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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_mcast_ttl</B> (int)<BR>
339 TTL for multicast packets (default: 1).
340 </LI>
341
342 <LI><B>cluster_hb_interval</B> (int)<BR>
343 Interval in tenths of a second between cluster heartbeat/pings.
344 </LI>
345
346 <LI><B>cluster_hb_timeout</B> (int)<BR>
347 Cluster heartbeat timeout in tenths of a second. A new master will be
348 elected when this interval has been passed without seeing a heartbeat
349 from the master.
350 </LI>
351
352 <LI><B>cluster_master_min_adv</B> (int)<BR>
353 Determines the minumum number of up to date slaves required before the
354 master will drop routes (default: 1).
355 </LI>
356 </UL>
357
358 <P>BGP routing configuration is entered by the command:
359 The routing configuration section is entered by the command
360 <DL><DD><B>router bgp</B> <I>as</I></DL>
361 where <I>as</I> specifies the local AS number.
362
363 <P>Subsequent lines prefixed with
364 <DL><DD><B>neighbour</B> <I>peer</I></DL>
365 define the attributes of BGP neighhbours. Valid commands are:
366 <DL>
367 <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
368 <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
369 </DL>
370
371 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
372 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
373 <I>hold</I> are the timer values in seconds.
374
375 <P>Named access-lists are configured using one of the commands:
376 <DL>
377 <DD><B>ip access-list standard</B> <I>name</I>
378 <DD><B>ip access-list extended</B> <I>name</I>
379 </DL>
380
381 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
382 define the body of the access-list. Standard access-list syntax:
383 <DL>
384 <DD>{<B>permit</B>|<B>deny</B>}
385 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
386 [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
387 </DL>
388
389 Extended access-lists:
390
391 <DIV STYLE="margin-left: 4em; text-indent: -2em">
392 <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
393 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
394 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
395 <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
396 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
397 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
398 {<I>host</I>|<I>destination destination-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 [<B>fragments</B>]
401 <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
402 {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
403 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
404 {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
405 [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
406 [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
407 {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
408 ...|<B>fragments</B>]
409 </DIV>
410
411 <H3 ID="users">users</H3>
412
413 Usernames and passwords for the command-line interface are stored in
414 this file. The format is <I>username</I><B>:</B><I>password</I> where
415 <I>password</I> may either by plain text, an MD5 digest (prefixed by
416 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
417 plain text by the prefix <B>{crypt}</B>.<P>
418
419 The username <B>enable</B> has a special meaning and is used to set
420 the enable password.<P>
421
422 <B>Note:</B> If this file doesn't exist, then anyone who can get to
423 port 23 will be allowed access without a username / password.<P>
424
425 <H3 ID="ip-pool">ip_pool</H3>
426
427 This file is used to configure the IP address pool which user
428 addresses are assigned from. This file should contain either an IP
429 address or a CIDR network per line. e.g.:<P>
430
431 <PRE>
432 192.168.1.1
433 192.168.1.2
434 192.168.1.3
435 192.168.4.0/24
436 172.16.0.0/16
437 10.0.0.0/8
438 </PRE>
439
440 Keep in mind that l2tpns can only handle 65535 connections per
441 process, so don't put more than 65535 IP addresses in the
442 configuration file. They will be wasted.
443
444 <H3 ID="build-garden">build-garden</H3>
445
446 The garden plugin on startup creates a NAT table called "garden" then
447 sources the <B>build-garden</B> script to populate that table. All
448 packets from gardened users will be sent through this table. Example:
449
450 <PRE>
451 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
452 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
453 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
454 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
455 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
456 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
457 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
458 iptables -t nat -A garden -p icmp -j ACCEPT
459 iptables -t nat -A garden -j DROP
460 </PRE>
461
462 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
463
464 A running l2tpns process can be controlled in a number of ways. The primary
465 method of control is by the Command-Line Interface (CLI).<P>
466
467 You can also remotely send commands to modules via the nsctl client
468 provided.<P>
469
470 Also, there are a number of signals that l2tpns understands and takes action
471 when it receives them.
472
473 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
474
475 You can access the command line interface by telnet'ing to port 23.
476 There is no IP address restriction, so it's a good idea to firewall
477 this port off from anyone who doesn't need access to it. See
478 <A HREF="#users">users</A> for information on restricting access based
479 on a username and password.<P>
480
481 The CLI gives you real-time control over almost everything in
482 the process. The interface is designed to look like a Cisco
483 device, and supports things like command history, line editing and
484 context sensitive help. This is provided by linking with the
485 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
486 library. Some general documentation of the interface is
487 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
488 here</A>.<P>
489
490 After you have connected to the telnet port (and perhaps logged in), you
491 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
492
493 Enter <EM>help</EM> to get a list of possible commands. A brief
494 overview of the more important commands follows:
495
496 <UL>
497 <LI><B>show session</B><BR>
498 Without specifying a session ID, this will list all tunnels currently
499 connected. If you specify a session ID, you will be given all
500 information on a single tunnel. Note that the full session list can
501 be around 185 columns wide, so you should probably use a wide terminal
502 to see the list properly.<P>
503 The columns listed in the overview are:
504 <TABLE>
505 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
506 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
507 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
508 authentication. If this is *, then LCP authentication has not
509 completed.</TD></TR>
510 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
511 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
512 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
513 session is being snooped. See <EM>snoop</EM>.</TD></TR>
514 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
515 currently throttled. See <EM>throttle</EM>.</TD></TR>
516 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
517 trapped in the walled garden. This field is present even if the
518 garden module is not loaded.</TD></TR>
519 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
520 session started</TD></TR>
521 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
522 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
523 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
524 detected on the session</TD></TR>
525 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
526 connected to.</TD></TR>
527 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
528 provided during the session setup. This field is generated by the
529 LAC.</TD></TR>
530 </TABLE>
531 <P>
532 </LI>
533
534 <LI><B>show users</B><BR>
535 With no arguments, display a list of currently connected users. If an
536 argument is given, the session details for the given username are
537 displayed.
538 </LI>
539
540 <LI><B>show tunnel</B><BR>
541 This will show all the open tunnels in a summary, or detail on a single
542 tunnel if you give a tunnel id.<P>
543 The columns listed in the overview are:
544 <TABLE>
545 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
546 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
547 provided by the LAC. This has no relation to DNS, it is just
548 a text field.</TD></TR>
549 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
550 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
551 Opening</TD></TR>
552 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
553 tunnel</TD></TR>
554 </TABLE>
555 <P>
556 </LI>
557
558 <LI><B>show pool</B><BR>
559 Displays the current IP address pool allocation. This will only display
560 addresses that are in use, or are reserved for re-allocation to a
561 disconnected user.<P>
562 If an address is not currently in use, but has been used, then in the User
563 column the username will be shown in square brackets, followed by the time
564 since the address was used:
565 <PRE>
566 IP Address Used Session User
567 192.168.100.6 N [joe.user] 1548s
568 </PRE>
569 <P>
570 </LI>
571
572 <LI><B>show radius</B><BR>
573 Show a summary of the in-use RADIUS sessions. This list should not be very
574 long, as RADIUS sessions should be cleaned up as soon as they are used. The
575 columns listed are:
576 <TABLE>
577 <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request. This is
578 sent in the packet to the RADIUS server for identification.</TD></TR>
579 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
580 AUTH, IPCP, START, STOP, NULL.</TD></TR>
581 <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
582 request is associated with</TD></TR>
583 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
584 request, it will retry at this time. This is a unix timestamp.</TD></TR>
585 <TR><TD><B>Try</B></TD><TD>Retry count. The RADIUS request is
586 discarded after 3 retries.</TD></TR>
587 </TABLE>
588 <P>
589 </LI>
590
591 <LI><B>show running-config</B><BR>
592 This will list the current running configuration. This is in a format that
593 can either be pasted into the configuration file, or run directly at the
594 command line.
595 <P>
596 </LI>
597
598 <LI><B>show counters</B><BR>
599 Internally, counters are kept of key values, such as bytes and packets
600 transferred, as well as function call counters. This function displays all
601 these counters, and is probably only useful for debugging.<P>
602 You can reset these counters by running <EM>clear counters</EM>.
603 <P>
604 </LI>
605
606 <LI><B>show cluster</B><BR>
607 Show cluster status. Shows the cluster state for this server
608 (Master/Slave), information about known peers and (for slaves) the
609 master IP address, last packet seen and up-to-date status.<P>
610 See <A HREF="#Clustering">Clustering</A> for more information.
611 <P>
612 </LI>
613
614 <LI><B>write memory</B><BR>
615 This will write the current running configuration to the config file
616 <B>startup-config</B>, which will be run on a restart.
617 <P>
618 </LI>
619
620 <LI><B>snoop</B><BR>
621 You must specify a username, IP address and port. All packets for the
622 current session for that username will be forwarded to the given
623 host/port. Specify <EM>no snoop username</EM> to disable interception
624 for the session.<P>
625
626 If you want interception to be permanent, you will have to modify the RADIUS
627 response for the user. See <A HREF="#Interception">Interception</A>.
628 <P>
629 </LI>
630
631 <LI><B>throttle</B><BR>
632 You must specify a username, which will be throttled for the current
633 session. Specify <EM>no throttle username</EM> to disable throttling
634 for the current session.<P>
635
636 If you want throttling to be permanent, you will have to modify the
637 RADIUS response for the user. See <A HREF="#Throttling">Throttling</A>.
638 <P>
639 </LI>
640
641 <LI><B>drop session</B><BR>
642 This will cleanly disconnect a session. You must specify a session id, which
643 you can get from <EM>show session</EM>. This will send a disconnect message
644 to the remote end.
645 <P>
646 </LI>
647
648 <LI><B>drop tunnel</B><BR>
649 This will cleanly disconnect a tunnel, as well as all sessions on that
650 tunnel. It will send a disconnect message for each session individually, and
651 after 10 seconds it will send a tunnel disconnect message.
652 <P>
653 </LI>
654
655 <LI><B>uptime</B><BR>
656 This will show how long the l2tpns process has been running, and the current
657 bandwidth utilization:
658 <PRE>
659 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
660 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
661 </PRE>
662 The bandwidth line contains 4 sets of values.<BR>
663 UDP-ETH is the current bandwidth going from the LAC to the ethernet
664 (user uploads), in mbits/sec.<BR>
665 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
666 downloads).<BR>
667 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
668 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
669 <P>
670 These counters are updated every second.
671 <P>
672 </LI>
673
674 <LI><B>configure terminal</B><BR>
675 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
676 The following commands are valid in this mode:<P>
677 </LI>
678
679 <LI><B>load plugin</B><BR>
680 Load a plugin. You must specify the plugin name, and it will search in
681 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
682 <EM>remove plugin</EM>.
683 <P>
684 </LI>
685
686 <LI><B>set</B><BR>
687 Set a configuration variable. You must specify the variable name, and
688 the value. If the value contains any spaces, you should quote the
689 value with double (") or single (') quotes.<P>
690
691 You can set any <A HREF="#startup-config">startup-config</A> value in
692 this way, although some may require a restart to take effect.<P>
693 </LI>
694 </UL>
695
696 <H3 ID="nsctl">nsctl</H3>
697
698 nsctl allows messages to be passed to plugins.<P>
699
700 Arguments are <EM>command</EM> and optional <EM>args</EM>. See
701 <STRONG>nsctl</STRONG>(8) for more details.<P>
702
703 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
704 <EM>help</EM>. Any other commands are passed to plugins for processing.
705
706 <H3 ID="Signals">Signals</H3>
707
708 While the process is running, you can send it a few different signals, using
709 the kill command.
710 <PRE>
711 killall -HUP l2tpns
712 </PRE>
713
714 The signals understood are:
715 <DL>
716 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
717 <DT>SIGTERM, SIGINT</DT><DD>Stop process. Tunnels and sessions are not
718 terminated. This signal should be used to stop l2tpns on a
719 <A HREF="#Clustering">cluster node</A> where there are other machines to
720 continue handling traffic.</DD>
721 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
722 complete.</DD>
723 </DL>
724
725 <H2 ID="Throttling">Throttling</H2>
726
727 l2tpns contains support for slowing down user sessions to whatever speed you
728 desire. You must first enable the global setting <EM>throttle_speed</EM>
729 before this will be activated.<P>
730
731 If you wish a session to be throttled permanently, you should set the
732 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
733 will be handled by the <EM>autothrottle</EM> module.<P>
734
735 Otherwise, you can enable and disable throttling an active session using
736 the <EM>throttle</EM> CLI command.<P>
737
738 <H2 ID="Interception">Interception</H2>
739
740 You may have to deal with legal requirements to be able to intercept a
741 user's traffic at any time. l2tpns allows you to begin and end interception
742 on the fly, as well as at authentication time.<P>
743
744 When a user is being intercepted, a copy of every packet they send and
745 receive will be sent wrapped in a UDP packet to the IP address and port set
746 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
747 variables.<P>
748
749 The UDP packet contains just the raw IP frame, with no extra headers.<P>
750
751 To enable interception on a connected user, use the <EM>snoop username</EM>
752 and <EM>no snoop username</EM> CLI commands. These will enable interception
753 immediately.<P>
754
755 If you wish the user to be intercepted whenever they reconnect, you will
756 need to modify the RADIUS response to include the Vendor-Specific value
757 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
758 you need to have the <EM>autosnoop</EM> module loaded.<P>
759
760 <H2 ID="Authentication">Authentication</H2>
761
762 Whenever a session connects, it is not fully set up until authentication is
763 completed. The remote end must send a PPP CHAP or PPP PAP authentication
764 request to l2tpns.<P>
765
766 This request is sent to the RADIUS server, which will hopefully respond with
767 Auth-Accept or Auth-Reject.<P>
768
769 If Auth-Accept is received, the session is set up and an IP address is
770 assigned. The RADIUS server can include a Framed-IP-Address field in the
771 reply, and that address will be assigned to the client. It can also include
772 specific DNS servers, and a Framed-Route if that is required.<P>
773
774 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
775 at which point they should disconnect. The exception to this is when the
776 walled garden module is loaded, in which case the user still receives the
777 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
778 should not receive any service.<P>
779
780 The RADIUS reply can also contain a Vendor-Specific attribute called
781 Cisco-Avpair. This field is a freeform text field that most Cisco
782 devices understand to contain configuration instructions for the session. In
783 the case of l2tpns it is expected to be of the form
784 <PRE>
785 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
786 </PRE>
787
788 Each key-value pair is separated and passed to any modules loaded. The
789 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
790 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
791 a user who is to be throttled and intercepted, the Cisco-Avpair value should
792 contain:
793 <PRE>
794 intercept=yes,throttle=yes
795 </PRE>
796
797 <H2 ID="Plugins">Plugins</H2>
798
799 So as to make l2tpns as flexible as possible (I know the core code is pretty
800 difficult to understand), it includes a plugin API, which you can use to
801 hook into certain events.<P>
802
803 There are a few example modules included - autosnoop, autothrottle and
804 garden.<P>
805
806 When an event happens that has a hook, l2tpns looks for a predefined
807 function name in every loaded module, and runs them in the order the modules
808 were loaded.<P>
809
810 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
811 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
812 modules should be run for this event.<P>
813 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
814 no further processing should be done for this event. <EM>Use this with care.</EM>
815
816 Every event function called takes a specific structure named
817 param_<EM>event</EM>, which varies in content with each event. The
818 function name for each event will be <B>plugin_<EM>event</EM></B>,
819 so for the event <EM>timer</EM>, the function declaration should look like:
820 <PRE>
821 int plugin_timer(struct param_timer *data);
822 </PRE>
823
824 A list of the available events follows, with a list of all the fields in the
825 supplied structure:
826 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
827 <TABLE CELLSPACING=1 CELLPADDING=3>
828 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
829 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
830 <TD>This is called after a RADIUS response has been
831 received, but before it has been processed by the
832 code. This will allow you to modify the response in
833 some way.
834 </TD>
835 <TD>
836 <DL>
837 <DT>t<DD>Tunnel
838 <DT>s<DD>Session
839 <DT>username
840 <DT>password
841 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
842 <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
843 </DL>
844 </TD>
845 </TR>
846 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
847 <TD>This is called after a RADIUS response has been
848 received, and the basic checks have been performed. This
849 is what the garden module uses to force authentication
850 to be accepted.
851 </TD>
852 <TD>
853 <DL>
854 <DT>t<DD>Tunnel
855 <DT>s<DD>Session
856 <DT>username
857 <DT>auth_allowed<DD>This is already set to true or
858 false depending on whether authentication has been
859 allowed so far. You can set this to 1 or 0 to force
860 allow or disallow authentication
861 <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
862 </DL>
863 </TD>
864 </TR>
865 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
866 <TD>This is called whenever a session receives a
867 packet. <FONT COLOR=RED>Use this sparingly, as this will
868 seriously slow down the system.</FONT>
869 </TD>
870 <TD>
871 <DL>
872 <DT>t<DD>Tunnel
873 <DT>s<DD>Session
874 <DT>buf<DD>The raw packet data
875 <DT>len<DD>The length of buf
876 </DL>
877 </TD>
878 </TR>
879 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
880 <TD>This is called whenever a session sends a
881 packet. <FONT COLOR=RED>Use this sparingly, as this will
882 seriously slow down the system.</FONT>
883 </TD>
884 <TD>
885 <DL>
886 <DT>t<DD>Tunnel
887 <DT>s<DD>Session
888 <DT>buf<DD>The raw packet data
889 <DT>len<DD>The length of buf
890 </DL>
891 </TD>
892 </TR>
893 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
894 <TD>This is run every second, no matter what is happening.
895 This is called from a signal handler, so make sure anything
896 you do is reentrant.
897 </TD>
898 <TD>
899 <DL>
900 <DT>time_now<DD>The current unix timestamp
901 </DL>
902 </TD>
903 </TR>
904 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
905 <TD>This is called after a session is fully set up. The
906 session is now ready to handle traffic.
907 </TD>
908 <TD>
909 <DL>
910 <DT>t<DD>Tunnel
911 <DT>s<DD>Session
912 </DL>
913 </TD>
914 </TR>
915 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
916 <TD>This is called when a session is about to be shut down.
917 This may be called multiple times for the same session.
918 </TD>
919 <TD>
920 <DL>
921 <DT>t<DD>Tunnel
922 <DT>s<DD>Session
923 </DL>
924 </TD>
925 </TR>
926 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
927 <TD>This is called whenever a RADIUS response includes a
928 Cisco-Avpair value. The value is split up into
929 <EM>key=value</EM> pairs, and each is processed through all
930 modules.
931 </TD>
932 <TD>
933 <DL>
934 <DT>t<DD>Tunnel
935 <DT>s<DD>Session
936 <DT>key
937 <DT>value
938 </DL>
939 </TD>
940 </TR>
941 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
942 <TD>This is called whenever a RADIUS CoA request is
943 received to reset any options to default values before
944 the new values are applied.
945 </TD>
946 <TD>
947 <DL>
948 <DT>t<DD>Tunnel
949 <DT>s<DD>Session
950 </DL>
951 </TD>
952 </TR>
953 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
954 <TD>This is called in whenever a nsctl packet is received.
955 This should handle the packet and form a response if
956 required.
957 </TD>
958 <TD>
959 <DL>
960 <DT>iam_master<DD>Cluster master status
961 <DT>argc<DD>The number of arguments
962 <DT>argv<DD>Arguments
963 <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
964 <DT>additional<DD>Extended response text
965 </DL>
966 </TD>
967 </TR>
968 </TABLE>
969 </TD></TR></TABLE>
970
971 <H2 ID="WalledGarden">Walled Garden</H2>
972
973 Walled Garden is implemented so that you can provide perhaps limited service
974 to sessions that incorrectly authenticate.<P>
975
976 Whenever a session provides incorrect authentication, and the
977 RADIUS server responds with Auth-Reject, the walled garden module
978 (if loaded) will force authentication to succeed, but set the flag
979 <EM>garden</EM> in the session structure, and adds an iptables rule to
980 the <B>garden_users</B> chain to force all packets for the session's IP
981 address to traverse the <B>garden</B> chain.<P>
982
983 This doesn't <EM>just work</EM>. To set this all up, you will to
984 setup the <B>garden</B> nat table with the
985 <A HREF="#build-garden">build-garden</A> script with rules to limit
986 user's traffic. For example, to force all traffic except DNS to be
987 forwarded to 192.168.1.1, add these entries to your
988 <EM>build-garden</EM>:
989 <PRE>
990 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
991 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
992 </PRE>
993
994 l2tpns will add entries to the garden_users chain as appropriate.<P>
995
996 You can check the amount of traffic being captured using the following
997 command:
998 <PRE>
999 iptables -t nat -L garden -nvx
1000 </PRE>
1001
1002 <H2 ID="Filtering">Filtering</H2>
1003
1004 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1005 the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
1006 access-list <I>filter</I> should be applied to traffic from the
1007 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1008 customer.
1009
1010 <H2 ID="Clustering">Clustering</H2>
1011
1012 An l2tpns cluster consists of of one* or more servers configured with
1013 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1014
1015 *A stand-alone server is simply a degraded cluster.<P>
1016
1017 Initially servers come up as cluster slaves, and periodically (every
1018 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1019 containing the start time of the process to the multicast
1020 <B>cluster_address</B>.<P>
1021
1022 A cluster master sends heartbeat rather than ping packets, which
1023 contain those session and tunnel changes since the last heartbeat.<P>
1024
1025 When a slave has not seen a heartbeat within
1026 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1027 examining the list of peers it has seen pings from and determines
1028 which of these and itself is the "best" candidate to be master.
1029 "Best" in this context means the server with the highest uptime (the
1030 highest IP address is used as a tie-breaker in the case of equal
1031 uptimes).<P>
1032
1033 After discovering a master, and determining that it is up-to-date (has
1034 seen an update for all in-use sessions and tunnels from heartbeat
1035 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1036 the <B>bind_address</B> and for all addresses/networks in
1037 <B>ip_pool</B>. Any packets recieved by the slave which would alter
1038 the session state, as well as packets for throttled or gardened
1039 sessions are forwarded to the master for handling. In addition, byte
1040 counters for session traffic are periodically forwarded.<P>
1041
1042 A master, when determining that it has at least one up-to-date slave
1043 will drop all routes (raising them again if all slaves disappear) and
1044 subsequently handle only packets forwarded to it by the slaves.<P>
1045
1046 <H2 ID="Routing">Routing</H2>
1047 If you are running a single instance, you may simply statically route
1048 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1049 arp).<P>
1050
1051 For a cluster, configure the members as BGP neighbours on your router
1052 and configure multi-path load-balancing. Cisco uses "maximum-paths
1053 ibgp" for IBGP. If this is not supported by your IOS revision, you
1054 can use "maximum-paths" (which works for EBGP) and set
1055 <B>as_number</B> to a private value such as 64512.<P>
1056
1057 <H2 ID="AvoidingFragmentation">Avoiding Fragmentation</H2>
1058
1059 Fragmentation of encapsulated return packets to the LAC may be avoided
1060 for TCP sessions by adding a firewall rule to clamps the MSS on
1061 outgoing SYN packets.
1062
1063 The following is appropriate for interfaces with a typical MTU of
1064 1500:
1065
1066 <pre>
1067 iptables -A FORWARD -i tun+ -o eth0 \
1068 -p tcp --tcp-flags SYN,RST SYN \
1069 -m tcpmss --mss 1413:1600 \
1070 -j TCPMSS --set-mss 1412
1071 </pre>
1072
1073 <H2 ID="Performance">Performance</H2>
1074
1075 Performance is great.<P>
1076
1077 I'd like to include some pretty graphs here that show a linear performance
1078 increase, with no impact by number of connected sessions.<P>
1079
1080 That's really what it looks like.<P>
1081
1082 <BR>
1083 David Parrish<BR>
1084 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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