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Date:	Fri, 5 Dec 2014 23:21:26 +0000
From:	"Arad, Ronen" <ronen.arad@...el.com>
To:	Roopa Prabhu <roopa@...ulusnetworks.com>,
	Scott Feldman <sfeldma@...il.com>,
	Netdev <netdev@...r.kernel.org>
CC:	Jirí Pírko <jiri@...nulli.us>,
	Jamal Hadi Salim <jhs@...atatu.com>,
	Benjamin LaHaise <bcrl@...ck.org>, Thomas Graf <tgraf@...g.ch>,
	john fastabend <john.fastabend@...il.com>,
	"stephen@...workplumber.org" <stephen@...workplumber.org>,
	John Linville <linville@...driver.com>,
	"nhorman@...driver.com" <nhorman@...driver.com>,
	Nicolas Dichtel <nicolas.dichtel@...nd.com>,
	"vyasevic@...hat.com" <vyasevic@...hat.com>,
	Florian Fainelli <f.fainelli@...il.com>,
	"buytenh@...tstofly.org" <buytenh@...tstofly.org>,
	Aviad Raveh <aviadr@...lanox.com>,
	"David S. Miller" <davem@...emloft.net>,
	"shm@...ulusnetworks.com" <shm@...ulusnetworks.com>,
	Andy Gospodarek <gospo@...ulusnetworks.com>
Subject: RE: [PATCH 2/3] bridge: offload bridge port attributes to switch
 asic if feature flag set



> -----Original Message-----
> From: netdev-owner@...r.kernel.org [mailto:netdev-
> owner@...r.kernel.org] On Behalf Of Roopa Prabhu
> Sent: Thursday, December 04, 2014 11:02 PM
> To: Scott Feldman
> Cc: Jiří Pírko; Jamal Hadi Salim; Benjamin LaHaise; Thomas Graf; john
> fastabend; stephen@...workplumber.org; John Linville;
> nhorman@...driver.com; Nicolas Dichtel; vyasevic@...hat.com; Florian
> Fainelli; buytenh@...tstofly.org; Aviad Raveh; Netdev; David S. Miller;
> shm@...ulusnetworks.com; Andy Gospodarek
> Subject: Re: [PATCH 2/3] bridge: offload bridge port attributes to switch asic
> if feature flag set
> 
> On 12/4/14, 10:41 PM, Scott Feldman wrote:
> > On Thu, Dec 4, 2014 at 6:26 PM,  <roopa@...ulusnetworks.com> wrote:
> >> From: Roopa Prabhu <roopa@...ulusnetworks.com>
> >>
> >> 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.
> ok, maybe using the higher bits as in
> https://patchwork.ozlabs.org/patch/413211/
> 
> might help with that. Let me think some more.
> >
> >> ---
> >>   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.
> 
> yeah, i thought about that. But i moved it here so that rollback would be
> easier.

There is a need for propagating setlink/dellink requests down multiple levels.
The use-case I have in mind is a bridge at the top, team/bond in the middle, and port devices at the bottom.
A setlink for VLAN filtering attributes would come with MASTER flag set, and either port or bond/team netdev.
How would this be handled?

The propagation rules between bridge and enslaved port device could be different from those between bond/team and enslaved devices.
The current bridge driver does not propagate VLAN filtering from bridge to its ports as each port could have different configuration. In a case of a bond/team all members need to have the same configuration such that the a bond/team would be indistinguishable from a simple port.

Therefore rtnetlink.c might not have the knowledge for propagation across multiple levels.
It seems that each device which implements ndo_bridge_setlink/ndo_bridge_dellink  and could have master role, need to take care of propagation to its slaves.
 
> >
> >> +               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.
> yep, exactly, I went through the same thought process yesterday when i was
> trying to implement rollback.
> >
> >> +                       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
> >>
> 
> --
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