN);
        memcpy(dst_addr, tmp, ETH_ALEN);

        skb->pkt_type = PACKET_OUTGOING;
        dn_rt_finish_output(skb, dst_addr, src_addr);
        return NET_RX_SUCCESS;
}

/**
 * dn_route_rx_packet - Try and find a route for an incoming packet
 * @skb: The packet to find a route for
 *
 * Returns: result of input function if route is found, error code otherwise
 */
static int dn_route_rx_packet(struct sk_buff *skb)
{
        struct dn_skb_cb *cb;
        int err;

        if ((err = dn_route_input(skb)) == 0)
                return dst_input(skb);

        cb = DN_SKB_CB(skb);
        if (decnet_debug_level & 4) {
                char *devname = skb->dev ? skb->dev->name : "???";

                printk(KERN_DEBUG
                        "DECnet: dn_route_rx_packet: rt_flags=0x%02x dev=%s len=%d src=0x%04hx dst=0x%04hx err=%d type=%d\n",
                        (int)cb->rt_flags, devname, skb->len,
                        le16_to_cpu(cb->src), le16_to_cpu(cb->dst),
                        err, skb->pkt_type);
        }

        if ((skb->pkt_type == PACKET_HOST) && (cb->rt_flags & DN_RT_F_RQR)) {
                switch(cb->rt_flags & DN_RT_PKT_MSK) {
                        case DN_RT_PKT_SHORT:
                                return dn_return_short(skb);
                        case DN_RT_PKT_LONG:
                                return dn_return_long(skb);
                }
        }

        kfree_skb(skb);
        return NET_RX_DROP;
}

static int dn_route_rx_long(struct sk_buff *skb)
{
        struct dn_skb_cb *cb = DN_SKB_CB(skb);
        unsigned char *ptr = skb->data;

        if (!pskb_may_pull(skb, 21)) /* 20 for long header, 1 for shortest nsp */
                goto drop_it;

        skb_pull(skb, 20);
        skb_reset_transport_header(skb);

        /* Destination info */
        ptr += 2;
        cb->dst = dn_eth2dn(ptr);
        if (memcmp(ptr, dn_hiord_addr, 4) != 0)
                goto drop_it;
        ptr += 6;


        /* Source info */
        ptr += 2;
        cb->src = dn_eth2dn(ptr);
        if (memcmp(ptr, dn_hiord_addr, 4) != 0)
                goto drop_it;
        ptr += 6;
        /* Other junk */
        ptr++;
        cb->hops = *ptr++; /* Visit Count */

        return NF_HOOK(NFPROTO_DECNET, NF_DN_PRE_ROUTING, skb, skb->dev, NULL,
                       dn_route_rx_packet);

drop_it:
        kfree_skb(skb);
        return NET_RX_DROP;
}



static int dn_route_rx_short(struct sk_buff *skb)
{
        struct dn_skb_cb *cb = DN_SKB_CB(skb);
        unsigned char *ptr = skb->data;

        if (!pskb_may_pull(skb, 6)) /* 5 for short header + 1 for shortest nsp */
                goto drop_it;

        skb_pull(skb, 5);
        skb_reset_transport_header(skb);

        cb->dst = *(__le16 *)ptr;
        ptr += 2;
        cb->src = *(__le16 *)ptr;
        ptr += 2;
        cb->hops = *ptr & 0x3f;

        return NF_HOOK(NFPROTO_DECNET, NF_DN_PRE_ROUTING, skb, skb->dev, NULL,
                       dn_route_rx_packet);

drop_it:
        kfree_skb(skb);
        return NET_RX_DROP;
}

static int dn_route_discard(struct sk_buff *skb)
{
        /*
         * I know we drop the packet here, but thats considered success in
         * this case
         */
        kfree_skb(skb);
        return NET_RX_SUCCESS;
}

static int dn_route_ptp_hello(struct sk_buff *skb)
{
        dn_dev_hello(skb);
        dn_neigh_pointopoint_hello(skb);
        return NET_RX_SUCCESS;
}

int dn_route_rcv(struct sk_buff *skb, struct net_device *dev, struct packet_type *pt, struct net_device *orig_dev)
{
        struct dn_skb_cb *cb;
        unsigned char flags = 0;
        __u16 len = le16_to_cpu(*(__le16 *)skb->data);
        struct dn_dev *dn = rcu_dereference(dev->dn_ptr);
        unsigned char padlen = 0;

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

        if (dn == NULL)
                goto dump_it;

        if ((skb = skb_share_check(skb, GFP_ATOMIC)) == NULL)
                goto out;

        if (!pskb_may_pull(skb, 3))
                goto dump_it;

        skb_pull(skb, 2);

        if (len > skb->len)
                goto dump_it;

        skb_trim(skb, len);

        flags = *skb->data;

        cb = DN_SKB_CB(skb);
        cb->stamp = jiffies;
        cb->iif = dev->ifindex;

        /*
         * If we have padding, remove it.
         */
        if (flags & DN_RT_F_PF) {
                padlen = flags & ~DN_RT_F_PF;
                if (!pskb_may_pull(skb, padlen + 1))
                        goto dump_it;
                skb_pull(skb, padlen);
                flags = *skb->data;
        }

        skb_reset_network_header(skb);

        /*
         * Weed out future version DECnet
         */
        if (flags & DN_RT_F_VER)
                goto dump_it;

        cb->rt_flags = flags;

        if (decnet_debug_level & 1)
                printk(KERN_DEBUG
                        "dn_route_rcv: got 0x%02x from %s [%d %d %d]\n",
                        (int)flags, (dev) ? dev->name : "???", len, skb->len,
                        padlen);

        if (flags & DN_RT_PKT_CNTL) {
                if (unlikely(skb_linearize(skb)))
                        goto dump_it;

                switch(flags & DN_RT_CNTL_MSK) {
                        case DN_RT_PKT_INIT:
                                dn_dev_init_pkt(skb);
                                break;
                        case DN_RT_PKT_VERI:
                                dn_dev_veri_pkt(skb);
                                break;
                }

                if (dn->parms.state != DN_DEV_S_RU)
                        goto dump_it;

                switch(flags & DN_RT_CNTL_MSK) {
                        case DN_RT_PKT_HELO:
                                return NF_HOOK(NFPROTO_DECNET, NF_DN_HELLO,
                                               skb, skb->dev, NULL,
                                               dn_route_ptp_hello);

                        case DN_RT_PKT_L1RT:
                        case DN_RT_PKT_L2RT:
                                return NF_HOOK(NFPROTO_DECNET, NF_DN_ROUTE,
                                               skb, skb->dev, NULL,
                                               dn_route_discard);
                        case DN_RT_PKT_ERTH:
                                return NF_HOOK(NFPROTO_DECNET, NF_DN_HELLO,
                                               skb, skb->dev, NULL,
                                               dn_neigh_router_hello);

                        case DN_RT_PKT_EEDH:
                                return NF_HOOK(NFPROTO_DECNET, NF_DN_HELLO,
                                               skb, skb->dev, NULL,
                                               dn_neigh_endnode_hello);
                }
        } else {
                if (dn->parms.state != DN_DEV_S_RU)
                        goto dump_it;

                skb_pull(skb, 1); /* Pull flags */

                switch(flags & DN_RT_PKT_MSK) {
                        case DN_RT_PKT_LONG:
                                return dn_route_rx_long(skb);
                        case DN_RT_PKT_SHORT:
                                return dn_route_rx_short(skb);
                }
        }

dump_it:
        kfree_skb(skb);
out:
        return NET_RX_DROP;
}

static int dn_output(struct sk_buff *skb)
{
        struct dst_entry *dst = skb_dst(skb);
        struct dn_route *rt = (struct dn_route *)dst;
        struct net_device *dev = dst->dev;
        struct dn_skb_cb *cb = DN_SKB_CB(skb);
        struct neighbour *neigh;

        int err = -EINVAL;

        if ((neigh = dst->neighbour) == NULL)
                goto error;

        skb->dev = dev;

        cb->src = rt->rt_saddr;
        cb->dst = rt->rt_daddr;

        /*
         * Always set the Intra-Ethernet bit on all outgoing packets
         * originated on this node. Only valid flag from upper layers
         * is return-to-sender-requested. Set hop count to 0 too.
         */
        cb->rt_flags &= ~DN_RT_F_RQR;
        cb->rt_flags |= DN_RT_F_IE;
        cb->hops = 0;

        return NF_HOOK(NFPROTO_DECNET, NF_DN_LOCAL_OUT, skb, NULL, dev,
                       neigh->output);

error:
        if (net_ratelimit())
                printk(KERN_DEBUG "dn_output: This should not happen\n");

        kfree_skb(skb);

        return err;
}

static int dn_forward(struct sk_buff *skb)
{
        struct dn_skb_cb *cb = DN_SKB_CB(skb);
        struct dst_entry *dst = skb_dst(skb);
        struct dn_dev *dn_db = rcu_dereference(dst->dev->dn_ptr);
        struct dn_route *rt;
        struct neighbour *neigh = dst->neighbour;
        int header_len;
#ifdef CONFIG_NETFILTER
        struct net_device *dev = skb->dev;
#endif

        if (skb->pkt_type != PACKET_HOST)
                goto drop;

        /* Ensure that we have enough space for headers */
        rt = (struct dn_route *)skb_dst(skb);
        header_len = dn_db->use_long ? 21 : 6;
        if (skb_cow(skb, LL_RESERVED_SPACE(rt->dst.dev)+header_len))
                goto drop;

        /*
         * Hop count exceeded.
         */
        if (++cb->hops > 30)
                goto drop;

        skb->dev = rt->dst.dev;

        /*
         * If packet goes out same interface it came in on, then set
         * the Intra-Ethernet bit. This has no effect for short
         * packets, so we don't need to test for them here.
         */
        cb->rt_flags &= ~DN_RT_F_IE;
        if (rt->rt_flags & RTCF_DOREDIRECT)
                cb->rt_flags |= DN_RT_F_IE;

        return NF_HOOK(NFPROTO_DECNET, NF_DN_FORWARD, skb, dev, skb->dev,
                       neigh->output);

drop:
        kfree_skb(skb);
        return NET_RX_DROP;
}

/*
 * Used to catch bugs. This should never normally get
 * called.
 */
static int dn_rt_bug(struct sk_buff *skb)
{
        if (net_ratelimit()) {
                struct dn_skb_cb *cb = DN_SKB_CB(skb);

                printk(KERN_DEBUG "dn_rt_bug: skb from:%04x to:%04x\n",
                                le16_to_cpu(cb->src), le16_to_cpu(cb->dst));
        }

        kfree_skb(skb);

        return NET_RX_DROP;
}

static unsigned int dn_dst_default_advmss(const struct dst_entry *dst)
{
        return dn_mss_from_pmtu(dst->dev, dst_mtu(dst));
}

static unsigned int dn_dst_default_mtu(const struct dst_entry *dst)
{
        return dst->dev->mtu;
}

static int dn_rt_set_next_hop(struct dn_route *rt, struct dn_fib_res *res)
{
        struct dn_fib_info *fi = res->fi;
        struct net_device *dev = rt->dst.dev;
        struct neighbour *n;
        unsigned int metric;

        if (fi) {
                if (DN_FIB_RES_GW(*res) &&
                    DN_FIB_RES_NH(*res).nh_scope == RT_SCOPE_LINK)
                        rt->rt_gateway = DN_FIB_RES_GW(*res);
                dst_import_metrics(&rt->dst, fi->fib_metrics);
        }
        rt->rt_type = res->type;

        if (dev != NULL && rt->dst.neighbour == NULL) {
                n = __neigh_lookup_errno(&dn_neigh_table, &rt->rt_gateway, dev);
                if (IS_ERR(n))
                        return PTR_ERR(n);
                rt->dst.neighbour = n;
        }

        if (dst_metric(&rt->dst, RTAX_MTU) > rt->dst.dev->mtu)
                dst_metric_set(&rt->dst, RTAX_MTU, rt->dst.dev->mtu);
        metric = dst_metric_raw(&rt->dst, RTAX_ADVMSS);
        if (metric) {
                unsigned int mss = dn_mss_from_pmtu(dev, dst_mtu(&rt->dst));
                if (metric > mss)
                        dst_metric_set(&rt->dst, RTAX_ADVMSS, mss);
        }
        return 0;
}

static inline int dn_match_addr(__le16 addr1, __le16 addr2)
{
        __u16 tmp = le16_to_cpu(addr1) ^ le16_to_cpu(addr2);
        int match = 16;
        while(tmp) {
                tmp >>= 1;
                match--;
        }
        return match;
}

static __le16 dnet_select_source(const struct net_device *dev, __le16 daddr, int scope)
{
        __le16 saddr = 0;
        struct dn_dev *dn_db;
        struct dn_ifaddr *ifa;
        int best_match = 0;
        int ret;

        rcu_read_lock();
        dn_db = rcu_dereference(dev->dn_ptr);
        for (ifa = rcu_dereference(dn_db->ifa_list);
             ifa != NULL;
             ifa = rcu_dereference(ifa->ifa_next)) {
                if (ifa->ifa_scope > scope)
                        continue;
                if (!daddr) {
                        saddr = ifa->ifa_local;
                        break;
                }
                ret = dn_match_addr(daddr, ifa->ifa_local);
                if (ret > best_match)
                        saddr = ifa->ifa_local;
                if (best_match == 0)
                        saddr = ifa->ifa_local;
        }
        rcu_read_unlock();

        return saddr;
}

static inline __le16 __dn_fib_res_prefsrc(struct dn_fib_res *res)
{
        return dnet_select_source(DN_FIB_RES_DEV(*res), DN_FIB_RES_GW(*res), res->scope);
}

static inline __le16 dn_fib_rules_map_destination(__le16 daddr, struct dn_fib_res *res)
{
        __le16 mask = dnet_make_mask(res->prefixlen);
        return (daddr&~mask)|res->fi->fib_nh->nh_gw;
}

static int dn_route_output_slow(struct dst_entry **pprt, const struct flowi *oldflp, int try_hard)
{
        struct flowi fl = { .fld_dst = oldflp->fld_dst,
                            .fld_src = oldflp->fld_src,
                            .fld_scope = RT_SCOPE_UNIVERSE,
                            .mark = oldflp->mark,
                            .iif = init_net.loopback_dev->ifindex,
                            .oif = oldflp->oif };
        struct dn_route *rt = NULL;
        struct net_device *dev_out = NULL, *dev;
        struct neighbour *neigh = NULL;
        unsigned hash;
        unsigned flags = 0;
        struct dn_fib_res res = { .fi = NULL, .type = RTN_UNICAST };
        int err;
        int free_res = 0;
        __le16 gateway = 0;

        if (decnet_debug_level & 16)
                printk(KERN_DEBUG
                       "dn_route_output_slow: dst=%04x src=%04x mark=%d"
                       " iif=%d oif=%d\n", le16_to_cpu(oldflp->fld_dst),
                       le16_to_cpu(oldflp->fld_src),
                       oldflp->mark, init_net.loopback_dev->ifindex, oldflp->oif);

        /* If we have an output interface, verify its a DECnet device */
        if (oldflp->oif) {
                dev_out = dev_get_by_index(&init_net, oldflp->oif);
                err = -ENODEV;
                if (dev_out && dev_out->dn_ptr == NULL) {
                        dev_put(dev_out);
                        dev_out = NULL;
                }
                if (dev_out == NULL)
                        goto out;
        }

        /* If we have a source address, verify that its a local address */
        if (oldflp->fld_src) {
                err = -EADDRNOTAVAIL;

                if (dev_out) {
                        if (dn_dev_islocal(dev_out, oldflp->fld_src))
                                goto source_ok;
                        dev_put(dev_out);
                        goto out;
                }
                rcu_read_lock();
                for_each_netdev_rcu(&init_net, dev) {
                        if (!dev->dn_ptr)
                                continue;
                        if (!dn_dev_islocal(dev, oldflp->fld_src))
                                continue;
                        if ((dev->flags & IFF_LOOPBACK) &&
                            oldflp->fld_dst &&
                            !dn_dev_islocal(dev, oldflp->fld_dst))
                                continue;

                        dev_out = dev;
                        break;
                }
                rcu_read_unlock();
                if (dev_out == NULL)
                        goto out;
                dev_hold(dev_out);
source_ok:
                ;
        }

        /* No destination? Assume its local */
        if (!fl.fld_dst) {
                fl.fld_dst = fl.fld_src;

                err = -EADDRNOTAVAIL;
                if (dev_out)
                        dev_put(dev_out);
                dev_out = init_net.loopback_dev;
                dev_hold(dev_out);
                if (!fl.fld_dst) {
                        fl.fld_dst =
                        fl.fld_src = dnet_select_source(dev_out, 0,
                                                       RT_SCOPE_HOST);
                        if (!fl.fld_dst)
                                goto out;
                }
                fl.oif = init_net.loopback_dev->ifindex;
                res.type = RTN_LOCAL;
                goto make_route;
        }

        if (decnet_debug_level & 16)
                printk(KERN_DEBUG
                       "dn_route_output_slow: initial checks complete."
                       " dst=%o4x src=%04x oif=%d try_hard=%d\n",
                       le16_to_cpu(fl.fld_dst), le16_to_cpu(fl.fld_src),
                       fl.oif, try_hard);

        /*
         * N.B. If the kernel is compiled without router support then
         * dn_fib_lookup() will evaluate to non-zero so this if () block
         * will always be executed.
         */
        err = -ESRCH;

        if (try_hard || (err = dn_fib_lookup(&fl, &res)) != 0) {
                struct dn_dev *dn_db;
                if (err != -ESRCH)
                        goto out;
                /*
                 * Here the fallback is basically the standard algorithm for
                 * routing in endnodes which is described in the DECnet routing
                 * docs
                 *
                 * If we are not trying hard, look in neighbour cache.
                 * The result is tested to ensure that if a specific output
                 * device/source address was requested, then we honour that
                 * here
                 */
                if (!try_hard) {
                        neigh = neigh_lookup_nodev(&dn_neigh_table, &init_net, &fl.fld_dst);
                        if (neigh) {
                                if ((oldflp->oif &&
                                    (neigh->dev->ifindex != oldflp->oif)) ||
                                    (oldflp->fld_src &&
                                    (!dn_dev_islocal(neigh->dev,
                                                      oldflp->fld_src)))) {
                                        neigh_release(neigh);
                                        neigh = NULL;
                                } else {
                                        if (dev_out)
                                                dev_put(dev_out);
                                        if (dn_dev_islocal(neigh->dev, fl.fld_dst)) {
                                                dev_out = init_net.loopback_dev;
                                                res.type = RTN_LOCAL;
                                        } else {
                                                dev_out = neigh->dev;
                                        }
                                        dev_hold(dev_out);
                                        goto select_source;
                                }
                        }
                }

                /* Not there? Perhaps its a local address */
                if (dev_out == NULL)
                        dev_out = dn_dev_get_default();
                err = -ENODEV;
                if (dev_out == NULL)
                        goto out;
                dn_db = rcu_dereference_raw(dev_out->dn_ptr);
                /* Possible improvement - check all devices for local addr */
                if (dn_dev_islocal(dev_out, fl.fld_dst)) {
                        dev_put(dev_out);
                        dev_out = init_net.loopback_dev;
                        dev_hold(dev_out);
                        res.type = RTN_LOCAL;
                        goto select_source;
                }
                /* Not local either.... try sending it to the default router */
                neigh = neigh_clone(dn_db->router);
                BUG_ON(neigh && neigh->dev != dev_out);

                /* Ok then, we assume its directly connected and move on */
select_source:
                if (neigh)
                        gateway = ((struct dn_neigh *)neigh)->addr;
                if (gateway == 0)
                        gateway = fl.fld_dst;
                if (fl.fld_src == 0) {
                        fl.fld_src = dnet_select_source(dev_out, gateway,
                                                         res.type == RTN_LOCAL ?
                                                         RT_SCOPE_HOST :
                                                         RT_SCOPE_LINK);
                        if (fl.fld_src == 0 && res.type != RTN_LOCAL)
                                goto e_addr;
                }
                fl.oif = dev_out->ifindex;
                goto make_route;
        }
        free_res = 1;

        if (res.type == RTN_NAT)
                goto e_inval;

        if (res.type == RTN_LOCAL) {
                if (!fl.fld_src)
                        fl.fld_src = fl.fld_dst;
                if (dev_out)
                        dev_put(dev_out);
                dev_out = init_net.loopback_dev;
                dev_hold(dev_out);
                fl.oif = dev_out->ifindex;
                if (res.fi)
                        dn_fib_info_put(res.fi);
                res.fi = NULL;
                goto make_route;
        }

        if (res.fi->fib_nhs > 1 && fl.oif == 0)
                dn_fib_select_multipath(&fl, &res);

        /*
         * We could add some logic to deal with default routes here and
         * get rid of some of the special casing above.
         */

        if (!fl.fld_src)
                fl.fld_src = DN_FIB_RES_PREFSRC(res);

        if (dev_out)
                dev_put(dev_out);
        dev_out = DN_FIB_RES_DEV(res);
        dev_hold(dev_out);
        fl.oif = dev_out->ifindex;
        gateway = DN_FIB_RES_GW(res);

make_route:
        if (dev_out->flags & IFF_LOOPBACK)
                flags |= RTCF_LOCAL;

        rt = dst_alloc(&dn_dst_ops);
        if (rt == NULL)
                goto e_nobufs;

        atomic_set(&rt->dst.__refcnt, 1);
        rt->dst.flags   = DST_HOST;

        rt->fl.fld_src    = oldflp->fld_src;
        rt->fl.fld_dst    = oldflp->fld_dst;
        rt->fl.oif        = oldflp->oif;
        rt->fl.iif        = 0;
        rt->fl.mark       = oldflp->mark;

        rt->rt_saddr      = fl.fld_src;
        rt->rt_daddr      = fl.fld_dst;
        rt->rt_gateway    = gateway ? gateway : fl.fld_dst;
        rt->rt_local_src  = fl.fld_src;

        rt->rt_dst_map    = fl.fld_dst;
        rt->rt_src_map    = fl.fld_src;

        rt->dst.dev = dev_out;
        dev_hold(dev_out);
        rt->dst.neighbour = neigh;
        neigh = NULL;

        rt->dst.lastuse = jiffies;
        rt->dst.output  = dn_output;
        rt->dst.input   = dn_rt_bug;
        rt->rt_flags      = flags;
        if (flags & RTCF_LOCAL)
                rt->dst.input = dn_nsp_rx;

        err = dn_rt_set_next_hop(rt, &res);
        if (err)
                goto e_neighbour;

        hash = dn_hash(rt->fl.fld_src, rt->fl.fld_dst);
        dn_insert_route(rt, hash, (struct dn_route **)pprt);

done:
        if (neigh)
                neigh_release(neigh);
        if (free_res)
                dn_fib_res_put(&res);
        if (dev_out)
                dev_put(dev_out);
out:
        return err;

e_addr:
        err = -EADDRNOTAVAIL;
        goto done;
e_inval:
        err = -EINVAL;
        goto done;
e_nobufs:
        err = -ENOBUFS;
        goto done;
e_neighbour:
        dst_free(&rt->dst);
        goto e_nobufs;
}


/*
 * N.B. The flags may be moved into the flowi at some future stage.
 */
static int __dn_route_output_key(struct dst_entry **pprt, const struct flowi *flp, int flags)
{
        unsigned hash = dn_hash(flp->fld_src, flp->fld_dst);
        struct dn_route *rt = NULL;

        if (!(flags & MSG_TRYHARD)) {
                rcu_read_lock_bh();
                for (rt = rcu_dereference_bh(dn_rt_hash_table[hash].chain); rt;
                        rt = rcu_dereference_bh(rt->dst.dn_next)) {
                        if ((flp->fld_dst == rt->fl.fld_dst) &&
                            (flp->fld_src == rt->fl.fld_src) &&
                            (flp->mark == rt->fl.mark) &&
                            dn_is_output_route(rt) &&
                            (rt->fl.oif == flp->oif)) {
                                dst_use(&rt->dst, jiffies);
                                rcu_read_unlock_bh();
                                *pprt = &rt->dst;
                                return 0;
                        }
                }
                rcu_read_unlock_bh();
        }

        return dn_route_output_slow(pprt, flp, flags);
}

static int dn_route_output_key(struct dst_entry **pprt, struct flowi *flp, int flags)
{
        int err;

        err = __dn_route_output_key(pprt, flp, flags);
        if (err == 0 && flp->proto) {
                err = xfrm_lookup(&init_net, pprt, flp, NULL, 0);
        }
        return err;
}

int dn_route_output_sock(struct dst_entry **pprt, struct flowi *fl, struct sock *sk, int flags)
{
        int err;

        err = __dn_route_output_key(pprt, fl, flags & MSG_TRYHARD);
        if (err == 0 && fl->proto) {
                err = xfrm_lookup(&init_net, pprt, fl, sk,
                                 (flags & MSG_DONTWAIT) ? 0 : XFRM_LOOKUP_WAIT);
        }
        return err;
}

static int dn_route_input_slow(struct sk_buff *skb)
{
        struct dn_route *rt = NULL;
        struct dn_skb_cb *cb = DN_SKB_CB(skb);
        struct net_device *in_dev = skb->dev;
        struct net_device *out_dev = NULL;
        struct dn_dev *dn_db;
        struct neighbour *neigh = NULL;
        unsigned hash;
        int flags = 0;
        __le16 gateway = 0;
        __le16 local_src = 0;
        struct flowi fl = { .fld_dst = cb->dst,
                            .fld_src = cb->src,
                            .fld_scope = RT_SCOPE_UNIVERSE,
                            .mark = skb->mark,
                            .iif = skb->dev->ifindex };
        struct dn_fib_res res = { .fi = NULL, .type = RTN_UNREACHABLE };
        int err = -EINVAL;
        int free_res = 0;

        dev_hold(in_dev);

        if ((dn_db = rcu_dereference(in_dev->dn_ptr)) == NULL)
                goto out;

        /* Zero source addresses are not allowed */
        if (fl.fld_src == 0)
                goto out;

        /*
         * In this case we've just received a packet from a source
         * outside ourselves pretending to come from us. We don't
         * allow it any further to prevent routing loops, spoofing and
         * other nasties. Loopback packets already have the dst attached
         * so this only affects packets which have originated elsewhere.
         */
        err  = -ENOTUNIQ;
        if (dn_dev_islocal(in_dev, cb->src))
                goto out;

        err = dn_fib_lookup(&fl, &res);
        if (err) {
                if (err != -ESRCH)
                        goto out;
                /*
                 * Is the destination us ?
                 */
                if (!dn_dev_islocal(in_dev, cb->dst))
                        goto e_inval;

                res.type = RTN_LOCAL;
        } else {
                __le16 src_map = fl.fld_src;
                free_res = 1;

                out_dev = DN_FIB_RES_DEV(res);
                if (out_dev == NULL) {
                        if (net_ratelimit())
                                printk(KERN_CRIT "Bug in dn_route_input_slow() "
                                                 "No output device\n");
                        goto e_inval;
                }
                dev_hold(out_dev);

                if (res.r)
                        src_map = fl.fld_src; /* no NAT support for now */

                gateway = DN_FIB_RES_GW(res);
                if (res.type == RTN_NAT) {
                        fl.fld_dst = dn_fib_rules_map_destination(fl.fld_dst, &res);
                        dn_fib_res_put(&res);
                        free_res = 0;
                        if (dn_fib_lookup(&fl, &res))
                                goto e_inval;
                        free_res = 1;
                        if (res.type != RTN_UNICAST)
                                goto e_inval;
                        flags |= RTCF_DNAT;
                        gateway = fl.fld_dst;
                }
                fl.fld_src = src_map;
        }

        switch(res.type) {
        case RTN_UNICAST:
                /*
                 * Forwarding check here, we only check for forwarding
                 * being turned off, if you want to only forward intra
                 * area, its up to you to set the routing tables up
                 * correctly.
                 */
                if (dn_db->parms.forwarding == 0)
                        goto e_inval;

                if (res.fi->fib_nhs > 1 && fl.oif == 0)
                        dn_fib_select_multipath(&fl, &res);

                /*
                 * Check for out_dev == in_dev. We use the RTCF_DOREDIRECT
                 * flag as a hint to set the intra-ethernet bit when
                 * forwarding. If we've got NAT in operation, we don't do
                 * this optimisation.
                 */
                if (out_dev == in_dev && !(flags & RTCF_NAT))
                        flags |= RTCF_DOREDIRECT;

                local_src = DN_FIB_RES_PREFSRC(res);

        case RTN_BLACKHOLE:
        case RTN_UNREACHABLE:
                break;
        case RTN_LOCAL:
                flags |= RTCF_LOCAL;
                fl.fld_src = cb->dst;
                fl.fld_dst = cb->src;

                /* Routing tables gave us a gateway */
                if (gateway)
                        goto make_route;

                /* Packet was intra-ethernet, so we know its on-link */
                if (cb->rt_flags & DN_RT_F_IE) {
                        gateway = cb->src;
                        flags |= RTCF_DIRECTSRC;
                        goto make_route;
                }

                /* Use the default router if there is one */
                neigh = neigh_clone(dn_db->router);
                if (neigh) {
                        gateway = ((struct dn_neigh *)neigh)->addr;
                        goto make_route;
                }

                /* Close eyes and pray */
                gateway = cb->src;
                flags |= RTCF_DIRECTSRC;
                goto make_route;
        default:
                goto e_inval;
        }

make_route:
        rt = dst_alloc(&dn_dst_ops);
        if (rt == NULL)
                goto e_nobufs;

        rt->rt_saddr      = fl.fld_src;
        rt->rt_daddr      = fl.fld_dst;
        rt->rt_gateway    = fl.fld_dst;
        if (gateway)
                rt->rt_gateway = gateway;
        rt->rt_local_src  = local_src ? local_src : rt->rt_saddr;

        rt->rt_dst_map    = fl.fld_dst;
        rt->rt_src_map    = fl.fld_src;

        rt->fl.fld_src    = cb->src;
        rt->fl.fld_dst    = cb->dst;
        rt->fl.oif        = 0;
        rt->fl.iif        = in_dev->ifindex;
        rt->fl.mark       = fl.mark;

        rt->dst.flags = DST_HOST;
        rt->dst.neighbour = neigh;
        rt->dst.dev = out_dev;
        rt->dst.lastuse = jiffies;
        rt->dst.output = dn_rt_bug;
        switch(res.type) {
                case RTN_UNICAST:
                        rt->dst.input = dn_forward;
                        break;
                case RTN_LOCAL:
                        rt->dst.output = dn_output;
                        rt->dst.input = dn_nsp_rx;
                        rt->dst.dev = in_dev;
                        flags |= RTCF_LOCAL;
                        break;
                default:
                case RTN_UNREACHABLE:
                case RTN_BLACKHOLE:
                        rt->dst.input = dst_discard;
        }
        rt->rt_flags = flags;
        if (rt->dst.dev)
                dev_hold(rt->dst.dev);

        err = dn_rt_set_next_hop(rt, &res);
        if (err)
                goto e_neighbour;

        hash = dn_hash(rt->fl.fld_src, rt->fl.fld_dst);
        dn_insert_route(rt, hash, &rt);
        skb_dst_set(skb, &rt->dst);

done:
        if (neigh)
                neigh_release(neigh);
        if (free_res)
                dn_fib_res_put(&res);
        dev_put(in_dev);
        if (out_dev)
                dev_put(out_dev);
out:
        return err;

e_inval:
        err = -EINVAL;
        goto done;

e_nobufs:
        err = -ENOBUFS;
        goto done;

e_neighbour:
        dst_free(&rt->dst);
        goto done;
}

static int dn_route_input(struct sk_buff *skb)
{
        struct dn_route *rt;
        struct dn_skb_cb *cb = DN_SKB_CB(skb);
        unsigned hash = dn_hash(cb->src, cb->dst);

        if (skb_dst(skb))
                return 0;

        rcu_read_lock();
        for(rt = rcu_dereference(dn_rt_hash_table[hash].chain); rt != NULL;
            rt = rcu_dereference(rt->dst.dn_next)) {
                if ((rt->fl.fld_src == cb->src) &&
                    (rt->fl.fld_dst == cb->dst) &&
                    (rt->fl.oif == 0) &&
                    (rt->fl.mark == skb->mark) &&
                    (rt->fl.iif == cb->iif)) {
                        dst_use(&rt->dst, jiffies);
                        rcu_read_unlock();
                        skb_dst_set(skb, (struct dst_entry *)rt);
                        return 0;
                }
        }
        rcu_read_unlock();

        return dn_route_input_slow(skb);
}

static int dn_rt_fill_info(struct sk_buff *skb, u32 pid, u32 seq,
                           int event, int nowait, unsigned int flags)
{
        struct dn_route *rt = (struct dn_route *)skb_dst(skb);
        struct rtmsg *r;
        struct nlmsghdr *nlh;
        unsigned char *b = skb_tail_pointer(skb);
        long expires;

        nlh = NLMSG_NEW(skb, pid, seq, event, sizeof(*r), flags);
        r = NLMSG_DATA(nlh);
        r->rtm_family = AF_DECnet;
        r->rtm_dst_len = 16;
        r->rtm_src_len = 0;
        r->rtm_tos = 0;
        r->rtm_table = RT_TABLE_MAIN;
        RTA_PUT_U32(skb, RTA_TABLE, RT_TABLE_MAIN);
        r->rtm_type = rt->rt_type;
        r->rtm_flags = (rt->rt_flags & ~0xFFFF) | RTM_F_CLONED;
        r->rtm_scope = RT_SCOPE_UNIVERSE;
        r->rtm_protocol = RTPROT_UNSPEC;
        if (rt->rt_flags & RTCF_NOTIFY)
                r->rtm_flags |= RTM_F_NOTIFY;
        RTA_PUT(skb, RTA_DST, 2, &rt->rt_daddr);
        if (rt->fl.fld_src) {
                r->rtm_src_len = 16;
                RTA_PUT(skb, RTA_SRC, 2, &rt->fl.fld_src);
        }
        if (rt->dst.dev)
                RTA_PUT(skb, RTA_OIF, sizeof(int), &rt->dst.dev->ifindex);
        /*
         * Note to self - change this if input routes reverse direction when
         * they deal only with inputs and not with replies like they do
         * currently.
         */
        RTA_PUT(skb, RTA_PREFSRC, 2, &rt->rt_local_src);
        if (rt->rt_daddr != rt->rt_gateway)
                RTA_PUT(skb, RTA_GATEWAY, 2, &rt->rt_gateway);
        if (rtnetlink_put_metrics(skb, dst_metrics_ptr(&rt->dst)) < 0)
                goto rtattr_failure;
        expires = rt->dst.expires ? rt->dst.expires - jiffies : 0;
        if (rtnl_put_cacheinfo(skb, &rt->dst, 0, 0, 0, expires,
                               rt->dst.error) < 0)
                goto rtattr_failure;
        if (dn_is_input_route(rt))
                RTA_PUT(skb, RTA_IIF, sizeof(int), &rt->fl.iif);

        nlh->nlmsg_len = skb_tail_pointer(skb) - b;
        return skb->len;

nlmsg_failure:
rtattr_failure:
        nlmsg_trim(skb, b);
        return -1;
}

/*
 * This is called by both endnodes and routers now.
 */
static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh, void *arg)
{
        struct net *net = sock_net(in_skb->sk);
        struct rtattr **rta = arg;
        struct rtmsg *rtm = NLMSG_DATA(nlh);
        struct dn_route *rt = NULL;
        struct dn_skb_cb *cb;
        int err;
        struct sk_buff *skb;
        struct flowi fl;

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

        memset(&fl, 0, sizeof(fl));
        fl.proto = DNPROTO_NSP;

        skb = alloc_skb(NLMSG_GOODSIZE, GFP_KERNEL);
        if (skb == NULL)
                return -ENOBUFS;
        skb_reset_mac_header(skb);
        cb = DN_SKB_CB(skb);

        if (rta[RTA_SRC-1])
                memcpy(&fl.fld_src, RTA_DATA(rta[RTA_SRC-1]), 2);
        if (rta[RTA_DST-1])
                memcpy(&fl.fld_dst, RTA_DATA(rta[RTA_DST-1]), 2);
        if (rta[RTA_IIF-1])
                memcpy(&fl.iif, RTA_DATA(rta[RTA_IIF-1]), sizeof(int));

        if (fl.iif) {
                struct net_device *dev;
                if ((dev = dev_get_by_index(&init_net, fl.iif)) == NULL) {
                        kfree_skb(skb);
                        return -ENODEV;
                }
                if (!dev->dn_ptr) {
                        dev_put(dev);
                        kfree_skb(skb);
                        return -ENODEV;
                }
                skb->protocol = htons(ETH_P_DNA_RT);
                skb->dev = dev;
                cb->src = fl.fld_src;
                cb->dst = fl.fld_dst;
                local_bh_disable();
                err = dn_route_input(skb);
                local_bh_enable();
                memset(cb, 0, sizeof(struct dn_skb_cb));
                rt = (struct dn_route *)skb_dst(skb);
                if (!err && -rt->dst.error)
                        err = rt->dst.error;
        } else {
                int oif = 0;
                if (rta[RTA_OIF - 1])
                        memcpy(&oif, RTA_DATA(rta[RTA_OIF - 1]), sizeof(int));
                fl.oif = oif;
                err = dn_route_output_key((struct dst_entry **)&rt, &fl, 0);
        }

        if (skb->dev)
                dev_put(skb->dev);
        skb->dev = NULL;
        if (err)
                goto out_free;
        skb_dst_set(skb, &rt->dst);
        if (rtm->rtm_flags & RTM_F_NOTIFY)
                rt->rt_flags |= RTCF_NOTIFY;

        err = dn_rt_fill_info(skb, NETLINK_CB(in_skb).pid, nlh->nlmsg_seq, RTM_NEWROUTE, 0, 0);

        if (err == 0)
                goto out_free;
        if (err < 0) {
                err = -EMSGSIZE;
                goto out_free;
        }

        return rtnl_unicast(skb, &init_net, NETLINK_CB(in_skb).pid);

out_free:
        kfree_skb(skb);
        return err;
}

/*
 * For routers, this is called from dn_fib_dump, but for endnodes its
 * called directly from the rtnetlink dispatch table.
 */
int dn_cache_dump(struct sk_buff *skb, struct netlink_callback *cb)
{
        struct net *net = sock_net(skb->sk);
        struct dn_route *rt;
        int h, s_h;
        int idx, s_idx;

        if (!net_eq(net, &init_net))
                return 0;

        if (NLMSG_PAYLOAD(cb->nlh, 0) < sizeof(struct rtmsg))
                return -EINVAL;
        if (!(((struct rtmsg *)NLMSG_DATA(cb->nlh))->rtm_flags&RTM_F_CLONED))
                return 0;

        s_h = cb->args[0];
        s_idx = idx = cb->args[1];
        for(h = 0; h <= dn_rt_hash_mask; h++) {
                if (h < s_h)
                        continue;
                if (h > s_h)
                        s_idx = 0;
                rcu_read_lock_bh();
                for(rt = rcu_dereference_bh(dn_rt_hash_table[h].chain), idx = 0;
                        rt;
                        rt = rcu_dereference_bh(rt->dst.dn_next), idx++) {
                        if (idx < s_idx)
                                continue;
                        skb_dst_set(skb, dst_clone(&rt->dst));
                        if (dn_rt_fill_info(skb, NETLINK_CB(cb->skb).pid,
                                        cb->nlh->nlmsg_seq, RTM_NEWROUTE,
                                        1, NLM_F_MULTI) <= 0) {
                                skb_dst_drop(skb);
                                rcu_read_unlock_bh();
                                goto done;
                        }
                        skb_dst_drop(skb);
                }
                rcu_read_unlock_bh();
        }

done:
        cb->args[0] = h;
        cb->args[1] = idx;
        return skb->len;
}

#ifdef CONFIG_PROC_FS
struct dn_rt_cache_iter_state {
        int bucket;
};

static struct dn_route *dn_rt_cache_get_first(struct seq_file *seq)
{
        struct dn_route *rt = NULL;
        struct dn_rt_cache_iter_state *s = seq->private;

        for(s->bucket = dn_rt_hash_mask; s->bucket >= 0; --s->bucket) {
                rcu_read_lock_bh();
                rt = rcu_dereference_bh(dn_rt_hash_table[s->bucket].chain);
                if (rt)
                        break;
                rcu_read_unlock_bh();
        }
        return rt;
}

static struct dn_route *dn_rt_cache_get_next(struct seq_file *seq, struct dn_route *rt)
{
        struct dn_rt_cache_iter_state *s = seq->private;

        rt = rcu_dereference_bh(rt->dst.dn_next);
        while (!rt) {
                rcu_read_unlock_bh();
                if (--s->bucket < 0)
                        break;
                rcu_read_lock_bh();
                rt = rcu_dereference_bh(dn_rt_hash_table[s->bucket].chain);
        }
        return rt;
}

static void *dn_rt_cache_seq_start(struct seq_file *seq, loff_t *pos)
{
        struct dn_route *rt = dn_rt_cache_get_first(seq);

        if (rt) {
                while(*pos && (rt = dn_rt_cache_get_next(seq, rt)))
                        --*pos;
        }
        return *pos ? NULL : rt;
}

static void *dn_rt_cache_seq_next(struct seq_file *seq, void *v, loff_t *pos)
{
        struct dn_route *rt = dn_rt_cache_get_next(seq, v);
        ++*pos;
        return rt;
}

static void dn_rt_cache_seq_stop(struct seq_file *seq, void *v)
{
        if (v)
                rcu_read_unlock_bh();
}

static int dn_rt_cache_seq_show(struct seq_file *seq, void *v)
{
        struct dn_route *rt = v;
        char buf1[DN_ASCBUF_LEN], buf2[DN_ASCBUF_LEN];

        seq_printf(seq, "%-8s %-7s %-7s %04d %04d %04d\n",
                        rt->dst.dev ? rt->dst.dev->name : "*",
                        dn_addr2asc(le16_to_cpu(rt->rt_daddr), buf1),
                        dn_addr2asc(le16_to_cpu(rt->rt_saddr), buf2),
                        atomic_read(&rt->dst.__refcnt),
                        rt->dst.__use,
                        (int) dst_metric(&rt->dst, RTAX_RTT));
        return 0;
}

static const struct seq_operations dn_rt_cache_seq_ops = {
        .start  = dn_rt_cache_seq_start,
        .next   = dn_rt_cache_seq_next,
        .stop   = dn_rt_cache_seq_stop,
        .show   = dn_rt_cache_seq_show,
};

static int dn_rt_cache_seq_open(struct inode *inode, struct file *file)
{
        return seq_open_private(file, &dn_rt_cache_seq_ops,
                        sizeof(struct dn_rt_cache_iter_state));
}

static const struct file_operations dn_rt_cache_seq_fops = {
        .owner   = THIS_MODULE,
        .open    = dn_rt_cache_seq_open,
        .read    = seq_read,
        .llseek  = seq_lseek,
        .release = seq_release_private,
};

#endif /* CONFIG_PROC_FS */

void __init dn_route_init(void)
{
        int i, goal, order;

        dn_dst_ops.kmem_cachep =
                kmem_cache_create("dn_dst_cache", sizeof(struct dn_route), 0,
                                  SLAB_HWCACHE_ALIGN|SLAB_PANIC, NULL);
        dst_entries_init(&dn_dst_ops);
        setup_timer(&dn_route_timer, dn_dst_check_expire, 0);
        dn_route_timer.expires = jiffies + decnet_dst_gc_interval * HZ;
        add_timer(&dn_route_timer);

        goal = totalram_pages >> (26 - PAGE_SHIFT);

        for(order = 0; (1UL << order) < goal; order++)
                /* NOTHING */;

        /*
         * Only want 1024 entries max, since the table is very, very unlikely
         * to be larger than that.
         */
        while(order && ((((1UL << order) * PAGE_SIZE) /
                                sizeof(struct dn_rt_hash_bucket)) >= 2048))
                order--;

        do {
                dn_rt_hash_mask = (1UL << order) * PAGE_SIZE /
                        sizeof(struct dn_rt_hash_bucket);
                while(dn_rt_hash_mask & (dn_rt_hash_mask - 1))
                        dn_rt_hash_mask--;
                dn_rt_hash_table = (struct dn_rt_hash_bucket *)
                        __get_free_pages(GFP_ATOMIC, order);
        } while (dn_rt_hash_table == NULL && --order > 0);

        if (!dn_rt_hash_table)
                panic("Failed to allocate DECnet route cache hash table\n");

        printk(KERN_INFO
                "DECnet: Routing cache hash table of %u buckets, %ldKbytes\n",
                dn_rt_hash_mask,
                (long)(dn_rt_hash_mask*sizeof(struct dn_rt_hash_bucket))/1024);

        dn_rt_hash_mask--;
        for(i = 0; i <= dn_rt_hash_mask; i++) {
                spin_lock_init(&dn_rt_hash_table[i].lock);
                dn_rt_hash_table[i].chain = NULL;
        }

        dn_dst_ops.gc_thresh = (dn_rt_hash_mask + 1);

        proc_net_fops_create(&init_net, "decnet_cache", S_IRUGO, &dn_rt_cache_seq_fops);

#ifdef CONFIG_DECNET_ROUTER
        rtnl_register(PF_DECnet, RTM_GETROUTE, dn_cache_getroute, dn_fib_dump);
#else
        rtnl_register(PF_DECnet, RTM_GETROUTE, dn_cache_getroute,
                      dn_cache_dump);
#endif
}

void __exit dn_route_cleanup(void)
{
        del_timer(&dn_route_timer);
        dn_run_flush(0);

        proc_net_remove(&init_net, "decnet_cache");
        dst_entries_destroy(&dn_dst_ops);
}