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36 .\" Author: Archie Cobbs <archie@FreeBSD.org>
43 .Nd L2TP protocol netgraph node type
46 .In netgraph/ng_l2tp.h
50 node type implements the encapsulation layer of the L2TP protocol
51 as described in RFC 2661.
52 This includes adding the L2TP packet header for outgoing packets
53 and verifying and removing it for incoming packets.
54 The node maintains the L2TP sequence number state and handles
55 control session packet acknowledgment and retransmission.
59 node type supports the following hooks:
60 .Bl -tag -width ".Va session_hhhh"
66 Session 0xhhhh data packets.
69 L2TP control and data packets are transmitted to, and received from,
73 Typically this hook would be connected to the
77 node for L2TP over UDP.
81 hook connects to the local L2TP management entity.
82 L2TP control messages (without any L2TP headers) are transmitted
83 and received on this hook.
84 Messages written to this hook are guaranteed to be delivered to the
85 peer reliably, in order, and without duplicates.
87 Packets written to the
89 hook must contain a two byte session ID prepended to the frame
91 This session ID is copied to the outgoing L2TP header.
92 Similarly, packets read from the
94 hook will have the received session ID prepended.
96 Once an L2TP session has been created, the corresponding session
97 hook may be used to transmit and receive the session's data frames:
98 for the session with session ID
103 This node type supports the generic control messages, plus the following:
105 .It Dv NGM_L2TP_SET_CONFIG Pq Ic setconfig
106 This command updates the configuration of the node.
108 .Vt "struct ng_l2tp_config"
111 /* Configuration for a node */
112 struct ng_l2tp_config {
113 u_char enabled; /* enables traffic flow */
114 u_char match_id; /* tunnel id must match 'tunnel_id' */
115 uint16_t tunnel_id; /* local tunnel id */
116 uint16_t peer_id; /* peer's tunnel id */
117 uint16_t peer_win; /* peer's max recv window size */
118 uint16_t rexmit_max; /* max retransmits before failure */
119 uint16_t rexmit_max_to; /* max delay between retransmits */
125 field enables packet processing.
126 Each time this field is changed back to zero the sequence
127 number state is reset.
128 In this way, reuse of a node is possible.
132 field configures the local tunnel ID for the control connection.
135 field determines how incoming L2TP packets with a tunnel ID
141 is non-zero, they will be dropped; otherwise, they will be dropped
142 only if the tunnel ID is non-zero.
145 is set to the local tunnel ID as soon as it is known and
147 is set to non-zero after receipt of the SCCRP or SCCCN control message.
149 The peer's tunnel ID should be set in
151 as soon as it is learned, typically after receipt of a SCCRQ or SCCRP
153 This value is copied into the L2TP header for outgoing packets.
157 field should be set from the
158 .Dq "Receive Window Size"
159 AVP received from the peer.
160 The default value for this field is one; zero is an invalid value.
163 is non-zero, this value may not be decreased.
169 fields configure packet retransmission.
171 is the maximum retransmission delay between packets, in seconds.
172 The retransmit delay will start at a small value and increase
173 exponentially up to this limit.
176 sets the maximum number of times a packet will be retransmitted
177 without being acknowledged before a failure condition is declared.
178 Once a failure condition is declared, each additional retransmission
182 .Dv NGM_L2TP_ACK_FAILURE Pq Ic ackfailure
183 control message back to the node that sent the last
184 .Dv NGM_L2TP_SET_CONFIG .
185 Appropriate action should then be taken to shutdown the control connection.
186 .It Dv NGM_L2TP_GET_CONFIG Pq Ic getconfig
187 Returns the current configuration as a
188 .Vt "struct ng_l2tp_config" .
189 .It Dv NGM_L2TP_SET_SESS_CONFIG Pq Ic setsessconfig
190 This control message configures a single data session.
191 The corresponding hook must already be connected before sending this command.
193 .Vt "struct ng_l2tp_sess_config" :
195 /* Configuration for a session hook */
196 struct ng_l2tp_sess_config {
197 uint16_t session_id; /* local session id */
198 uint16_t peer_id; /* peer's session id */
199 u_char control_dseq; /* whether we control data sequencing */
200 u_char enable_dseq; /* whether to enable data sequencing */
201 u_char include_length; /* whether to include length field */
209 fields configure the local and remote session IDs, respectively.
215 fields determine whether sequence numbers are used with L2TP data packets.
218 is zero, then no sequence numbers are sent and incoming sequence numbers
220 Otherwise, sequence numbers are included on outgoing packets and checked
225 is non-zero, then the setting of
227 will never change except by another
228 .Dv NGM_L2TP_SET_SESS_CONFIG
232 is zero, then the peer controls whether sequence numbers are used:
233 if an incoming L2TP data packet contains sequence numbers,
235 is set to one, and conversely if an incoming L2TP data packet does not
236 contain sequence numbers,
241 is always accessible via the
242 .Dv NGM_L2TP_GET_SESS_CONFIG
243 control message (see below).
244 Typically an LNS would set
246 to one while a LAC would set
248 to zero (if the Sequencing Required AVP were not sent), thus giving
249 control of data packet sequencing to the LNS.
253 field determines whether the L2TP header length field is included
254 in outgoing L2TP data packets.
255 For incoming packets, the L2TP length field is always checked when present.
256 .It Dv NGM_L2TP_GET_SESS_CONFIG Pq Ic getsessconfig
257 This command takes a two byte session ID as an argument and returns
258 the current configuration for the corresponding data session as a
259 .Vt "struct ng_l2tp_sess_config" .
260 The corresponding session hook must be connected.
261 .It Dv NGM_L2TP_GET_STATS Pq Ic getstats
262 This command returns a
263 .Vt "struct ng_l2tp_stats"
264 containing statistics of the L2TP tunnel.
265 .It Dv NGM_L2TP_CLR_STATS Pq Ic clrstats
266 This command clears the statistics for the L2TP tunnel.
267 .It Dv NGM_L2TP_GETCLR_STATS Pq Ic getclrstats
269 .Dv NGM_L2TP_GET_STATS ,
270 but also atomically clears the statistics as well.
271 .It Dv NGM_L2TP_GET_SESSION_STATS Pq Ic getsessstats
272 This command takes a two byte session ID as an argument and returns a
273 .Vt "struct ng_l2tp_session_stats"
274 containing statistics for the corresponding data session.
275 The corresponding session hook must be connected.
276 .It Dv NGM_L2TP_CLR_SESSION_STATS Pq Ic clrsessstats
277 This command takes a two byte session ID as an argument and
278 clears the statistics for that data session.
279 The corresponding session hook must be connected.
280 .It Dv NGM_L2TP_GETCLR_SESSION_STATS Pq Ic getclrsessstats
282 .Dv NGM_L2TP_GET_SESSION_STATS ,
283 but also atomically clears the statistics as well.
284 .It Dv NGM_L2TP_SET_SEQ Pq Ic setsequence
285 This command sets the sequence numbers of a not yet enabled node.
287 .Vt "struct ng_l2tp_seq_config"
297 This option is particularly useful if one receives and processes
298 the first packet entirely in userspace and wants to hand over further
299 processing to the node.
302 This node shuts down upon receipt of a
304 control message, or when all hooks have been disconnected.
318 .%T "Layer Two Tunneling Protocol L2TP"
324 node type was developed at Packet Design, LLC,
325 .Pa http://www.packetdesign.com/ .
327 .An Archie Cobbs Aq Mt archie@packetdesign.com