Subject: Re: [PATCH] bonding: correct the MAC address for "follow" fail_over_mac policy

From: Nikolay Aleksandrov <[email-masked]>
Date: Thu, 16 Jul 2015 13:54:28 +0200

On 07/16/2015 01:50 PM, Nikolay Aleksandrov wrote:
> On 07/16/2015 01:48 PM, Ding Tianhong wrote:
>> On 2015/7/16 17:24, Nikolay Aleksandrov wrote:
>>> On 07/16/2015 10:30 AM, Ding Tianhong wrote:
>>>> 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 <[email-masked]>
>>>> ---
>>>>  drivers/net/bonding/bond_main.c | 20 ++++++++++++++++++++
>>>>  1 file changed, 20 insertions(+)
>>>>
>>>
>>> This doesn't seem to be true:
>>> ~# cat /sys/class/net/bond0/bonding/fail_over_mac 
>>> follow 2
>>> root@debian:~# ip l sh eth1
>>> 3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>> root@debian:~# ip l sh eth2
>>> 4: eth2: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:4f:a5:99 brd ff:ff:ff:ff:ff:ff
>>> root@debian:~# ip l sh bond0
>>> 26: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>>
>>> *eth1 is the first and active slave and bond0 has taken its mac.
>>> Now trying your steps:
>>> Step 3) (bringing down the active eth1)
>>> root@debian:~# ip l set eth1 down
>>> root@debian:~# ip l sh bond0
>>> 26: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>> root@debian:~# ip l sh eth1
>>> 3: eth1: <BROADCAST,MULTICAST,SLAVE> mtu 1500 qdisc pfifo_fast master bond0 state DOWN mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:4f:a5:99 brd ff:ff:ff:ff:ff:ff
>>> root@debian:~# ip l sh eth2
>>> 4: eth2: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>>
>>> *The mac addresses of eth1 and eth2 are correctly swapped, so far so good.
>>>
>>> Step 4) (bringing down the active eth2)
>>> root@debian:~# ip l set eth2 down
>>> 3: eth1: <BROADCAST,MULTICAST,SLAVE> mtu 1500 qdisc pfifo_fast master bond0 state DOWN mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:4f:a5:99 brd ff:ff:ff:ff:ff:ff
>>> 4: eth2: <BROADCAST,MULTICAST,SLAVE> mtu 1500 qdisc pfifo_fast master bond0 state DOWN mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>> 26: bond0: <NO-CARRIER,BROADCAST,MULTICAST,MASTER,UP> mtu 1500 qdisc noqueue state DOWN mode DEFAULT group default 
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>>
>>> *eth2 has kept the mac address of the bond and they're both down now
>>>
>>> Step 5) (bring eth1 up again and observe the macs)
>>> ~# ip l set eth1 up
>>> 3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>> 4: eth2: <BROADCAST,MULTICAST,SLAVE> mtu 1500 qdisc pfifo_fast master bond0 state DOWN mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:4f:a5:99 brd ff:ff:ff:ff:ff:ff
>>> 26: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>>
>>> *The macs are correctly swapped and there's no such bug. 
>>>
>>> Step 6(?) bring eth2 up
>>> ~# ip l set eth2 up
>>> 3: eth1: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>> 4: eth2: <BROADCAST,MULTICAST,SLAVE,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master bond0 state UP mode DEFAULT group default qlen 1000
>>>     link/ether 52:54:00:4f:a5:99 brd ff:ff:ff:ff:ff:ff
>>> 26: bond0: <BROADCAST,MULTICAST,MASTER,UP,LOWER_UP> mtu 1500 qdisc noqueue state UP mode DEFAULT group default 
>>>     link/ether 52:54:00:3f:47:69 brd ff:ff:ff:ff:ff:ff
>>>
>>> *Still correct.
>>>
>>> Also the mac address that gets set is dev_addr which is changed when
>>> the swapping is done, if you'd like to get the original mac address
>>> you should be using slave->perm_hwaddr.
>>>
>>
>> Hi Nik:
>>
>> Which kernel version do you use, I test this on kernel 3.19.8 and 4.2-rc2, this problem exist on both version,
>> maybe I miss something?
>>
>> Ding
>>
>>
> 
> It's current net-next.
> ~# uname -a
> Linux debian 4.2.0-rc2+ #8 SMP Wed Jul 15 21:22:14 CEST 2015 x86_64 GNU/Linux
> 

Ah this is my bad, my setup was polluted from previous tests and the bonding wasn't
clean, you're right - this does reproduce.
Sorry about that

>>> Cheers,
>>>  Nik
>>> .