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25 <H1>L2TPNS Manual
</H1>
27 <LI><A HREF=
"#Overview">Overview
</A></LI>
28 <LI><A HREF=
"#Installation">Installation
</A>
30 <LI><A HREF=
"#Requirements">Requirements
</A></LI>
31 <LI><A HREF=
"#Compile">Compile
</A></LI>
32 <LI><A HREF=
"#Install">Install
</A></LI>
33 <LI><A HREF=
"#Running">Running
</A></LI>
36 <LI><A HREF=
"#Configuration">Configuration
</A>
38 <LI><A HREF=
"#startup-config">startup-config
</A></LI>
39 <LI><A HREF=
"#users">users
</A></LI>
40 <LI><A HREF=
"#ip-pool">ip_pool
</A></LI>
41 <LI><A HREF=
"#build-garden">build-garden
</A></LI>
44 <LI><A HREF=
"#ControllingtheProcess">Controlling the Process
</A>
46 <LI><A HREF=
"#Command-LineInterface">Command-Line Interface
</A></LI>
47 <LI><A HREF=
"#nsctl">nsctl
</A></LI>
48 <LI><A HREF=
"#Signals">Signals
</A></LI>
51 <LI><A HREF=
"#Throttling">Throttling
</A></LI>
52 <LI><A HREF=
"#Interception">Interception
</A></LI>
53 <LI><A HREF=
"#Authentication">Authentication
</A></LI>
54 <LI><A HREF=
"#Plugins">Plugins
</A></LI>
55 <LI><A HREF=
"#WalledGarden">Walled Garden
</A></LI>
56 <LI><A HREF=
"#Filtering">Filtering
</A></LI>
57 <LI><A HREF=
"#Clustering">Clustering
</A></LI>
58 <LI><A HREF=
"#Routing">Routing
</A></LI>
59 <LI><A HREF=
"#Performance">Performance
</A></LI>
62 <H2 ID=
"Overview">Overview
</H2>
63 l2tpns is half of a complete L2TP implementation. It supports only the
64 LNS side of the connection.
<P>
66 L2TP (Layer
2 Tunneling Protocol) is designed to allow any layer
2
67 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns
68 implements PPP over L2TP only.
<P>
70 There are a couple of other L2TP implementations, of which
<A
71 HREF=
"http://sourceforge.net/projects/l2tpd">l2tpd
</A> is probably the
72 most popular. l2tpd also will handle being either end of a tunnel, and
73 is a lot more configurable than l2tpns. However, due to the way it works,
74 it is nowhere near as scalable.
<P>
76 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
77 and send packets. Using some packet manipulation it doesn't require a
78 single interface per connection, as l2tpd does.
<P>
80 This allows it to scale extremely well to very high loads and very high
81 numbers of connections.
<P>
83 It also has a plugin architecture which allows custom code to be run
84 during processing. An example of this is in the walled garden module
88 <EM>Documentation is not my best skill. If you find any problems
89 with this document, or if you wish to contribute, please email
<A
90 HREF=
"mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list
</A>.
</EM><P>
92 <H2 ID=
"Installation">Installation
</H2>
93 <H3 ID=
"Requirements">Requirements
</H3>
96 <LI>Linux kernel version
2.4 or above, with the Tun/Tap interface either
97 compiled in, or as a module.
</LI>
99 <LI>libcli
1.8.0 or greater.
<BR>You can get this from
<A
100 HREF=
"http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli
</A></LI>
103 <H3 ID=
"Compile">Compile
</H3>
105 You can generally get away with just running
<B>make
</B> from the source
106 directory. This will compile the daemon, associated tools and any modules
107 shipped with the distribution.
<P>
109 <H3 ID=
"Install">Install
</H3>
111 After you have successfully compiled everything, run
<B>make
112 install
</B> to install it. By default, the binaries are installed into
113 <EM>/usr/sbin
</EM>, the configuration into
<EM>/etc/l2tpns
</EM>, and the
114 modules into
<EM>/usr/lib/l2tpns
</EM>.
<P>
116 You will definately need to edit the configuration files before you
117 start. See the
<A HREF=
"#Configuration">Configuration
</A> section for
120 <H3 ID=
"Running">Running
</H3>
122 You only need to run
<B>/usr/sbin/l2tpns
</B> as root to start it. It does
123 not detach to a daemon process, so you should perhaps run it from init.
<P>
125 By default there is no log destination set, so all log messages will go to
128 <H2 ID=
"Configuration">Configuration
</H2>
130 All configuration of the software is done from the files installed into
133 <H3 ID=
"startup-config">startup-config
</H3>
135 This is the main configuration file for l2tpns. The format of the file is a
136 list of commands that can be run through the command-line interface. This
137 file can also be written directly by the l2tpns process if a user runs the
138 <EM>write memory
</EM> command, so any comments will be lost. However if your
139 policy is not to write the config by the program, then feel free to comment
140 the file with a # or ! at the beginning of the line.
<P>
142 A list of the possible configuration directives follows. Each of these
143 should be set by a line like:
<P>
145 set configstring
"value"
146 set ipaddress
192.168.1.1
152 <LI><B>debug
</B> (int)
<BR>
153 Sets the level of messages that will be written to the log file. The value
154 should be between
0 and
5, with
0 being no debugging, and
5 being the
155 highest. A rough description of the levels is:
157 <LI VALUE=
0>Critical Errors - Things are probably broken
</LI>
158 <LI>Errors - Things might have gone wrong, but probably will recover
</LI>
159 <LI>Warnings - Just in case you care what is not quite perfect
</LI>
160 <LI>Information - Parameters of control packets
</LI>
161 <LI>Calls - For tracing the execution of the code
</LI>
162 <LI>Packets - Everything, including a hex dump of all packets processed... probably twice
</LI>
164 Note that the higher you set the debugging level, the slower the program
165 will run. Also, at level
5 a LOT of information will be logged. This should
166 only ever be used for working out why it doesn't work at all.
169 <LI><B>log_file
</B> (string)
<BR>
170 This will be where all logging and debugging information is written
171 to. This may be either a filename, such as
<EM>/var/log/l2tpns
</EM>, or
172 the special magic string
<EM>syslog:facility
</EM>, where
<EM>facility
</EM>
173 is any one of the syslog logging facilities, such as local5.
176 <LI><B>pid_file
</B> (string)
<BR>
177 If set, the process id will be written to the specified file. The
178 value must be an absolute path.
181 <LI><B>l2tp_secret
</B> (string)
<BR>
182 The secret used by l2tpns for authenticating tunnel request. Must be
183 the same as the LAC, or authentication will fail. Only actually be
184 used if the LAC requests authentication.
187 <LI><B>primary_dns
</B> (ip address)
188 <LI><B>secondary_dns
</B> (ip address)
<BR>
189 Whenever a PPP connection is established, DNS servers will be sent to the
190 user, both a primary and a secondary. If either is set to
0.0.0.0, then that
191 one will not be sent.
194 <LI><B>primary_radius
</B> (ip address)
195 <LI><B>secondary_radius
</B> (ip address)
<BR>
196 Sets the RADIUS servers used for both authentication and accounting.
197 If the primary server does not respond, then the secondary RADIUS
198 server will be tried.
<br>
199 <strong>Note:
</strong> in addition to the source IP address and
200 identifier, the RADIUS server
<strong>must
</strong> include the source
201 port when detecting duplicates to supress (in order to cope with a
202 large number of sessions comming on-line simultaneously l2tpns uses a
203 set of udp sockets, each with a seperate identifier).
206 <LI><B>primary_radius_port
</B> (short)
207 <LI><B>secondary_radius_port
</B> (short)
<BR>
208 Sets the authentication ports for the primary and secondary RADIUS
209 servers. The accounting port is one more than the authentication
210 port. If no RADIUS ports are given, the authentication port defaults
211 to
1645, and the accounting port to
1646.
214 <LI><B>radius_accounting
</B> (boolean)
<BR>
215 If set to true, then RADIUS accounting packets will be sent. This
216 means that a Start record will be sent when the session is
217 successfully authenticated, and a Stop record will be sent when the
221 <LI><B>radius_secret
</B> (string)
<BR>
222 This secret will be used in all RADIUS queries. If this is not set then
223 RADIUS queries will fail.
226 <LI><B>radius_authtypes
</B> (string)
</BR>
227 A comma separated list of supported RADIUS authentication methods
228 (
<B>pap
</B> or
<B>chap
</B>), in order of preference (default
<B>pap
</B>).
231 <LI><B>allow_duplicate_users
</B> (boolean)
</BR>
232 Allow multiple logins with the same username. If false (the default),
233 any prior session with the same username will be dropped when a new
234 session is established.
237 <LI><B>bind_address
</B> (ip address)
<BR>
238 When the tun interface is created, it is assigned the address
239 specified here. If no address is given,
1.1.1.1 is used. Packets
240 containing user traffic should be routed via this address if given,
241 otherwise the primary address of the machine.
244 <LI><B>peer_address
</B> (ip address)
<BR>
245 Address to send to clients as the default gateway.
248 <LI><B>send_garp
</B> (boolean)
<BR>
249 Determines whether or not to send a gratuitous ARP for the
250 bind_address when the server is ready to handle traffic (default:
252 This value is ignored if BGP is configured.
255 <LI><B>throttle_speed
</B> (int)
<BR>
256 Sets the default speed (in kbits/s) which sessions will be limited to.
257 If this is set to
0, then throttling will not be used at all. Note:
258 You can set this by the CLI, but changes will not affect currently
262 <LI><B>throttle_buckets
</B> (int)
<BR>
263 Number of token buckets to allocate for throttling. Each throttled
264 session requires two buckets (in and out).
267 <LI><B>accounting_dir
</B> (string)
<BR>
268 If set to a directory, then every
5 minutes the current usage for
269 every connected use will be dumped to a file in this directory. Each
270 file dumped begins with a header, where each line is prefixed by #.
271 Following the header is a single line for every connected user, fields
272 separated by a space.
<BR> The fields are username, ip, qos,
273 uptxoctets, downrxoctets. The qos field is
1 if a standard user, and
274 2 if the user is throttled.
277 <LI><B>setuid
</B> (int)
<BR>
278 After starting up and binding the interface, change UID to this. This
279 doesn't work properly.
282 <LI><B>dump_speed
</B> (boolean)
<BR>
283 If set to true, then the current bandwidth utilization will be logged every
284 second. Even if this is disabled, you can see this information by running
285 the
<EM>uptime
</EM> command on the CLI.
288 <LI><B>multi_read_count
</B> (int)
<BR>
289 Number of packets to read off each of the UDP and TUN fds when
290 returned as readable by select (default:
10). Avoids incurring the
291 unnecessary system call overhead of select on busy servers.
294 <LI><B>scheduler_fifo
</B> (boolean)
<BR>
295 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
296 causes the kernel to immediately preempt any currently running SCHED_OTHER
297 (normal) process in favour of l2tpns when it becomes runnable.
298 Ignored on uniprocessor systems.
301 <LI><B>lock_pages
</B> (boolean)
<BR>
302 Keep all pages mapped by the l2tpns process in memory.
305 <LI><B>icmp_rate
</B> (int)
<BR>
306 Maximum number of host unreachable ICMP packets to send per second.
309 <LI><B>packet_limit
</B> (int
><BR>
310 Maximum number of packets of downstream traffic to be handled each
311 tenth of a second per session. If zero, no limit is applied (default:
312 0). Intended as a DoS prevention mechanism and not a general
313 throttling control (packets are dropped, not queued).
316 <LI><B>cluster_address
</B> (ip address)
<BR>
317 Multicast cluster address (default:
239.192.13.13). See the section
318 on
<A HREF=
"#Clustering">Clustering
</A> for more information.
321 <LI><B>cluster_interface
</B> (string)
<BR>
322 Interface for cluster packets (default: eth0).
325 <LI><B>cluster_hb_interval
</B> (int)
<BR>
326 Interval in tenths of a second between cluster heartbeat/pings.
329 <LI><B>cluster_hb_timeout
</B> (int)
<BR>
330 Cluster heartbeat timeout in tenths of a second. A new master will be
331 elected when this interval has been passed without seeing a heartbeat
335 <LI><B>cluster_master_min_adv
</B> (int)
<BR>
336 Determines the minumum number of up to date slaves required before the
337 master will drop routes (default:
1).
341 <P>BGP routing configuration is entered by the command:
342 The routing configuration section is entered by the command
343 <DL><DD><B>router bgp
</B> <I>as
</I></DL>
344 where
<I>as
</I> specifies the local AS number.
346 <P>Subsequent lines prefixed with
347 <DL><DD><B>neighbour
</B> <I>peer
</I></DL>
348 define the attributes of BGP neighhbours. Valid commands are:
350 <DD><B>neighbour
</B> <I>peer
</I> <B>remote-as
</B> <I>as
</I>
351 <DD><B>neighbout
</B> <I>peer
</I> <B>timers
</B> <I>keepalive hold
</I>
354 Where
<I>peer
</I> specifies the BGP neighbour as either a hostname or
355 IP address,
<I>as
</I> is the remote AS number and
<I>keepalive
</I>,
356 <I>hold
</I> are the timer values in seconds.
358 <P>Named access-lists are configured using one of the commands:
360 <DD><B>ip access-list standard
</B> <I>name
</I>
361 <DD><B>ip access-list extended
</B> <I>name
</I>
364 <P>Subsequent lines prefixed with
<B>permit
</B> or
<B>deny
</B>
365 define the body of the access-list. Standard access-list syntax:
367 <DD>{
<B>permit
</B>|
<B>deny
</B>}
368 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
369 [{
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>}]
372 Extended access-lists:
374 <DIV STYLE=
"margin-left: 4em; text-indent: -2em">
375 <P>{
<B>permit
</B>|
<B>deny
</B>}
<B>ip
</B>
376 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
377 {
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>} [
<B>fragments
</B>]
378 <P>{
<B>permit
</B>|
<B>deny
</B>}
<B>udp
</B>
379 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
380 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
381 {
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>}
382 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
384 <P>{
<B>permit
</B>|
<B>deny
</B>}
<B>tcp
</B>
385 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
386 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
387 {
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>}
388 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
389 [{
<B>established
</B>|{
<B>match-any
</B>|
<B>match-all
</B>}
390 {
<B>+
</B>|
<B>-
</B>}{
<B>fin
</B>|
<B>syn
</B>|
<B>rst
</B>|
<B>psh
</B>|
<B>ack
</B>|
<B>urg
</B>}
391 ...|
<B>fragments
</B>]
394 <H3 ID=
"users">users
</H3>
396 Usernames and passwords for the command-line interface are stored in
397 this file. The format is
<I>username
</I><B>:
</B><I>password
</I> where
398 <I>password
</I> may either by plain text, an MD5 digest (prefixed by
399 <B>$
1</B><I>salt
</I><B>$
</B>) or a DES password, distinguished from
400 plain text by the prefix
<B>{crypt}
</B>.
<P>
402 The username
<B>enable
</B> has a special meaning and is used to set
403 the enable password.
<P>
405 <B>Note:
</B> If this file doesn't exist, then anyone who can get to
406 port
23 will be allowed access without a username / password.
<P>
408 <H3 ID=
"ip-pool">ip_pool
</H3>
410 This file is used to configure the IP address pool which user
411 addresses are assigned from. This file should contain either an IP
412 address or a CIDR network per line. e.g.:
<P>
423 Keep in mind that l2tpns can only handle
65535 connections per
424 process, so don't put more than
65535 IP addresses in the
425 configuration file. They will be wasted.
427 <H3 ID=
"build-garden">build-garden
</H3>
429 The garden plugin on startup creates a NAT table called
"garden" then
430 sources the
<B>build-garden
</B> script to populate that table. All
431 packets from gardened users will be sent through this table. Example:
434 iptables -t nat -A garden -p tcp -m tcp --dport
25 -j DNAT --to
192.168.1.1
435 iptables -t nat -A garden -p udp -m udp --dport
53 -j DNAT --to
192.168.1.1
436 iptables -t nat -A garden -p tcp -m tcp --dport
53 -j DNAT --to
192.168.1.1
437 iptables -t nat -A garden -p tcp -m tcp --dport
80 -j DNAT --to
192.168.1.1
438 iptables -t nat -A garden -p tcp -m tcp --dport
110 -j DNAT --to
192.168.1.1
439 iptables -t nat -A garden -p tcp -m tcp --dport
443 -j DNAT --to
192.168.1.1
440 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to
192.168.1.1
441 iptables -t nat -A garden -p icmp -j ACCEPT
442 iptables -t nat -A garden -j DROP
445 <H2 ID=
"ControllingtheProcess">Controlling the Process
</H2>
447 A running l2tpns process can be controlled in a number of ways. The primary
448 method of control is by the Command-Line Interface (CLI).
<P>
450 You can also remotely send commands to modules via the nsctl client
453 Also, there are a number of signals that l2tpns understands and takes action
454 when it receives them.
456 <H3 ID=
"Command-LineInterface">Command-Line Interface
</H3>
458 You can access the command line interface by telnet'ing to port
23.
459 There is no IP address restriction, so it's a good idea to firewall
460 this port off from anyone who doesn't need access to it. See
461 <A HREF=
"#users">users
</A> for information on restricting access based
462 on a username and password.
<P>
464 The CLI gives you real-time control over almost everything in
465 the process. The interface is designed to look like a Cisco
466 device, and supports things like command history, line editing and
467 context sensitive help. This is provided by linking with the
468 <A HREF=
"http://sourceforge.net/projects/libcli">libcli
</A>
469 library. Some general documentation of the interface is
470 <A HREF=
"http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
473 After you have connected to the telnet port (and perhaps logged in), you
474 will be presented with a
<I>hostname
</I><B>></B> prompt.
<P>
476 Enter
<EM>help
</EM> to get a list of possible commands. A brief
477 overview of the more important commands follows:
480 <LI><B>show session
</B><BR>
481 Without specifying a session ID, this will list all tunnels currently
482 connected. If you specify a session ID, you will be given all
483 information on a single tunnel. Note that the full session list can
484 be around
185 columns wide, so you should probably use a wide terminal
485 to see the list properly.
<P>
486 The columns listed in the overview are:
488 <TR><TD><B>SID
</B></TD><TD>Session ID
</TD></TR>
489 <TR><TD><B>TID
</B></TD><TD>Tunnel ID - Use with
<EM>show tunnel tid
</EM></TD></TR>
490 <TR><TD><B>Username
</B></TD><TD>The username given in the PPP
491 authentication. If this is *, then LCP authentication has not
493 <TR><TD><B>IP
</B></TD><TD>The IP address given to the session. If
494 this is
0.0.0.0, LCP negotiation has not completed.
</TD></TR>
495 <TR><TD><B>I
</B></TD><TD>Intercept - Y or N depending on whether the
496 session is being snooped. See
<EM>snoop
</EM>.
</TD></TR>
497 <TR><TD><B>T
</B></TD><TD>Throttled - Y or N if the session is
498 currently throttled. See
<EM>throttle
</EM>.
</TD></TR>
499 <TR><TD><B>G
</B></TD><TD>Walled Garden - Y or N if the user is
500 trapped in the walled garden. This field is present even if the
501 garden module is not loaded.
</TD></TR>
502 <TR><TD><B>opened
</B></TD><TD>The number of seconds since the
503 session started
</TD></TR>
504 <TR><TD><B>downloaded
</B></TD><TD>Number of bytes downloaded by the user
</TD></TR>
505 <TR><TD><B>uploaded
</B></TD><TD>Number of bytes uploaded by the user
</TD></TR>
506 <TR><TD><B>idle
</B></TD><TD>The number of seconds since traffic was
507 detected on the session
</TD></TR>
508 <TR><TD><B>LAC
</B></TD><TD>The IP address of the LAC the session is
509 connected to.
</TD></TR>
510 <TR><TD><B>CLI
</B></TD><TD>The Calling-Line-Identification field
511 provided during the session setup. This field is generated by the
517 <LI><B>show users
</B><BR>
518 With no arguments, display a list of currently connected users. If an
519 argument is given, the session details for the given username are
523 <LI><B>show tunnel
</B><BR>
524 This will show all the open tunnels in a summary, or detail on a single
525 tunnel if you give a tunnel id.
<P>
526 The columns listed in the overview are:
528 <TR><TD><B>TID
</B></TD><TD>Tunnel ID
</TD></TR>
529 <TR><TD><B>Hostname
</B></TD><TD>The hostname for the tunnel as
530 provided by the LAC. This has no relation to DNS, it is just
531 a text field.
</TD></TR>
532 <TR><TD><B>IP
</B></TD><TD>The IP address of the LAC
</TD></TR>
533 <TR><TD><B>State
</B></TD><TD>Tunnel state - Free, Open, Dieing,
535 <TR><TD><B>Sessions
</B></TD><TD>The number of open sessions on the
541 <LI><B>show pool
</B><BR>
542 Displays the current IP address pool allocation. This will only display
543 addresses that are in use, or are reserved for re-allocation to a
544 disconnected user.
<P>
545 If an address is not currently in use, but has been used, then in the User
546 column the username will be shown in square brackets, followed by the time
547 since the address was used:
549 IP Address Used Session User
550 192.168.100.6 N [joe.user]
1548s
555 <LI><B>show radius
</B><BR>
556 Show a summary of the in-use RADIUS sessions. This list should not be very
557 long, as RADIUS sessions should be cleaned up as soon as they are used. The
560 <TR><TD><B>Radius
</B></TD><TD>The ID of the RADIUS request. This is
561 sent in the packet to the RADIUS server for identification.
</TD></TR>
562 <TR><TD><B>State
</B></TD><TD>The state of the request - WAIT, CHAP,
563 AUTH, IPCP, START, STOP, NULL.
</TD></TR>
564 <TR><TD><B>Session
</B></TD><TD>The session ID that this RADIUS
565 request is associated with
</TD></TR>
566 <TR><TD><B>Retry
</B></TD><TD>If a response does not appear to the
567 request, it will retry at this time. This is a unix timestamp.
</TD></TR>
568 <TR><TD><B>Try
</B></TD><TD>Retry count. The RADIUS request is
569 discarded after
3 retries.
</TD></TR>
574 <LI><B>show running-config
</B><BR>
575 This will list the current running configuration. This is in a format that
576 can either be pasted into the configuration file, or run directly at the
581 <LI><B>show counters
</B><BR>
582 Internally, counters are kept of key values, such as bytes and packets
583 transferred, as well as function call counters. This function displays all
584 these counters, and is probably only useful for debugging.
<P>
585 You can reset these counters by running
<EM>clear counters
</EM>.
589 <LI><B>show cluster
</B><BR>
590 Show cluster status. Shows the cluster state for this server
591 (Master/Slave), information about known peers and (for slaves) the
592 master IP address, last packet seen and up-to-date status.
<P>
593 See
<A HREF=
"#Clustering">Clustering
</A> for more information.
597 <LI><B>write memory
</B><BR>
598 This will write the current running configuration to the config file
599 <B>startup-config
</B>, which will be run on a restart.
604 You must specify a username, IP address and port. All packets for the
605 current session for that username will be forwarded to the given
606 host/port. Specify
<EM>no snoop username
</EM> to disable interception
609 If you want interception to be permanent, you will have to modify the RADIUS
610 response for the user. See
<A HREF=
"#Interception">Interception
</A>.
614 <LI><B>throttle
</B><BR>
615 You must specify a username, which will be throttled for the current
616 session. Specify
<EM>no throttle username
</EM> to disable throttling
617 for the current session.
<P>
619 If you want throttling to be permanent, you will have to modify the
620 RADIUS response for the user. See
<A HREF=
"#Throttling">Throttling
</A>.
624 <LI><B>drop session
</B><BR>
625 This will cleanly disconnect a session. You must specify a session id, which
626 you can get from
<EM>show session
</EM>. This will send a disconnect message
631 <LI><B>drop tunnel
</B><BR>
632 This will cleanly disconnect a tunnel, as well as all sessions on that
633 tunnel. It will send a disconnect message for each session individually, and
634 after
10 seconds it will send a tunnel disconnect message.
638 <LI><B>uptime
</B><BR>
639 This will show how long the l2tpns process has been running, and the current
640 bandwidth utilization:
642 17:
10:
35 up
8 days,
2212 users, load average:
0.21,
0.17,
0.16
643 Bandwidth: UDP-ETH:
6/
6 ETH-UDP:
13/
13 TOTAL:
37.6 IN:
3033 OUT:
2569
645 The bandwidth line contains
4 sets of values.
<BR>
646 UDP-ETH is the current bandwidth going from the LAC to the ethernet
647 (user uploads), in mbits/sec.
<BR>
648 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
650 TOTAL is the total aggregate bandwidth in mbits/s.
<BR>
651 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
653 These counters are updated every second.
657 <LI><B>configure terminal
</B><BR>
658 Enter configuration mode. Use
<EM>exit
</EM> or ^Z to exit this mode.
659 The following commands are valid in this mode:
<P>
662 <LI><B>load plugin
</B><BR>
663 Load a plugin. You must specify the plugin name, and it will search in
664 /usr/lib/l2tpns for
<EM>plugin
</EM>.so. You can unload a loaded plugin with
665 <EM>remove plugin
</EM>.
670 Set a configuration variable. You must specify the variable name, and
671 the value. If the value contains any spaces, you should quote the
672 value with double (
") or single (') quotes.<P>
674 You can set any <A HREF="#startup-config
">startup-config</A> value in
675 this way, although some may require a restart to take effect.<P>
679 <H3 ID="nsctl
">nsctl</H3>
681 nsctl allows messages to be passed to plugins.<P>
683 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
684 <STRONG>nsctl</STRONG>(8) for more details.<P>
686 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
687 <EM>help</EM>. Any other commands are passed to plugins for processing.
689 <H3 ID="Signals
">Signals</H3>
691 While the process is running, you can send it a few different signals, using
697 The signals understood are:
699 <LI>SIGHUP - Reload the config from disk and re-open log file</LI>
700 <LI>SIGTERM / SIGINT - Shut down.</LI>
701 <LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
702 every active session and tunnel before shutting down.</LI>
705 <H2 ID="Throttling
">Throttling</H2>
707 l2tpns contains support for slowing down user sessions to whatever speed you
708 desire. You must first enable the global setting <EM>throttle_speed</EM>
709 before this will be activated.<P>
711 If you wish a session to be throttled permanently, you should set the
712 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes
"</B>, which
713 will be handled by the <EM>autothrottle</EM> module.<P>
715 Otherwise, you can enable and disable throttling an active session using
716 the <EM>throttle</EM> CLI command.<P>
718 <H2 ID="Interception
">Interception</H2>
720 You may have to deal with legal requirements to be able to intercept a
721 user's traffic at any time. l2tpns allows you to begin and end interception
722 on the fly, as well as at authentication time.<P>
724 When a user is being intercepted, a copy of every packet they send and
725 receive will be sent wrapped in a UDP packet to the IP address and port set
726 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
729 The UDP packet contains just the raw IP frame, with no extra headers.<P>
731 To enable interception on a connected user, use the <EM>snoop username</EM>
732 and <EM>no snoop username</EM> CLI commands. These will enable interception
735 If you wish the user to be intercepted whenever they reconnect, you will
736 need to modify the RADIUS response to include the Vendor-Specific value
737 <B>Cisco-Avpair="intercept=yes
"</B>. For this feature to be enabled,
738 you need to have the <EM>autosnoop</EM> module loaded.<P>
740 <H2 ID="Authentication
">Authentication</H2>
742 Whenever a session connects, it is not fully set up until authentication is
743 completed. The remote end must send a PPP CHAP or PPP PAP authentication
744 request to l2tpns.<P>
746 This request is sent to the RADIUS server, which will hopefully respond with
747 Auth-Accept or Auth-Reject.<P>
749 If Auth-Accept is received, the session is set up and an IP address is
750 assigned. The RADIUS server can include a Framed-IP-Address field in the
751 reply, and that address will be assigned to the client. It can also include
752 specific DNS servers, and a Framed-Route if that is required.<P>
754 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
755 at which point they should disconnect. The exception to this is when the
756 walled garden module is loaded, in which case the user still receives the
757 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
758 should not receive any service.<P>
760 The RADIUS reply can also contain a Vendor-Specific attribute called
761 Cisco-Avpair. This field is a freeform text field that most Cisco
762 devices understand to contain configuration instructions for the session. In
763 the case of l2tpns it is expected to be of the form
765 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
768 Each key-value pair is separated and passed to any modules loaded. The
769 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
770 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
771 a user who is to be throttled and intercepted, the Cisco-Avpair value should
774 intercept=yes,throttle=yes
777 <H2 ID="Plugins
">Plugins</H2>
779 So as to make l2tpns as flexible as possible (I know the core code is pretty
780 difficult to understand), it includes a plugin API, which you can use to
781 hook into certain events.<P>
783 There are a few example modules included - autosnoop, autothrottle and
786 When an event happens that has a hook, l2tpns looks for a predefined
787 function name in every loaded module, and runs them in the order the modules
790 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
791 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
792 modules should be run for this event.<P>
793 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
794 no further processing should be done for this event. <EM>Use this with care.</EM>
796 Every event function called takes a specific structure named
797 param_<EM>event</EM>, which varies in content with each event. The
798 function name for each event will be <B>plugin_<EM>event</EM></B>,
799 so for the event <EM>timer</EM>, the function declaration should look like:
801 int plugin_timer(struct param_timer *data);
804 A list of the available events follows, with a list of all the fields in the
806 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
807 <TABLE CELLSPACING=1 CELLPADDING=3>
808 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
809 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
810 <TD>This is called after a RADIUS response has been
811 received, but before it has been processed by the
812 code. This will allow you to modify the response in
817 <LI>t - Tunnel ID</LI>
818 <LI>s - Session ID</LI>
821 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
822 <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
826 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
827 <TD>This is called after a RADIUS response has been
828 received, and the basic checks have been performed. This
829 is what the garden module uses to force authentication
834 <LI>t - Tunnel ID</LI>
835 <LI>s - Session ID</LI>
837 <LI>auth_allowed - This is already set to true or
838 false depending on whether authentication has been
839 allowed so far. You can set this to 1 or 0 to force
840 allow or disallow authentication</LI>
841 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
845 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
846 <TD>This is called whenever a session receives a
847 packet. <FONT COLOR=RED>Use this sparingly, as this will
848 seriously slow down the system.</FONT>
852 <LI>t - Tunnel ID</LI>
853 <LI>s - Session ID</LI>
854 <LI>buf - The raw packet data</LI>
855 <LI>len - The length of buf</LI>
859 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
860 <TD>This is called whenever a session sends a
861 packet. <FONT COLOR=RED>Use this sparingly, as this will
862 seriously slow down the system.</FONT>
866 <LI>t - Tunnel ID</LI>
867 <LI>s - Session ID</LI>
868 <LI>buf - The raw packet data</LI>
869 <LI>len - The length of buf</LI>
873 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
874 <TD>This is run every second, no matter what is happening.
875 This is called from a signal handler, so make sure anything
880 <LI>time_now - The current unix timestamp</LI>
884 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
885 <TD>This is called after a session is fully set up. The
886 session is now ready to handle traffic.
890 <LI>t - Tunnel ID</LI>
891 <LI>s - Session ID</LI>
895 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
896 <TD>This is called when a session is about to be shut down.
897 This may be called multiple times for the same session.
901 <LI>t - Tunnel ID</LI>
902 <LI>s - Session ID</LI>
906 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
907 <TD>This is called whenever a RADIUS response includes a
908 Cisco-Avpair value. The value is split up into
909 <EM>key=value</EM> pairs, and each is processed through all
914 <LI>t - Tunnel ID</LI>
915 <LI>s - Session ID</LI>
921 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
922 <TD>This is called in whenever a nsctl packet is received.
923 This should handle the packet and form a response if
928 <LI>buf - The raw packet data</LI>
929 <LI>l - The raw packet data length</LI>
930 <LI>source_ip - Where the request came from</LI>
931 <LI>source_port - Where the request came from</LI>
932 <LI>response - Allocate a buffer and put your response in here</LI>
933 <LI>response_length - Length of response</LI>
934 <LI>send_response - true or false whether a response
935 should be sent. If you set this to true, you must
936 allocate a response buffer.</LI>
937 <LI>type - Type of request (see nsctl.c)</LI>
938 <LI>id - ID of request</LI>
939 <LI>data - I'm really not sure</LI>
940 <LI>data_length - Length of data</LI>
947 <H2 ID="WalledGarden
">Walled Garden</H2>
949 Walled Garden is implemented so that you can provide perhaps limited service
950 to sessions that incorrectly authenticate.<P>
952 Whenever a session provides incorrect authentication, and the
953 RADIUS server responds with Auth-Reject, the walled garden module
954 (if loaded) will force authentication to succeed, but set the flag
955 <EM>garden</EM> in the session structure, and adds an iptables rule to
956 the <B>garden_users</B> chain to force all packets for the session's IP
957 address to traverse the <B>garden</B> chain.<P>
959 This doesn't <EM>just work</EM>. To set this all up, you will to
960 setup the <B>garden</B> nat table with the
961 <A HREF="#build-garden
">build-garden</A> script with rules to limit
962 user's traffic. For example, to force all traffic except DNS to be
963 forwarded to 192.168.1.1, add these entries to your
964 <EM>build-garden</EM>:
966 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
967 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
970 l2tpns will add entries to the garden_users chain as appropriate.<P>
972 You can check the amount of traffic being captured using the following
975 iptables -t nat -L garden -nvx
978 <H2 ID="Filtering
">Filtering</H2>
980 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
981 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
982 access-list <I>filter</I> should be applied to traffic from the
983 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
986 <H2 ID="Clustering
">Clustering</H2>
988 An l2tpns cluster consists of of one* or more servers configured with
989 the same configuration, notably the multicast <B>cluster_address</B>.<P>
991 *A stand-alone server is simply a degraded cluster.<P>
993 Initially servers come up as cluster slaves, and periodically (every
994 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
995 containing the start time of the process to the multicast
996 <B>cluster_address</B>.<P>
998 A cluster master sends heartbeat rather than ping packets, which
999 contain those session and tunnel changes since the last heartbeat.<P>
1001 When a slave has not seen a heartbeat within
1002 <B>cluster_hb_timeout</B>/10 seconds it "elects
" a new master by
1003 examining the list of peers it has seen pings from and determines
1004 which of these and itself is the "best
" candidate to be master.
1005 "Best
" in this context means the server with the highest uptime (the
1006 highest IP address is used as a tie-breaker in the case of equal
1009 After discovering a master, and determining that it is up-to-date (has
1010 seen an update for all in-use sessions and tunnels from heartbeat
1011 packets) will raise a route (see <A HREF="#Routing
">Routing</A>) for
1012 the <B>bind_address</B> and for all addresses/networks in
1013 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1014 the session state, as well as packets for throttled or gardened
1015 sessions are forwarded to the master for handling. In addition, byte
1016 counters for session traffic are periodically forwarded.<P>
1018 A master, when determining that it has at least one up-to-date slave
1019 will drop all routes (raising them again if all slaves disappear) and
1020 subsequently handle only packets forwarded to it by the slaves.<P>
1022 <H2 ID="Routing
">Routing</H2>
1023 If you are running a single instance, you may simply statically route
1024 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1027 For a cluster, configure the members as BGP neighbours on your router
1028 and configure multi-path load-balancing. Cisco uses "maximum-paths
1029 ibgp
" for IBGP. If this is not supported by your IOS revision, you
1030 can use "maximum-paths
" (which works for EBGP) and set
1031 <B>as_number</B> to a private value such as 64512.<P>
1033 <H2 ID="Performance
">Performance</H2>
1035 Performance is great.<P>
1037 I'd like to include some pretty graphs here that show a linear performance
1038 increase, with no impact by number of connected sessions.<P>
1040 That's really what it looks like.<P>
1044 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%
20Documentation
">l2tpns-users@lists.sourceforge.net</A>