netdev - Re: FOU RX interface?

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Message-ID: <CALCETrWb_mmmn7xAj_GsxA5fvREyhK0Bcy1Op=JuQgVr7TuUmg@mail.gmail.com>
Date:	Thu, 2 Oct 2014 08:24:08 -0700
From:	Andy Lutomirski <luto@...capital.net>
To:	Tom Herbert <therbert@...gle.com>
Cc:	Network Development <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: FOU RX interface?

On Thu, Oct 2, 2014 at 7:44 AM, Tom Herbert <therbert@...gle.com> wrote:
> On Wed, Oct 1, 2014 at 10:14 PM, Andy Lutomirski <luto@...capital.net> wrote:
>> Hi-
>>
>> Sorry for the lack of proper threading here -- I lost the original message.
>>
>> If I'm understanding the FOU use case correctly, if I set up a FOU
>> tunnel tun0 that is encapsulated in UDP on eth0, then tun0 packets
>> will be transmitted on tun0, but incoming packets will show up on eth0
>> when they're reinjected after stripping the FOU header.
>>
> Incoming FOU packets will still land on the tunnel interface. In FOU
> RX the UDP packet is removed and logically re-injected into the
> stack-- at this point the packet is IPIP in IP (or sit, GRE) so
> appropriate tunnel protocol processing occurs.
>

Oh, right.  That should have been obvious.  Thanks for the clarification!

--Andy

>> Is this right?  I think that, without a way to reinject the received
>> packets on the tunnel interface, using FOU will be annoying.  For
>> example, writing firewall rules might be tricky.  And programs that
>> use packet sockets or SO_BINDTODEVICE could have a hard time being
>> configured such that they notice the received packets.
>>
> I believe it should work.
>
>> Also, is it even possible to assign a FOU tunnel to a different
>> network namespace than the device that's being tunneled over?  How
>> will the received packets end up in the right netns?
>>
> Anything you can do with IP tunnels, you should be able to with FOU
> enabled IP tunnels. FOU is transparent to IP tunnels on RX.
>
>> --Andy



-- 
Andy Lutomirski
AMA Capital Management, LLC
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