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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>multi_read_count</B> (int)<BR>
 286 Number of packets to read off each of the UDP and TUN fds when
 287 returned as readable by select (default:  10).  Avoids incurring the
 288 unnecessary system call overhead of select on busy servers.
 289 </LI>
 290
 291 <LI><B>scheduler_fifo</B> (boolean)<BR>
 292 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 293 causes the kernel to immediately preempt any currently running SCHED_OTHER
 294 (normal) process in favour of l2tpns when it becomes runnable.
 295 Ignored on uniprocessor systems.
 296 </LI>
 297
 298 <LI><B>lock_pages</B> (boolean)<BR>
 299 Keep all pages mapped by the l2tpns process in memory.
 300 </LI>
 301
 302 <LI><B>icmp_rate</B> (int)<BR>
 303 Maximum number of host unreachable ICMP packets to send per second.
 304 </LI>
 305
 306 <LI><B>packet_limit</B> (int><BR>
 307 Maximum number of packets of downstream traffic to be handled each
 308 tenth of a second per session.  If zero, no limit is applied (default:
 309 0).  Intended as a DoS prevention mechanism and not a general
 310 throttling control (packets are dropped, not queued).
 311 </LI>
 312
 313 <LI><B>cluster_address</B> (ip address)<BR>
 314 Multicast cluster address (default:  239.192.13.13).  See the section
 315 on <A HREF="#Clustering">Clustering</A> for more information.
 316 </LI>
 317
 318 <LI><B>cluster_interface</B> (string)<BR>
 319 Interface for cluster packets (default: eth0).
 320 </LI>
 321
 322 <LI><B>cluster_hb_interval</B> (int)<BR>
 323 Interval in tenths of a second between cluster heartbeat/pings.
 324 </LI>
 325
 326 <LI><B>cluster_hb_timeout</B> (int)<BR>
 327 Cluster heartbeat timeout in tenths of a second.  A new master will be
 328 elected when this interval has been passed without seeing a heartbeat
 329 from the master.
 330 </LI>
 331
 332 <LI><B>cluster_master_min_adv</B> (int)<BR>
 333 Determines the minumum number of up to date slaves required before the
 334 master will drop routes (default: 1).
 335 </LI>
 336 </UL>
 337
 338 <P>BGP routing configuration is entered by the command:
 339 The routing configuration section is entered by the command
 340 <DL><DD><B>router bgp</B> <I>as</I></DL>
 341 where <I>as</I> specifies the local AS number.
 342
 343 <P>Subsequent lines prefixed with
 344 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 345 define the attributes of BGP neighhbours.  Valid commands are:
 346 <DL>
 347   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 348   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 349 </DL>
 350
 351 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 352 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 353 <I>hold</I> are the timer values in seconds.
 354
 355 <P>Named access-lists are configured using one of the commands:
 356 <DL>
 357   <DD><B>ip access-list standard</B> <I>name</I>
 358   <DD><B>ip access-list extended</B> <I>name</I>
 359 </DL>
 360
 361 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 362 define the body of the access-list.  Standard access-list syntax:
 363 <DL>
 364   <DD>{<B>permit</B>|<B>deny</B>}
 365     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 366     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 367 </DL>
 368
 369 Extended access-lists:
 370
 371 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 372   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 373     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 374     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 375   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 376     {<I>host</I>|<I>source source-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     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 379         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 380         [<B>fragments</B>]
 381   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 382     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 383         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 384     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 385         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 386         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 387             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 388             ...|<B>fragments</B>]
 389 </DIV>
 390
 391 <H3 ID="users">users</H3>
 392
 393 Usernames and passwords for the command-line interface are stored in
 394 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 395 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 396 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 397 plain text by the prefix <B>{crypt}</B>.<P>
 398
 399 The username <B>enable</B> has a special meaning and is used to set
 400 the enable password.<P>
 401
 402 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 403 port 23 will be allowed access without a username / password.<P>
 404
 405 <H3 ID="ip-pool">ip_pool</H3>
 406
 407 This file is used to configure the IP address pool which user
 408 addresses are assigned from.  This file should contain either an IP
 409 address or a CIDR network per line.  e.g.:<P>
 410
 411 <PRE>
 412     192.168.1.1
 413     192.168.1.2
 414     192.168.1.3
 415     192.168.4.0/24
 416     172.16.0.0/16
 417     10.0.0.0/8
 418 </PRE>
 419
 420 Keep in mind that l2tpns can only handle 65535 connections per
 421 process, so don't put more than 65535 IP addresses in the
 422 configuration file.  They will be wasted.
 423
 424 <H3 ID="build-garden">build-garden</H3>
 425
 426 The garden plugin on startup creates a NAT table called "garden" then
 427 sources the <B>build-garden</B> script to populate that table.  All
 428 packets from gardened users will be sent through this table.  Example:
 429
 430 <PRE>
 431     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 432     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 433     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 434     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 435     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 436     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 437     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 438     iptables -t nat -A garden -p icmp -j ACCEPT
 439     iptables -t nat -A garden -j DROP
 440 </PRE>
 441
 442 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 443
 444 A running l2tpns process can be controlled in a number of ways.  The primary
 445 method of control is by the Command-Line Interface (CLI).<P>
 446
 447 You can also remotely send commands to modules via the nsctl client
 448 provided.<P>
 449
 450 Also, there are a number of signals that l2tpns understands and takes action
 451 when it receives them.
 452
 453 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 454
 455 You can access the command line interface by telnet'ing to port 23.
 456 There is no IP address restriction, so it's a good idea to firewall
 457 this port off from anyone who doesn't need access to it.  See
 458 <A HREF="#users">users</A> for information on restricting access based
 459 on a username and password.<P>
 460
 461 The CLI gives you real-time control over almost everything in
 462 the process.  The interface is designed to look like a Cisco
 463 device, and supports things like command history, line editing and
 464 context sensitive help.  This is provided by linking with the
 465 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 466 library.  Some general documentation of the interface is
 467 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 468 here</A>.<P>
 469
 470 After you have connected to the telnet port (and perhaps logged in), you
 471 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 472
 473 Enter <EM>help</EM> to get a list of possible commands.  A brief
 474 overview of the more important commands follows:
 475
 476 <UL>
 477 <LI><B>show session</B><BR>
 478 Without specifying a session ID, this will list all tunnels currently
 479 connected.  If you specify a session ID, you will be given all
 480 information on a single tunnel.  Note that the full session list can
 481 be around 185 columns wide, so you should probably use a wide terminal
 482 to see the list properly.<P>
 483 The columns listed in the overview are:
 484 <TABLE>
 485         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 486         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 487         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 488         authentication.  If this is *, then LCP authentication has not
 489         completed.</TD></TR>
 490         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 491         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 492         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 493         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 494         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 495         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 496         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 497         trapped in the walled garden.  This field is present even if the
 498         garden module is not loaded.</TD></TR>
 499         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 500         session started</TD></TR>
 501         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 502         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 503         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 504         detected on the session</TD></TR>
 505         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 506         connected to.</TD></TR>
 507         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 508         provided during the session setup.  This field is generated by the
 509         LAC.</TD></TR>
 510 </TABLE>
 511 <P>
 512 </LI>
 513
 514 <LI><B>show users</B><BR>
 515 With no arguments, display a list of currently connected users.  If an
 516 argument is given, the session details for the given username are
 517 displayed.
 518 </LI>
 519
 520 <LI><B>show tunnel</B><BR>
 521 This will show all the open tunnels in a summary, or detail on a single
 522 tunnel if you give a tunnel id.<P>
 523 The columns listed in the overview are:
 524 <TABLE>
 525         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 526         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 527         provided by the LAC.  This has no relation to DNS, it is just
 528         a text field.</TD></TR>
 529         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 530         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 531         Opening</TD></TR>
 532         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 533         tunnel</TD></TR>
 534 </TABLE>
 535 <P>
 536 </LI>
 537
 538 <LI><B>show pool</B><BR>
 539 Displays the current IP address pool allocation.  This will only display
 540 addresses that are in use, or are reserved for re-allocation to a
 541 disconnected user.<P>
 542 If an address is not currently in use, but has been used, then in the User
 543 column the username will be shown in square brackets, followed by the time
 544 since the address was used:
 545 <PRE>
 546 IP Address      Used  Session User
 547 192.168.100.6     N           [joe.user] 1548s
 548 </PRE>
 549 <P>
 550 </LI>
 551
 552 <LI><B>show radius</B><BR>
 553 Show a summary of the in-use RADIUS sessions.  This list should not be very
 554 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 555 columns listed are:
 556 <TABLE>
 557         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 558         sent in the packet to the RADIUS server for identification.</TD></TR>
 559         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 560         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 561         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 562         request is associated with</TD></TR>
 563         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 564         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 565         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 566         discarded after 3 retries.</TD></TR>
 567 </TABLE>
 568 <P>
 569 </LI>
 570
 571 <LI><B>show running-config</B><BR>
 572 This will list the current running configuration.  This is in a format that
 573 can either be pasted into the configuration file, or run directly at the
 574 command line.
 575 <P>
 576 </LI>
 577
 578 <LI><B>show counters</B><BR>
 579 Internally, counters are kept of key values, such as bytes and packets
 580 transferred, as well as function call counters.  This function displays all
 581 these counters, and is probably only useful for debugging.<P>
 582 You can reset these counters by running <EM>clear counters</EM>.
 583 <P>
 584 </LI>
 585
 586 <LI><B>show cluster</B><BR>
 587 Show cluster status.  Shows the cluster state for this server
 588 (Master/Slave), information about known peers and (for slaves) the
 589 master IP address, last packet seen and up-to-date status.<P>
 590 See <A HREF="#Clustering">Clustering</A> for more information.
 591 <P>
 592 </LI>
 593
 594 <LI><B>write memory</B><BR>
 595 This will write the current running configuration to the config file
 596 <B>startup-config</B>, which will be run on a restart.
 597 <P>
 598 </LI>
 599
 600 <LI><B>snoop</B><BR>
 601 You must specify a username, IP address and port.  All packets for the
 602 current session for that username will be forwarded to the given
 603 host/port.  Specify <EM>no snoop username</EM> to disable interception
 604 for the session.<P>
 605
 606 If you want interception to be permanent, you will have to modify the RADIUS
 607 response for the user.  See <A HREF="#Interception">Interception</A>.
 608 <P>
 609 </LI>
 610
 611 <LI><B>throttle</B><BR>
 612 You must specify a username, which will be throttled for the current
 613 session.  Specify <EM>no throttle username</EM> to disable throttling
 614 for the current session.<P>
 615
 616 If you want throttling to be permanent, you will have to modify the
 617 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 618 <P>
 619 </LI>
 620
 621 <LI><B>drop session</B><BR>
 622 This will cleanly disconnect a session.  You must specify a session id, which
 623 you can get from <EM>show session</EM>.  This will send a disconnect message
 624 to the remote end.
 625 <P>
 626 </LI>
 627
 628 <LI><B>drop tunnel</B><BR>
 629 This will cleanly disconnect a tunnel, as well as all sessions on that
 630 tunnel.  It will send a disconnect message for each session individually, and
 631 after 10 seconds it will send a tunnel disconnect message.
 632 <P>
 633 </LI>
 634
 635 <LI><B>uptime</B><BR>
 636 This will show how long the l2tpns process has been running, and the current
 637 bandwidth utilization:
 638 <PRE>
 639 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 640 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 641 </PRE>
 642 The bandwidth line contains 4 sets of values.<BR>
 643 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 644 (user uploads), in mbits/sec.<BR>
 645 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 646 downloads).<BR>
 647 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 648 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 649 <P>
 650 These counters are updated every second.
 651 <P>
 652 </LI>
 653
 654 <LI><B>configure terminal</B><BR>
 655 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 656 The following commands are valid in this mode:<P>
 657 </LI>
 658
 659 <LI><B>load plugin</B><BR>
 660 Load a plugin.  You must specify the plugin name, and it will search in
 661 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 662 <EM>remove plugin</EM>.
 663 <P>
 664 </LI>
 665
 666 <LI><B>set</B><BR>
 667 Set a configuration variable.  You must specify the variable name, and
 668 the value.  If the value contains any spaces, you should quote the
 669 value with double (") or single (') quotes.<P>
 670
 671 You can set any <A HREF="#startup-config">startup-config</A> value in
 672 this way, although some may require a restart to take effect.<P>
 673 </LI>
 674 </UL>
 675
 676 <H3 ID="nsctl">nsctl</H3>
 677
 678 nsctl allows messages to be passed to plugins.<P>
 679
 680 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 681 <STRONG>nsctl</STRONG>(8) for more details.<P>
 682
 683 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 684 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 685
 686 <H3 ID="Signals">Signals</H3>
 687
 688 While the process is running, you can send it a few different signals, using
 689 the kill command.
 690 <PRE>
 691 killall -HUP l2tpns
 692 </PRE>
 693
 694 The signals understood are:
 695 <UL>
 696 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
 697 <LI>SIGTERM / SIGINT - Shut down for a restart.  This will dump the current
 698 state to disk (if <EM>save_state</EM> is set to true).  Upon restart, the
 699 process will read this saved state to resume active sessions.<P>
 700 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 701 every active session and tunnel before shutting down.  This is a good idea
 702 when upgrading the code, as no sessions will be left with the remote end
 703 thinking they are open.</LI>
 704 </UL>
 705
 706 <H2 ID="Throttling">Throttling</H2>
 707
 708 l2tpns contains support for slowing down user sessions to whatever speed you
 709 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 710 before this will be activated.<P>
 711
 712 If you wish a session to be throttled permanently, you should set the
 713 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 714 will be handled by the <EM>autothrottle</EM> module.<P>
 715
 716 Otherwise, you can enable and disable throttling an active session using
 717 the <EM>throttle</EM> CLI command.<P>
 718
 719 <H2 ID="Interception">Interception</H2>
 720
 721 You may have to deal with legal requirements to be able to intercept a
 722 user's traffic at any time.  l2tpns allows you to begin and end interception
 723 on the fly, as well as at authentication time.<P>
 724
 725 When a user is being intercepted, a copy of every packet they send and
 726 receive will be sent wrapped in a UDP packet to the IP address and port set
 727 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 728 variables.<P>
 729
 730 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 731
 732 To enable interception on a connected user, use the <EM>snoop username</EM>
 733 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 734 immediately.<P>
 735
 736 If you wish the user to be intercepted whenever they reconnect, you will
 737 need to modify the RADIUS response to include the Vendor-Specific value
 738 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 739 you need to have the <EM>autosnoop</EM> module loaded.<P>
 740
 741 <H2 ID="Authentication">Authentication</H2>
 742
 743 Whenever a session connects, it is not fully set up until authentication is
 744 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 745 request to l2tpns.<P>
 746
 747 This request is sent to the RADIUS server, which will hopefully respond with
 748 Auth-Accept or Auth-Reject.<P>
 749
 750 If Auth-Accept is received, the session is set up and an IP address is
 751 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 752 reply, and that address will be assigned to the client.  It can also include
 753 specific DNS servers, and a Framed-Route if that is required.<P>
 754
 755 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 756 at which point they should disconnect.  The exception to this is when the
 757 walled garden module is loaded, in which case the user still receives the
 758 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 759 should not receive any service.<P>
 760
 761 The RADIUS reply can also contain a Vendor-Specific attribute called
 762 Cisco-Avpair.  This field is a freeform text field that most Cisco
 763 devices understand to contain configuration instructions for the session.  In
 764 the case of l2tpns it is expected to be of the form
 765 <PRE>
 766 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 767 </PRE>
 768
 769 Each key-value pair is separated and passed to any modules loaded.  The
 770 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 771 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 772 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 773 contain:
 774 <PRE>
 775 intercept=yes,throttle=yes
 776 </PRE>
 777
 778 <H2 ID="Plugins">Plugins</H2>
 779
 780 So as to make l2tpns as flexible as possible (I know the core code is pretty
 781 difficult to understand), it includes a plugin API, which you can use to
 782 hook into certain events.<P>
 783
 784 There are a few example modules included - autosnoop, autothrottle and
 785 garden.<P>
 786
 787 When an event happens that has a hook, l2tpns looks for a predefined
 788 function name in every loaded module, and runs them in the order the modules
 789 were loaded.<P>
 790
 791 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 792 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 793 modules should be run for this event.<P>
 794 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 795 no further processing should be done for this event.  <EM>Use this with care.</EM>
 796
 797 Every event function called takes a specific structure named
 798 param_<EM>event</EM>, which varies in content with each event.  The
 799 function name for each event will be <B>plugin_<EM>event</EM></B>,
 800 so for the event <EM>timer</EM>, the function declaration should look like:
 801 <PRE>
 802 int plugin_timer(struct param_timer *data);
 803 </PRE>
 804
 805 A list of the available events follows, with a list of all the fields in the
 806 supplied structure:
 807 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 808 <TABLE CELLSPACING=1 CELLPADDING=3>
 809         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 810         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 811                 <TD>This is called after a RADIUS response has been
 812                 received, but before it has been processed by the
 813                 code.  This will allow you to modify the response in
 814                 some way.
 815                 </TD>
 816                 <TD>
 817                 <UL>
 818                         <LI>t - Tunnel ID</LI>
 819                         <LI>s - Session ID</LI>
 820                         <LI>username</LI>
 821                         <LI>password</LI>
 822                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 823                         <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
 824                 </UL>
 825                 </TD>
 826         </TR>
 827         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 828                 <TD>This is called after a RADIUS response has been
 829                 received, and the basic checks have been performed.  This
 830                 is what the garden module uses to force authentication
 831                 to be accepted.
 832                 </TD>
 833                 <TD>
 834                 <UL>
 835                         <LI>t - Tunnel ID</LI>
 836                         <LI>s - Session ID</LI>
 837                         <LI>username</LI>
 838                         <LI>auth_allowed - This is already set to true or
 839                         false depending on whether authentication has been
 840                         allowed so far.  You can set this to 1 or 0 to force
 841                         allow or disallow authentication</LI>
 842                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 843                 </UL>
 844                 </TD>
 845         </TR>
 846         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 847                 <TD>This is called whenever a session receives a
 848                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 849                 seriously slow down the system.</FONT>
 850                 </TD>
 851                 <TD>
 852                 <UL>
 853                         <LI>t - Tunnel ID</LI>
 854                         <LI>s - Session ID</LI>
 855                         <LI>buf - The raw packet data</LI>
 856                         <LI>len - The length of buf</LI>
 857                 </UL>
 858                 </TD>
 859         </TR>
 860         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 861                 <TD>This is called whenever a session sends a
 862                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 863                 seriously slow down the system.</FONT>
 864                 </TD>
 865                 <TD>
 866                 <UL>
 867                         <LI>t - Tunnel ID</LI>
 868                         <LI>s - Session ID</LI>
 869                         <LI>buf - The raw packet data</LI>
 870                         <LI>len - The length of buf</LI>
 871                 </UL>
 872                 </TD>
 873         </TR>
 874         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 875                 <TD>This is run every second, no matter what is happening.
 876                 This is called from a signal handler, so make sure anything
 877                 you do is reentrant.
 878                 </TD>
 879                 <TD>
 880                 <UL>
 881                         <LI>time_now - The current unix timestamp</LI>
 882                 </UL>
 883                 </TD>
 884         </TR>
 885         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 886                 <TD>This is called after a session is fully set up.  The
 887                 session is now ready to handle traffic.
 888                 </TD>
 889                 <TD>
 890                 <UL>
 891                         <LI>t - Tunnel ID</LI>
 892                         <LI>s - Session ID</LI>
 893                 </UL>
 894                 </TD>
 895         </TR>
 896         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 897                 <TD>This is called when a session is about to be shut down.
 898                 This may be called multiple times for the same session.
 899                 </TD>
 900                 <TD>
 901                 <UL>
 902                         <LI>t - Tunnel ID</LI>
 903                         <LI>s - Session ID</LI>
 904                 </UL>
 905                 </TD>
 906         </TR>
 907         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 908                 <TD>This is called whenever a RADIUS response includes a
 909                 Cisco-Avpair value.  The value is split up into
 910                 <EM>key=value</EM> pairs, and each is processed through all
 911                 modules.
 912                 </TD>
 913                 <TD>
 914                 <UL>
 915                         <LI>t - Tunnel ID</LI>
 916                         <LI>s - Session ID</LI>
 917                         <LI>key</LI>
 918                         <LI>value</LI>
 919                 </UL>
 920                 </TD>
 921         </TR>
 922         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 923                 <TD>This is called in whenever a nsctl packet is received.
 924                 This should handle the packet and form a response if
 925                 required.
 926                 </TD>
 927                 <TD>
 928                 <UL>
 929                         <LI>buf - The raw packet data</LI>
 930                         <LI>l - The raw packet data length</LI>
 931                         <LI>source_ip - Where the request came from</LI>
 932                         <LI>source_port - Where the request came from</LI>
 933                         <LI>response - Allocate a buffer and put your response in here</LI>
 934                         <LI>response_length - Length of response</LI>
 935                         <LI>send_response - true or false whether a response
 936                         should be sent.  If you set this to true, you must
 937                         allocate a response buffer.</LI>
 938                         <LI>type - Type of request (see nsctl.c)</LI>
 939                         <LI>id - ID of request</LI>
 940                         <LI>data - I'm really not sure</LI>
 941                         <LI>data_length - Length of data</LI>
 942                 </UL>
 943                 </TD>
 944         </TR>
 945 </TABLE>
 946 </TD></TR></TABLE>
 947
 948 <H2 ID="WalledGarden">Walled Garden</H2>
 949
 950 Walled Garden is implemented so that you can provide perhaps limited service
 951 to sessions that incorrectly authenticate.<P>
 952
 953 Whenever a session provides incorrect authentication, and the
 954 RADIUS server responds with Auth-Reject, the walled garden module
 955 (if loaded) will force authentication to succeed, but set the flag
 956 <EM>garden</EM> in the session structure, and adds an iptables rule to
 957 the <B>garden_users</B> chain to force all packets for the session's IP
 958 address to traverse the <B>garden</B> chain.<P>
 959
 960 This doesn't <EM>just work</EM>.  To set this all up, you will to
 961 setup the <B>garden</B> nat table with the
 962 <A HREF="#build-garden">build-garden</A> script with rules to limit
 963 user's traffic.  For example, to force all traffic except DNS to be
 964 forwarded to 192.168.1.1, add these entries to your
 965 <EM>build-garden</EM>:
 966 <PRE>
 967 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
 968 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
 969 </PRE>
 970
 971 l2tpns will add entries to the garden_users chain as appropriate.<P>
 972
 973 You can check the amount of traffic being captured using the following
 974 command:
 975 <PRE>
 976 iptables -t nat -L garden -nvx
 977 </PRE>
 978
 979 <H2 ID="Filtering">Filtering</H2>
 980
 981 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
 982 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
 983 access-list <I>filter</I> should be applied to traffic from the
 984 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
 985 customer.
 986
 987 <H2 ID="Clustering">Clustering</H2>
 988
 989 An l2tpns cluster consists of of one* or more servers configured with
 990 the same configuration, notably the multicast <B>cluster_address</B>.<P>
 991
 992 *A stand-alone server is simply a degraded cluster.<P>
 993
 994 Initially servers come up as cluster slaves, and periodically (every
 995 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
 996 containing the start time of the process to the multicast
 997 <B>cluster_address</B>.<P>
 998
 999 A cluster master sends heartbeat rather than ping packets, which
1000 contain those session and tunnel changes since the last heartbeat.<P>
1001
1002 When a slave has not seen a heartbeat within
1003 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1004 examining the list of peers it has seen pings from and determines
1005 which of these and itself is the "best" candidate to be master.
1006 "Best" in this context means the server with the highest uptime (the
1007 highest IP address is used as a tie-breaker in the case of equal
1008 uptimes).<P>
1009
1010 After discovering a master, and determining that it is up-to-date (has
1011 seen an update for all in-use sessions and tunnels from heartbeat
1012 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1013 the <B>bind_address</B> and for all addresses/networks in
1014 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1015 the session state, as well as packets for throttled or gardened
1016 sessions are forwarded to the master for handling.  In addition, byte
1017 counters for session traffic are periodically forwarded.<P>
1018
1019 A master, when determining that it has at least one up-to-date slave
1020 will drop all routes (raising them again if all slaves disappear) and
1021 subsequently handle only packets forwarded to it by the slaves.<P>
1022
1023 <H2 ID="Routing">Routing</H2>
1024 If you are running a single instance, you may simply statically route
1025 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1026 arp).<P>
1027
1028 For a cluster, configure the members as BGP neighbours on your router
1029 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1030 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1031 can use "maximum-paths" (which works for EBGP) and set
1032 <B>as_number</B> to a private value such as 64512.<P>
1033
1034 <H2 ID="Performance">Performance</H2>
1035
1036 Performance is great.<P>
1037
1038 I'd like to include some pretty graphs here that show a linear performance
1039 increase, with no impact by number of connected sessions.<P>
1040
1041 That's really what it looks like.<P>
1042
1043 <BR>
1044 David Parrish<BR>
1045 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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