[Bridge] [PATCH v9 net-next 00/12] Add basic VLAN support to bridges

Stephen Hemminger stephen at networkplumber.org
Thu Feb 7 22:57:55 UTC 2013

On Thu, 07 Feb 2013 17:48:00 -0500
Vlad Yasevich <vyasevic at redhat.com> wrote:

> On 02/04/2013 11:58 AM, Vlad Yasevich wrote:
> > On 02/04/2013 11:24 AM, Stephen Hemminger wrote:
> >> One thing I am not clear about is whether is supposed to be just
> >> a simple filter of VLAN traffic, or a full VLAN aware bridge.
> >
> > I started with the concept of basic VLAN filtering, but it has been
> > morphing into more of a VLAN away bridge.
> >
> >>
> >> The change to make FDB entries per-VLAN seems to be the biggest tipping
> >> point into a full VLAN bridge. I am concerned that might break existing
> >> API's and Spanning Tree (internal and external).
> >>
> >
> > I debated for a while about whether per-VLAN FDB entries were needed.
> > The typing point was that without it, you may end up with flopping FDB
> > and possible packet drops or vlan leaks, if say 2 different VMs used the
> > same MAC but different VLANs.  Without it, there is an exploitable gap.
> >
> > I've also tried to separate FDB code changes as much as possible.  If
> > you really thing this is a big risk and a barrier to entry, then we can
> > drop them.  I am just concerned about the hole I described above, but I
> > guess it is not much different then what's there now.
> >
> So I played with STP for quite a bit and found the FDB changes have 
> absolutely no effect on operation of STP.
> Since all the vlan filtering code is mostly in forwarding path, STP 
> works just fine.
> Looking at STP code (the one in the kernel), I don't see any 
> dependencies on FDB.  The only userspace code I can find is from here
> git://git.kernel.org/pub/scm/linux/kernel/git/shemminger/rstp.git.  That 
> only seems to ask for RTM_GETLINK, and there you will not get any vlan 
> information if you don't set the filter flags.
> So, I don't see any API impact as far as STP is concerned.

Good, does bridge command (in newer iproute2) still work?

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