text: // SPDX-License-Identifier: GPL-2.0-or-later
  /*
   * 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
  
  *******************************************************************************/
  
  #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,
  			       bool confirm_neigh);
  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(struct timer_list *unused);
  
  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);
  int decnet_dst_gc_interval = 2;
  
  static struct dst_ops dn_dst_ops = {
  	.family =		PF_DECnet,
  	.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 void dn_dst_check_expire(struct timer_list *unused)
  {
  	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) > 1 ||
  			    (now - rt->dst.lastuse) < expire) {
  				rtp = &rt->dn_next;
  				continue;
  			}
  			*rtp = rt->dn_next;
  			rt->dn_next = NULL;
  			dst_dev_put(&rt->dst);
  			dst_release(&rt->dst);
  		}
  		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) > 1 ||
  			    (now - rt->dst.lastuse) < expire) {
  				rtp = &rt->dn_next;
  				continue;
  			}
  			*rtp = rt->dn_next;
  			rt->dn_next = NULL;
  			dst_dev_put(&rt->dst);
  			dst_release(&rt->dst);
  			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,
  			       bool confirm_neigh)
  {
  	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->dn_next;
  			rcu_assign_pointer(rth->dn_next,
  					   dn_rt_hash_table[hash].chain);
  			rcu_assign_pointer(dn_rt_hash_table[hash].chain, rth);
  
  			dst_hold_and_use(&rth->dst, now);
  			spin_unlock_bh(&dn_rt_hash_table[hash].lock);
  
  			dst_release_immediate(&rt->dst);
  			*rp = rth;
  			return 0;
  		}
  		rthp = &rth->dn_next;
  	}
  
  	rcu_assign_pointer(rt->dn_next, dn_rt_hash_table[hash].chain);
  	rcu_assign_pointer(dn_rt_hash_table[hash].chain, rt);
  
  	dst_hold_and_use(&rt->dst, now);
  	spin_unlock_bh(&dn_rt_hash_table[hash].lock);
  	*rp = rt;
  	return 0;
  }
  
  static void dn_run_flush(struct timer_list *unused)
  {
  	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);
  
  		rt = xchg((struct dn_route **)&dn_rt_hash_table[i].chain, NULL);
  		if (!rt)
  			goto nothing_to_declare;
  
  		for (; rt; rt = next) {
  			next = rcu_dereference_raw(rt->dn_next);
  			RCU_INIT_POINTER(rt->dn_next, NULL);
  			dst_dev_put(&rt->dst);
  			dst_release(&rt->dst);
  		}
  
  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(NULL);
  		return;
  	}
  
  	if (dn_rt_deadline == 0)
  		dn_rt_deadline = now + dn_rt_max_delay;
  
  	dn_rt_flush_timer.expires = now + delay;
  	add_timer(&dn_rt_flush_timer);
  	spin_unlock_bh(&dn_rt_flush_lock);
  }
  
  /**
   * dn_return_short - Return a short packet to its sender
   * @skb: The packet to return
   *
   */
  static int dn_return_short(struct sk_buff *skb)
  {
  	struct dn_skb_cb *cb;
  	unsigned char *ptr;
  	__le16 *src;
  	__le16 *dst;
  
  	/* Add back headers */
  	skb_push(skb, skb->data - skb_network_header(skb));
  
  	skb = skb_unshare(skb, GFP_ATOMIC);
  	if (!skb)
  		return NET_RX_DROP;
  
  	cb = DN_SKB_CB(skb);
  	/* Skip packet length and point to flags */
  	ptr = skb->data + 2;
  	*ptr++ = (cb->rt_flags & ~DN_RT_F_RQR) | DN_RT_F_RTS;
  
  	dst = (__le16 *)ptr;
  	ptr += 2;
  	src = (__le16 *)ptr;
  	ptr += 2;
  	*ptr = 0; /* Zero hop count */
  
  	swap(*src, *dst);
  
  	skb->pkt_type = PACKET_OUTGOING;
  	dn_rt_finish_output(skb, NULL, NULL);
  	return NET_RX_SUCCESS;
  }
  
  /**
   * dn_return_long - Return a long packet to its sender
   * @skb: The long format packet to return
   *
   */
  static int dn_return_long(struct sk_buff *skb)
  {
  	struct dn_skb_cb *cb;
  	unsigned char *ptr;
  	unsigned char *src_addr, *dst_addr;
  	unsigned char tmp[ETH_ALEN];
  
  	/* Add back all headers */
  	skb_push(skb, skb->data - skb_network_header(skb));
  
  	skb = skb_unshare(skb, GFP_ATOMIC);
  	if (!skb)
  		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
   * @net: The applicable net namespace
   * @sk: Socket packet transmitted on
   * @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 net *net, struct sock *sk, struct sk_buff *skb)
  {
  	struct dn_skb_cb *cb;
  	int err;
  
  	err = dn_route_input(skb);
  	if (err == 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,
  		       &init_net, NULL, 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,
  		       &init_net, NULL, skb, skb->dev, NULL,
  		       dn_route_rx_packet);
  
  drop_it:
  	kfree_skb(skb);
  	return NET_RX_DROP;
  }
  
  static int dn_route_discard(struct net *net, struct sock *sk, struct sk_buff *skb)
  {
  	/*
  	 * I know we drop the packet here, but that's considered success in
  	 * this case
  	 */
  	kfree_skb(skb);
  	return NET_RX_SUCCESS;
  }
  
  static int dn_route_ptp_hello(struct net *net, struct sock *sk, 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;
  
  	skb = skb_share_check(skb, GFP_ATOMIC);
  	if (!skb)
  		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->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,
  				       &init_net, NULL, 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,
  				       &init_net, NULL, skb, skb->dev, NULL,
  				       dn_route_discard);
  		case DN_RT_PKT_ERTH:
  			return NF_HOOK(NFPROTO_DECNET, NF_DN_HELLO,
  				       &init_net, NULL, skb, skb->dev, NULL,
  				       dn_neigh_router_hello);
  
  		case DN_RT_PKT_EEDH:
  			return NF_HOOK(NFPROTO_DECNET, NF_DN_HELLO,
  				       &init_net, NULL, 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 net *net, struct sock *sk, 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,
  		       &init_net, sk, 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;
  	struct net_device *dev = skb->dev;
  
  	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,
  		       &init_net, NULL, 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_out(struct net *net, struct sock *sk, 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 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;
  
  		dev_put(dev_out);
  		err = -EINVAL;
  		dev_out = init_net.loopback_dev;
  		if (!dev_out->dn_ptr)
  			goto out;
  		err = -EADDRNOTAVAIL;
  		dev_hold(dev_out);
  		if (!fld.daddr) {
  			fld.daddr =
  			fld.saddr = dnet_select_source(dev_out, 0,
  						       RT_SCOPE_HOST);
  			if (!fld.daddr)
  				goto done;
  		}
  		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=%04x 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 {
  					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);
  		if (!dn_db)
  			goto e_inval;
  		/* 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 = container_of(neigh, struct dn_neigh, n)->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;
  		dev_put(dev_out);
  		dev_out = init_net.loopback_dev;
  		dev_hold(dev_out);
  		if (!dev_out->dn_ptr)
  			goto e_inval;
  		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);
  
  	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, 0, DST_OBSOLETE_NONE, 0);
  	if (rt == NULL)
  		goto e_nobufs;
  
  	rt->dn_next = NULL;
  	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() increments dst->__refcnt */
  	dn_insert_route(rt, hash, (struct dn_route **)pprt);
  
  done:
  	if (neigh)
  		neigh_release(neigh);
  	if (free_res)
  		dn_fib_res_put(&res);
  	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_release_immediate(&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->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_hold_and_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 __rcu **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) {
  		*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);
  
  	dn_db = rcu_dereference(in_dev->dn_ptr);
  	if (!dn_db)
  		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);
  		break;
  	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 = container_of(neigh, struct dn_neigh, n)->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, 1, DST_OBSOLETE_NONE, 0);
  	if (rt == NULL)
  		goto e_nobufs;
  
  	rt->dn_next = NULL;
  	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_out;
  	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() increments dst->__refcnt */
  	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);
  	dev_put(out_dev);
  out:
  	return err;
  
  e_inval:
  	err = -EINVAL;
  	goto done;
  
  e_nobufs:
  	err = -ENOBUFS;
  	goto done;
  
  e_neighbour:
  	dst_release_immediate(&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->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_hold_and_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;
  
  	nlmsg_end(skb, nlh);
  	return 0;
  
  errout:
  	nlmsg_cancel(skb, nlh);
  	return -EMSGSIZE;
  }
  
  const struct nla_policy rtm_dn_policy[RTA_MAX + 1] = {
  	[RTA_DST]		= { .type = NLA_U16 },
  	[RTA_SRC]		= { .type = NLA_U16 },
  	[RTA_IIF]		= { .type = NLA_U32 },
  	[RTA_OIF]		= { .type = NLA_U32 },
  	[RTA_GATEWAY]		= { .type = NLA_U16 },
  	[RTA_PRIORITY]		= { .type = NLA_U32 },
  	[RTA_PREFSRC]		= { .type = NLA_U16 },
  	[RTA_METRICS]		= { .type = NLA_NESTED },
  	[RTA_MULTIPATH]		= { .type = NLA_NESTED },
  	[RTA_TABLE]		= { .type = NLA_U32 },
  	[RTA_MARK]		= { .type = NLA_U32 },
  };
  
  /*
   * This is called by both endnodes and routers now.
   */
  static int dn_cache_getroute(struct sk_buff *in_skb, struct nlmsghdr *nlh,
  			     struct netlink_ext_ack *extack)
  {
  	struct net *net = sock_net(in_skb->sk);
  	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;
  	struct nlattr *tb[RTA_MAX+1];
  
  	if (!net_eq(net, &init_net))
  		return -EINVAL;
  
  	err = nlmsg_parse_deprecated(nlh, sizeof(*rtm), tb, RTA_MAX,
  				     rtm_dn_policy, extack);
  	if (err < 0)
  		return err;
  
  	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 (tb[RTA_SRC])
  		fld.saddr = nla_get_le16(tb[RTA_SRC]);
  
  	if (tb[RTA_DST])
  		fld.daddr = nla_get_le16(tb[RTA_DST]);
  
  	if (tb[RTA_IIF])
  		fld.flowidn_iif = nla_get_u32(tb[RTA_IIF]);
  
  	if (fld.flowidn_iif) {
  		struct net_device *dev;
  		dev = __dev_get_by_index(&init_net, fld.flowidn_iif);
  		if (!dev || !dev->dn_ptr) {
  			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 {
  		if (tb[RTA_OIF])
  			fld.flowidn_oif = nla_get_u32(tb[RTA_OIF]);
  
  		err = dn_route_output_key((struct dst_entry **)&rt, &fld, 0);
  	}
  
  	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) {
  		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->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->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,
  };
  #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);
  	timer_setup(&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_create_seq_private("decnet_cache", 0444, init_net.proc_net,
  			&dn_rt_cache_seq_ops,
  			sizeof(struct dn_rt_cache_iter_state), NULL);
  
  #ifdef CONFIG_DECNET_ROUTER
  	rtnl_register_module(THIS_MODULE, PF_DECnet, RTM_GETROUTE,
  			     dn_cache_getroute, dn_fib_dump, 0);
  #else
  	rtnl_register_module(THIS_MODULE, PF_DECnet, RTM_GETROUTE,
  			     dn_cache_getroute, dn_cache_dump, 0);
  #endif
  }
  
  void __exit dn_route_cleanup(void)
  {
  	del_timer(&dn_route_timer);
  	dn_run_flush(NULL);
  
  	remove_proc_entry("decnet_cache", init_net.proc_net);
  	dst_entries_destroy(&dn_dst_ops);
  }
  