l2tp: Add L2TPv3 protocol support

The L2TPv3 protocol changes the layout of the L2TP packet
header. Tunnel and session ids change from 16-bit to 32-bit values,
data sequence numbers change from 16-bit to 24-bit values and PPP-specific
fields are moved into protocol-specific subheaders.

Although this patch introduces L2TPv3 protocol support, there are no
userspace interfaces to create L2TPv3 sessions yet.

Signed-off-by: James Chapman <jchapman@katalix.com>
Reviewed-by: Randy Dunlap <randy.dunlap@oracle.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

1 files changed, 25 insertions, 0 deletions

diff --git a/net/l2tp/Kconfig b/net/l2tp/Kconfig
index ec88c5cdc397..d60758d60478 100644
--- a/net/l2tp/Kconfig
+++ b/net/l2tp/Kconfig
@@ -19,6 +19,10 @@ menuconfig L2TP
           connections. L2TP is also used as a VPN protocol, popular
           with home workers to connect to their offices.
 
+          L2TPv3 allows other protocols as well as PPP to be carried
+          over L2TP tunnels. L2TPv3 is defined in RFC 3931
+          <http://www.ietf.org/rfc/rfc3931.txt>.
+
           The kernel component handles only L2TP data packets: a
           userland daemon handles L2TP the control protocol (tunnel
           and session setup). One such daemon is OpenL2TP
@@ -26,3 +30,24 @@ menuconfig L2TP
 
           If you don't need L2TP, say N. To compile all L2TP code as
           modules, choose M here.
+
+config L2TP_V3
+        bool "L2TPv3 support (EXPERIMENTAL)"
+        depends on EXPERIMENTAL && L2TP
+        help
+          Layer Two Tunneling Protocol Version 3
+
+          From RFC 3931 <http://www.ietf.org/rfc/rfc3931.txt>.
+
+          The Layer Two Tunneling Protocol (L2TP) provides a dynamic
+          mechanism for tunneling Layer 2 (L2) "circuits" across a
+          packet-oriented data network (e.g., over IP).  L2TP, as
+          originally defined in RFC 2661, is a standard method for
+          tunneling Point-to-Point Protocol (PPP) [RFC1661] sessions.
+          L2TP has since been adopted for tunneling a number of other
+          L2 protocols, including ATM, Frame Relay, HDLC and even raw
+          ethernet frames.
+
+          If you are connecting to L2TPv3 equipment, or you want to
+          tunnel raw ethernet frames using L2TP, say Y here. If
+          unsure, say N.