Documentation/networking/l2tp.txt

49 Each L2TP tunnel is implemented using a UDP or L2TPIP socket; L2TPIP
51 new l2tpip socket family. The tunnel socket is typically created by
52 userspace, though for unmanaged L2TPv3 tunnels, the socket can also be
55 indirectly by pppd using a pppol2tp socket. In the case of ethernet,
85 socket. The session context holds data that lets the driver interface
94 1. Use a UDP socket per tunnel.
96 2. Create a single PPPoL2TP socket per tunnel bound to a special null
99    management socket causes the driver to mark the tunnel socket as an
100    L2TP UDP encapsulation socket and flags it for use by the
103    in this special PPPoX socket.
105 3. Create a PPPoL2TP socket per L2TP session. This is typically done
107    arguments. A PPPoL2TP tunnel management socket (Step 2) must be
108    created before the first PPPoL2TP session socket is created.
111 to the driver about the socket in a socket connect() call. Source and
113 descriptor of a UDP socket. See struct pppol2tp_addr in
116 socket in Step 2 above, zero source and destination session ids are
118 descriptor for use as an L2TP tunnel socket.
121 setsockopt and ioctl on the PPPoX socket. The following socket
134 PPPoX socket.
138 PPPoX socket of the appropriate tunnel or session.
144 1. Open a GENL socket using L2TP_GENL_NAME for configuring the kernel
147 2. Create a UDP or L2TPIP socket for the tunnel.
151    referencing the UDP or L2TPIP socket created in the previous step.
156 The tunnel and all of its sessions are closed when the tunnel socket
164 case -- the tunnel socket is created by the kernel and configured
176 setsockopt on the PPPoX socket to set a debug mask.
251 1. Create tunnel management PPPoX socket
253         kernel_fd = socket(AF_PPPOX, SOCK_DGRAM, PX_PROTO_OL2TP);
262                 sax.pppol2tp.fd = udp_fd;       /* fd of tunnel UDP socket */
267                 sax.pppol2tp.s_session = 0;     /* special case: mgmt socket */
269                 sax.pppol2tp.d_session = 0;     /* special case: mgmt socket */
278 2. Create session PPPoX data socket
283         /* Note, the target socket must be bound already, else it will not be ready */
295         /* session_fd is the fd of the session's PPPoL2TP socket.
296          * tunnel_fd is the fd of the tunnel UDP socket.
309 always associated with a UDP or L2TP/IP socket and keeps a list of
317 When a tunnel is first opened, the reference count on the socket is
318 increased using sock_hold(). This ensures that the kernel socket
321 Some L2TP sessions also have a socket (PPP pseudowires) while others
322 do not (ethernet pseudowires). We can't use the socket reference count