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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>primary_radius</B> (ip address)
 195 <LI><B>secondary_radius</B> (ip address)<BR>
 196 Sets the RADIUS servers used for both authentication and accounting.
 197 If the primary server does not respond, then the secondary RADIUS
 198 server will be tried.<br>
 199 <strong>Note:</strong> in addition to the source IP address and
 200 identifier, the RADIUS server <strong>must</strong> include the source
 201 port when detecting duplicates to supress (in order to cope with a
 202 large number of sessions comming on-line simultaneously l2tpns uses a
 203 set of udp sockets, each with a seperate identifier).
 204 </LI>
 205
 206 <LI><B>primary_radius_port</B> (short)
 207 <LI><B>secondary_radius_port</B> (short)<BR>
 208 Sets the authentication ports for the primary and secondary RADIUS
 209 servers.  The accounting port is one more than the authentication
 210 port.  If no RADIUS ports are given, the authentication port defaults
 211 to 1645, and the accounting port to 1646.
 212 </LI>
 213
 214 <LI><B>radius_accounting</B> (boolean)<BR>
 215 If set to true, then RADIUS accounting packets will be sent.  This
 216 means that a Start record will be sent when the session is
 217 successfully authenticated, and a Stop record will be sent when the
 218 session is closed.
 219 </LI>
 220
 221 <LI><B>radius_secret</B> (string)<BR>
 222 This secret will be used in all RADIUS queries.  If this is not set then
 223 RADIUS queries will fail.
 224 </LI>
 225
 226 <LI><B>bind_address</B> (ip address)<BR>
 227 When the tun interface is created, it is assigned the address
 228 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 229 containing user traffic should be routed via this address if given,
 230 otherwise the primary address of the machine.
 231 </LI>
 232
 233 <LI><B>peer_address</B> (ip address)<BR>
 234 Address to send to clients as the default gateway.
 235 </L1>
 236
 237 <LI><B>send_garp</B> (boolean)<BR>
 238 Determines whether or not to send a gratuitous ARP for the
 239 bind_address when the server is ready to handle traffic (default:
 240 true).<BR>
 241 This value is ignored if BGP is configured.
 242 </LI>
 243
 244 <LI><B>throttle_speed</B> (int)<BR>
 245 Sets the default speed (in kbits/s) which sessions will be limited to.
 246 If this is set to 0, then throttling will not be used at all.  Note:
 247 You can set this by the CLI, but changes will not affect currently
 248 connected users.
 249 </LI>
 250
 251 <LI><B>throttle_buckets</B> (int)<BR>
 252 Number of token buckets to allocate for throttling.  Each throttled
 253 session requires two buckets (in and out).
 254 </LI>
 255
 256 <LI><B>accounting_dir</B> (string)<BR>
 257 If set to a directory, then every 5 minutes the current usage for
 258 every connected use will be dumped to a file in this directory.  Each
 259 file dumped begins with a header, where each line is prefixed by #.
 260 Following the header is a single line for every connected user, fields
 261 separated by a space.<BR> The fields are username, ip, qos,
 262 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 263 2 if the user is throttled.
 264 </LI>
 265
 266 <LI><B>setuid</B> (int)<BR>
 267 After starting up and binding the interface, change UID to this.  This
 268 doesn't work properly.
 269 </LI>
 270
 271 <LI><B>dump_speed</B> (boolean)<BR>
 272 If set to true, then the current bandwidth utilization will be logged every
 273 second.  Even if this is disabled, you can see this information by running
 274 the <EM>uptime</EM> command on the CLI.
 275 </LI>
 276
 277 <LI><B>cleanup_interval</B> (int)<BR>
 278 Interval between regular cleanups (in seconds).
 279 </LI>
 280
 281 <LI><B>multi_read_count</B> (int)<BR>
 282 Number of packets to read off each of the UDP and TUN fds when
 283 returned as readable by select (default:  10).  Avoids incurring the
 284 unnecessary system call overhead of select on busy servers.
 285 </LI>
 286
 287 <LI><B>scheduler_fifo</B> (boolean)<BR>
 288 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 289 causes the kernel to immediately preempt any currently running SCHED_OTHER
 290 (normal) process in favour of l2tpns when it becomes runnable.
 291 Ignored on uniprocessor systems.
 292 </LI>
 293
 294 <LI><B>lock_pages</B> (boolean)<BR>
 295 Keep all pages mapped by the l2tpns process in memory.
 296 </LI>
 297
 298 <LI><B>icmp_rate</B> (int)<BR>
 299 Maximum number of host unreachable ICMP packets to send per second.
 300 </LI>
 301
 302 <LI><B>packet_limit</B> (int><BR>
 303 Maximum number of packets of downstream traffic to be handled each
 304 tenth of a second per session.  If zero, no limit is applied (default:
 305 0).  Intended as a DoS prevention mechanism and not a general
 306 throttling control (packets are dropped, not queued).
 307 </LI>
 308
 309 <LI><B>cluster_address</B> (ip address)<BR>
 310 Multicast cluster address (default:  239.192.13.13).  See the section
 311 on <A HREF="#Clustering">Clustering</A> for more information.
 312 </LI>
 313
 314 <LI><B>cluster_interface</B> (string)<BR>
 315 Interface for cluster packets (default: eth0).
 316 </LI>
 317
 318 <LI><B>cluster_hb_interval</B> (int)<BR>
 319 Interval in tenths of a second between cluster heartbeat/pings.
 320 </LI>
 321
 322 <LI><B>cluster_hb_timeout</B> (int)<BR>
 323 Cluster heartbeat timeout in tenths of a second.  A new master will be
 324 elected when this interval has been passed without seeing a heartbeat
 325 from the master.
 326 </LI>
 327
 328 <LI><B>cluster_master_min_adv</B> (int)<BR>
 329 Determines the minumum number of up to date slaves required before the
 330 master will drop routes (default: 1).
 331 </LI>
 332 </UL>
 333
 334 <P>BGP routing configuration is entered by the command:
 335 The routing configuration section is entered by the command
 336 <DL><DD><B>router bgp</B> <I>as</I></DL>
 337 where <I>as</I> specifies the local AS number.
 338
 339 <P>Subsequent lines prefixed with
 340 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 341 define the attributes of BGP neighhbours.  Valid commands are:
 342 <DL>
 343   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 344   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 345 </DL>
 346
 347 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 348 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 349 <I>hold</I> are the timer values in seconds.
 350
 351 <P>Named access-lists are configured using one of the commands:
 352 <DL>
 353   <DD><B>ip access-list standard</B> <I>name</I>
 354   <DD><B>ip access-list extended</B> <I>name</I>
 355 </DL>
 356
 357 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 358 define the body of the access-list.  Standard access-list syntax:
 359 <DL>
 360   <DD>{<B>permit</B>|<B>deny</B>}
 361     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 362     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 363 </DL>
 364
 365 Extended access-lists:
 366
 367 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 368   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 369     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 370     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 371   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 372     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 373         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 374     {<I>host</I>|<I>destination destination-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         [<B>fragments</B>]
 377   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 378     {<I>host</I>|<I>source source-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     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 381         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 382         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 383             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 384             ...|<B>fragments</B>]
 385 </DIV>
 386
 387 <H3 ID="users">users</H3>
 388
 389 Usernames and passwords for the command-line interface are stored in
 390 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 391 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 392 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 393 plain text by the prefix <B>{crypt}</B>.<P>
 394
 395 The username <B>enable</B> has a special meaning and is used to set
 396 the enable password.<P>
 397
 398 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 399 port 23 will be allowed access without a username / password.<P>
 400
 401 <H3 ID="ip-pool">ip_pool</H3>
 402
 403 This file is used to configure the IP address pool which user
 404 addresses are assigned from.  This file should contain either an IP
 405 address or a CIDR network per line.  e.g.:<P>
 406
 407 <PRE>
 408     192.168.1.1
 409     192.168.1.2
 410     192.168.1.3
 411     192.168.4.0/24
 412     172.16.0.0/16
 413     10.0.0.0/8
 414 </PRE>
 415
 416 Keep in mind that l2tpns can only handle 65535 connections per
 417 process, so don't put more than 65535 IP addresses in the
 418 configuration file.  They will be wasted.
 419
 420 <H3 ID="build-garden">build-garden</H3>
 421
 422 The garden plugin on startup creates a NAT table called "garden" then
 423 sources the <B>build-garden</B> script to populate that table.  All
 424 packets from gardened users will be sent through this table.  Example:
 425
 426 <PRE>
 427     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 428     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 429     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 430     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 431     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 432     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 433     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 434     iptables -t nat -A garden -p icmp -j ACCEPT
 435     iptables -t nat -A garden -j DROP
 436 </PRE>
 437
 438 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 439
 440 A running l2tpns process can be controlled in a number of ways.  The primary
 441 method of control is by the Command-Line Interface (CLI).<P>
 442
 443 You can also remotely send commands to modules via the nsctl client
 444 provided.<P>
 445
 446 Also, there are a number of signals that l2tpns understands and takes action
 447 when it receives them.
 448
 449 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 450
 451 You can access the command line interface by telnet'ing to port 23.
 452 There is no IP address restriction, so it's a good idea to firewall
 453 this port off from anyone who doesn't need access to it.  See
 454 <A HREF="#users">users</A> for information on restricting access based
 455 on a username and password.<P>
 456
 457 The CLI gives you real-time control over almost everything in
 458 the process.  The interface is designed to look like a Cisco
 459 device, and supports things like command history, line editing and
 460 context sensitive help.  This is provided by linking with the
 461 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 462 library.  Some general documentation of the interface is
 463 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 464 here</A>.<P>
 465
 466 After you have connected to the telnet port (and perhaps logged in), you
 467 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 468
 469 Enter <EM>help</EM> to get a list of possible commands.  A brief
 470 overview of the more important commands follows:
 471
 472 <UL>
 473 <LI><B>show session</B><BR>
 474 Without specifying a session ID, this will list all tunnels currently
 475 connected.  If you specify a session ID, you will be given all
 476 information on a single tunnel.  Note that the full session list can
 477 be around 185 columns wide, so you should probably use a wide terminal
 478 to see the list properly.<P>
 479 The columns listed in the overview are:
 480 <TABLE>
 481         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 482         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 483         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 484         authentication.  If this is *, then LCP authentication has not
 485         completed.</TD></TR>
 486         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 487         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 488         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 489         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 490         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 491         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 492         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 493         trapped in the walled garden.  This field is present even if the
 494         garden module is not loaded.</TD></TR>
 495         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 496         session started</TD></TR>
 497         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 498         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 499         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 500         detected on the session</TD></TR>
 501         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 502         connected to.</TD></TR>
 503         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 504         provided during the session setup.  This field is generated by the
 505         LAC.</TD></TR>
 506 </TABLE>
 507 <P>
 508 </LI>
 509
 510 <LI><B>show users</B><BR>
 511 With no arguments, display a list of currently connected users.  If an
 512 argument is given, the session details for the given username are
 513 displayed.
 514 </LI>
 515
 516 <LI><B>show tunnel</B><BR>
 517 This will show all the open tunnels in a summary, or detail on a single
 518 tunnel if you give a tunnel id.<P>
 519 The columns listed in the overview are:
 520 <TABLE>
 521         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 522         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 523         provided by the LAC.  This has no relation to DNS, it is just
 524         a text field.</TD></TR>
 525         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 526         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 527         Opening</TD></TR>
 528         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 529         tunnel</TD></TR>
 530 </TABLE>
 531 <P>
 532 </LI>
 533
 534 <LI><B>show pool</B><BR>
 535 Displays the current IP address pool allocation.  This will only display
 536 addresses that are in use, or are reserved for re-allocation to a
 537 disconnected user.<P>
 538 If an address is not currently in use, but has been used, then in the User
 539 column the username will be shown in square brackets, followed by the time
 540 since the address was used:
 541 <PRE>
 542 IP Address      Used  Session User
 543 192.168.100.6     N           [joe.user] 1548s
 544 </PRE>
 545 <P>
 546 </LI>
 547
 548 <LI><B>show radius</B><BR>
 549 Show a summary of the in-use RADIUS sessions.  This list should not be very
 550 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 551 columns listed are:
 552 <TABLE>
 553         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 554         sent in the packet to the RADIUS server for identification.</TD></TR>
 555         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 556         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 557         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 558         request is associated with</TD></TR>
 559         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 560         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 561         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 562         discarded after 3 retries.</TD></TR>
 563 </TABLE>
 564 <P>
 565 </LI>
 566
 567 <LI><B>show running-config</B><BR>
 568 This will list the current running configuration.  This is in a format that
 569 can either be pasted into the configuration file, or run directly at the
 570 command line.
 571 <P>
 572 </LI>
 573
 574 <LI><B>show counters</B><BR>
 575 Internally, counters are kept of key values, such as bytes and packets
 576 transferred, as well as function call counters.  This function displays all
 577 these counters, and is probably only useful for debugging.<P>
 578 You can reset these counters by running <EM>clear counters</EM>.
 579 <P>
 580 </LI>
 581
 582 <LI><B>show cluster</B><BR>
 583 Show cluster status.  Shows the cluster state for this server
 584 (Master/Slave), information about known peers and (for slaves) the
 585 master IP address, last packet seen and up-to-date status.<P>
 586 See <A HREF="#Clustering">Clustering</A> for more information.
 587 <P>
 588 </LI>
 589
 590 <LI><B>write memory</B><BR>
 591 This will write the current running configuration to the config file
 592 <B>startup-config</B>, which will be run on a restart.
 593 <P>
 594 </LI>
 595
 596 <LI><B>snoop</B><BR>
 597 You must specify a username, IP address and port.  All packets for the
 598 current session for that username will be forwarded to the given
 599 host/port.  Specify <EM>no snoop username</EM> to disable interception
 600 for the session.<P>
 601
 602 If you want interception to be permanent, you will have to modify the RADIUS
 603 response for the user.  See <A HREF="#Interception">Interception</A>.
 604 <P>
 605 </LI>
 606
 607 <LI><B>throttle</B><BR>
 608 You must specify a username, which will be throttled for the current
 609 session.  Specify <EM>no throttle username</EM> to disable throttling
 610 for the current session.<P>
 611
 612 If you want throttling to be permanent, you will have to modify the
 613 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 614 <P>
 615 </LI>
 616
 617 <LI><B>drop session</B><BR>
 618 This will cleanly disconnect a session.  You must specify a session id, which
 619 you can get from <EM>show session</EM>.  This will send a disconnect message
 620 to the remote end.
 621 <P>
 622 </LI>
 623
 624 <LI><B>drop tunnel</B><BR>
 625 This will cleanly disconnect a tunnel, as well as all sessions on that
 626 tunnel.  It will send a disconnect message for each session individually, and
 627 after 10 seconds it will send a tunnel disconnect message.
 628 <P>
 629 </LI>
 630
 631 <LI><B>uptime</B><BR>
 632 This will show how long the l2tpns process has been running, and the current
 633 bandwidth utilization:
 634 <PRE>
 635 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 636 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 637 </PRE>
 638 The bandwidth line contains 4 sets of values.<BR>
 639 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 640 (user uploads), in mbits/sec.<BR>
 641 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 642 downloads).<BR>
 643 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 644 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 645 <P>
 646 These counters are updated every second.
 647 <P>
 648 </LI>
 649
 650 <LI><B>configure terminal</B><BR>
 651 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 652 The following commands are valid in this mode:<P>
 653 </LI>
 654
 655 <LI><B>load plugin</B><BR>
 656 Load a plugin.  You must specify the plugin name, and it will search in
 657 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 658 <EM>remove plugin</EM>.
 659 <P>
 660 </LI>
 661
 662 <LI><B>set</B><BR>
 663 Set a configuration variable.  You must specify the variable name, and
 664 the value.  If the value contains any spaces, you should quote the
 665 value with double (") or single (') quotes.<P>
 666
 667 You can set any <A HREF="#startup-config">startup-config</A> value in
 668 this way, although some may require a restart to take effect.<P>
 669 </LI>
 670 </UL>
 671
 672 <H3 ID="nsctl">nsctl</H3>
 673
 674 nsctl allows messages to be passed to plugins.<P>
 675
 676 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 677 <STRONG>nsctl</STRONG>(8) for more details.<P>
 678
 679 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 680 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 681
 682 <H3 ID="Signals">Signals</H3>
 683
 684 While the process is running, you can send it a few different signals, using
 685 the kill command.
 686 <PRE>
 687 killall -HUP l2tpns
 688 </PRE>
 689
 690 The signals understood are:
 691 <UL>
 692 <LI>SIGHUP - Reload the config from disk and re-open log file</LI>
 693 <LI>SIGTERM / SIGINT - Shut down.</LI>
 694 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 695 every active session and tunnel before shutting down.</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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