Subject: Re: [PATCH 2/3] bridge: offload bridge port attributes to switch asic if feature flag set

From: John Fastabend <[email-masked]>
Date: Thu, 04 Dec 2014 22:55:04 -0800

On 12/04/2014 10:41 PM, Scott Feldman wrote:
> On Thu, Dec 4, 2014 at 6:26 PM,  <[email-masked]> wrote:
>> From: Roopa Prabhu <[email-masked]>
>>
>> This allows offloading to switch asic without having the user to set
>> any flag. And this is done in the bridge driver to rollback kernel settings
>> on hw offload failure if required in the future.
>>
>> With this, it also makes sure a notification goes out only after the
>> attributes are set both in the kernel and hw.
>
> I like this approach as it streamlines the steps for the user in
> setting port flags.  There is one case for FLOODING where you'll have
> to turn off flooding for both, and then turn on flooding in hw.  You
> don't want flooding turned on on kernel and hw.
>
>> ---
>>   net/bridge/br_netlink.c |   27 ++++++++++++++++++++++++++-
>>   1 file changed, 26 insertions(+), 1 deletion(-)
>>
>> diff --git a/net/bridge/br_netlink.c b/net/bridge/br_netlink.c
>> index 9f5eb55..ce173f0 100644
>> --- a/net/bridge/br_netlink.c
>> +++ b/net/bridge/br_netlink.c
>> @@ -407,9 +407,21 @@ int br_setlink(struct net_device *dev, struct nlmsghdr *nlh)
>>                                  afspec, RTM_SETLINK);
>>          }
>>
>> +       if ((dev->features & NETIF_F_HW_SWITCH_OFFLOAD) &&
>> +                       dev->netdev_ops->ndo_bridge_setlink) {
>> +               int ret = dev->netdev_ops->ndo_bridge_setlink(dev, nlh);
>
> I think you want to up-level this to net/core/rtnetlink.c because
> you're only enabling the feature for one instance of a driver that
> implements ndo_bridge_setlink: the bridge driver.  If another driver
> was MASTER and implemented ndo_bridge_setlink, you'd want same check
> to push setting down to SELF port driver.

Also if the user set SELF && MASTER flags && had HW_SWITCH_OFFLOAD bit
set we would call ndo_bridge_setlink twice on the dev. Maybe you can
catch this case in rtnetlink.c and only call it once.

>
>> +               if (ret && ret != -EOPNOTSUPP) {
>> +                       /* XXX Fix this in the future to rollback
>> +                        * kernel settings and return error
>> +                        */
>
> The future is now.  Let's fix this now for the rollback case (again up
> in rtnetlink.c).  So then a general question comes to mind: for these
> dual target sets, is it best to try HW first and then SW, or the other
> way around?  Either way, on failure on second you need to rollback
> first.  And, on failure, you need to know rollback value for first, so
> you have to do a getlink on first before attempting set.

It might be helpful to return some indication of what object failed as
well.

>
>> +                       br_warn(p->br, "error offloading bridge attributes "
>> +                                       "on port %u(%s)\n", (unsigned int) p->port_no,
>> +                                       p->dev->name);
>> +               }
>> +       }
>> +
>>          if (err == 0)
>>                  br_ifinfo_notify(RTM_NEWLINK, p);
>> -
>>   out:
>>          return err;
>>   }
>> @@ -433,6 +445,19 @@ int br_dellink(struct net_device *dev, struct nlmsghdr *nlh)
>>          err = br_afspec((struct net_bridge *)netdev_priv(dev), p,
>>                          afspec, RTM_DELLINK);
>>
>> +       if (dev->features & NETIF_F_HW_SWITCH_OFFLOAD
>> +                       && dev->netdev_ops->ndo_bridge_setlink) {
>> +               int ret = dev->netdev_ops->ndo_bridge_dellink(dev, nlh);
>> +               if (ret && ret != -EOPNOTSUPP) {
>> +                       /* XXX Fix this in the future to rollback
>> +                        * kernel settings and return error
>> +                        */
>> +                       br_warn(p->br, "error offloading bridge attributes "
>> +                                       "on port %u(%s)\n", (unsigned int) p->port_no,
>> +                                       p->dev->name);
>> +               }
>> +       }
>> +
>
> Same comments as setlink above.
>
>>          return err;
>>   }
>>   static int br_validate(struct nlattr *tb[], struct nlattr *data[])
>> --
>> 1.7.10.4
>>

-- 
John Fastabend         Intel Corporation