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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 <P>
150 <UL>
151 <LI><B>debug</B> (int)<BR>
152 Sets the level of messages that will be written to the log file. The value
153 should be between 0 and 5, with 0 being no debugging, and 5 being the
154 highest. A rough description of the levels is:
155 <OL>
156 <LI VALUE=0>Critical Errors - Things are probably broken</LI>
157 <LI>Errors - Things might have gone wrong, but probably will recover</LI>
158 <LI>Warnings - Just in case you care what is not quite perfect</LI>
159 <LI>Information - Parameters of control packets</LI>
160 <LI>Calls - For tracing the execution of the code</LI>
161 <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
162 </OL><P>
163 Note that the higher you set the debugging level, the slower the program
164 will run. Also, at level 5 a LOT of information will be logged. This should
165 only ever be used for working out why it doesn't work at all.
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 may 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 </LI>
174
175 <LI><B>pid_file</B> (string)<BR>
176 If set, the process id will be written to the specified file. The
177 value must be an absolute path.
178 </LI>
179
180 <LI><B>l2tp_secret</B> (string)<BR>
181 The secret used by l2tpns for authenticating tunnel request. Must be
182 the same as the LAC, or authentication will fail. Only actually be
183 used if the LAC requests authentication.
184 </LI>
185
186 <LI><B>primary_dns</B> (ip address)
187 <LI><B>secondary_dns</B> (ip address)<BR>
188 Whenever a PPP connection is established, DNS servers will be sent to the
189 user, both a primary and a secondary. If either is set to 0.0.0.0, then that
190 one will not be sent.
191 </LI>
192
193 <LI><B>save_state</B> (boolean)<BR>
194 When l2tpns receives a STGTERM it will write out its current
195 ip_address_pool, session and tunnel tables to disk prior to exiting to
196 be re-loaded at startup. The validity of this data is obviously quite
197 short and the intent is to allow an sessions to be retained over a
198 software upgrade.
199 </LI>
200
201 <LI><B>primary_radius</B> (ip address)
202 <LI><B>secondary_radius</B> (ip address)<BR>
203 Sets the radius servers used for both authentication and accounting.
204 If the primary server does not respond, then the secondary radius
205 server will be tried.
206 </LI>
207
208 <LI><B>primary_radius_port</B> (short)
209 <LI><B>secondary_radius_port</B> (short)<BR>
210 Sets the authentication ports for the primary and secondary radius
211 servers. The accounting port is one more than the authentication
212 port. If no radius ports are given, the authentication port defaults
213 to 1645, and the accounting port to 1646.
214 </LI>
215
216 <LI><B>radius_accounting</B> (boolean)<BR>
217 If set to true, then radius accounting packets will be sent. This
218 means that a Start record will be sent when the session is
219 successfully authenticated, and a Stop record will be sent when the
220 session is closed.
221 </LI>
222
223 <LI><B>radius_secret</B> (string)<BR>
224 This secret will be used in all radius queries. If this is not set then
225 radius queries will fail.
226 </LI>
227
228 <LI><B>bind_address</B> (ip address)<BR>
229 When the tun interface is created, it is assigned the address
230 specified here. If no address is given, 1.1.1.1 is used. Packets
231 containing user traffic should be routed via this address if given,
232 otherwise the primary address of the machine.
233 </LI>
234
235 <LI><B>peer_address</B> (ip address)<BR>
236 Address to send to clients as the default gateway.
237 </L1>
238
239 <LI><B>send_garp</B> (boolean)<BR>
240 Determines whether or not to send a gratuitous ARP for the
241 bind_address when the server is ready to handle traffic (default:
242 true).<BR>
243 This value is ignored if BGP is configured.
244 </LI>
245
246 <LI><B>throttle_speed</B> (int)<BR>
247 Sets the default speed (in kbits/s) which sessions will be limited to.
248 If this is set to 0, then throttling will not be used at all. Note:
249 You can set this by the CLI, but changes will not affect currently
250 connected users.
251 </LI>
252
253 <LI><B>throttle_buckets</B> (int)<BR>
254 Number of token buckets to allocate for throttling. Each throttled
255 session requires two buckets (in and out).
256 </LI>
257
258 <LI><B>accounting_dir</B> (string)<BR>
259 If set to a directory, then every 5 minutes the current usage for
260 every connected use will be dumped to a file in this directory. Each
261 file dumped begins with a header, where each line is prefixed by #.
262 Following the header is a single line for every connected user, fields
263 separated by a space.<BR> The fields are username, ip, qos,
264 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
265 2 if the user is throttled.
266 </LI>
267
268 <LI><B>setuid</B> (int)<BR>
269 After starting up and binding the interface, change UID to this. This
270 doesn't work properly.
271 </LI>
272
273 <LI><B>dump_speed</B> (boolean)<BR>
274 If set to true, then the current bandwidth utilization will be logged every
275 second. Even if this is disabled, you can see this information by running
276 the <EM>uptime</EM> command on the CLI.
277 </LI>
278
279 <LI><B>cleanup_interval</B> (int)<BR>
280 Interval between regular cleanups (in seconds).
281 </LI>
282
283 <LI><B>multi_read_count</B> (int)<BR>
284 Number of packets to read off each of the UDP and TUN fds when
285 returned as readable by select (default: 10). Avoids incurring the
286 unnecessary system call overhead of select on busy servers.
287 </LI>
288
289 <LI><B>scheduler_fifo</B> (boolean)<BR>
290 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
291 causes the kernel to immediately preempt any currently running SCHED_OTHER
292 (normal) process in favour of l2tpns when it becomes runnable.
293 Ignored on uniprocessor systems.
294 </LI>
295
296 <LI><B>lock_pages</B> (boolean)<BR>
297 Keep all pages mapped by the l2tpns process in memory.
298 </LI>
299
300 <LI><B>icmp_rate</B> (int)<BR>
301 Maximum number of host unreachable ICMP packets to send per second.
302 </LI>
303
304 <LI><B>cluster_address</B> (ip address)<BR>
305 Multicast cluster address (default: 239.192.13.13). See the section
306 on <A HREF="#Clustering">Clustering</A> for more information.
307 </LI>
308
309 <LI><B>cluster_interface</B> (string)<BR>
310 Interface for cluster packets (default: eth0).
311 </LI>
312
313 <LI><B>cluster_hb_interval</B> (int)<BR>
314 Interval in tenths of a second between cluster heartbeat/pings.
315 </LI>
316
317 <LI><B>cluster_hb_timeout</B> (int)<BR>
318 Cluster heartbeat timeout in tenths of a second. A new master will be
319 elected when this interval has been passed without seeing a heartbeat
320 from the master.
321 </LI>
322 </UL>
323
324 <P>BGP routing configuration is entered by the command:
325 The routing configuration section is entered by the command
326 <DL><DD><B>router bgp</B> <I>as</I></DL>
327 where <I>as</I> specifies the local AS number.
328
329 <P>Subsequent lines prefixed with
330 <DL><DD><B>neighbour</B> <I>peer</I></DL>
331 define the attributes of BGP neighhbours. Valid commands are:
332 <DL>
333 <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
334 <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
335 </DL>
336
337 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
338 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
339 <I>hold</I> are the timer values in seconds.
340
341 <H3 ID="users">users</H3>
342
343 Usernames and passwords for the command-line interface are stored in
344 this file. The format is <I>username</I><B>:</B><I>password</I> where
345 <I>password</I> may either by plain text, an MD5 digest (prefixed by
346 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
347 plain text by the prefix <B>{crypt}</B>.<P>
348
349 The username <B>enable</B> has a special meaning and is used to set
350 the enable password.<P>
351
352 <B>Note:</B> If this file doesn't exist, then anyone who can get to
353 port 23 will be allowed access without a username / password.<P>
354
355 <H3 ID="ip-pool">ip_pool</H3>
356
357 This file is used to configure the IP address pool which user
358 addresses are assigned from. This file should contain either an IP
359 address or a CIDR network per line. e.g.:<P>
360
361 <PRE>
362 192.168.1.1
363 192.168.1.2
364 192.168.1.3
365 192.168.4.0/24
366 172.16.0.0/16
367 10.0.0.0/8
368 </PRE>
369
370 Keep in mind that l2tpns can only handle 65535 connections per
371 process, so don't put more than 65535 IP addresses in the
372 configuration file. They will be wasted.
373
374 <H3 ID="build-garden">build-garden</H3>
375
376 The garden plugin on startup creates a NAT table called "garden" then
377 sources the <B>build-garden</B> script to populate that table. All
378 packets from gardened users will be sent through this table. Example:
379
380 <PRE>
381 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
382 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
383 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
384 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
385 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
386 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
387 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
388 iptables -t nat -A garden -p icmp -j ACCEPT
389 iptables -t nat -A garden -j DROP
390 </PRE>
391
392 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
393
394 A running l2tpns process can be controlled in a number of ways. The primary
395 method of control is by the Command-Line Interface (CLI).<P>
396
397 You can also remotely send commands to modules via the nsctl client
398 provided.<P>
399
400 Also, there are a number of signals that l2tpns understands and takes action
401 when it receives them.
402
403 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
404
405 You can access the command line interface by telnet'ing to port 23.
406 There is no IP address restriction, so it's a good idea to firewall
407 this port off from anyone who doesn't need access to it. See
408 <A HREF="#users">users</A> for information on restricting access based
409 on a username and password.<P>
410
411 The CLI gives you real-time control over almost everything in
412 the process. The interface is designed to look like a Cisco
413 device, and supports things like command history, line editing and
414 context sensitive help. This is provided by linking with the
415 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
416 library. Some general documentation of the interface is
417 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
418 here</A>.<P>
419
420 After you have connected to the telnet port (and perhaps logged in), you
421 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
422
423 Enter <EM>help</EM> to get a list of possible commands. A brief
424 overview of the more important commands follows:
425
426 <UL>
427 <LI><B>show session</B><BR>
428 Without specifying a session ID, this will list all tunnels currently
429 connected. If you specify a session ID, you will be given all
430 information on a single tunnel. Note that the full session list can
431 be around 185 columns wide, so you should probably use a wide terminal
432 to see the list properly.<P>
433 The columns listed in the overview are:
434 <TABLE>
435 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
436 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
437 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
438 authentication. If this is *, then LCP authentication has not
439 completed.</TD></TR>
440 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
441 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
442 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
443 session is being snooped. See <EM>snoop</EM>.</TD></TR>
444 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
445 currently throttled. See <EM>throttle</EM>.</TD></TR>
446 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
447 trapped in the walled garden. This field is present even if the
448 garden module is not loaded.</TD></TR>
449 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
450 session started</TD></TR>
451 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
452 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
453 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
454 detected on the session</TD></TR>
455 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
456 connected to.</TD></TR>
457 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
458 provided during the session setup. This field is generated by the
459 LAC.</TD></TR>
460 </TABLE>
461 <P>
462 </LI>
463
464 <LI><B>show users</B><BR>
465 With no arguments, display a list of currently connected users. If an
466 argument is given, the session details for the given username are
467 displayed.
468 </LI>
469
470 <LI><B>show tunnel</B><BR>
471 This will show all the open tunnels in a summary, or detail on a single
472 tunnel if you give a tunnel id.<P>
473 The columns listed in the overview are:
474 <TABLE>
475 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
476 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
477 provided by the LAC. This has no relation to DNS, it is just
478 a text field.</TD></TR>
479 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
480 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
481 Opening</TD></TR>
482 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
483 tunnel</TD></TR>
484 </TABLE>
485 <P>
486 </LI>
487
488 <LI><B>show pool</B><BR>
489 Displays the current IP address pool allocation. This will only display
490 addresses that are in use, or are reserved for re-allocation to a
491 disconnected user.<P>
492 If an address is not currently in use, but has been used, then in the User
493 column the username will be shown in square brackets, followed by the time
494 since the address was used:
495 <PRE>
496 IP Address Used Session User
497 192.168.100.6 N [joe.user] 1548s
498 </PRE>
499 <P>
500 </LI>
501
502 <LI><B>show radius</B><BR>
503 Show a summary of the in-use radius sessions. This list should not be very
504 long, as radius sessions should be cleaned up as soon as they are used. The
505 columns listed are:
506 <TABLE>
507 <TR><TD><B>Radius</B></TD><TD>The ID of the radius request. This is
508 sent in the packet to the radius server for identification.</TD></TR>
509 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
510 AUTH, IPCP, START, STOP, NULL.</TD></TR>
511 <TR><TD><B>Session</B></TD><TD>The session ID that this radius
512 request is associated with</TD></TR>
513 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
514 request, it will retry at this time. This is a unix timestamp.</TD></TR>
515 <TR><TD><B>Try</B></TD><TD>Retry count. The radius request is
516 discarded after 3 retries.</TD></TR>
517 </TABLE>
518 <P>
519 </LI>
520
521 <LI><B>show running-config</B><BR>
522 This will list the current running configuration. This is in a format that
523 can either be pasted into the configuration file, or run directly at the
524 command line.
525 <P>
526 </LI>
527
528 <LI><B>show counters</B><BR>
529 Internally, counters are kept of key values, such as bytes and packets
530 transferred, as well as function call counters. This function displays all
531 these counters, and is probably only useful for debugging.<P>
532 You can reset these counters by running <EM>clear counters</EM>.
533 <P>
534 </LI>
535
536 <LI><B>show cluster</B><BR>
537 Show cluster status. Shows the cluster state for this server
538 (Master/Slave), information about known peers and (for slaves) the
539 master IP address, last packet seen and up-to-date status.<P>
540 See <A HREF="#Clustering">Clustering</A> for more information.
541 <P>
542 </LI>
543
544 <LI><B>write memory</B><BR>
545 This will write the current running configuration to the config file
546 <B>startup-config</B>, which will be run on a restart.
547 <P>
548 </LI>
549
550 <LI><B>snoop</B><BR>
551 You must specify a username, IP address and port. All packets for the
552 current session for that username will be forwarded to the given
553 host/port. Specify <EM>no snoop username</EM> to disable interception
554 for the session.<P>
555
556 If you want interception to be permanent, you will have to modify the radius
557 response for the user. See <A HREF="#Interception">Interception</A>.
558 <P>
559 </LI>
560
561 <LI><B>throttle</B><BR>
562 You must specify a username, which will be throttled for the current
563 session. Specify <EM>no throttle username</EM> to disable throttling
564 for the current session.<P>
565
566 If you want throttling to be permanent, you will have to modify the
567 radius response for the user. See <A HREF="#THrottling">Throttling</A>.
568 <P>
569 </LI>
570
571 <LI><B>drop session</B><BR>
572 This will cleanly disconnect a session. You must specify a session id, which
573 you can get from <EM>show session</EM>. This will send a disconnect message
574 to the remote end.
575 <P>
576 </LI>
577
578 <LI><B>drop tunnel</B><BR>
579 This will cleanly disconnect a tunnel, as well as all sessions on that
580 tunnel. It will send a disconnect message for each session individually, and
581 after 10 seconds it will send a tunnel disconnect message.
582 <P>
583 </LI>
584
585 <LI><B>uptime</B><BR>
586 This will show how long the l2tpns process has been running, and the current
587 bandwidth utilization:
588 <PRE>
589 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
590 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
591 </PRE>
592 The bandwidth line contains 4 sets of values.<BR>
593 UDP-ETH is the current bandwidth going from the LAC to the ethernet
594 (user uploads), in mbits/sec.<BR>
595 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
596 downloads).<BR>
597 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
598 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
599 <P>
600 These counters are updated every second.
601 <P>
602 </LI>
603
604 <LI><B>configure terminal</B><BR>
605 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
606 The following commands are valid in this mode:<P>
607 </LI>
608
609 <LI><B>load plugin</B><BR>
610 Load a plugin. You must specify the plugin name, and it will search in
611 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
612 <EM>remove plugin</EM>.
613 <P>
614 </LI>
615
616 <LI><B>set</B><BR>
617 Set a configuration variable. You must specify the variable name, and
618 the value. If the value contains any spaces, you should quote the
619 value with double (") or single (') quotes.<P>
620
621 You can set any <A HREF="#startup-config">startup-config</A> value in
622 this way, although some may require a restart to take effect.<P>
623 </LI>
624 </UL>
625
626 <H3 ID="nsctl">nsctl</H3>
627
628 nsctl allows messages to be passed to plugins.<P>
629
630 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
631 <STRONG>nsctl</STRONG>(8) for more details.<P>
632
633 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
634 <EM>help</EM>. Any other commands are passed to plugins for processing.
635
636 <H3 ID="Signals">Signals</H3>
637
638 While the process is running, you can send it a few different signals, using
639 the kill command.
640 <PRE>
641 killall -HUP l2tpns
642 </PRE>
643
644 The signals understood are:
645 <UL>
646 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
647 <LI>SIGTERM / SIGINT - Shut down for a restart. This will dump the current
648 state to disk (if <EM>save_state</EM> is set to true). Upon restart, the
649 process will read this saved state to resume active sessions.<P>
650 <LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
651 every active session and tunnel before shutting down. This is a good idea
652 when upgrading the code, as no sessions will be left with the remote end
653 thinking they are open.</LI>
654 </UL>
655
656 <H2 ID="Throttling">Throttling</H2>
657
658 l2tpns contains support for slowing down user sessions to whatever speed you
659 desire. You must first enable the global setting <EM>throttle_speed</EM>
660 before this will be activated.<P>
661
662 If you wish a session to be throttled permanently, you should set the
663 Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
664 will be handled by the <EM>autothrottle</EM> module.<P>
665
666 Otherwise, you can enable and disable throttling an active session using
667 the <EM>throttle</EM> CLI command.<P>
668
669 <H2 ID="Interception">Interception</H2>
670
671 You may have to deal with legal requirements to be able to intercept a
672 user's traffic at any time. l2tpns allows you to begin and end interception
673 on the fly, as well as at authentication time.<P>
674
675 When a user is being intercepted, a copy of every packet they send and
676 receive will be sent wrapped in a UDP packet to the IP address and port set
677 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
678 variables.<P>
679
680 The UDP packet contains just the raw IP frame, with no extra headers.<P>
681
682 To enable interception on a connected user, use the <EM>snoop username</EM>
683 and <EM>no snoop username</EM> CLI commands. These will enable interception
684 immediately.<P>
685
686 If you wish the user to be intercepted whenever they reconnect, you will
687 need to modify the radius response to include the Vendor-Specific value
688 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
689 you need to have the <EM>autosnoop</EM> module loaded.<P>
690
691 <H2 ID="Authentication">Authentication</H2>
692
693 Whenever a session connects, it is not fully set up until authentication is
694 completed. The remote end must send a PPP CHAP or PPP PAP authentication
695 request to l2tpns.<P>
696
697 This request is sent to the radius server, which will hopefully respond with
698 Auth-Accept or Auth-Reject.<P>
699
700 If Auth-Accept is received, the session is set up and an IP address is
701 assigned. The radius server can include a Framed-IP-Address field in the
702 reply, and that address will be assigned to the client. It can also include
703 specific DNS servers, and a Framed-Route if that is required.<P>
704
705 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
706 at which point they should disconnect. The exception to this is when the
707 walled garden module is loaded, in which case the user still receives the
708 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
709 should not receive any service.<P>
710
711 The radius reply can also contain a Vendor-Specific attribute called
712 Cisco-Avpair. This field is a freeform text field that most Cisco
713 devices understand to contain configuration instructions for the session. In
714 the case of l2tpns it is expected to be of the form
715 <PRE>
716 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
717 </PRE>
718
719 Each key-value pair is separated and passed to any modules loaded. The
720 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
721 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
722 a user who is to be throttled and intercepted, the Cisco-Avpair value should
723 contain:
724 <PRE>
725 intercept=yes,throttle=yes
726 </PRE>
727
728 <H2 ID="Plugins">Plugins</H2>
729
730 So as to make l2tpns as flexible as possible (I know the core code is pretty
731 difficult to understand), it includes a plugin API, which you can use to
732 hook into certain events.<P>
733
734 There are a few example modules included - autosnoop, autothrottle and
735 garden.<P>
736
737 When an event happens that has a hook, l2tpns looks for a predefined
738 function name in every loaded module, and runs them in the order the modules
739 were loaded.<P>
740
741 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
742 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
743 modules should be run for this event.<P>
744 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
745 no further processing should be done for this event. <EM>Use this with care.</EM>
746
747 Every event function called takes a specific structure named
748 param_<EM>event</EM>, which varies in content with each event. The
749 function name for each event will be <B>plugin_<EM>event</EM></B>,
750 so for the event <EM>timer</EM>, the function declaration should look like:
751 <PRE>
752 int plugin_timer(struct param_timer *data);
753 </PRE>
754
755 A list of the available events follows, with a list of all the fields in the
756 supplied structure:
757 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
758 <TABLE CELLSPACING=1 CELLPADDING=3>
759 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
760 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
761 <TD>This is called after a radius response has been
762 received, but before it has been processed by the
763 code. This will allow you to modify the response in
764 some way.
765 </TD>
766 <TD>
767 <UL>
768 <LI>t - Tunnel ID</LI>
769 <LI>s - Session ID</LI>
770 <LI>username</LI>
771 <LI>password</LI>
772 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
773 <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
774 </UL>
775 </TD>
776 </TR>
777 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
778 <TD>This is called after a radius response has been
779 received, and the basic checks have been performed. This
780 is what the garden module uses to force authentication
781 to be accepted.
782 </TD>
783 <TD>
784 <UL>
785 <LI>t - Tunnel ID</LI>
786 <LI>s - Session ID</LI>
787 <LI>username</LI>
788 <LI>auth_allowed - This is already set to true or
789 false depending on whether authentication has been
790 allowed so far. You can set this to 1 or 0 to force
791 allow or disallow authentication</LI>
792 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
793 </UL>
794 </TD>
795 </TR>
796 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
797 <TD>This is called whenever a session receives a
798 packet. <FONT COLOR=RED>Use this sparingly, as this will
799 seriously slow down the system.</FONT>
800 </TD>
801 <TD>
802 <UL>
803 <LI>t - Tunnel ID</LI>
804 <LI>s - Session ID</LI>
805 <LI>buf - The raw packet data</LI>
806 <LI>len - The length of buf</LI>
807 </UL>
808 </TD>
809 </TR>
810 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
811 <TD>This is called whenever a session sends 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>timer</B></TD>
825 <TD>This is run every second, no matter what is happening.
826 This is called from a signal handler, so make sure anything
827 you do is reentrant.
828 </TD>
829 <TD>
830 <UL>
831 <LI>time_now - The current unix timestamp</LI>
832 </UL>
833 </TD>
834 </TR>
835 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
836 <TD>This is called after a session is fully set up. The
837 session is now ready to handle traffic.
838 </TD>
839 <TD>
840 <UL>
841 <LI>t - Tunnel ID</LI>
842 <LI>s - Session ID</LI>
843 </UL>
844 </TD>
845 </TR>
846 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
847 <TD>This is called when a session is about to be shut down.
848 This may be called multiple times for the same session.
849 </TD>
850 <TD>
851 <UL>
852 <LI>t - Tunnel ID</LI>
853 <LI>s - Session ID</LI>
854 </UL>
855 </TD>
856 </TR>
857 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
858 <TD>This is called whenever a radius response includes a
859 Cisco-Avpair value. The value is split up into
860 <EM>key=value</EM> pairs, and each is processed through all
861 modules.
862 </TD>
863 <TD>
864 <UL>
865 <LI>t - Tunnel ID</LI>
866 <LI>s - Session ID</LI>
867 <LI>key</LI>
868 <LI>value</LI>
869 </UL>
870 </TD>
871 </TR>
872 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
873 <TD>This is called in whenever a nsctl packet is received.
874 This should handle the packet and form a response if
875 required.
876 </TD>
877 <TD>
878 <UL>
879 <LI>buf - The raw packet data</LI>
880 <LI>l - The raw packet data length</LI>
881 <LI>source_ip - Where the request came from</LI>
882 <LI>source_port - Where the request came from</LI>
883 <LI>response - Allocate a buffer and put your response in here</LI>
884 <LI>response_length - Length of response</LI>
885 <LI>send_response - true or false whether a response
886 should be sent. If you set this to true, you must
887 allocate a response buffer.</LI>
888 <LI>type - Type of request (see nsctl.c)</LI>
889 <LI>id - ID of request</LI>
890 <LI>data - I'm really not sure</LI>
891 <LI>data_length - Length of data</LI>
892 </UL>
893 </TD>
894 </TR>
895 </TABLE>
896 </TD></TR></TABLE>
897
898 <H2 ID="WalledGarden">Walled Garden</H2>
899
900 Walled Garden is implemented so that you can provide perhaps limited service
901 to sessions that incorrectly authenticate.<P>
902
903 Whenever a session provides incorrect authentication, and the
904 radius server responds with Auth-Reject, the walled garden module
905 (if loaded) will force authentication to succeed, but set the flag
906 <EM>garden</EM> in the session structure, and adds an iptables rule to
907 the <B>garden_users</B> chain to force all packets for the session's IP
908 address to traverse the <B>garden</B> chain.<P>
909
910 This doesn't <EM>just work</EM>. To set this all up, you will to
911 setup the <B>garden</B> nat table with the
912 <A HREF="#build-garden">build-garden</A> script with rules to limit
913 user's traffic. For example, to force all traffic except DNS to be
914 forwarded to 192.168.1.1, add these entries to your
915 <EM>build-garden</EM>:
916 <PRE>
917 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
918 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
919 </PRE>
920
921 l2tpns will add entries to the garden_users chain as appropriate.<P>
922
923 You can check the amount of traffic being captured using the following
924 command:
925 <PRE>
926 iptables -t nat -L garden -nvx
927 </PRE>
928
929 <H2 ID="Clustering">Clustering</H2>
930
931 An l2tpns cluster consists of of one* or more servers configured with
932 the same configuration, notably the multicast <B>cluster_address</B>.<P>
933
934 *A stand-alone server is simply a degraded cluster.<P>
935
936 Initially servers come up as cluster slaves, and periodically (every
937 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
938 containing the start time of the process to the multicast
939 <B>cluster_address</B>.<P>
940
941 A cluster master sends heartbeat rather than ping packets, which
942 contain those session and tunnel changes since the last heartbeat.<P>
943
944 When a slave has not seen a heartbeat within
945 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
946 examining the list of peers it has seen pings from and determines
947 which of these and itself is the "best" candidate to be master.
948 "Best" in this context means the server with the highest uptime (the
949 highest IP address is used as a tie-breaker in the case of equal
950 uptimes).<P>
951
952 After discovering a master, and determining that it is up-to-date (has
953 seen an update for all in-use sessions and tunnels from heartbeat
954 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
955 the <B>bind_address</B> and for all addresses/networks in
956 <B>ip_pool</B>. Any packets recieved by the slave which would alter
957 the session state, as well as packets for throttled or gardened
958 sessions are forwarded to the master for handling. In addition, byte
959 counters for session traffic are periodically forwarded.<P>
960
961 A master, when determining that it has at least one up-to-date slave
962 will drop all routes (raising them again if all slaves disappear) and
963 subsequently handle only packets forwarded to it by the slaves.<P>
964
965 <H2 ID="Routing">Routing</H2>
966 If you are running a single instance, you may simply statically route
967 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
968 arp).<P>
969
970 For a cluster, configure the members as BGP neighbours on your router
971 and configure multi-path load-balancing. Cisco uses "maximum-paths
972 ibgp" for IBGP. If this is not supported by your IOS revision, you
973 can use "maximum-paths" (which works for EBGP) and set
974 <B>as_number</B> to a private value such as 64512.<P>
975
976 <H2 ID="Performance">Performance</H2>
977
978 Performance is great.<P>
979
980 I'd like to include some pretty graphs here that show a linear performance
981 increase, with no impact by number of connected sessions.<P>
982
983 That's really what it looks like.<P>
984
985 <BR>
986 David Parrish<BR>
987 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
988 </BODY>
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