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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="#Walled Garden">Walled Garden</A></LI>
56 <LI><A HREF="#Clustering">Clustering</A></LI>
57 <LI><A HREF="#Routing">Routing</A></LI>
58 <LI><A HREF="#Performance">Performance</A></LI>
59 </OL>
60
61 <H2 ID="Overview">Overview</H2>
62 l2tpns is half of a complete L2TP implementation. It supports only the
63 LNS side of the connection.<P>
64
65 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
66 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns
67 implements PPP over L2TP only.<P>
68
69 There are a couple of other L2TP imlementations, of which <A
70 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
71 most popular. l2tpd also will handle being either end of a tunnel, and
72 is a lot more configurable than l2tpns. However, due to the way it works,
73 it is nowhere near as scalable.<P>
74
75 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
76 and send packets. Using some packet manipulation it doesn't require a
77 single interface per connection, as l2tpd does.<P>
78
79 This allows it to scale extremely well to very high loads and very high
80 numbers of connections.<P>
81
82 It also has a plugin architecture which allows custom code to be run
83 during processing. An example of this is in the walled garden module
84 included.<P>
85
86 <BR>
87 <EM>Documentation is not my best skill. If you find any problems
88 with this document, or if you wish to contribute, please email <A
89 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
90
91 <H2 ID="Installation">Installation</H2>
92 <H3 ID="Requirements">Requirements</H3>
93
94 <OL>
95 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
96 compiled in, or as a module.</LI>
97
98 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
99 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
100 </OL>
101
102 <H3 ID="Compile">Compile</H3>
103
104 You can generally get away with just running <B>make</B> from the source
105 directory. This will compile the daemon, associated tools and any modules
106 shipped with the distribution.<P>
107
108 <H3 ID="Install">Install</H3>
109
110 After you have successfully compiled everything, run <B>make
111 install</B> to install it. By default, the binaries are installed into
112 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
113 modules into <EM>/usr/lib/l2tpns</EM>.<P>
114
115 You will definately need to edit the configuration files before you
116 start. See the <A HREF="#Configuration">Configuration</A> section for
117 more information.<P>
118
119 <H3 ID="Running">Running</H3>
120
121 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it. It does
122 not detach to a daemon process, so you should perhaps run it from init.<P>
123
124 By default there is no log destination set, so all log messages will go to
125 stdout.<P>
126
127 <H2 ID="Configuration">Configuration</H2>
128
129 All configuration of the software is done from the files installed into
130 /etc/l2tpns.
131
132 <H3 ID="startup-config">startup-config</H3>
133
134 This is the main configuration file for l2tpns. The format of the file is a
135 list of commands that can be run through the command-line interface. This
136 file can also be written directly by the l2tpns process if a user runs the
137 <EM>write memory</EM> command, so any comments will be lost. However if your
138 policy is not to write the config by the program, then feel free to comment
139 the file with a # or ! at the beginning of the line.<P>
140
141 A list of the possible configuration directives follows. Each of these
142 should be set by a line like:<P>
143 <PRE>
144 set configstring "value"
145 set ipaddress 192.168.1.1
146 set boolean true
147 </PRE>
148
149 <UL>
150 <LI><B>debug</B> (int)<BR>
151 Sets the level of messages that will be written to the log file. The value
152 should be between 0 and 5, with 0 being no debugging, and 5 being the
153 highest. A rough description of the levels is:
154 <OL>
155 <LI VALUE=0>Critical Errors - Things are probably broken</LI>
156 <LI>Errors - Things might have gone wrong, but probably will recover</LI>
157 <LI>Warnings - Just in case you care what is not quite perfect</LI>
158 <LI>Information - Parameters of control packets</LI>
159 <LI>Calls - For tracing the execution of the code</LI>
160 <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
161 </OL><P>
162 Note that the higher you set the debugging level, the slower the program
163 will run. Also, at level 5 a LOT of information will be logged. This should
164 only ever be used for working out why it doesn't work at all.
165 <P>
166 </LI>
167
168 <LI><B>log_file</B> (string)<BR>
169 This will be where all logging and debugging information is written
170 to. This can be either a filename, such as <EM>/var/log/l2tpns</EM>, or
171 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
172 is any one of the syslog logging facilities, such as local5.
173 <P>
174 </LI>
175
176 <LI><B>pid_file</B> (string)<BR>
177 If this is set, the process id will be written to this file. The filename must
178 contain an absolute path.
179 <P>
180 </LI>
181
182 <LI><B>l2tp_secret</B> (string)<BR>
183 This sets the string that l2tpns will use for authenticating tunnel request.
184 This must be the same as the LAC, or authentication will fail. This will
185 only actually be used if the LAC requests authentication.
186 <P>
187 </LI>
188
189 <LI><B>primary_dns</B> (ip address)
190 <LI><B>secondary_dns</B> (ip address)<BR>
191 Whenever a PPP connection is established, DNS servers will be sent to the
192 user, both a primary and a secondary. If either is set to 0.0.0.0, then that
193 one will not be sent.
194 <P>
195 </LI>
196
197 <LI><B>save_state</B> (boolean)<BR>
198 When l2tpns receives a STGTERM it will write out its current
199 ip_address_pool, session and tunnel tables to disk prior to exiting to
200 be re-loaded at startup. The validity of this data is obviously quite
201 short and the intent is to allow an sessions to be retained over a
202 software upgrade.
203 <P>
204 </LI>
205
206 <LI><B>primary_radius</B> (ip address)
207 <LI><B>secondary_radius</B> (ip address)<BR>
208 This sets the radius servers used for both authentication and
209 accounting. If the primary server does not respond, then the
210 secondary radius server will be tried.
211 <P>
212 </LI>
213
214 <LI><B>primary_radius_port</B> (short)
215 <LI><B>secondary_radius_port</B> (short)<BR>
216 This sets the authentication ports for the primary and secondary
217 radius servers. The accounting port is one more than the authentication
218 port. If no radius ports are given, the authentication port defaults to 1645,
219 and the accounting port to 1646.
220 <P>
221 </LI>
222
223 <LI><B>radius_accounting</B> (boolean)<BR>
224 If set to true, then radius accounting packets will be sent. This
225 means that a Start record will be sent when the session is
226 successfully authenticated, and a Stop record will be sent when the
227 session is closed.
228 <P>
229 </LI>
230
231 <LI><B>radius_secret</B> (string)<BR>
232 This secret will be used in all radius queries. If this is not set then
233 radius queries will fail.
234 <P>
235 </LI>
236
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.
242 <P>
243 </LI>
244
245 <LI><B>send_garp</B> (boolean)<BR>
246 Determines whether or not to send a gratuitous ARP for the
247 bind_address when the server is ready to handle traffic (default:
248 true).<BR>
249 This value is ignored if BGP is configured.
250 <P>
251 </LI>
252
253 <LI><B>throttle_speed</B> (int)<BR>
254 Sets the speed (in kbits/s) which sessions will be limited to. If this is
255 set to 0, then throttling will not be used at all. Note: You can set this by
256 the CLI, but changes will not affect currently connected users.
257 <P>
258 </LI>
259
260 <LI><B>accounting_dir</B> (string)<BR>
261 If set to a directory, then every 5 minutes the current usage for
262 every connected use will be dumped to a file in this directory. Each
263 file dumped begins with a header, where each line is prefixed by #.
264 Following the header is a single line for every connected user, fields
265 separated by a space.<BR> The fields are username, ip, qos,
266 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
267 2 if the user is throttled.
268 <P>
269 </LI>
270
271 <LI><B>setuid</B> (int)<BR>
272 After starting up and binding the interface, change UID to this. This
273 doesn't work properly.
274 <P>
275 </LI>
276
277 <LI><B>dump_speed</B> (boolean)<BR>
278 If set to true, then the current bandwidth utilization will be logged every
279 second. Even if this is disabled, you can see this information by running
280 the <EM>uptime</EM> command on the CLI.
281 <P>
282 </LI>
283
284 <LI><B>cleanup_interval</B> (int)<BR>
285 Interval between regular cleanups (in seconds).
286 <P>
287 </LI>
288
289 <LI><B>multi_read_count</B> (int)<BR>
290 Number of packets to read off each of the UDP and TUN fds when
291 returned as readable by select (default: 10). Avoids incurring the
292 unnecessary system call overhead of select on busy servers.
293 <P>
294 </LI>
295
296 <LI><B>scheduler_fifo</B> (boolean)<BR>
297 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
298 causes the kernel to immediately preempt any currently SCHED_OTHER
299 (normal) process in favour of l2tpns when it becomes runnable.
300 Ignored on uniprocessor systems.
301 <P>
302 </LI>
303
304 <LI><B>lock_pages</B> (boolean)<BR>
305 Keep all pages mapped by the l2tpns process in memory.
306 <P>
307 </LI>
308
309 <LI><B>icmp_rate</B> (int)<BR>
310 Maximum number of host unreachable icmp packets to send per second.
311 <P>
312 </LI>
313
314 <LI><B>cluster_address</B> (ip address)<BR>
315 Multicast cluster address (default: 239.192.13.13). See the section
316 on <A HREF="#Clustering">Clustering</A> for more information.
317 <P>
318 </LI>
319
320 <LI><B>cluster_interface</B> (string)<BR>
321 Interface for cluster packets (default: eth0).
322 <P>
323 </LI>
324
325 <LI><B>cluster_hb_interval</B> (int)<BR>
326 Interval in tenths of a second between cluster heartbeat/pings.
327 <P>
328 </LI>
329
330 <LI><B>cluster_hb_timeout</B> (int)<BR>
331 Cluster heartbeat timeout in tenths of a second. A new master will be
332 elected when this interval has been passed without seeing a heartbeat
333 from the master.
334 <P>
335 </LI>
336
337 <LI><B>as_number</B> (int)<BR>
338 Defines the local AS number for BGP (see <A HREF="#Routing">Routing</A>).
339 <P>
340 </LI>
341
342 <LI><B>bgp_peer1</B> (string)
343 <LI><B>bgp_peer1_as</B> (int)
344 <LI><B>bgp_peer2</B> (string)
345 <LI><B>bgp_peer2_as</B> (int)<BR>
346 <P>
347 DNS name (or IP) and AS number of BGP peers.
348 </LI>
349 </UL>
350
351 <H3 ID="users">users</H3>
352
353 Usernames and passwords for the command-line interface are stored in
354 this file. The format is <I>username</I><B>:</B><I>password</I> where
355 <I>password</I> may either by plain text, an MD5 digest (prefixed by
356 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
357 plain text by the prefix <B>{crypt}</B>.<P>
358
359 The username <B>enable</B> has a special meaning and is used to set
360 the enable password.<P>
361
362 <B>Note:</B> If this file doesn't exist, then anyone who can get to
363 port 23 will be allowed access without a username / password.<P>
364
365 <H3 ID="ip-pool">ip_pool</H3>
366
367 This file is used to configure the IP address pool which user
368 addresses are assigned from. This file should contain either an IP
369 address or a CIDR network per line. e.g.:<P>
370
371 <PRE>
372 192.168.1.1
373 192.168.1.2
374 192.168.1.3
375 192.168.4.0/24
376 172.16.0.0/16
377 10.0.0.0/8
378 </PRE>
379
380 Keep in mind that l2tpns can only handle 65535 connections per
381 process, so don't put more than 65535 IP addresses in the
382 configuration file. They will be wasted.
383
384 <H3 ID="build-garden">build-garden</H3>
385
386 The garden plugin on startup creates a NAT table called "garden" then
387 sources the <B>build-garden</B> script to populate that table. All
388 packets from gardened users will be sent through this table. Example:
389
390 <PRE>
391 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
392 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
393 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
394 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
395 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
396 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
397 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
398 iptables -t nat -A garden -p icmp -j ACCEPT
399 iptables -t nat -A garden -j DROP
400 </PRE>
401
402 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
403
404 A running l2tpns process can be controlled in a number of ways. The primary
405 method of control is by the Command-Line Interface (CLI).<P>
406
407 You can also remotely send commands to modules via the nsctl client
408 provided. This currently only works with the walled garden module, but
409 modification is trivial to support other modules.<P>
410
411 Also, there are a number of signals that l2tpns understands and takes action
412 when it receives them.
413
414 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
415
416 You can access the command line interface by telnet'ing to port 23.
417 There is no IP address restriction, so it's a good idea to firewall
418 this port off from anyone who doesn't need access to it. See
419 <A HREF="#users">users</A> for information on restricting access based
420 on a username and password.<P>
421
422 The CLI gives you real-time control over almost everything in
423 the process. The interface is designed to look like a Cisco
424 device, and supports things like command history, line editing and
425 context sensitive help. This is provided by linking with the
426 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
427 library. Some general documentation of the interface is
428 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
429 here</A>.<P>
430
431 After you have connected to the telnet port (and perhaps logged in), you
432 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
433
434 Enter <EM>help</EM> to get a list of possible commands. A brief
435 overview of the more important commands follows:
436
437 <UL>
438 <LI><B>show session</B><BR>
439 Without specifying a session ID, this will list all tunnels currently
440 connected. If you specify a session ID, you will be given all
441 information on a single tunnel. Note that the full session list can
442 be around 185 columns wide, so you should probably use a wide terminal
443 to see the list properly.<P>
444 The columns listed in the overview are:
445 <TABLE>
446 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
447 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
448 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
449 authentication. If this is *, then LCP authentication has not
450 completed.</TD></TR>
451 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
452 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
453 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
454 session is being snooped. See <EM>snoop</EM>.</TD></TR>
455 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
456 currently throttled. See <EM>throttle</EM>.</TD></TR>
457 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
458 trapped in the walled garden. This field is present even if the
459 garden module is not loaded.</TD></TR>
460 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
461 session started</TD></TR>
462 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
463 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
464 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
465 detected on the session</TD></TR>
466 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
467 connected to.</TD></TR>
468 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
469 provided during the session setup. This field is generated by the
470 LAC.</TD></TR>
471 </TABLE>
472 <P>
473 </LI>
474
475 <LI><B>show users</B><BR>
476 With no arguments, display a list of currently connected users. If an
477 argument is given, the session details for the given username are
478 displayed.
479 </LI>
480
481 <LI><B>show tunnel</B><BR>
482 This will show all the open tunnels in a summary, or detail on a single
483 tunnel if you give a tunnel id.<P>
484 The columns listed in the overview are:
485 <TABLE>
486 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
487 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
488 provided by the LAC. This has no relation to DNS, it is just
489 a text field.</TD></TR>
490 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
491 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
492 Opening</TD></TR>
493 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
494 tunnel</TD></TR>
495 </TABLE>
496 <P>
497 </LI>
498
499 <LI><B>show pool</B><BR>
500 Displays the current IP address pool allocation. This will only display
501 addresses that are in use, or are reserved for re-allocation to a
502 disconnected user.<P>
503 If an address is not currently in use, but has been used, then in the User
504 column the username will be shown in square brackets, followed by the time
505 since the address was used:
506 <PRE>
507 IP Address Used Session User
508 192.168.100.6 N [joe.user] 1548s
509 </PRE>
510 <P>
511 </LI>
512
513 <LI><B>show radius</B><BR>
514 Show a summary of the in-use radius sessions. This list should not be very
515 long, as radius sessions should be cleaned up as soon as they are used. The
516 columns listed are:
517 <TABLE>
518 <TR><TD><B>Radius</B></TD><TD>The ID of the radius request. This is
519 sent in the packet to the radius server for identification.</TD></TR>
520 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
521 AUTH, IPCP, START, STOP, NULL.</TD></TR>
522 <TR><TD><B>Session</B></TD><TD>The session ID that this radius
523 request is associated with</TD></TR>
524 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
525 request, it will retry at this time. This is a unix timestamp.</TD></TR>
526 <TR><TD><B>Try</B></TD><TD>Retry count. The radius request is
527 discarded after 3 retries.</TD></TR>
528 </TABLE>
529 <P>
530 </LI>
531
532 <LI><B>show running-config</B><BR>
533 This will list the current running configuration. This is in a format that
534 can either be pasted into the configuration file, or run directly at the
535 command line.
536 <P>
537 </LI>
538
539 <LI><B>show counters</B><BR>
540 Internally, counters are kept of key values, such as bytes and packets
541 transferred, as well as function call counters. This function displays all
542 these counters, and is probably only useful for debugging.<P>
543 You can reset these counters by running <EM>clear counters</EM>.
544 <P>
545 </LI>
546
547 <LI><B>show cluster</B><BR>
548 Show cluster status. Shows the cluster state for this server
549 (Master/Slave), information about known peers and (for slaves) the
550 master IP address, last packet seen and up-to-date status.<P>
551 See <A HREF="#Clustering">Clustering</A> for more information.
552 <P>
553 </LI>
554
555 <LI><B>write memory</B><BR>
556 This will write the current running configuration to the config file
557 <B>startup-config</B>, which will be run on a restart.
558 <P>
559 </LI>
560
561 <LI><B>snoop</B><BR>
562 You must specify a username, IP address and port. All packets for the
563 current session for that username will be forwarded to the given
564 host/port. Specify <EM>no snoop username</EM> to disable interception
565 for the session.<P>
566
567 If you want interception to be permanent, you will have to modify the radius
568 response for the user. See <A HREF="#Interception">Interception</A>.
569 <P>
570 </LI>
571
572 <LI><B>throttle</B><BR>
573 You must specify a username, which will be throttled for the current
574 session. Specify <EM>no throttle username</EM> to disable throttling
575 for the current session.<P>
576
577 If you want throttling to be permanent, you will have to modify the
578 radius response for the user. See <A HREF="#THrottling">Throttling</A>.
579 <P>
580 </LI>
581
582 <LI><B>drop session</B><BR>
583 This will cleanly disconnect a session. You must specify a session id, which
584 you can get from <EM>show session</EM>. This will send a disconnect message
585 to the remote end.
586 <P>
587 </LI>
588
589 <LI><B>drop tunnel</B><BR>
590 This will cleanly disconnect a tunnel, as well as all sessions on that
591 tunnel. It will send a disconnect message for each session individually, and
592 after 10 seconds it will send a tunnel disconnect message.
593 <P>
594 </LI>
595
596 <LI><B>uptime</B><BR>
597 This will show how long the l2tpns process has been running, and the current
598 bandwidth utilization:
599 <PRE>
600 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
601 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
602 </PRE>
603 The bandwidth line contains 4 sets of values.<BR>
604 UDP-ETH is the current bandwidth going from the LAC to the ethernet
605 (user uploads), in mbits/sec.<BR>
606 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
607 downloads).<BR>
608 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
609 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
610 <P>
611 These counters are updated every second.
612 <P>
613 </LI>
614
615 <LI><B>configure terminal</B><BR>
616 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
617 The following commands are valid in this mode:<P>
618 </LI>
619
620 <LI><B>load plugin</B><BR>
621 Load a plugin. You must specify the plugin name, and it will search in
622 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
623 <EM>remove plugin</EM>.
624 <P>
625 </LI>
626
627 <LI><B>set</B><BR>
628 Set a configuration variable. You must specify the variable name, and
629 the value. If the value contains any spaces, you should quote the
630 value with double (") or single (') quotes.<P>
631
632 You can set any <A HREF="#startup-config">startup-config</A> value in
633 this way, although some may require a restart to take effect.<P>
634 </LI>
635 </UL>
636
637 <H3 ID="nsctl">nsctl</H3>
638
639 nsctl was implemented (badly) to allow messages to be passed to modules.<P>
640
641 You must pass at least 2 parameters: <EM>host</EM> and <EM>command</EM>. The
642 host is the address of the l2tpns server which you want to send the message
643 to.<P>
644
645 Command can currently be either <EM>garden</EM> or <EM>ungarden</EM>. With
646 both of these commands, you must give a session ID as the 3rd parameter.
647 This will activate or deactivate the walled garden for a session
648 temporarily.
649
650 <H3 ID="Signals">Signals</H3>
651
652 While the process is running, you can send it a few different signals, using
653 the kill command.
654 <PRE>
655 killall -HUP l2tpns
656 </PRE>
657
658 The signals understood are:
659 <UL>
660 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
661 <LI>SIGTERM / SIGINT - Shut down for a restart. This will dump the current
662 state to disk (if <EM>save_state</EM> is set to true). Upon restart, the
663 process will read this saved state to resume active sessions.<P>
664 <LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
665 every active session and tunnel before shutting down. This is a good idea
666 when upgrading the code, as no sessions will be left with the remote end
667 thinking they are open.</LI>
668 </UL>
669
670 <H2 ID="Throttling">Throttling</H2>
671
672 l2tpns contains support for slowing down user sessions to whatever speed you
673 desire. You must first enable the global setting <EM>throttle_speed</EM>
674 before this will be activated.<P>
675
676 If you wish a session to be throttled permanently, you should set the
677 Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
678 will be handled by the <EM>autothrottle</EM> module.<P>
679
680 Otherwise, you can enable and disable throttling an active session using
681 the <EM>throttle</EM> CLI command.<P>
682
683 <H2 ID="Interception">Interception</H2>
684
685 You may have to deal with legal requirements to be able to intercept a
686 user's traffic at any time. l2tpns allows you to begin and end interception
687 on the fly, as well as at authentication time.<P>
688
689 When a user is being intercepted, a copy of every packet they send and
690 receive will be sent wrapped in a UDP packet to the IP address and port set
691 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
692 variables.<P>
693
694 The UDP packet contains just the raw IP frame, with no extra headers.<P>
695
696 To enable interception on a connected user, use the <EM>snoop username</EM>
697 and <EM>no snoop username</EM> CLI commands. These will enable interception
698 immediately.<P>
699
700 If you wish the user to be intercepted whenever they reconnect, you will
701 need to modify the radius response to include the Vendor-Specific value
702 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
703 you need to have the <EM>autosnoop</EM> module loaded.<P>
704
705 <H2 ID="Authentication">Authentication</H2>
706
707 Whenever a session connects, it is not fully set up until authentication is
708 completed. The remote end must send a PPP CHAP or PPP PAP authentication
709 request to l2tpns.<P>
710
711 This request is sent to the radius server, which will hopefully respond with
712 Auth-Accept or Auth-Reject.<P>
713
714 If Auth-Accept is received, the session is set up and an IP address is
715 assigned. The radius server can include a Framed-IP-Address field in the
716 reply, and that address will be assigned to the client. It can also include
717 specific DNS servers, and a Framed-Route if that is required.<P>
718
719 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
720 at which point they should disconnect. The exception to this is when the
721 walled garden module is loaded, in which case the user still receives the
722 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
723 should not receive any service.<P>
724
725 The radius reply can also contain a Vendor-Specific attribute called
726 Cisco-Avpair. This field is a freeform text field that most Cisco
727 devices understand to contain configuration instructions for the session. In
728 the case of l2tpns it is expected to be of the form
729 <PRE>
730 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
731 </PRE>
732
733 Each key-value pair is separated and passed to any modules loaded. The
734 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
735 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
736 a user who is to be throttled and intercepted, the Cisco-Avpair value should
737 contain:
738 <PRE>
739 intercept=yes,throttle=yes
740 </PRE>
741
742 <H2 ID="Plugins">Plugins</H2>
743
744 So as to make l2tpns as flexible as possible (I know the core code is pretty
745 difficult to understand), it includes a plugin API, which you can use to
746 hook into certain events.<P>
747
748 There are a few example modules included - autosnoop, autothrottle and
749 garden.<P>
750
751 When an event happens that has a hook, l2tpns looks for a predefined
752 function name in every loaded module, and runs them in the order the modules
753 were loaded.<P>
754
755 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
756 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
757 modules should be run for this event.<P>
758 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
759 no further processing should be done for this event. <EM>Use this with care.</EM>
760
761 Every event function called takes a specific structure named
762 param_<EM>event</EM>, which varies in content with each event. The
763 function name for each event will be <B>plugin_<EM>event</EM></B>,
764 so for the event <EM>timer</EM>, the function declaration should look like:
765 <PRE>
766 int plugin_timer(struct param_timer *data);
767 </PRE>
768
769 A list of the available events follows, with a list of all the fields in the
770 supplied structure:
771 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
772 <TABLE CELLSPACING=1 CELLPADDING=3>
773 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
774 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
775 <TD>This is called after a radius response has been
776 received, but before it has been processed by the
777 code. This will allow you to modify the response in
778 some way.
779 </TD>
780 <TD>
781 <UL>
782 <LI>t - Tunnel ID</LI>
783 <LI>s - Session ID</LI>
784 <LI>username</LI>
785 <LI>password</LI>
786 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
787 <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
788 </UL>
789 </TD>
790 </TR>
791 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
792 <TD>This is called after a radius response has been
793 received, and the basic checks have been performed. This
794 is what the garden module uses to force authentication
795 to be accepted.
796 </TD>
797 <TD>
798 <UL>
799 <LI>t - Tunnel ID</LI>
800 <LI>s - Session ID</LI>
801 <LI>username</LI>
802 <LI>auth_allowed - This is already set to true or
803 false depending on whether authentication has been
804 allowed so far. You can set this to 1 or 0 to force
805 allow or disallow authentication</LI>
806 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
807 </UL>
808 </TD>
809 </TR>
810 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
811 <TD>This is called whenever a session receives a
812 packet. <FONT COLOR=RED>Use this sparingly, as this will
813 seriously slow down the system.</FONT>
814 </TD>
815 <TD>
816 <UL>
817 <LI>t - Tunnel ID</LI>
818 <LI>s - Session ID</LI>
819 <LI>buf - The raw packet data</LI>
820 <LI>len - The length of buf</LI>
821 </UL>
822 </TD>
823 </TR>
824 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
825 <TD>This is called whenever a session sends a
826 packet. <FONT COLOR=RED>Use this sparingly, as this will
827 seriously slow down the system.</FONT>
828 </TD>
829 <TD>
830 <UL>
831 <LI>t - Tunnel ID</LI>
832 <LI>s - Session ID</LI>
833 <LI>buf - The raw packet data</LI>
834 <LI>len - The length of buf</LI>
835 </UL>
836 </TD>
837 </TR>
838 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
839 <TD>This is run every second, no matter what is happening.
840 This is called from a signal handler, so make sure anything
841 you do is reentrant.
842 </TD>
843 <TD>
844 <UL>
845 <LI>time_now - The current unix timestamp</LI>
846 </UL>
847 </TD>
848 </TR>
849 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
850 <TD>This is called after a session is fully set up. The
851 session is now ready to handle traffic.
852 </TD>
853 <TD>
854 <UL>
855 <LI>t - Tunnel ID</LI>
856 <LI>s - Session ID</LI>
857 </UL>
858 </TD>
859 </TR>
860 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
861 <TD>This is called when a session is about to be shut down.
862 This may be called multiple times for the same session.
863 </TD>
864 <TD>
865 <UL>
866 <LI>t - Tunnel ID</LI>
867 <LI>s - Session ID</LI>
868 </UL>
869 </TD>
870 </TR>
871 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
872 <TD>This is called whenever a radius response includes a
873 Cisco-Avpair value. The value is split up into
874 <EM>key=value</EM> pairs, and each is processed through all
875 modules.
876 </TD>
877 <TD>
878 <UL>
879 <LI>t - Tunnel ID</LI>
880 <LI>s - Session ID</LI>
881 <LI>key</LI>
882 <LI>value</LI>
883 </UL>
884 </TD>
885 </TR>
886 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
887 <TD>This is called in whenever a nsctl packet is received.
888 This should handle the packet and form a response if
889 required.
890 </TD>
891 <TD>
892 <UL>
893 <LI>buf - The raw packet data</LI>
894 <LI>l - The raw packet data length</LI>
895 <LI>source_ip - Where the request came from</LI>
896 <LI>source_port - Where the request came from</LI>
897 <LI>response - Allocate a buffer and put your response in here</LI>
898 <LI>response_length - Length of response</LI>
899 <LI>send_response - true or false whether a response
900 should be sent. If you set this to true, you must
901 allocate a response buffer.</LI>
902 <LI>type - Type of request (see nsctl.c)</LI>
903 <LI>id - ID of request</LI>
904 <LI>data - I'm really not sure</LI>
905 <LI>data_length - Length of data</LI>
906 </UL>
907 </TD>
908 </TR>
909 </TABLE>
910 </TD></TR></TABLE>
911
912 <H2 ID="WalledGarden">Walled Garden</H2>
913
914 Walled Garden is implemented so that you can provide perhaps limited service
915 to sessions that incorrectly authenticate.<P>
916
917 Whenever a session provides incorrect authentication, and the
918 radius server responds with Auth-Reject, the walled garden module
919 (if loaded) will force authentication to succeed, but set the flag
920 <EM>garden</EM> in the session structure, and adds an iptables rule to
921 the <B>garden_users</B> chain to force all packets for the session's IP
922 address to traverse the <B>garden</B> chain.<P>
923
924 This doesn't <EM>just work</EM>. To set this all up, you will to
925 setup the <B>garden</B> nat table with the
926 <A HREF="#build-garden">build-garden</A> script with rules to limit
927 user's traffic. For example, to force all traffic except DNS to be
928 forwarded to 192.168.1.1, add these entries to your
929 <EM>build-garden</EM>:
930 <PRE>
931 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
932 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
933 </PRE>
934
935 l2tpns will add entries to the garden_users chain as appropriate.<P>
936
937 You can check the amount of traffic being captured using the following
938 command:
939 <PRE>
940 iptables -t nat -L garden -nvx
941 </PRE>
942
943 <H2 ID="Clustering">Clustering</H2>
944
945 An l2tpns cluster consists of of one* or more servers configured with
946 the same configuration, notably the multicast <B>cluster_address</B>.<P>
947
948 *A stand-alone server is simply a degraded cluster.<P>
949
950 Initially servers come up as cluster slaves, and periodically (every
951 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
952 containing the start time of the process to the multicast
953 <B>cluster_address</B>.<P>
954
955 A cluster master sends heartbeat rather than ping packets, which
956 contain those session and tunnel changes since the last heartbeat.<P>
957
958 When a slave has not seen a heartbeat within
959 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
960 examining the list of peers it has seen pings from and determines
961 which of these and itself is the "best" candidate to be master.
962 "Best" in this context means the server with the highest uptime (the
963 highest IP address is used as a tie-breaker in the case of equal
964 uptimes).<P>
965
966 After discovering a master, and determining that it is up-to-date (has
967 seen an update for all in-use sessions and tunnels from heartbeat
968 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
969 the <B>bind_address</B> and for all addresses/networks in
970 <B>ip_pool</B>. Any packets recieved by the slave which would alter
971 the session state, as well as packets for throttled or gardened
972 sessions are forwarded to the master for handling. In addition, byte
973 counters for session traffic are periodically forwarded.<P>
974
975 A master, when determining that it has at least one up-to-date slave
976 will drop all routes (raising them again if all slaves disappear) and
977 subsequently handle only packets forwarded to it by the slaves.<P>
978
979 <H2 ID="Routing">Routing</H2>
980 If you are running a single instance, you may simply statically route
981 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
982 arp).<P>
983
984 For a cluster, configure the members as BGP neighbours on your router
985 and configure multi-path load-balancing. Cisco uses "maximum-paths
986 ibgp" for IBGP. If this is not supported by your IOS revision, you
987 can use "maximum-paths" (which works for EBGP) and set
988 <B>as_number</B> to a private value such as 64512.<P>
989
990 <H2 ID="Performance">Performance</H2>
991
992 Performance is great.<P>
993
994 I'd like to include some pretty graphs here that show a linear performance
995 increase, with no impact by number of connected sessions.<P>
996
997 That's really what it looks like.<P>
998
999 <BR>
1000 David Parrish<BR>
1001 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1002 </BODY>
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