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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>l2tp_mtu</B> (int)<BR>
 188 MTU of interface for L2TP traffic (default: 1500).  Used to set link
 189 MRU and adjust TCP MSS.
 190 </LI>
 191
 192 <LI><B>ppp_restart_time</B> (int)<BR>
 193 <B>ppp_max_configure</B> (int)<BR>
 194 <B>ppp_max_failure</B> (int)<BR>
 195 PPP counter and timer values, as described in &sect;4.1 of
 196 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661</a>.
 197 </LI>
 198
 199 <LI><B>primary_dns</B> (ip address)
 200 <LI><B>secondary_dns</B> (ip address)<BR>
 201 Whenever a PPP connection is established, DNS servers will be sent to the
 202 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 203 one will not be sent.
 204 </LI>
 205
 206 <LI><B>primary_radius</B> (ip address)
 207 <LI><B>secondary_radius</B> (ip address)<BR>
 208 Sets the RADIUS servers used for both authentication and accounting.
 209 If the primary server does not respond, then the secondary RADIUS
 210 server will be tried.<br>
 211 <strong>Note:</strong> in addition to the source IP address and
 212 identifier, the RADIUS server <strong>must</strong> include the source
 213 port when detecting duplicates to supress (in order to cope with a
 214 large number of sessions comming on-line simultaneously l2tpns uses a
 215 set of udp sockets, each with a seperate identifier).
 216 </LI>
 217
 218 <LI><B>primary_radius_port</B> (short)
 219 <LI><B>secondary_radius_port</B> (short)<BR>
 220 Sets the authentication ports for the primary and secondary RADIUS
 221 servers.  The accounting port is one more than the authentication
 222 port.  If no RADIUS ports are given, the authentication port defaults
 223 to 1645, and the accounting port to 1646.
 224 </LI>
 225
 226 <LI><B>radius_accounting</B> (boolean)<BR>
 227 If set to true, then RADIUS accounting packets will be sent.  This
 228 means that a Start record will be sent when the session is
 229 successfully authenticated, and a Stop record will be sent when the
 230 session is closed.
 231 </LI>
 232
 233 <LI><B>radius_secret</B> (string)<BR>
 234 This secret will be used in all RADIUS queries.  If this is not set then
 235 RADIUS queries will fail.
 236 </LI>
 237
 238 <LI><B>radius_authtypes</B> (string)</BR>
 239 A comma separated list of supported RADIUS authentication methods
 240 (<B>pap</B> or <B>chap</B>), in order of preference (default <B>pap</B>).
 241 </LI>
 242
 243 <LI><B>radius_dae_port</B> (short)<BR>
 244 Port for DAE RADIUS (Packet of Death/Disconnect, Change of Authorization)
 245 requests (default: <B>3799</B>).
 246 </LI>
 247
 248 <LI><B>allow_duplicate_users</B> (boolean)</BR>
 249 Allow multiple logins with the same username.  If false (the default),
 250 any prior session with the same username will be dropped when a new
 251 session is established.
 252 </LI>
 253
 254 <LI><B>bind_address</B> (ip address)<BR>
 255 When the tun interface is created, it is assigned the address
 256 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 257 containing user traffic should be routed via this address if given,
 258 otherwise the primary address of the machine.
 259 </LI>
 260
 261 <LI><B>peer_address</B> (ip address)<BR>
 262 Address to send to clients as the default gateway.
 263 </L1>
 264
 265 <LI><B>send_garp</B> (boolean)<BR>
 266 Determines whether or not to send a gratuitous ARP for the
 267 bind_address when the server is ready to handle traffic (default:
 268 true).<BR>
 269 This value is ignored if BGP is configured.
 270 </LI>
 271
 272 <LI><B>throttle_speed</B> (int)<BR>
 273 Sets the default speed (in kbits/s) which sessions will be limited to.
 274 If this is set to 0, then throttling will not be used at all.  Note:
 275 You can set this by the CLI, but changes will not affect currently
 276 connected users.
 277 </LI>
 278
 279 <LI><B>throttle_buckets</B> (int)<BR>
 280 Number of token buckets to allocate for throttling.  Each throttled
 281 session requires two buckets (in and out).
 282 </LI>
 283
 284 <LI><B>accounting_dir</B> (string)<BR>
 285 If set to a directory, then every 5 minutes the current usage for
 286 every connected use will be dumped to a file in this directory.  Each
 287 file dumped begins with a header, where each line is prefixed by #.
 288 Following the header is a single line for every connected user, fields
 289 separated by a space.<BR> The fields are username, ip, qos,
 290 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 291 2 if the user is throttled.
 292 </LI>
 293
 294 <LI><B>setuid</B> (int)<BR>
 295 After starting up and binding the interface, change UID to this.  This
 296 doesn't work properly.
 297 </LI>
 298
 299 <LI><B>dump_speed</B> (boolean)<BR>
 300 If set to true, then the current bandwidth utilization will be logged every
 301 second.  Even if this is disabled, you can see this information by running
 302 the <EM>uptime</EM> command on the CLI.
 303 </LI>
 304
 305 <LI><B>multi_read_count</B> (int)<BR>
 306 Number of packets to read off each of the UDP and TUN fds when
 307 returned as readable by select (default:  10).  Avoids incurring the
 308 unnecessary system call overhead of select on busy servers.
 309 </LI>
 310
 311 <LI><B>scheduler_fifo</B> (boolean)<BR>
 312 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 313 causes the kernel to immediately preempt any currently running SCHED_OTHER
 314 (normal) process in favour of l2tpns when it becomes runnable.
 315 Ignored on uniprocessor systems.
 316 </LI>
 317
 318 <LI><B>lock_pages</B> (boolean)<BR>
 319 Keep all pages mapped by the l2tpns process in memory.
 320 </LI>
 321
 322 <LI><B>icmp_rate</B> (int)<BR>
 323 Maximum number of host unreachable ICMP packets to send per second.
 324 </LI>
 325
 326 <LI><B>packet_limit</B> (int><BR>
 327 Maximum number of packets of downstream traffic to be handled each
 328 tenth of a second per session.  If zero, no limit is applied (default:
 329 0).  Intended as a DoS prevention mechanism and not a general
 330 throttling control (packets are dropped, not queued).
 331 </LI>
 332
 333 <LI><B>cluster_address</B> (ip address)<BR>
 334 Multicast cluster address (default:  239.192.13.13).  See the section
 335 on <A HREF="#Clustering">Clustering</A> for more information.
 336 </LI>
 337
 338 <LI><B>cluster_interface</B> (string)<BR>
 339 Interface for cluster packets (default: eth0).
 340 </LI>
 341
 342 <LI><B>cluster_mcast_ttl</B> (int)<BR>
 343 TTL for multicast packets (default: 1).
 344 </LI>
 345
 346 <LI><B>cluster_hb_interval</B> (int)<BR>
 347 Interval in tenths of a second between cluster heartbeat/pings.
 348 </LI>
 349
 350 <LI><B>cluster_hb_timeout</B> (int)<BR>
 351 Cluster heartbeat timeout in tenths of a second.  A new master will be
 352 elected when this interval has been passed without seeing a heartbeat
 353 from the master.
 354 </LI>
 355
 356 <LI><B>cluster_master_min_adv</B> (int)<BR>
 357 Determines the minumum number of up to date slaves required before the
 358 master will drop routes (default: 1).
 359 </LI>
 360
 361 <LI><B>echo_timeout</B> (int)<BR>
 362 Time between last packet sent and LCP ECHO generation
 363 (default: 10 (seconds)).
 364 </LI>
 365
 366 <LI><B>idle_echo_timeout</B> (int)<BR>
 367 Drop sessions who have not responded within idle_echo_timeout seconds
 368 (default: 240 (seconds))
 369 </LI>
 370
 371 </UL>
 372
 373 <P>BGP routing configuration is entered by the command:
 374 The routing configuration section is entered by the command
 375 <DL><DD><B>router bgp</B> <I>as</I></DL>
 376 where <I>as</I> specifies the local AS number.
 377
 378 <P>Subsequent lines prefixed with
 379 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 380 define the attributes of BGP neighhbours.  Valid commands are:
 381 <DL>
 382   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 383   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 384 </DL>
 385
 386 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 387 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 388 <I>hold</I> are the timer values in seconds.
 389
 390 <P>Named access-lists are configured using one of the commands:
 391 <DL>
 392   <DD><B>ip access-list standard</B> <I>name</I>
 393   <DD><B>ip access-list extended</B> <I>name</I>
 394 </DL>
 395
 396 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 397 define the body of the access-list.  Standard access-list syntax:
 398 <DL>
 399   <DD>{<B>permit</B>|<B>deny</B>}
 400     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 401     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 402 </DL>
 403
 404 Extended access-lists:
 405
 406 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 407   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 408     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 409     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 410   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 411     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 412         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 413     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 414         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 415         [<B>fragments</B>]
 416   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 417     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 418         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 419     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 420         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 421         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 422             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 423             ...|<B>fragments</B>]
 424 </DIV>
 425
 426 <H3 ID="users">users</H3>
 427
 428 Usernames and passwords for the command-line interface are stored in
 429 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 430 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 431 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 432 plain text by the prefix <B>{crypt}</B>.<P>
 433
 434 The username <B>enable</B> has a special meaning and is used to set
 435 the enable password.<P>
 436
 437 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 438 port 23 will be allowed access without a username / password.<P>
 439
 440 <H3 ID="ip-pool">ip_pool</H3>
 441
 442 This file is used to configure the IP address pool which user
 443 addresses are assigned from.  This file should contain either an IP
 444 address or a CIDR network per line.  e.g.:<P>
 445
 446 <PRE>
 447     192.168.1.1
 448     192.168.1.2
 449     192.168.1.3
 450     192.168.4.0/24
 451     172.16.0.0/16
 452     10.0.0.0/8
 453 </PRE>
 454
 455 Keep in mind that l2tpns can only handle 65535 connections per
 456 process, so don't put more than 65535 IP addresses in the
 457 configuration file.  They will be wasted.
 458
 459 <H3 ID="build-garden">build-garden</H3>
 460
 461 The garden plugin on startup creates a NAT table called "garden" then
 462 sources the <B>build-garden</B> script to populate that table.  All
 463 packets from gardened users will be sent through this table.  Example:
 464
 465 <PRE>
 466     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 467     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 468     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 469     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 470     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 471     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 472     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 473     iptables -t nat -A garden -p icmp -j ACCEPT
 474     iptables -t nat -A garden -j DROP
 475 </PRE>
 476
 477 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 478
 479 A running l2tpns process can be controlled in a number of ways.  The primary
 480 method of control is by the Command-Line Interface (CLI).<P>
 481
 482 You can also remotely send commands to modules via the nsctl client
 483 provided.<P>
 484
 485 Also, there are a number of signals that l2tpns understands and takes action
 486 when it receives them.
 487
 488 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 489
 490 You can access the command line interface by telnet'ing to port 23.
 491 There is no IP address restriction, so it's a good idea to firewall
 492 this port off from anyone who doesn't need access to it.  See
 493 <A HREF="#users">users</A> for information on restricting access based
 494 on a username and password.<P>
 495
 496 The CLI gives you real-time control over almost everything in
 497 the process.  The interface is designed to look like a Cisco
 498 device, and supports things like command history, line editing and
 499 context sensitive help.  This is provided by linking with the
 500 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 501 library.  Some general documentation of the interface is
 502 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 503 here</A>.<P>
 504
 505 After you have connected to the telnet port (and perhaps logged in), you
 506 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 507
 508 Enter <EM>help</EM> to get a list of possible commands.  A brief
 509 overview of the more important commands follows:
 510
 511 <UL>
 512 <LI><B>show session</B><BR>
 513 Without specifying a session ID, this will list all tunnels currently
 514 connected.  If you specify a session ID, you will be given all
 515 information on a single tunnel.  Note that the full session list can
 516 be around 185 columns wide, so you should probably use a wide terminal
 517 to see the list properly.<P>
 518 The columns listed in the overview are:
 519 <TABLE>
 520         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 521         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 522         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 523         authentication.  If this is *, then LCP authentication has not
 524         completed.</TD></TR>
 525         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 526         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 527         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 528         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 529         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 530         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 531         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 532         trapped in the walled garden.  This field is present even if the
 533         garden module is not loaded.</TD></TR>
 534         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 535         session started</TD></TR>
 536         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 537         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 538         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 539         detected on the session</TD></TR>
 540         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 541         connected to.</TD></TR>
 542         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 543         provided during the session setup.  This field is generated by the
 544         LAC.</TD></TR>
 545 </TABLE>
 546 <P>
 547 </LI>
 548
 549 <LI><B>show users</B><BR>
 550 With no arguments, display a list of currently connected users.  If an
 551 argument is given, the session details for the given username are
 552 displayed.
 553 </LI>
 554
 555 <LI><B>show tunnel</B><BR>
 556 This will show all the open tunnels in a summary, or detail on a single
 557 tunnel if you give a tunnel id.<P>
 558 The columns listed in the overview are:
 559 <TABLE>
 560         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 561         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 562         provided by the LAC.  This has no relation to DNS, it is just
 563         a text field.</TD></TR>
 564         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 565         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 566         Opening</TD></TR>
 567         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 568         tunnel</TD></TR>
 569 </TABLE>
 570 <P>
 571 </LI>
 572
 573 <LI><B>show pool</B><BR>
 574 Displays the current IP address pool allocation.  This will only display
 575 addresses that are in use, or are reserved for re-allocation to a
 576 disconnected user.<P>
 577 If an address is not currently in use, but has been used, then in the User
 578 column the username will be shown in square brackets, followed by the time
 579 since the address was used:
 580 <PRE>
 581 IP Address      Used  Session User
 582 192.168.100.6     N           [joe.user] 1548s
 583 </PRE>
 584 <P>
 585 </LI>
 586
 587 <LI><B>show radius</B><BR>
 588 Show a summary of the in-use RADIUS sessions.  This list should not be very
 589 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 590 columns listed are:
 591 <TABLE>
 592         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 593         sent in the packet to the RADIUS server for identification.</TD></TR>
 594         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 595         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 596         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 597         request is associated with</TD></TR>
 598         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 599         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 600         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 601         discarded after 3 retries.</TD></TR>
 602 </TABLE>
 603 <P>
 604 </LI>
 605
 606 <LI><B>show running-config</B><BR>
 607 This will list the current running configuration.  This is in a format that
 608 can either be pasted into the configuration file, or run directly at the
 609 command line.
 610 <P>
 611 </LI>
 612
 613 <LI><B>show counters</B><BR>
 614 Internally, counters are kept of key values, such as bytes and packets
 615 transferred, as well as function call counters.  This function displays all
 616 these counters, and is probably only useful for debugging.<P>
 617 You can reset these counters by running <EM>clear counters</EM>.
 618 <P>
 619 </LI>
 620
 621 <LI><B>show cluster</B><BR>
 622 Show cluster status.  Shows the cluster state for this server
 623 (Master/Slave), information about known peers and (for slaves) the
 624 master IP address, last packet seen and up-to-date status.<P>
 625 See <A HREF="#Clustering">Clustering</A> for more information.
 626 <P>
 627 </LI>
 628
 629 <LI><B>write memory</B><BR>
 630 This will write the current running configuration to the config file
 631 <B>startup-config</B>, which will be run on a restart.
 632 <P>
 633 </LI>
 634
 635 <LI><B>snoop</B><BR>
 636 You must specify a username, IP address and port.  All packets for the
 637 current session for that username will be forwarded to the given
 638 host/port.  Specify <EM>no snoop username</EM> to disable interception
 639 for the session.<P>
 640
 641 If you want interception to be permanent, you will have to modify the RADIUS
 642 response for the user.  See <A HREF="#Interception">Interception</A>.
 643 <P>
 644 </LI>
 645
 646 <LI><B>throttle</B><BR>
 647 You must specify a username, which will be throttled for the current
 648 session.  Specify <EM>no throttle username</EM> to disable throttling
 649 for the current session.<P>
 650
 651 If you want throttling to be permanent, you will have to modify the
 652 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 653 <P>
 654 </LI>
 655
 656 <LI><B>drop session</B><BR>
 657 This will cleanly disconnect a session.  You must specify a session id, which
 658 you can get from <EM>show session</EM>.  This will send a disconnect message
 659 to the remote end.
 660 <P>
 661 </LI>
 662
 663 <LI><B>drop tunnel</B><BR>
 664 This will cleanly disconnect a tunnel, as well as all sessions on that
 665 tunnel.  It will send a disconnect message for each session individually, and
 666 after 10 seconds it will send a tunnel disconnect message.
 667 <P>
 668 </LI>
 669
 670 <LI><B>uptime</B><BR>
 671 This will show how long the l2tpns process has been running, and the current
 672 bandwidth utilization:
 673 <PRE>
 674 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 675 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 676 </PRE>
 677 The bandwidth line contains 4 sets of values.<BR>
 678 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 679 (user uploads), in mbits/sec.<BR>
 680 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 681 downloads).<BR>
 682 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 683 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 684 <P>
 685 These counters are updated every second.
 686 <P>
 687 </LI>
 688
 689 <LI><B>configure terminal</B><BR>
 690 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 691 The following commands are valid in this mode:<P>
 692 </LI>
 693
 694 <LI><B>load plugin</B><BR>
 695 Load a plugin.  You must specify the plugin name, and it will search in
 696 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 697 <EM>remove plugin</EM>.
 698 <P>
 699 </LI>
 700
 701 <LI><B>set</B><BR>
 702 Set a configuration variable.  You must specify the variable name, and
 703 the value.  If the value contains any spaces, you should quote the
 704 value with double (") or single (') quotes.<P>
 705
 706 You can set any <A HREF="#startup-config">startup-config</A> value in
 707 this way, although some may require a restart to take effect.<P>
 708 </LI>
 709 </UL>
 710
 711 <H3 ID="nsctl">nsctl</H3>
 712
 713 nsctl allows messages to be passed to plugins.<P>
 714
 715 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 716 <STRONG>nsctl</STRONG>(8) for more details.<P>
 717
 718 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 719 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 720
 721 <H3 ID="Signals">Signals</H3>
 722
 723 While the process is running, you can send it a few different signals, using
 724 the kill command.
 725 <PRE>
 726 killall -HUP l2tpns
 727 </PRE>
 728
 729 The signals understood are:
 730 <DL>
 731 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 732 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 733 terminated.  This signal should be used to stop l2tpns on a
 734 <A HREF="#Clustering">cluster node</A> where there are other machines to
 735 continue handling traffic.</DD>
 736 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 737 complete.</DD>
 738 </DL>
 739
 740 <H2 ID="Throttling">Throttling</H2>
 741
 742 l2tpns contains support for slowing down user sessions to whatever speed you
 743 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 744 before this will be activated.<P>
 745
 746 If you wish a session to be throttled permanently, you should set the
 747 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 748 will be handled by the <EM>autothrottle</EM> module.<P>
 749
 750 Otherwise, you can enable and disable throttling an active session using
 751 the <EM>throttle</EM> CLI command.<P>
 752
 753 <H2 ID="Interception">Interception</H2>
 754
 755 You may have to deal with legal requirements to be able to intercept a
 756 user's traffic at any time.  l2tpns allows you to begin and end interception
 757 on the fly, as well as at authentication time.<P>
 758
 759 When a user is being intercepted, a copy of every packet they send and
 760 receive will be sent wrapped in a UDP packet to the IP address and port set
 761 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 762 variables.<P>
 763
 764 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 765
 766 To enable interception on a connected user, use the <EM>snoop username</EM>
 767 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 768 immediately.<P>
 769
 770 If you wish the user to be intercepted whenever they reconnect, you will
 771 need to modify the RADIUS response to include the Vendor-Specific value
 772 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 773 you need to have the <EM>autosnoop</EM> module loaded.<P>
 774
 775 <H2 ID="Authentication">Authentication</H2>
 776
 777 Whenever a session connects, it is not fully set up until authentication is
 778 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 779 request to l2tpns.<P>
 780
 781 This request is sent to the RADIUS server, which will hopefully respond with
 782 Auth-Accept or Auth-Reject.<P>
 783
 784 If Auth-Accept is received, the session is set up and an IP address is
 785 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 786 reply, and that address will be assigned to the client.  It can also include
 787 specific DNS servers, and a Framed-Route if that is required.<P>
 788
 789 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 790 at which point they should disconnect.  The exception to this is when the
 791 walled garden module is loaded, in which case the user still receives the
 792 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 793 should not receive any service.<P>
 794
 795 The RADIUS reply can also contain a Vendor-Specific attribute called
 796 Cisco-Avpair.  This field is a freeform text field that most Cisco
 797 devices understand to contain configuration instructions for the session.  In
 798 the case of l2tpns it is expected to be of the form
 799 <PRE>
 800 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 801 </PRE>
 802
 803 Each key-value pair is separated and passed to any modules loaded.  The
 804 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 805 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 806 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 807 contain:
 808 <PRE>
 809 intercept=yes,throttle=yes
 810 </PRE>
 811
 812 <H2 ID="Plugins">Plugins</H2>
 813
 814 So as to make l2tpns as flexible as possible (I know the core code is pretty
 815 difficult to understand), it includes a plugin API, which you can use to
 816 hook into certain events.<P>
 817
 818 There are a few example modules included - autosnoop, autothrottle and
 819 garden.<P>
 820
 821 When an event happens that has a hook, l2tpns looks for a predefined
 822 function name in every loaded module, and runs them in the order the modules
 823 were loaded.<P>
 824
 825 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 826 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 827 modules should be run for this event.<P>
 828 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 829 no further processing should be done for this event.  <EM>Use this with care.</EM>
 830
 831 Every event function called takes a specific structure named
 832 param_<EM>event</EM>, which varies in content with each event.  The
 833 function name for each event will be <B>plugin_<EM>event</EM></B>,
 834 so for the event <EM>timer</EM>, the function declaration should look like:
 835 <PRE>
 836 int plugin_timer(struct param_timer *data);
 837 </PRE>
 838
 839 A list of the available events follows, with a list of all the fields in the
 840 supplied structure:
 841 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 842 <TABLE CELLSPACING=1 CELLPADDING=3>
 843         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 844         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 845                 <TD>This is called after a RADIUS response has been
 846                 received, but before it has been processed by the
 847                 code.  This will allow you to modify the response in
 848                 some way.
 849                 </TD>
 850                 <TD>
 851                 <DL>
 852                         <DT>t<DD>Tunnel
 853                         <DT>s<DD>Session
 854                         <DT>username
 855                         <DT>password
 856                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 857                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 858                 </DL>
 859                 </TD>
 860         </TR>
 861         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 862                 <TD>This is called after a RADIUS response has been
 863                 received, and the basic checks have been performed.  This
 864                 is what the garden module uses to force authentication
 865                 to be accepted.
 866                 </TD>
 867                 <TD>
 868                 <DL>
 869                         <DT>t<DD>Tunnel
 870                         <DT>s<DD>Session
 871                         <DT>username
 872                         <DT>auth_allowed<DD>This is already set to true or
 873                         false depending on whether authentication has been
 874                         allowed so far.  You can set this to 1 or 0 to force
 875                         allow or disallow authentication
 876                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 877                 </DL>
 878                 </TD>
 879         </TR>
 880         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 881                 <TD>This is called whenever a session receives a
 882                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 883                 seriously slow down the system.</FONT>
 884                 </TD>
 885                 <TD>
 886                 <DL>
 887                         <DT>t<DD>Tunnel
 888                         <DT>s<DD>Session
 889                         <DT>buf<DD>The raw packet data
 890                         <DT>len<DD>The length of buf
 891                 </DL>
 892                 </TD>
 893         </TR>
 894         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 895                 <TD>This is called whenever a session sends a
 896                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 897                 seriously slow down the system.</FONT>
 898                 </TD>
 899                 <TD>
 900                 <DL>
 901                         <DT>t<DD>Tunnel
 902                         <DT>s<DD>Session
 903                         <DT>buf<DD>The raw packet data
 904                         <DT>len<DD>The length of buf
 905                 </DL>
 906                 </TD>
 907         </TR>
 908         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 909                 <TD>This is run every second, no matter what is happening.
 910                 This is called from a signal handler, so make sure anything
 911                 you do is reentrant.
 912                 </TD>
 913                 <TD>
 914                 <DL>
 915                         <DT>time_now<DD>The current unix timestamp
 916                 </DL>
 917                 </TD>
 918         </TR>
 919         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 920                 <TD>This is called after a session is fully set up.  The
 921                 session is now ready to handle traffic.
 922                 </TD>
 923                 <TD>
 924                 <DL>
 925                         <DT>t<DD>Tunnel
 926                         <DT>s<DD>Session
 927                 </DL>
 928                 </TD>
 929         </TR>
 930         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 931                 <TD>This is called when a session is about to be shut down.
 932                 This may be called multiple times for the same session.
 933                 </TD>
 934                 <TD>
 935                 <DL>
 936                         <DT>t<DD>Tunnel
 937                         <DT>s<DD>Session
 938                 </DL>
 939                 </TD>
 940         </TR>
 941         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 942                 <TD>This is called whenever a RADIUS response includes a
 943                 Cisco-Avpair value.  The value is split up into
 944                 <EM>key=value</EM> pairs, and each is processed through all
 945                 modules.
 946                 </TD>
 947                 <TD>
 948                 <DL>
 949                         <DT>t<DD>Tunnel
 950                         <DT>s<DD>Session
 951                         <DT>key
 952                         <DT>value
 953                 </DL>
 954                 </TD>
 955         </TR>
 956         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
 957                 <TD>This is called whenever a RADIUS CoA request is
 958                 received to reset any options to default values before
 959                 the new values are applied.
 960                 </TD>
 961                 <TD>
 962                 <DL>
 963                         <DT>t<DD>Tunnel
 964                         <DT>s<DD>Session
 965                 </DL>
 966                 </TD>
 967         </TR>
 968         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 969                 <TD>This is called in whenever a nsctl packet is received.
 970                 This should handle the packet and form a response if
 971                 required.
 972                 </TD>
 973                 <TD>
 974                 <DL>
 975                         <DT>iam_master<DD>Cluster master status
 976                         <DT>argc<DD>The number of arguments
 977                         <DT>argv<DD>Arguments
 978                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
 979                         <DT>additional<DD>Extended response text
 980                 </DL>
 981                 </TD>
 982         </TR>
 983 </TABLE>
 984 </TD></TR></TABLE>
 985
 986 <H2 ID="WalledGarden">Walled Garden</H2>
 987
 988 Walled Garden is implemented so that you can provide perhaps limited service
 989 to sessions that incorrectly authenticate.<P>
 990
 991 Whenever a session provides incorrect authentication, and the
 992 RADIUS server responds with Auth-Reject, the walled garden module
 993 (if loaded) will force authentication to succeed, but set the flag
 994 <EM>garden</EM> in the session structure, and adds an iptables rule to
 995 the <B>garden_users</B> chain to force all packets for the session's IP
 996 address to traverse the <B>garden</B> chain.<P>
 997
 998 This doesn't <EM>just work</EM>.  To set this all up, you will to
 999 setup the <B>garden</B> nat table with the
1000 <A HREF="#build-garden">build-garden</A> script with rules to limit
1001 user's traffic.  For example, to force all traffic except DNS to be
1002 forwarded to 192.168.1.1, add these entries to your
1003 <EM>build-garden</EM>:
1004 <PRE>
1005 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1006 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1007 </PRE>
1008
1009 l2tpns will add entries to the garden_users chain as appropriate.<P>
1010
1011 You can check the amount of traffic being captured using the following
1012 command:
1013 <PRE>
1014 iptables -t nat -L garden -nvx
1015 </PRE>
1016
1017 <H2 ID="Filtering">Filtering</H2>
1018
1019 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1020 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1021 access-list <I>filter</I> should be applied to traffic from the
1022 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1023 customer.
1024
1025 <H2 ID="Clustering">Clustering</H2>
1026
1027 An l2tpns cluster consists of of one* or more servers configured with
1028 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1029
1030 *A stand-alone server is simply a degraded cluster.<P>
1031
1032 Initially servers come up as cluster slaves, and periodically (every
1033 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1034 containing the start time of the process to the multicast
1035 <B>cluster_address</B>.<P>
1036
1037 A cluster master sends heartbeat rather than ping packets, which
1038 contain those session and tunnel changes since the last heartbeat.<P>
1039
1040 When a slave has not seen a heartbeat within
1041 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1042 examining the list of peers it has seen pings from and determines
1043 which of these and itself is the "best" candidate to be master.
1044 "Best" in this context means the server with the highest uptime (the
1045 highest IP address is used as a tie-breaker in the case of equal
1046 uptimes).<P>
1047
1048 After discovering a master, and determining that it is up-to-date (has
1049 seen an update for all in-use sessions and tunnels from heartbeat
1050 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1051 the <B>bind_address</B> and for all addresses/networks in
1052 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1053 the session state, as well as packets for throttled or gardened
1054 sessions are forwarded to the master for handling.  In addition, byte
1055 counters for session traffic are periodically forwarded.<P>
1056
1057 A master, when determining that it has at least one up-to-date slave
1058 will drop all routes (raising them again if all slaves disappear) and
1059 subsequently handle only packets forwarded to it by the slaves.<P>
1060
1061 <H2 ID="Routing">Routing</H2>
1062 If you are running a single instance, you may simply statically route
1063 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1064 arp).<P>
1065
1066 For a cluster, configure the members as BGP neighbours on your router
1067 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1068 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1069 can use "maximum-paths" (which works for EBGP) and set
1070 <B>as_number</B> to a private value such as 64512.<P>
1071
1072 <H2 ID="Performance">Performance</H2>
1073
1074 Performance is great.<P>
1075
1076 I'd like to include some pretty graphs here that show a linear performance
1077 increase, with no impact by number of connected sessions.<P>
1078
1079 That's really what it looks like.<P>
1080
1081 <BR>
1082 David Parrish<BR>
1083 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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