Re: agr(4) + bridge(4): problems!

[Thor Lancelot Simon <tls%panix.com@localhost>]

On Thu, Sep 27, 2012 at 12:59:30PM +0100, Hugo Silva wrote:
> 
> On the host system, ifconfig.agr0 looks like:
> 
> create
> link1
> agrport wm1
> agrport wm4
> up
> inet xxx.xxx.xxx.xxx netmask 255.255.255.0

You don't say which interface you added to the bridge.  I assume it's
agr0, not wm1 nor wm4.

What you may be seeing is an inherent asymmetry of agr in our kernel.
Unless some other interface is stacked on top of the agr, there's really
no reason for packets to be fed to the agr's input routine rather than
passed directly from the underlying hardware's input routine to the
network-layer protocol input routine (usually but not always ip_input).
So -- unless things have changed since last I looked -- that's exactly
what is done.  Packets go _out_ the agr, but they come _in_ the wm
interfaces.  If you attach tcpdump to the agr you may miss all inbound
traffic, and the bridge likely does too.

Even in the case of vlan-on-agr, since most network hardware supports
vlan decapsulation directly it is probably the case that the agr input
routine is bypassed.  Unless my head's gone completely wrong this
morning and I'm thinking of a different kernel.

I have blind-carboned in a former coworker who may remember the awful
details of this better than I do.

But I suspect you're going to have to whack the agr code so that it
tells the underlying interfaces to feed input packets to the bridge, if
one is configured, as well as putting them in promiscuous mode so the
bridge can work at all, or the bridge will never see the packets on
input and this will just never work.  It's a matter of arranging for
the ioctls to flow up and down the stack properly and for the right
thing to happen at the right layer in each case, which for agr input
will be at the physical network interface, not at the agr.

The duplicate address business is because you need to up the interface,
then delete its accursed autoconfigured IPv6 address, before you add it
to the agr, since adding it to the agr produces a MAC address change
which will give the same autoconfigured address to both hosts.  I think
we really need an ifconfig flag to tell the stack *not* to do
autoaddressing on a given interface when it's brought up, but for now,
see:

        http://mail-index.netbsd.org/tech-net/2010/05/06/msg002065.html
        http://mail-index.netbsd.org/tech-net/2010/05/06/msg002066.html

Thor