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