[PATCH 3/3] ipvlan: set dev_id for l2 ports to generate unique IPv6 addresses

[Konstantin Khlebnikov <khlebnikov@yandex-team.ru>]

All ipvlan ports use one MAC address, this way ipv6 RA tries to assign
one ipv6 address to all of them. This patch assigns unique dev_id to each
ipvlan port. This field is used instead of common FF-FE in Modified EUI-64.

Signed-off-by: Konstantin Khlebnikov <khlebnikov@yandex-team.ru>
---
 Documentation/networking/ipvlan.txt |   12 +++++++++++-
 drivers/net/ipvlan/ipvlan.h         |    1 +
 drivers/net/ipvlan/ipvlan_main.c    |   20 ++++++++++++++++++++
 3 files changed, 32 insertions(+), 1 deletion(-)

diff --git a/Documentation/networking/ipvlan.txt b/Documentation/networking/ipvlan.txt
index cf996394e466..cb0b777bce58 100644
--- a/Documentation/networking/ipvlan.txt
+++ b/Documentation/networking/ipvlan.txt
@@ -24,7 +24,7 @@ using IProute2/ip utility.
 
 	ip link add link <master-dev> <slave-dev> type ipvlan mode { l2 | L3 }
 
-	e.g. ip link add link ipvl0 eth0 type ipvlan mode l2
+	e.g. ip link add link eth0 ipvl0 type ipvlan mode l2
 
 
 4. Operating modes:
@@ -41,6 +41,15 @@ slave device and packets are switched and queued to the master device to send
 out. In this mode the slaves will RX/TX multicast and broadcast (if applicable)
 as well.
 
+	In L2 mode slave devices receive Router Advertisements from the network
+and perform autoconfiguration as well as master device. Each port has unique
+16-bit device id which is used for filling octets 4-5 of Modified EUI-64.
+That gives 65533 addresses (FF-FE used by master, FF-FF/00-00 reserved/not used).
+
+	Also lower half of IPv6 address could be set as interface token:
+
+	ip token set ::aaaa:bbbb:cccc:dddd dev ipvl0
+
 4.2 L3 mode:
 	In this mode TX processing upto L3 happens on the stack instance attached
 to the slave device and packets are switched to the stack instance of the
@@ -105,3 +114,4 @@ namespace where L2 on the slave could be changed / misused.
 			(4) ip -4 addr add 127.0.0.1 dev lo
 			(5) ip -4 addr add $IPADDR dev ipvl1
 			(6) ip -4 route add default via $ROUTER dev ipvl1
+
diff --git a/drivers/net/ipvlan/ipvlan.h b/drivers/net/ipvlan/ipvlan.h
index 54549a6223dd..1ebab84e7a0e 100644
--- a/drivers/net/ipvlan/ipvlan.h
+++ b/drivers/net/ipvlan/ipvlan.h
@@ -95,6 +95,7 @@ struct ipvl_port {
 	struct rcu_head		rcu;
 	int			count;
 	u16			mode;
+	struct ida		ida;
 };
 
 static inline struct ipvl_port *ipvlan_port_get_rcu(const struct net_device *d)
diff --git a/drivers/net/ipvlan/ipvlan_main.c b/drivers/net/ipvlan/ipvlan_main.c
index 0cafd3e6f02d..dee0e8441150 100644
--- a/drivers/net/ipvlan/ipvlan_main.c
+++ b/drivers/net/ipvlan/ipvlan_main.c
@@ -53,6 +53,7 @@ static int ipvlan_port_create(struct net_device *dev)
 	INIT_LIST_HEAD(&port->ipvlans);
 	for (idx = 0; idx < IPVLAN_HASH_SIZE; idx++)
 		INIT_HLIST_HEAD(&port->hlhead[idx]);
+	ida_init(&port->ida);
 
 	err = netdev_rx_handler_register(dev, ipvlan_handle_frame, port);
 	if (err)
@@ -72,6 +73,7 @@ static void ipvlan_port_destroy(struct net_device *dev)
 
 	dev->priv_flags &= ~IFF_IPVLAN_MASTER;
 	netdev_rx_handler_unregister(dev);
+	ida_destroy(&port->ida);
 	kfree_rcu(port, rcu);
 }
 
@@ -484,6 +486,18 @@ static int ipvlan_link_new(struct net *src_net, struct net_device *dev,
 	 */
 	memcpy(dev->dev_addr, phy_dev->dev_addr, ETH_ALEN);
 
+	if (port->mode == IPVLAN_MODE_L2) {
+		/*
+		 * IPv6 addrconf uses it to produce unique addresses,
+		 * see function addrconf_ifid_eui48.
+		 */
+		err = ida_simple_get(&port->ida, 1, 0xFFFE, GFP_KERNEL);
+		if (err > 0)
+			dev->dev_id = err;
+		else if (err != -ENOSPC)
+			goto ipvlan_destroy_port;
+	}
+
 	dev->priv_flags |= IFF_IPVLAN_SLAVE;
 
 	port->count += 1;
@@ -518,6 +532,12 @@ static void ipvlan_link_delete(struct net_device *dev, struct list_head *head)
 			list_del(&addr->anode);
 		}
 	}
+
+	if (dev->dev_id) {
+		ida_simple_remove(&ipvlan->port->ida, dev->dev_id);
+		dev->dev_id = 0;
+	}
+
 	list_del_rcu(&ipvlan->pnode);
 	unregister_netdevice_queue(dev, head);
 	netdev_upper_dev_unlink(ipvlan->phy_dev, dev);