/* Copyright 2011-2013 Autronica Fire and Security AS
   *
   * 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 (at your option)
   * any later version.
   *
   * Author(s):
   *	2011-2013 Arvid Brodin, arvid.brodin@xdin.com
   *
   * The HSR spec says never to forward the same frame twice on the same
   * interface. A frame is identified by its source MAC address and its HSR
   * sequence number. This code keeps track of senders and their sequence numbers
   * to allow filtering of duplicate frames, and to detect HSR ring errors.
   */
  
  #include <linux/if_ether.h>
  #include <linux/etherdevice.h>
  #include <linux/slab.h>
  #include <linux/rculist.h>
  #include "hsr_main.h"
  #include "hsr_framereg.h"
  #include "hsr_netlink.h"
  
  
  struct node_entry {
  	struct list_head mac_list;
  	unsigned char	MacAddressA[ETH_ALEN];
  	unsigned char	MacAddressB[ETH_ALEN];
  	enum hsr_dev_idx   AddrB_if;	/* The local slave through which AddrB
  					 * frames are received from this node
  					 */
  	unsigned long	time_in[HSR_MAX_SLAVE];
  	bool		time_in_stale[HSR_MAX_SLAVE];
  	u16		seq_out[HSR_MAX_DEV];
  	struct rcu_head rcu_head;
  };
  
  /*	TODO: use hash lists for mac addresses (linux/jhash.h)?    */
  
  
  
  /* Search for mac entry. Caller must hold rcu read lock.
   */
  static struct node_entry *find_node_by_AddrA(struct list_head *node_db,
  					     const unsigned char addr[ETH_ALEN])
  {
  	struct node_entry *node;
  
  	list_for_each_entry_rcu(node, node_db, mac_list) {
  		if (ether_addr_equal(node->MacAddressA, addr))
  			return node;
  	}
  
  	return NULL;
  }
  
  
  /* Search for mac entry. Caller must hold rcu read lock.
   */
  static struct node_entry *find_node_by_AddrB(struct list_head *node_db,
  					     const unsigned char addr[ETH_ALEN])
  {
  	struct node_entry *node;
  
  	list_for_each_entry_rcu(node, node_db, mac_list) {
  		if (ether_addr_equal(node->MacAddressB, addr))
  			return node;
  	}
  
  	return NULL;
  }
  
  
  /* Search for mac entry. Caller must hold rcu read lock.
   */
  struct node_entry *hsr_find_node(struct list_head *node_db, struct sk_buff *skb)
  {
  	struct node_entry *node;
  	struct ethhdr *ethhdr;
  
  	if (!skb_mac_header_was_set(skb))
  		return NULL;
  
  	ethhdr = (struct ethhdr *) skb_mac_header(skb);
  
  	list_for_each_entry_rcu(node, node_db, mac_list) {
  		if (ether_addr_equal(node->MacAddressA, ethhdr->h_source))
  			return node;
  		if (ether_addr_equal(node->MacAddressB, ethhdr->h_source))
  			return node;
  	}
  
  	return NULL;
  }
  
  
  /* Helper for device init; the self_node_db is used in hsr_rcv() to recognize
   * frames from self that's been looped over the HSR ring.
   */
  int hsr_create_self_node(struct list_head *self_node_db,
  			 unsigned char addr_a[ETH_ALEN],
  			 unsigned char addr_b[ETH_ALEN])
  {
  	struct node_entry *node, *oldnode;
  
  	node = kmalloc(sizeof(*node), GFP_KERNEL);
  	if (!node)
  		return -ENOMEM;
  
  	memcpy(node->MacAddressA, addr_a, ETH_ALEN);
  	memcpy(node->MacAddressB, addr_b, ETH_ALEN);
  
  	rcu_read_lock();
  	oldnode = list_first_or_null_rcu(self_node_db,
  						struct node_entry, mac_list);
  	if (oldnode) {
  		list_replace_rcu(&oldnode->mac_list, &node->mac_list);
  		rcu_read_unlock();
  		synchronize_rcu();
  		kfree(oldnode);
  	} else {
  		rcu_read_unlock();
  		list_add_tail_rcu(&node->mac_list, self_node_db);
  	}
  
  	return 0;
  }
  
  
  /* Add/merge node to the database of nodes. 'skb' must contain an HSR
   * supervision frame.
   * - If the supervision header's MacAddressA field is not yet in the database,
   * this frame is from an hitherto unknown node - add it to the database.
   * - If the sender's MAC address is not the same as its MacAddressA address,
   * the node is using PICS_SUBS (address substitution). Record the sender's
   * address as the node's MacAddressB.
   *
   * This function needs to work even if the sender node has changed one of its
   * slaves' MAC addresses. In this case, there are four different cases described
   * by (Addr-changed, received-from) pairs as follows. Note that changing the
   * SlaveA address is equal to changing the node's own address:
   *
   * - (AddrB, SlaveB): The new AddrB will be recorded by PICS_SUBS code since
   *		      node == NULL.
   * - (AddrB, SlaveA): Will work as usual (the AddrB change won't be detected
   *		      from this frame).
   *
   * - (AddrA, SlaveB): The old node will be found. We need to detect this and
   *		      remove the node.
   * - (AddrA, SlaveA): A new node will be registered (non-PICS_SUBS at first).
   *		      The old one will be pruned after HSR_NODE_FORGET_TIME.
   *
   * We also need to detect if the sender's SlaveA and SlaveB cables have been
   * swapped.
   */
  struct node_entry *hsr_merge_node(struct hsr_priv *hsr_priv,
  				  struct node_entry *node,
  				  struct sk_buff *skb,
  				  enum hsr_dev_idx dev_idx)
  {
  	struct hsr_sup_payload *hsr_sp;
  	struct hsr_ethhdr_sp *hsr_ethsup;
  	int i;
  	unsigned long now;
  
  	hsr_ethsup = (struct hsr_ethhdr_sp *) skb_mac_header(skb);
  	hsr_sp = (struct hsr_sup_payload *) skb->data;
  
  	if (node && !ether_addr_equal(node->MacAddressA, hsr_sp->MacAddressA)) {
  		/* Node has changed its AddrA, frame was received from SlaveB */
  		list_del_rcu(&node->mac_list);
  		kfree_rcu(node, rcu_head);
  		node = NULL;
  	}
  
  	if (node && (dev_idx == node->AddrB_if) &&
  	    !ether_addr_equal(node->MacAddressB, hsr_ethsup->ethhdr.h_source)) {
  		/* Cables have been swapped */
  		list_del_rcu(&node->mac_list);
  		kfree_rcu(node, rcu_head);
  		node = NULL;
  	}
  
  	if (node && (dev_idx != node->AddrB_if) &&
  	    (node->AddrB_if != HSR_DEV_NONE) &&
  	    !ether_addr_equal(node->MacAddressA, hsr_ethsup->ethhdr.h_source)) {
  		/* Cables have been swapped */
  		list_del_rcu(&node->mac_list);
  		kfree_rcu(node, rcu_head);
  		node = NULL;
  	}
  
  	if (node)
  		return node;
  
  	node = find_node_by_AddrA(&hsr_priv->node_db, hsr_sp->MacAddressA);
  	if (node) {
  		/* Node is known, but frame was received from an unknown
  		 * address. Node is PICS_SUBS capable; merge its AddrB.
  		 */
  		memcpy(node->MacAddressB, hsr_ethsup->ethhdr.h_source, ETH_ALEN);
  		node->AddrB_if = dev_idx;
  		return node;
  	}
  
  	node = kzalloc(sizeof(*node), GFP_ATOMIC);
  	if (!node)
  		return NULL;
  
  	memcpy(node->MacAddressA, hsr_sp->MacAddressA, ETH_ALEN);
  	memcpy(node->MacAddressB, hsr_ethsup->ethhdr.h_source, ETH_ALEN);
  	if (!ether_addr_equal(hsr_sp->MacAddressA, hsr_ethsup->ethhdr.h_source))
  		node->AddrB_if = dev_idx;
  	else
  		node->AddrB_if = HSR_DEV_NONE;
  
  	/* We are only interested in time diffs here, so use current jiffies
  	 * as initialization. (0 could trigger an spurious ring error warning).
  	 */
  	now = jiffies;
  	for (i = 0; i < HSR_MAX_SLAVE; i++)
  		node->time_in[i] = now;
  	for (i = 0; i < HSR_MAX_DEV; i++)
  		node->seq_out[i] = ntohs(hsr_ethsup->hsr_sup.sequence_nr) - 1;
  
  	list_add_tail_rcu(&node->mac_list, &hsr_priv->node_db);
  
  	return node;
  }
  
  
  /* 'skb' is a frame meant for this host, that is to be passed to upper layers.
   *
   * If the frame was sent by a node's B interface, replace the sender
   * address with that node's "official" address (MacAddressA) so that upper
   * layers recognize where it came from.
   */
  void hsr_addr_subst_source(struct hsr_priv *hsr_priv, struct sk_buff *skb)
  {
  	struct ethhdr *ethhdr;
  	struct node_entry *node;
  
  	if (!skb_mac_header_was_set(skb)) {
  		WARN_ONCE(1, "%s: Mac header not set
  ", __func__);
  		return;
  	}
  	ethhdr = (struct ethhdr *) skb_mac_header(skb);
  
  	rcu_read_lock();
  	node = find_node_by_AddrB(&hsr_priv->node_db, ethhdr->h_source);
  	if (node)
  		memcpy(ethhdr->h_source, node->MacAddressA, ETH_ALEN);
  	rcu_read_unlock();
  }
  
  
  /* 'skb' is a frame meant for another host.
   * 'hsr_dev_idx' is the HSR index of the outgoing device
   *
   * Substitute the target (dest) MAC address if necessary, so the it matches the
   * recipient interface MAC address, regardless of whether that is the
   * recipient's A or B interface.
   * This is needed to keep the packets flowing through switches that learn on
   * which "side" the different interfaces are.
   */
  void hsr_addr_subst_dest(struct hsr_priv *hsr_priv, struct ethhdr *ethhdr,
  			 enum hsr_dev_idx dev_idx)
  {
  	struct node_entry *node;
  
  	rcu_read_lock();
  	node = find_node_by_AddrA(&hsr_priv->node_db, ethhdr->h_dest);
  	if (node && (node->AddrB_if == dev_idx))
  		memcpy(ethhdr->h_dest, node->MacAddressB, ETH_ALEN);
  	rcu_read_unlock();
  }
  
  
  /* seq_nr_after(a, b) - return true if a is after (higher in sequence than) b,
   * false otherwise.
   */
  static bool seq_nr_after(u16 a, u16 b)
  {
  	/* Remove inconsistency where
  	 * seq_nr_after(a, b) == seq_nr_before(a, b)
  	 */
  	if ((int) b - a == 32768)
  		return false;
  
  	return (((s16) (b - a)) < 0);
  }
  #define seq_nr_before(a, b)		seq_nr_after((b), (a))
  #define seq_nr_after_or_eq(a, b)	(!seq_nr_before((a), (b)))
  #define seq_nr_before_or_eq(a, b)	(!seq_nr_after((a), (b)))
  
  
  void hsr_register_frame_in(struct node_entry *node, enum hsr_dev_idx dev_idx)
  {
  	if ((dev_idx < 0) || (dev_idx >= HSR_MAX_SLAVE)) {
  		WARN_ONCE(1, "%s: Invalid dev_idx (%d)
  ", __func__, dev_idx);
  		return;
  	}
  	node->time_in[dev_idx] = jiffies;
  	node->time_in_stale[dev_idx] = false;
  }
  
  
  /* 'skb' is a HSR Ethernet frame (with a HSR tag inserted), with a valid
   * ethhdr->h_source address and skb->mac_header set.
   *
   * Return:
   *	 1 if frame can be shown to have been sent recently on this interface,
   *	 0 otherwise, or
   *	 negative error code on error
   */
  int hsr_register_frame_out(struct node_entry *node, enum hsr_dev_idx dev_idx,
  			   struct sk_buff *skb)
  {
  	struct hsr_ethhdr *hsr_ethhdr;
  	u16 sequence_nr;
  
  	if ((dev_idx < 0) || (dev_idx >= HSR_MAX_DEV)) {
  		WARN_ONCE(1, "%s: Invalid dev_idx (%d)
  ", __func__, dev_idx);
  		return -EINVAL;
  	}
  	if (!skb_mac_header_was_set(skb)) {
  		WARN_ONCE(1, "%s: Mac header not set
  ", __func__);
  		return -EINVAL;
  	}
  	hsr_ethhdr = (struct hsr_ethhdr *) skb_mac_header(skb);
  
  	sequence_nr = ntohs(hsr_ethhdr->hsr_tag.sequence_nr);
  	if (seq_nr_before_or_eq(sequence_nr, node->seq_out[dev_idx]))
  		return 1;
  
  	node->seq_out[dev_idx] = sequence_nr;
  	return 0;
  }
  
  
  
  static bool is_late(struct node_entry *node, enum hsr_dev_idx dev_idx)
  {
  	enum hsr_dev_idx other;
  
  	if (node->time_in_stale[dev_idx])
  		return true;
  
  	if (dev_idx == HSR_DEV_SLAVE_A)
  		other = HSR_DEV_SLAVE_B;
  	else
  		other = HSR_DEV_SLAVE_A;
  
  	if (node->time_in_stale[other])
  		return false;
  
  	if (time_after(node->time_in[other], node->time_in[dev_idx] +
  		       msecs_to_jiffies(MAX_SLAVE_DIFF)))
  		return true;
  
  	return false;
  }
  
  
  /* Remove stale sequence_nr records. Called by timer every
   * HSR_LIFE_CHECK_INTERVAL (two seconds or so).
   */
  void hsr_prune_nodes(struct hsr_priv *hsr_priv)
  {
  	struct node_entry *node;
  	unsigned long timestamp;
  	unsigned long time_a, time_b;
  
  	rcu_read_lock();
  	list_for_each_entry_rcu(node, &hsr_priv->node_db, mac_list) {
  		/* Shorthand */
  		time_a = node->time_in[HSR_DEV_SLAVE_A];
  		time_b = node->time_in[HSR_DEV_SLAVE_B];
  
  		/* Check for timestamps old enough to risk wrap-around */
  		if (time_after(jiffies, time_a + MAX_JIFFY_OFFSET/2))
  			node->time_in_stale[HSR_DEV_SLAVE_A] = true;
  		if (time_after(jiffies, time_b + MAX_JIFFY_OFFSET/2))
  			node->time_in_stale[HSR_DEV_SLAVE_B] = true;
  
  		/* Get age of newest frame from node.
  		 * At least one time_in is OK here; nodes get pruned long
  		 * before both time_ins can get stale
  		 */
  		timestamp = time_a;
  		if (node->time_in_stale[HSR_DEV_SLAVE_A] ||
  		    (!node->time_in_stale[HSR_DEV_SLAVE_B] &&
  		    time_after(time_b, time_a)))
  			timestamp = time_b;
  
  		/* Warn of ring error only as long as we get frames at all */
  		if (time_is_after_jiffies(timestamp +
  					msecs_to_jiffies(1.5*MAX_SLAVE_DIFF))) {
  
  			if (is_late(node, HSR_DEV_SLAVE_A))
  				hsr_nl_ringerror(hsr_priv, node->MacAddressA,
  						 HSR_DEV_SLAVE_A);
  			else if (is_late(node, HSR_DEV_SLAVE_B))
  				hsr_nl_ringerror(hsr_priv, node->MacAddressA,
  						 HSR_DEV_SLAVE_B);
  		}
  
  		/* Prune old entries */
  		if (time_is_before_jiffies(timestamp +
  					msecs_to_jiffies(HSR_NODE_FORGET_TIME))) {
  			hsr_nl_nodedown(hsr_priv, node->MacAddressA);
  			list_del_rcu(&node->mac_list);
  			/* Note that we need to free this entry later: */
  			kfree_rcu(node, rcu_head);
  		}
  	}
  	rcu_read_unlock();
  }
  
  
  void *hsr_get_next_node(struct hsr_priv *hsr_priv, void *_pos,
  			unsigned char addr[ETH_ALEN])
  {
  	struct node_entry *node;
  
  	if (!_pos) {
  		node = list_first_or_null_rcu(&hsr_priv->node_db,
  						struct node_entry, mac_list);
  		if (node)
  			memcpy(addr, node->MacAddressA, ETH_ALEN);
  		return node;
  	}
  
  	node = _pos;
  	list_for_each_entry_continue_rcu(node, &hsr_priv->node_db, mac_list) {
  		memcpy(addr, node->MacAddressA, ETH_ALEN);
  		return node;
  	}
  
  	return NULL;
  }
  
  
  int hsr_get_node_data(struct hsr_priv *hsr_priv,
  		      const unsigned char *addr,
  		      unsigned char addr_b[ETH_ALEN],
  		      unsigned int *addr_b_ifindex,
  		      int *if1_age,
  		      u16 *if1_seq,
  		      int *if2_age,
  		      u16 *if2_seq)
  {
  	struct node_entry *node;
  	unsigned long tdiff;
  
  
  	rcu_read_lock();
  	node = find_node_by_AddrA(&hsr_priv->node_db, addr);
  	if (!node) {
  		rcu_read_unlock();
  		return -ENOENT;	/* No such entry */
  	}
  
  	memcpy(addr_b, node->MacAddressB, ETH_ALEN);
  
  	tdiff = jiffies - node->time_in[HSR_DEV_SLAVE_A];
  	if (node->time_in_stale[HSR_DEV_SLAVE_A])
  		*if1_age = INT_MAX;
  #if HZ <= MSEC_PER_SEC
  	else if (tdiff > msecs_to_jiffies(INT_MAX))
  		*if1_age = INT_MAX;
  #endif
  	else
  		*if1_age = jiffies_to_msecs(tdiff);
  
  	tdiff = jiffies - node->time_in[HSR_DEV_SLAVE_B];
  	if (node->time_in_stale[HSR_DEV_SLAVE_B])
  		*if2_age = INT_MAX;
  #if HZ <= MSEC_PER_SEC
  	else if (tdiff > msecs_to_jiffies(INT_MAX))
  		*if2_age = INT_MAX;
  #endif
  	else
  		*if2_age = jiffies_to_msecs(tdiff);
  
  	/* Present sequence numbers as if they were incoming on interface */
  	*if1_seq = node->seq_out[HSR_DEV_SLAVE_B];
  	*if2_seq = node->seq_out[HSR_DEV_SLAVE_A];
  
  	if ((node->AddrB_if != HSR_DEV_NONE) && hsr_priv->slave[node->AddrB_if])
  		*addr_b_ifindex = hsr_priv->slave[node->AddrB_if]->ifindex;
  	else
  		*addr_b_ifindex = -1;
  
  	rcu_read_unlock();
  
  	return 0;
  }