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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>primary_dns</B> (ip address)
188 <LI><B>secondary_dns</B> (ip address)<BR>
189 Whenever a PPP connection is established, DNS servers will be sent to the
190 user, both a primary and a secondary. If either is set to 0.0.0.0, then that
191 one will not be sent.
192 </LI>
193
194 <LI><B>save_state</B> (boolean)<BR>
195 When l2tpns receives a STGTERM it will write out its current
196 ip_address_pool, session and tunnel tables to disk prior to exiting to
197 be re-loaded at startup. The validity of this data is obviously quite
198 short and the intent is to allow an sessions to be retained over a
199 software upgrade.
200 </LI>
201
202 <LI><B>primary_radius</B> (ip address)
203 <LI><B>secondary_radius</B> (ip address)<BR>
204 Sets the RADIUS servers used for both authentication and accounting.
205 If the primary server does not respond, then the secondary RADIUS
206 server will be tried.<br>
207 <strong>Note:</strong> in addition to the source IP address and
208 identifier, the RADIUS server <strong>must</strong> include the source
209 port when detecting duplicates to supress (in order to cope with a
210 large number of sessions comming on-line simultaneously l2tpns uses a
211 set of udp sockets, each with a seperate identifier).
212 </LI>
213
214 <LI><B>primary_radius_port</B> (short)
215 <LI><B>secondary_radius_port</B> (short)<BR>
216 Sets the authentication ports for the primary and secondary RADIUS
217 servers. The accounting port is one more than the authentication
218 port. If no RADIUS ports are given, the authentication port defaults
219 to 1645, and the accounting port to 1646.
220 </LI>
221
222 <LI><B>radius_accounting</B> (boolean)<BR>
223 If set to true, then RADIUS accounting packets will be sent. This
224 means that a Start record will be sent when the session is
225 successfully authenticated, and a Stop record will be sent when the
226 session is closed.
227 </LI>
228
229 <LI><B>radius_secret</B> (string)<BR>
230 This secret will be used in all RADIUS queries. If this is not set then
231 RADIUS queries will fail.
232 </LI>
233
234 <LI><B>bind_address</B> (ip address)<BR>
235 When the tun interface is created, it is assigned the address
236 specified here. If no address is given, 1.1.1.1 is used. Packets
237 containing user traffic should be routed via this address if given,
238 otherwise the primary address of the machine.
239 </LI>
240
241 <LI><B>peer_address</B> (ip address)<BR>
242 Address to send to clients as the default gateway.
243 </L1>
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 </LI>
251
252 <LI><B>throttle_speed</B> (int)<BR>
253 Sets the default speed (in kbits/s) which sessions will be limited to.
254 If this is set to 0, then throttling will not be used at all. Note:
255 You can set this by the CLI, but changes will not affect currently
256 connected users.
257 </LI>
258
259 <LI><B>throttle_buckets</B> (int)<BR>
260 Number of token buckets to allocate for throttling. Each throttled
261 session requires two buckets (in and out).
262 </LI>
263
264 <LI><B>accounting_dir</B> (string)<BR>
265 If set to a directory, then every 5 minutes the current usage for
266 every connected use will be dumped to a file in this directory. Each
267 file dumped begins with a header, where each line is prefixed by #.
268 Following the header is a single line for every connected user, fields
269 separated by a space.<BR> The fields are username, ip, qos,
270 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
271 2 if the user is throttled.
272 </LI>
273
274 <LI><B>setuid</B> (int)<BR>
275 After starting up and binding the interface, change UID to this. This
276 doesn't work properly.
277 </LI>
278
279 <LI><B>dump_speed</B> (boolean)<BR>
280 If set to true, then the current bandwidth utilization will be logged every
281 second. Even if this is disabled, you can see this information by running
282 the <EM>uptime</EM> command on the CLI.
283 </LI>
284
285 <LI><B>cleanup_interval</B> (int)<BR>
286 Interval between regular cleanups (in seconds).
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 </LI>
294
295 <LI><B>scheduler_fifo</B> (boolean)<BR>
296 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
297 causes the kernel to immediately preempt any currently running SCHED_OTHER
298 (normal) process in favour of l2tpns when it becomes runnable.
299 Ignored on uniprocessor systems.
300 </LI>
301
302 <LI><B>lock_pages</B> (boolean)<BR>
303 Keep all pages mapped by the l2tpns process in memory.
304 </LI>
305
306 <LI><B>icmp_rate</B> (int)<BR>
307 Maximum number of host unreachable ICMP packets to send per second.
308 </LI>
309
310 <LI><B>cluster_address</B> (ip address)<BR>
311 Multicast cluster address (default: 239.192.13.13). See the section
312 on <A HREF="#Clustering">Clustering</A> for more information.
313 </LI>
314
315 <LI><B>cluster_interface</B> (string)<BR>
316 Interface for cluster packets (default: eth0).
317 </LI>
318
319 <LI><B>cluster_hb_interval</B> (int)<BR>
320 Interval in tenths of a second between cluster heartbeat/pings.
321 </LI>
322
323 <LI><B>cluster_hb_timeout</B> (int)<BR>
324 Cluster heartbeat timeout in tenths of a second. A new master will be
325 elected when this interval has been passed without seeing a heartbeat
326 from the master.
327 </LI>
328 </UL>
329
330 <P>BGP routing configuration is entered by the command:
331 The routing configuration section is entered by the command
332 <DL><DD><B>router bgp</B> <I>as</I></DL>
333 where <I>as</I> specifies the local AS number.
334
335 <P>Subsequent lines prefixed with
336 <DL><DD><B>neighbour</B> <I>peer</I></DL>
337 define the attributes of BGP neighhbours. Valid commands are:
338 <DL>
339 <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
340 <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
341 </DL>
342
343 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
344 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
345 <I>hold</I> are the timer values in seconds.
346
347 <P>Named access-lists are configured using one of the commands:
348 <DL>
349 <DD><B>ip access-list standard</B> <I>name</I>
350 <DD><B>ip access-list extended</B> <I>name</I>
351 </DL>
352
353 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
354 define the body of the access-list. Standard access-list syntax:
355 <DL>
356 <DD>{<B>permit</B>|<B>deny</B>}
357 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
358 [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
359 </DL>
360
361 Extended access-lists:
362
363 <DL>
364 <DD>{<B>permit</B>|<B>deny</B>} <B>ip</B>
365 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
366 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
367 <DD>{<B>permit</B>|<B>deny</B>} <B>udp</B>
368 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
369 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
370 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
371 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
372 <DD>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
373 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
374 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
375 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
376 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
377 [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
378 {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>} ...]
379 </DL>
380
381 <H3 ID="users">users</H3>
382
383 Usernames and passwords for the command-line interface are stored in
384 this file. The format is <I>username</I><B>:</B><I>password</I> where
385 <I>password</I> may either by plain text, an MD5 digest (prefixed by
386 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
387 plain text by the prefix <B>{crypt}</B>.<P>
388
389 The username <B>enable</B> has a special meaning and is used to set
390 the enable password.<P>
391
392 <B>Note:</B> If this file doesn't exist, then anyone who can get to
393 port 23 will be allowed access without a username / password.<P>
394
395 <H3 ID="ip-pool">ip_pool</H3>
396
397 This file is used to configure the IP address pool which user
398 addresses are assigned from. This file should contain either an IP
399 address or a CIDR network per line. e.g.:<P>
400
401 <PRE>
402 192.168.1.1
403 192.168.1.2
404 192.168.1.3
405 192.168.4.0/24
406 172.16.0.0/16
407 10.0.0.0/8
408 </PRE>
409
410 Keep in mind that l2tpns can only handle 65535 connections per
411 process, so don't put more than 65535 IP addresses in the
412 configuration file. They will be wasted.
413
414 <H3 ID="build-garden">build-garden</H3>
415
416 The garden plugin on startup creates a NAT table called "garden" then
417 sources the <B>build-garden</B> script to populate that table. All
418 packets from gardened users will be sent through this table. Example:
419
420 <PRE>
421 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
422 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
423 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
424 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
425 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
426 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
427 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
428 iptables -t nat -A garden -p icmp -j ACCEPT
429 iptables -t nat -A garden -j DROP
430 </PRE>
431
432 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
433
434 A running l2tpns process can be controlled in a number of ways. The primary
435 method of control is by the Command-Line Interface (CLI).<P>
436
437 You can also remotely send commands to modules via the nsctl client
438 provided.<P>
439
440 Also, there are a number of signals that l2tpns understands and takes action
441 when it receives them.
442
443 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
444
445 You can access the command line interface by telnet'ing to port 23.
446 There is no IP address restriction, so it's a good idea to firewall
447 this port off from anyone who doesn't need access to it. See
448 <A HREF="#users">users</A> for information on restricting access based
449 on a username and password.<P>
450
451 The CLI gives you real-time control over almost everything in
452 the process. The interface is designed to look like a Cisco
453 device, and supports things like command history, line editing and
454 context sensitive help. This is provided by linking with the
455 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
456 library. Some general documentation of the interface is
457 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
458 here</A>.<P>
459
460 After you have connected to the telnet port (and perhaps logged in), you
461 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
462
463 Enter <EM>help</EM> to get a list of possible commands. A brief
464 overview of the more important commands follows:
465
466 <UL>
467 <LI><B>show session</B><BR>
468 Without specifying a session ID, this will list all tunnels currently
469 connected. If you specify a session ID, you will be given all
470 information on a single tunnel. Note that the full session list can
471 be around 185 columns wide, so you should probably use a wide terminal
472 to see the list properly.<P>
473 The columns listed in the overview are:
474 <TABLE>
475 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
476 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
477 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
478 authentication. If this is *, then LCP authentication has not
479 completed.</TD></TR>
480 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
481 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
482 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
483 session is being snooped. See <EM>snoop</EM>.</TD></TR>
484 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
485 currently throttled. See <EM>throttle</EM>.</TD></TR>
486 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
487 trapped in the walled garden. This field is present even if the
488 garden module is not loaded.</TD></TR>
489 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
490 session started</TD></TR>
491 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
492 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
493 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
494 detected on the session</TD></TR>
495 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
496 connected to.</TD></TR>
497 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
498 provided during the session setup. This field is generated by the
499 LAC.</TD></TR>
500 </TABLE>
501 <P>
502 </LI>
503
504 <LI><B>show users</B><BR>
505 With no arguments, display a list of currently connected users. If an
506 argument is given, the session details for the given username are
507 displayed.
508 </LI>
509
510 <LI><B>show tunnel</B><BR>
511 This will show all the open tunnels in a summary, or detail on a single
512 tunnel if you give a tunnel id.<P>
513 The columns listed in the overview are:
514 <TABLE>
515 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
516 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
517 provided by the LAC. This has no relation to DNS, it is just
518 a text field.</TD></TR>
519 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
520 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
521 Opening</TD></TR>
522 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
523 tunnel</TD></TR>
524 </TABLE>
525 <P>
526 </LI>
527
528 <LI><B>show pool</B><BR>
529 Displays the current IP address pool allocation. This will only display
530 addresses that are in use, or are reserved for re-allocation to a
531 disconnected user.<P>
532 If an address is not currently in use, but has been used, then in the User
533 column the username will be shown in square brackets, followed by the time
534 since the address was used:
535 <PRE>
536 IP Address Used Session User
537 192.168.100.6 N [joe.user] 1548s
538 </PRE>
539 <P>
540 </LI>
541
542 <LI><B>show radius</B><BR>
543 Show a summary of the in-use RADIUS sessions. This list should not be very
544 long, as RADIUS sessions should be cleaned up as soon as they are used. The
545 columns listed are:
546 <TABLE>
547 <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request. This is
548 sent in the packet to the RADIUS server for identification.</TD></TR>
549 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
550 AUTH, IPCP, START, STOP, NULL.</TD></TR>
551 <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
552 request is associated with</TD></TR>
553 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
554 request, it will retry at this time. This is a unix timestamp.</TD></TR>
555 <TR><TD><B>Try</B></TD><TD>Retry count. The RADIUS request is
556 discarded after 3 retries.</TD></TR>
557 </TABLE>
558 <P>
559 </LI>
560
561 <LI><B>show running-config</B><BR>
562 This will list the current running configuration. This is in a format that
563 can either be pasted into the configuration file, or run directly at the
564 command line.
565 <P>
566 </LI>
567
568 <LI><B>show counters</B><BR>
569 Internally, counters are kept of key values, such as bytes and packets
570 transferred, as well as function call counters. This function displays all
571 these counters, and is probably only useful for debugging.<P>
572 You can reset these counters by running <EM>clear counters</EM>.
573 <P>
574 </LI>
575
576 <LI><B>show cluster</B><BR>
577 Show cluster status. Shows the cluster state for this server
578 (Master/Slave), information about known peers and (for slaves) the
579 master IP address, last packet seen and up-to-date status.<P>
580 See <A HREF="#Clustering">Clustering</A> for more information.
581 <P>
582 </LI>
583
584 <LI><B>write memory</B><BR>
585 This will write the current running configuration to the config file
586 <B>startup-config</B>, which will be run on a restart.
587 <P>
588 </LI>
589
590 <LI><B>snoop</B><BR>
591 You must specify a username, IP address and port. All packets for the
592 current session for that username will be forwarded to the given
593 host/port. Specify <EM>no snoop username</EM> to disable interception
594 for the session.<P>
595
596 If you want interception to be permanent, you will have to modify the RADIUS
597 response for the user. See <A HREF="#Interception">Interception</A>.
598 <P>
599 </LI>
600
601 <LI><B>throttle</B><BR>
602 You must specify a username, which will be throttled for the current
603 session. Specify <EM>no throttle username</EM> to disable throttling
604 for the current session.<P>
605
606 If you want throttling to be permanent, you will have to modify the
607 RADIUS response for the user. See <A HREF="#Throttling">Throttling</A>.
608 <P>
609 </LI>
610
611 <LI><B>drop session</B><BR>
612 This will cleanly disconnect a session. You must specify a session id, which
613 you can get from <EM>show session</EM>. This will send a disconnect message
614 to the remote end.
615 <P>
616 </LI>
617
618 <LI><B>drop tunnel</B><BR>
619 This will cleanly disconnect a tunnel, as well as all sessions on that
620 tunnel. It will send a disconnect message for each session individually, and
621 after 10 seconds it will send a tunnel disconnect message.
622 <P>
623 </LI>
624
625 <LI><B>uptime</B><BR>
626 This will show how long the l2tpns process has been running, and the current
627 bandwidth utilization:
628 <PRE>
629 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
630 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
631 </PRE>
632 The bandwidth line contains 4 sets of values.<BR>
633 UDP-ETH is the current bandwidth going from the LAC to the ethernet
634 (user uploads), in mbits/sec.<BR>
635 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
636 downloads).<BR>
637 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
638 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
639 <P>
640 These counters are updated every second.
641 <P>
642 </LI>
643
644 <LI><B>configure terminal</B><BR>
645 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
646 The following commands are valid in this mode:<P>
647 </LI>
648
649 <LI><B>load plugin</B><BR>
650 Load a plugin. You must specify the plugin name, and it will search in
651 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
652 <EM>remove plugin</EM>.
653 <P>
654 </LI>
655
656 <LI><B>set</B><BR>
657 Set a configuration variable. You must specify the variable name, and
658 the value. If the value contains any spaces, you should quote the
659 value with double (") or single (') quotes.<P>
660
661 You can set any <A HREF="#startup-config">startup-config</A> value in
662 this way, although some may require a restart to take effect.<P>
663 </LI>
664 </UL>
665
666 <H3 ID="nsctl">nsctl</H3>
667
668 nsctl allows messages to be passed to plugins.<P>
669
670 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
671 <STRONG>nsctl</STRONG>(8) for more details.<P>
672
673 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
674 <EM>help</EM>. Any other commands are passed to plugins for processing.
675
676 <H3 ID="Signals">Signals</H3>
677
678 While the process is running, you can send it a few different signals, using
679 the kill command.
680 <PRE>
681 killall -HUP l2tpns
682 </PRE>
683
684 The signals understood are:
685 <UL>
686 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
687 <LI>SIGTERM / SIGINT - Shut down for a restart. This will dump the current
688 state to disk (if <EM>save_state</EM> is set to true). Upon restart, the
689 process will read this saved state to resume active sessions.<P>
690 <LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
691 every active session and tunnel before shutting down. This is a good idea
692 when upgrading the code, as no sessions will be left with the remote end
693 thinking they are open.</LI>
694 </UL>
695
696 <H2 ID="Throttling">Throttling</H2>
697
698 l2tpns contains support for slowing down user sessions to whatever speed you
699 desire. You must first enable the global setting <EM>throttle_speed</EM>
700 before this will be activated.<P>
701
702 If you wish a session to be throttled permanently, you should set the
703 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
704 will be handled by the <EM>autothrottle</EM> module.<P>
705
706 Otherwise, you can enable and disable throttling an active session using
707 the <EM>throttle</EM> CLI command.<P>
708
709 <H2 ID="Interception">Interception</H2>
710
711 You may have to deal with legal requirements to be able to intercept a
712 user's traffic at any time. l2tpns allows you to begin and end interception
713 on the fly, as well as at authentication time.<P>
714
715 When a user is being intercepted, a copy of every packet they send and
716 receive will be sent wrapped in a UDP packet to the IP address and port set
717 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
718 variables.<P>
719
720 The UDP packet contains just the raw IP frame, with no extra headers.<P>
721
722 To enable interception on a connected user, use the <EM>snoop username</EM>
723 and <EM>no snoop username</EM> CLI commands. These will enable interception
724 immediately.<P>
725
726 If you wish the user to be intercepted whenever they reconnect, you will
727 need to modify the RADIUS response to include the Vendor-Specific value
728 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
729 you need to have the <EM>autosnoop</EM> module loaded.<P>
730
731 <H2 ID="Authentication">Authentication</H2>
732
733 Whenever a session connects, it is not fully set up until authentication is
734 completed. The remote end must send a PPP CHAP or PPP PAP authentication
735 request to l2tpns.<P>
736
737 This request is sent to the RADIUS server, which will hopefully respond with
738 Auth-Accept or Auth-Reject.<P>
739
740 If Auth-Accept is received, the session is set up and an IP address is
741 assigned. The RADIUS server can include a Framed-IP-Address field in the
742 reply, and that address will be assigned to the client. It can also include
743 specific DNS servers, and a Framed-Route if that is required.<P>
744
745 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
746 at which point they should disconnect. The exception to this is when the
747 walled garden module is loaded, in which case the user still receives the
748 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
749 should not receive any service.<P>
750
751 The RADIUS reply can also contain a Vendor-Specific attribute called
752 Cisco-Avpair. This field is a freeform text field that most Cisco
753 devices understand to contain configuration instructions for the session. In
754 the case of l2tpns it is expected to be of the form
755 <PRE>
756 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
757 </PRE>
758
759 Each key-value pair is separated and passed to any modules loaded. The
760 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
761 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
762 a user who is to be throttled and intercepted, the Cisco-Avpair value should
763 contain:
764 <PRE>
765 intercept=yes,throttle=yes
766 </PRE>
767
768 <H2 ID="Plugins">Plugins</H2>
769
770 So as to make l2tpns as flexible as possible (I know the core code is pretty
771 difficult to understand), it includes a plugin API, which you can use to
772 hook into certain events.<P>
773
774 There are a few example modules included - autosnoop, autothrottle and
775 garden.<P>
776
777 When an event happens that has a hook, l2tpns looks for a predefined
778 function name in every loaded module, and runs them in the order the modules
779 were loaded.<P>
780
781 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
782 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
783 modules should be run for this event.<P>
784 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
785 no further processing should be done for this event. <EM>Use this with care.</EM>
786
787 Every event function called takes a specific structure named
788 param_<EM>event</EM>, which varies in content with each event. The
789 function name for each event will be <B>plugin_<EM>event</EM></B>,
790 so for the event <EM>timer</EM>, the function declaration should look like:
791 <PRE>
792 int plugin_timer(struct param_timer *data);
793 </PRE>
794
795 A list of the available events follows, with a list of all the fields in the
796 supplied structure:
797 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
798 <TABLE CELLSPACING=1 CELLPADDING=3>
799 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
800 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
801 <TD>This is called after a RADIUS response has been
802 received, but before it has been processed by the
803 code. This will allow you to modify the response in
804 some way.
805 </TD>
806 <TD>
807 <UL>
808 <LI>t - Tunnel ID</LI>
809 <LI>s - Session ID</LI>
810 <LI>username</LI>
811 <LI>password</LI>
812 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
813 <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
814 </UL>
815 </TD>
816 </TR>
817 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
818 <TD>This is called after a RADIUS response has been
819 received, and the basic checks have been performed. This
820 is what the garden module uses to force authentication
821 to be accepted.
822 </TD>
823 <TD>
824 <UL>
825 <LI>t - Tunnel ID</LI>
826 <LI>s - Session ID</LI>
827 <LI>username</LI>
828 <LI>auth_allowed - This is already set to true or
829 false depending on whether authentication has been
830 allowed so far. You can set this to 1 or 0 to force
831 allow or disallow authentication</LI>
832 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
833 </UL>
834 </TD>
835 </TR>
836 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
837 <TD>This is called whenever a session receives a
838 packet. <FONT COLOR=RED>Use this sparingly, as this will
839 seriously slow down the system.</FONT>
840 </TD>
841 <TD>
842 <UL>
843 <LI>t - Tunnel ID</LI>
844 <LI>s - Session ID</LI>
845 <LI>buf - The raw packet data</LI>
846 <LI>len - The length of buf</LI>
847 </UL>
848 </TD>
849 </TR>
850 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
851 <TD>This is called whenever a session sends a
852 packet. <FONT COLOR=RED>Use this sparingly, as this will
853 seriously slow down the system.</FONT>
854 </TD>
855 <TD>
856 <UL>
857 <LI>t - Tunnel ID</LI>
858 <LI>s - Session ID</LI>
859 <LI>buf - The raw packet data</LI>
860 <LI>len - The length of buf</LI>
861 </UL>
862 </TD>
863 </TR>
864 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
865 <TD>This is run every second, no matter what is happening.
866 This is called from a signal handler, so make sure anything
867 you do is reentrant.
868 </TD>
869 <TD>
870 <UL>
871 <LI>time_now - The current unix timestamp</LI>
872 </UL>
873 </TD>
874 </TR>
875 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
876 <TD>This is called after a session is fully set up. The
877 session is now ready to handle traffic.
878 </TD>
879 <TD>
880 <UL>
881 <LI>t - Tunnel ID</LI>
882 <LI>s - Session ID</LI>
883 </UL>
884 </TD>
885 </TR>
886 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
887 <TD>This is called when a session is about to be shut down.
888 This may be called multiple times for the same session.
889 </TD>
890 <TD>
891 <UL>
892 <LI>t - Tunnel ID</LI>
893 <LI>s - Session ID</LI>
894 </UL>
895 </TD>
896 </TR>
897 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
898 <TD>This is called whenever a RADIUS response includes a
899 Cisco-Avpair value. The value is split up into
900 <EM>key=value</EM> pairs, and each is processed through all
901 modules.
902 </TD>
903 <TD>
904 <UL>
905 <LI>t - Tunnel ID</LI>
906 <LI>s - Session ID</LI>
907 <LI>key</LI>
908 <LI>value</LI>
909 </UL>
910 </TD>
911 </TR>
912 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
913 <TD>This is called in whenever a nsctl packet is received.
914 This should handle the packet and form a response if
915 required.
916 </TD>
917 <TD>
918 <UL>
919 <LI>buf - The raw packet data</LI>
920 <LI>l - The raw packet data length</LI>
921 <LI>source_ip - Where the request came from</LI>
922 <LI>source_port - Where the request came from</LI>
923 <LI>response - Allocate a buffer and put your response in here</LI>
924 <LI>response_length - Length of response</LI>
925 <LI>send_response - true or false whether a response
926 should be sent. If you set this to true, you must
927 allocate a response buffer.</LI>
928 <LI>type - Type of request (see nsctl.c)</LI>
929 <LI>id - ID of request</LI>
930 <LI>data - I'm really not sure</LI>
931 <LI>data_length - Length of data</LI>
932 </UL>
933 </TD>
934 </TR>
935 </TABLE>
936 </TD></TR></TABLE>
937
938 <H2 ID="WalledGarden">Walled Garden</H2>
939
940 Walled Garden is implemented so that you can provide perhaps limited service
941 to sessions that incorrectly authenticate.<P>
942
943 Whenever a session provides incorrect authentication, and the
944 RADIUS server responds with Auth-Reject, the walled garden module
945 (if loaded) will force authentication to succeed, but set the flag
946 <EM>garden</EM> in the session structure, and adds an iptables rule to
947 the <B>garden_users</B> chain to force all packets for the session's IP
948 address to traverse the <B>garden</B> chain.<P>
949
950 This doesn't <EM>just work</EM>. To set this all up, you will to
951 setup the <B>garden</B> nat table with the
952 <A HREF="#build-garden">build-garden</A> script with rules to limit
953 user's traffic. For example, to force all traffic except DNS to be
954 forwarded to 192.168.1.1, add these entries to your
955 <EM>build-garden</EM>:
956 <PRE>
957 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
958 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
959 </PRE>
960
961 l2tpns will add entries to the garden_users chain as appropriate.<P>
962
963 You can check the amount of traffic being captured using the following
964 command:
965 <PRE>
966 iptables -t nat -L garden -nvx
967 </PRE>
968
969 <H2 ID="Filtering">Filtering</H2>
970
971 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
972 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
973 access-list <I>filter</I> should be applied to traffic from the
974 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
975 customer.
976
977 <H2 ID="Clustering">Clustering</H2>
978
979 An l2tpns cluster consists of of one* or more servers configured with
980 the same configuration, notably the multicast <B>cluster_address</B>.<P>
981
982 *A stand-alone server is simply a degraded cluster.<P>
983
984 Initially servers come up as cluster slaves, and periodically (every
985 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
986 containing the start time of the process to the multicast
987 <B>cluster_address</B>.<P>
988
989 A cluster master sends heartbeat rather than ping packets, which
990 contain those session and tunnel changes since the last heartbeat.<P>
991
992 When a slave has not seen a heartbeat within
993 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
994 examining the list of peers it has seen pings from and determines
995 which of these and itself is the "best" candidate to be master.
996 "Best" in this context means the server with the highest uptime (the
997 highest IP address is used as a tie-breaker in the case of equal
998 uptimes).<P>
999
1000 After discovering a master, and determining that it is up-to-date (has
1001 seen an update for all in-use sessions and tunnels from heartbeat
1002 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1003 the <B>bind_address</B> and for all addresses/networks in
1004 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1005 the session state, as well as packets for throttled or gardened
1006 sessions are forwarded to the master for handling. In addition, byte
1007 counters for session traffic are periodically forwarded.<P>
1008
1009 A master, when determining that it has at least one up-to-date slave
1010 will drop all routes (raising them again if all slaves disappear) and
1011 subsequently handle only packets forwarded to it by the slaves.<P>
1012
1013 <H2 ID="Routing">Routing</H2>
1014 If you are running a single instance, you may simply statically route
1015 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1016 arp).<P>
1017
1018 For a cluster, configure the members as BGP neighbours on your router
1019 and configure multi-path load-balancing. Cisco uses "maximum-paths
1020 ibgp" for IBGP. If this is not supported by your IOS revision, you
1021 can use "maximum-paths" (which works for EBGP) and set
1022 <B>as_number</B> to a private value such as 64512.<P>
1023
1024 <H2 ID="Performance">Performance</H2>
1025
1026 Performance is great.<P>
1027
1028 I'd like to include some pretty graphs here that show a linear performance
1029 increase, with no impact by number of connected sessions.<P>
1030
1031 That's really what it looks like.<P>
1032
1033 <BR>
1034 David Parrish<BR>
1035 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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