57 Tunnel Sockets
117 sockets are used to implement unmanaged L2TPv3 tunnels (iproute2's "ip
204 onto the new session. This is covered in "PPPoL2TP Sockets" later.
357 When creating PPPoL2TP sockets, the application provides information
421 only PPPoL2TP sockets. The PPPoL2TP socket is used as described in
491 Sockets  section in Internal Implementation
494 UDP sockets are implemented by the networking core. When an L2TP
501 L2TPIP sockets are implemented in `net/l2tp/l2tp_ip.c`_ and
527 socket. For UDP sockets, when userspace closes the tunnel socket, the
529 its tunnel close actions. For L2TPIP sockets, the socket's close
641   1) Multiple UDP sockets with the same 5-tuple address cannot be