netdev - Re: FOU RX interface?

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Date:	Thu, 2 Oct 2014 07:44:55 -0700
From:	Tom Herbert <therbert@...gle.com>
To:	Andy Lutomirski <luto@...capital.net>
Cc:	Network Development <netdev@...r.kernel.org>,
	"David S. Miller" <davem@...emloft.net>
Subject: Re: FOU RX interface?

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.

> 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
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