[3.19.y-ckt stable] Patch "bonding: correct the MAC address for "follow" fail_over_mac policy" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    bonding: correct the MAC address for "follow" fail_over_mac policy

to the linux-3.19.y-queue branch of the 3.19.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.19.y-queue

This patch is scheduled to be released in version 3.19.8-ckt7.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.19.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From 8c3ccb56ffdfc6e299dc86250fb43f93fc14f7f0 Mon Sep 17 00:00:00 2001
From: dingtianhong <dingtianhong at huawei.com>
Date: Thu, 16 Jul 2015 16:30:02 +0800
Subject: bonding: correct the MAC address for "follow" fail_over_mac policy

[ Upstream commit a951bc1e6ba58f11df5ed5ddc41311e10f5fd20b ]

The "follow" fail_over_mac policy is useful for multiport devices that
either become confused or incur a performance penalty when multiple
ports are programmed with the same MAC address, but the same MAC
address still may happened by this steps for this policy:

1) echo +eth0 > /sys/class/net/bond0/bonding/slaves
   bond0 has the same mac address with eth0, it is MAC1.

2) echo +eth1 > /sys/class/net/bond0/bonding/slaves
   eth1 is backup, eth1 has MAC2.

3) ifconfig eth0 down
   eth1 became active slave, bond will swap MAC for eth0 and eth1,
   so eth1 has MAC1, and eth0 has MAC2.

4) ifconfig eth1 down
   there is no active slave, and eth1 still has MAC1, eth2 has MAC2.

5) ifconfig eth0 up
   the eth0 became active slave again, the bond set eth0 to MAC1.

Something wrong here, then if you set eth1 up, the eth0 and eth1 will have the same
MAC address, it will break this policy for ACTIVE_BACKUP mode.

This patch will fix this problem by finding the old active slave and
swap them MAC address before change active slave.

Signed-off-by: Ding Tianhong <dingtianhong at huawei.com>
Tested-by: Nikolay Aleksandrov <nikolay at cumulusnetworks.com>
Signed-off-by: David S. Miller <davem at davemloft.net>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 drivers/net/bonding/bond_main.c | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
index 58b687c..d3b9436 100644
--- a/drivers/net/bonding/bond_main.c
+++ b/drivers/net/bonding/bond_main.c
@@ -622,6 +622,23 @@ static void bond_set_dev_addr(struct net_device *bond_dev,
 	call_netdevice_notifiers(NETDEV_CHANGEADDR, bond_dev);
 }

+static struct slave *bond_get_old_active(struct bonding *bond,
+					 struct slave *new_active)
+{
+	struct slave *slave;
+	struct list_head *iter;
+
+	bond_for_each_slave(bond, slave, iter) {
+		if (slave == new_active)
+			continue;
+
+		if (ether_addr_equal(bond->dev->dev_addr, slave->dev->dev_addr))
+			return slave;
+	}
+
+	return NULL;
+}
+
 /* bond_do_fail_over_mac
  *
  * Perform special MAC address swapping for fail_over_mac settings
@@ -649,6 +666,9 @@ static void bond_do_fail_over_mac(struct bonding *bond,
 		if (!new_active)
 			return;

+		if (!old_active)
+			old_active = bond_get_old_active(bond, new_active);
+
 		if (old_active) {
 			ether_addr_copy(tmp_mac, new_active->dev->dev_addr);
 			ether_addr_copy(saddr.sa_data,
--
1.9.1