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

 // SPDX-License-Identifier: GPL-2.0
 /* Copyright 2011-2014 Autronica Fire and Security AS
  *
  * Author(s):
  *	2011-2014 Arvid Brodin, arvid.brodin@alten.se
  *
  * 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"

 /*	TODO: use hash lists for mac addresses (linux/jhash.h)?    */

 /* 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)))

 bool hsr_addr_is_self(struct hsr_priv *hsr, unsigned char *addr)
 {
 	struct hsr_node *node;

 	node = list_first_or_null_rcu(&hsr->self_node_db, struct hsr_node,
 				      mac_list);
 	if (!node) {
 		WARN_ONCE(1, "HSR: No self node\n");
 		return false;
 	}

 	if (ether_addr_equal(addr, node->macaddress_A))
 		return true;
 	if (ether_addr_equal(addr, node->macaddress_B))
 		return true;

 	return false;
 }

 /* Search for mac entry. Caller must hold rcu read lock.
  */
 static struct hsr_node *find_node_by_addr_A(struct list_head *node_db,
 					    const unsigned char addr[ETH_ALEN])
 {
 	struct hsr_node *node;

 	list_for_each_entry_rcu(node, node_db, mac_list) {
 		if (ether_addr_equal(node->macaddress_A, addr))
 			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 hsr_node *node, *oldnode;

 	node = kmalloc(sizeof(*node), GFP_KERNEL);
 	if (!node)
 		return -ENOMEM;

 	ether_addr_copy(node->macaddress_A, addr_a);
 	ether_addr_copy(node->macaddress_B, addr_b);

 	rcu_read_lock();
 	oldnode = list_first_or_null_rcu(self_node_db,
 					 struct hsr_node, 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;
 }

 void hsr_del_self_node(struct list_head *self_node_db)
 {
 	struct hsr_node *node;

 	rcu_read_lock();
 	node = list_first_or_null_rcu(self_node_db, struct hsr_node, mac_list);
 	rcu_read_unlock();
 	if (node) {
 		list_del_rcu(&node->mac_list);
 		kfree(node);
 	}
 }

 void hsr_del_nodes(struct list_head *node_db)
 {
 	struct hsr_node *node;
 	struct hsr_node *tmp;

 	list_for_each_entry_safe(node, tmp, node_db, mac_list)
 		kfree(node);
 }

 /* Allocate an hsr_node and add it to node_db. 'addr' is the node's address_A;
  * seq_out is used to initialize filtering of outgoing duplicate frames
  * originating from the newly added node.
  */
 struct hsr_node *hsr_add_node(struct list_head *node_db, unsigned char addr[],
 			      u16 seq_out)
 {
 	struct hsr_node *node;
 	unsigned long now;
 	int i;

 	node = kzalloc(sizeof(*node), GFP_ATOMIC);
 	if (!node)
 		return NULL;

 	ether_addr_copy(node->macaddress_A, addr);

 	/* 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_PT_PORTS; i++)
 		node->time_in[i] = now;
 	for (i = 0; i < HSR_PT_PORTS; i++)
 		node->seq_out[i] = seq_out;

 	list_add_tail_rcu(&node->mac_list, node_db);

 	return node;
 }

 /* Get the hsr_node from which 'skb' was sent.
  */
 struct hsr_node *hsr_get_node(struct hsr_port *port, struct sk_buff *skb,
 			      bool is_sup)
 {
 	struct list_head *node_db = &port->hsr->node_db;
 	struct hsr_node *node;
 	struct ethhdr *ethhdr;
 	u16 seq_out;

 	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->macaddress_A, ethhdr->h_source))
 			return node;
 		if (ether_addr_equal(node->macaddress_B, ethhdr->h_source))
 			return node;
 	}

 	/* Everyone may create a node entry, connected node to a HSR device. */

 	if (ethhdr->h_proto == htons(ETH_P_PRP) ||
 	    ethhdr->h_proto == htons(ETH_P_HSR)) {
 		/* Use the existing sequence_nr from the tag as starting point
 		 * for filtering duplicate frames.
 		 */
 		seq_out = hsr_get_skb_sequence_nr(skb) - 1;
 	} else {
 		/* this is called also for frames from master port and
 		 * so warn only for non master ports
 		 */
 		if (port->type != HSR_PT_MASTER)
 			WARN_ONCE(1, "%s: Non-HSR frame\n", __func__);
 		seq_out = HSR_SEQNR_START;
 	}

 	return hsr_add_node(node_db, ethhdr->h_source, seq_out);
 }

 /* Use the Supervision frame's info about an eventual macaddress_B for merging
  * nodes that has previously had their macaddress_B registered as a separate
  * node.
  */
 void hsr_handle_sup_frame(struct sk_buff *skb, struct hsr_node *node_curr,
 			  struct hsr_port *port_rcv)
 {
 	struct ethhdr *ethhdr;
 	struct hsr_node *node_real;
 	struct hsr_sup_payload *hsr_sp;
 	struct list_head *node_db;
 	int i;

 	ethhdr = (struct ethhdr *)skb_mac_header(skb);

 	/* Leave the ethernet header. */
 	skb_pull(skb, sizeof(struct ethhdr));

 	/* And leave the HSR tag. */
 	if (ethhdr->h_proto == htons(ETH_P_HSR))
 		skb_pull(skb, sizeof(struct hsr_tag));

 	/* And leave the HSR sup tag. */
 	skb_pull(skb, sizeof(struct hsr_sup_tag));

 	hsr_sp = (struct hsr_sup_payload *)skb->data;

 	/* Merge node_curr (registered on macaddress_B) into node_real */
 	node_db = &port_rcv->hsr->node_db;
 	node_real = find_node_by_addr_A(node_db, hsr_sp->macaddress_A);
 	if (!node_real)
 		/* No frame received from AddrA of this node yet */
 		node_real = hsr_add_node(node_db, hsr_sp->macaddress_A,
 					 HSR_SEQNR_START - 1);
 	if (!node_real)
 		goto done; /* No mem */
 	if (node_real == node_curr)
 		/* Node has already been merged */
 		goto done;

 	ether_addr_copy(node_real->macaddress_B, ethhdr->h_source);
 	for (i = 0; i < HSR_PT_PORTS; i++) {
 		if (!node_curr->time_in_stale[i] &&
 		    time_after(node_curr->time_in[i], node_real->time_in[i])) {
 			node_real->time_in[i] = node_curr->time_in[i];
 			node_real->time_in_stale[i] =
 						node_curr->time_in_stale[i];
 		}
 		if (seq_nr_after(node_curr->seq_out[i], node_real->seq_out[i]))
 			node_real->seq_out[i] = node_curr->seq_out[i];
 	}
 	node_real->addr_B_port = port_rcv->type;

 	list_del_rcu(&node_curr->mac_list);
 	kfree_rcu(node_curr, rcu_head);

 done:
 	skb_push(skb, sizeof(struct hsrv1_ethhdr_sp));
 }

 /* '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 source
  * address with that node's "official" address (macaddress_A) so that upper
  * layers recognize where it came from.
  */
 void hsr_addr_subst_source(struct hsr_node *node, struct sk_buff *skb)
 {
 	if (!skb_mac_header_was_set(skb)) {
 		WARN_ONCE(1, "%s: Mac header not set\n", __func__);
 		return;
 	}

 	memcpy(&eth_hdr(skb)->h_source, node->macaddress_A, ETH_ALEN);
 }

 /* 'skb' is a frame meant for another host.
  * 'port' is the outgoing interface
  *
  * 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_node *node_src, struct sk_buff *skb,
 			 struct hsr_port *port)
 {
 	struct hsr_node *node_dst;

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

 	if (!is_unicast_ether_addr(eth_hdr(skb)->h_dest))
 		return;

 	node_dst = find_node_by_addr_A(&port->hsr->node_db,
 				       eth_hdr(skb)->h_dest);
 	if (!node_dst) {
 		WARN_ONCE(1, "%s: Unknown node\n", __func__);
 		return;
 	}
 	if (port->type != node_dst->addr_B_port)
 		return;

 	ether_addr_copy(eth_hdr(skb)->h_dest, node_dst->macaddress_B);
 }

 void hsr_register_frame_in(struct hsr_node *node, struct hsr_port *port,
 			   u16 sequence_nr)
 {
 	/* Don't register incoming frames without a valid sequence number. This
 	 * ensures entries of restarted nodes gets pruned so that they can
 	 * re-register and resume communications.
 	 */
 	if (seq_nr_before(sequence_nr, node->seq_out[port->type]))
 		return;

 	node->time_in[port->type] = jiffies;
 	node->time_in_stale[port->type] = 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 hsr_port *port, struct hsr_node *node,
 			   u16 sequence_nr)
 {
 	if (seq_nr_before_or_eq(sequence_nr, node->seq_out[port->type]))
 		return 1;

 	node->seq_out[port->type] = sequence_nr;
 	return 0;
 }

 static struct hsr_port *get_late_port(struct hsr_priv *hsr,
 				      struct hsr_node *node)
 {
 	if (node->time_in_stale[HSR_PT_SLAVE_A])
 		return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_A);
 	if (node->time_in_stale[HSR_PT_SLAVE_B])
 		return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_B);

 	if (time_after(node->time_in[HSR_PT_SLAVE_B],
 		       node->time_in[HSR_PT_SLAVE_A] +
 					msecs_to_jiffies(MAX_SLAVE_DIFF)))
 		return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_A);
 	if (time_after(node->time_in[HSR_PT_SLAVE_A],
 		       node->time_in[HSR_PT_SLAVE_B] +
 					msecs_to_jiffies(MAX_SLAVE_DIFF)))
 		return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_B);

 	return NULL;
 }

 /* Remove stale sequence_nr records. Called by timer every
  * HSR_LIFE_CHECK_INTERVAL (two seconds or so).
  */
 void hsr_prune_nodes(struct timer_list *t)
 {
 	struct hsr_priv *hsr = from_timer(hsr, t, prune_timer);
 	struct hsr_node *node;
 	struct hsr_port *port;
 	unsigned long timestamp;
 	unsigned long time_a, time_b;

 	rcu_read_lock();
 	list_for_each_entry_rcu(node, &hsr->node_db, mac_list) {
 		/* Don't prune own node. Neither time_in[HSR_PT_SLAVE_A]
 		 * nor time_in[HSR_PT_SLAVE_B], will ever be updated for
 		 * the master port. Thus the master node will be repeatedly
 		 * pruned leading to packet loss.
 		 */
 		if (hsr_addr_is_self(hsr, node->macaddress_A))
 			continue;

 		/* Shorthand */
 		time_a = node->time_in[HSR_PT_SLAVE_A];
 		time_b = node->time_in[HSR_PT_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_PT_SLAVE_A] = true;
 		if (time_after(jiffies, time_b + MAX_JIFFY_OFFSET / 2))
 			node->time_in_stale[HSR_PT_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_PT_SLAVE_A] ||
 		    (!node->time_in_stale[HSR_PT_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))) {
 			rcu_read_lock();
 			port = get_late_port(hsr, node);
 			if (port)
 				hsr_nl_ringerror(hsr, node->macaddress_A, port);
 			rcu_read_unlock();
 		}

 		/* Prune old entries */
 		if (time_is_before_jiffies(timestamp +
 				msecs_to_jiffies(HSR_NODE_FORGET_TIME))) {
 			hsr_nl_nodedown(hsr, node->macaddress_A);
 			list_del_rcu(&node->mac_list);
 			/* Note that we need to free this entry later: */
 			kfree_rcu(node, rcu_head);
 		}
 	}
 	rcu_read_unlock();

 	/* Restart timer */
 	mod_timer(&hsr->prune_timer,
 		  jiffies + msecs_to_jiffies(PRUNE_PERIOD));
 }

 void *hsr_get_next_node(struct hsr_priv *hsr, void *_pos,
 			unsigned char addr[ETH_ALEN])
 {
 	struct hsr_node *node;

 	if (!_pos) {
 		node = list_first_or_null_rcu(&hsr->node_db,
 					      struct hsr_node, mac_list);
 		if (node)
 			ether_addr_copy(addr, node->macaddress_A);
 		return node;
 	}

 	node = _pos;
 	list_for_each_entry_continue_rcu(node, &hsr->node_db, mac_list) {
 		ether_addr_copy(addr, node->macaddress_A);
 		return node;
 	}

 	return NULL;
 }

 int hsr_get_node_data(struct hsr_priv *hsr,
 		      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 hsr_node *node;
 	struct hsr_port *port;
 	unsigned long tdiff;

 	rcu_read_lock();
 	node = find_node_by_addr_A(&hsr->node_db, addr);
 	if (!node) {
 		rcu_read_unlock();
 		return -ENOENT;	/* No such entry */
 	}

 	ether_addr_copy(addr_b, node->macaddress_B);

 	tdiff = jiffies - node->time_in[HSR_PT_SLAVE_A];
 	if (node->time_in_stale[HSR_PT_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_PT_SLAVE_B];
 	if (node->time_in_stale[HSR_PT_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_PT_SLAVE_B];
 	*if2_seq = node->seq_out[HSR_PT_SLAVE_A];

 	if (node->addr_B_port != HSR_PT_NONE) {
 		port = hsr_port_get_hsr(hsr, node->addr_B_port);
 		*addr_b_ifindex = port->dev->ifindex;
 	} else {
 		*addr_b_ifindex = -1;
 	}

 	rcu_read_unlock();

 	return 0;
 }
	// SPDX-License-Identifier: GPL-2.0
	/* Copyright 2011-2014 Autronica Fire and Security AS
	*
	* Author(s):
	* 2011-2014 Arvid Brodin, arvid.brodin@alten.se
	*
	* 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"

	/* TODO: use hash lists for mac addresses (linux/jhash.h)? */

	/* 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)))

	bool hsr_addr_is_self(struct hsr_priv hsr, unsigned char addr)
	{
	struct hsr_node *node;

	node = list_first_or_null_rcu(&hsr->self_node_db, struct hsr_node,
	mac_list);
	if (!node) {
	WARN_ONCE(1, "HSR: No self node\n");
	return false;
	}

	if (ether_addr_equal(addr, node->macaddress_A))
	return true;
	if (ether_addr_equal(addr, node->macaddress_B))
	return true;

	return false;
	}

	/* Search for mac entry. Caller must hold rcu read lock.
	*/
	static struct hsr_node find_node_by_addr_A(struct list_head node_db,
	const unsigned char addr[ETH_ALEN])
	{
	struct hsr_node *node;

	list_for_each_entry_rcu(node, node_db, mac_list) {
	if (ether_addr_equal(node->macaddress_A, addr))
	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 hsr_node node, oldnode;

	node = kmalloc(sizeof(*node), GFP_KERNEL);
	if (!node)
	return -ENOMEM;

	ether_addr_copy(node->macaddress_A, addr_a);
	ether_addr_copy(node->macaddress_B, addr_b);

	rcu_read_lock();
	oldnode = list_first_or_null_rcu(self_node_db,
	struct hsr_node, 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;
	}

	void hsr_del_self_node(struct list_head *self_node_db)
	{
	struct hsr_node *node;

	rcu_read_lock();
	node = list_first_or_null_rcu(self_node_db, struct hsr_node, mac_list);
	rcu_read_unlock();
	if (node) {
	list_del_rcu(&node->mac_list);
	kfree(node);
	}
	}

	void hsr_del_nodes(struct list_head *node_db)
	{
	struct hsr_node *node;
	struct hsr_node *tmp;

	list_for_each_entry_safe(node, tmp, node_db, mac_list)
	kfree(node);
	}

	/* Allocate an hsr_node and add it to node_db. 'addr' is the node's address_A;
	* seq_out is used to initialize filtering of outgoing duplicate frames
	* originating from the newly added node.
	*/
	struct hsr_node hsr_add_node(struct list_head node_db, unsigned char addr[],
	u16 seq_out)
	{
	struct hsr_node *node;
	unsigned long now;
	int i;

	node = kzalloc(sizeof(*node), GFP_ATOMIC);
	if (!node)
	return NULL;

	ether_addr_copy(node->macaddress_A, addr);

	/* 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_PT_PORTS; i++)
	node->time_in[i] = now;
	for (i = 0; i < HSR_PT_PORTS; i++)
	node->seq_out[i] = seq_out;

	list_add_tail_rcu(&node->mac_list, node_db);

	return node;
	}

	/* Get the hsr_node from which 'skb' was sent.
	*/
	struct hsr_node hsr_get_node(struct hsr_port port, struct sk_buff *skb,
	bool is_sup)
	{
	struct list_head *node_db = &port->hsr->node_db;
	struct hsr_node *node;
	struct ethhdr *ethhdr;
	u16 seq_out;

	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->macaddress_A, ethhdr->h_source))
	return node;
	if (ether_addr_equal(node->macaddress_B, ethhdr->h_source))
	return node;
	}

	/* Everyone may create a node entry, connected node to a HSR device. */

	if (ethhdr->h_proto == htons(ETH_P_PRP) \|\|
	ethhdr->h_proto == htons(ETH_P_HSR)) {
	/* Use the existing sequence_nr from the tag as starting point
	* for filtering duplicate frames.
	*/
	seq_out = hsr_get_skb_sequence_nr(skb) - 1;
	} else {
	/* this is called also for frames from master port and
	* so warn only for non master ports
	*/
	if (port->type != HSR_PT_MASTER)
	WARN_ONCE(1, "%s: Non-HSR frame\n", __func__);
	seq_out = HSR_SEQNR_START;
	}

	return hsr_add_node(node_db, ethhdr->h_source, seq_out);
	}

	/* Use the Supervision frame's info about an eventual macaddress_B for merging
	* nodes that has previously had their macaddress_B registered as a separate
	* node.
	*/
	void hsr_handle_sup_frame(struct sk_buff skb, struct hsr_node node_curr,
	struct hsr_port *port_rcv)
	{
	struct ethhdr *ethhdr;
	struct hsr_node *node_real;
	struct hsr_sup_payload *hsr_sp;
	struct list_head *node_db;
	int i;

	ethhdr = (struct ethhdr *)skb_mac_header(skb);

	/* Leave the ethernet header. */
	skb_pull(skb, sizeof(struct ethhdr));

	/* And leave the HSR tag. */
	if (ethhdr->h_proto == htons(ETH_P_HSR))
	skb_pull(skb, sizeof(struct hsr_tag));

	/* And leave the HSR sup tag. */
	skb_pull(skb, sizeof(struct hsr_sup_tag));

	hsr_sp = (struct hsr_sup_payload *)skb->data;

	/* Merge node_curr (registered on macaddress_B) into node_real */
	node_db = &port_rcv->hsr->node_db;
	node_real = find_node_by_addr_A(node_db, hsr_sp->macaddress_A);
	if (!node_real)
	/* No frame received from AddrA of this node yet */
	node_real = hsr_add_node(node_db, hsr_sp->macaddress_A,
	HSR_SEQNR_START - 1);
	if (!node_real)
	goto done; /* No mem */
	if (node_real == node_curr)
	/* Node has already been merged */
	goto done;

	ether_addr_copy(node_real->macaddress_B, ethhdr->h_source);
	for (i = 0; i < HSR_PT_PORTS; i++) {
	if (!node_curr->time_in_stale[i] &&
	time_after(node_curr->time_in[i], node_real->time_in[i])) {
	node_real->time_in[i] = node_curr->time_in[i];
	node_real->time_in_stale[i] =
	node_curr->time_in_stale[i];
	}
	if (seq_nr_after(node_curr->seq_out[i], node_real->seq_out[i]))
	node_real->seq_out[i] = node_curr->seq_out[i];
	}
	node_real->addr_B_port = port_rcv->type;

	list_del_rcu(&node_curr->mac_list);
	kfree_rcu(node_curr, rcu_head);

	done:
	skb_push(skb, sizeof(struct hsrv1_ethhdr_sp));
	}

	/* '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 source
	* address with that node's "official" address (macaddress_A) so that upper
	* layers recognize where it came from.
	*/
	void hsr_addr_subst_source(struct hsr_node node, struct sk_buff skb)
	{
	if (!skb_mac_header_was_set(skb)) {
	WARN_ONCE(1, "%s: Mac header not set\n", __func__);
	return;
	}

	memcpy(&eth_hdr(skb)->h_source, node->macaddress_A, ETH_ALEN);
	}

	/* 'skb' is a frame meant for another host.
	* 'port' is the outgoing interface
	*
	* 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_node node_src, struct sk_buff skb,
	struct hsr_port *port)
	{
	struct hsr_node *node_dst;

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

	if (!is_unicast_ether_addr(eth_hdr(skb)->h_dest))
	return;

	node_dst = find_node_by_addr_A(&port->hsr->node_db,
	eth_hdr(skb)->h_dest);
	if (!node_dst) {
	WARN_ONCE(1, "%s: Unknown node\n", __func__);
	return;
	}
	if (port->type != node_dst->addr_B_port)
	return;

	ether_addr_copy(eth_hdr(skb)->h_dest, node_dst->macaddress_B);
	}

	void hsr_register_frame_in(struct hsr_node node, struct hsr_port port,
	u16 sequence_nr)
	{
	/* Don't register incoming frames without a valid sequence number. This
	* ensures entries of restarted nodes gets pruned so that they can
	* re-register and resume communications.
	*/
	if (seq_nr_before(sequence_nr, node->seq_out[port->type]))
	return;

	node->time_in[port->type] = jiffies;
	node->time_in_stale[port->type] = 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 hsr_port port, struct hsr_node node,
	u16 sequence_nr)
	{
	if (seq_nr_before_or_eq(sequence_nr, node->seq_out[port->type]))
	return 1;

	node->seq_out[port->type] = sequence_nr;
	return 0;
	}

	static struct hsr_port get_late_port(struct hsr_priv hsr,
	struct hsr_node *node)
	{
	if (node->time_in_stale[HSR_PT_SLAVE_A])
	return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_A);
	if (node->time_in_stale[HSR_PT_SLAVE_B])
	return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_B);

	if (time_after(node->time_in[HSR_PT_SLAVE_B],
	node->time_in[HSR_PT_SLAVE_A] +
	msecs_to_jiffies(MAX_SLAVE_DIFF)))
	return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_A);
	if (time_after(node->time_in[HSR_PT_SLAVE_A],
	node->time_in[HSR_PT_SLAVE_B] +
	msecs_to_jiffies(MAX_SLAVE_DIFF)))
	return hsr_port_get_hsr(hsr, HSR_PT_SLAVE_B);

	return NULL;
	}

	/* Remove stale sequence_nr records. Called by timer every
	* HSR_LIFE_CHECK_INTERVAL (two seconds or so).
	*/
	void hsr_prune_nodes(struct timer_list *t)
	{
	struct hsr_priv *hsr = from_timer(hsr, t, prune_timer);
	struct hsr_node *node;
	struct hsr_port *port;
	unsigned long timestamp;
	unsigned long time_a, time_b;

	rcu_read_lock();
	list_for_each_entry_rcu(node, &hsr->node_db, mac_list) {
	/* Don't prune own node. Neither time_in[HSR_PT_SLAVE_A]
	* nor time_in[HSR_PT_SLAVE_B], will ever be updated for
	* the master port. Thus the master node will be repeatedly
	* pruned leading to packet loss.
	*/
	if (hsr_addr_is_self(hsr, node->macaddress_A))
	continue;

	/* Shorthand */
	time_a = node->time_in[HSR_PT_SLAVE_A];
	time_b = node->time_in[HSR_PT_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_PT_SLAVE_A] = true;
	if (time_after(jiffies, time_b + MAX_JIFFY_OFFSET / 2))
	node->time_in_stale[HSR_PT_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_PT_SLAVE_A] \|\|
	(!node->time_in_stale[HSR_PT_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))) {
	rcu_read_lock();
	port = get_late_port(hsr, node);
	if (port)
	hsr_nl_ringerror(hsr, node->macaddress_A, port);
	rcu_read_unlock();
	}

	/* Prune old entries */
	if (time_is_before_jiffies(timestamp +
	msecs_to_jiffies(HSR_NODE_FORGET_TIME))) {
	hsr_nl_nodedown(hsr, node->macaddress_A);
	list_del_rcu(&node->mac_list);
	/* Note that we need to free this entry later: */
	kfree_rcu(node, rcu_head);
	}
	}
	rcu_read_unlock();

	/* Restart timer */
	mod_timer(&hsr->prune_timer,
	jiffies + msecs_to_jiffies(PRUNE_PERIOD));
	}

	void hsr_get_next_node(struct hsr_priv hsr, void *_pos,
	unsigned char addr[ETH_ALEN])
	{
	struct hsr_node *node;

	if (!_pos) {
	node = list_first_or_null_rcu(&hsr->node_db,
	struct hsr_node, mac_list);
	if (node)
	ether_addr_copy(addr, node->macaddress_A);
	return node;
	}

	node = _pos;
	list_for_each_entry_continue_rcu(node, &hsr->node_db, mac_list) {
	ether_addr_copy(addr, node->macaddress_A);
	return node;
	}

	return NULL;
	}

	int hsr_get_node_data(struct hsr_priv *hsr,
	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 hsr_node *node;
	struct hsr_port *port;
	unsigned long tdiff;

	rcu_read_lock();
	node = find_node_by_addr_A(&hsr->node_db, addr);
	if (!node) {
	rcu_read_unlock();
	return -ENOENT; /* No such entry */
	}

	ether_addr_copy(addr_b, node->macaddress_B);

	tdiff = jiffies - node->time_in[HSR_PT_SLAVE_A];
	if (node->time_in_stale[HSR_PT_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_PT_SLAVE_B];
	if (node->time_in_stale[HSR_PT_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_PT_SLAVE_B];
	*if2_seq = node->seq_out[HSR_PT_SLAVE_A];

	if (node->addr_B_port != HSR_PT_NONE) {
	port = hsr_port_get_hsr(hsr, node->addr_B_port);
	*addr_b_ifindex = port->dev->ifindex;
	} else {
	*addr_b_ifindex = -1;
	}

	rcu_read_unlock();

	return 0;
	}