[ovs-discuss] ARP Behavior in XenServer Host

[Ben Pfaff]

On Thu, Sep 08, 2011 at 06:11:39PM -0700, David Erickson wrote:
> Hi All-
> I'm seeing some confusing behavior happening relating to ARPs and
> OVS 1.2.1 (also on 1.1.1 and probably 1.0.1). This is a XS machine
> with 1 ethernet port, so in-band connection from OVS to the
> controller. Specifically there are two cases where I would expect
> packets to be sent up to the connected controller, but they aren't:

By "sent up", do you mean "forwarded like an Ethernet switch" or "sent
as OpenFlow packet-out messages"?

> 1- VLAN Tagged ARP replies coming in eth0, attached as tagged_arp.pcap

I think that these match in-band rule (b).  (The in-band control rules
that OVS sets up wildcard the VLAN field.  We've never really thought
that through, though.)

> 2- Gratuitous ARPs sent from the XS host, eg: /sbin/arping -U -c 1
> -I xenbr0 -s 10.0.2.5 255.255.255.255, attached as
> gratuitous_arp.pcap

I think that these match in-band rule (c) described in DESIGN, so I'm
surprised that these don't get forwarded.

> Also is there a document that specifies OVSs behavior in in-band
> environments such as XS with one ethernet port?  I would expect
> after the controller is connected that all packets coming in/out
> other than the controller connection (and possibly ARPs towards the
> controller ip/gateway?) should flow through the
> flowtable/controller, but maybe my expectation is incorrect.

See DESIGN and ofproto/in-band.c.  Feel free to ask questions and we
will try clarify what they say.