[ovs-dev] native tunneling bug?

[Pravin Shelar]

On Tue, Sep 1, 2015 at 4:56 PM, Ben Pfaff <blp at nicira.com> wrote:
> I think I've come across a bug in OVS native tunneling, or at any rate
> an important difference between Linux kernel and OVS native tunneling.
> In Linux kernel tunneling, a tunnel packet received by the kernel first
> passes through the kernel IP stack.  Among other things, the IP stack
> drops packets that are not destined to the current host.  It appears to
> me that the native tunneling code doesn't have any similar check,
> because I'm seeing it accept and packets flooded by the upstream switch
> that are not destined to an IP address of the host.  This means in
> effect that the user of native tunneling must set "options:local_ip",
> whereas a user of Linux kernel tunneling doesn't (and probably
> shouldn't).
>
Right. Its bug.

> I suspect that this behavior is unintentional; it isn't mentioned in
> README-native-tunneling.md or (as far as I can tell) anywhere else.
>
> I noticed this while testing OVN.  If you configure a few hypervisors
> and send packets from only one of them, then the switch that connects
> them will flood all the packets to all of the rest (since it hasn't yet
> learned where they are).  The result is that for N hypervisors, remote
> VIFs get N-1 copies of the packets instead of just one.  I'm appending a
> patch that works around it, though I'd prefer to fix the tunneling code
> rather than apply this patch.
>
We can fix it adding the local ip-address to tnl-port-map.
I will send a patch.