net/hsr/hsr_device.c - kernel/msm-4.9 - Gitiles

 /* 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
  *
  * This file contains device methods for creating, using and destroying
  * virtual HSR devices.
  */

 #include <linux/netdevice.h>
 #include <linux/skbuff.h>
 #include <linux/etherdevice.h>
 #include <linux/if_arp.h>
 #include <linux/rtnetlink.h>
 #include <linux/pkt_sched.h>
 #include "hsr_device.h"
 #include "hsr_framereg.h"
 #include "hsr_main.h"


 static bool is_admin_up(struct net_device *dev)
 {
 	return dev && (dev->flags & IFF_UP);
 }

 static bool is_slave_up(struct net_device *dev)
 {
 	return dev && is_admin_up(dev) && netif_oper_up(dev);
 }

 static void __hsr_set_operstate(struct net_device *dev, int transition)
 {
 	write_lock_bh(&dev_base_lock);
 	if (dev->operstate != transition) {
 		dev->operstate = transition;
 		write_unlock_bh(&dev_base_lock);
 		netdev_state_change(dev);
 	} else {
 		write_unlock_bh(&dev_base_lock);
 	}
 }

 void hsr_set_operstate(struct net_device *hsr_dev, struct net_device *slave1,
 		       struct net_device *slave2)
 {
 	if (!is_admin_up(hsr_dev)) {
 		__hsr_set_operstate(hsr_dev, IF_OPER_DOWN);
 		return;
 	}

 	if (is_slave_up(slave1) || is_slave_up(slave2))
 		__hsr_set_operstate(hsr_dev, IF_OPER_UP);
 	else
 		__hsr_set_operstate(hsr_dev, IF_OPER_LOWERLAYERDOWN);
 }

 void hsr_set_carrier(struct net_device *hsr_dev, struct net_device *slave1,
 		     struct net_device *slave2)
 {
 	if (is_slave_up(slave1) || is_slave_up(slave2))
 		netif_carrier_on(hsr_dev);
 	else
 		netif_carrier_off(hsr_dev);
 }


 void hsr_check_announce(struct net_device *hsr_dev, int old_operstate)
 {
 	struct hsr_priv *hsr_priv;

 	hsr_priv = netdev_priv(hsr_dev);

 	if ((hsr_dev->operstate == IF_OPER_UP) && (old_operstate != IF_OPER_UP)) {
 		/* Went up */
 		hsr_priv->announce_count = 0;
 		hsr_priv->announce_timer.expires = jiffies +
 				msecs_to_jiffies(HSR_ANNOUNCE_INTERVAL);
 		add_timer(&hsr_priv->announce_timer);
 	}

 	if ((hsr_dev->operstate != IF_OPER_UP) && (old_operstate == IF_OPER_UP))
 		/* Went down */
 		del_timer(&hsr_priv->announce_timer);
 }


 int hsr_get_max_mtu(struct hsr_priv *hsr_priv)
 {
 	int mtu_max;

 	if (hsr_priv->slave[0] && hsr_priv->slave[1])
 		mtu_max = min(hsr_priv->slave[0]->mtu, hsr_priv->slave[1]->mtu);
 	else if (hsr_priv->slave[0])
 		mtu_max = hsr_priv->slave[0]->mtu;
 	else if (hsr_priv->slave[1])
 		mtu_max = hsr_priv->slave[1]->mtu;
 	else
 		mtu_max = HSR_TAGLEN;

 	return mtu_max - HSR_TAGLEN;
 }

 static int hsr_dev_change_mtu(struct net_device *dev, int new_mtu)
 {
 	struct hsr_priv *hsr_priv;

 	hsr_priv = netdev_priv(dev);

 	if (new_mtu > hsr_get_max_mtu(hsr_priv)) {
 		netdev_info(hsr_priv->dev, "A HSR master's MTU cannot be greater than the smallest MTU of its slaves minus the HSR Tag length (%d octets).\n",
 			    HSR_TAGLEN);
 		return -EINVAL;
 	}

 	dev->mtu = new_mtu;

 	return 0;
 }

 static int hsr_dev_open(struct net_device *dev)
 {
 	struct hsr_priv *hsr_priv;
 	int i;
 	char *slave_name;

 	hsr_priv = netdev_priv(dev);

 	for (i = 0; i < HSR_MAX_SLAVE; i++) {
 		if (hsr_priv->slave[i])
 			slave_name = hsr_priv->slave[i]->name;
 		else
 			slave_name = "null";

 		if (!is_slave_up(hsr_priv->slave[i]))
 			netdev_warn(dev, "Slave %c (%s) is not up; please bring it up to get a working HSR network\n",
 				    'A' + i, slave_name);
 	}

 	return 0;
 }

 static int hsr_dev_close(struct net_device *dev)
 {
 	/* Nothing to do here. We could try to restore the state of the slaves
 	 * to what they were before being changed by the hsr master dev's state,
 	 * but they might have been changed manually in the mean time too, so
 	 * taking them up or down here might be confusing and is probably not a
 	 * good idea.
 	 */
 	return 0;
 }


 static void hsr_fill_tag(struct hsr_ethhdr *hsr_ethhdr, struct hsr_priv *hsr_priv)
 {
 	unsigned long irqflags;

 	/* IEC 62439-1:2010, p 48, says the 4-bit "path" field can take values
 	 * between 0001-1001 ("ring identifier", for regular HSR frames),
 	 * or 1111 ("HSR management", supervision frames). Unfortunately, the
 	 * spec writers forgot to explain what a "ring identifier" is, or
 	 * how it is used. So we just set this to 0001 for regular frames,
 	 * and 1111 for supervision frames.
 	 */
 	set_hsr_tag_path(&hsr_ethhdr->hsr_tag, 0x1);

 	/* IEC 62439-1:2010, p 12: "The link service data unit in an Ethernet
 	 * frame is the content of the frame located between the Length/Type
 	 * field and the Frame Check Sequence."
 	 *
 	 * IEC 62439-3, p 48, specifies the "original LPDU" to include the
 	 * original "LT" field (what "LT" means is not explained anywhere as
 	 * far as I can see - perhaps "Length/Type"?). So LSDU_size might
 	 * equal original length + 2.
 	 *   Also, the fact that this field is not used anywhere (might be used
 	 * by a RedBox connecting HSR and PRP nets?) means I cannot test its
 	 * correctness. Instead of guessing, I set this to 0 here, to make any
 	 * problems immediately apparent. Anyone using this driver with PRP/HSR
 	 * RedBoxes might need to fix this...
 	 */
 	set_hsr_tag_LSDU_size(&hsr_ethhdr->hsr_tag, 0);

 	spin_lock_irqsave(&hsr_priv->seqnr_lock, irqflags);
 	hsr_ethhdr->hsr_tag.sequence_nr = htons(hsr_priv->sequence_nr);
 	hsr_priv->sequence_nr++;
 	spin_unlock_irqrestore(&hsr_priv->seqnr_lock, irqflags);

 	hsr_ethhdr->hsr_tag.encap_proto = hsr_ethhdr->ethhdr.h_proto;

 	hsr_ethhdr->ethhdr.h_proto = htons(ETH_P_PRP);
 }

 static int slave_xmit(struct sk_buff *skb, struct hsr_priv *hsr_priv,
 		      enum hsr_dev_idx dev_idx)
 {
 	struct hsr_ethhdr *hsr_ethhdr;

 	hsr_ethhdr = (struct hsr_ethhdr *) skb->data;

 	skb->dev = hsr_priv->slave[dev_idx];

 	hsr_addr_subst_dest(hsr_priv, &hsr_ethhdr->ethhdr, dev_idx);

 	/* Address substitution (IEC62439-3 pp 26, 50): replace mac
 	 * address of outgoing frame with that of the outgoing slave's.
 	 */
 	memcpy(hsr_ethhdr->ethhdr.h_source, skb->dev->dev_addr, ETH_ALEN);

 	return dev_queue_xmit(skb);
 }


 static int hsr_dev_xmit(struct sk_buff *skb, struct net_device *dev)
 {
 	struct hsr_priv *hsr_priv;
 	struct hsr_ethhdr *hsr_ethhdr;
 	struct sk_buff *skb2;
 	int res1, res2;

 	hsr_priv = netdev_priv(dev);
 	hsr_ethhdr = (struct hsr_ethhdr *) skb->data;

 	if ((skb->protocol != htons(ETH_P_PRP)) ||
 	    (hsr_ethhdr->ethhdr.h_proto != htons(ETH_P_PRP))) {
 		hsr_fill_tag(hsr_ethhdr, hsr_priv);
 		skb->protocol = htons(ETH_P_PRP);
 	}

 	skb2 = pskb_copy(skb, GFP_ATOMIC);

 	res1 = NET_XMIT_DROP;
 	if (likely(hsr_priv->slave[HSR_DEV_SLAVE_A]))
 		res1 = slave_xmit(skb, hsr_priv, HSR_DEV_SLAVE_A);

 	res2 = NET_XMIT_DROP;
 	if (likely(skb2 && hsr_priv->slave[HSR_DEV_SLAVE_B]))
 		res2 = slave_xmit(skb2, hsr_priv, HSR_DEV_SLAVE_B);

 	if (likely(res1 == NET_XMIT_SUCCESS || res1 == NET_XMIT_CN ||
 		   res2 == NET_XMIT_SUCCESS || res2 == NET_XMIT_CN)) {
 		hsr_priv->dev->stats.tx_packets++;
 		hsr_priv->dev->stats.tx_bytes += skb->len;
 	} else {
 		hsr_priv->dev->stats.tx_dropped++;
 	}

 	return NETDEV_TX_OK;
 }


 static int hsr_header_create(struct sk_buff *skb, struct net_device *dev,
 			     unsigned short type, const void *daddr,
 			     const void *saddr, unsigned int len)
 {
 	int res;

 	/* Make room for the HSR tag now. We will fill it in later (in
 	 * hsr_dev_xmit)
 	 */
 	if (skb_headroom(skb) < HSR_TAGLEN + ETH_HLEN)
 		return -ENOBUFS;
 	skb_push(skb, HSR_TAGLEN);

 	/* To allow VLAN/HSR combos we should probably use
 	 * res = dev_hard_header(skb, dev, type, daddr, saddr, len + HSR_TAGLEN);
 	 * here instead. It would require other changes too, though - e.g.
 	 * separate headers for each slave etc...
 	 */
 	res = eth_header(skb, dev, type, daddr, saddr, len + HSR_TAGLEN);
 	if (res <= 0)
 		return res;
 	skb_reset_mac_header(skb);

 	return res + HSR_TAGLEN;
 }


 static const struct header_ops hsr_header_ops = {
 	.create	 = hsr_header_create,
 	.parse	 = eth_header_parse,
 };


 /* HSR:2010 supervision frames should be padded so that the whole frame,
  * including headers and FCS, is 64 bytes (without VLAN).
  */
 static int hsr_pad(int size)
 {
 	const int min_size = ETH_ZLEN - HSR_TAGLEN - ETH_HLEN;

 	if (size >= min_size)
 		return size;
 	return min_size;
 }

 static void send_hsr_supervision_frame(struct net_device *hsr_dev, u8 type)
 {
 	struct hsr_priv *hsr_priv;
 	struct sk_buff *skb;
 	int hlen, tlen;
 	struct hsr_sup_tag *hsr_stag;
 	struct hsr_sup_payload *hsr_sp;
 	unsigned long irqflags;

 	hlen = LL_RESERVED_SPACE(hsr_dev);
 	tlen = hsr_dev->needed_tailroom;
 	skb = alloc_skb(hsr_pad(sizeof(struct hsr_sup_payload)) + hlen + tlen,
 			GFP_ATOMIC);

 	if (skb == NULL)
 		return;

 	hsr_priv = netdev_priv(hsr_dev);

 	skb_reserve(skb, hlen);

 	skb->dev = hsr_dev;
 	skb->protocol = htons(ETH_P_PRP);
 	skb->priority = TC_PRIO_CONTROL;

 	if (dev_hard_header(skb, skb->dev, ETH_P_PRP,
 			    hsr_priv->sup_multicast_addr,
 			    skb->dev->dev_addr, skb->len) < 0)
 		goto out;

 	skb_pull(skb, sizeof(struct ethhdr));
 	hsr_stag = (typeof(hsr_stag)) skb->data;

 	set_hsr_stag_path(hsr_stag, 0xf);
 	set_hsr_stag_HSR_Ver(hsr_stag, 0);

 	spin_lock_irqsave(&hsr_priv->seqnr_lock, irqflags);
 	hsr_stag->sequence_nr = htons(hsr_priv->sequence_nr);
 	hsr_priv->sequence_nr++;
 	spin_unlock_irqrestore(&hsr_priv->seqnr_lock, irqflags);

 	hsr_stag->HSR_TLV_Type = type;
 	hsr_stag->HSR_TLV_Length = 12;

 	skb_push(skb, sizeof(struct ethhdr));

 	/* Payload: MacAddressA */
 	hsr_sp = (typeof(hsr_sp)) skb_put(skb, sizeof(*hsr_sp));
 	memcpy(hsr_sp->MacAddressA, hsr_dev->dev_addr, ETH_ALEN);

 	dev_queue_xmit(skb);
 	return;

 out:
 	kfree_skb(skb);
 }


 /* Announce (supervision frame) timer function
  */
 static void hsr_announce(unsigned long data)
 {
 	struct hsr_priv *hsr_priv;

 	hsr_priv = (struct hsr_priv *) data;

 	if (hsr_priv->announce_count < 3) {
 		send_hsr_supervision_frame(hsr_priv->dev, HSR_TLV_ANNOUNCE);
 		hsr_priv->announce_count++;
 	} else {
 		send_hsr_supervision_frame(hsr_priv->dev, HSR_TLV_LIFE_CHECK);
 	}

 	if (hsr_priv->announce_count < 3)
 		hsr_priv->announce_timer.expires = jiffies +
 				msecs_to_jiffies(HSR_ANNOUNCE_INTERVAL);
 	else
 		hsr_priv->announce_timer.expires = jiffies +
 				msecs_to_jiffies(HSR_LIFE_CHECK_INTERVAL);

 	if (is_admin_up(hsr_priv->dev))
 		add_timer(&hsr_priv->announce_timer);
 }


 static void restore_slaves(struct net_device *hsr_dev)
 {
 	struct hsr_priv *hsr_priv;
 	int i;
 	int res;

 	hsr_priv = netdev_priv(hsr_dev);

 	rtnl_lock();

 	/* Restore promiscuity */
 	for (i = 0; i < HSR_MAX_SLAVE; i++) {
 		if (!hsr_priv->slave[i])
 			continue;
 		res = dev_set_promiscuity(hsr_priv->slave[i], -1);
 		if (res)
 			netdev_info(hsr_dev,
 				    "Cannot restore slave promiscuity (%s, %d)\n",
 				    hsr_priv->slave[i]->name, res);
 	}

 	rtnl_unlock();
 }

 static void reclaim_hsr_dev(struct rcu_head *rh)
 {
 	struct hsr_priv *hsr_priv;

 	hsr_priv = container_of(rh, struct hsr_priv, rcu_head);
 	free_netdev(hsr_priv->dev);
 }


 /* According to comments in the declaration of struct net_device, this function
  * is "Called from unregister, can be used to call free_netdev". Ok then...
  */
 static void hsr_dev_destroy(struct net_device *hsr_dev)
 {
 	struct hsr_priv *hsr_priv;

 	hsr_priv = netdev_priv(hsr_dev);

 	del_timer(&hsr_priv->announce_timer);
 	unregister_hsr_master(hsr_priv);    /* calls list_del_rcu on hsr_priv */
 	restore_slaves(hsr_dev);
 	call_rcu(&hsr_priv->rcu_head, reclaim_hsr_dev);   /* reclaim hsr_priv */
 }

 static const struct net_device_ops hsr_device_ops = {
 	.ndo_change_mtu = hsr_dev_change_mtu,
 	.ndo_open = hsr_dev_open,
 	.ndo_stop = hsr_dev_close,
 	.ndo_start_xmit = hsr_dev_xmit,
 };


 void hsr_dev_setup(struct net_device *dev)
 {
 	random_ether_addr(dev->dev_addr);

 	ether_setup(dev);
 	dev->header_ops		 = &hsr_header_ops;
 	dev->netdev_ops		 = &hsr_device_ops;
 	dev->tx_queue_len	 = 0;

 	dev->destructor = hsr_dev_destroy;
 }


 /* Return true if dev is a HSR master; return false otherwise.
  */
 bool is_hsr_master(struct net_device *dev)
 {
 	return (dev->netdev_ops->ndo_start_xmit == hsr_dev_xmit);
 }

 static int check_slave_ok(struct net_device *dev)
 {
 	/* Don't allow HSR on non-ethernet like devices */
 	if ((dev->flags & IFF_LOOPBACK) || (dev->type != ARPHRD_ETHER) ||
 	    (dev->addr_len != ETH_ALEN)) {
 		netdev_info(dev, "Cannot use loopback or non-ethernet device as HSR slave.\n");
 		return -EINVAL;
 	}

 	/* Don't allow enslaving hsr devices */
 	if (is_hsr_master(dev)) {
 		netdev_info(dev, "Cannot create trees of HSR devices.\n");
 		return -EINVAL;
 	}

 	if (is_hsr_slave(dev)) {
 		netdev_info(dev, "This device is already a HSR slave.\n");
 		return -EINVAL;
 	}

 	if (dev->priv_flags & IFF_802_1Q_VLAN) {
 		netdev_info(dev, "HSR on top of VLAN is not yet supported in this driver.\n");
 		return -EINVAL;
 	}

 	/* HSR over bonded devices has not been tested, but I'm not sure it
 	 * won't work...
 	 */

 	return 0;
 }


 /* Default multicast address for HSR Supervision frames */
 static const unsigned char def_multicast_addr[ETH_ALEN] = {
 	0x01, 0x15, 0x4e, 0x00, 0x01, 0x00
 };

 int hsr_dev_finalize(struct net_device *hsr_dev, struct net_device *slave[2],
 		     unsigned char multicast_spec)
 {
 	struct hsr_priv *hsr_priv;
 	int i;
 	int res;

 	hsr_priv = netdev_priv(hsr_dev);
 	hsr_priv->dev = hsr_dev;
 	INIT_LIST_HEAD(&hsr_priv->node_db);
 	INIT_LIST_HEAD(&hsr_priv->self_node_db);
 	for (i = 0; i < HSR_MAX_SLAVE; i++)
 		hsr_priv->slave[i] = slave[i];

 	spin_lock_init(&hsr_priv->seqnr_lock);
 	/* Overflow soon to find bugs easier: */
 	hsr_priv->sequence_nr = USHRT_MAX - 1024;

 	init_timer(&hsr_priv->announce_timer);
 	hsr_priv->announce_timer.function = hsr_announce;
 	hsr_priv->announce_timer.data = (unsigned long) hsr_priv;

 	memcpy(hsr_priv->sup_multicast_addr, def_multicast_addr, ETH_ALEN);
 	hsr_priv->sup_multicast_addr[ETH_ALEN - 1] = multicast_spec;

 /* FIXME: should I modify the value of these?
  *
  * - hsr_dev->flags - i.e.
  *			IFF_MASTER/SLAVE?
  * - hsr_dev->priv_flags - i.e.
  *			IFF_EBRIDGE?
  *			IFF_TX_SKB_SHARING?
  *			IFF_HSR_MASTER/SLAVE?
  */

 	for (i = 0; i < HSR_MAX_SLAVE; i++) {
 		res = check_slave_ok(slave[i]);
 		if (res)
 			return res;
 	}

 	hsr_dev->features = slave[0]->features & slave[1]->features;
 	/* Prevent recursive tx locking */
 	hsr_dev->features |= NETIF_F_LLTX;
 	/* VLAN on top of HSR needs testing and probably some work on
 	 * hsr_header_create() etc.
 	 */
 	hsr_dev->features |= NETIF_F_VLAN_CHALLENGED;

 	/* Set hsr_dev's MAC address to that of mac_slave1 */
 	memcpy(hsr_dev->dev_addr, hsr_priv->slave[0]->dev_addr, ETH_ALEN);

 	/* Set required header length */
 	for (i = 0; i < HSR_MAX_SLAVE; i++) {
 		if (slave[i]->hard_header_len + HSR_TAGLEN >
 						hsr_dev->hard_header_len)
 			hsr_dev->hard_header_len =
 					slave[i]->hard_header_len + HSR_TAGLEN;
 	}

 	/* MTU */
 	for (i = 0; i < HSR_MAX_SLAVE; i++)
 		if (slave[i]->mtu - HSR_TAGLEN < hsr_dev->mtu)
 			hsr_dev->mtu = slave[i]->mtu - HSR_TAGLEN;

 	/* Make sure the 1st call to netif_carrier_on() gets through */
 	netif_carrier_off(hsr_dev);

 	/* Promiscuity */
 	for (i = 0; i < HSR_MAX_SLAVE; i++) {
 		res = dev_set_promiscuity(slave[i], 1);
 		if (res) {
 			netdev_info(hsr_dev, "Cannot set slave promiscuity (%s, %d)\n",
 				    slave[i]->name, res);
 			goto fail;
 		}
 	}

 	/* Make sure we recognize frames from ourselves in hsr_rcv() */
 	res = hsr_create_self_node(&hsr_priv->self_node_db,
 					hsr_dev->dev_addr,
 					hsr_priv->slave[1]->dev_addr);
 	if (res < 0)
 		goto fail;

 	res = register_netdevice(hsr_dev);
 	if (res)
 		goto fail;

 	register_hsr_master(hsr_priv);

 	return 0;

 fail:
 	restore_slaves(hsr_dev);
 	return res;
 }
	/* 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
	*
	* This file contains device methods for creating, using and destroying
	* virtual HSR devices.
	*/

	#include <linux/netdevice.h>
	#include <linux/skbuff.h>
	#include <linux/etherdevice.h>
	#include <linux/if_arp.h>
	#include <linux/rtnetlink.h>
	#include <linux/pkt_sched.h>
	#include "hsr_device.h"
	#include "hsr_framereg.h"
	#include "hsr_main.h"


	static bool is_admin_up(struct net_device *dev)
	{
	return dev && (dev->flags & IFF_UP);
	}

	static bool is_slave_up(struct net_device *dev)
	{
	return dev && is_admin_up(dev) && netif_oper_up(dev);
	}

	static void __hsr_set_operstate(struct net_device *dev, int transition)
	{
	write_lock_bh(&dev_base_lock);
	if (dev->operstate != transition) {
	dev->operstate = transition;
	write_unlock_bh(&dev_base_lock);
	netdev_state_change(dev);
	} else {
	write_unlock_bh(&dev_base_lock);
	}
	}

	void hsr_set_operstate(struct net_device hsr_dev, struct net_device slave1,
	struct net_device *slave2)
	{
	if (!is_admin_up(hsr_dev)) {
	__hsr_set_operstate(hsr_dev, IF_OPER_DOWN);
	return;
	}

	if (is_slave_up(slave1) \|\| is_slave_up(slave2))
	__hsr_set_operstate(hsr_dev, IF_OPER_UP);
	else
	__hsr_set_operstate(hsr_dev, IF_OPER_LOWERLAYERDOWN);
	}

	void hsr_set_carrier(struct net_device hsr_dev, struct net_device slave1,
	struct net_device *slave2)
	{
	if (is_slave_up(slave1) \|\| is_slave_up(slave2))
	netif_carrier_on(hsr_dev);
	else
	netif_carrier_off(hsr_dev);
	}


	void hsr_check_announce(struct net_device *hsr_dev, int old_operstate)
	{
	struct hsr_priv *hsr_priv;

	hsr_priv = netdev_priv(hsr_dev);

	if ((hsr_dev->operstate == IF_OPER_UP) && (old_operstate != IF_OPER_UP)) {
	/* Went up */
	hsr_priv->announce_count = 0;
	hsr_priv->announce_timer.expires = jiffies +
	msecs_to_jiffies(HSR_ANNOUNCE_INTERVAL);
	add_timer(&hsr_priv->announce_timer);
	}

	if ((hsr_dev->operstate != IF_OPER_UP) && (old_operstate == IF_OPER_UP))
	/* Went down */
	del_timer(&hsr_priv->announce_timer);
	}


	int hsr_get_max_mtu(struct hsr_priv *hsr_priv)
	{
	int mtu_max;

	if (hsr_priv->slave[0] && hsr_priv->slave[1])
	mtu_max = min(hsr_priv->slave[0]->mtu, hsr_priv->slave[1]->mtu);
	else if (hsr_priv->slave[0])
	mtu_max = hsr_priv->slave[0]->mtu;
	else if (hsr_priv->slave[1])
	mtu_max = hsr_priv->slave[1]->mtu;
	else
	mtu_max = HSR_TAGLEN;

	return mtu_max - HSR_TAGLEN;
	}

	static int hsr_dev_change_mtu(struct net_device *dev, int new_mtu)
	{
	struct hsr_priv *hsr_priv;

	hsr_priv = netdev_priv(dev);

	if (new_mtu > hsr_get_max_mtu(hsr_priv)) {
	netdev_info(hsr_priv->dev, "A HSR master's MTU cannot be greater than the smallest MTU of its slaves minus the HSR Tag length (%d octets).\n",
	HSR_TAGLEN);
	return -EINVAL;
	}

	dev->mtu = new_mtu;

	return 0;
	}

	static int hsr_dev_open(struct net_device *dev)
	{
	struct hsr_priv *hsr_priv;
	int i;
	char *slave_name;

	hsr_priv = netdev_priv(dev);

	for (i = 0; i < HSR_MAX_SLAVE; i++) {
	if (hsr_priv->slave[i])
	slave_name = hsr_priv->slave[i]->name;
	else
	slave_name = "null";

	if (!is_slave_up(hsr_priv->slave[i]))
	netdev_warn(dev, "Slave %c (%s) is not up; please bring it up to get a working HSR network\n",
	'A' + i, slave_name);
	}

	return 0;
	}

	static int hsr_dev_close(struct net_device *dev)
	{
	/* Nothing to do here. We could try to restore the state of the slaves
	* to what they were before being changed by the hsr master dev's state,
	* but they might have been changed manually in the mean time too, so
	* taking them up or down here might be confusing and is probably not a
	* good idea.
	*/
	return 0;
	}


	static void hsr_fill_tag(struct hsr_ethhdr hsr_ethhdr, struct hsr_priv hsr_priv)
	{
	unsigned long irqflags;

	/* IEC 62439-1:2010, p 48, says the 4-bit "path" field can take values
	* between 0001-1001 ("ring identifier", for regular HSR frames),
	* or 1111 ("HSR management", supervision frames). Unfortunately, the
	* spec writers forgot to explain what a "ring identifier" is, or
	* how it is used. So we just set this to 0001 for regular frames,
	* and 1111 for supervision frames.
	*/
	set_hsr_tag_path(&hsr_ethhdr->hsr_tag, 0x1);

	/* IEC 62439-1:2010, p 12: "The link service data unit in an Ethernet
	* frame is the content of the frame located between the Length/Type
	* field and the Frame Check Sequence."
	*
	* IEC 62439-3, p 48, specifies the "original LPDU" to include the
	* original "LT" field (what "LT" means is not explained anywhere as
	* far as I can see - perhaps "Length/Type"?). So LSDU_size might
	* equal original length + 2.
	* Also, the fact that this field is not used anywhere (might be used
	* by a RedBox connecting HSR and PRP nets?) means I cannot test its
	* correctness. Instead of guessing, I set this to 0 here, to make any
	* problems immediately apparent. Anyone using this driver with PRP/HSR
	* RedBoxes might need to fix this...
	*/
	set_hsr_tag_LSDU_size(&hsr_ethhdr->hsr_tag, 0);

	spin_lock_irqsave(&hsr_priv->seqnr_lock, irqflags);
	hsr_ethhdr->hsr_tag.sequence_nr = htons(hsr_priv->sequence_nr);
	hsr_priv->sequence_nr++;
	spin_unlock_irqrestore(&hsr_priv->seqnr_lock, irqflags);

	hsr_ethhdr->hsr_tag.encap_proto = hsr_ethhdr->ethhdr.h_proto;

	hsr_ethhdr->ethhdr.h_proto = htons(ETH_P_PRP);
	}

	static int slave_xmit(struct sk_buff skb, struct hsr_priv hsr_priv,
	enum hsr_dev_idx dev_idx)
	{
	struct hsr_ethhdr *hsr_ethhdr;

	hsr_ethhdr = (struct hsr_ethhdr *) skb->data;

	skb->dev = hsr_priv->slave[dev_idx];

	hsr_addr_subst_dest(hsr_priv, &hsr_ethhdr->ethhdr, dev_idx);

	/* Address substitution (IEC62439-3 pp 26, 50): replace mac
	* address of outgoing frame with that of the outgoing slave's.
	*/
	memcpy(hsr_ethhdr->ethhdr.h_source, skb->dev->dev_addr, ETH_ALEN);

	return dev_queue_xmit(skb);
	}


	static int hsr_dev_xmit(struct sk_buff skb, struct net_device dev)
	{
	struct hsr_priv *hsr_priv;
	struct hsr_ethhdr *hsr_ethhdr;
	struct sk_buff *skb2;
	int res1, res2;

	hsr_priv = netdev_priv(dev);
	hsr_ethhdr = (struct hsr_ethhdr *) skb->data;

	if ((skb->protocol != htons(ETH_P_PRP)) \|\|
	(hsr_ethhdr->ethhdr.h_proto != htons(ETH_P_PRP))) {
	hsr_fill_tag(hsr_ethhdr, hsr_priv);
	skb->protocol = htons(ETH_P_PRP);
	}

	skb2 = pskb_copy(skb, GFP_ATOMIC);

	res1 = NET_XMIT_DROP;
	if (likely(hsr_priv->slave[HSR_DEV_SLAVE_A]))
	res1 = slave_xmit(skb, hsr_priv, HSR_DEV_SLAVE_A);

	res2 = NET_XMIT_DROP;
	if (likely(skb2 && hsr_priv->slave[HSR_DEV_SLAVE_B]))
	res2 = slave_xmit(skb2, hsr_priv, HSR_DEV_SLAVE_B);

	if (likely(res1 == NET_XMIT_SUCCESS \|\| res1 == NET_XMIT_CN \|\|
	res2 == NET_XMIT_SUCCESS \|\| res2 == NET_XMIT_CN)) {
	hsr_priv->dev->stats.tx_packets++;
	hsr_priv->dev->stats.tx_bytes += skb->len;
	} else {
	hsr_priv->dev->stats.tx_dropped++;
	}

	return NETDEV_TX_OK;
	}


	static int hsr_header_create(struct sk_buff skb, struct net_device dev,
	unsigned short type, const void *daddr,
	const void *saddr, unsigned int len)
	{
	int res;

	/* Make room for the HSR tag now. We will fill it in later (in
	* hsr_dev_xmit)
	*/
	if (skb_headroom(skb) < HSR_TAGLEN + ETH_HLEN)
	return -ENOBUFS;
	skb_push(skb, HSR_TAGLEN);

	/* To allow VLAN/HSR combos we should probably use
	* res = dev_hard_header(skb, dev, type, daddr, saddr, len + HSR_TAGLEN);
	* here instead. It would require other changes too, though - e.g.
	* separate headers for each slave etc...
	*/
	res = eth_header(skb, dev, type, daddr, saddr, len + HSR_TAGLEN);
	if (res <= 0)
	return res;
	skb_reset_mac_header(skb);

	return res + HSR_TAGLEN;
	}


	static const struct header_ops hsr_header_ops = {
	.create = hsr_header_create,
	.parse = eth_header_parse,
	};


	/* HSR:2010 supervision frames should be padded so that the whole frame,
	* including headers and FCS, is 64 bytes (without VLAN).
	*/
	static int hsr_pad(int size)
	{
	const int min_size = ETH_ZLEN - HSR_TAGLEN - ETH_HLEN;

	if (size >= min_size)
	return size;
	return min_size;
	}

	static void send_hsr_supervision_frame(struct net_device *hsr_dev, u8 type)
	{
	struct hsr_priv *hsr_priv;
	struct sk_buff *skb;
	int hlen, tlen;
	struct hsr_sup_tag *hsr_stag;
	struct hsr_sup_payload *hsr_sp;
	unsigned long irqflags;

	hlen = LL_RESERVED_SPACE(hsr_dev);
	tlen = hsr_dev->needed_tailroom;
	skb = alloc_skb(hsr_pad(sizeof(struct hsr_sup_payload)) + hlen + tlen,
	GFP_ATOMIC);

	if (skb == NULL)
	return;

	hsr_priv = netdev_priv(hsr_dev);

	skb_reserve(skb, hlen);

	skb->dev = hsr_dev;
	skb->protocol = htons(ETH_P_PRP);
	skb->priority = TC_PRIO_CONTROL;

	if (dev_hard_header(skb, skb->dev, ETH_P_PRP,
	hsr_priv->sup_multicast_addr,
	skb->dev->dev_addr, skb->len) < 0)
	goto out;

	skb_pull(skb, sizeof(struct ethhdr));
	hsr_stag = (typeof(hsr_stag)) skb->data;

	set_hsr_stag_path(hsr_stag, 0xf);
	set_hsr_stag_HSR_Ver(hsr_stag, 0);

	spin_lock_irqsave(&hsr_priv->seqnr_lock, irqflags);
	hsr_stag->sequence_nr = htons(hsr_priv->sequence_nr);
	hsr_priv->sequence_nr++;
	spin_unlock_irqrestore(&hsr_priv->seqnr_lock, irqflags);

	hsr_stag->HSR_TLV_Type = type;
	hsr_stag->HSR_TLV_Length = 12;

	skb_push(skb, sizeof(struct ethhdr));

	/* Payload: MacAddressA */
	hsr_sp = (typeof(hsr_sp)) skb_put(skb, sizeof(*hsr_sp));
	memcpy(hsr_sp->MacAddressA, hsr_dev->dev_addr, ETH_ALEN);

	dev_queue_xmit(skb);
	return;

	out:
	kfree_skb(skb);
	}


	/* Announce (supervision frame) timer function
	*/
	static void hsr_announce(unsigned long data)
	{
	struct hsr_priv *hsr_priv;

	hsr_priv = (struct hsr_priv *) data;

	if (hsr_priv->announce_count < 3) {
	send_hsr_supervision_frame(hsr_priv->dev, HSR_TLV_ANNOUNCE);
	hsr_priv->announce_count++;
	} else {
	send_hsr_supervision_frame(hsr_priv->dev, HSR_TLV_LIFE_CHECK);
	}

	if (hsr_priv->announce_count < 3)
	hsr_priv->announce_timer.expires = jiffies +
	msecs_to_jiffies(HSR_ANNOUNCE_INTERVAL);
	else
	hsr_priv->announce_timer.expires = jiffies +
	msecs_to_jiffies(HSR_LIFE_CHECK_INTERVAL);

	if (is_admin_up(hsr_priv->dev))
	add_timer(&hsr_priv->announce_timer);
	}


	static void restore_slaves(struct net_device *hsr_dev)
	{
	struct hsr_priv *hsr_priv;
	int i;
	int res;

	hsr_priv = netdev_priv(hsr_dev);

	rtnl_lock();

	/* Restore promiscuity */
	for (i = 0; i < HSR_MAX_SLAVE; i++) {
	if (!hsr_priv->slave[i])
	continue;
	res = dev_set_promiscuity(hsr_priv->slave[i], -1);
	if (res)
	netdev_info(hsr_dev,
	"Cannot restore slave promiscuity (%s, %d)\n",
	hsr_priv->slave[i]->name, res);
	}

	rtnl_unlock();
	}

	static void reclaim_hsr_dev(struct rcu_head *rh)
	{
	struct hsr_priv *hsr_priv;

	hsr_priv = container_of(rh, struct hsr_priv, rcu_head);
	free_netdev(hsr_priv->dev);
	}


	/* According to comments in the declaration of struct net_device, this function
	* is "Called from unregister, can be used to call free_netdev". Ok then...
	*/
	static void hsr_dev_destroy(struct net_device *hsr_dev)
	{
	struct hsr_priv *hsr_priv;

	hsr_priv = netdev_priv(hsr_dev);

	del_timer(&hsr_priv->announce_timer);
	unregister_hsr_master(hsr_priv); /* calls list_del_rcu on hsr_priv */
	restore_slaves(hsr_dev);
	call_rcu(&hsr_priv->rcu_head, reclaim_hsr_dev); /* reclaim hsr_priv */
	}

	static const struct net_device_ops hsr_device_ops = {
	.ndo_change_mtu = hsr_dev_change_mtu,
	.ndo_open = hsr_dev_open,
	.ndo_stop = hsr_dev_close,
	.ndo_start_xmit = hsr_dev_xmit,
	};


	void hsr_dev_setup(struct net_device *dev)
	{
	random_ether_addr(dev->dev_addr);

	ether_setup(dev);
	dev->header_ops = &hsr_header_ops;
	dev->netdev_ops = &hsr_device_ops;
	dev->tx_queue_len = 0;

	dev->destructor = hsr_dev_destroy;
	}


	/* Return true if dev is a HSR master; return false otherwise.
	*/
	bool is_hsr_master(struct net_device *dev)
	{
	return (dev->netdev_ops->ndo_start_xmit == hsr_dev_xmit);
	}

	static int check_slave_ok(struct net_device *dev)
	{
	/* Don't allow HSR on non-ethernet like devices */
	if ((dev->flags & IFF_LOOPBACK) \|\| (dev->type != ARPHRD_ETHER) \|\|
	(dev->addr_len != ETH_ALEN)) {
	netdev_info(dev, "Cannot use loopback or non-ethernet device as HSR slave.\n");
	return -EINVAL;
	}

	/* Don't allow enslaving hsr devices */
	if (is_hsr_master(dev)) {
	netdev_info(dev, "Cannot create trees of HSR devices.\n");
	return -EINVAL;
	}

	if (is_hsr_slave(dev)) {
	netdev_info(dev, "This device is already a HSR slave.\n");
	return -EINVAL;
	}

	if (dev->priv_flags & IFF_802_1Q_VLAN) {
	netdev_info(dev, "HSR on top of VLAN is not yet supported in this driver.\n");
	return -EINVAL;
	}

	/* HSR over bonded devices has not been tested, but I'm not sure it
	* won't work...
	*/

	return 0;
	}


	/* Default multicast address for HSR Supervision frames */
	static const unsigned char def_multicast_addr[ETH_ALEN] = {
	0x01, 0x15, 0x4e, 0x00, 0x01, 0x00
	};

	int hsr_dev_finalize(struct net_device hsr_dev, struct net_device slave[2],
	unsigned char multicast_spec)
	{
	struct hsr_priv *hsr_priv;
	int i;
	int res;

	hsr_priv = netdev_priv(hsr_dev);
	hsr_priv->dev = hsr_dev;
	INIT_LIST_HEAD(&hsr_priv->node_db);
	INIT_LIST_HEAD(&hsr_priv->self_node_db);
	for (i = 0; i < HSR_MAX_SLAVE; i++)
	hsr_priv->slave[i] = slave[i];

	spin_lock_init(&hsr_priv->seqnr_lock);
	/* Overflow soon to find bugs easier: */
	hsr_priv->sequence_nr = USHRT_MAX - 1024;

	init_timer(&hsr_priv->announce_timer);
	hsr_priv->announce_timer.function = hsr_announce;
	hsr_priv->announce_timer.data = (unsigned long) hsr_priv;

	memcpy(hsr_priv->sup_multicast_addr, def_multicast_addr, ETH_ALEN);
	hsr_priv->sup_multicast_addr[ETH_ALEN - 1] = multicast_spec;

	/* FIXME: should I modify the value of these?
	*
	* - hsr_dev->flags - i.e.
	* IFF_MASTER/SLAVE?
	* - hsr_dev->priv_flags - i.e.
	* IFF_EBRIDGE?
	* IFF_TX_SKB_SHARING?
	* IFF_HSR_MASTER/SLAVE?
	*/

	for (i = 0; i < HSR_MAX_SLAVE; i++) {
	res = check_slave_ok(slave[i]);
	if (res)
	return res;
	}

	hsr_dev->features = slave[0]->features & slave[1]->features;
	/* Prevent recursive tx locking */
	hsr_dev->features \|= NETIF_F_LLTX;
	/* VLAN on top of HSR needs testing and probably some work on
	* hsr_header_create() etc.
	*/
	hsr_dev->features \|= NETIF_F_VLAN_CHALLENGED;

	/* Set hsr_dev's MAC address to that of mac_slave1 */
	memcpy(hsr_dev->dev_addr, hsr_priv->slave[0]->dev_addr, ETH_ALEN);

	/* Set required header length */
	for (i = 0; i < HSR_MAX_SLAVE; i++) {
	if (slave[i]->hard_header_len + HSR_TAGLEN >
	hsr_dev->hard_header_len)
	hsr_dev->hard_header_len =
	slave[i]->hard_header_len + HSR_TAGLEN;
	}

	/* MTU */
	for (i = 0; i < HSR_MAX_SLAVE; i++)
	if (slave[i]->mtu - HSR_TAGLEN < hsr_dev->mtu)
	hsr_dev->mtu = slave[i]->mtu - HSR_TAGLEN;

	/* Make sure the 1st call to netif_carrier_on() gets through */
	netif_carrier_off(hsr_dev);

	/* Promiscuity */
	for (i = 0; i < HSR_MAX_SLAVE; i++) {
	res = dev_set_promiscuity(slave[i], 1);
	if (res) {
	netdev_info(hsr_dev, "Cannot set slave promiscuity (%s, %d)\n",
	slave[i]->name, res);
	goto fail;
	}
	}

	/* Make sure we recognize frames from ourselves in hsr_rcv() */
	res = hsr_create_self_node(&hsr_priv->self_node_db,
	hsr_dev->dev_addr,
	hsr_priv->slave[1]->dev_addr);
	if (res < 0)
	goto fail;

	res = register_netdevice(hsr_dev);
	if (res)
	goto fail;

	register_hsr_master(hsr_priv);

	return 0;

	fail:
	restore_slaves(hsr_dev);
	return res;
	}