add length checks and comments to proxy LCP parsing
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25 <H1>L2TPNS Manual</H1>
26 <OL>
27 <LI><A HREF="#Overview">Overview</A></LI>
28 <LI><A HREF="#Installation">Installation</A>
29 <OL>
30 <LI><A HREF="#Requirements">Requirements</A></LI>
31 <LI><A HREF="#Compile">Compile</A></LI>
32 <LI><A HREF="#Install">Install</A></LI>
33 <LI><A HREF="#Running">Running</A></LI>
34 </OL>
35 </LI>
36 <LI><A HREF="#Configuration">Configuration</A>
37 <OL>
38 <LI><A HREF="#startup-config">startup-config</A></LI>
39 <LI><A HREF="#users">users</A></LI>
40 <LI><A HREF="#ip-pool">ip_pool</A></LI>
41 <LI><A HREF="#build-garden">build-garden</A></LI>
42 </OL>
43 </LI>
44 <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
45 <OL>
46 <LI><A HREF="#Command-LineInterface">Command-Line Interface</A></LI>
47 <LI><A HREF="#nsctl">nsctl</A></LI>
48 <LI><A HREF="#Signals">Signals</A></LI>
49 </OL>
50 </LI>
51 <LI><A HREF="#Throttling">Throttling</A></LI>
52 <LI><A HREF="#Interception">Interception</A></LI>
53 <LI><A HREF="#Authentication">Authentication</A></LI>
54 <LI><A HREF="#Plugins">Plugins</A></LI>
55 <LI><A HREF="#Walled Garden">Walled Garden</A></LI>
56 <LI><A HREF="#Clustering">Clustering</A></LI>
57 <LI><A HREF="#Routing">Routing</A></LI>
58 <LI><A HREF="#Performance">Performance</A></LI>
59 </OL>
60
61 <H2 ID="Overview">Overview</H2>
62 l2tpns is half of a complete L2TP implementation. It supports only the
63 LNS side of the connection.<P>
64
65 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
66 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns
67 implements PPP over L2TP only.<P>
68
69 There are a couple of other L2TP imlementations, of which <A
70 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
71 most popular. l2tpd also will handle being either end of a tunnel, and
72 is a lot more configurable than l2tpns. However, due to the way it works,
73 it is nowhere near as scalable.<P>
74
75 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
76 and send packets. Using some packet manipulation it doesn't require a
77 single interface per connection, as l2tpd does.<P>
78
79 This allows it to scale extremely well to very high loads and very high
80 numbers of connections.<P>
81
82 It also has a plugin architecture which allows custom code to be run
83 during processing. An example of this is in the walled garden module
84 included.<P>
85
86 <BR>
87 <EM>Documentation is not my best skill. If you find any problems
88 with this document, or if you wish to contribute, please email <A
89 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
90
91 <H2 ID="Installation">Installation</H2>
92 <H3 ID="Requirements">Requirements</H3>
93
94 <OL>
95 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
96 compiled in, or as a module.</LI>
97
98 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
99 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
100 </OL>
101
102 <H3 ID="Compile">Compile</H3>
103
104 You can generally get away with just running <B>make</B> from the source
105 directory. This will compile the daemon, associated tools and any modules
106 shipped with the distribution.<P>
107
108 <H3 ID="Install">Install</H3>
109
110 After you have successfully compiled everything, run <B>make
111 install</B> to install it. By default, the binaries are installed into
112 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
113 modules into <EM>/usr/lib/l2tpns</EM>.<P>
114
115 You will definately need to edit the configuration files before you
116 start. See the <A HREF="#Configuration">Configuration</A> section for
117 more information.<P>
118
119 <H3 ID="Running">Running</H3>
120
121 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it. It does
122 not detach to a daemon process, so you should perhaps run it from init.<P>
123
124 By default there is no log destination set, so all log messages will go to
125 stdout.<P>
126
127 <H2 ID="Configuration">Configuration</H2>
128
129 All configuration of the software is done from the files installed into
130 /etc/l2tpns.
131
132 <H3 ID="startup-config">startup-config</H3>
133
134 This is the main configuration file for l2tpns. The format of the file is a
135 list of commands that can be run through the command-line interface. This
136 file can also be written directly by the l2tpns process if a user runs the
137 <EM>write memory</EM> command, so any comments will be lost. However if your
138 policy is not to write the config by the program, then feel free to comment
139 the file with a # or ! at the beginning of the line.<P>
140
141 A list of the possible configuration directives follows. Each of these
142 should be set by a line like:<P>
143 <PRE>
144 set configstring "value"
145 set ipaddress 192.168.1.1
146 set boolean true
147 </PRE>
148
149 <UL>
150 <LI><B>debug</B> (int)<BR>
151 Sets the level of messages that will be written to the log file. The value
152 should be between 0 and 5, with 0 being no debugging, and 5 being the
153 highest. A rough description of the levels is:
154 <OL>
155 <LI VALUE=0>Critical Errors - Things are probably broken</LI>
156 <LI>Errors - Things might have gone wrong, but probably will recover</LI>
157 <LI>Warnings - Just in case you care what is not quite perfect</LI>
158 <LI>Information - Parameters of control packets</LI>
159 <LI>Calls - For tracing the execution of the code</LI>
160 <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
161 </OL><P>
162 Note that the higher you set the debugging level, the slower the program
163 will run. Also, at level 5 a LOT of information will be logged. This should
164 only ever be used for working out why it doesn't work at all.
165 <P>
166 </LI>
167
168 <LI><B>log_file</B> (string)<BR>
169 This will be where all logging and debugging information is written
170 to. This can be either a filename, such as <EM>/var/log/l2tpns</EM>, or
171 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
172 is any one of the syslog logging facilities, such as local5.
173 <P>
174 </LI>
175
176 <LI><B>pid_file</B> (string)<BR>
177 If this is set, the process id will be written to this file. The filename must
178 contain an absolute path.
179 <P>
180 </LI>
181
182 <LI><B>l2tp_secret</B> (string)<BR>
183 This sets the string that l2tpns will use for authenticating tunnel request.
184 This must be the same as the LAC, or authentication will fail. This will
185 only actually be used if the LAC requests authentication.
186 <P>
187 </LI>
188
189 <LI><B>primary_dns</B> (ip address)
190 <LI><B>secondary_dns</B> (ip address)<BR>
191 Whenever a PPP connection is established, DNS servers will be sent to the
192 user, both a primary and a secondary. If either is set to 0.0.0.0, then that
193 one will not be sent.
194 <P>
195 </LI>
196
197 <LI><B>save_state</B> (boolean)<BR>
198 When l2tpns receives a STGTERM it will write out its current
199 ip_address_pool, session and tunnel tables to disk prior to exiting to
200 be re-loaded at startup. The validity of this data is obviously quite
201 short and the intent is to allow an sessions to be retained over a
202 software upgrade.
203 <P>
204 </LI>
205
206 <LI><B>primary_radius</B> (ip address)
207 <LI><B>secondary_radius</B> (ip address)<BR>
208 This sets the radius servers used for both authentication and
209 accounting. If the primary server does not respond, then the
210 secondary radius server will be tried.
211 <P>
212 </LI>
213
214 <LI><B>primary_radius_port</B> (short)
215 <LI><B>secondary_radius_port</B> (short)<BR>
216 This sets the authentication ports for the primary and secondary
217 radius servers. The accounting port is one more than the authentication
218 port. If no radius ports are given, the authentication port defaults to 1645,
219 and the accounting port to 1646.
220 <P>
221 </LI>
222
223 <LI><B>radius_accounting</B> (boolean)<BR>
224 If set to true, then radius accounting packets will be sent. This
225 means that a Start record will be sent when the session is
226 successfully authenticated, and a Stop record will be sent when the
227 session is closed.
228 <P>
229 </LI>
230
231 <LI><B>radius_secret</B> (string)<BR>
232 This secret will be used in all radius queries. If this is not set then
233 radius queries will fail.
234 <P>
235 </LI>
236
237 <LI><B>bind_address</B> (ip address)<BR>
238 When the tun interface is created, it is assigned the address
239 specified here. If no address is given, 1.1.1.1 is used. Packets
240 containing user traffic should be routed via this address if given,
241 otherwise the primary address of the machine.
242 <P>
243 </LI>
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 <P>
251 </LI>
252
253 <LI><B>throttle_speed</B> (int)<BR>
254 Sets the speed (in kbits/s) which sessions will be limited to. If this is
255 set to 0, then throttling will not be used at all. Note: You can set this by
256 the CLI, but changes will not affect currently connected users.
257 <P>
258 </LI>
259
260 <LI><B>throttle_buckets</B> (int)<BR>
261 Number of token buckets to allocate for throttling. Each throttled
262 session requires two buckets (in and out).
263 <P>
264 </LI>
265
266 <LI><B>accounting_dir</B> (string)<BR>
267 If set to a directory, then every 5 minutes the current usage for
268 every connected use will be dumped to a file in this directory. Each
269 file dumped begins with a header, where each line is prefixed by #.
270 Following the header is a single line for every connected user, fields
271 separated by a space.<BR> The fields are username, ip, qos,
272 uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
273 2 if the user is throttled.
274 <P>
275 </LI>
276
277 <LI><B>setuid</B> (int)<BR>
278 After starting up and binding the interface, change UID to this. This
279 doesn't work properly.
280 <P>
281 </LI>
282
283 <LI><B>dump_speed</B> (boolean)<BR>
284 If set to true, then the current bandwidth utilization will be logged every
285 second. Even if this is disabled, you can see this information by running
286 the <EM>uptime</EM> command on the CLI.
287 <P>
288 </LI>
289
290 <LI><B>cleanup_interval</B> (int)<BR>
291 Interval between regular cleanups (in seconds).
292 <P>
293 </LI>
294
295 <LI><B>multi_read_count</B> (int)<BR>
296 Number of packets to read off each of the UDP and TUN fds when
297 returned as readable by select (default: 10). Avoids incurring the
298 unnecessary system call overhead of select on busy servers.
299 <P>
300 </LI>
301
302 <LI><B>scheduler_fifo</B> (boolean)<BR>
303 Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
304 causes the kernel to immediately preempt any currently SCHED_OTHER
305 (normal) process in favour of l2tpns when it becomes runnable.
306 Ignored on uniprocessor systems.
307 <P>
308 </LI>
309
310 <LI><B>lock_pages</B> (boolean)<BR>
311 Keep all pages mapped by the l2tpns process in memory.
312 <P>
313 </LI>
314
315 <LI><B>icmp_rate</B> (int)<BR>
316 Maximum number of host unreachable icmp packets to send per second.
317 <P>
318 </LI>
319
320 <LI><B>cluster_address</B> (ip address)<BR>
321 Multicast cluster address (default: 239.192.13.13). See the section
322 on <A HREF="#Clustering">Clustering</A> for more information.
323 <P>
324 </LI>
325
326 <LI><B>cluster_interface</B> (string)<BR>
327 Interface for cluster packets (default: eth0).
328 <P>
329 </LI>
330
331 <LI><B>cluster_hb_interval</B> (int)<BR>
332 Interval in tenths of a second between cluster heartbeat/pings.
333 <P>
334 </LI>
335
336 <LI><B>cluster_hb_timeout</B> (int)<BR>
337 Cluster heartbeat timeout in tenths of a second. A new master will be
338 elected when this interval has been passed without seeing a heartbeat
339 from the master.
340 <P>
341 </LI>
342
343 <LI><B>as_number</B> (int)<BR>
344 Defines the local AS number for BGP (see <A HREF="#Routing">Routing</A>).
345 <P>
346 </LI>
347
348 <LI><B>bgp_peer1</B> (string)
349 <LI><B>bgp_peer1_as</B> (int)
350 <LI><B>bgp_peer2</B> (string)
351 <LI><B>bgp_peer2_as</B> (int)<BR>
352 <P>
353 DNS name (or IP) and AS number of BGP peers.
354 </LI>
355 </UL>
356
357 <H3 ID="users">users</H3>
358
359 Usernames and passwords for the command-line interface are stored in
360 this file. The format is <I>username</I><B>:</B><I>password</I> where
361 <I>password</I> may either by plain text, an MD5 digest (prefixed by
362 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
363 plain text by the prefix <B>{crypt}</B>.<P>
364
365 The username <B>enable</B> has a special meaning and is used to set
366 the enable password.<P>
367
368 <B>Note:</B> If this file doesn't exist, then anyone who can get to
369 port 23 will be allowed access without a username / password.<P>
370
371 <H3 ID="ip-pool">ip_pool</H3>
372
373 This file is used to configure the IP address pool which user
374 addresses are assigned from. This file should contain either an IP
375 address or a CIDR network per line. e.g.:<P>
376
377 <PRE>
378 192.168.1.1
379 192.168.1.2
380 192.168.1.3
381 192.168.4.0/24
382 172.16.0.0/16
383 10.0.0.0/8
384 </PRE>
385
386 Keep in mind that l2tpns can only handle 65535 connections per
387 process, so don't put more than 65535 IP addresses in the
388 configuration file. They will be wasted.
389
390 <H3 ID="build-garden">build-garden</H3>
391
392 The garden plugin on startup creates a NAT table called "garden" then
393 sources the <B>build-garden</B> script to populate that table. All
394 packets from gardened users will be sent through this table. Example:
395
396 <PRE>
397 iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
398 iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
399 iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
400 iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
401 iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
402 iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
403 iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
404 iptables -t nat -A garden -p icmp -j ACCEPT
405 iptables -t nat -A garden -j DROP
406 </PRE>
407
408 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
409
410 A running l2tpns process can be controlled in a number of ways. The primary
411 method of control is by the Command-Line Interface (CLI).<P>
412
413 You can also remotely send commands to modules via the nsctl client
414 provided. This currently only works with the walled garden module, but
415 modification is trivial to support other modules.<P>
416
417 Also, there are a number of signals that l2tpns understands and takes action
418 when it receives them.
419
420 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
421
422 You can access the command line interface by telnet'ing to port 23.
423 There is no IP address restriction, so it's a good idea to firewall
424 this port off from anyone who doesn't need access to it. See
425 <A HREF="#users">users</A> for information on restricting access based
426 on a username and password.<P>
427
428 The CLI gives you real-time control over almost everything in
429 the process. The interface is designed to look like a Cisco
430 device, and supports things like command history, line editing and
431 context sensitive help. This is provided by linking with the
432 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
433 library. Some general documentation of the interface is
434 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
435 here</A>.<P>
436
437 After you have connected to the telnet port (and perhaps logged in), you
438 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
439
440 Enter <EM>help</EM> to get a list of possible commands. A brief
441 overview of the more important commands follows:
442
443 <UL>
444 <LI><B>show session</B><BR>
445 Without specifying a session ID, this will list all tunnels currently
446 connected. If you specify a session ID, you will be given all
447 information on a single tunnel. Note that the full session list can
448 be around 185 columns wide, so you should probably use a wide terminal
449 to see the list properly.<P>
450 The columns listed in the overview are:
451 <TABLE>
452 <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
453 <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
454 <TR><TD><B>Username</B></TD><TD>The username given in the PPP
455 authentication. If this is *, then LCP authentication has not
456 completed.</TD></TR>
457 <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
458 this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
459 <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
460 session is being snooped. See <EM>snoop</EM>.</TD></TR>
461 <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
462 currently throttled. See <EM>throttle</EM>.</TD></TR>
463 <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
464 trapped in the walled garden. This field is present even if the
465 garden module is not loaded.</TD></TR>
466 <TR><TD><B>opened</B></TD><TD>The number of seconds since the
467 session started</TD></TR>
468 <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
469 <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
470 <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
471 detected on the session</TD></TR>
472 <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
473 connected to.</TD></TR>
474 <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
475 provided during the session setup. This field is generated by the
476 LAC.</TD></TR>
477 </TABLE>
478 <P>
479 </LI>
480
481 <LI><B>show users</B><BR>
482 With no arguments, display a list of currently connected users. If an
483 argument is given, the session details for the given username are
484 displayed.
485 </LI>
486
487 <LI><B>show tunnel</B><BR>
488 This will show all the open tunnels in a summary, or detail on a single
489 tunnel if you give a tunnel id.<P>
490 The columns listed in the overview are:
491 <TABLE>
492 <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
493 <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
494 provided by the LAC. This has no relation to DNS, it is just
495 a text field.</TD></TR>
496 <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
497 <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
498 Opening</TD></TR>
499 <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
500 tunnel</TD></TR>
501 </TABLE>
502 <P>
503 </LI>
504
505 <LI><B>show pool</B><BR>
506 Displays the current IP address pool allocation. This will only display
507 addresses that are in use, or are reserved for re-allocation to a
508 disconnected user.<P>
509 If an address is not currently in use, but has been used, then in the User
510 column the username will be shown in square brackets, followed by the time
511 since the address was used:
512 <PRE>
513 IP Address Used Session User
514 192.168.100.6 N [joe.user] 1548s
515 </PRE>
516 <P>
517 </LI>
518
519 <LI><B>show radius</B><BR>
520 Show a summary of the in-use radius sessions. This list should not be very
521 long, as radius sessions should be cleaned up as soon as they are used. The
522 columns listed are:
523 <TABLE>
524 <TR><TD><B>Radius</B></TD><TD>The ID of the radius request. This is
525 sent in the packet to the radius server for identification.</TD></TR>
526 <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
527 AUTH, IPCP, START, STOP, NULL.</TD></TR>
528 <TR><TD><B>Session</B></TD><TD>The session ID that this radius
529 request is associated with</TD></TR>
530 <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
531 request, it will retry at this time. This is a unix timestamp.</TD></TR>
532 <TR><TD><B>Try</B></TD><TD>Retry count. The radius request is
533 discarded after 3 retries.</TD></TR>
534 </TABLE>
535 <P>
536 </LI>
537
538 <LI><B>show running-config</B><BR>
539 This will list the current running configuration. This is in a format that
540 can either be pasted into the configuration file, or run directly at the
541 command line.
542 <P>
543 </LI>
544
545 <LI><B>show counters</B><BR>
546 Internally, counters are kept of key values, such as bytes and packets
547 transferred, as well as function call counters. This function displays all
548 these counters, and is probably only useful for debugging.<P>
549 You can reset these counters by running <EM>clear counters</EM>.
550 <P>
551 </LI>
552
553 <LI><B>show cluster</B><BR>
554 Show cluster status. Shows the cluster state for this server
555 (Master/Slave), information about known peers and (for slaves) the
556 master IP address, last packet seen and up-to-date status.<P>
557 See <A HREF="#Clustering">Clustering</A> for more information.
558 <P>
559 </LI>
560
561 <LI><B>write memory</B><BR>
562 This will write the current running configuration to the config file
563 <B>startup-config</B>, which will be run on a restart.
564 <P>
565 </LI>
566
567 <LI><B>snoop</B><BR>
568 You must specify a username, IP address and port. All packets for the
569 current session for that username will be forwarded to the given
570 host/port. Specify <EM>no snoop username</EM> to disable interception
571 for the session.<P>
572
573 If you want interception to be permanent, you will have to modify the radius
574 response for the user. See <A HREF="#Interception">Interception</A>.
575 <P>
576 </LI>
577
578 <LI><B>throttle</B><BR>
579 You must specify a username, which will be throttled for the current
580 session. Specify <EM>no throttle username</EM> to disable throttling
581 for the current session.<P>
582
583 If you want throttling to be permanent, you will have to modify the
584 radius response for the user. See <A HREF="#THrottling">Throttling</A>.
585 <P>
586 </LI>
587
588 <LI><B>drop session</B><BR>
589 This will cleanly disconnect a session. You must specify a session id, which
590 you can get from <EM>show session</EM>. This will send a disconnect message
591 to the remote end.
592 <P>
593 </LI>
594
595 <LI><B>drop tunnel</B><BR>
596 This will cleanly disconnect a tunnel, as well as all sessions on that
597 tunnel. It will send a disconnect message for each session individually, and
598 after 10 seconds it will send a tunnel disconnect message.
599 <P>
600 </LI>
601
602 <LI><B>uptime</B><BR>
603 This will show how long the l2tpns process has been running, and the current
604 bandwidth utilization:
605 <PRE>
606 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
607 Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
608 </PRE>
609 The bandwidth line contains 4 sets of values.<BR>
610 UDP-ETH is the current bandwidth going from the LAC to the ethernet
611 (user uploads), in mbits/sec.<BR>
612 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
613 downloads).<BR>
614 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
615 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
616 <P>
617 These counters are updated every second.
618 <P>
619 </LI>
620
621 <LI><B>configure terminal</B><BR>
622 Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
623 The following commands are valid in this mode:<P>
624 </LI>
625
626 <LI><B>load plugin</B><BR>
627 Load a plugin. You must specify the plugin name, and it will search in
628 /usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
629 <EM>remove plugin</EM>.
630 <P>
631 </LI>
632
633 <LI><B>set</B><BR>
634 Set a configuration variable. You must specify the variable name, and
635 the value. If the value contains any spaces, you should quote the
636 value with double (") or single (') quotes.<P>
637
638 You can set any <A HREF="#startup-config">startup-config</A> value in
639 this way, although some may require a restart to take effect.<P>
640 </LI>
641 </UL>
642
643 <H3 ID="nsctl">nsctl</H3>
644
645 nsctl was implemented (badly) to allow messages to be passed to modules.<P>
646
647 You must pass at least 2 parameters: <EM>host</EM> and <EM>command</EM>. The
648 host is the address of the l2tpns server which you want to send the message
649 to.<P>
650
651 Command can currently be either <EM>garden</EM> or <EM>ungarden</EM>. With
652 both of these commands, you must give a session ID as the 3rd parameter.
653 This will activate or deactivate the walled garden for a session
654 temporarily.
655
656 <H3 ID="Signals">Signals</H3>
657
658 While the process is running, you can send it a few different signals, using
659 the kill command.
660 <PRE>
661 killall -HUP l2tpns
662 </PRE>
663
664 The signals understood are:
665 <UL>
666 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
667 <LI>SIGTERM / SIGINT - Shut down for a restart. This will dump the current
668 state to disk (if <EM>save_state</EM> is set to true). Upon restart, the
669 process will read this saved state to resume active sessions.<P>
670 <LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
671 every active session and tunnel before shutting down. This is a good idea
672 when upgrading the code, as no sessions will be left with the remote end
673 thinking they are open.</LI>
674 </UL>
675
676 <H2 ID="Throttling">Throttling</H2>
677
678 l2tpns contains support for slowing down user sessions to whatever speed you
679 desire. You must first enable the global setting <EM>throttle_speed</EM>
680 before this will be activated.<P>
681
682 If you wish a session to be throttled permanently, you should set the
683 Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
684 will be handled by the <EM>autothrottle</EM> module.<P>
685
686 Otherwise, you can enable and disable throttling an active session using
687 the <EM>throttle</EM> CLI command.<P>
688
689 <H2 ID="Interception">Interception</H2>
690
691 You may have to deal with legal requirements to be able to intercept a
692 user's traffic at any time. l2tpns allows you to begin and end interception
693 on the fly, as well as at authentication time.<P>
694
695 When a user is being intercepted, a copy of every packet they send and
696 receive will be sent wrapped in a UDP packet to the IP address and port set
697 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
698 variables.<P>
699
700 The UDP packet contains just the raw IP frame, with no extra headers.<P>
701
702 To enable interception on a connected user, use the <EM>snoop username</EM>
703 and <EM>no snoop username</EM> CLI commands. These will enable interception
704 immediately.<P>
705
706 If you wish the user to be intercepted whenever they reconnect, you will
707 need to modify the radius response to include the Vendor-Specific value
708 <B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
709 you need to have the <EM>autosnoop</EM> module loaded.<P>
710
711 <H2 ID="Authentication">Authentication</H2>
712
713 Whenever a session connects, it is not fully set up until authentication is
714 completed. The remote end must send a PPP CHAP or PPP PAP authentication
715 request to l2tpns.<P>
716
717 This request is sent to the radius server, which will hopefully respond with
718 Auth-Accept or Auth-Reject.<P>
719
720 If Auth-Accept is received, the session is set up and an IP address is
721 assigned. The radius server can include a Framed-IP-Address field in the
722 reply, and that address will be assigned to the client. It can also include
723 specific DNS servers, and a Framed-Route if that is required.<P>
724
725 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
726 at which point they should disconnect. The exception to this is when the
727 walled garden module is loaded, in which case the user still receives the
728 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
729 should not receive any service.<P>
730
731 The radius reply can also contain a Vendor-Specific attribute called
732 Cisco-Avpair. This field is a freeform text field that most Cisco
733 devices understand to contain configuration instructions for the session. In
734 the case of l2tpns it is expected to be of the form
735 <PRE>
736 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
737 </PRE>
738
739 Each key-value pair is separated and passed to any modules loaded. The
740 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
741 <EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
742 a user who is to be throttled and intercepted, the Cisco-Avpair value should
743 contain:
744 <PRE>
745 intercept=yes,throttle=yes
746 </PRE>
747
748 <H2 ID="Plugins">Plugins</H2>
749
750 So as to make l2tpns as flexible as possible (I know the core code is pretty
751 difficult to understand), it includes a plugin API, which you can use to
752 hook into certain events.<P>
753
754 There are a few example modules included - autosnoop, autothrottle and
755 garden.<P>
756
757 When an event happens that has a hook, l2tpns looks for a predefined
758 function name in every loaded module, and runs them in the order the modules
759 were loaded.<P>
760
761 The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
762 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
763 modules should be run for this event.<P>
764 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
765 no further processing should be done for this event. <EM>Use this with care.</EM>
766
767 Every event function called takes a specific structure named
768 param_<EM>event</EM>, which varies in content with each event. The
769 function name for each event will be <B>plugin_<EM>event</EM></B>,
770 so for the event <EM>timer</EM>, the function declaration should look like:
771 <PRE>
772 int plugin_timer(struct param_timer *data);
773 </PRE>
774
775 A list of the available events follows, with a list of all the fields in the
776 supplied structure:
777 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
778 <TABLE CELLSPACING=1 CELLPADDING=3>
779 <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
780 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
781 <TD>This is called after a radius response has been
782 received, but before it has been processed by the
783 code. This will allow you to modify the response in
784 some way.
785 </TD>
786 <TD>
787 <UL>
788 <LI>t - Tunnel ID</LI>
789 <LI>s - Session ID</LI>
790 <LI>username</LI>
791 <LI>password</LI>
792 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
793 <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
794 </UL>
795 </TD>
796 </TR>
797 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
798 <TD>This is called after a radius response has been
799 received, and the basic checks have been performed. This
800 is what the garden module uses to force authentication
801 to be accepted.
802 </TD>
803 <TD>
804 <UL>
805 <LI>t - Tunnel ID</LI>
806 <LI>s - Session ID</LI>
807 <LI>username</LI>
808 <LI>auth_allowed - This is already set to true or
809 false depending on whether authentication has been
810 allowed so far. You can set this to 1 or 0 to force
811 allow or disallow authentication</LI>
812 <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
813 </UL>
814 </TD>
815 </TR>
816 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
817 <TD>This is called whenever a session receives a
818 packet. <FONT COLOR=RED>Use this sparingly, as this will
819 seriously slow down the system.</FONT>
820 </TD>
821 <TD>
822 <UL>
823 <LI>t - Tunnel ID</LI>
824 <LI>s - Session ID</LI>
825 <LI>buf - The raw packet data</LI>
826 <LI>len - The length of buf</LI>
827 </UL>
828 </TD>
829 </TR>
830 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
831 <TD>This is called whenever a session sends a
832 packet. <FONT COLOR=RED>Use this sparingly, as this will
833 seriously slow down the system.</FONT>
834 </TD>
835 <TD>
836 <UL>
837 <LI>t - Tunnel ID</LI>
838 <LI>s - Session ID</LI>
839 <LI>buf - The raw packet data</LI>
840 <LI>len - The length of buf</LI>
841 </UL>
842 </TD>
843 </TR>
844 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
845 <TD>This is run every second, no matter what is happening.
846 This is called from a signal handler, so make sure anything
847 you do is reentrant.
848 </TD>
849 <TD>
850 <UL>
851 <LI>time_now - The current unix timestamp</LI>
852 </UL>
853 </TD>
854 </TR>
855 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
856 <TD>This is called after a session is fully set up. The
857 session is now ready to handle traffic.
858 </TD>
859 <TD>
860 <UL>
861 <LI>t - Tunnel ID</LI>
862 <LI>s - Session ID</LI>
863 </UL>
864 </TD>
865 </TR>
866 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
867 <TD>This is called when a session is about to be shut down.
868 This may be called multiple times for the same session.
869 </TD>
870 <TD>
871 <UL>
872 <LI>t - Tunnel ID</LI>
873 <LI>s - Session ID</LI>
874 </UL>
875 </TD>
876 </TR>
877 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
878 <TD>This is called whenever a radius response includes a
879 Cisco-Avpair value. The value is split up into
880 <EM>key=value</EM> pairs, and each is processed through all
881 modules.
882 </TD>
883 <TD>
884 <UL>
885 <LI>t - Tunnel ID</LI>
886 <LI>s - Session ID</LI>
887 <LI>key</LI>
888 <LI>value</LI>
889 </UL>
890 </TD>
891 </TR>
892 <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
893 <TD>This is called in whenever a nsctl packet is received.
894 This should handle the packet and form a response if
895 required.
896 </TD>
897 <TD>
898 <UL>
899 <LI>buf - The raw packet data</LI>
900 <LI>l - The raw packet data length</LI>
901 <LI>source_ip - Where the request came from</LI>
902 <LI>source_port - Where the request came from</LI>
903 <LI>response - Allocate a buffer and put your response in here</LI>
904 <LI>response_length - Length of response</LI>
905 <LI>send_response - true or false whether a response
906 should be sent. If you set this to true, you must
907 allocate a response buffer.</LI>
908 <LI>type - Type of request (see nsctl.c)</LI>
909 <LI>id - ID of request</LI>
910 <LI>data - I'm really not sure</LI>
911 <LI>data_length - Length of data</LI>
912 </UL>
913 </TD>
914 </TR>
915 </TABLE>
916 </TD></TR></TABLE>
917
918 <H2 ID="WalledGarden">Walled Garden</H2>
919
920 Walled Garden is implemented so that you can provide perhaps limited service
921 to sessions that incorrectly authenticate.<P>
922
923 Whenever a session provides incorrect authentication, and the
924 radius server responds with Auth-Reject, the walled garden module
925 (if loaded) will force authentication to succeed, but set the flag
926 <EM>garden</EM> in the session structure, and adds an iptables rule to
927 the <B>garden_users</B> chain to force all packets for the session's IP
928 address to traverse the <B>garden</B> chain.<P>
929
930 This doesn't <EM>just work</EM>. To set this all up, you will to
931 setup the <B>garden</B> nat table with the
932 <A HREF="#build-garden">build-garden</A> script with rules to limit
933 user's traffic. For example, to force all traffic except DNS to be
934 forwarded to 192.168.1.1, add these entries to your
935 <EM>build-garden</EM>:
936 <PRE>
937 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
938 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
939 </PRE>
940
941 l2tpns will add entries to the garden_users chain as appropriate.<P>
942
943 You can check the amount of traffic being captured using the following
944 command:
945 <PRE>
946 iptables -t nat -L garden -nvx
947 </PRE>
948
949 <H2 ID="Clustering">Clustering</H2>
950
951 An l2tpns cluster consists of of one* or more servers configured with
952 the same configuration, notably the multicast <B>cluster_address</B>.<P>
953
954 *A stand-alone server is simply a degraded cluster.<P>
955
956 Initially servers come up as cluster slaves, and periodically (every
957 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
958 containing the start time of the process to the multicast
959 <B>cluster_address</B>.<P>
960
961 A cluster master sends heartbeat rather than ping packets, which
962 contain those session and tunnel changes since the last heartbeat.<P>
963
964 When a slave has not seen a heartbeat within
965 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
966 examining the list of peers it has seen pings from and determines
967 which of these and itself is the "best" candidate to be master.
968 "Best" in this context means the server with the highest uptime (the
969 highest IP address is used as a tie-breaker in the case of equal
970 uptimes).<P>
971
972 After discovering a master, and determining that it is up-to-date (has
973 seen an update for all in-use sessions and tunnels from heartbeat
974 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
975 the <B>bind_address</B> and for all addresses/networks in
976 <B>ip_pool</B>. Any packets recieved by the slave which would alter
977 the session state, as well as packets for throttled or gardened
978 sessions are forwarded to the master for handling. In addition, byte
979 counters for session traffic are periodically forwarded.<P>
980
981 A master, when determining that it has at least one up-to-date slave
982 will drop all routes (raising them again if all slaves disappear) and
983 subsequently handle only packets forwarded to it by the slaves.<P>
984
985 <H2 ID="Routing">Routing</H2>
986 If you are running a single instance, you may simply statically route
987 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
988 arp).<P>
989
990 For a cluster, configure the members as BGP neighbours on your router
991 and configure multi-path load-balancing. Cisco uses "maximum-paths
992 ibgp" for IBGP. If this is not supported by your IOS revision, you
993 can use "maximum-paths" (which works for EBGP) and set
994 <B>as_number</B> to a private value such as 64512.<P>
995
996 <H2 ID="Performance">Performance</H2>
997
998 Performance is great.<P>
999
1000 I'd like to include some pretty graphs here that show a linear performance
1001 increase, with no impact by number of connected sessions.<P>
1002
1003 That's really what it looks like.<P>
1004
1005 <BR>
1006 David Parrish<BR>
1007 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1008 </BODY>
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