netdev - Ethernet-over-UDP virtual network interface

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Message-ID: <CAKLmikOBPB7rTZu2EfK26=3AhOQUR8xg8n4ySUKRMFmBkC1J3g@mail.gmail.com>
Date:	Sun, 4 Mar 2012 12:30:01 +0100
From:	Mitar <mmitar@...il.com>
To:	netdev@...r.kernel.org
Cc:	Nejc Skoberne <nejc@...berne.net>,
	Jernej Kos <kostko@...matrix-one.org>, gw.2012@...de.com
Subject: Ethernet-over-UDP virtual network interface

Hi!

At community wireless network wlan slovenija (http://dev.wlan-si.net/)
we have been using OpenVPN tunnels to connect our WiFi nodes together
over existing Internet infrastructure. After some time of using it we
have discovered throughput problems using a user-land tunneling
solution on those small/consumer Wifi router hardware. Because of the
context switches we cannot get more than 5 Mbit/s even with disabled
encryption. (And as we have a lot of fiber here, it really makes
uplinks unused a lot.)

We found out that we need a really light-weight tunneling solution,
but on a L2 level. The idea is to have a simple encryption-less,
state-less, and session-less L2 tunneling. Some kind of
Ethernet-over-UDP type of virtual interface where we could configure
multiple peer IP address and virtual interface would work as a simple
switch, only instead of cables, it would send packets encapsulated in
UDP (EoIP is not good because many consumer routers do not allow
non-TCP/UDP packets to get through). No session handling, nothing.
Simply, any packets it gets in it is send (based on auto-learned MAC
addresses) to the destination IP address in the UDP packet. On the
other side decapsulated packet is simply output of the virtual
interface there.

I have searched around and have not found anything which would work
like this. Have I missed something? If not, I have decided to write
our own kernel module for this, but first I would like to hear some
feedback from others. Would anybody be interested in developing it
with me or at mentoring me (it would be my first kernel module)?

I have found this code:

https://lwn.net/Articles/199120/

and was planning to use it as a basis, but use UDP for communication.
What is a proper way to do UDP communication from a kernel module?

Best regards and thank you all for the great work you are doing on Linux

Mitar
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