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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>l2tp_mtu
</B> (int)
<BR>
188 MTU of interface for L2TP traffic (default:
1500). Used to set link
189 MRU and adjust TCP MSS.
192 <LI><B>ppp_restart_time
</B> (int)
<BR>
193 <B>ppp_max_configure
</B> (int)
<BR>
194 <B>ppp_max_failure
</B> (int)
<BR>
195 PPP counter and timer values, as described in
§4.1 of
196 <a href=
"ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661
</a>.
199 <LI><B>primary_dns
</B> (ip address)
200 <LI><B>secondary_dns
</B> (ip address)
<BR>
201 Whenever a PPP connection is established, DNS servers will be sent to the
202 user, both a primary and a secondary. If either is set to
0.0.0.0, then that
203 one will not be sent.
206 <LI><B>primary_radius
</B> (ip address)
207 <LI><B>secondary_radius
</B> (ip address)
<BR>
208 Sets the RADIUS servers used for both authentication and accounting.
209 If the primary server does not respond, then the secondary RADIUS
210 server will be tried.
<br>
211 <strong>Note:
</strong> in addition to the source IP address and
212 identifier, the RADIUS server
<strong>must
</strong> include the source
213 port when detecting duplicates to supress (in order to cope with a
214 large number of sessions comming on-line simultaneously l2tpns uses a
215 set of udp sockets, each with a seperate identifier).
218 <LI><B>primary_radius_port
</B> (short)
219 <LI><B>secondary_radius_port
</B> (short)
<BR>
220 Sets the authentication ports for the primary and secondary RADIUS
221 servers. The accounting port is one more than the authentication
222 port. If no RADIUS ports are given, the authentication port defaults
223 to
1645, and the accounting port to
1646.
226 <LI><B>radius_accounting
</B> (boolean)
<BR>
227 If set to true, then RADIUS accounting packets will be sent. This
228 means that a Start record will be sent when the session is
229 successfully authenticated, and a Stop record will be sent when the
233 <LI><B>radius_secret
</B> (string)
<BR>
234 This secret will be used in all RADIUS queries. If this is not set then
235 RADIUS queries will fail.
238 <LI><B>radius_authtypes
</B> (string)
</BR>
239 A comma separated list of supported RADIUS authentication methods
240 (
<B>pap
</B> or
<B>chap
</B>), in order of preference (default
<B>pap
</B>).
243 <LI><B>radius_dae_port
</B> (short)
<BR>
244 Port for DAE RADIUS (Packet of Death/Disconnect, Change of Authorization)
245 requests (default:
<B>3799</B>).
248 <LI><B>allow_duplicate_users
</B> (boolean)
</BR>
249 Allow multiple logins with the same username. If false (the default),
250 any prior session with the same username will be dropped when a new
251 session is established.
254 <LI><B>bind_address
</B> (ip address)
<BR>
255 It's the listen address of the l2tp udp protocol sent and received
256 to LAC. This address is also assigned to the tun interface if no
257 iftun_address is specified. Packets containing user traffic should be
258 routed via this address if given, otherwise the primary address of the
262 <LI><B>iftun_address
</B> (ip address)
<BR>
263 This parameter is used when you want a tun interface address different
264 from the address of
"bind_address" (For use in cases of specific configuration).
265 If no address is given to iftun_address and bind_address,
1.1.1.1 is used.
268 <LI><B>tundevicename
</B> (string)
<BR>
269 Name of the tun interface (default:
"tun0").
272 <LI><B>peer_address
</B> (ip address)
<BR>
273 Address to send to clients as the default gateway.
276 <LI><B>send_garp
</B> (boolean)
<BR>
277 Determines whether or not to send a gratuitous ARP for the
278 bind_address when the server is ready to handle traffic (default:
280 This value is ignored if BGP is configured.
283 <LI><B>throttle_speed
</B> (int)
<BR>
284 Sets the default speed (in kbits/s) which sessions will be limited to.
285 If this is set to
0, then throttling will not be used at all. Note:
286 You can set this by the CLI, but changes will not affect currently
290 <LI><B>throttle_buckets
</B> (int)
<BR>
291 Number of token buckets to allocate for throttling. Each throttled
292 session requires two buckets (in and out).
295 <LI><B>accounting_dir
</B> (string)
<BR>
296 If set to a directory, then every
5 minutes the current usage for
297 every connected use will be dumped to a file in this directory. Each
298 file dumped begins with a header, where each line is prefixed by #.
299 Following the header is a single line for every connected user, fields
300 separated by a space.
<BR> The fields are username, ip, qos,
301 uptxoctets, downrxoctets. The qos field is
1 if a standard user, and
302 2 if the user is throttled.
305 <LI><B>setuid
</B> (int)
<BR>
306 After starting up and binding the interface, change UID to this. This
307 doesn't work properly.
310 <LI><B>dump_speed
</B> (boolean)
<BR>
311 If set to true, then the current bandwidth utilization will be logged every
312 second. Even if this is disabled, you can see this information by running
313 the
<EM>uptime
</EM> command on the CLI.
316 <LI><B>multi_read_count
</B> (int)
<BR>
317 Number of packets to read off each of the UDP and TUN fds when
318 returned as readable by select (default:
10). Avoids incurring the
319 unnecessary system call overhead of select on busy servers.
322 <LI><B>scheduler_fifo
</B> (boolean)
<BR>
323 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
324 causes the kernel to immediately preempt any currently running SCHED_OTHER
325 (normal) process in favour of l2tpns when it becomes runnable.
326 Ignored on uniprocessor systems.
329 <LI><B>lock_pages
</B> (boolean)
<BR>
330 Keep all pages mapped by the l2tpns process in memory.
333 <LI><B>icmp_rate
</B> (int)
<BR>
334 Maximum number of host unreachable ICMP packets to send per second.
337 <LI><B>packet_limit
</B> (int
><BR>
338 Maximum number of packets of downstream traffic to be handled each
339 tenth of a second per session. If zero, no limit is applied (default:
340 0). Intended as a DoS prevention mechanism and not a general
341 throttling control (packets are dropped, not queued).
344 <LI><B>cluster_address
</B> (ip address)
<BR>
345 Multicast cluster address (default:
239.192.13.13). See the section
346 on
<A HREF=
"#Clustering">Clustering
</A> for more information.
349 <LI><B>cluster_interface
</B> (string)
<BR>
350 Interface for cluster packets (default: eth0).
353 <LI><B>cluster_mcast_ttl
</B> (int)
<BR>
354 TTL for multicast packets (default:
1).
357 <LI><B>cluster_hb_interval
</B> (int)
<BR>
358 Interval in tenths of a second between cluster heartbeat/pings.
361 <LI><B>cluster_hb_timeout
</B> (int)
<BR>
362 Cluster heartbeat timeout in tenths of a second. A new master will be
363 elected when this interval has been passed without seeing a heartbeat
367 <LI><B>cluster_master_min_adv
</B> (int)
<BR>
368 Determines the minumum number of up to date slaves required before the
369 master will drop routes (default:
1).
372 <LI><B>echo_timeout
</B> (int)
<BR>
373 Time between last packet sent and LCP ECHO generation
374 (default:
10 (seconds)).
377 <LI><B>idle_echo_timeout
</B> (int)
<BR>
378 Drop sessions who have not responded within idle_echo_timeout seconds
379 (default:
240 (seconds))
382 <LI><B>bind_address_remotelns
</B> (ip address)
<BR>
383 Address of the interface to listen the remote LNS tunnels.
384 If no address is given, all interfaces are listened (Any Address).
387 <LI><B>bind_portremotelns
</B> (short)
<BR>
388 Port to bind for the Remote LNS (default:
65432).
391 <LI><B>auth_tunnel_change_addr_src
</B> (boolean)
<BR>
392 This parameter authorize to change the source IP of the tunnels l2tp.
393 This parameter can be used when the remotes BAS/LAC are l2tpns server
394 configured in cluster mode, but that the interface to remote LNS are
395 not clustered (the tunnel can be coming from different source IP)
401 <P>The REMOTES LNS configuration is entered by the command:
402 <DL> <DD><B>setforward
</B> <I>MASK
</I> <I>IP
</I> <I>PORT
</I> <I>SECRET
</I> </DL>
404 where
<I>MASK
</I> specifies the mask of users who have forwarded to
405 remote LNS (ex: /myISP@company.com).
</BR>
406 where
<I>IP
</I> specifies the IP of the remote LNS (ex:
66.66.66.55).
</BR>
407 where
<I>PORT
</I> specifies the L2TP Port of the remote LNS
408 (Normally should be
1701) (ex:
1701).
</BR>
409 where
<I>SECRET
</I> specifies the secret password the remote LNS (ex: mysecret).
</BR>
411 <P>BGP routing configuration is entered by the command:
412 The routing configuration section is entered by the command
413 <DL><DD><B>router bgp
</B> <I>as
</I></DL>
414 where
<I>as
</I> specifies the local AS number.
416 <P>Subsequent lines prefixed with
417 <DL><DD><B>neighbour
</B> <I>peer
</I></DL>
418 define the attributes of BGP neighhbours. Valid commands are:
420 <DD><B>neighbour
</B> <I>peer
</I> <B>remote-as
</B> <I>as
</I>
421 <DD><B>neighbout
</B> <I>peer
</I> <B>timers
</B> <I>keepalive hold
</I>
424 Where
<I>peer
</I> specifies the BGP neighbour as either a hostname or
425 IP address,
<I>as
</I> is the remote AS number and
<I>keepalive
</I>,
426 <I>hold
</I> are the timer values in seconds.
428 <P>Named access-lists are configured using one of the commands:
430 <DD><B>ip access-list standard
</B> <I>name
</I>
431 <DD><B>ip access-list extended
</B> <I>name
</I>
434 <P>Subsequent lines prefixed with
<B>permit
</B> or
<B>deny
</B>
435 define the body of the access-list. Standard access-list syntax:
437 <DD>{
<B>permit
</B>|
<B>deny
</B>}
438 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
439 [{
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>}]
442 Extended access-lists:
444 <DIV STYLE=
"margin-left: 4em; text-indent: -2em">
445 <P>{
<B>permit
</B>|
<B>deny
</B>}
<B>ip
</B>
446 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
447 {
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>} [
<B>fragments
</B>]
448 <P>{
<B>permit
</B>|
<B>deny
</B>}
<B>udp
</B>
449 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
450 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
451 {
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>}
452 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
454 <P>{
<B>permit
</B>|
<B>deny
</B>}
<B>tcp
</B>
455 {
<I>host
</I>|
<I>source source-wildcard
</I>|
<B>any
</B>}
456 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
457 {
<I>host
</I>|
<I>destination destination-wildcard
</I>|
<B>any
</B>}
458 [{
<B>eq
</B>|
<B>neq
</B>|
<B>gt
</B>|
<B>lt
</B>}
<I>port
</I>|
<B>range
</B> <I>from
</I> <I>to
</I>]
459 [{
<B>established
</B>|{
<B>match-any
</B>|
<B>match-all
</B>}
460 {
<B>+
</B>|
<B>-
</B>}{
<B>fin
</B>|
<B>syn
</B>|
<B>rst
</B>|
<B>psh
</B>|
<B>ack
</B>|
<B>urg
</B>}
461 ...|
<B>fragments
</B>]
464 <H3 ID=
"users">users
</H3>
466 Usernames and passwords for the command-line interface are stored in
467 this file. The format is
<I>username
</I><B>:
</B><I>password
</I> where
468 <I>password
</I> may either by plain text, an MD5 digest (prefixed by
469 <B>$
1</B><I>salt
</I><B>$
</B>) or a DES password, distinguished from
470 plain text by the prefix
<B>{crypt}
</B>.
<P>
472 The username
<B>enable
</B> has a special meaning and is used to set
473 the enable password.
<P>
475 <B>Note:
</B> If this file doesn't exist, then anyone who can get to
476 port
23 will be allowed access without a username / password.
<P>
478 <H3 ID=
"ip-pool">ip_pool
</H3>
480 This file is used to configure the IP address pool which user
481 addresses are assigned from. This file should contain either an IP
482 address or a CIDR network per line. e.g.:
<P>
493 Keep in mind that l2tpns can only handle
65535 connections per
494 process, so don't put more than
65535 IP addresses in the
495 configuration file. They will be wasted.
497 <H3 ID=
"build-garden">build-garden
</H3>
499 The garden plugin on startup creates a NAT table called
"garden" then
500 sources the
<B>build-garden
</B> script to populate that table. All
501 packets from gardened users will be sent through this table. Example:
504 iptables -t nat -A garden -p tcp -m tcp --dport
25 -j DNAT --to
192.168.1.1
505 iptables -t nat -A garden -p udp -m udp --dport
53 -j DNAT --to
192.168.1.1
506 iptables -t nat -A garden -p tcp -m tcp --dport
53 -j DNAT --to
192.168.1.1
507 iptables -t nat -A garden -p tcp -m tcp --dport
80 -j DNAT --to
192.168.1.1
508 iptables -t nat -A garden -p tcp -m tcp --dport
110 -j DNAT --to
192.168.1.1
509 iptables -t nat -A garden -p tcp -m tcp --dport
443 -j DNAT --to
192.168.1.1
510 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to
192.168.1.1
511 iptables -t nat -A garden -p icmp -j ACCEPT
512 iptables -t nat -A garden -j DROP
515 <H2 ID=
"ControllingtheProcess">Controlling the Process
</H2>
517 A running l2tpns process can be controlled in a number of ways. The primary
518 method of control is by the Command-Line Interface (CLI).
<P>
520 You can also remotely send commands to modules via the nsctl client
523 Also, there are a number of signals that l2tpns understands and takes action
524 when it receives them.
526 <H3 ID=
"Command-LineInterface">Command-Line Interface
</H3>
528 You can access the command line interface by telnet'ing to port
23.
529 There is no IP address restriction, so it's a good idea to firewall
530 this port off from anyone who doesn't need access to it. See
531 <A HREF=
"#users">users
</A> for information on restricting access based
532 on a username and password.
<P>
534 The CLI gives you real-time control over almost everything in
535 the process. The interface is designed to look like a Cisco
536 device, and supports things like command history, line editing and
537 context sensitive help. This is provided by linking with the
538 <A HREF=
"http://sourceforge.net/projects/libcli">libcli
</A>
539 library. Some general documentation of the interface is
540 <A HREF=
"http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
543 After you have connected to the telnet port (and perhaps logged in), you
544 will be presented with a
<I>hostname
</I><B>></B> prompt.
<P>
546 Enter
<EM>help
</EM> to get a list of possible commands. A brief
547 overview of the more important commands follows:
550 <LI><B>show session
</B><BR>
551 Without specifying a session ID, this will list all tunnels currently
552 connected. If you specify a session ID, you will be given all
553 information on a single tunnel. Note that the full session list can
554 be around
185 columns wide, so you should probably use a wide terminal
555 to see the list properly.
<P>
556 The columns listed in the overview are:
558 <TR><TD><B>SID
</B></TD><TD>Session ID
</TD></TR>
559 <TR><TD><B>TID
</B></TD><TD>Tunnel ID - Use with
<EM>show tunnel tid
</EM></TD></TR>
560 <TR><TD><B>Username
</B></TD><TD>The username given in the PPP
561 authentication. If this is *, then LCP authentication has not
563 <TR><TD><B>IP
</B></TD><TD>The IP address given to the session. If
564 this is
0.0.0.0, LCP negotiation has not completed.
</TD></TR>
565 <TR><TD><B>I
</B></TD><TD>Intercept - Y or N depending on whether the
566 session is being snooped. See
<EM>snoop
</EM>.
</TD></TR>
567 <TR><TD><B>T
</B></TD><TD>Throttled - Y or N if the session is
568 currently throttled. See
<EM>throttle
</EM>.
</TD></TR>
569 <TR><TD><B>G
</B></TD><TD>Walled Garden - Y or N if the user is
570 trapped in the walled garden. This field is present even if the
571 garden module is not loaded.
</TD></TR>
572 <TR><TD><B>opened
</B></TD><TD>The number of seconds since the
573 session started
</TD></TR>
574 <TR><TD><B>downloaded
</B></TD><TD>Number of bytes downloaded by the user
</TD></TR>
575 <TR><TD><B>uploaded
</B></TD><TD>Number of bytes uploaded by the user
</TD></TR>
576 <TR><TD><B>idle
</B></TD><TD>The number of seconds since traffic was
577 detected on the session
</TD></TR>
578 <TR><TD><B>LAC
</B></TD><TD>The IP address of the LAC the session is
579 connected to.
</TD></TR>
580 <TR><TD><B>CLI
</B></TD><TD>The Calling-Line-Identification field
581 provided during the session setup. This field is generated by the
587 <LI><B>show users
</B><BR>
588 With no arguments, display a list of currently connected users. If an
589 argument is given, the session details for the given username are
593 <LI><B>show tunnel
</B><BR>
594 This will show all the open tunnels in a summary, or detail on a single
595 tunnel if you give a tunnel id.
<P>
596 The columns listed in the overview are:
598 <TR><TD><B>TID
</B></TD><TD>Tunnel ID
</TD></TR>
599 <TR><TD><B>Hostname
</B></TD><TD>The hostname for the tunnel as
600 provided by the LAC. This has no relation to DNS, it is just
601 a text field.
</TD></TR>
602 <TR><TD><B>IP
</B></TD><TD>The IP address of the LAC
</TD></TR>
603 <TR><TD><B>State
</B></TD><TD>Tunnel state - Free, Open, Dieing,
605 <TR><TD><B>Sessions
</B></TD><TD>The number of open sessions on the
611 <LI><B>show pool
</B><BR>
612 Displays the current IP address pool allocation. This will only display
613 addresses that are in use, or are reserved for re-allocation to a
614 disconnected user.
<P>
615 If an address is not currently in use, but has been used, then in the User
616 column the username will be shown in square brackets, followed by the time
617 since the address was used:
619 IP Address Used Session User
620 192.168.100.6 N [joe.user]
1548s
625 <LI><B>show radius
</B><BR>
626 Show a summary of the in-use RADIUS sessions. This list should not be very
627 long, as RADIUS sessions should be cleaned up as soon as they are used. The
630 <TR><TD><B>Radius
</B></TD><TD>The ID of the RADIUS request. This is
631 sent in the packet to the RADIUS server for identification.
</TD></TR>
632 <TR><TD><B>State
</B></TD><TD>The state of the request - WAIT, CHAP,
633 AUTH, IPCP, START, STOP, NULL.
</TD></TR>
634 <TR><TD><B>Session
</B></TD><TD>The session ID that this RADIUS
635 request is associated with
</TD></TR>
636 <TR><TD><B>Retry
</B></TD><TD>If a response does not appear to the
637 request, it will retry at this time. This is a unix timestamp.
</TD></TR>
638 <TR><TD><B>Try
</B></TD><TD>Retry count. The RADIUS request is
639 discarded after
3 retries.
</TD></TR>
644 <LI><B>show running-config
</B><BR>
645 This will list the current running configuration. This is in a format that
646 can either be pasted into the configuration file, or run directly at the
651 <LI><B>show counters
</B><BR>
652 Internally, counters are kept of key values, such as bytes and packets
653 transferred, as well as function call counters. This function displays all
654 these counters, and is probably only useful for debugging.
<P>
655 You can reset these counters by running
<EM>clear counters
</EM>.
659 <LI><B>show cluster
</B><BR>
660 Show cluster status. Shows the cluster state for this server
661 (Master/Slave), information about known peers and (for slaves) the
662 master IP address, last packet seen and up-to-date status.
<P>
663 See
<A HREF=
"#Clustering">Clustering
</A> for more information.
667 <LI><B>write memory
</B><BR>
668 This will write the current running configuration to the config file
669 <B>startup-config
</B>, which will be run on a restart.
674 You must specify a username, IP address and port. All packets for the
675 current session for that username will be forwarded to the given
676 host/port. Specify
<EM>no snoop username
</EM> to disable interception
679 If you want interception to be permanent, you will have to modify the RADIUS
680 response for the user. See
<A HREF=
"#Interception">Interception
</A>.
684 <LI><B>throttle
</B><BR>
685 You must specify a username, which will be throttled for the current
686 session. Specify
<EM>no throttle username
</EM> to disable throttling
687 for the current session.
<P>
689 If you want throttling to be permanent, you will have to modify the
690 RADIUS response for the user. See
<A HREF=
"#Throttling">Throttling
</A>.
694 <LI><B>drop session
</B><BR>
695 This will cleanly disconnect a session. You must specify a session id, which
696 you can get from
<EM>show session
</EM>. This will send a disconnect message
701 <LI><B>drop tunnel
</B><BR>
702 This will cleanly disconnect a tunnel, as well as all sessions on that
703 tunnel. It will send a disconnect message for each session individually, and
704 after
10 seconds it will send a tunnel disconnect message.
708 <LI><B>uptime
</B><BR>
709 This will show how long the l2tpns process has been running, and the current
710 bandwidth utilization:
712 17:
10:
35 up
8 days,
2212 users, load average:
0.21,
0.17,
0.16
713 Bandwidth: UDP-ETH:
6/
6 ETH-UDP:
13/
13 TOTAL:
37.6 IN:
3033 OUT:
2569
715 The bandwidth line contains
4 sets of values.
<BR>
716 UDP-ETH is the current bandwidth going from the LAC to the ethernet
717 (user uploads), in mbits/sec.
<BR>
718 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
720 TOTAL is the total aggregate bandwidth in mbits/s.
<BR>
721 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
723 These counters are updated every second.
727 <LI><B>configure terminal
</B><BR>
728 Enter configuration mode. Use
<EM>exit
</EM> or ^Z to exit this mode.
729 The following commands are valid in this mode:
<P>
732 <LI><B>load plugin
</B><BR>
733 Load a plugin. You must specify the plugin name, and it will search in
734 /usr/lib/l2tpns for
<EM>plugin
</EM>.so. You can unload a loaded plugin with
735 <EM>remove plugin
</EM>.
740 Set a configuration variable. You must specify the variable name, and
741 the value. If the value contains any spaces, you should quote the
742 value with double (
") or single (') quotes.<P>
744 You can set any <A HREF="#startup-config
">startup-config</A> value in
745 this way, although some may require a restart to take effect.<P>
749 <H3 ID="nsctl
">nsctl</H3>
751 nsctl allows messages to be passed to plugins.<P>
753 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
754 <STRONG>nsctl</STRONG>(8) for more details.<P>
756 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
757 <EM>help</EM>. Any other commands are passed to plugins for processing.
759 <H3 ID="Signals
">Signals</H3>
761 While the process is running, you can send it a few different signals, using
767 The signals understood are:
769 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
770 <DT>SIGTERM, SIGINT</DT><DD>Stop process. Tunnels and sessions are not
771 terminated. This signal should be used to stop l2tpns on a
772 <A HREF="#Clustering
">cluster node</A> where there are other machines to
773 continue handling traffic.</DD>
774 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
778 <H2 ID="Throttling
">Throttling</H2>
780 l2tpns contains support for slowing down user sessions to whatever speed you
781 desire. You must first enable the global setting <EM>throttle_speed</EM>
782 before this will be activated.<P>
784 If you wish a session to be throttled permanently, you should set the
785 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes
"</B>, which
786 will be handled by the <EM>autothrottle</EM> module.<P>
788 Otherwise, you can enable and disable throttling an active session using
789 the <EM>throttle</EM> CLI command.<P>
791 <H2 ID="Interception
">Interception</H2>
793 You may have to deal with legal requirements to be able to intercept a
794 user's traffic at any time. l2tpns allows you to begin and end interception
795 on the fly, as well as at authentication time.<P>
797 When a user is being intercepted, a copy of every packet they send and
798 receive will be sent wrapped in a UDP packet to the IP address and port set
799 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
802 The UDP packet contains just the raw IP frame, with no extra headers.<P>
804 To enable interception on a connected user, use the <EM>snoop username</EM>
805 and <EM>no snoop username</EM> CLI commands. These will enable interception
808 If you wish the user to be intercepted whenever they reconnect, you will
809 need to modify the RADIUS response to include the Vendor-Specific value
810 <B>Cisco-Avpair="intercept=yes
"</B>. For this feature to be enabled,
811 you need to have the <EM>autosnoop</EM> module loaded.<P>
813 <H2 ID="Authentication
">Authentication</H2>
815 Whenever a session connects, it is not fully set up until authentication is
816 completed. The remote end must send a PPP CHAP or PPP PAP authentication
817 request to l2tpns.<P>
819 This request is sent to the RADIUS server, which will hopefully respond with
820 Auth-Accept or Auth-Reject.<P>
822 If Auth-Accept is received, the session is set up and an IP address is
823 assigned. The RADIUS server can include a Framed-IP-Address field in the
824 reply, and that address will be assigned to the client. It can also include
825 specific DNS servers, and a Framed-Route if that is required.<P>
827 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
828 at which point they should disconnect. The exception to this is when the
829 walled garden module is loaded, in which case the user still receives the
830 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
831 should not receive any service.<P>
833 The RADIUS reply can also contain a Vendor-Specific attribute called
834 Cisco-Avpair. This field is a freeform text field that most Cisco
835 devices understand to contain configuration instructions for the session. In
836 the case of l2tpns it is expected to be of the form
838 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
841 Each key-value pair is separated and passed to any modules loaded. The
842 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
843 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
844 a user who is to be throttled and intercepted, the Cisco-Avpair value should
847 intercept=yes,throttle=yes
850 <H2 ID="Plugins
">Plugins</H2>
852 So as to make l2tpns as flexible as possible (I know the core code is pretty
853 difficult to understand), it includes a plugin API, which you can use to
854 hook into certain events.<P>
856 There are a few example modules included - autosnoop, autothrottle and
859 When an event happens that has a hook, l2tpns looks for a predefined
860 function name in every loaded module, and runs them in the order the modules
863 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
864 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
865 modules should be run for this event.<P>
866 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
867 no further processing should be done for this event. <EM>Use this with care.</EM>
869 Every event function called takes a specific structure named
870 param_<EM>event</EM>, which varies in content with each event. The
871 function name for each event will be <B>plugin_<EM>event</EM></B>,
872 so for the event <EM>timer</EM>, the function declaration should look like:
874 int plugin_timer(struct param_timer *data);
877 A list of the available events follows, with a list of all the fields in the
879 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
880 <TABLE CELLSPACING=1 CELLPADDING=3>
881 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
882 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
883 <TD>This is called after a RADIUS response has been
884 received, but before it has been processed by the
885 code. This will allow you to modify the response in
894 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
895 <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
899 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
900 <TD>This is called after a RADIUS response has been
901 received, and the basic checks have been performed. This
902 is what the garden module uses to force authentication
910 <DT>auth_allowed<DD>This is already set to true or
911 false depending on whether authentication has been
912 allowed so far. You can set this to 1 or 0 to force
913 allow or disallow authentication
914 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
918 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
919 <TD>This is called whenever a session receives a
920 packet. <FONT COLOR=RED>Use this sparingly, as this will
921 seriously slow down the system.</FONT>
927 <DT>buf<DD>The raw packet data
928 <DT>len<DD>The length of buf
932 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
933 <TD>This is called whenever a session sends a
934 packet. <FONT COLOR=RED>Use this sparingly, as this will
935 seriously slow down the system.</FONT>
941 <DT>buf<DD>The raw packet data
942 <DT>len<DD>The length of buf
946 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
947 <TD>This is run every second, no matter what is happening.
948 This is called from a signal handler, so make sure anything
953 <DT>time_now<DD>The current unix timestamp
957 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
958 <TD>This is called after a session is fully set up. The
959 session is now ready to handle traffic.
968 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
969 <TD>This is called when a session is about to be shut down.
970 This may be called multiple times for the same session.
979 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
980 <TD>This is called whenever a RADIUS response includes a
981 Cisco-Avpair value. The value is split up into
982 <EM>key=value</EM> pairs, and each is processed through all
994 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
995 <TD>This is called whenever a RADIUS CoA request is
996 received to reset any options to default values before
997 the new values are applied.
1006 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1007 <TD>This is called in whenever a nsctl packet is received.
1008 This should handle the packet and form a response if
1013 <DT>iam_master<DD>Cluster master status
1014 <DT>argc<DD>The number of arguments
1015 <DT>argv<DD>Arguments
1016 <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1017 <DT>additional<DD>Extended response text
1024 <H2 ID="WalledGarden
">Walled Garden</H2>
1026 Walled Garden is implemented so that you can provide perhaps limited service
1027 to sessions that incorrectly authenticate.<P>
1029 Whenever a session provides incorrect authentication, and the
1030 RADIUS server responds with Auth-Reject, the walled garden module
1031 (if loaded) will force authentication to succeed, but set the flag
1032 <EM>garden</EM> in the session structure, and adds an iptables rule to
1033 the <B>garden_users</B> chain to force all packets for the session's IP
1034 address to traverse the <B>garden</B> chain.<P>
1036 This doesn't <EM>just work</EM>. To set this all up, you will to
1037 setup the <B>garden</B> nat table with the
1038 <A HREF="#build-garden
">build-garden</A> script with rules to limit
1039 user's traffic. For example, to force all traffic except DNS to be
1040 forwarded to 192.168.1.1, add these entries to your
1041 <EM>build-garden</EM>:
1043 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1044 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1047 l2tpns will add entries to the garden_users chain as appropriate.<P>
1049 You can check the amount of traffic being captured using the following
1052 iptables -t nat -L garden -nvx
1055 <H2 ID="Filtering
">Filtering</H2>
1057 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1058 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
1059 access-list <I>filter</I> should be applied to traffic from the
1060 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1063 <H2 ID="Clustering
">Clustering</H2>
1065 An l2tpns cluster consists of of one* or more servers configured with
1066 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1068 *A stand-alone server is simply a degraded cluster.<P>
1070 Initially servers come up as cluster slaves, and periodically (every
1071 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1072 containing the start time of the process to the multicast
1073 <B>cluster_address</B>.<P>
1075 A cluster master sends heartbeat rather than ping packets, which
1076 contain those session and tunnel changes since the last heartbeat.<P>
1078 When a slave has not seen a heartbeat within
1079 <B>cluster_hb_timeout</B>/10 seconds it "elects
" a new master by
1080 examining the list of peers it has seen pings from and determines
1081 which of these and itself is the "best
" candidate to be master.
1082 "Best
" in this context means the server with the highest uptime (the
1083 highest IP address is used as a tie-breaker in the case of equal
1086 After discovering a master, and determining that it is up-to-date (has
1087 seen an update for all in-use sessions and tunnels from heartbeat
1088 packets) will raise a route (see <A HREF="#Routing
">Routing</A>) for
1089 the <B>bind_address</B> and for all addresses/networks in
1090 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1091 the session state, as well as packets for throttled or gardened
1092 sessions are forwarded to the master for handling. In addition, byte
1093 counters for session traffic are periodically forwarded.<P>
1095 A master, when determining that it has at least one up-to-date slave
1096 will drop all routes (raising them again if all slaves disappear) and
1097 subsequently handle only packets forwarded to it by the slaves.<P>
1099 <H2 ID="Routing
">Routing</H2>
1100 If you are running a single instance, you may simply statically route
1101 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1104 For a cluster, configure the members as BGP neighbours on your router
1105 and configure multi-path load-balancing. Cisco uses "maximum-paths
1106 ibgp
" for IBGP. If this is not supported by your IOS revision, you
1107 can use "maximum-paths
" (which works for EBGP) and set
1108 <B>as_number</B> to a private value such as 64512.<P>
1110 <H2 ID="Performance
">Performance</H2>
1112 Performance is great.<P>
1114 I'd like to include some pretty graphs here that show a linear performance
1115 increase, with no impact by number of connected sessions.<P>
1117 That's really what it looks like.<P>
1121 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%
20Documentation
">l2tpns-users@lists.sourceforge.net</A>