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