[ovs-discuss] Small 802.1q-prepended packets not getting through to VM

[Steinar H. Gunderson]

On Tue, Jun 11, 2019 at 03:00:00PM -0700, Gregory Rose wrote:
> I see the source of the confusion here.  The vlan1 interface is added to the
> OVS bridge and the port type
> is internal.  Here's a better way to look at this:
> 
>       Net Device
> <Can originate packets>              OVS switch
> |------------------|             |-----------------|
> |                  |             |                 |
> |       vlan1      |<----------->|      ovsbr1     |
> |                  |     ^       |                 |
> |------------------|     |       |-----------------|
>                          |
>                          |
>                    <internal port> <----------------- Think of that as a
> virtual Ethernet cable
> 
> When you ssh to a destination via the vlan1 interface then the vlan1
> interface is generating the packets.  If it has a tcp checksum offload
> capability then it would use it but that will depend on the master device
> it is controlled by.  This port is in no way owned by OVS.  OVS has simply
> added it to the bridge using a virtual port which is by convention called
> an 'internal' port.  But think of it as the cable connecting your virtual
> device 'vlan1' to the OVS bridge 'ovsbr1'.
> 
> Does that help explain?

Only if you can tell me what the vlan1 device is. :-) I had assumed this was
a first-class concept within ovs; after all, when you create a bridge you get
one of these.

It's created with Debian's ifupdown integration (an “OVSIntPort”-type
interface), which seems to do:

                ovs_vsctl -- --may-exist add-port "${IF_OVS_BRIDGE}"\
                    "${IFACE}" ${IF_OVS_OPTIONS} -- set Interface "${IFACE}"\
                    type=internal ${OVS_EXTRA+-- $OVS_EXTRA}

> No, the internal ports are the virtual interfaces between physical/virtual
> devices (vlan1) and the OVS bridge (ovsbr1).

So what are the vlan1 devices? Who should I nag to get them to pad their
packets correctly? :-)

/* Steinar */
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