Re: [dpdk-dev] [PATCH] net/bonding: propagate promiscous mode in mode 4

[Chas Williams <3chas3@gmail.com>]

On Wed, Aug 1, 2018 at 9:48 AM Radu Nicolau <radu.nicolau@intel.com> wrote:

>
>
> On 8/1/2018 2:34 PM, Chas Williams wrote:
>
>
>
> On Wed, Aug 1, 2018 at 9:04 AM Radu Nicolau <radu.nicolau@intel.com>
> wrote:
>
>> Update the bonding promiscuous mode enable/disable functions as to
>> propagate the change to all slaves instead of doing nothing; this
>> seems to be the correct behaviour according to the standard,
>> and also implemented in the linux network stack.
>>
>> Signed-off-by: Radu Nicolau <radu.nicolau@intel.com>
>> ---
>>  drivers/net/bonding/rte_eth_bond_pmd.c | 8 ++------
>>  1 file changed, 2 insertions(+), 6 deletions(-)
>>
>> diff --git a/drivers/net/bonding/rte_eth_bond_pmd.c
>> b/drivers/net/bonding/rte_eth_bond_pmd.c
>> index ad6e33f..16105cb 100644
>> --- a/drivers/net/bonding/rte_eth_bond_pmd.c
>> +++ b/drivers/net/bonding/rte_eth_bond_pmd.c
>> @@ -2617,12 +2617,10 @@ bond_ethdev_promiscuous_enable(struct rte_eth_dev
>> *eth_dev)
>>         case BONDING_MODE_ROUND_ROBIN:
>>         case BONDING_MODE_BALANCE:
>>         case BONDING_MODE_BROADCAST:
>> +       case BONDING_MODE_8023AD:
>>                 for (i = 0; i < internals->slave_count; i++)
>>
>> rte_eth_promiscuous_enable(internals->slaves[i].port_id);
>>                 break;
>> -       /* In mode4 promiscus mode is managed when slave is added/removed
>> */
>>
>
> This comment is true (and it appears it is always on in 802.3ad mode):
>
>         /* use this port as agregator */
>         port->aggregator_port_id = slave_id;
>         rte_eth_promiscuous_enable(slave_id);
>
> If we are going to do this here, we should probably get rid of it in
> the other location so that future readers aren't confused about which
> is the one doing the work.
>
> Since some adapters don't have group multicast support, we might
> already be in promiscuous anyway.  Turning off promiscuous for
> the bonding master might turn it off in the slaves where an application
> has already enabled it.
>
>
> The idea was to preserve the current behavior except for the explicit
> promiscuous disable/enable APIs; an application may disable the promiscuous
> mode on the bonding port and then enable it back, expecting it to propagate
> to the slaves.
>

Yes, but an application doing that will break 802.3ad because promiscuous
mode is used to receive the LAG PDUs which are on a multicast group.
That's why this code doesn't let you disable promiscuous when you are in
802.3ad mode.

If you want to do this it needs to be more complicated.  In 802.3ad, you
should try to add the multicast group to the slave interface.  If that
fails, turn on promisc mode for the slave.  Make note of it.  Later if
bonding wants to enabled/disable promisc mode for the slaves, it needs to
check if that slaves needs to remain in promisc to continue to get the LAG
PDUs.