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  25 <H1>L2TPNS Manual</H1>
  26 <OL>
  27     <LI><A HREF="#Overview">Overview</A></LI>
  28     <LI><A HREF="#Installation">Installation</A>
  29         <OL>
  30             <LI><A HREF="#Requirements">Requirements</A></LI>
  31             <LI><A HREF="#Compile">Compile</A></LI>
  32             <LI><A HREF="#Install">Install</A></LI>
  33             <LI><A HREF="#Running">Running</A></LI>
  34         </OL>
  35     </LI>
  36     <LI><A HREF="#Configuration">Configuration</A>
  37         <OL>
  38             <LI><A HREF="#startup-config">startup-config</A></LI>
  39             <LI><A HREF="#users">users</A></LI>
  40             <LI><A HREF="#ip-pool">ip_pool</A></LI>
  41             <LI><A HREF="#build-garden">build-garden</A></LI>
  42         </OL>
  43     </LI>
  44     <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
  45         <OL>
  46             <LI><A HREF="#Command-LineInterface">Command-Line Interface</A></LI>
  47             <LI><A HREF="#nsctl">nsctl</A></LI>
  48             <LI><A HREF="#Signals">Signals</A></LI>
  49         </OL>
  50     </LI>
  51     <LI><A HREF="#Throttling">Throttling</A></LI>
  52     <LI><A HREF="#Interception">Interception</A></LI>
  53     <LI><A HREF="#Authentication">Authentication</A></LI>
  54     <LI><A HREF="#Plugins">Plugins</A></LI>
  55     <LI><A HREF="#WalledGarden">Walled Garden</A></LI>
  56     <LI><A HREF="#Filtering">Filtering</A></LI>
  57     <LI><A HREF="#Clustering">Clustering</A></LI>
  58     <LI><A HREF="#Routing">Routing</A></LI>
  59     <LI><A HREF="#Performance">Performance</A></LI>
  60 </OL>
  61
  62 <H2 ID="Overview">Overview</H2>
  63 l2tpns is half of a complete L2TP implementation.  It supports only the
  64 LNS side of the connection.<P>
  65
  66 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
  67 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection.  l2tpns
  68 implements PPP over L2TP only.<P>
  69
  70 There are a couple of other L2TP implementations, of which <A
  71 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
  72 most popular.  l2tpd also will handle being either end of a tunnel, and
  73 is a lot more configurable than l2tpns.  However, due to the way it works,
  74 it is nowhere near as scalable.<P>
  75
  76 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
  77 and send packets.  Using some packet manipulation it doesn't require a
  78 single interface per connection, as l2tpd does.<P>
  79
  80 This allows it to scale extremely well to very high loads and very high
  81 numbers of connections.<P>
  82
  83 It also has a plugin architecture which allows custom code to be run
  84 during processing.  An example of this is in the walled garden module
  85 included.<P>
  86
  87 <BR>
  88 <EM>Documentation is not my best skill.  If you find any problems
  89 with this document, or if you wish to contribute, please email <A
  90 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
  91
  92 <H2 ID="Installation">Installation</H2>
  93 <H3 ID="Requirements">Requirements</H3>
  94
  95 <OL>
  96 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
  97 compiled in, or as a module.</LI>
  98
  99 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
 100 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
 101 </OL>
 102
 103 <H3 ID="Compile">Compile</H3>
 104
 105 You can generally get away with just running <B>make</B> from the source
 106 directory.  This will compile the daemon, associated tools and any modules
 107 shipped with the distribution.<P>
 108
 109 <H3 ID="Install">Install</H3>
 110
 111 After you have successfully compiled everything, run <B>make
 112 install</B> to install it.  By default, the binaries are installed into
 113 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
 114 modules into <EM>/usr/lib/l2tpns</EM>.<P>
 115
 116 You will definately need to edit the configuration files before you
 117 start.  See the <A HREF="#Configuration">Configuration</A> section for
 118 more information.<P>
 119
 120 <H3 ID="Running">Running</H3>
 121
 122 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it.  It does
 123 not detach to a daemon process, so you should perhaps run it from init.<P>
 124
 125 By default there is no log destination set, so all log messages will go to
 126 stdout.<P>
 127
 128 <H2 ID="Configuration">Configuration</H2>
 129
 130 All configuration of the software is done from the files installed into
 131 /etc/l2tpns.
 132
 133 <H3 ID="startup-config">startup-config</H3>
 134
 135 This is the main configuration file for l2tpns.  The format of the file is a
 136 list of commands that can be run through the command-line interface.  This
 137 file can also be written directly by the l2tpns process if a user runs the
 138 <EM>write memory</EM> command, so any comments will be lost.  However if your
 139 policy is not to write the config by the program, then feel free to comment
 140 the file with a # or ! at the beginning of the line.<P>
 141
 142 A list of the possible configuration directives follows.  Each of these
 143 should be set by a line like:<P>
 144 <PRE>
 145 set configstring "value"
 146 set ipaddress 192.168.1.1
 147 set boolean true
 148 </PRE>
 149
 150 <P>
 151 <UL>
 152 <LI><B>debug</B> (int)<BR>
 153 Sets the level of messages that will be written to the log file.  The value
 154 should be between 0 and 5, with 0 being no debugging, and 5 being the
 155 highest.  A rough description of the levels is:
 156         <OL>
 157         <LI VALUE=0>Critical Errors - Things are probably broken</LI>
 158         <LI>Errors - Things might have gone wrong, but probably will recover</LI>
 159         <LI>Warnings - Just in case you care what is not quite perfect</LI>
 160         <LI>Information - Parameters of control packets</LI>
 161         <LI>Calls - For tracing the execution of the code</LI>
 162         <LI>Packets - Everything, including a hex dump of all packets processed...  probably twice</LI>
 163         </OL><P>
 164 Note that the higher you set the debugging level, the slower the program
 165 will run.  Also, at level 5 a LOT of information will be logged.  This should
 166 only ever be used for working out why it doesn't work at all.
 167 </LI>
 168
 169 <LI><B>log_file</B> (string)<BR>
 170 This will be where all logging and debugging information is written
 171 to.  This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or
 172 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
 173 is any one of the syslog logging facilities, such as local5.
 174 </LI>
 175
 176 <LI><B>pid_file</B> (string)<BR>
 177 If set, the process id will be written to the specified file.  The
 178 value must be an absolute path.
 179 </LI>
 180
 181 <LI><B>l2tp_secret</B> (string)<BR>
 182 The secret used by l2tpns for authenticating tunnel request.  Must be
 183 the same as the LAC, or authentication will fail.  Only actually be
 184 used if the LAC requests authentication.
 185 </LI>
 186
 187 <LI><B>primary_dns</B> (ip address)
 188 <LI><B>secondary_dns</B> (ip address)<BR>
 189 Whenever a PPP connection is established, DNS servers will be sent to the
 190 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 191 one will not be sent.
 192 </LI>
 193
 194 <LI><B>save_state</B> (boolean)<BR>
 195 When l2tpns receives a STGTERM it will write out its current
 196 ip_address_pool, session and tunnel tables to disk prior to exiting to
 197 be re-loaded at startup.  The validity of this data is obviously quite
 198 short and the intent is to allow an sessions to be retained over a
 199 software upgrade.
 200 </LI>
 201
 202 <LI><B>primary_radius</B> (ip address)
 203 <LI><B>secondary_radius</B> (ip address)<BR>
 204 Sets the RADIUS servers used for both authentication and accounting.
 205 If the primary server does not respond, then the secondary RADIUS
 206 server will be tried.<br>
 207 <strong>Note:</strong> in addition to the source IP address and
 208 identifier, the RADIUS server <strong>must</strong> include the source
 209 port when detecting duplicates to supress (in order to cope with a
 210 large number of sessions comming on-line simultaneously l2tpns uses a
 211 set of udp sockets, each with a seperate identifier).
 212 </LI>
 213
 214 <LI><B>primary_radius_port</B> (short)
 215 <LI><B>secondary_radius_port</B> (short)<BR>
 216 Sets the authentication ports for the primary and secondary RADIUS
 217 servers.  The accounting port is one more than the authentication
 218 port.  If no RADIUS ports are given, the authentication port defaults
 219 to 1645, and the accounting port to 1646.
 220 </LI>
 221
 222 <LI><B>radius_accounting</B> (boolean)<BR>
 223 If set to true, then RADIUS accounting packets will be sent.  This
 224 means that a Start record will be sent when the session is
 225 successfully authenticated, and a Stop record will be sent when the
 226 session is closed.
 227 </LI>
 228
 229 <LI><B>radius_secret</B> (string)<BR>
 230 This secret will be used in all RADIUS queries.  If this is not set then
 231 RADIUS queries will fail.
 232 </LI>
 233
 234 <LI><B>bind_address</B> (ip address)<BR>
 235 When the tun interface is created, it is assigned the address
 236 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 237 containing user traffic should be routed via this address if given,
 238 otherwise the primary address of the machine.
 239 </LI>
 240
 241 <LI><B>peer_address</B> (ip address)<BR>
 242 Address to send to clients as the default gateway.
 243 </L1>
 244
 245 <LI><B>send_garp</B> (boolean)<BR>
 246 Determines whether or not to send a gratuitous ARP for the
 247 bind_address when the server is ready to handle traffic (default:
 248 true).<BR>
 249 This value is ignored if BGP is configured.
 250 </LI>
 251
 252 <LI><B>throttle_speed</B> (int)<BR>
 253 Sets the default speed (in kbits/s) which sessions will be limited to.
 254 If this is set to 0, then throttling will not be used at all.  Note:
 255 You can set this by the CLI, but changes will not affect currently
 256 connected users.
 257 </LI>
 258
 259 <LI><B>throttle_buckets</B> (int)<BR>
 260 Number of token buckets to allocate for throttling.  Each throttled
 261 session requires two buckets (in and out).
 262 </LI>
 263
 264 <LI><B>accounting_dir</B> (string)<BR>
 265 If set to a directory, then every 5 minutes the current usage for
 266 every connected use will be dumped to a file in this directory.  Each
 267 file dumped begins with a header, where each line is prefixed by #.
 268 Following the header is a single line for every connected user, fields
 269 separated by a space.<BR> The fields are username, ip, qos,
 270 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 271 2 if the user is throttled.
 272 </LI>
 273
 274 <LI><B>setuid</B> (int)<BR>
 275 After starting up and binding the interface, change UID to this.  This
 276 doesn't work properly.
 277 </LI>
 278
 279 <LI><B>dump_speed</B> (boolean)<BR>
 280 If set to true, then the current bandwidth utilization will be logged every
 281 second.  Even if this is disabled, you can see this information by running
 282 the <EM>uptime</EM> command on the CLI.
 283 </LI>
 284
 285 <LI><B>cleanup_interval</B> (int)<BR>
 286 Interval between regular cleanups (in seconds).
 287 </LI>
 288
 289 <LI><B>multi_read_count</B> (int)<BR>
 290 Number of packets to read off each of the UDP and TUN fds when
 291 returned as readable by select (default:  10).  Avoids incurring the
 292 unnecessary system call overhead of select on busy servers.
 293 </LI>
 294
 295 <LI><B>scheduler_fifo</B> (boolean)<BR>
 296 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 297 causes the kernel to immediately preempt any currently running SCHED_OTHER
 298 (normal) process in favour of l2tpns when it becomes runnable.
 299 Ignored on uniprocessor systems.
 300 </LI>
 301
 302 <LI><B>lock_pages</B> (boolean)<BR>
 303 Keep all pages mapped by the l2tpns process in memory.
 304 </LI>
 305
 306 <LI><B>icmp_rate</B> (int)<BR>
 307 Maximum number of host unreachable ICMP packets to send per second.
 308 </LI>
 309
 310 <LI><B>packet_limit</B> (int><BR>
 311 Maximum number of packets of downstream traffic to be handled each
 312 tenth of a second per session.  If zero, no limit is applied (default:
 313 0).  Intended as a DoS prevention mechanism and not a general
 314 throttling control (packets are dropped, not queued).
 315 </LI>
 316
 317 <LI><B>cluster_address</B> (ip address)<BR>
 318 Multicast cluster address (default:  239.192.13.13).  See the section
 319 on <A HREF="#Clustering">Clustering</A> for more information.
 320 </LI>
 321
 322 <LI><B>cluster_interface</B> (string)<BR>
 323 Interface for cluster packets (default: eth0).
 324 </LI>
 325
 326 <LI><B>cluster_hb_interval</B> (int)<BR>
 327 Interval in tenths of a second between cluster heartbeat/pings.
 328 </LI>
 329
 330 <LI><B>cluster_hb_timeout</B> (int)<BR>
 331 Cluster heartbeat timeout in tenths of a second.  A new master will be
 332 elected when this interval has been passed without seeing a heartbeat
 333 from the master.
 334 </LI>
 335
 336 <LI><B>cluster_master_min_adv</B> (int)<BR>
 337 Determines the minumum number of up to date slaves required before the
 338 master will drop routes (default: 1).
 339 </LI>
 340 </UL>
 341
 342 <P>BGP routing configuration is entered by the command:
 343 The routing configuration section is entered by the command
 344 <DL><DD><B>router bgp</B> <I>as</I></DL>
 345 where <I>as</I> specifies the local AS number.
 346
 347 <P>Subsequent lines prefixed with
 348 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 349 define the attributes of BGP neighhbours.  Valid commands are:
 350 <DL>
 351   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 352   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 353 </DL>
 354
 355 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 356 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 357 <I>hold</I> are the timer values in seconds.
 358
 359 <P>Named access-lists are configured using one of the commands:
 360 <DL>
 361   <DD><B>ip access-list standard</B> <I>name</I>
 362   <DD><B>ip access-list extended</B> <I>name</I>
 363 </DL>
 364
 365 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 366 define the body of the access-list.  Standard access-list syntax:
 367 <DL>
 368   <DD>{<B>permit</B>|<B>deny</B>}
 369     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 370     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 371 </DL>
 372
 373 Extended access-lists:
 374
 375 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 376   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 377     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 378     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 379   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 380     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 381         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 382     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 383         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 384         [<B>fragments</B>]
 385   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 386     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 387         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 388     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 389         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 390         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 391             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 392             ...|<B>fragments</B>]
 393 </DIV>
 394
 395 <H3 ID="users">users</H3>
 396
 397 Usernames and passwords for the command-line interface are stored in
 398 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 399 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 400 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 401 plain text by the prefix <B>{crypt}</B>.<P>
 402
 403 The username <B>enable</B> has a special meaning and is used to set
 404 the enable password.<P>
 405
 406 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 407 port 23 will be allowed access without a username / password.<P>
 408
 409 <H3 ID="ip-pool">ip_pool</H3>
 410
 411 This file is used to configure the IP address pool which user
 412 addresses are assigned from.  This file should contain either an IP
 413 address or a CIDR network per line.  e.g.:<P>
 414
 415 <PRE>
 416     192.168.1.1
 417     192.168.1.2
 418     192.168.1.3
 419     192.168.4.0/24
 420     172.16.0.0/16
 421     10.0.0.0/8
 422 </PRE>
 423
 424 Keep in mind that l2tpns can only handle 65535 connections per
 425 process, so don't put more than 65535 IP addresses in the
 426 configuration file.  They will be wasted.
 427
 428 <H3 ID="build-garden">build-garden</H3>
 429
 430 The garden plugin on startup creates a NAT table called "garden" then
 431 sources the <B>build-garden</B> script to populate that table.  All
 432 packets from gardened users will be sent through this table.  Example:
 433
 434 <PRE>
 435     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 436     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 437     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 438     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 439     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 440     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 441     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 442     iptables -t nat -A garden -p icmp -j ACCEPT
 443     iptables -t nat -A garden -j DROP
 444 </PRE>
 445
 446 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 447
 448 A running l2tpns process can be controlled in a number of ways.  The primary
 449 method of control is by the Command-Line Interface (CLI).<P>
 450
 451 You can also remotely send commands to modules via the nsctl client
 452 provided.<P>
 453
 454 Also, there are a number of signals that l2tpns understands and takes action
 455 when it receives them.
 456
 457 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 458
 459 You can access the command line interface by telnet'ing to port 23.
 460 There is no IP address restriction, so it's a good idea to firewall
 461 this port off from anyone who doesn't need access to it.  See
 462 <A HREF="#users">users</A> for information on restricting access based
 463 on a username and password.<P>
 464
 465 The CLI gives you real-time control over almost everything in
 466 the process.  The interface is designed to look like a Cisco
 467 device, and supports things like command history, line editing and
 468 context sensitive help.  This is provided by linking with the
 469 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 470 library.  Some general documentation of the interface is
 471 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 472 here</A>.<P>
 473
 474 After you have connected to the telnet port (and perhaps logged in), you
 475 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 476
 477 Enter <EM>help</EM> to get a list of possible commands.  A brief
 478 overview of the more important commands follows:
 479
 480 <UL>
 481 <LI><B>show session</B><BR>
 482 Without specifying a session ID, this will list all tunnels currently
 483 connected.  If you specify a session ID, you will be given all
 484 information on a single tunnel.  Note that the full session list can
 485 be around 185 columns wide, so you should probably use a wide terminal
 486 to see the list properly.<P>
 487 The columns listed in the overview are:
 488 <TABLE>
 489         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 490         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 491         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 492         authentication.  If this is *, then LCP authentication has not
 493         completed.</TD></TR>
 494         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 495         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 496         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 497         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 498         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 499         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 500         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 501         trapped in the walled garden.  This field is present even if the
 502         garden module is not loaded.</TD></TR>
 503         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 504         session started</TD></TR>
 505         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 506         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 507         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 508         detected on the session</TD></TR>
 509         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 510         connected to.</TD></TR>
 511         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 512         provided during the session setup.  This field is generated by the
 513         LAC.</TD></TR>
 514 </TABLE>
 515 <P>
 516 </LI>
 517
 518 <LI><B>show users</B><BR>
 519 With no arguments, display a list of currently connected users.  If an
 520 argument is given, the session details for the given username are
 521 displayed.
 522 </LI>
 523
 524 <LI><B>show tunnel</B><BR>
 525 This will show all the open tunnels in a summary, or detail on a single
 526 tunnel if you give a tunnel id.<P>
 527 The columns listed in the overview are:
 528 <TABLE>
 529         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 530         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 531         provided by the LAC.  This has no relation to DNS, it is just
 532         a text field.</TD></TR>
 533         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 534         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 535         Opening</TD></TR>
 536         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 537         tunnel</TD></TR>
 538 </TABLE>
 539 <P>
 540 </LI>
 541
 542 <LI><B>show pool</B><BR>
 543 Displays the current IP address pool allocation.  This will only display
 544 addresses that are in use, or are reserved for re-allocation to a
 545 disconnected user.<P>
 546 If an address is not currently in use, but has been used, then in the User
 547 column the username will be shown in square brackets, followed by the time
 548 since the address was used:
 549 <PRE>
 550 IP Address      Used  Session User
 551 192.168.100.6     N           [joe.user] 1548s
 552 </PRE>
 553 <P>
 554 </LI>
 555
 556 <LI><B>show radius</B><BR>
 557 Show a summary of the in-use RADIUS sessions.  This list should not be very
 558 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 559 columns listed are:
 560 <TABLE>
 561         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 562         sent in the packet to the RADIUS server for identification.</TD></TR>
 563         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 564         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 565         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 566         request is associated with</TD></TR>
 567         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 568         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 569         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 570         discarded after 3 retries.</TD></TR>
 571 </TABLE>
 572 <P>
 573 </LI>
 574
 575 <LI><B>show running-config</B><BR>
 576 This will list the current running configuration.  This is in a format that
 577 can either be pasted into the configuration file, or run directly at the
 578 command line.
 579 <P>
 580 </LI>
 581
 582 <LI><B>show counters</B><BR>
 583 Internally, counters are kept of key values, such as bytes and packets
 584 transferred, as well as function call counters.  This function displays all
 585 these counters, and is probably only useful for debugging.<P>
 586 You can reset these counters by running <EM>clear counters</EM>.
 587 <P>
 588 </LI>
 589
 590 <LI><B>show cluster</B><BR>
 591 Show cluster status.  Shows the cluster state for this server
 592 (Master/Slave), information about known peers and (for slaves) the
 593 master IP address, last packet seen and up-to-date status.<P>
 594 See <A HREF="#Clustering">Clustering</A> for more information.
 595 <P>
 596 </LI>
 597
 598 <LI><B>write memory</B><BR>
 599 This will write the current running configuration to the config file
 600 <B>startup-config</B>, which will be run on a restart.
 601 <P>
 602 </LI>
 603
 604 <LI><B>snoop</B><BR>
 605 You must specify a username, IP address and port.  All packets for the
 606 current session for that username will be forwarded to the given
 607 host/port.  Specify <EM>no snoop username</EM> to disable interception
 608 for the session.<P>
 609
 610 If you want interception to be permanent, you will have to modify the RADIUS
 611 response for the user.  See <A HREF="#Interception">Interception</A>.
 612 <P>
 613 </LI>
 614
 615 <LI><B>throttle</B><BR>
 616 You must specify a username, which will be throttled for the current
 617 session.  Specify <EM>no throttle username</EM> to disable throttling
 618 for the current session.<P>
 619
 620 If you want throttling to be permanent, you will have to modify the
 621 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 622 <P>
 623 </LI>
 624
 625 <LI><B>drop session</B><BR>
 626 This will cleanly disconnect a session.  You must specify a session id, which
 627 you can get from <EM>show session</EM>.  This will send a disconnect message
 628 to the remote end.
 629 <P>
 630 </LI>
 631
 632 <LI><B>drop tunnel</B><BR>
 633 This will cleanly disconnect a tunnel, as well as all sessions on that
 634 tunnel.  It will send a disconnect message for each session individually, and
 635 after 10 seconds it will send a tunnel disconnect message.
 636 <P>
 637 </LI>
 638
 639 <LI><B>uptime</B><BR>
 640 This will show how long the l2tpns process has been running, and the current
 641 bandwidth utilization:
 642 <PRE>
 643 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 644 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 645 </PRE>
 646 The bandwidth line contains 4 sets of values.<BR>
 647 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 648 (user uploads), in mbits/sec.<BR>
 649 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 650 downloads).<BR>
 651 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 652 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 653 <P>
 654 These counters are updated every second.
 655 <P>
 656 </LI>
 657
 658 <LI><B>configure terminal</B><BR>
 659 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 660 The following commands are valid in this mode:<P>
 661 </LI>
 662
 663 <LI><B>load plugin</B><BR>
 664 Load a plugin.  You must specify the plugin name, and it will search in
 665 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 666 <EM>remove plugin</EM>.
 667 <P>
 668 </LI>
 669
 670 <LI><B>set</B><BR>
 671 Set a configuration variable.  You must specify the variable name, and
 672 the value.  If the value contains any spaces, you should quote the
 673 value with double (") or single (') quotes.<P>
 674
 675 You can set any <A HREF="#startup-config">startup-config</A> value in
 676 this way, although some may require a restart to take effect.<P>
 677 </LI>
 678 </UL>
 679
 680 <H3 ID="nsctl">nsctl</H3>
 681
 682 nsctl allows messages to be passed to plugins.<P>
 683
 684 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 685 <STRONG>nsctl</STRONG>(8) for more details.<P>
 686
 687 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 688 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 689
 690 <H3 ID="Signals">Signals</H3>
 691
 692 While the process is running, you can send it a few different signals, using
 693 the kill command.
 694 <PRE>
 695 killall -HUP l2tpns
 696 </PRE>
 697
 698 The signals understood are:
 699 <UL>
 700 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
 701 <LI>SIGTERM / SIGINT - Shut down for a restart.  This will dump the current
 702 state to disk (if <EM>save_state</EM> is set to true).  Upon restart, the
 703 process will read this saved state to resume active sessions.<P>
 704 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 705 every active session and tunnel before shutting down.  This is a good idea
 706 when upgrading the code, as no sessions will be left with the remote end
 707 thinking they are open.</LI>
 708 </UL>
 709
 710 <H2 ID="Throttling">Throttling</H2>
 711
 712 l2tpns contains support for slowing down user sessions to whatever speed you
 713 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 714 before this will be activated.<P>
 715
 716 If you wish a session to be throttled permanently, you should set the
 717 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 718 will be handled by the <EM>autothrottle</EM> module.<P>
 719
 720 Otherwise, you can enable and disable throttling an active session using
 721 the <EM>throttle</EM> CLI command.<P>
 722
 723 <H2 ID="Interception">Interception</H2>
 724
 725 You may have to deal with legal requirements to be able to intercept a
 726 user's traffic at any time.  l2tpns allows you to begin and end interception
 727 on the fly, as well as at authentication time.<P>
 728
 729 When a user is being intercepted, a copy of every packet they send and
 730 receive will be sent wrapped in a UDP packet to the IP address and port set
 731 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 732 variables.<P>
 733
 734 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 735
 736 To enable interception on a connected user, use the <EM>snoop username</EM>
 737 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 738 immediately.<P>
 739
 740 If you wish the user to be intercepted whenever they reconnect, you will
 741 need to modify the RADIUS response to include the Vendor-Specific value
 742 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 743 you need to have the <EM>autosnoop</EM> module loaded.<P>
 744
 745 <H2 ID="Authentication">Authentication</H2>
 746
 747 Whenever a session connects, it is not fully set up until authentication is
 748 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 749 request to l2tpns.<P>
 750
 751 This request is sent to the RADIUS server, which will hopefully respond with
 752 Auth-Accept or Auth-Reject.<P>
 753
 754 If Auth-Accept is received, the session is set up and an IP address is
 755 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 756 reply, and that address will be assigned to the client.  It can also include
 757 specific DNS servers, and a Framed-Route if that is required.<P>
 758
 759 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 760 at which point they should disconnect.  The exception to this is when the
 761 walled garden module is loaded, in which case the user still receives the
 762 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 763 should not receive any service.<P>
 764
 765 The RADIUS reply can also contain a Vendor-Specific attribute called
 766 Cisco-Avpair.  This field is a freeform text field that most Cisco
 767 devices understand to contain configuration instructions for the session.  In
 768 the case of l2tpns it is expected to be of the form
 769 <PRE>
 770 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 771 </PRE>
 772
 773 Each key-value pair is separated and passed to any modules loaded.  The
 774 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 775 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 776 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 777 contain:
 778 <PRE>
 779 intercept=yes,throttle=yes
 780 </PRE>
 781
 782 <H2 ID="Plugins">Plugins</H2>
 783
 784 So as to make l2tpns as flexible as possible (I know the core code is pretty
 785 difficult to understand), it includes a plugin API, which you can use to
 786 hook into certain events.<P>
 787
 788 There are a few example modules included - autosnoop, autothrottle and
 789 garden.<P>
 790
 791 When an event happens that has a hook, l2tpns looks for a predefined
 792 function name in every loaded module, and runs them in the order the modules
 793 were loaded.<P>
 794
 795 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 796 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 797 modules should be run for this event.<P>
 798 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 799 no further processing should be done for this event.  <EM>Use this with care.</EM>
 800
 801 Every event function called takes a specific structure named
 802 param_<EM>event</EM>, which varies in content with each event.  The
 803 function name for each event will be <B>plugin_<EM>event</EM></B>,
 804 so for the event <EM>timer</EM>, the function declaration should look like:
 805 <PRE>
 806 int plugin_timer(struct param_timer *data);
 807 </PRE>
 808
 809 A list of the available events follows, with a list of all the fields in the
 810 supplied structure:
 811 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 812 <TABLE CELLSPACING=1 CELLPADDING=3>
 813         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 814         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 815                 <TD>This is called after a RADIUS response has been
 816                 received, but before it has been processed by the
 817                 code.  This will allow you to modify the response in
 818                 some way.
 819                 </TD>
 820                 <TD>
 821                 <UL>
 822                         <LI>t - Tunnel ID</LI>
 823                         <LI>s - Session ID</LI>
 824                         <LI>username</LI>
 825                         <LI>password</LI>
 826                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 827                         <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
 828                 </UL>
 829                 </TD>
 830         </TR>
 831         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 832                 <TD>This is called after a RADIUS response has been
 833                 received, and the basic checks have been performed.  This
 834                 is what the garden module uses to force authentication
 835                 to be accepted.
 836                 </TD>
 837                 <TD>
 838                 <UL>
 839                         <LI>t - Tunnel ID</LI>
 840                         <LI>s - Session ID</LI>
 841                         <LI>username</LI>
 842                         <LI>auth_allowed - This is already set to true or
 843                         false depending on whether authentication has been
 844                         allowed so far.  You can set this to 1 or 0 to force
 845                         allow or disallow authentication</LI>
 846                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 847                 </UL>
 848                 </TD>
 849         </TR>
 850         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 851                 <TD>This is called whenever a session receives a
 852                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 853                 seriously slow down the system.</FONT>
 854                 </TD>
 855                 <TD>
 856                 <UL>
 857                         <LI>t - Tunnel ID</LI>
 858                         <LI>s - Session ID</LI>
 859                         <LI>buf - The raw packet data</LI>
 860                         <LI>len - The length of buf</LI>
 861                 </UL>
 862                 </TD>
 863         </TR>
 864         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 865                 <TD>This is called whenever a session sends a
 866                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 867                 seriously slow down the system.</FONT>
 868                 </TD>
 869                 <TD>
 870                 <UL>
 871                         <LI>t - Tunnel ID</LI>
 872                         <LI>s - Session ID</LI>
 873                         <LI>buf - The raw packet data</LI>
 874                         <LI>len - The length of buf</LI>
 875                 </UL>
 876                 </TD>
 877         </TR>
 878         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 879                 <TD>This is run every second, no matter what is happening.
 880                 This is called from a signal handler, so make sure anything
 881                 you do is reentrant.
 882                 </TD>
 883                 <TD>
 884                 <UL>
 885                         <LI>time_now - The current unix timestamp</LI>
 886                 </UL>
 887                 </TD>
 888         </TR>
 889         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 890                 <TD>This is called after a session is fully set up.  The
 891                 session is now ready to handle traffic.
 892                 </TD>
 893                 <TD>
 894                 <UL>
 895                         <LI>t - Tunnel ID</LI>
 896                         <LI>s - Session ID</LI>
 897                 </UL>
 898                 </TD>
 899         </TR>
 900         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 901                 <TD>This is called when a session is about to be shut down.
 902                 This may be called multiple times for the same session.
 903                 </TD>
 904                 <TD>
 905                 <UL>
 906                         <LI>t - Tunnel ID</LI>
 907                         <LI>s - Session ID</LI>
 908                 </UL>
 909                 </TD>
 910         </TR>
 911         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 912                 <TD>This is called whenever a RADIUS response includes a
 913                 Cisco-Avpair value.  The value is split up into
 914                 <EM>key=value</EM> pairs, and each is processed through all
 915                 modules.
 916                 </TD>
 917                 <TD>
 918                 <UL>
 919                         <LI>t - Tunnel ID</LI>
 920                         <LI>s - Session ID</LI>
 921                         <LI>key</LI>
 922                         <LI>value</LI>
 923                 </UL>
 924                 </TD>
 925         </TR>
 926         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 927                 <TD>This is called in whenever a nsctl packet is received.
 928                 This should handle the packet and form a response if
 929                 required.
 930                 </TD>
 931                 <TD>
 932                 <UL>
 933                         <LI>buf - The raw packet data</LI>
 934                         <LI>l - The raw packet data length</LI>
 935                         <LI>source_ip - Where the request came from</LI>
 936                         <LI>source_port - Where the request came from</LI>
 937                         <LI>response - Allocate a buffer and put your response in here</LI>
 938                         <LI>response_length - Length of response</LI>
 939                         <LI>send_response - true or false whether a response
 940                         should be sent.  If you set this to true, you must
 941                         allocate a response buffer.</LI>
 942                         <LI>type - Type of request (see nsctl.c)</LI>
 943                         <LI>id - ID of request</LI>
 944                         <LI>data - I'm really not sure</LI>
 945                         <LI>data_length - Length of data</LI>
 946                 </UL>
 947                 </TD>
 948         </TR>
 949 </TABLE>
 950 </TD></TR></TABLE>
 951
 952 <H2 ID="WalledGarden">Walled Garden</H2>
 953
 954 Walled Garden is implemented so that you can provide perhaps limited service
 955 to sessions that incorrectly authenticate.<P>
 956
 957 Whenever a session provides incorrect authentication, and the
 958 RADIUS server responds with Auth-Reject, the walled garden module
 959 (if loaded) will force authentication to succeed, but set the flag
 960 <EM>garden</EM> in the session structure, and adds an iptables rule to
 961 the <B>garden_users</B> chain to force all packets for the session's IP
 962 address to traverse the <B>garden</B> chain.<P>
 963
 964 This doesn't <EM>just work</EM>.  To set this all up, you will to
 965 setup the <B>garden</B> nat table with the
 966 <A HREF="#build-garden">build-garden</A> script with rules to limit
 967 user's traffic.  For example, to force all traffic except DNS to be
 968 forwarded to 192.168.1.1, add these entries to your
 969 <EM>build-garden</EM>:
 970 <PRE>
 971 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
 972 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
 973 </PRE>
 974
 975 l2tpns will add entries to the garden_users chain as appropriate.<P>
 976
 977 You can check the amount of traffic being captured using the following
 978 command:
 979 <PRE>
 980 iptables -t nat -L garden -nvx
 981 </PRE>
 982
 983 <H2 ID="Filtering">Filtering</H2>
 984
 985 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
 986 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
 987 access-list <I>filter</I> should be applied to traffic from the
 988 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
 989 customer.
 990
 991 <H2 ID="Clustering">Clustering</H2>
 992
 993 An l2tpns cluster consists of of one* or more servers configured with
 994 the same configuration, notably the multicast <B>cluster_address</B>.<P>
 995
 996 *A stand-alone server is simply a degraded cluster.<P>
 997
 998 Initially servers come up as cluster slaves, and periodically (every
 999 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1000 containing the start time of the process to the multicast
1001 <B>cluster_address</B>.<P>
1002
1003 A cluster master sends heartbeat rather than ping packets, which
1004 contain those session and tunnel changes since the last heartbeat.<P>
1005
1006 When a slave has not seen a heartbeat within
1007 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1008 examining the list of peers it has seen pings from and determines
1009 which of these and itself is the "best" candidate to be master.
1010 "Best" in this context means the server with the highest uptime (the
1011 highest IP address is used as a tie-breaker in the case of equal
1012 uptimes).<P>
1013
1014 After discovering a master, and determining that it is up-to-date (has
1015 seen an update for all in-use sessions and tunnels from heartbeat
1016 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1017 the <B>bind_address</B> and for all addresses/networks in
1018 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1019 the session state, as well as packets for throttled or gardened
1020 sessions are forwarded to the master for handling.  In addition, byte
1021 counters for session traffic are periodically forwarded.<P>
1022
1023 A master, when determining that it has at least one up-to-date slave
1024 will drop all routes (raising them again if all slaves disappear) and
1025 subsequently handle only packets forwarded to it by the slaves.<P>
1026
1027 <H2 ID="Routing">Routing</H2>
1028 If you are running a single instance, you may simply statically route
1029 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1030 arp).<P>
1031
1032 For a cluster, configure the members as BGP neighbours on your router
1033 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1034 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1035 can use "maximum-paths" (which works for EBGP) and set
1036 <B>as_number</B> to a private value such as 64512.<P>
1037
1038 <H2 ID="Performance">Performance</H2>
1039
1040 Performance is great.<P>
1041
1042 I'd like to include some pretty graphs here that show a linear performance
1043 increase, with no impact by number of connected sessions.<P>
1044
1045 That's really what it looks like.<P>
1046
1047 <BR>
1048 David Parrish<BR>
1049 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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