netdev - Re: [RFC] iproute2: add br command

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Date:	Wed, 05 Oct 2011 16:00:14 -0700
From:	Sridhar Samudrala <sri@...ibm.com>
To:	Stephen Hemminger <shemminger@...tta.com>
Cc:	netdev <netdev@...r.kernel.org>,
	John Fastabend <john.r.fastabend@...el.com>
Subject: Re: [RFC] iproute2: add br command

On Wed, 2011-10-05 at 08:58 -0700, Stephen Hemminger wrote:
> On Tue, 04 Oct 2011 22:08:15 -0700
> Sridhar Samudrala <sri@...ibm.com> wrote:
> 
> > 
> > On Tue, 2011-10-04 at 16:00 -0700, Stephen Hemminger wrote:
> > > On Tue, 04 Oct 2011 15:54:07 -0700
> > > Sridhar Samudrala<sri@...ibm.com  <mailto:sri@...ibm.com>>  wrote:
> > >
> > > >  On Tue, 2011-10-04 at 15:42 -0700, Stephen Hemminger wrote:
> > > >  >  On Wed, 5 Oct 2011 00:32:31 +0200
> > > >  >  Michał Mirosław<mirqus@...il.com  <mailto:mirqus@...il.com>>  wrote:
> > > >  >
> > > >  >  >  2011/10/5 Sridhar Samudrala<sri@...ibm.com  <mailto:sri@...ibm.com>>:
> > > >  >  >  >  On Tue, 2011-10-04 at 14:07 -0700, Stephen Hemminger wrote:
> > > >  >  >  >>  On Tue, 04 Oct 2011 09:58:55 -0700
> > > >  >  >  >>  Andi Kleen<andi@...stfloor.org  <mailto:andi@...stfloor.org>>  wrote:
> > > >  >  >  >>  >  Stephen Hemminger<shemminger@...tta.com  <mailto:shemminger@...tta.com>>  writes:
> > > >  >  >  >>  >  >  This adds a new 'br' command which is the bridging equivalent of
> > > >  >  >  >>  >  >  the ip command. More of a demo of how to use netlink and bridging
> > > >  >  >  >>  >  >  at this point.
> > > >  >  >  >>  >  Please name it "bridge", not "br"
> > > >  >  >  >>  Ok, but it breaks the existing pattern.
> > > >  >  >  >  Is this supposed to replace brctl utility?
> > > >  >  >  >
> > > >  >  >  >  Can we add/delete a bridge and add/delete interfaces to a bridge using
> > > >  >  >  >  this command?
> > > >  >  >  >
> > > >  >  >  >  If so, why not make it
> > > >  >  >  >    ip bridge add/del<brname>
> > > >  >  >  >    ip bridge addif/delif<brname>  <ifname>
> > > >  >  >
> > > >  >  >  I'll add one more idea:
> > > >  >  >
> > > >  >  >  ip link add/del<brname>  type bridge
> > > >  >  >  ip bridge add/del<brname>  <ifname>
> > > >  >  >  ip bridge fdb ...
> > > >  >
> > > >  >  In 3.0 you can already do:
> > > >  >  # ip link add dev br3 type bridge
> > This is a new syntax that i think works only for 'bridge' type.
> 
> 
> The bridge interface to 'ip link' is nothing special. The same syntax
> is available for macvlan, vlan, and bonding.
> 
> 
> > All other types require a prefix 'ip link add link'
> 
> 
> 
> For vlan:
>   ip link add link eth0 name eth0.1 type vlan id 1
> 
> The reason there is no 'link' parameter when creating a bridge is that
> the bridge is a standalone device it is not slaved to an underlying
> device.
> 
> > 
> > I think the ip command help text should be updated to include this syntax.
> 
> 
> patches accepted...

Will submit soon.
> 
> > 
> > > >  >  # ip link set dev eth3 master br3
> > 
> > looks like the command to delete an interface from a bridge is
> >        ip link set dev eth3 nomaster
> > 
> > Somehow this interface doesn't look all that intuitive.
> 
> Propose something better. 

Add eth3 to br3
ip link add link br3 [name] eth3 type brif

Delete eth3 from br3
ip link del link br3 [name] eth3 type brif

> 
> 
> > Currently we have 'ip route' and 'ip neigh' to manipulate routing and
> > neighbor entry tables. I think 'ip bridge' would be good way to extend
> > this to support bridging.
> > 
> > If it is not too late, can we have a interface where all bridge related
> > commands can be done using the same prefix.
> > 
> > I think we also should think about how this syntax can be extended to show
> > embedded bridges in SR-IOV NICs.
> 
> The iproute2 commands in general try to be as close to the
> underlying netlink protocol. This makes it less user friendly but smaller,
> easier to program. The only part of bridging that is special is the
> forwarding database which is similar to the neighbor table.
> If I do merge bridging into ip, it would not be as 'ip bridge' but as
> another protocol family.
> 
>    ip -family bridge neigh ...

OK. I am not too familiar with the internal implementation details.
So i guess this may not be as straightforward as i thought.

Thanks
Sridhar


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