// SPDX-License-Identifier: GPL-2.0

  /*
   * 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 Neighbour Functions (Adjacency Database and

   *                                                        On-Ethernet Cache)
   *
   * Author:      Steve Whitehouse <SteveW@ACM.org>
   *
   *
   * Changes:
   *     Steve Whitehouse     : Fixed router listing routine
   *     Steve Whitehouse     : Added error_report functions
   *     Steve Whitehouse     : Added default router detection
   *     Steve Whitehouse     : Hop counts in outgoing messages
   *     Steve Whitehouse     : Fixed src/dst in outgoing messages so
   *                            forwarding now stands a good chance of
   *                            working.
   *     Steve Whitehouse     : Fixed neighbour states (for now anyway).
   *     Steve Whitehouse     : Made error_report functions dummies. This
   *                            is not the right place to return skbs.
   *     Steve Whitehouse     : Convert to seq_file
   *
   */

  #include <linux/net.h>
  #include <linux/module.h>
  #include <linux/socket.h>
  #include <linux/if_arp.h>

  #include <linux/slab.h>

  #include <linux/if_ether.h>
  #include <linux/init.h>
  #include <linux/proc_fs.h>
  #include <linux/string.h>
  #include <linux/netfilter_decnet.h>
  #include <linux/spinlock.h>
  #include <linux/seq_file.h>
  #include <linux/rcupdate.h>
  #include <linux/jhash.h>

  #include <linux/atomic.h>

  #include <net/net_namespace.h>

  #include <net/neighbour.h>
  #include <net/dst.h>
  #include <net/flow.h>
  #include <net/dn.h>
  #include <net/dn_dev.h>
  #include <net/dn_neigh.h>
  #include <net/dn_route.h>

  static int dn_neigh_construct(struct neighbour *);

  static void dn_neigh_error_report(struct neighbour *, struct sk_buff *);
  static int dn_neigh_output(struct neighbour *neigh, struct sk_buff *skb);

  
  /*

   * Operations for adding the link layer header.

   */

  static const struct neigh_ops dn_neigh_ops = {

  	.family =		AF_DECnet,

  	.error_report =		dn_neigh_error_report,
  	.output =		dn_neigh_output,
  	.connected_output =	dn_neigh_output,

  };

  static u32 dn_neigh_hash(const void *pkey,
  			 const struct net_device *dev,

  			 __u32 *hash_rnd)

  {

  	return jhash_2words(*(__u16 *)pkey, 0, hash_rnd[0]);

  }

  static bool dn_key_eq(const struct neighbour *neigh, const void *pkey)
  {
  	return neigh_key_eq16(neigh, pkey);
  }

  struct neigh_table dn_neigh_table = {
  	.family =			PF_DECnet,

  	.entry_size =			NEIGH_ENTRY_SIZE(sizeof(struct dn_neigh)),

  	.key_len =			sizeof(__le16),

  	.protocol =			cpu_to_be16(ETH_P_DNA_RT),

  	.hash =				dn_neigh_hash,

  	.key_eq =			dn_key_eq,

  	.constructor =			dn_neigh_construct,
  	.id =				"dn_neigh_cache",
  	.parms ={
  		.tbl =			&dn_neigh_table,

  		.reachable_time =	30 * HZ,
  		.data = {
  			[NEIGH_VAR_MCAST_PROBES] = 0,
  			[NEIGH_VAR_UCAST_PROBES] = 0,
  			[NEIGH_VAR_APP_PROBES] = 0,
  			[NEIGH_VAR_RETRANS_TIME] = 1 * HZ,
  			[NEIGH_VAR_BASE_REACHABLE_TIME] = 30 * HZ,
  			[NEIGH_VAR_DELAY_PROBE_TIME] = 5 * HZ,
  			[NEIGH_VAR_GC_STALETIME] = 60 * HZ,

  			[NEIGH_VAR_QUEUE_LEN_BYTES] = SK_WMEM_MAX,

  			[NEIGH_VAR_PROXY_QLEN] = 0,
  			[NEIGH_VAR_ANYCAST_DELAY] = 0,
  			[NEIGH_VAR_PROXY_DELAY] = 0,
  			[NEIGH_VAR_LOCKTIME] = 1 * HZ,
  		},

  	},
  	.gc_interval =			30 * HZ,
  	.gc_thresh1 =			128,
  	.gc_thresh2 =			512,
  	.gc_thresh3 =			1024,
  };

  static int dn_neigh_construct(struct neighbour *neigh)
  {
  	struct net_device *dev = neigh->dev;

  	struct dn_neigh *dn = container_of(neigh, struct dn_neigh, n);

  	struct dn_dev *dn_db;
  	struct neigh_parms *parms;
  
  	rcu_read_lock();
  	dn_db = rcu_dereference(dev->dn_ptr);
  	if (dn_db == NULL) {
  		rcu_read_unlock();
  		return -EINVAL;
  	}
  
  	parms = dn_db->neigh_parms;
  	if (!parms) {
  		rcu_read_unlock();
  		return -EINVAL;
  	}
  
  	__neigh_parms_put(neigh->parms);
  	neigh->parms = neigh_parms_clone(parms);

  	rcu_read_unlock();

  	neigh->ops = &dn_neigh_ops;

  	neigh->nud_state = NUD_NOARP;
  	neigh->output = neigh->ops->connected_output;
  
  	if ((dev->type == ARPHRD_IPGRE) || (dev->flags & IFF_POINTOPOINT))
  		memcpy(neigh->ha, dev->broadcast, dev->addr_len);
  	else if ((dev->type == ARPHRD_ETHER) || (dev->type == ARPHRD_LOOPBACK))
  		dn_dn2eth(neigh->ha, dn->addr);
  	else {

  		net_dbg_ratelimited("Trying to create neigh for hw %d
  ",
  				    dev->type);

  		return -EINVAL;
  	}
  
  	/*
  	 * Make an estimate of the remote block size by assuming that its
  	 * two less then the device mtu, which it true for ethernet (and
  	 * other things which support long format headers) since there is
  	 * an extra length field (of 16 bits) which isn't part of the
  	 * ethernet headers and which the DECnet specs won't admit is part
  	 * of the DECnet routing headers either.
  	 *
  	 * If we over estimate here its no big deal, the NSP negotiations
  	 * will prevent us from sending packets which are too large for the
  	 * remote node to handle. In any case this figure is normally updated
  	 * by a hello message in most cases.
  	 */
  	dn->blksize = dev->mtu - 2;
  
  	return 0;
  }

  static void dn_neigh_error_report(struct neighbour *neigh, struct sk_buff *skb)

  {

  	printk(KERN_DEBUG "dn_neigh_error_report: called
  ");

  	kfree_skb(skb);
  }

  static int dn_neigh_output(struct neighbour *neigh, struct sk_buff *skb)

  {

  	struct dst_entry *dst = skb_dst(skb);

  	struct dn_route *rt = (struct dn_route *)dst;

  	struct net_device *dev = neigh->dev;
  	char mac_addr[ETH_ALEN];

  	unsigned int seq;
  	int err;

  
  	dn_dn2eth(mac_addr, rt->rt_local_src);

  	do {
  		seq = read_seqbegin(&neigh->ha_lock);
  		err = dev_hard_header(skb, dev, ntohs(skb->protocol),
  				      neigh->ha, mac_addr, skb->len);
  	} while (read_seqretry(&neigh->ha_lock, seq));
  
  	if (err >= 0)
  		err = dev_queue_xmit(skb);
  	else {
  		kfree_skb(skb);
  		err = -EINVAL;
  	}
  	return err;

  }

  static int dn_neigh_output_packet(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 neighbour *neigh = rt->n;
  
  	return neigh->output(neigh, skb);
  }
  
  /*
   * For talking to broadcast devices: Ethernet & PPP
   */

  static int dn_long_output(struct neighbour *neigh, struct sock *sk,
  			  struct sk_buff *skb)

  {

  	struct net_device *dev = neigh->dev;
  	int headroom = dev->hard_header_len + sizeof(struct dn_long_packet) + 3;
  	unsigned char *data;
  	struct dn_long_packet *lp;
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  
  
  	if (skb_headroom(skb) < headroom) {
  		struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
  		if (skb2 == NULL) {

  			net_crit_ratelimited("dn_long_output: no memory
  ");

  			kfree_skb(skb);
  			return -ENOBUFS;
  		}

  		consume_skb(skb);

  		skb = skb2;

  		net_info_ratelimited("dn_long_output: Increasing headroom
  ");

  	}
  
  	data = skb_push(skb, sizeof(struct dn_long_packet) + 3);
  	lp = (struct dn_long_packet *)(data+3);

  	*((__le16 *)data) = cpu_to_le16(skb->len - 2);

  	*(data + 2) = 1 | DN_RT_F_PF; /* Padding */
  
  	lp->msgflg   = DN_RT_PKT_LONG|(cb->rt_flags&(DN_RT_F_IE|DN_RT_F_RQR|DN_RT_F_RTS));
  	lp->d_area   = lp->d_subarea = 0;

  	dn_dn2eth(lp->d_id, cb->dst);

  	lp->s_area   = lp->s_subarea = 0;

  	dn_dn2eth(lp->s_id, cb->src);

  	lp->nl2      = 0;
  	lp->visit_ct = cb->hops & 0x3f;
  	lp->s_class  = 0;
  	lp->pt       = 0;

  	skb_reset_network_header(skb);

  	return NF_HOOK(NFPROTO_DECNET, NF_DN_POST_ROUTING,
  		       &init_net, sk, skb, NULL, neigh->dev,
  		       dn_neigh_output_packet);

  }

  /*
   * For talking to pointopoint and multidrop devices: DDCMP and X.25
   */

  static int dn_short_output(struct neighbour *neigh, struct sock *sk,
  			   struct sk_buff *skb)

  {

  	struct net_device *dev = neigh->dev;
  	int headroom = dev->hard_header_len + sizeof(struct dn_short_packet) + 2;
  	struct dn_short_packet *sp;
  	unsigned char *data;
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);

  	if (skb_headroom(skb) < headroom) {
  		struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
  		if (skb2 == NULL) {

  			net_crit_ratelimited("dn_short_output: no memory
  ");

  			kfree_skb(skb);
  			return -ENOBUFS;
  		}

  		consume_skb(skb);

  		skb = skb2;

  		net_info_ratelimited("dn_short_output: Increasing headroom
  ");

  	}

  
  	data = skb_push(skb, sizeof(struct dn_short_packet) + 2);

  	*((__le16 *)data) = cpu_to_le16(skb->len - 2);

  	sp = (struct dn_short_packet *)(data+2);
  
  	sp->msgflg     = DN_RT_PKT_SHORT|(cb->rt_flags&(DN_RT_F_RQR|DN_RT_F_RTS));
  	sp->dstnode    = cb->dst;
  	sp->srcnode    = cb->src;
  	sp->forward    = cb->hops & 0x3f;

  	skb_reset_network_header(skb);

  	return NF_HOOK(NFPROTO_DECNET, NF_DN_POST_ROUTING,
  		       &init_net, sk, skb, NULL, neigh->dev,
  		       dn_neigh_output_packet);

  }
  
  /*

   * For talking to DECnet phase III nodes
   * Phase 3 output is the same as short output, execpt that

   * it clears the area bits before transmission.
   */

  static int dn_phase3_output(struct neighbour *neigh, struct sock *sk,
  			    struct sk_buff *skb)

  {

  	struct net_device *dev = neigh->dev;
  	int headroom = dev->hard_header_len + sizeof(struct dn_short_packet) + 2;
  	struct dn_short_packet *sp;
  	unsigned char *data;
  	struct dn_skb_cb *cb = DN_SKB_CB(skb);
  
  	if (skb_headroom(skb) < headroom) {
  		struct sk_buff *skb2 = skb_realloc_headroom(skb, headroom);
  		if (skb2 == NULL) {

  			net_crit_ratelimited("dn_phase3_output: no memory
  ");

  			kfree_skb(skb);
  			return -ENOBUFS;
  		}

  		consume_skb(skb);

  		skb = skb2;

  		net_info_ratelimited("dn_phase3_output: Increasing headroom
  ");

  	}
  
  	data = skb_push(skb, sizeof(struct dn_short_packet) + 2);

  	*((__le16 *)data) = cpu_to_le16(skb->len - 2);

  	sp = (struct dn_short_packet *)(data + 2);
  
  	sp->msgflg   = DN_RT_PKT_SHORT|(cb->rt_flags&(DN_RT_F_RQR|DN_RT_F_RTS));

  	sp->dstnode  = cb->dst & cpu_to_le16(0x03ff);
  	sp->srcnode  = cb->src & cpu_to_le16(0x03ff);

  	sp->forward  = cb->hops & 0x3f;

  	skb_reset_network_header(skb);

  	return NF_HOOK(NFPROTO_DECNET, NF_DN_POST_ROUTING,
  		       &init_net, sk, skb, NULL, neigh->dev,
  		       dn_neigh_output_packet);

  }

  int dn_to_neigh_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 neighbour *neigh = rt->n;

  	struct dn_neigh *dn = container_of(neigh, struct dn_neigh, n);

  	struct dn_dev *dn_db;
  	bool use_long;
  
  	rcu_read_lock();
  	dn_db = rcu_dereference(neigh->dev->dn_ptr);
  	if (dn_db == NULL) {
  		rcu_read_unlock();
  		return -EINVAL;
  	}
  	use_long = dn_db->use_long;
  	rcu_read_unlock();
  
  	if (dn->flags & DN_NDFLAG_P3)

  		return dn_phase3_output(neigh, sk, skb);

  	if (use_long)

  		return dn_long_output(neigh, sk, skb);

  	else

  		return dn_short_output(neigh, sk, skb);

  }

  /*
   * Unfortunately, the neighbour code uses the device in its hash
   * function, so we don't get any advantage from it. This function
   * basically does a neigh_lookup(), but without comparing the device
   * field. This is required for the On-Ethernet cache
   */
  
  /*
   * Pointopoint link receives a hello message
   */
  void dn_neigh_pointopoint_hello(struct sk_buff *skb)
  {
  	kfree_skb(skb);
  }
  
  /*
   * Ethernet router hello message received
   */

  int dn_neigh_router_hello(struct net *net, struct sock *sk, struct sk_buff *skb)

  {
  	struct rtnode_hello_message *msg = (struct rtnode_hello_message *)skb->data;
  
  	struct neighbour *neigh;
  	struct dn_neigh *dn;
  	struct dn_dev *dn_db;

  	__le16 src;

  	src = dn_eth2dn(msg->id);

  
  	neigh = __neigh_lookup(&dn_neigh_table, &src, skb->dev, 1);

  	dn = container_of(neigh, struct dn_neigh, n);

  
  	if (neigh) {
  		write_lock(&neigh->lock);
  
  		neigh->used = jiffies;

  		dn_db = rcu_dereference(neigh->dev->dn_ptr);

  
  		if (!(neigh->nud_state & NUD_PERMANENT)) {
  			neigh->updated = jiffies;
  
  			if (neigh->dev->type == ARPHRD_ETHER)
  				memcpy(neigh->ha, &eth_hdr(skb)->h_source, ETH_ALEN);

  			dn->blksize  = le16_to_cpu(msg->blksize);

  			dn->priority = msg->priority;
  
  			dn->flags &= ~DN_NDFLAG_P3;

  			switch (msg->iinfo & DN_RT_INFO_TYPE) {
  			case DN_RT_INFO_L1RT:
  				dn->flags &=~DN_NDFLAG_R2;
  				dn->flags |= DN_NDFLAG_R1;
  				break;
  			case DN_RT_INFO_L2RT:
  				dn->flags |= DN_NDFLAG_R2;

  			}
  		}

  		/* Only use routers in our area */

  		if ((le16_to_cpu(src)>>10) == (le16_to_cpu((decnet_address))>>10)) {

  			if (!dn_db->router) {
  				dn_db->router = neigh_clone(neigh);
  			} else {
  				if (msg->priority > ((struct dn_neigh *)dn_db->router)->priority)
  					neigh_release(xchg(&dn_db->router, neigh_clone(neigh)));
  			}

  		}
  		write_unlock(&neigh->lock);
  		neigh_release(neigh);
  	}
  
  	kfree_skb(skb);
  	return 0;
  }
  
  /*
   * Endnode hello message received
   */

  int dn_neigh_endnode_hello(struct net *net, struct sock *sk, struct sk_buff *skb)

  {
  	struct endnode_hello_message *msg = (struct endnode_hello_message *)skb->data;
  	struct neighbour *neigh;
  	struct dn_neigh *dn;

  	__le16 src;

  	src = dn_eth2dn(msg->id);

  
  	neigh = __neigh_lookup(&dn_neigh_table, &src, skb->dev, 1);

  	dn = container_of(neigh, struct dn_neigh, n);

  
  	if (neigh) {
  		write_lock(&neigh->lock);
  
  		neigh->used = jiffies;
  
  		if (!(neigh->nud_state & NUD_PERMANENT)) {
  			neigh->updated = jiffies;
  
  			if (neigh->dev->type == ARPHRD_ETHER)
  				memcpy(neigh->ha, &eth_hdr(skb)->h_source, ETH_ALEN);
  			dn->flags   &= ~(DN_NDFLAG_R1 | DN_NDFLAG_R2);

  			dn->blksize  = le16_to_cpu(msg->blksize);

  			dn->priority = 0;
  		}
  
  		write_unlock(&neigh->lock);
  		neigh_release(neigh);
  	}
  
  	kfree_skb(skb);
  	return 0;
  }
  
  static char *dn_find_slot(char *base, int max, int priority)
  {
  	int i;
  	unsigned char *min = NULL;
  
  	base += 6; /* skip first id */
  
  	for(i = 0; i < max; i++) {
  		if (!min || (*base < *min))
  			min = base;
  		base += 7; /* find next priority */
  	}
  
  	if (!min)
  		return NULL;
  
  	return (*min < priority) ? (min - 6) : NULL;
  }
  
  struct elist_cb_state {
  	struct net_device *dev;
  	unsigned char *ptr;
  	unsigned char *rs;
  	int t, n;
  };
  
  static void neigh_elist_cb(struct neighbour *neigh, void *_info)
  {
  	struct elist_cb_state *s = _info;

  	struct dn_neigh *dn;
  
  	if (neigh->dev != s->dev)
  		return;

  	dn = container_of(neigh, struct dn_neigh, n);

  	if (!(dn->flags & (DN_NDFLAG_R1|DN_NDFLAG_R2)))
  		return;

  	if (s->t == s->n)
  		s->rs = dn_find_slot(s->ptr, s->n, dn->priority);
  	else
  		s->t++;
  	if (s->rs == NULL)
  		return;
  
  	dn_dn2eth(s->rs, dn->addr);
  	s->rs += 6;
  	*(s->rs) = neigh->nud_state & NUD_CONNECTED ? 0x80 : 0x0;
  	*(s->rs) |= dn->priority;
  	s->rs++;
  }
  
  int dn_neigh_elist(struct net_device *dev, unsigned char *ptr, int n)
  {
  	struct elist_cb_state state;
  
  	state.dev = dev;
  	state.t = 0;
  	state.n = n;
  	state.ptr = ptr;
  	state.rs = ptr;
  
  	neigh_for_each(&dn_neigh_table, neigh_elist_cb, &state);
  
  	return state.t;
  }
  
  
  #ifdef CONFIG_PROC_FS
  
  static inline void dn_neigh_format_entry(struct seq_file *seq,
  					 struct neighbour *n)
  {

  	struct dn_neigh *dn = container_of(n, struct dn_neigh, n);

  	char buf[DN_ASCBUF_LEN];
  
  	read_lock(&n->lock);
  	seq_printf(seq, "%-7s %s%s%s   %02x    %02d  %07ld %-8s
  ",

  		   dn_addr2asc(le16_to_cpu(dn->addr), buf),

  		   (dn->flags&DN_NDFLAG_R1) ? "1" : "-",
  		   (dn->flags&DN_NDFLAG_R2) ? "2" : "-",
  		   (dn->flags&DN_NDFLAG_P3) ? "3" : "-",
  		   dn->n.nud_state,

  		   refcount_read(&dn->n.refcnt),

  		   dn->blksize,
  		   (dn->n.dev) ? dn->n.dev->name : "?");
  	read_unlock(&n->lock);
  }
  
  static int dn_neigh_seq_show(struct seq_file *seq, void *v)
  {
  	if (v == SEQ_START_TOKEN) {
  		seq_puts(seq, "Addr    Flags State Use Blksize Dev
  ");
  	} else {
  		dn_neigh_format_entry(seq, v);
  	}
  
  	return 0;
  }
  
  static void *dn_neigh_seq_start(struct seq_file *seq, loff_t *pos)
  {
  	return neigh_seq_start(seq, pos, &dn_neigh_table,
  			       NEIGH_SEQ_NEIGH_ONLY);
  }

  static const struct seq_operations dn_neigh_seq_ops = {

  	.start = dn_neigh_seq_start,
  	.next  = neigh_seq_next,
  	.stop  = neigh_seq_stop,
  	.show  = dn_neigh_seq_show,
  };

  #endif
  
  void __init dn_neigh_init(void)
  {

  	neigh_table_init(NEIGH_DN_TABLE, &dn_neigh_table);

  	proc_create_net("decnet_neigh", 0444, init_net.proc_net,
  			&dn_neigh_seq_ops, sizeof(struct neigh_seq_state));

  }
  
  void __exit dn_neigh_cleanup(void)
  {

  	remove_proc_entry("decnet_neigh", init_net.proc_net);

  	neigh_table_clear(NEIGH_DN_TABLE, &dn_neigh_table);

  }