[RFC PATCH 0/8] l2tp: introduce L2TPv3 support

[James Chapman <jchapman@katalix.com>]

This patch series implements L2TPv3. It replaces the existing pppol2tp
driver with a number of separate drivers, namely:-

l2tp_core    - L2TP driver core. Always required.
l2tp_ppp     - L2TP PPP
l2tp_eth     - L2TPv3 ethernet pseudowire
l2tp_ip      - L2TPv3 IP encapsulation
l2tp_netlink - L2TPv3 netlink API

The combination of l2tp_core and l2tp_ppp provides
backwards-compatible L2TPv2 pppol2tp functionality.

Except for Patch 6, these patches are not yet ready for the mainline
so don't have my signed-off-by sig. Recently added pppol2tp features
such as namespace support are still to be merged in. I am posting the
patches early to get some feedback before I spend too long
testing. The code is working in basic test setups.

The implementation is as I described in a previous posting to netdev,
archived at http://marc.info/?l=linux-netdev&m=120845482320143&w=4.

The patches are:-

1. Move the existing L2TPv2 pppol2tp driver from drivers/net into a
   new directory, net/l2tp.

2. Split the pppol2tp driver into separate L2TP and PPP parts. This
   is required for L2TPv3 since L2TPv3 can carry protocols other than
   PPP.

3. Add L2TPv3 core protocol support.

4. Update PPP-over-L2TP driver to work over L2TPv3.

5. Add L2TPv3 IP encapsulation (no UDP) support. This creates a new
   L2TPIP socket family. Userspace uses an L2TPIP socket instead of a
   UDP socket when IP encapsulation is required.

6. Small change to genetlink core to export genl_lock/genl_unlock.

7. Add userspace API for L2TPv3 using netlink. Userspace must manage
   L2TPv3 kernel tunnel/session configuration using netlink. The
   previous pppol2tp driver was managed using [gs]etsockopt(), which
   is retained for backwards compatibility. Netlink is used for L2TPv3
   because it is more flexible and the L2TPv3 kernel interface is
   quite complex.

8. Add ethernet pseudowire support. Each ethernet pseudowire has a
   net_device which may be managed by userspace tools.

--
James Chapman
Katalix Systems Ltd
http://www.katalix.com
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