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36 .\" Author: Archie Cobbs <archie@FreeBSD.org>
45 .Nd L2TP protocol netgraph node type
48 .In netgraph/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:
62 .Bl -tag -width ".Va session_hhhh"
68 Session 0xhhhh data packets.
71 L2TP control and data packets are transmitted to, and received from,
75 Typically this hook would be connected to the
79 node for L2TP over UDP.
83 hook connects to the local L2TP management entity.
84 L2TP control messages (without any L2TP headers) are transmitted
85 and received on this hook.
86 Messages written to this hook are guaranteed to be delivered to the
87 peer reliably, in order, and without duplicates.
89 Packets written to the
91 hook must contain a two byte session ID prepended to the frame
93 This session ID is copied to the outgoing L2TP header.
94 Similarly, packets read from the
96 hook will have the received session ID prepended.
98 Once an L2TP session has been created, the corresponding session
99 hook may be used to transmit and receive the session's data frames:
100 for the session with session ID
105 This node type supports the generic control messages, plus the following:
107 .It Dv NGM_L2TP_SET_CONFIG Pq Ic setconfig
108 This command updates the configuration of the node.
110 .Vt "struct ng_l2tp_config"
113 /* Configuration for a node */
114 struct ng_l2tp_config {
115 u_char enabled; /* enables traffic flow */
116 u_char match_id; /* tunnel id must match 'tunnel_id' */
117 uint16_t tunnel_id; /* local tunnel id */
118 uint16_t peer_id; /* peer's tunnel id */
119 uint16_t peer_win; /* peer's max recv window size */
120 uint16_t rexmit_max; /* max retransmits before failure */
121 uint16_t rexmit_max_to; /* max delay between retransmits */
127 field enables packet processing.
128 Each time this field is changed back to zero the sequence
129 number state is reset.
130 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 Pq Ic ackfailure
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 Pq Ic getconfig
189 Returns the current configuration as a
190 .Vt "struct ng_l2tp_config" .
191 .It Dv NGM_L2TP_SET_SESS_CONFIG Pq Ic setsessconfig
192 This control message configures a single data session.
193 The corresponding hook must already be connected before sending this command.
195 .Vt "struct ng_l2tp_sess_config" :
197 /* Configuration for a session hook */
198 struct ng_l2tp_sess_config {
199 uint16_t session_id; /* local session id */
200 uint16_t peer_id; /* peer's session id */
201 u_char control_dseq; /* whether we control data sequencing */
202 u_char enable_dseq; /* whether to enable data sequencing */
203 u_char include_length; /* whether to include length field */
211 fields configure the local and remote session IDs, 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 Pq Ic getsessconfig
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 .Vt "struct ng_l2tp_sess_config" .
262 The corresponding session hook must be connected.
263 .It Dv NGM_L2TP_GET_STATS Pq Ic getstats
264 This command returns a
265 .Vt "struct ng_l2tp_stats"
266 containing statistics of the L2TP tunnel.
267 .It Dv NGM_L2TP_CLR_STATS Pq Ic clrstats
268 This command clears the statistics for the L2TP tunnel.
269 .It Dv NGM_L2TP_GETCLR_STATS Pq Ic getclrstats
271 .Dv NGM_L2TP_GET_STATS ,
272 but also atomically clears the statistics as well.
273 .It Dv NGM_L2TP_GET_SESSION_STATS Pq Ic getsessstats
274 This command takes a two byte session ID as an argument and returns a
275 .Vt "struct ng_l2tp_session_stats"
276 containing statistics for the corresponding data session.
277 The corresponding session hook must be connected.
278 .It Dv NGM_L2TP_CLR_SESSION_STATS Pq Ic clrsessstats
279 This command takes a two byte session ID as an argument and
280 clears the statistics for that data session.
281 The corresponding session hook must be connected.
282 .It Dv NGM_L2TP_GETCLR_SESSION_STATS Pq Ic getclrsessstats
284 .Dv NGM_L2TP_GET_SESSION_STATS ,
285 but also atomically clears the statistics as well.
286 .It Dv NGM_L2TP_SET_SEQ Pq Ic setsequence
287 This command sets the sequence numbers of a not yet enabled node.
289 .Vt "struct ng_l2tp_seq_config"
299 This option is particularly useful if one receives and processes
300 the first packet entirely in userspace and wants to hand over further
301 processing to the node.
304 This node shuts down upon receipt of a
306 control message, or when all hooks have been disconnected.
320 .%T "Layer Two Tunneling Protocol L2TP"
326 node type was developed at Packet Design, LLC,
327 .Pa http://www.packetdesign.com/ .
329 .An Archie Cobbs Aq Mt archie@packetdesign.com