net/hsr/hsr_framereg.c - arm/linux-arm-legacy - Git at Google

 /* 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\n", __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)\n", __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)\n", __func__, dev_idx);
 		return -EINVAL;
 	}
 	if (!skb_mac_header_was_set(skb)) {
 		WARN_ONCE(1, "%s: Mac header not set\n", __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;
 }
	/* 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\n", __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)\n", __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)\n", __func__, dev_idx);
	return -EINVAL;
	}
	if (!skb_mac_header_was_set(skb)) {
	WARN_ONCE(1, "%s: Mac header not set\n", __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;
	}