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dn_route.c

/*
 * 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 <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 *chain;
      spinlock_t lock;
} __attribute__((__aligned__(8)));

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(void);
static struct dst_entry *dn_dst_check(struct dst_entry *, __u32);
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 =       __constant_htons(ETH_P_DNA_RT),
      .gc_thresh =            128,
      .gc =             dn_dst_gc,
      .check =          dn_dst_check,
      .negative_advice =      dn_dst_negative_advice,
      .link_failure =         dn_dst_link_failure,
      .update_pmtu =          dn_dst_update_pmtu,
      .entry_size =           sizeof(struct dn_route),
      .entries =        ATOMIC_INIT(0),
};

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->u.dst.rcu_head, dst_rcu_free);
}

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

static void dn_dst_check_expire(unsigned long dummy)
{
      int i;
      struct dn_route *rt, **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=*rtp) != NULL) {
                  if (atomic_read(&rt->u.dst.__refcnt) ||
                              (now - rt->u.dst.lastuse) < expire) {
                        rtp = &rt->u.dst.dn_next;
                        continue;
                  }
                  *rtp = rt->u.dst.dn_next;
                  rt->u.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(void)
{
      struct dn_route *rt, **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=*rtp) != NULL) {
                  if (atomic_read(&rt->u.dst.__refcnt) ||
                              (now - rt->u.dst.lastuse) < expire) {
                        rtp = &rt->u.dst.dn_next;
                        continue;
                  }
                  *rtp = rt->u.dst.dn_next;
                  rt->u.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 ?
                      (struct dn_dev *)dst->neighbour->dev->dn_ptr : NULL;

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

      if (dst->metrics[RTAX_MTU-1] > mtu && mtu >= min_mtu) {
            if (!(dst_metric_locked(dst, RTAX_MTU))) {
                  dst->metrics[RTAX_MTU-1] = mtu;
                  dst_set_expires(dst, dn_rt_mtu_expires);
            }
            if (!(dst_metric_locked(dst, RTAX_ADVMSS))) {
                  u32 mss = mtu - DN_MAX_NSP_DATA_HEADER;
                  if (dst->metrics[RTAX_ADVMSS-1] > mss)
                        dst->metrics[RTAX_ADVMSS-1] = 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)
{
      return;
}

static inline int compare_keys(struct flowi *fl1, struct flowi *fl2)
{
      return ((fl1->nl_u.dn_u.daddr ^ fl2->nl_u.dn_u.daddr) |
            (fl1->nl_u.dn_u.saddr ^ fl2->nl_u.dn_u.saddr) |
            (fl1->mark ^ fl2->mark) |
            (fl1->nl_u.dn_u.scope ^ fl2->nl_u.dn_u.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, **rthp;
      unsigned long now = jiffies;

      rthp = &dn_rt_hash_table[hash].chain;

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

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

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

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

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

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(&dn_rt_hash_table[i].chain, NULL)) == NULL)
                  goto nothing_to_declare;

            for(; rt; rt=next) {
                  next = rt->u.dst.dn_next;
                  rt->u.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;
      __le16 tmp;

      /* 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 source and destination */
      tmp  = *src;
      *src = *dst;
      *dst = tmp;

      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 = DN_SKB_CB(skb);
      int err;

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

      if (decnet_debug_level & 4) {
            char *devname = skb->dev ? skb->dev->name : "???";
            struct dn_skb_cb *cb = DN_SKB_CB(skb);
            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,
                  dn_ntohs(cb->src), dn_ntohs(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(PF_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(PF_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 = dn_ntohs(*(__le16 *)skb->data);
      struct dn_dev *dn = (struct dn_dev *)dev->dn_ptr;
      unsigned char padlen = 0;

      if (dev->nd_net != &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(PF_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(PF_DECnet, NF_DN_ROUTE, skb, skb->dev, NULL, dn_route_discard);
                  case DN_RT_PKT_ERTH:
                        return NF_HOOK(PF_DECnet, NF_DN_HELLO, skb, skb->dev, NULL, dn_neigh_router_hello);

                  case DN_RT_PKT_EEDH:
                        return NF_HOOK(PF_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;
      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(PF_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;
      struct dn_dev *dn_db = 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;
      header_len = dn_db->use_long ? 21 : 6;
      if (skb_cow(skb, LL_RESERVED_SPACE(rt->u.dst.dev)+header_len))
            goto drop;

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

      skb->dev = rt->u.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(PF_DECnet, NF_DN_FORWARD, skb, dev, skb->dev, neigh->output);

drop:
      kfree_skb(skb);
      return NET_RX_DROP;
}

/*
 * Drop packet. This is used for endnodes and for
 * when we should not be forwarding packets from
 * this dest.
 */
static int dn_blackhole(struct sk_buff *skb)
{
      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",
                        dn_ntohs(cb->src), dn_ntohs(cb->dst));
      }

      kfree_skb(skb);

      return NET_RX_BAD;
}

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->u.dst.dev;
      struct neighbour *n;
      unsigned mss;

      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);
            memcpy(rt->u.dst.metrics, fi->fib_metrics,
                   sizeof(rt->u.dst.metrics));
      }
      rt->rt_type = res->type;

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

      if (rt->u.dst.metrics[RTAX_MTU-1] == 0 ||
          rt->u.dst.metrics[RTAX_MTU-1] > rt->u.dst.dev->mtu)
            rt->u.dst.metrics[RTAX_MTU-1] = rt->u.dst.dev->mtu;
      mss = dn_mss_from_pmtu(dev, dst_mtu(&rt->u.dst));
      if (rt->u.dst.metrics[RTAX_ADVMSS-1] == 0 ||
          rt->u.dst.metrics[RTAX_ADVMSS-1] > mss)
            rt->u.dst.metrics[RTAX_ADVMSS-1] = mss;
      return 0;
}

static inline int dn_match_addr(__le16 addr1, __le16 addr2)
{
      __u16 tmp = dn_ntohs(addr1) ^ dn_ntohs(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 = dev->dn_ptr;
      struct dn_ifaddr *ifa;
      int best_match = 0;
      int ret;

      read_lock(&dev_base_lock);
      for(ifa = dn_db->ifa_list; ifa; ifa = 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;
      }
      read_unlock(&dev_base_lock);

      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 = { .nl_u = { .dn_u =
                              { .daddr = oldflp->fld_dst,
                              .saddr = oldflp->fld_src,
                              .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", dn_ntohs(oldflp->fld_dst),
                   dn_ntohs(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;
            }
            read_lock(&dev_base_lock);
            for_each_netdev(&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;
            }
            read_unlock(&dev_base_lock);
            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",
                   dn_ntohs(fl.fld_dst), dn_ntohs(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, &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 = 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->u.dst.__refcnt, 1);
      rt->u.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->u.dst.dev = dev_out;
      dev_hold(dev_out);
      rt->u.dst.neighbour = neigh;
      neigh = NULL;

      rt->u.dst.lastuse = jiffies;
      rt->u.dst.output  = dn_output;
      rt->u.dst.input   = dn_rt_bug;
      rt->rt_flags      = flags;
      if (flags & RTCF_LOCAL)
            rt->u.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->u.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(dn_rt_hash_table[hash].chain); rt;
                  rt = rcu_dereference(rt->u.dst.dn_next)) {
                  if ((flp->fld_dst == rt->fl.fld_dst) &&
                      (flp->fld_src == rt->fl.fld_src) &&
                      (flp->mark == rt->fl.mark) &&
                      (rt->fl.iif == 0) &&
                      (rt->fl.oif == flp->oif)) {
                        dst_use(&rt->u.dst, jiffies);
                        rcu_read_unlock_bh();
                        *pprt = &rt->u.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(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(pprt, fl, sk, !(flags & MSG_DONTWAIT));
      }
      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 = { .nl_u = { .dn_u =
                             { .daddr = cb->dst,
                               .saddr = cb->src,
                               .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 = 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->u.dst.flags = DST_HOST;
      rt->u.dst.neighbour = neigh;
      rt->u.dst.dev = out_dev;
      rt->u.dst.lastuse = jiffies;
      rt->u.dst.output = dn_rt_bug;
      switch(res.type) {
            case RTN_UNICAST:
                  rt->u.dst.input = dn_forward;
                  break;
            case RTN_LOCAL:
                  rt->u.dst.output = dn_output;
                  rt->u.dst.input = dn_nsp_rx;
                  rt->u.dst.dev = in_dev;
                  flags |= RTCF_LOCAL;
                  break;
            default:
            case RTN_UNREACHABLE:
            case RTN_BLACKHOLE:
                  rt->u.dst.input = dn_blackhole;
      }
      rt->rt_flags = flags;
      if (rt->u.dst.dev)
            dev_hold(rt->u.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, (struct dn_route **)&skb->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->u.dst);
      goto done;
}

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)
            return 0;

      rcu_read_lock();
      for(rt = rcu_dereference(dn_rt_hash_table[hash].chain); rt != NULL;
          rt = rcu_dereference(rt->u.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->u.dst, jiffies);
                  rcu_read_unlock();
                  skb->dst = (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;
      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->u.dst.dev)
            RTA_PUT(skb, RTA_OIF, sizeof(int), &rt->u.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, rt->u.dst.metrics) < 0)
            goto rtattr_failure;
      expires = rt->u.dst.expires ? rt->u.dst.expires - jiffies : 0;
      if (rtnl_put_cacheinfo(skb, &rt->u.dst, 0, 0, 0, expires,
                         rt->u.dst.error) < 0)
            goto rtattr_failure;
      if (rt->fl.iif)
            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 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;

      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 = __constant_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;
            if (!err && -rt->u.dst.error)
                  err = rt->u.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 = &rt->u.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, 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 dn_route *rt;
      int h, s_h;
      int idx, s_idx;

      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(dn_rt_hash_table[h].chain), idx = 0;
                  rt;
                  rt = rcu_dereference(rt->u.dst.dn_next), idx++) {
                  if (idx < s_idx)
                        continue;
                  skb->dst = dst_clone(&rt->u.dst);
                  if (dn_rt_fill_info(skb, NETLINK_CB(cb->skb).pid,
                              cb->nlh->nlmsg_seq, RTM_NEWROUTE,
                              1, NLM_F_MULTI) <= 0) {
                        dst_release(xchg(&skb->dst, NULL));
                        rcu_read_unlock_bh();
                        goto done;
                  }
                  dst_release(xchg(&skb->dst, NULL));
            }
            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 = dn_rt_hash_table[s->bucket].chain;
            if (rt)
                  break;
            rcu_read_unlock_bh();
      }
      return rcu_dereference(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 = rt->u.dst.dn_next;
      while(!rt) {
            rcu_read_unlock_bh();
            if (--s->bucket < 0)
                  break;
            rcu_read_lock_bh();
            rt = dn_rt_hash_table[s->bucket].chain;
      }
      return rcu_dereference(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->u.dst.dev ? rt->u.dst.dev->name : "*",
                  dn_addr2asc(dn_ntohs(rt->rt_daddr), buf1),
                  dn_addr2asc(dn_ntohs(rt->rt_saddr), buf2),
                  atomic_read(&rt->u.dst.__refcnt),
                  rt->u.dst.__use,
                  (int) dst_metric(&rt->u.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);
      init_timer(&dn_route_timer);
      dn_route_timer.function = dn_dst_check_expire;
      dn_route_timer.expires = jiffies + decnet_dst_gc_interval * HZ;
      add_timer(&dn_route_timer);

      goal = num_physpages >> (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");
}


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