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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="#AvoidingFragmentation">Avoiding Fragmentation</A></LI>
60 <LI><A HREF="#Performance">Performance</A></LI>
61 </OL>
62
63 <H2 ID="Overview">Overview</H2>
64 l2tpns is half of a complete L2TP implementation. It supports only the
65 LNS side of the connection.<P>
66
67 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
68 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns
69 implements PPP over L2TP only.<P>
70
71 There are a couple of other L2TP implementations, of which <A
72 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
73 most popular. l2tpd also will handle being either end of a tunnel, and
74 is a lot more configurable than l2tpns. However, due to the way it works,
75 it is nowhere near as scalable.<P>
76
77 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
78 and send packets. Using some packet manipulation it doesn't require a
79 single interface per connection, as l2tpd does.<P>
80
81 This allows it to scale extremely well to very high loads and very high
82 numbers of connections.<P>
83
84 It also has a plugin architecture which allows custom code to be run
85 during processing. An example of this is in the walled garden module
86 included.<P>
87
88 <BR>
89 <EM>Documentation is not my best skill. If you find any problems
90 with this document, or if you wish to contribute, please email <A
91 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
92
93 <H2 ID="Installation">Installation</H2>
94 <H3 ID="Requirements">Requirements</H3>
95
96 <OL>
97 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
98 compiled in, or as a module.</LI>
99
100 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
101 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
102 </OL>
103
104 <H3 ID="Compile">Compile</H3>
105
106 You can generally get away with just running <B>make</B> from the source
107 directory. This will compile the daemon, associated tools and any modules
108 shipped with the distribution.<P>
109
110 <H3 ID="Install">Install</H3>
111
112 After you have successfully compiled everything, run <B>make
113 install</B> to install it. By default, the binaries are installed into
114 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
115 modules into <EM>/usr/lib/l2tpns</EM>.<P>
116
117 You will definately need to edit the configuration files before you
118 start. See the <A HREF="#Configuration">Configuration</A> section for
119 more information.<P>
120
121 <H3 ID="Running">Running</H3>
122
123 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it. It does
124 not detach to a daemon process, so you should perhaps run it from init.<P>
125
126 By default there is no log destination set, so all log messages will go to
127 stdout.<P>
128
129 <H2 ID="Configuration">Configuration</H2>
130
131 All configuration of the software is done from the files installed into
132 /etc/l2tpns.
133
134 <H3 ID="startup-config">startup-config</H3>
135
136 This is the main configuration file for l2tpns. The format of the file is a
137 list of commands that can be run through the command-line interface. This
138 file can also be written directly by the l2tpns process if a user runs the
139 <EM>write memory</EM> command, so any comments will be lost. However if your
140 policy is not to write the config by the program, then feel free to comment
141 the file with a # or ! at the beginning of the line.<P>
142
143 A list of the possible configuration directives follows. Each of these
144 should be set by a line like:<P>
145 <PRE>
146 set configstring "value"
147 set ipaddress 192.168.1.1
148 set boolean true
149 </PRE>
150
151 <P>
152 <UL>
153 <LI><B>debug</B> (int)<BR>
154 Sets the level of messages that will be written to the log file. The value
155 should be between 0 and 5, with 0 being no debugging, and 5 being the
156 highest. A rough description of the levels is:
157 <OL>
158 <LI VALUE=0>Critical Errors - Things are probably broken</LI>
159 <LI>Errors - Things might have gone wrong, but probably will recover</LI>
160 <LI>Warnings - Just in case you care what is not quite perfect</LI>
161 <LI>Information - Parameters of control packets</LI>
162 <LI>Calls - For tracing the execution of the code</LI>
163 <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
164 </OL><P>
165 Note that the higher you set the debugging level, the slower the program
166 will run. Also, at level 5 a LOT of information will be logged. This should
167 only ever be used for working out why it doesn't work at all.
168 </LI>
169
170 <LI><B>log_file</B> (string)<BR>
171 This will be where all logging and debugging information is written
172 to. This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or
173 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
174 is any one of the syslog logging facilities, such as local5.
175 </LI>
176
177 <LI><B>pid_file</B> (string)<BR>
178 If set, the process id will be written to the specified file. The
179 value must be an absolute path.
180 </LI>
181
182 <LI><B>l2tp_secret</B> (string)<BR>
183 The secret used by l2tpns for authenticating tunnel request. Must be
184 the same as the LAC, or authentication will fail. Only actually be
185 used if the LAC requests authentication.
186 </LI>
187
188 <LI><B>ppp_restart_time</B> (int)<BR>
189 <B>ppp_max_configure</B> (int)<BR>
190 <B>ppp_max_failure</B> (int)<BR>
191 PPP counter and timer values, as described in &sect;4.1 of
192 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661</a>.
193 </LI>
194
195 <LI><B>primary_dns</B> (ip address)
196 <LI><B>secondary_dns</B> (ip address)<BR>
197 Whenever a PPP connection is established, DNS servers will be sent to the
198 user, both a primary and a secondary. If either is set to 0.0.0.0, then that
199 one will not be sent.
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>radius_authtypes</B> (string)</BR>
235 A comma separated list of supported RADIUS authentication methods
236 (<B>pap</B> or <B>chap</B>), in order of preference (default <B>pap</B>).
237 </LI>
238
239 <LI><B>radius_dae_port</B> (short)<BR>
240 Port for DAE RADIUS (Packet of Death/Disconnect, Change of Authorization)
241 requests (default: <B>3799</B>).
242 </LI>
243
244 <LI><B>allow_duplicate_users</B> (boolean)</BR>
245 Allow multiple logins with the same username. If false (the default),
246 any prior session with the same username will be dropped when a new
247 session is established.
248 </LI>
249
250 <LI><B>bind_address</B> (ip address)<BR>
251 When the tun interface is created, it is assigned the address
252 specified here. If no address is given, 1.1.1.1 is used. Packets
253 containing user traffic should be routed via this address if given,
254 otherwise the primary address of the machine.
255 </LI>
256
257 <LI><B>peer_address</B> (ip address)<BR>
258 Address to send to clients as the default gateway.
259 </L1>
260
261 <LI><B>send_garp</B> (boolean)<BR>
262 Determines whether or not to send a gratuitous ARP for the
263 bind_address when the server is ready to handle traffic (default:
264 true).<BR>
265 This value is ignored if BGP is configured.
266 </LI>
267
268 <LI><B>throttle_speed</B> (int)<BR>
269 Sets the default speed (in kbits/s) which sessions will be limited to.
270 If this is set to 0, then throttling will not be used at all. Note:
271 You can set this by the CLI, but changes will not affect currently
272 connected users.
273 </LI>
274
275 <LI><B>throttle_buckets</B> (int)<BR>
276 Number of token buckets to allocate for throttling. Each throttled
277 session requires two buckets (in and out).
278 </LI>
279
280 <LI><B>accounting_dir</B> (string)<BR>
281 If set to a directory, then every 5 minutes the current usage for
282 every connected use will be dumped to a file in this directory. Each
283 file dumped begins with a header, where each line is prefixed by #.
284 Following the header is a single line for every connected user, fields
285 separated by a space.<BR> The fields are username, ip, qos,
286 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
287 2 if the user is throttled.
288 </LI>
289
290 <LI><B>setuid</B> (int)<BR>
291 After starting up and binding the interface, change UID to this. This
292 doesn't work properly.
293 </LI>
294
295 <LI><B>dump_speed</B> (boolean)<BR>
296 If set to true, then the current bandwidth utilization will be logged every
297 second. Even if this is disabled, you can see this information by running
298 the <EM>uptime</EM> command on the CLI.
299 </LI>
300
301 <LI><B>multi_read_count</B> (int)<BR>
302 Number of packets to read off each of the UDP and TUN fds when
303 returned as readable by select (default: 10). Avoids incurring the
304 unnecessary system call overhead of select on busy servers.
305 </LI>
306
307 <LI><B>scheduler_fifo</B> (boolean)<BR>
308 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
309 causes the kernel to immediately preempt any currently running SCHED_OTHER
310 (normal) process in favour of l2tpns when it becomes runnable.
311 Ignored on uniprocessor systems.
312 </LI>
313
314 <LI><B>lock_pages</B> (boolean)<BR>
315 Keep all pages mapped by the l2tpns process in memory.
316 </LI>
317
318 <LI><B>icmp_rate</B> (int)<BR>
319 Maximum number of host unreachable ICMP packets to send per second.
320 </LI>
321
322 <LI><B>packet_limit</B> (int><BR>
323 Maximum number of packets of downstream traffic to be handled each
324 tenth of a second per session. If zero, no limit is applied (default:
325 0). Intended as a DoS prevention mechanism and not a general
326 throttling control (packets are dropped, not queued).
327 </LI>
328
329 <LI><B>cluster_address</B> (ip address)<BR>
330 Multicast cluster address (default: 239.192.13.13). See the section
331 on <A HREF="#Clustering">Clustering</A> for more information.
332 </LI>
333
334 <LI><B>cluster_interface</B> (string)<BR>
335 Interface for cluster packets (default: eth0).
336 </LI>
337
338 <LI><B>cluster_hb_interval</B> (int)<BR>
339 Interval in tenths of a second between cluster heartbeat/pings.
340 </LI>
341
342 <LI><B>cluster_hb_timeout</B> (int)<BR>
343 Cluster heartbeat timeout in tenths of a second. A new master will be
344 elected when this interval has been passed without seeing a heartbeat
345 from the master.
346 </LI>
347
348 <LI><B>cluster_master_min_adv</B> (int)<BR>
349 Determines the minumum number of up to date slaves required before the
350 master will drop routes (default: 1).
351 </LI>
352 </UL>
353
354 <P>BGP routing configuration is entered by the command:
355 The routing configuration section is entered by the command
356 <DL><DD><B>router bgp</B> <I>as</I></DL>
357 where <I>as</I> specifies the local AS number.
358
359 <P>Subsequent lines prefixed with
360 <DL><DD><B>neighbour</B> <I>peer</I></DL>
361 define the attributes of BGP neighhbours. Valid commands are:
362 <DL>
363 <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
364 <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
365 </DL>
366
367 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
368 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
369 <I>hold</I> are the timer values in seconds.
370
371 <P>Named access-lists are configured using one of the commands:
372 <DL>
373 <DD><B>ip access-list standard</B> <I>name</I>
374 <DD><B>ip access-list extended</B> <I>name</I>
375 </DL>
376
377 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
378 define the body of the access-list. Standard access-list syntax:
379 <DL>
380 <DD>{<B>permit</B>|<B>deny</B>}
381 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
382 [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
383 </DL>
384
385 Extended access-lists:
386
387 <DIV STYLE="margin-left: 4em; text-indent: -2em">
388 <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
389 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
390 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
391 <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
392 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
393 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
394 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
395 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
396 [<B>fragments</B>]
397 <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
398 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
399 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
400 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
401 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
402 [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
403 {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
404 ...|<B>fragments</B>]
405 </DIV>
406
407 <H3 ID="users">users</H3>
408
409 Usernames and passwords for the command-line interface are stored in
410 this file. The format is <I>username</I><B>:</B><I>password</I> where
411 <I>password</I> may either by plain text, an MD5 digest (prefixed by
412 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
413 plain text by the prefix <B>{crypt}</B>.<P>
414
415 The username <B>enable</B> has a special meaning and is used to set
416 the enable password.<P>
417
418 <B>Note:</B> If this file doesn't exist, then anyone who can get to
419 port 23 will be allowed access without a username / password.<P>
420
421 <H3 ID="ip-pool">ip_pool</H3>
422
423 This file is used to configure the IP address pool which user
424 addresses are assigned from. This file should contain either an IP
425 address or a CIDR network per line. e.g.:<P>
426
427 <PRE>
428 192.168.1.1
429 192.168.1.2
430 192.168.1.3
431 192.168.4.0/24
432 172.16.0.0/16
433 10.0.0.0/8
434 </PRE>
435
436 Keep in mind that l2tpns can only handle 65535 connections per
437 process, so don't put more than 65535 IP addresses in the
438 configuration file. They will be wasted.
439
440 <H3 ID="build-garden">build-garden</H3>
441
442 The garden plugin on startup creates a NAT table called "garden" then
443 sources the <B>build-garden</B> script to populate that table. All
444 packets from gardened users will be sent through this table. Example:
445
446 <PRE>
447 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
448 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
449 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
450 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
451 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
452 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
453 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
454 iptables -t nat -A garden -p icmp -j ACCEPT
455 iptables -t nat -A garden -j DROP
456 </PRE>
457
458 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
459
460 A running l2tpns process can be controlled in a number of ways. The primary
461 method of control is by the Command-Line Interface (CLI).<P>
462
463 You can also remotely send commands to modules via the nsctl client
464 provided.<P>
465
466 Also, there are a number of signals that l2tpns understands and takes action
467 when it receives them.
468
469 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
470
471 You can access the command line interface by telnet'ing to port 23.
472 There is no IP address restriction, so it's a good idea to firewall
473 this port off from anyone who doesn't need access to it. See
474 <A HREF="#users">users</A> for information on restricting access based
475 on a username and password.<P>
476
477 The CLI gives you real-time control over almost everything in
478 the process. The interface is designed to look like a Cisco
479 device, and supports things like command history, line editing and
480 context sensitive help. This is provided by linking with the
481 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
482 library. Some general documentation of the interface is
483 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
484 here</A>.<P>
485
486 After you have connected to the telnet port (and perhaps logged in), you
487 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
488
489 Enter <EM>help</EM> to get a list of possible commands. A brief
490 overview of the more important commands follows:
491
492 <UL>
493 <LI><B>show session</B><BR>
494 Without specifying a session ID, this will list all tunnels currently
495 connected. If you specify a session ID, you will be given all
496 information on a single tunnel. Note that the full session list can
497 be around 185 columns wide, so you should probably use a wide terminal
498 to see the list properly.<P>
499 The columns listed in the overview are:
500 <TABLE>
501 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
502 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
503 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
504 authentication. If this is *, then LCP authentication has not
505 completed.</TD></TR>
506 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
507 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
508 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
509 session is being snooped. See <EM>snoop</EM>.</TD></TR>
510 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
511 currently throttled. See <EM>throttle</EM>.</TD></TR>
512 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
513 trapped in the walled garden. This field is present even if the
514 garden module is not loaded.</TD></TR>
515 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
516 session started</TD></TR>
517 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
518 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
519 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
520 detected on the session</TD></TR>
521 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
522 connected to.</TD></TR>
523 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
524 provided during the session setup. This field is generated by the
525 LAC.</TD></TR>
526 </TABLE>
527 <P>
528 </LI>
529
530 <LI><B>show users</B><BR>
531 With no arguments, display a list of currently connected users. If an
532 argument is given, the session details for the given username are
533 displayed.
534 </LI>
535
536 <LI><B>show tunnel</B><BR>
537 This will show all the open tunnels in a summary, or detail on a single
538 tunnel if you give a tunnel id.<P>
539 The columns listed in the overview are:
540 <TABLE>
541 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
542 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
543 provided by the LAC. This has no relation to DNS, it is just
544 a text field.</TD></TR>
545 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
546 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
547 Opening</TD></TR>
548 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
549 tunnel</TD></TR>
550 </TABLE>
551 <P>
552 </LI>
553
554 <LI><B>show pool</B><BR>
555 Displays the current IP address pool allocation. This will only display
556 addresses that are in use, or are reserved for re-allocation to a
557 disconnected user.<P>
558 If an address is not currently in use, but has been used, then in the User
559 column the username will be shown in square brackets, followed by the time
560 since the address was used:
561 <PRE>
562 IP Address Used Session User
563 192.168.100.6 N [joe.user] 1548s
564 </PRE>
565 <P>
566 </LI>
567
568 <LI><B>show radius</B><BR>
569 Show a summary of the in-use RADIUS sessions. This list should not be very
570 long, as RADIUS sessions should be cleaned up as soon as they are used. The
571 columns listed are:
572 <TABLE>
573 <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request. This is
574 sent in the packet to the RADIUS server for identification.</TD></TR>
575 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
576 AUTH, IPCP, START, STOP, NULL.</TD></TR>
577 <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
578 request is associated with</TD></TR>
579 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
580 request, it will retry at this time. This is a unix timestamp.</TD></TR>
581 <TR><TD><B>Try</B></TD><TD>Retry count. The RADIUS request is
582 discarded after 3 retries.</TD></TR>
583 </TABLE>
584 <P>
585 </LI>
586
587 <LI><B>show running-config</B><BR>
588 This will list the current running configuration. This is in a format that
589 can either be pasted into the configuration file, or run directly at the
590 command line.
591 <P>
592 </LI>
593
594 <LI><B>show counters</B><BR>
595 Internally, counters are kept of key values, such as bytes and packets
596 transferred, as well as function call counters. This function displays all
597 these counters, and is probably only useful for debugging.<P>
598 You can reset these counters by running <EM>clear counters</EM>.
599 <P>
600 </LI>
601
602 <LI><B>show cluster</B><BR>
603 Show cluster status. Shows the cluster state for this server
604 (Master/Slave), information about known peers and (for slaves) the
605 master IP address, last packet seen and up-to-date status.<P>
606 See <A HREF="#Clustering">Clustering</A> for more information.
607 <P>
608 </LI>
609
610 <LI><B>write memory</B><BR>
611 This will write the current running configuration to the config file
612 <B>startup-config</B>, which will be run on a restart.
613 <P>
614 </LI>
615
616 <LI><B>snoop</B><BR>
617 You must specify a username, IP address and port. All packets for the
618 current session for that username will be forwarded to the given
619 host/port. Specify <EM>no snoop username</EM> to disable interception
620 for the session.<P>
621
622 If you want interception to be permanent, you will have to modify the RADIUS
623 response for the user. See <A HREF="#Interception">Interception</A>.
624 <P>
625 </LI>
626
627 <LI><B>throttle</B><BR>
628 You must specify a username, which will be throttled for the current
629 session. Specify <EM>no throttle username</EM> to disable throttling
630 for the current session.<P>
631
632 If you want throttling to be permanent, you will have to modify the
633 RADIUS response for the user. See <A HREF="#Throttling">Throttling</A>.
634 <P>
635 </LI>
636
637 <LI><B>drop session</B><BR>
638 This will cleanly disconnect a session. You must specify a session id, which
639 you can get from <EM>show session</EM>. This will send a disconnect message
640 to the remote end.
641 <P>
642 </LI>
643
644 <LI><B>drop tunnel</B><BR>
645 This will cleanly disconnect a tunnel, as well as all sessions on that
646 tunnel. It will send a disconnect message for each session individually, and
647 after 10 seconds it will send a tunnel disconnect message.
648 <P>
649 </LI>
650
651 <LI><B>uptime</B><BR>
652 This will show how long the l2tpns process has been running, and the current
653 bandwidth utilization:
654 <PRE>
655 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
656 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
657 </PRE>
658 The bandwidth line contains 4 sets of values.<BR>
659 UDP-ETH is the current bandwidth going from the LAC to the ethernet
660 (user uploads), in mbits/sec.<BR>
661 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
662 downloads).<BR>
663 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
664 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
665 <P>
666 These counters are updated every second.
667 <P>
668 </LI>
669
670 <LI><B>configure terminal</B><BR>
671 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
672 The following commands are valid in this mode:<P>
673 </LI>
674
675 <LI><B>load plugin</B><BR>
676 Load a plugin. You must specify the plugin name, and it will search in
677 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
678 <EM>remove plugin</EM>.
679 <P>
680 </LI>
681
682 <LI><B>set</B><BR>
683 Set a configuration variable. You must specify the variable name, and
684 the value. If the value contains any spaces, you should quote the
685 value with double (") or single (') quotes.<P>
686
687 You can set any <A HREF="#startup-config">startup-config</A> value in
688 this way, although some may require a restart to take effect.<P>
689 </LI>
690 </UL>
691
692 <H3 ID="nsctl">nsctl</H3>
693
694 nsctl allows messages to be passed to plugins.<P>
695
696 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
697 <STRONG>nsctl</STRONG>(8) for more details.<P>
698
699 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
700 <EM>help</EM>. Any other commands are passed to plugins for processing.
701
702 <H3 ID="Signals">Signals</H3>
703
704 While the process is running, you can send it a few different signals, using
705 the kill command.
706 <PRE>
707 killall -HUP l2tpns
708 </PRE>
709
710 The signals understood are:
711 <DL>
712 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
713 <DT>SIGTERM, SIGINT</DT><DD>Stop process. Tunnels and sessions are not
714 terminated. This signal should be used to stop l2tpns on a
715 <A HREF="#Clustering">cluster node</A> where there are other machines to
716 continue handling traffic.</DD>
717 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
718 complete.</DD>
719 </DL>
720
721 <H2 ID="Throttling">Throttling</H2>
722
723 l2tpns contains support for slowing down user sessions to whatever speed you
724 desire. You must first enable the global setting <EM>throttle_speed</EM>
725 before this will be activated.<P>
726
727 If you wish a session to be throttled permanently, you should set the
728 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
729 will be handled by the <EM>autothrottle</EM> module.<P>
730
731 Otherwise, you can enable and disable throttling an active session using
732 the <EM>throttle</EM> CLI command.<P>
733
734 <H2 ID="Interception">Interception</H2>
735
736 You may have to deal with legal requirements to be able to intercept a
737 user's traffic at any time. l2tpns allows you to begin and end interception
738 on the fly, as well as at authentication time.<P>
739
740 When a user is being intercepted, a copy of every packet they send and
741 receive will be sent wrapped in a UDP packet to the IP address and port set
742 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
743 variables.<P>
744
745 The UDP packet contains just the raw IP frame, with no extra headers.<P>
746
747 To enable interception on a connected user, use the <EM>snoop username</EM>
748 and <EM>no snoop username</EM> CLI commands. These will enable interception
749 immediately.<P>
750
751 If you wish the user to be intercepted whenever they reconnect, you will
752 need to modify the RADIUS response to include the Vendor-Specific value
753 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
754 you need to have the <EM>autosnoop</EM> module loaded.<P>
755
756 <H2 ID="Authentication">Authentication</H2>
757
758 Whenever a session connects, it is not fully set up until authentication is
759 completed. The remote end must send a PPP CHAP or PPP PAP authentication
760 request to l2tpns.<P>
761
762 This request is sent to the RADIUS server, which will hopefully respond with
763 Auth-Accept or Auth-Reject.<P>
764
765 If Auth-Accept is received, the session is set up and an IP address is
766 assigned. The RADIUS server can include a Framed-IP-Address field in the
767 reply, and that address will be assigned to the client. It can also include
768 specific DNS servers, and a Framed-Route if that is required.<P>
769
770 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
771 at which point they should disconnect. The exception to this is when the
772 walled garden module is loaded, in which case the user still receives the
773 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
774 should not receive any service.<P>
775
776 The RADIUS reply can also contain a Vendor-Specific attribute called
777 Cisco-Avpair. This field is a freeform text field that most Cisco
778 devices understand to contain configuration instructions for the session. In
779 the case of l2tpns it is expected to be of the form
780 <PRE>
781 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
782 </PRE>
783
784 Each key-value pair is separated and passed to any modules loaded. The
785 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
786 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
787 a user who is to be throttled and intercepted, the Cisco-Avpair value should
788 contain:
789 <PRE>
790 intercept=yes,throttle=yes
791 </PRE>
792
793 <H2 ID="Plugins">Plugins</H2>
794
795 So as to make l2tpns as flexible as possible (I know the core code is pretty
796 difficult to understand), it includes a plugin API, which you can use to
797 hook into certain events.<P>
798
799 There are a few example modules included - autosnoop, autothrottle and
800 garden.<P>
801
802 When an event happens that has a hook, l2tpns looks for a predefined
803 function name in every loaded module, and runs them in the order the modules
804 were loaded.<P>
805
806 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
807 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
808 modules should be run for this event.<P>
809 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
810 no further processing should be done for this event. <EM>Use this with care.</EM>
811
812 Every event function called takes a specific structure named
813 param_<EM>event</EM>, which varies in content with each event. The
814 function name for each event will be <B>plugin_<EM>event</EM></B>,
815 so for the event <EM>timer</EM>, the function declaration should look like:
816 <PRE>
817 int plugin_timer(struct param_timer *data);
818 </PRE>
819
820 A list of the available events follows, with a list of all the fields in the
821 supplied structure:
822 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
823 <TABLE CELLSPACING=1 CELLPADDING=3>
824 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
825 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
826 <TD>This is called after a RADIUS response has been
827 received, but before it has been processed by the
828 code. This will allow you to modify the response in
829 some way.
830 </TD>
831 <TD>
832 <DL>
833 <DT>t<DD>Tunnel
834 <DT>s<DD>Session
835 <DT>username
836 <DT>password
837 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
838 <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
839 </DL>
840 </TD>
841 </TR>
842 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
843 <TD>This is called after a RADIUS response has been
844 received, and the basic checks have been performed. This
845 is what the garden module uses to force authentication
846 to be accepted.
847 </TD>
848 <TD>
849 <DL>
850 <DT>t<DD>Tunnel
851 <DT>s<DD>Session
852 <DT>username
853 <DT>auth_allowed<DD>This is already set to true or
854 false depending on whether authentication has been
855 allowed so far. You can set this to 1 or 0 to force
856 allow or disallow authentication
857 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
858 </DL>
859 </TD>
860 </TR>
861 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
862 <TD>This is called whenever a session receives a
863 packet. <FONT COLOR=RED>Use this sparingly, as this will
864 seriously slow down the system.</FONT>
865 </TD>
866 <TD>
867 <DL>
868 <DT>t<DD>Tunnel
869 <DT>s<DD>Session
870 <DT>buf<DD>The raw packet data
871 <DT>len<DD>The length of buf
872 </DL>
873 </TD>
874 </TR>
875 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
876 <TD>This is called whenever a session sends a
877 packet. <FONT COLOR=RED>Use this sparingly, as this will
878 seriously slow down the system.</FONT>
879 </TD>
880 <TD>
881 <DL>
882 <DT>t<DD>Tunnel
883 <DT>s<DD>Session
884 <DT>buf<DD>The raw packet data
885 <DT>len<DD>The length of buf
886 </DL>
887 </TD>
888 </TR>
889 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
890 <TD>This is run every second, no matter what is happening.
891 This is called from a signal handler, so make sure anything
892 you do is reentrant.
893 </TD>
894 <TD>
895 <DL>
896 <DT>time_now<DD>The current unix timestamp
897 </DL>
898 </TD>
899 </TR>
900 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
901 <TD>This is called after a session is fully set up. The
902 session is now ready to handle traffic.
903 </TD>
904 <TD>
905 <DL>
906 <DT>t<DD>Tunnel
907 <DT>s<DD>Session
908 </DL>
909 </TD>
910 </TR>
911 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
912 <TD>This is called when a session is about to be shut down.
913 This may be called multiple times for the same session.
914 </TD>
915 <TD>
916 <DL>
917 <DT>t<DD>Tunnel
918 <DT>s<DD>Session
919 </DL>
920 </TD>
921 </TR>
922 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
923 <TD>This is called whenever a RADIUS response includes a
924 Cisco-Avpair value. The value is split up into
925 <EM>key=value</EM> pairs, and each is processed through all
926 modules.
927 </TD>
928 <TD>
929 <DL>
930 <DT>t<DD>Tunnel
931 <DT>s<DD>Session
932 <DT>key
933 <DT>value
934 </DL>
935 </TD>
936 </TR>
937 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
938 <TD>This is called whenever a RADIUS CoA request is
939 received to reset any options to default values before
940 the new values are applied.
941 </TD>
942 <TD>
943 <DL>
944 <DT>t<DD>Tunnel
945 <DT>s<DD>Session
946 </DL>
947 </TD>
948 </TR>
949 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
950 <TD>This is called in whenever a nsctl packet is received.
951 This should handle the packet and form a response if
952 required.
953 </TD>
954 <TD>
955 <DL>
956 <DT>iam_master<DD>Cluster master status
957 <DT>argc<DD>The number of arguments
958 <DT>argv<DD>Arguments
959 <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
960 <DT>additional<DD>Extended response text
961 </DL>
962 </TD>
963 </TR>
964 </TABLE>
965 </TD></TR></TABLE>
966
967 <H2 ID="WalledGarden">Walled Garden</H2>
968
969 Walled Garden is implemented so that you can provide perhaps limited service
970 to sessions that incorrectly authenticate.<P>
971
972 Whenever a session provides incorrect authentication, and the
973 RADIUS server responds with Auth-Reject, the walled garden module
974 (if loaded) will force authentication to succeed, but set the flag
975 <EM>garden</EM> in the session structure, and adds an iptables rule to
976 the <B>garden_users</B> chain to force all packets for the session's IP
977 address to traverse the <B>garden</B> chain.<P>
978
979 This doesn't <EM>just work</EM>. To set this all up, you will to
980 setup the <B>garden</B> nat table with the
981 <A HREF="#build-garden">build-garden</A> script with rules to limit
982 user's traffic. For example, to force all traffic except DNS to be
983 forwarded to 192.168.1.1, add these entries to your
984 <EM>build-garden</EM>:
985 <PRE>
986 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
987 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
988 </PRE>
989
990 l2tpns will add entries to the garden_users chain as appropriate.<P>
991
992 You can check the amount of traffic being captured using the following
993 command:
994 <PRE>
995 iptables -t nat -L garden -nvx
996 </PRE>
997
998 <H2 ID="Filtering">Filtering</H2>
999
1000 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1001 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
1002 access-list <I>filter</I> should be applied to traffic from the
1003 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1004 customer.
1005
1006 <H2 ID="Clustering">Clustering</H2>
1007
1008 An l2tpns cluster consists of of one* or more servers configured with
1009 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1010
1011 *A stand-alone server is simply a degraded cluster.<P>
1012
1013 Initially servers come up as cluster slaves, and periodically (every
1014 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1015 containing the start time of the process to the multicast
1016 <B>cluster_address</B>.<P>
1017
1018 A cluster master sends heartbeat rather than ping packets, which
1019 contain those session and tunnel changes since the last heartbeat.<P>
1020
1021 When a slave has not seen a heartbeat within
1022 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1023 examining the list of peers it has seen pings from and determines
1024 which of these and itself is the "best" candidate to be master.
1025 "Best" in this context means the server with the highest uptime (the
1026 highest IP address is used as a tie-breaker in the case of equal
1027 uptimes).<P>
1028
1029 After discovering a master, and determining that it is up-to-date (has
1030 seen an update for all in-use sessions and tunnels from heartbeat
1031 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1032 the <B>bind_address</B> and for all addresses/networks in
1033 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1034 the session state, as well as packets for throttled or gardened
1035 sessions are forwarded to the master for handling. In addition, byte
1036 counters for session traffic are periodically forwarded.<P>
1037
1038 A master, when determining that it has at least one up-to-date slave
1039 will drop all routes (raising them again if all slaves disappear) and
1040 subsequently handle only packets forwarded to it by the slaves.<P>
1041
1042 <H2 ID="Routing">Routing</H2>
1043 If you are running a single instance, you may simply statically route
1044 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1045 arp).<P>
1046
1047 For a cluster, configure the members as BGP neighbours on your router
1048 and configure multi-path load-balancing. Cisco uses "maximum-paths
1049 ibgp" for IBGP. If this is not supported by your IOS revision, you
1050 can use "maximum-paths" (which works for EBGP) and set
1051 <B>as_number</B> to a private value such as 64512.<P>
1052
1053 <H2 ID="AvoidingFragmentation">Avoiding Fragmentation</H2>
1054
1055 Fragmentation of encapsulated return packets to the LAC may be avoided
1056 for TCP sessions by adding a firewall rule to clamps the MSS on
1057 outgoing SYN packets.
1058
1059 The following is appropriate for interfaces with a typical MTU of
1060 1500:
1061
1062 <pre>
1063 iptables -A FORWARD -i tun+ -o eth0 \
1064 -p tcp --tcp-flags SYN,RST SYN \
1065 -m tcpmss --mss 1413:1600 \
1066 -j TCPMSS --set-mss 1412
1067 </pre>
1068
1069 <H2 ID="Performance">Performance</H2>
1070
1071 Performance is great.<P>
1072
1073 I'd like to include some pretty graphs here that show a linear performance
1074 increase, with no impact by number of connected sessions.<P>
1075
1076 That's really what it looks like.<P>
1077
1078 <BR>
1079 David Parrish<BR>
1080 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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