Subject: Re: [PATCH] bonding: Allow tun-interfaces as slaves

From: Ding Tianhong <[email-masked]>
Date: Wed, 10 Aug 2016 09:06:06 +0800

On 2016/8/10 7:51, Jay Vosburgh wrote:
> Jörn Engel <[email-masked]> wrote:
> 
>> On Tue, Aug 09, 2016 at 12:06:36PM -0700, David Miller wrote:
>>>> On Tue, Aug 09, 2016 at 09:28:45PM +0800, Ding Tianhong wrote:
>>>>
>>>> Simply not checking errors when setting the mac address solves the
>>>> problem for me.  No new features needed.
>>>
>>> But it only works in certain modes.
>>>
>>> So the best we can do is enforce the MAC address setting in the
>>> modes that absolutely require it.  We cannot ignore the MAC
>>> address setting unilaterally.
>>
>> Something like this?
>>
>> [PATCH] bonding: Allow tun-interfaces as slaves in balance-rr mode
>>
>> Up until 00503b6f702e (part of 3.14-rc1), the bonding driver could be
>> used to enslave tun-interfaces.  00503b6f702e broke that behaviour,
>> afaics as an unintended side-effect.
>>
>> For the purpose of bond-over-tun in balance-rr mode, simply ignoring the
>> error from dev_set_mac_address() is good enough.
>>
>> Signed-off-by: Joern Engel <[email-masked]>
>> ---
>> drivers/net/bonding/bond_main.c | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
>> index 1f276fa30ba6..2f686bfe4304 100644
>> --- a/drivers/net/bonding/bond_main.c
>> +++ b/drivers/net/bonding/bond_main.c
>> @@ -1490,7 +1490,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>> 		memcpy(addr.sa_data, bond_dev->dev_addr, bond_dev->addr_len);
>> 		addr.sa_family = slave_dev->type;
>> 		res = dev_set_mac_address(slave_dev, &addr);
>> -		if (res) {
>> +		/* round-robin mode works fine without a mac address */
>> +		if (res && BOND_MODE(bond) != BOND_MODE_ROUNDROBIN) {
> 
> 	This will cause balance-rr to add the slave to the bond if any
> device's dev_set_mac_address call fails.
> 
> 	If a bond of regular Ethernet devices is connected to a static
> link aggregation (Etherchannel channel group), a set_mac failure would
> result in that slave having a different MAC address than the bond, which
> in turn would cause traffic inbound from the switch to that slave to be
> dropped (as the destination MAC would not pass the device MAC filters).
> 
> 	The failure check for the set_mac call serves a legitimate
> purpose, and I don't believe we should bypass it without making the
> bypass an option that is explicitly enabled for those special cases that
> need it.
> 
> 	E.g., something like the following (which I have not tested);
> this would also need documentation and iproute2 updates to go with it.
> This would be enabled with "fail_over_mac=keepmac".
> 
> diff --git a/drivers/net/bonding/bond_main.c b/drivers/net/bonding/bond_main.c
> index 1f276fa30ba6..d2283fc23b16 100644
> --- a/drivers/net/bonding/bond_main.c
> +++ b/drivers/net/bonding/bond_main.c
> @@ -1483,7 +1483,8 @@ int bond_enslave(struct net_device *bond_dev, struct net_device *slave_dev)
>  	ether_addr_copy(new_slave->perm_hwaddr, slave_dev->dev_addr);
>  
>  	if (!bond->params.fail_over_mac ||
> -	    BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP) {
> +	    (BOND_MODE(bond) != BOND_MODE_ACTIVEBACKUP &&
> +	     bond->params.fail_over_mac != BOND_FOM_KEEPMAC)) {
>  		/* Set slave to master's mac address.  The application already
>  		 * set the master's mac address to that of the first slave
>  		 */
> diff --git a/drivers/net/bonding/bond_options.c b/drivers/net/bonding/bond_options.c
> index 577e57cad1dc..f9653fe4d622 100644
> --- a/drivers/net/bonding/bond_options.c
> +++ b/drivers/net/bonding/bond_options.c
> @@ -125,6 +125,7 @@ static const struct bond_opt_value bond_fail_over_mac_tbl[] = {
>  	{ "none",   BOND_FOM_NONE,   BOND_VALFLAG_DEFAULT},
>  	{ "active", BOND_FOM_ACTIVE, 0},
>  	{ "follow", BOND_FOM_FOLLOW, 0},
> +	{ "keepmac", BOND_FOM_KEEPMAC, 0},
>  	{ NULL,     -1,              0},
>  };
>  
> diff --git a/include/net/bonding.h b/include/net/bonding.h
> index 6360c259da6d..ec3442b3aa83 100644
> --- a/include/net/bonding.h
> +++ b/include/net/bonding.h
> @@ -420,6 +420,7 @@ static inline bool bond_slave_can_tx(struct slave *slave)
>  #define BOND_FOM_NONE			0
>  #define BOND_FOM_ACTIVE			1
>  #define BOND_FOM_FOLLOW			2
> +#define BOND_FOM_KEEPMAC		3
>  
>  #define BOND_ARP_TARGETS_ANY		0
>  #define BOND_ARP_TARGETS_ALL		1
> 
> 
> 	-J
> 

Hi Jay:

It looks the best solution till now, the user need to ensure the slave don't need the same mac
any more, and no need to checking the ndo_set_mac_address, it looks need more think about this later,
but let we fix it first.

Ding

> ---
> 	-Jay Vosburgh, [email-masked]
> 
> .
>