net/hsr: Add support for the High-availability Seamless Redundancy protocol (HSRv0)

High-availability Seamless Redundancy ("HSR") provides instant failover
redundancy for Ethernet networks. It requires a special network topology where
all nodes are connected in a ring (each node having two physical network
interfaces). It is suited for applications that demand high availability and
very short reaction time.

HSR acts on the Ethernet layer, using a registered Ethernet protocol type to
send special HSR frames in both directions over the ring. The driver creates
virtual network interfaces that can be used just like any ordinary Linux
network interface, for IP/TCP/UDP traffic etc. All nodes in the network ring
must be HSR capable.

This code is a "best effort" to comply with the HSR standard as described in
IEC 62439-3:2010 (HSRv0).

Signed-off-by: Arvid Brodin <arvid.brodin@xdin.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 469 insertions, 0 deletions

diff --git a/net/hsr/hsr_main.c b/net/hsr/hsr_main.c
new file mode 100644
index 000000000000..af68dd83a4e3
--- /dev/null
+++ b/net/hsr/hsr_main.c
@@ -0,0 +1,469 @@
+/* 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
+ *
+ * In addition to routines for registering and unregistering HSR support, this
+ * file also contains the receive routine that handles all incoming frames with
+ * Ethertype (protocol) ETH_P_PRP (HSRv0), and network device event handling.
+ */
+
+#include <linux/netdevice.h>
+#include <linux/rculist.h>
+#include <linux/timer.h>
+#include <linux/etherdevice.h>
+#include "hsr_main.h"
+#include "hsr_device.h"
+#include "hsr_netlink.h"
+#include "hsr_framereg.h"
+
+
+/* List of all registered virtual HSR devices */
+static LIST_HEAD(hsr_list);
+
+void register_hsr_master(struct hsr_priv *hsr_priv)
+{
+	list_add_tail_rcu(&hsr_priv->hsr_list, &hsr_list);
+}
+
+void unregister_hsr_master(struct hsr_priv *hsr_priv)
+{
+	struct hsr_priv *hsr_priv_it;
+
+	list_for_each_entry(hsr_priv_it, &hsr_list, hsr_list)
+		if (hsr_priv_it == hsr_priv) {
+			list_del_rcu(&hsr_priv_it->hsr_list);
+			return;
+		}
+}
+
+bool is_hsr_slave(struct net_device *dev)
+{
+	struct hsr_priv *hsr_priv_it;
+
+	list_for_each_entry_rcu(hsr_priv_it, &hsr_list, hsr_list) {
+		if (dev == hsr_priv_it->slave[0])
+			return true;
+		if (dev == hsr_priv_it->slave[1])
+			return true;
+	}
+
+	return false;
+}
+
+
+/* If dev is a HSR slave device, return the virtual master device. Return NULL
+ * otherwise.
+ */
+static struct hsr_priv *get_hsr_master(struct net_device *dev)
+{
+	struct hsr_priv *hsr_priv;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(hsr_priv, &hsr_list, hsr_list)
+		if ((dev == hsr_priv->slave[0]) ||
+		    (dev == hsr_priv->slave[1])) {
+			rcu_read_unlock();
+			return hsr_priv;
+		}
+
+	rcu_read_unlock();
+	return NULL;
+}
+
+
+/* If dev is a HSR slave device, return the other slave device. Return NULL
+ * otherwise.
+ */
+static struct net_device *get_other_slave(struct hsr_priv *hsr_priv,
+					  struct net_device *dev)
+{
+	if (dev == hsr_priv->slave[0])
+		return hsr_priv->slave[1];
+	if (dev == hsr_priv->slave[1])
+		return hsr_priv->slave[0];
+
+	return NULL;
+}
+
+
+static int hsr_netdev_notify(struct notifier_block *nb, unsigned long event,
+			     void *ptr)
+{
+	struct net_device *slave, *other_slave;
+	struct hsr_priv *hsr_priv;
+	int old_operstate;
+	int mtu_max;
+	int res;
+	struct net_device *dev;
+
+	dev = netdev_notifier_info_to_dev(ptr);
+
+	hsr_priv = get_hsr_master(dev);
+	if (hsr_priv) {
+		/* dev is a slave device */
+		slave = dev;
+		other_slave = get_other_slave(hsr_priv, slave);
+	} else {
+		if (!is_hsr_master(dev))
+			return NOTIFY_DONE;
+		hsr_priv = netdev_priv(dev);
+		slave = hsr_priv->slave[0];
+		other_slave = hsr_priv->slave[1];
+	}
+
+	switch (event) {
+	case NETDEV_UP:		/* Administrative state DOWN */
+	case NETDEV_DOWN:	/* Administrative state UP */
+	case NETDEV_CHANGE:	/* Link (carrier) state changes */
+		old_operstate = hsr_priv->dev->operstate;
+		hsr_set_carrier(hsr_priv->dev, slave, other_slave);
+		/* netif_stacked_transfer_operstate() cannot be used here since
+		 * it doesn't set IF_OPER_LOWERLAYERDOWN (?)
+		 */
+		hsr_set_operstate(hsr_priv->dev, slave, other_slave);
+		hsr_check_announce(hsr_priv->dev, old_operstate);
+		break;
+	case NETDEV_CHANGEADDR:
+
+		/* This should not happen since there's no ndo_set_mac_address()
+		 * for HSR devices - i.e. not supported.
+		 */
+		if (dev == hsr_priv->dev)
+			break;
+
+		if (dev == hsr_priv->slave[0])
+			memcpy(hsr_priv->dev->dev_addr,
+			       hsr_priv->slave[0]->dev_addr, ETH_ALEN);
+
+		/* Make sure we recognize frames from ourselves in hsr_rcv() */
+		res = hsr_create_self_node(&hsr_priv->self_node_db,
+					   hsr_priv->dev->dev_addr,
+					   hsr_priv->slave[1] ?
+						hsr_priv->slave[1]->dev_addr :
+						hsr_priv->dev->dev_addr);
+		if (res)
+			netdev_warn(hsr_priv->dev,
+				    "Could not update HSR node address.\n");
+
+		if (dev == hsr_priv->slave[0])
+			call_netdevice_notifiers(NETDEV_CHANGEADDR, hsr_priv->dev);
+		break;
+	case NETDEV_CHANGEMTU:
+		if (dev == hsr_priv->dev)
+			break; /* Handled in ndo_change_mtu() */
+		mtu_max = hsr_get_max_mtu(hsr_priv);
+		if (hsr_priv->dev->mtu > mtu_max)
+			dev_set_mtu(hsr_priv->dev, mtu_max);
+		break;
+	case NETDEV_UNREGISTER:
+		if (dev == hsr_priv->slave[0])
+			hsr_priv->slave[0] = NULL;
+		if (dev == hsr_priv->slave[1])
+			hsr_priv->slave[1] = NULL;
+
+		/* There should really be a way to set a new slave device... */
+
+		break;
+	case NETDEV_PRE_TYPE_CHANGE:
+		/* HSR works only on Ethernet devices. Refuse slave to change
+		 * its type.
+		 */
+		return NOTIFY_BAD;
+	}
+
+	return NOTIFY_DONE;
+}
+
+
+static struct timer_list prune_timer;
+
+static void prune_nodes_all(unsigned long data)
+{
+	struct hsr_priv *hsr_priv;
+
+	rcu_read_lock();
+	list_for_each_entry_rcu(hsr_priv, &hsr_list, hsr_list)
+		hsr_prune_nodes(hsr_priv);
+	rcu_read_unlock();
+
+	prune_timer.expires = jiffies + msecs_to_jiffies(PRUNE_PERIOD);
+	add_timer(&prune_timer);
+}
+
+
+static struct sk_buff *hsr_pull_tag(struct sk_buff *skb)
+{
+	struct hsr_tag *hsr_tag;
+	struct sk_buff *skb2;
+
+	skb2 = skb_share_check(skb, GFP_ATOMIC);
+	if (unlikely(!skb2))
+		goto err_free;
+	skb = skb2;
+
+	if (unlikely(!pskb_may_pull(skb, HSR_TAGLEN)))
+		goto err_free;
+
+	hsr_tag = (struct hsr_tag *) skb->data;
+	skb->protocol = hsr_tag->encap_proto;
+	skb_pull(skb, HSR_TAGLEN);
+
+	return skb;
+
+err_free:
+	kfree_skb(skb);
+	return NULL;
+}
+
+
+/* The uses I can see for these HSR supervision frames are:
+ * 1) Use the frames that are sent after node initialization ("HSR_TLV.Type =
+ *    22") to reset any sequence_nr counters belonging to that node. Useful if
+ *    the other node's counter has been reset for some reason.
+ *    --
+ *    Or not - resetting the counter and bridging the frame would create a
+ *    loop, unfortunately.
+ *
+ * 2) Use the LifeCheck frames to detect ring breaks. I.e. if no LifeCheck
+ *    frame is received from a particular node, we know something is wrong.
+ *    We just register these (as with normal frames) and throw them away.
+ *
+ * 3) Allow different MAC addresses for the two slave interfaces, using the
+ *    MacAddressA field.
+ */
+static bool is_supervision_frame(struct hsr_priv *hsr_priv, struct sk_buff *skb)
+{
+	struct hsr_sup_tag *hsr_stag;
+
+	if (!ether_addr_equal(eth_hdr(skb)->h_dest,
+			      hsr_priv->sup_multicast_addr))
+		return false;
+
+	hsr_stag = (struct hsr_sup_tag *) skb->data;
+	if (get_hsr_stag_path(hsr_stag) != 0x0f)
+		return false;
+	if ((hsr_stag->HSR_TLV_Type != HSR_TLV_ANNOUNCE) &&
+	    (hsr_stag->HSR_TLV_Type != HSR_TLV_LIFE_CHECK))
+		return false;
+	if (hsr_stag->HSR_TLV_Length != 12)
+		return false;
+
+	return true;
+}
+
+
+/* Implementation somewhat according to IEC-62439-3, p. 43
+ */
+static int hsr_rcv(struct sk_buff *skb, struct net_device *dev,
+		   struct packet_type *pt, struct net_device *orig_dev)
+{
+	struct hsr_priv *hsr_priv;
+	struct net_device *other_slave;
+	struct node_entry *node;
+	bool deliver_to_self;
+	struct sk_buff *skb_deliver;
+	enum hsr_dev_idx dev_in_idx, dev_other_idx;
+	bool dup_out;
+	int ret;
+
+	hsr_priv = get_hsr_master(dev);
+
+	if (!hsr_priv) {
+		/* Non-HSR-slave device 'dev' is connected to a HSR network */
+		kfree_skb(skb);
+		dev->stats.rx_errors++;
+		return NET_RX_SUCCESS;
+	}
+
+	if (dev == hsr_priv->slave[0]) {
+		dev_in_idx = HSR_DEV_SLAVE_A;
+		dev_other_idx = HSR_DEV_SLAVE_B;
+	} else {
+		dev_in_idx = HSR_DEV_SLAVE_B;
+		dev_other_idx = HSR_DEV_SLAVE_A;
+	}
+
+	node = hsr_find_node(&hsr_priv->self_node_db, skb);
+	if (node) {
+		/* Always kill frames sent by ourselves */
+		kfree_skb(skb);
+		return NET_RX_SUCCESS;
+	}
+
+	/* Is this frame a candidate for local reception? */
+	deliver_to_self = false;
+	if ((skb->pkt_type == PACKET_HOST) ||
+	    (skb->pkt_type == PACKET_MULTICAST) ||
+	    (skb->pkt_type == PACKET_BROADCAST))
+		deliver_to_self = true;
+	else if (ether_addr_equal(eth_hdr(skb)->h_dest,
+				     hsr_priv->dev->dev_addr)) {
+		skb->pkt_type = PACKET_HOST;
+		deliver_to_self = true;
+	}
+
+
+	rcu_read_lock(); /* node_db */
+	node = hsr_find_node(&hsr_priv->node_db, skb);
+
+	if (is_supervision_frame(hsr_priv, skb)) {
+		skb_pull(skb, sizeof(struct hsr_sup_tag));
+		node = hsr_merge_node(hsr_priv, node, skb, dev_in_idx);
+		if (!node) {
+			rcu_read_unlock(); /* node_db */
+			kfree_skb(skb);
+			hsr_priv->dev->stats.rx_dropped++;
+			return NET_RX_DROP;
+		}
+		skb_push(skb, sizeof(struct hsr_sup_tag));
+		deliver_to_self = false;
+	}
+
+	if (!node) {
+		/* Source node unknown; this might be a HSR frame from
+		 * another net (different multicast address). Ignore it.
+		 */
+		rcu_read_unlock(); /* node_db */
+		kfree_skb(skb);
+		return NET_RX_SUCCESS;
+	}
+
+	/* Register ALL incoming frames as outgoing through the other interface.
+	 * This allows us to register frames as incoming only if they are valid
+	 * for the receiving interface, without using a specific counter for
+	 * incoming frames.
+	 */
+	dup_out = hsr_register_frame_out(node, dev_other_idx, skb);
+	if (!dup_out)
+		hsr_register_frame_in(node, dev_in_idx);
+
+	/* Forward this frame? */
+	if (!dup_out && (skb->pkt_type != PACKET_HOST))
+		other_slave = get_other_slave(hsr_priv, dev);
+	else
+		other_slave = NULL;
+
+	if (hsr_register_frame_out(node, HSR_DEV_MASTER, skb))
+		deliver_to_self = false;
+
+	rcu_read_unlock(); /* node_db */
+
+	if (!deliver_to_self && !other_slave) {
+		kfree_skb(skb);
+		/* Circulated frame; silently remove it. */
+		return NET_RX_SUCCESS;
+	}
+
+	skb_deliver = skb;
+	if (deliver_to_self && other_slave) {
+		/* skb_clone() is not enough since we will strip the hsr tag
+		 * and do address substitution below
+		 */
+		skb_deliver = pskb_copy(skb, GFP_ATOMIC);
+		if (!skb_deliver) {
+			deliver_to_self = false;
+			hsr_priv->dev->stats.rx_dropped++;
+		}
+	}
+
+	if (deliver_to_self) {
+		bool multicast_frame;
+
+		skb_deliver = hsr_pull_tag(skb_deliver);
+		if (!skb_deliver) {
+			hsr_priv->dev->stats.rx_dropped++;
+			goto forward;
+		}
+#if !defined(CONFIG_HAVE_EFFICIENT_UNALIGNED_ACCESS)
+		/* Move everything in the header that is after the HSR tag,
+		 * to work around alignment problems caused by the 6-byte HSR
+		 * tag. In practice, this removes/overwrites the HSR tag in
+		 * the header and restores a "standard" packet.
+		 */
+		memmove(skb_deliver->data - HSR_TAGLEN, skb_deliver->data,
+			skb_headlen(skb_deliver));
+
+		/* Adjust skb members so they correspond with the move above.
+		 * This cannot possibly underflow skb->data since hsr_pull_tag()
+		 * above succeeded.
+		 * At this point in the protocol stack, the transport and
+		 * network headers have not been set yet, and we haven't touched
+		 * the mac header nor the head. So we only need to adjust data
+		 * and tail:
+		 */
+		skb_deliver->data -= HSR_TAGLEN;
+		skb_deliver->tail -= HSR_TAGLEN;
+#endif
+		skb_deliver->dev = hsr_priv->dev;
+		hsr_addr_subst_source(hsr_priv, skb_deliver);
+		multicast_frame = (skb_deliver->pkt_type == PACKET_MULTICAST);
+		ret = netif_rx(skb_deliver);
+		if (ret == NET_RX_DROP) {
+			hsr_priv->dev->stats.rx_dropped++;
+		} else {
+			hsr_priv->dev->stats.rx_packets++;
+			hsr_priv->dev->stats.rx_bytes += skb->len;
+			if (multicast_frame)
+				hsr_priv->dev->stats.multicast++;
+		}
+	}
+
+forward:
+	if (other_slave) {
+		skb_push(skb, ETH_HLEN);
+		skb->dev = other_slave;
+		dev_queue_xmit(skb);
+	}
+
+	return NET_RX_SUCCESS;
+}
+
+
+static struct packet_type hsr_pt __read_mostly = {
+	.type = htons(ETH_P_PRP),
+	.func = hsr_rcv,
+};
+
+static struct notifier_block hsr_nb = {
+	.notifier_call = hsr_netdev_notify,	/* Slave event notifications */
+};
+
+
+static int __init hsr_init(void)
+{
+	int res;
+
+	BUILD_BUG_ON(sizeof(struct hsr_tag) != HSR_TAGLEN);
+
+	dev_add_pack(&hsr_pt);
+
+	init_timer(&prune_timer);
+	prune_timer.function = prune_nodes_all;
+	prune_timer.data = 0;
+	prune_timer.expires = jiffies + msecs_to_jiffies(PRUNE_PERIOD);
+	add_timer(&prune_timer);
+
+	register_netdevice_notifier(&hsr_nb);
+
+	res = hsr_netlink_init();
+
+	return res;
+}
+
+static void __exit hsr_exit(void)
+{
+	unregister_netdevice_notifier(&hsr_nb);
+	del_timer(&prune_timer);
+	hsr_netlink_exit();
+	dev_remove_pack(&hsr_pt);
+}
+
+module_init(hsr_init);
+module_exit(hsr_exit);
+MODULE_LICENSE("GPL");