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36 .\" Author: Archie Cobbs <archie@freebsd.org>
38 .\" $FreeBSD: src/share/man/man4/ng_l2tp.4,v 1.1.2.1 2002/08/20 23:48:53 archie Exp $
39 .\" $DragonFly: src/share/man/man4/ng_l2tp.4,v 1.8 2007/11/21 19:12:41 swildner Exp $
46 .Nd L2TP protocol netgraph node type
48 .In netgraph/l2tp/ng_l2tp.h
52 node type implements the encapsulation layer of the L2TP protocol
53 as described in RFC 2661.
54 This includes adding the L2TP packet header for outgoing packets
55 and verifying and removing it for incoming packets.
56 The node maintains the L2TP sequence number state and handles
57 control session packet acknowledgment and retransmission.
61 node type supports the following hooks:
63 .Bl -tag -compact -offset 3n -width session_hhhh
69 Session 0xhhhh data packets
72 L2TP control and data packets are transmitted to, and received from,
76 Typically this hook would be connected to the
80 node for L2TP over UDP.
84 hook connects to the local L2TP management entity.
85 L2TP control messages (without any L2TP headers) are transmitted
86 and received on this hook.
87 Messages written to this hook are guaranteed to be delivered to the
88 peer reliably, in order, and without duplicates.
90 Packets written to the
92 hook must contain a two byte session ID prepended to the frame
94 This session ID is copied to the outgoing L2TP header.
95 Similarly, packets read from the
97 hook will have the received session ID prepended.
99 Once an L2TP session has been created, the corresponding session
100 hook may be used to transmit and receive the session's data frames:
101 for the session with session ID
106 This node type supports the generic control messages, plus the following:
108 .It Dv NGM_L2TP_SET_CONFIG
109 This command updates the configuration of the node.
111 .Li "struct ng_l2tp_config"
113 .Bd -literal -offset 0n
114 /* Configuration for a node */
115 struct ng_l2tp_config {
116 u_char enabled; /* enables traffic flow */
117 u_char match_id; /* tunnel id must match 'tunnel_id' */
118 u_int16_t tunnel_id; /* local tunnel id */
119 u_int16_t peer_id; /* peer's tunnel id */
120 u_int16_t peer_win; /* peer's max recv window size */
121 u_int16_t rexmit_max; /* max retransmits before failure */
122 u_int16_t rexmit_max_to; /* max delay between retransmits */
128 field enables packet processing.
129 Each time this field is changed back to zero the sequence
130 number state is reset. In this way, reuse of a node is possible.
134 field configures the local tunnel ID for the control connection.
137 field determines how incoming L2TP packets with a tunnel ID
143 is non-zero, they will be dropped; otherwise, they will be dropped
144 only if the tunnel ID is non-zero.
147 is set to the local tunnel ID as soon as it is known and
149 is set to non-zero after receipt of the SCCRP or SCCCN control message.
151 The peer's tunnel ID should be set in
153 as soon as it is learned, typically after receipt of a SCCRQ or SCCRP
155 This value is copied into the L2TP header for outgoing packets.
159 field should be set from the
160 .Dq Receive Window Size
161 AVP received from the peer.
162 The default value for this field is one; zero is an invalid value.
165 is non-zero, this value may not be decreased.
171 fields configure packet retransmission.
173 is the maximum retransmission delay between packets, in seconds.
174 The retransmit delay will start at a small value and increase
175 exponentially up to this limit.
178 sets the maximum number of times a packet will be retransmitted
179 without being acknowledged before a failure condition is declared.
180 Once a failure condition is declared, each additional retransmission
184 .Dv NGM_L2TP_ACK_FAILURE
185 control message back to the node that sent the last
186 .Dv NGM_L2TP_SET_CONFIG .
187 Appropriate action should then be taken to shutdown the control connection.
188 .It Dv NGM_L2TP_GET_CONFIG
189 Returns the current configuration as a
190 .Dv "struct ng_l2tp_config" .
191 .It Dv NGM_L2TP_SET_SESS_CONFIG
192 This control message configures a single data session.
193 The corresponding hook must already be connected before sending this command.
195 .Li "struct ng_l2tp_sess_config" :
196 .Bd -literal -offset 0n
197 /* Configuration for a session hook */
198 struct ng_l2tp_sess_config {
199 u_int16_t session_id; /* local session id */
200 u_int16_t peer_id; /* peer's session id */
201 u_char control_dseq; /* we control data sequencing? */
202 u_char enable_dseq; /* enable data sequencing? */
203 u_char include_length; /* include length field? */
211 fields configure the local and remote session ID's, respectively.
217 fields determine whether sequence numbers are used with L2TP data packets.
220 is zero, then no sequence numbers are sent and incoming sequence numbers
222 Otherwise, sequence numbers are included on outgoing packets and checked
227 is non-zero, then the setting of
229 will never change except by another
230 .Dv NGM_L2TP_SET_SESS_CONFIG
234 is zero, then the peer controls whether sequence numbers are used:
235 if an incoming L2TP data packet contains sequence numbers,
237 is set to one, and conversely if an incoming L2TP data packet does not
238 contain sequence numbers,
243 is always accessible via the
244 .Dv NGM_L2TP_GET_SESS_CONFIG
245 control message (see below).
246 Typically an LNS would set
248 to one while a LAC would set
250 to zero (if the Sequencing Required AVP were not sent), thus giving
251 control of data packet sequencing to the LNS.
255 field determines whether the L2TP header length field is included
256 in outgoing L2TP data packets.
257 For incoming packets, the L2TP length field is always checked when present.
258 .It Dv NGM_L2TP_GET_SESS_CONFIG
259 This command takes a two byte session ID as an argument and returns
260 the current configuration for the corresponding data session as a
261 .Dv "struct ng_l2tp_sess_config" .
262 The corresponding session hook must be connected.
263 .It Dv NGM_L2TP_GET_STATS
264 This command takes a two byte session ID as an argument and returns a
265 .Dv "struct ng_l2tp_stats"
266 containing statistics for the corresponding data session.
267 The corresponding session hook must be connected.
268 .It Dv NGM_L2TP_CLR_STATS
269 This command takes a two byte session ID as an argument and
270 clears the statistics for that data session.
271 The corresponding session hook must be connected.
272 .It Dv NGM_L2TP_GETCLR_STATS
274 .Dv NGM_L2TP_GET_STATS ,
275 but also atomically clears the statistics as well.
278 This node shuts down upon receipt of a
280 control message, or when all hooks have been disconnected.
294 .%T "Layer Two Tunneling Protocol L2TP"
300 node type was developed at Packet Design, LLC.
301 .Pa "http://www.packetdesign.com/"
303 .An Archie Cobbs Aq archie@packetdesign.com