dn_route.c

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/*
 * 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 <[email protected]>
 *              Eduardo Marcelo Serrat <[email protected]>
 *
 * 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       [email protected]

    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 <linux/export.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_mtu(const struct dst_entry *dst);
static void dn_dst_destroy(struct dst_entry *);
static void dn_dst_ifdown(struct dst_entry *, struct net_device *dev, int how);
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, struct sock *sk,
                   struct sk_buff *skb , u32 mtu);
static void dn_dst_redirect(struct dst_entry *dst, struct sock *sk,
                struct sk_buff *skb);
static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst,
                         struct sk_buff *skb,
                         const void *daddr);
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 int 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,
    .mtu =          dn_dst_mtu,
    .cow_metrics =      dst_cow_metrics_generic,
    .destroy =      dn_dst_destroy,
    .ifdown =       dn_dst_ifdown,
    .negative_advice =  dn_dst_negative_advice,
    .link_failure =     dn_dst_link_failure,
    .update_pmtu =      dn_dst_update_pmtu,
    .redirect =     dn_dst_redirect,
    .neigh_lookup =     dn_dst_neigh_lookup,
};

static void dn_dst_destroy(struct dst_entry *dst)
{
    struct dn_route *rt = (struct dn_route *) dst;

    if (rt->n)
        neigh_release(rt->n);
    dst_destroy_metrics_generic(dst);
}

static void dn_dst_ifdown(struct dst_entry *dst, struct net_device *dev, int how)
{
    if (how) {
        struct dn_route *rt = (struct dn_route *) dst;
        struct neighbour *n = rt->n;

        if (n && n->dev == dev) {
            n->dev = dev_net(dev)->loopback_dev;
            dev_hold(n->dev);
            dev_put(dev);
        }
    }
}

static __inline__ unsigned int 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 int)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, struct sock *sk,
                   struct sk_buff *skb, u32 mtu)
{
    struct dn_route *rt = (struct dn_route *) dst;
    struct neighbour *n = rt->n;
    u32 min_mtu = 230;
    struct dn_dev *dn;

    dn = n ? rcu_dereference_raw(n->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);
        }
    }
}

static void dn_dst_redirect(struct dst_entry *dst, struct sock *sk,
                struct sk_buff *skb)
{
}

/*
 * 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 flowidn *fl1, struct flowidn *fl2)
{
    return ((fl1->daddr ^ fl2->daddr) |
        (fl1->saddr ^ fl2->saddr) |
        (fl1->flowidn_mark ^ fl2->flowidn_mark) |
        (fl1->flowidn_scope ^ fl2->flowidn_scope) |
        (fl1->flowidn_oif ^ fl2->flowidn_oif) |
        (fl1->flowidn_iif ^ fl2->flowidn_iif)) == 0;
}

static int dn_insert_route(struct dn_route *rt, unsigned int 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->fld, &rt->fld)) {
            /* 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);
}

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;
}

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;
}

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_to_neigh_output(struct sk_buff *skb)
{
    struct dst_entry *dst = skb_dst(skb);
    struct dn_route *rt = (struct dn_route *) dst;
    struct neighbour *n = rt->n;

    return n->output(n, skb);
}

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);

    int err = -EINVAL;

    if (rt->n == 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,
               dn_to_neigh_output);

error:
    net_dbg_ratelimited("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;
    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,
               dn_to_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)
{
    struct dn_skb_cb *cb = DN_SKB_CB(skb);

    net_dbg_ratelimited("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_mtu(const struct dst_entry *dst)
{
    unsigned int mtu = dst_metric_raw(dst, RTAX_MTU);

    return mtu ? : dst->dev->mtu;
}

static struct neighbour *dn_dst_neigh_lookup(const struct dst_entry *dst,
                         struct sk_buff *skb,
                         const void *daddr)
{
    return __neigh_lookup_errno(&dn_neigh_table, daddr, dst->dev);
}

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;
    unsigned int mss_metric;
    struct neighbour *n;

    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_init_metrics(&rt->dst, fi->fib_metrics, true);
    }
    rt->rt_type = res->type;

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

    if (dst_metric(&rt->dst, RTAX_MTU) > rt->dst.dev->mtu)
        dst_metric_set(&rt->dst, RTAX_MTU, rt->dst.dev->mtu);
    mss_metric = dst_metric_raw(&rt->dst, RTAX_ADVMSS);
    if (mss_metric) {
        unsigned int mss = dn_mss_from_pmtu(dev, dst_mtu(&rt->dst));
        if (mss_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 flowidn *oldflp, int try_hard)
{
    struct flowidn fld = {
        .daddr = oldflp->daddr,
        .saddr = oldflp->saddr,
        .flowidn_scope = RT_SCOPE_UNIVERSE,
        .flowidn_mark = oldflp->flowidn_mark,
        .flowidn_iif = LOOPBACK_IFINDEX,
        .flowidn_oif = oldflp->flowidn_oif,
    };
    struct dn_route *rt = NULL;
    struct net_device *dev_out = NULL, *dev;
    struct neighbour *neigh = NULL;
    unsigned int hash;
    unsigned int 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->daddr),
               le16_to_cpu(oldflp->saddr),
               oldflp->flowidn_mark, LOOPBACK_IFINDEX,
               oldflp->flowidn_oif);

    /* If we have an output interface, verify its a DECnet device */
    if (oldflp->flowidn_oif) {
        dev_out = dev_get_by_index(&init_net, oldflp->flowidn_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->saddr) {
        err = -EADDRNOTAVAIL;

        if (dev_out) {
            if (dn_dev_islocal(dev_out, oldflp->saddr))
                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->saddr))
                continue;
            if ((dev->flags & IFF_LOOPBACK) &&
                oldflp->daddr &&
                !dn_dev_islocal(dev, oldflp->daddr))
                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 (!fld.daddr) {
        fld.daddr = fld.saddr;

        err = -EADDRNOTAVAIL;
        if (dev_out)
            dev_put(dev_out);
        dev_out = init_net.loopback_dev;
        dev_hold(dev_out);
        if (!fld.daddr) {
            fld.daddr =
            fld.saddr = dnet_select_source(dev_out, 0,
                               RT_SCOPE_HOST);
            if (!fld.daddr)
                goto out;
        }
        fld.flowidn_oif = LOOPBACK_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(fld.daddr), le16_to_cpu(fld.saddr),
               fld.flowidn_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(&fld, &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, &fld.daddr);
            if (neigh) {
                if ((oldflp->flowidn_oif &&
                    (neigh->dev->ifindex != oldflp->flowidn_oif)) ||
                    (oldflp->saddr &&
                    (!dn_dev_islocal(neigh->dev,
                             oldflp->saddr)))) {
                    neigh_release(neigh);
                    neigh = NULL;
                } else {
                    if (dev_out)
                        dev_put(dev_out);
                    if (dn_dev_islocal(neigh->dev, fld.daddr)) {
                        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, fld.daddr)) {
            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 = fld.daddr;
        if (fld.saddr == 0) {
            fld.saddr = dnet_select_source(dev_out, gateway,
                               res.type == RTN_LOCAL ?
                               RT_SCOPE_HOST :
                               RT_SCOPE_LINK);
            if (fld.saddr == 0 && res.type != RTN_LOCAL)
                goto e_addr;
        }
        fld.flowidn_oif = dev_out->ifindex;
        goto make_route;
    }
    free_res = 1;

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

    if (res.type == RTN_LOCAL) {
        if (!fld.saddr)
            fld.saddr = fld.daddr;
        if (dev_out)
            dev_put(dev_out);
        dev_out = init_net.loopback_dev;
        dev_hold(dev_out);
        fld.flowidn_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 && fld.flowidn_oif == 0)
        dn_fib_select_multipath(&fld, &res);

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

    if (!fld.saddr)
        fld.saddr = DN_FIB_RES_PREFSRC(res);

    if (dev_out)
        dev_put(dev_out);
    dev_out = DN_FIB_RES_DEV(res);
    dev_hold(dev_out);
    fld.flowidn_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, dev_out, 1, DST_OBSOLETE_NONE, DST_HOST);
    if (rt == NULL)
        goto e_nobufs;

    memset(&rt->fld, 0, sizeof(rt->fld));
    rt->fld.saddr        = oldflp->saddr;
    rt->fld.daddr        = oldflp->daddr;
    rt->fld.flowidn_oif  = oldflp->flowidn_oif;
    rt->fld.flowidn_iif  = 0;
    rt->fld.flowidn_mark = oldflp->flowidn_mark;

    rt->rt_saddr      = fld.saddr;
    rt->rt_daddr      = fld.daddr;
    rt->rt_gateway    = gateway ? gateway : fld.daddr;
    rt->rt_local_src  = fld.saddr;

    rt->rt_dst_map    = fld.daddr;
    rt->rt_src_map    = fld.saddr;

    rt->n = 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->fld.saddr, rt->fld.daddr);
    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 flowidn *flp, int flags)
{
    unsigned int hash = dn_hash(flp->saddr, flp->daddr);
    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->daddr == rt->fld.daddr) &&
                (flp->saddr == rt->fld.saddr) &&
                (flp->flowidn_mark == rt->fld.flowidn_mark) &&
                dn_is_output_route(rt) &&
                (rt->fld.flowidn_oif == flp->flowidn_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 flowidn *flp, int flags)
{
    int err;

    err = __dn_route_output_key(pprt, flp, flags);
    if (err == 0 && flp->flowidn_proto) {
        *pprt = xfrm_lookup(&init_net, *pprt,
                    flowidn_to_flowi(flp), NULL, 0);
        if (IS_ERR(*pprt)) {
            err = PTR_ERR(*pprt);
            *pprt = NULL;
        }
    }
    return err;
}

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

    err = __dn_route_output_key(pprt, fl, flags & MSG_TRYHARD);
    if (err == 0 && fl->flowidn_proto) {
        if (!(flags & MSG_DONTWAIT))
            fl->flowidn_flags |= FLOWI_FLAG_CAN_SLEEP;
        *pprt = xfrm_lookup(&init_net, *pprt,
                    flowidn_to_flowi(fl), sk, 0);
        if (IS_ERR(*pprt)) {
            err = PTR_ERR(*pprt);
            *pprt = NULL;
        }
    }
    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 int hash;
    int flags = 0;
    __le16 gateway = 0;
    __le16 local_src = 0;
    struct flowidn fld = {
        .daddr = cb->dst,
        .saddr = cb->src,
        .flowidn_scope = RT_SCOPE_UNIVERSE,
        .flowidn_mark = skb->mark,
        .flowidn_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 (fld.saddr == 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(&fld, &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 = fld.saddr;
        free_res = 1;

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

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

        gateway = DN_FIB_RES_GW(res);
        if (res.type == RTN_NAT) {
            fld.daddr = dn_fib_rules_map_destination(fld.daddr, &res);
            dn_fib_res_put(&res);
            free_res = 0;
            if (dn_fib_lookup(&fld, &res))
                goto e_inval;
            free_res = 1;
            if (res.type != RTN_UNICAST)
                goto e_inval;
            flags |= RTCF_DNAT;
            gateway = fld.daddr;
        }
        fld.saddr = 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 && fld.flowidn_oif == 0)
            dn_fib_select_multipath(&fld, &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;
        fld.saddr = cb->dst;
        fld.daddr = 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;
            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;
        goto make_route;
    default:
        goto e_inval;
    }

make_route:
    rt = dst_alloc(&dn_dst_ops, out_dev, 0, DST_OBSOLETE_NONE, DST_HOST);
    if (rt == NULL)
        goto e_nobufs;

    memset(&rt->fld, 0, sizeof(rt->fld));
    rt->rt_saddr      = fld.saddr;
    rt->rt_daddr      = fld.daddr;
    rt->rt_gateway    = fld.daddr;
    if (gateway)
        rt->rt_gateway = gateway;
    rt->rt_local_src  = local_src ? local_src : rt->rt_saddr;

    rt->rt_dst_map    = fld.daddr;
    rt->rt_src_map    = fld.saddr;

    rt->fld.saddr        = cb->src;
    rt->fld.daddr        = cb->dst;
    rt->fld.flowidn_oif  = 0;
    rt->fld.flowidn_iif  = in_dev->ifindex;
    rt->fld.flowidn_mark = fld.flowidn_mark;

    rt->n = neigh;
    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;

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

    hash = dn_hash(rt->fld.saddr, rt->fld.daddr);
    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 int 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->fld.saddr == cb->src) &&
            (rt->fld.daddr == cb->dst) &&
            (rt->fld.flowidn_oif == 0) &&
            (rt->fld.flowidn_mark == skb->mark) &&
            (rt->fld.flowidn_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 portid, 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;
    long expires;

    nlh = nlmsg_put(skb, portid, seq, event, sizeof(*r), flags);
    if (!nlh)
        return -EMSGSIZE;

    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;
    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;

    if (nla_put_u32(skb, RTA_TABLE, RT_TABLE_MAIN) < 0 ||
        nla_put_le16(skb, RTA_DST, rt->rt_daddr) < 0)
        goto errout;

    if (rt->fld.saddr) {
        r->rtm_src_len = 16;
        if (nla_put_le16(skb, RTA_SRC, rt->fld.saddr) < 0)
            goto errout;
    }
    if (rt->dst.dev &&
        nla_put_u32(skb, RTA_OIF, rt->dst.dev->ifindex) < 0)
        goto errout;

    /*
     * Note to self - change this if input routes reverse direction when
     * they deal only with inputs and not with replies like they do
     * currently.
     */
    if (nla_put_le16(skb, RTA_PREFSRC, rt->rt_local_src) < 0)
        goto errout;

    if (rt->rt_daddr != rt->rt_gateway &&
        nla_put_le16(skb, RTA_GATEWAY, rt->rt_gateway) < 0)
        goto errout;

    if (rtnetlink_put_metrics(skb, dst_metrics_ptr(&rt->dst)) < 0)
        goto errout;

    expires = rt->dst.expires ? rt->dst.expires - jiffies : 0;
    if (rtnl_put_cacheinfo(skb, &rt->dst, 0, expires,
                   rt->dst.error) < 0)
        goto errout;

    if (dn_is_input_route(rt) &&
        nla_put_u32(skb, RTA_IIF, rt->fld.flowidn_iif) < 0)
        goto errout;

    return nlmsg_end(skb, nlh);

errout:
    nlmsg_cancel(skb, nlh);
    return -EMSGSIZE;
}

/*
 * 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 flowidn fld;

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

    memset(&fld, 0, sizeof(fld));
    fld.flowidn_proto = DNPROTO_NSP;

    skb = nlmsg_new(NLMSG_DEFAULT_SIZE, GFP_KERNEL);
    if (skb == NULL)
        return -ENOBUFS;
    skb_reset_mac_header(skb);
    cb = DN_SKB_CB(skb);

    if (rta[RTA_SRC-1])
        memcpy(&fld.saddr, RTA_DATA(rta[RTA_SRC-1]), 2);
    if (rta[RTA_DST-1])
        memcpy(&fld.daddr, RTA_DATA(rta[RTA_DST-1]), 2);
    if (rta[RTA_IIF-1])
        memcpy(&fld.flowidn_iif, RTA_DATA(rta[RTA_IIF-1]), sizeof(int));

    if (fld.flowidn_iif) {
        struct net_device *dev;
        if ((dev = dev_get_by_index(&init_net, fld.flowidn_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 = fld.saddr;
        cb->dst = fld.daddr;
        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));
        fld.flowidn_oif = oif;
        err = dn_route_output_key((struct dst_entry **)&rt, &fld, 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).portid, 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).portid);

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;
    struct rtmsg *rtm;

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

    if (nlmsg_len(cb->nlh) < sizeof(struct rtmsg))
        return -EINVAL;

    rtm = nlmsg_data(cb->nlh);
    if (!(rtm->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).portid,
                    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, 0);
    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, NULL);
#else
    rtnl_register(PF_DECnet, RTM_GETROUTE, dn_cache_getroute,
              dn_cache_dump, NULL);
#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);
}