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25 <H1>L2TPNS Manual</H1>
26 <OL>
27 <LI><A HREF="#Overview">Overview</A></LI>
28 <LI><A HREF="#Installation">Installation</A>
29 <OL>
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>
34 </OL>
35 </LI>
36 <LI><A HREF="#Configuration">Configuration</A>
37 <OL>
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>
42 </OL>
43 </LI>
44 <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
45 <OL>
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>
49 </OL>
50 </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>
60 </OL>
61
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>
65
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>
69
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>
75
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>
79
80 This allows it to scale extremely well to very high loads and very high
81 numbers of connections.<P>
82
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
85 included.<P>
86
87 <BR>
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>
91
92 <H2 ID="Installation">Installation</H2>
93 <H3 ID="Requirements">Requirements</H3>
94
95 <OL>
96 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
97 compiled in, or as a module.</LI>
98
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>
101 </OL>
102
103 <H3 ID="Compile">Compile</H3>
104
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>
108
109 <H3 ID="Install">Install</H3>
110
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>
115
116 You will definately need to edit the configuration files before you
117 start. See the <A HREF="#Configuration">Configuration</A> section for
118 more information.<P>
119
120 <H3 ID="Running">Running</H3>
121
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>
124
125 By default there is no log destination set, so all log messages will go to
126 stdout.<P>
127
128 <H2 ID="Configuration">Configuration</H2>
129
130 All configuration of the software is done from the files installed into
131 /etc/l2tpns.
132
133 <H3 ID="startup-config">startup-config</H3>
134
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>
141
142 A list of the possible configuration directives follows. Each of these
143 should be set by a line like:<P>
144 <PRE>
145 set configstring "value"
146 set ipaddress 192.168.1.1
147 set boolean true
148 </PRE>
149
150 <P>
151 <UL>
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:
156 <OL>
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>
163 </OL><P>
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.
167 </LI>
168
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.
174 </LI>
175
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.
179 </LI>
180
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.
185 </LI>
186
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.
190 </LI>
191
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 &sect;4.1 of
196 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661</a>.
197 </LI>
198
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.
204 </LI>
205
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).
216 </LI>
217
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.
224 </LI>
225
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
230 session is closed.
231 </LI>
232
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.
236 </LI>
237
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>).
241 </LI>
242
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>).
246 </LI>
247
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.
252 </LI>
253
254 <LI><B>bind_address</B> (ip address)<BR>
255 When the tun interface is created, it is assigned the address
256 specified here. If no address is given, 1.1.1.1 is used. Packets
257 containing user traffic should be routed via this address if given,
258 otherwise the primary address of the machine.
259 </LI>
260
261 <LI><B>peer_address</B> (ip address)<BR>
262 Address to send to clients as the default gateway.
263 </L1>
264
265 <LI><B>send_garp</B> (boolean)<BR>
266 Determines whether or not to send a gratuitous ARP for the
267 bind_address when the server is ready to handle traffic (default:
268 true).<BR>
269 This value is ignored if BGP is configured.
270 </LI>
271
272 <LI><B>throttle_speed</B> (int)<BR>
273 Sets the default speed (in kbits/s) which sessions will be limited to.
274 If this is set to 0, then throttling will not be used at all. Note:
275 You can set this by the CLI, but changes will not affect currently
276 connected users.
277 </LI>
278
279 <LI><B>throttle_buckets</B> (int)<BR>
280 Number of token buckets to allocate for throttling. Each throttled
281 session requires two buckets (in and out).
282 </LI>
283
284 <LI><B>accounting_dir</B> (string)<BR>
285 If set to a directory, then every 5 minutes the current usage for
286 every connected use will be dumped to a file in this directory. Each
287 file dumped begins with a header, where each line is prefixed by #.
288 Following the header is a single line for every connected user, fields
289 separated by a space.<BR> The fields are username, ip, qos,
290 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
291 2 if the user is throttled.
292 </LI>
293
294 <LI><B>setuid</B> (int)<BR>
295 After starting up and binding the interface, change UID to this. This
296 doesn't work properly.
297 </LI>
298
299 <LI><B>dump_speed</B> (boolean)<BR>
300 If set to true, then the current bandwidth utilization will be logged every
301 second. Even if this is disabled, you can see this information by running
302 the <EM>uptime</EM> command on the CLI.
303 </LI>
304
305 <LI><B>multi_read_count</B> (int)<BR>
306 Number of packets to read off each of the UDP and TUN fds when
307 returned as readable by select (default: 10). Avoids incurring the
308 unnecessary system call overhead of select on busy servers.
309 </LI>
310
311 <LI><B>scheduler_fifo</B> (boolean)<BR>
312 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
313 causes the kernel to immediately preempt any currently running SCHED_OTHER
314 (normal) process in favour of l2tpns when it becomes runnable.
315 Ignored on uniprocessor systems.
316 </LI>
317
318 <LI><B>lock_pages</B> (boolean)<BR>
319 Keep all pages mapped by the l2tpns process in memory.
320 </LI>
321
322 <LI><B>icmp_rate</B> (int)<BR>
323 Maximum number of host unreachable ICMP packets to send per second.
324 </LI>
325
326 <LI><B>packet_limit</B> (int><BR>
327 Maximum number of packets of downstream traffic to be handled each
328 tenth of a second per session. If zero, no limit is applied (default:
329 0). Intended as a DoS prevention mechanism and not a general
330 throttling control (packets are dropped, not queued).
331 </LI>
332
333 <LI><B>cluster_address</B> (ip address)<BR>
334 Multicast cluster address (default: 239.192.13.13). See the section
335 on <A HREF="#Clustering">Clustering</A> for more information.
336 </LI>
337
338 <LI><B>cluster_interface</B> (string)<BR>
339 Interface for cluster packets (default: eth0).
340 </LI>
341
342 <LI><B>cluster_mcast_ttl</B> (int)<BR>
343 TTL for multicast packets (default: 1).
344 </LI>
345
346 <LI><B>cluster_hb_interval</B> (int)<BR>
347 Interval in tenths of a second between cluster heartbeat/pings.
348 </LI>
349
350 <LI><B>cluster_hb_timeout</B> (int)<BR>
351 Cluster heartbeat timeout in tenths of a second. A new master will be
352 elected when this interval has been passed without seeing a heartbeat
353 from the master.
354 </LI>
355
356 <LI><B>cluster_master_min_adv</B> (int)<BR>
357 Determines the minumum number of up to date slaves required before the
358 master will drop routes (default: 1).
359 </LI>
360 </UL>
361
362 <P>BGP routing configuration is entered by the command:
363 The routing configuration section is entered by the command
364 <DL><DD><B>router bgp</B> <I>as</I></DL>
365 where <I>as</I> specifies the local AS number.
366
367 <P>Subsequent lines prefixed with
368 <DL><DD><B>neighbour</B> <I>peer</I></DL>
369 define the attributes of BGP neighhbours. Valid commands are:
370 <DL>
371 <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
372 <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
373 </DL>
374
375 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
376 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
377 <I>hold</I> are the timer values in seconds.
378
379 <P>Named access-lists are configured using one of the commands:
380 <DL>
381 <DD><B>ip access-list standard</B> <I>name</I>
382 <DD><B>ip access-list extended</B> <I>name</I>
383 </DL>
384
385 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
386 define the body of the access-list. Standard access-list syntax:
387 <DL>
388 <DD>{<B>permit</B>|<B>deny</B>}
389 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
390 [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
391 </DL>
392
393 Extended access-lists:
394
395 <DIV STYLE="margin-left: 4em; text-indent: -2em">
396 <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
397 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
398 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
399 <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
400 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
401 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
402 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
403 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
404 [<B>fragments</B>]
405 <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
406 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
407 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
408 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
409 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
410 [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
411 {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
412 ...|<B>fragments</B>]
413 </DIV>
414
415 <H3 ID="users">users</H3>
416
417 Usernames and passwords for the command-line interface are stored in
418 this file. The format is <I>username</I><B>:</B><I>password</I> where
419 <I>password</I> may either by plain text, an MD5 digest (prefixed by
420 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
421 plain text by the prefix <B>{crypt}</B>.<P>
422
423 The username <B>enable</B> has a special meaning and is used to set
424 the enable password.<P>
425
426 <B>Note:</B> If this file doesn't exist, then anyone who can get to
427 port 23 will be allowed access without a username / password.<P>
428
429 <H3 ID="ip-pool">ip_pool</H3>
430
431 This file is used to configure the IP address pool which user
432 addresses are assigned from. This file should contain either an IP
433 address or a CIDR network per line. e.g.:<P>
434
435 <PRE>
436 192.168.1.1
437 192.168.1.2
438 192.168.1.3
439 192.168.4.0/24
440 172.16.0.0/16
441 10.0.0.0/8
442 </PRE>
443
444 Keep in mind that l2tpns can only handle 65535 connections per
445 process, so don't put more than 65535 IP addresses in the
446 configuration file. They will be wasted.
447
448 <H3 ID="build-garden">build-garden</H3>
449
450 The garden plugin on startup creates a NAT table called "garden" then
451 sources the <B>build-garden</B> script to populate that table. All
452 packets from gardened users will be sent through this table. Example:
453
454 <PRE>
455 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
456 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
457 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
458 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
459 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
460 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
461 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
462 iptables -t nat -A garden -p icmp -j ACCEPT
463 iptables -t nat -A garden -j DROP
464 </PRE>
465
466 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
467
468 A running l2tpns process can be controlled in a number of ways. The primary
469 method of control is by the Command-Line Interface (CLI).<P>
470
471 You can also remotely send commands to modules via the nsctl client
472 provided.<P>
473
474 Also, there are a number of signals that l2tpns understands and takes action
475 when it receives them.
476
477 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
478
479 You can access the command line interface by telnet'ing to port 23.
480 There is no IP address restriction, so it's a good idea to firewall
481 this port off from anyone who doesn't need access to it. See
482 <A HREF="#users">users</A> for information on restricting access based
483 on a username and password.<P>
484
485 The CLI gives you real-time control over almost everything in
486 the process. The interface is designed to look like a Cisco
487 device, and supports things like command history, line editing and
488 context sensitive help. This is provided by linking with the
489 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
490 library. Some general documentation of the interface is
491 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
492 here</A>.<P>
493
494 After you have connected to the telnet port (and perhaps logged in), you
495 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
496
497 Enter <EM>help</EM> to get a list of possible commands. A brief
498 overview of the more important commands follows:
499
500 <UL>
501 <LI><B>show session</B><BR>
502 Without specifying a session ID, this will list all tunnels currently
503 connected. If you specify a session ID, you will be given all
504 information on a single tunnel. Note that the full session list can
505 be around 185 columns wide, so you should probably use a wide terminal
506 to see the list properly.<P>
507 The columns listed in the overview are:
508 <TABLE>
509 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
510 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
511 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
512 authentication. If this is *, then LCP authentication has not
513 completed.</TD></TR>
514 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
515 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
516 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
517 session is being snooped. See <EM>snoop</EM>.</TD></TR>
518 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
519 currently throttled. See <EM>throttle</EM>.</TD></TR>
520 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
521 trapped in the walled garden. This field is present even if the
522 garden module is not loaded.</TD></TR>
523 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
524 session started</TD></TR>
525 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
526 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
527 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
528 detected on the session</TD></TR>
529 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
530 connected to.</TD></TR>
531 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
532 provided during the session setup. This field is generated by the
533 LAC.</TD></TR>
534 </TABLE>
535 <P>
536 </LI>
537
538 <LI><B>show users</B><BR>
539 With no arguments, display a list of currently connected users. If an
540 argument is given, the session details for the given username are
541 displayed.
542 </LI>
543
544 <LI><B>show tunnel</B><BR>
545 This will show all the open tunnels in a summary, or detail on a single
546 tunnel if you give a tunnel id.<P>
547 The columns listed in the overview are:
548 <TABLE>
549 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
550 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
551 provided by the LAC. This has no relation to DNS, it is just
552 a text field.</TD></TR>
553 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
554 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
555 Opening</TD></TR>
556 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
557 tunnel</TD></TR>
558 </TABLE>
559 <P>
560 </LI>
561
562 <LI><B>show pool</B><BR>
563 Displays the current IP address pool allocation. This will only display
564 addresses that are in use, or are reserved for re-allocation to a
565 disconnected user.<P>
566 If an address is not currently in use, but has been used, then in the User
567 column the username will be shown in square brackets, followed by the time
568 since the address was used:
569 <PRE>
570 IP Address Used Session User
571 192.168.100.6 N [joe.user] 1548s
572 </PRE>
573 <P>
574 </LI>
575
576 <LI><B>show radius</B><BR>
577 Show a summary of the in-use RADIUS sessions. This list should not be very
578 long, as RADIUS sessions should be cleaned up as soon as they are used. The
579 columns listed are:
580 <TABLE>
581 <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request. This is
582 sent in the packet to the RADIUS server for identification.</TD></TR>
583 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
584 AUTH, IPCP, START, STOP, NULL.</TD></TR>
585 <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
586 request is associated with</TD></TR>
587 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
588 request, it will retry at this time. This is a unix timestamp.</TD></TR>
589 <TR><TD><B>Try</B></TD><TD>Retry count. The RADIUS request is
590 discarded after 3 retries.</TD></TR>
591 </TABLE>
592 <P>
593 </LI>
594
595 <LI><B>show running-config</B><BR>
596 This will list the current running configuration. This is in a format that
597 can either be pasted into the configuration file, or run directly at the
598 command line.
599 <P>
600 </LI>
601
602 <LI><B>show counters</B><BR>
603 Internally, counters are kept of key values, such as bytes and packets
604 transferred, as well as function call counters. This function displays all
605 these counters, and is probably only useful for debugging.<P>
606 You can reset these counters by running <EM>clear counters</EM>.
607 <P>
608 </LI>
609
610 <LI><B>show cluster</B><BR>
611 Show cluster status. Shows the cluster state for this server
612 (Master/Slave), information about known peers and (for slaves) the
613 master IP address, last packet seen and up-to-date status.<P>
614 See <A HREF="#Clustering">Clustering</A> for more information.
615 <P>
616 </LI>
617
618 <LI><B>write memory</B><BR>
619 This will write the current running configuration to the config file
620 <B>startup-config</B>, which will be run on a restart.
621 <P>
622 </LI>
623
624 <LI><B>snoop</B><BR>
625 You must specify a username, IP address and port. All packets for the
626 current session for that username will be forwarded to the given
627 host/port. Specify <EM>no snoop username</EM> to disable interception
628 for the session.<P>
629
630 If you want interception to be permanent, you will have to modify the RADIUS
631 response for the user. See <A HREF="#Interception">Interception</A>.
632 <P>
633 </LI>
634
635 <LI><B>throttle</B><BR>
636 You must specify a username, which will be throttled for the current
637 session. Specify <EM>no throttle username</EM> to disable throttling
638 for the current session.<P>
639
640 If you want throttling to be permanent, you will have to modify the
641 RADIUS response for the user. See <A HREF="#Throttling">Throttling</A>.
642 <P>
643 </LI>
644
645 <LI><B>drop session</B><BR>
646 This will cleanly disconnect a session. You must specify a session id, which
647 you can get from <EM>show session</EM>. This will send a disconnect message
648 to the remote end.
649 <P>
650 </LI>
651
652 <LI><B>drop tunnel</B><BR>
653 This will cleanly disconnect a tunnel, as well as all sessions on that
654 tunnel. It will send a disconnect message for each session individually, and
655 after 10 seconds it will send a tunnel disconnect message.
656 <P>
657 </LI>
658
659 <LI><B>uptime</B><BR>
660 This will show how long the l2tpns process has been running, and the current
661 bandwidth utilization:
662 <PRE>
663 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
664 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
665 </PRE>
666 The bandwidth line contains 4 sets of values.<BR>
667 UDP-ETH is the current bandwidth going from the LAC to the ethernet
668 (user uploads), in mbits/sec.<BR>
669 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
670 downloads).<BR>
671 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
672 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
673 <P>
674 These counters are updated every second.
675 <P>
676 </LI>
677
678 <LI><B>configure terminal</B><BR>
679 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
680 The following commands are valid in this mode:<P>
681 </LI>
682
683 <LI><B>load plugin</B><BR>
684 Load a plugin. You must specify the plugin name, and it will search in
685 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
686 <EM>remove plugin</EM>.
687 <P>
688 </LI>
689
690 <LI><B>set</B><BR>
691 Set a configuration variable. You must specify the variable name, and
692 the value. If the value contains any spaces, you should quote the
693 value with double (") or single (') quotes.<P>
694
695 You can set any <A HREF="#startup-config">startup-config</A> value in
696 this way, although some may require a restart to take effect.<P>
697 </LI>
698 </UL>
699
700 <H3 ID="nsctl">nsctl</H3>
701
702 nsctl allows messages to be passed to plugins.<P>
703
704 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
705 <STRONG>nsctl</STRONG>(8) for more details.<P>
706
707 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
708 <EM>help</EM>. Any other commands are passed to plugins for processing.
709
710 <H3 ID="Signals">Signals</H3>
711
712 While the process is running, you can send it a few different signals, using
713 the kill command.
714 <PRE>
715 killall -HUP l2tpns
716 </PRE>
717
718 The signals understood are:
719 <DL>
720 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
721 <DT>SIGTERM, SIGINT</DT><DD>Stop process. Tunnels and sessions are not
722 terminated. This signal should be used to stop l2tpns on a
723 <A HREF="#Clustering">cluster node</A> where there are other machines to
724 continue handling traffic.</DD>
725 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
726 complete.</DD>
727 </DL>
728
729 <H2 ID="Throttling">Throttling</H2>
730
731 l2tpns contains support for slowing down user sessions to whatever speed you
732 desire. You must first enable the global setting <EM>throttle_speed</EM>
733 before this will be activated.<P>
734
735 If you wish a session to be throttled permanently, you should set the
736 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
737 will be handled by the <EM>autothrottle</EM> module.<P>
738
739 Otherwise, you can enable and disable throttling an active session using
740 the <EM>throttle</EM> CLI command.<P>
741
742 <H2 ID="Interception">Interception</H2>
743
744 You may have to deal with legal requirements to be able to intercept a
745 user's traffic at any time. l2tpns allows you to begin and end interception
746 on the fly, as well as at authentication time.<P>
747
748 When a user is being intercepted, a copy of every packet they send and
749 receive will be sent wrapped in a UDP packet to the IP address and port set
750 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
751 variables.<P>
752
753 The UDP packet contains just the raw IP frame, with no extra headers.<P>
754
755 To enable interception on a connected user, use the <EM>snoop username</EM>
756 and <EM>no snoop username</EM> CLI commands. These will enable interception
757 immediately.<P>
758
759 If you wish the user to be intercepted whenever they reconnect, you will
760 need to modify the RADIUS response to include the Vendor-Specific value
761 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
762 you need to have the <EM>autosnoop</EM> module loaded.<P>
763
764 <H2 ID="Authentication">Authentication</H2>
765
766 Whenever a session connects, it is not fully set up until authentication is
767 completed. The remote end must send a PPP CHAP or PPP PAP authentication
768 request to l2tpns.<P>
769
770 This request is sent to the RADIUS server, which will hopefully respond with
771 Auth-Accept or Auth-Reject.<P>
772
773 If Auth-Accept is received, the session is set up and an IP address is
774 assigned. The RADIUS server can include a Framed-IP-Address field in the
775 reply, and that address will be assigned to the client. It can also include
776 specific DNS servers, and a Framed-Route if that is required.<P>
777
778 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
779 at which point they should disconnect. The exception to this is when the
780 walled garden module is loaded, in which case the user still receives the
781 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
782 should not receive any service.<P>
783
784 The RADIUS reply can also contain a Vendor-Specific attribute called
785 Cisco-Avpair. This field is a freeform text field that most Cisco
786 devices understand to contain configuration instructions for the session. In
787 the case of l2tpns it is expected to be of the form
788 <PRE>
789 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
790 </PRE>
791
792 Each key-value pair is separated and passed to any modules loaded. The
793 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
794 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
795 a user who is to be throttled and intercepted, the Cisco-Avpair value should
796 contain:
797 <PRE>
798 intercept=yes,throttle=yes
799 </PRE>
800
801 <H2 ID="Plugins">Plugins</H2>
802
803 So as to make l2tpns as flexible as possible (I know the core code is pretty
804 difficult to understand), it includes a plugin API, which you can use to
805 hook into certain events.<P>
806
807 There are a few example modules included - autosnoop, autothrottle and
808 garden.<P>
809
810 When an event happens that has a hook, l2tpns looks for a predefined
811 function name in every loaded module, and runs them in the order the modules
812 were loaded.<P>
813
814 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
815 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
816 modules should be run for this event.<P>
817 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
818 no further processing should be done for this event. <EM>Use this with care.</EM>
819
820 Every event function called takes a specific structure named
821 param_<EM>event</EM>, which varies in content with each event. The
822 function name for each event will be <B>plugin_<EM>event</EM></B>,
823 so for the event <EM>timer</EM>, the function declaration should look like:
824 <PRE>
825 int plugin_timer(struct param_timer *data);
826 </PRE>
827
828 A list of the available events follows, with a list of all the fields in the
829 supplied structure:
830 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
831 <TABLE CELLSPACING=1 CELLPADDING=3>
832 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
833 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
834 <TD>This is called after a RADIUS response has been
835 received, but before it has been processed by the
836 code. This will allow you to modify the response in
837 some way.
838 </TD>
839 <TD>
840 <DL>
841 <DT>t<DD>Tunnel
842 <DT>s<DD>Session
843 <DT>username
844 <DT>password
845 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
846 <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
847 </DL>
848 </TD>
849 </TR>
850 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
851 <TD>This is called after a RADIUS response has been
852 received, and the basic checks have been performed. This
853 is what the garden module uses to force authentication
854 to be accepted.
855 </TD>
856 <TD>
857 <DL>
858 <DT>t<DD>Tunnel
859 <DT>s<DD>Session
860 <DT>username
861 <DT>auth_allowed<DD>This is already set to true or
862 false depending on whether authentication has been
863 allowed so far. You can set this to 1 or 0 to force
864 allow or disallow authentication
865 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
866 </DL>
867 </TD>
868 </TR>
869 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
870 <TD>This is called whenever a session receives a
871 packet. <FONT COLOR=RED>Use this sparingly, as this will
872 seriously slow down the system.</FONT>
873 </TD>
874 <TD>
875 <DL>
876 <DT>t<DD>Tunnel
877 <DT>s<DD>Session
878 <DT>buf<DD>The raw packet data
879 <DT>len<DD>The length of buf
880 </DL>
881 </TD>
882 </TR>
883 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
884 <TD>This is called whenever a session sends a
885 packet. <FONT COLOR=RED>Use this sparingly, as this will
886 seriously slow down the system.</FONT>
887 </TD>
888 <TD>
889 <DL>
890 <DT>t<DD>Tunnel
891 <DT>s<DD>Session
892 <DT>buf<DD>The raw packet data
893 <DT>len<DD>The length of buf
894 </DL>
895 </TD>
896 </TR>
897 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
898 <TD>This is run every second, no matter what is happening.
899 This is called from a signal handler, so make sure anything
900 you do is reentrant.
901 </TD>
902 <TD>
903 <DL>
904 <DT>time_now<DD>The current unix timestamp
905 </DL>
906 </TD>
907 </TR>
908 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
909 <TD>This is called after a session is fully set up. The
910 session is now ready to handle traffic.
911 </TD>
912 <TD>
913 <DL>
914 <DT>t<DD>Tunnel
915 <DT>s<DD>Session
916 </DL>
917 </TD>
918 </TR>
919 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
920 <TD>This is called when a session is about to be shut down.
921 This may be called multiple times for the same session.
922 </TD>
923 <TD>
924 <DL>
925 <DT>t<DD>Tunnel
926 <DT>s<DD>Session
927 </DL>
928 </TD>
929 </TR>
930 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
931 <TD>This is called whenever a RADIUS response includes a
932 Cisco-Avpair value. The value is split up into
933 <EM>key=value</EM> pairs, and each is processed through all
934 modules.
935 </TD>
936 <TD>
937 <DL>
938 <DT>t<DD>Tunnel
939 <DT>s<DD>Session
940 <DT>key
941 <DT>value
942 </DL>
943 </TD>
944 </TR>
945 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
946 <TD>This is called whenever a RADIUS CoA request is
947 received to reset any options to default values before
948 the new values are applied.
949 </TD>
950 <TD>
951 <DL>
952 <DT>t<DD>Tunnel
953 <DT>s<DD>Session
954 </DL>
955 </TD>
956 </TR>
957 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
958 <TD>This is called in whenever a nsctl packet is received.
959 This should handle the packet and form a response if
960 required.
961 </TD>
962 <TD>
963 <DL>
964 <DT>iam_master<DD>Cluster master status
965 <DT>argc<DD>The number of arguments
966 <DT>argv<DD>Arguments
967 <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
968 <DT>additional<DD>Extended response text
969 </DL>
970 </TD>
971 </TR>
972 </TABLE>
973 </TD></TR></TABLE>
974
975 <H2 ID="WalledGarden">Walled Garden</H2>
976
977 Walled Garden is implemented so that you can provide perhaps limited service
978 to sessions that incorrectly authenticate.<P>
979
980 Whenever a session provides incorrect authentication, and the
981 RADIUS server responds with Auth-Reject, the walled garden module
982 (if loaded) will force authentication to succeed, but set the flag
983 <EM>garden</EM> in the session structure, and adds an iptables rule to
984 the <B>garden_users</B> chain to force all packets for the session's IP
985 address to traverse the <B>garden</B> chain.<P>
986
987 This doesn't <EM>just work</EM>. To set this all up, you will to
988 setup the <B>garden</B> nat table with the
989 <A HREF="#build-garden">build-garden</A> script with rules to limit
990 user's traffic. For example, to force all traffic except DNS to be
991 forwarded to 192.168.1.1, add these entries to your
992 <EM>build-garden</EM>:
993 <PRE>
994 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
995 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
996 </PRE>
997
998 l2tpns will add entries to the garden_users chain as appropriate.<P>
999
1000 You can check the amount of traffic being captured using the following
1001 command:
1002 <PRE>
1003 iptables -t nat -L garden -nvx
1004 </PRE>
1005
1006 <H2 ID="Filtering">Filtering</H2>
1007
1008 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1009 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
1010 access-list <I>filter</I> should be applied to traffic from the
1011 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1012 customer.
1013
1014 <H2 ID="Clustering">Clustering</H2>
1015
1016 An l2tpns cluster consists of of one* or more servers configured with
1017 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1018
1019 *A stand-alone server is simply a degraded cluster.<P>
1020
1021 Initially servers come up as cluster slaves, and periodically (every
1022 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1023 containing the start time of the process to the multicast
1024 <B>cluster_address</B>.<P>
1025
1026 A cluster master sends heartbeat rather than ping packets, which
1027 contain those session and tunnel changes since the last heartbeat.<P>
1028
1029 When a slave has not seen a heartbeat within
1030 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1031 examining the list of peers it has seen pings from and determines
1032 which of these and itself is the "best" candidate to be master.
1033 "Best" in this context means the server with the highest uptime (the
1034 highest IP address is used as a tie-breaker in the case of equal
1035 uptimes).<P>
1036
1037 After discovering a master, and determining that it is up-to-date (has
1038 seen an update for all in-use sessions and tunnels from heartbeat
1039 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1040 the <B>bind_address</B> and for all addresses/networks in
1041 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1042 the session state, as well as packets for throttled or gardened
1043 sessions are forwarded to the master for handling. In addition, byte
1044 counters for session traffic are periodically forwarded.<P>
1045
1046 A master, when determining that it has at least one up-to-date slave
1047 will drop all routes (raising them again if all slaves disappear) and
1048 subsequently handle only packets forwarded to it by the slaves.<P>
1049
1050 <H2 ID="Routing">Routing</H2>
1051 If you are running a single instance, you may simply statically route
1052 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1053 arp).<P>
1054
1055 For a cluster, configure the members as BGP neighbours on your router
1056 and configure multi-path load-balancing. Cisco uses "maximum-paths
1057 ibgp" for IBGP. If this is not supported by your IOS revision, you
1058 can use "maximum-paths" (which works for EBGP) and set
1059 <B>as_number</B> to a private value such as 64512.<P>
1060
1061 <H2 ID="Performance">Performance</H2>
1062
1063 Performance is great.<P>
1064
1065 I'd like to include some pretty graphs here that show a linear performance
1066 increase, with no impact by number of connected sessions.<P>
1067
1068 That's really what it looks like.<P>
1069
1070 <BR>
1071 David Parrish<BR>
1072 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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