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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="#Walled Garden">Walled Garden</A></LI>
  56     <LI><A HREF="#Clustering">Clustering</A></LI>
  57     <LI><A HREF="#Routing">Routing</A></LI>
  58     <LI><A HREF="#Performance">Performance</A></LI>
  59 </OL>
  60
  61 <H2 ID="Overview">Overview</H2>
  62 l2tpns is half of a complete L2TP implementation.  It supports only the
  63 LNS side of the connection.<P>
  64
  65 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
  66 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection.  l2tpns
  67 implements PPP over L2TP only.<P>
  68
  69 There are a couple of other L2TP imlementations, of which <A
  70 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
  71 most popular.  l2tpd also will handle being either end of a tunnel, and
  72 is a lot more configurable than l2tpns.  However, due to the way it works,
  73 it is nowhere near as scalable.<P>
  74
  75 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
  76 and send packets.  Using some packet manipulation it doesn't require a
  77 single interface per connection, as l2tpd does.<P>
  78
  79 This allows it to scale extremely well to very high loads and very high
  80 numbers of connections.<P>
  81
  82 It also has a plugin architecture which allows custom code to be run
  83 during processing.  An example of this is in the walled garden module
  84 included.<P>
  85
  86 <BR>
  87 <EM>Documentation is not my best skill.  If you find any problems
  88 with this document, or if you wish to contribute, please email <A
  89 HREF="mailto:david@dparrish.com?subject=L2TPNS+Documentation">david@dparrish.com</A>.</EM><P>
  90
  91 <H2 ID="Installation">Installation</H2>
  92 <H3 ID="Requirements">Requirements</H3>
  93
  94 <OL>
  95 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
  96 compiled in, or as a module.</LI>
  97
  98 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
  99 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
 100 </OL>
 101
 102 <H3 ID="Compile">Compile</H3>
 103
 104 You can generally get away with just running <B>make</B> from the source
 105 directory.  This will compile the daemon, associated tools and any modules
 106 shipped with the distribution.<P>
 107
 108 <H3 ID="Install">Install</H3>
 109
 110 After you have successfully compiled everything, run <B>make
 111 install</B> to install it.  By default, the binaries are installed into
 112 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
 113 modules into <EM>/usr/lib/l2tpns</EM>.<P>
 114
 115 You will definately need to edit the configuration files before you
 116 start.  See the <A HREF="#Configuration">Configuration</A> section for
 117 more information.<P>
 118
 119 <H3 ID="Running">Running</H3>
 120
 121 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it.  It does
 122 not detach to a daemon process, so you should perhaps run it from init.<P>
 123
 124 By default there is no log destination set, so all log messages will go to
 125 stdout.<P>
 126
 127 <H2 ID="Configuration">Configuration</H2>
 128
 129 All configuration of the software is done from the files installed into
 130 /etc/l2tpns.
 131
 132 <H3 ID="startup-config">startup-config</H3>
 133
 134 This is the main configuration file for l2tpns.  The format of the file is a
 135 list of commands that can be run through the command-line interface.  This
 136 file can also be written directly by the l2tpns process if a user runs the
 137 <EM>write memory</EM> command, so any comments will be lost.  However if your
 138 policy is not to write the config by the program, then feel free to comment
 139 the file with a # or ! at the beginning of the line.<P>
 140
 141 A list of the possible configuration directives follows.  Each of these
 142 should be set by a line like:<P>
 143 <PRE>
 144 set configstring "value"
 145 set ipaddress 192.168.1.1
 146 set boolean true
 147 </PRE>
 148
 149 <UL>
 150 <LI><B>debug</B> (int)<BR>
 151 Sets the level of messages that will be written to the log file.  The value
 152 should be between 0 and 5, with 0 being no debugging, and 5 being the
 153 highest.  A rough description of the levels is:
 154         <OL>
 155         <LI VALUE=0>Critical Errors - Things are probably broken</LI>
 156         <LI>Errors - Things might have gone wrong, but probably will recover</LI>
 157         <LI>Warnings - Just in case you care what is not quite perfect</LI>
 158         <LI>Information - Parameters of control packets</LI>
 159         <LI>Calls - For tracing the execution of the code</LI>
 160         <LI>Packets - Everything, including a hex dump of all packets processed...  probably twice</LI>
 161         </OL><P>
 162 Note that the higher you set the debugging level, the slower the program
 163 will run.  Also, at level 5 a LOT of information will be logged.  This should
 164 only ever be used for working out why it doesn't work at all.
 165 <P>
 166 </LI>
 167
 168 <LI><B>log_file</B> (string)<BR>
 169 This will be where all logging and debugging information is written
 170 to.  This can be either a filename, such as <EM>/var/log/l2tpns</EM>, or
 171 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
 172 is any one of the syslog logging facilities, such as local5.
 173 <P>
 174 </LI>
 175
 176 <LI><B>l2tp_secret</B> (string)<BR>
 177 This sets the string that l2tpns will use for authenticating tunnel request.
 178 This must be the same as the LAC, or authentication will fail.  This will
 179 only actually be used if the LAC requests authentication.
 180 <P>
 181 </LI>
 182
 183 <LI><B>primary_dns</B> (ip address)
 184 <LI><B>secondary_dns</B> (ip address)<BR>
 185 Whenever a PPP connection is established, DNS servers will be sent to the
 186 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 187 one will not be sent.
 188 <P>
 189 </LI>
 190
 191 <LI><B>save_state</B> (boolean)<BR>
 192 When l2tpns receives a STGTERM it will write out its current
 193 ip_address_pool, session and tunnel tables to disk prior to exiting to
 194 be re-loaded at startup.  The validity of this data is obviously quite
 195 short and the intent is to allow an sessions to be retained over a
 196 software upgrade.
 197 <P>
 198 </LI>
 199
 200 <LI><B>primary_radius</B> (ip address)
 201 <LI><B>secondary_radius</B> (ip address)<BR>
 202 This sets the radius servers used for both authentication and
 203 accounting.  If the primary server does not respond, then the
 204 secondary radius server will be tried.
 205 <P>
 206 </LI>
 207
 208 <LI><B>primary_radius_port</B> (short)
 209 <LI><B>secondary_radius_port</B> (short)<BR>
 210 This sets the authentication ports for the primary and secondary
 211 radius servers.  The accounting port is one more than the authentication
 212 port.  If no radius ports are given, the authentication port defaults to 1645,
 213 and the accounting port to 1646.
 214 <P>
 215 </LI>
 216
 217 <LI><B>radius_accounting</B> (boolean)<BR>
 218 If set to true, then radius accounting packets will be sent.  This
 219 means that a Start record will be sent when the session is
 220 successfully authenticated, and a Stop record will be sent when the
 221 session is closed.
 222 <P>
 223 </LI>
 224
 225 <LI><B>radius_secret</B> (string)<BR>
 226 This secret will be used in all radius queries.  If this is not set then
 227 radius queries will fail.
 228 <P>
 229 </LI>
 230
 231 <LI><B>bind_address</B> (ip address)<BR>
 232 When the tun interface is created, it is assigned the address
 233 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 234 containing user traffic should be routed via this address if given,
 235 otherwise the primary address of the machine.
 236 <P>
 237 </LI>
 238
 239 <LI><B>send_garp</B> (boolean)<BR>
 240 Determines whether or not to send a gratuitous ARP for the
 241 bind_address when the server is ready to handle traffic (default:
 242 true).<BR>
 243 This value is ignored if BGP is configured.
 244 <P>
 245 </LI>
 246
 247 <LI><B>throttle_speed</B> (int)<BR>
 248 Sets the speed (in kbits/s) which sessions will be limited to.  If this is
 249 set to 0, then throttling will not be used at all.  Note: You can set this by
 250 the CLI, but changes will not affect currently connected users.
 251 <P>
 252 </LI>
 253
 254 <LI><B>accounting_dir</B> (string)<BR>
 255 If set to a directory, then every 5 minutes the current usage for
 256 every connected use will be dumped to a file in this directory.  Each
 257 file dumped begins with a header, where each line is prefixed by #.
 258 Following the header is a single line for every connected user, fields
 259 separated by a space.<BR> The fields are username, ip, qos,
 260 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 261 2 if the user is throttled.
 262 <P>
 263 </LI>
 264
 265 <LI><B>setuid</B> (int)<BR>
 266 After starting up and binding the interface, change UID to this.  This
 267 doesn't work properly.
 268 <P>
 269 </LI>
 270
 271 <LI><B>dump_speed</B> (boolean)<BR>
 272 If set to true, then the current bandwidth utilization will be logged every
 273 second.  Even if this is disabled, you can see this information by running
 274 the <EM>uptime</EM> command on the CLI.
 275 <P>
 276 </LI>
 277
 278 <LI><B>cleanup_interval</B> (int)<BR>
 279 Interval between regular cleanups (in seconds).
 280 <P>
 281 </LI>
 282
 283 <LI><B>multi_read_count</B> (int)<BR>
 284 Number of packets to read off each of the UDP and TUN fds when
 285 returned as readable by select (default:  10).  Avoids incurring the
 286 unnecessary system call overhead of select on busy servers.
 287 <P>
 288 </LI>
 289
 290 <LI><B>scheduler_fifo</B> (boolean)<BR>
 291 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 292 causes the kernel to immediately preempt any currently SCHED_OTHER
 293 (normal) process in favour of l2tpns when it becomes runnable.
 294 Ignored on uniprocessor systems.
 295 <P>
 296 </LI>
 297
 298 <LI><B>lock_pages</B> (boolean)<BR>
 299 Keep all pages mapped by the l2tpns process in memory.
 300 <P>
 301 </LI>
 302
 303 <LI><B>icmp_rate</B> (int)<BR>
 304 Maximum number of host unreachable icmp packets to send per second.
 305 <P>
 306 </LI>
 307
 308 <LI><B>cluster_address</B> (ip address)<BR>
 309 Multicast cluster address (default:  239.192.13.13).  See the section
 310 on <A HREF="#Clustering">Clustering</A> for more information.
 311 <P>
 312 </LI>
 313
 314 <LI><B>cluster_interface</B> (string)<BR>
 315 Interface for cluster packets (default: eth0).
 316 <P>
 317 </LI>
 318
 319 <LI><B>cluster_hb_interval</B> (int)<BR>
 320 Interval in tenths of a second between cluster heartbeat/pings.
 321 <P>
 322 </LI>
 323
 324 <LI><B>cluster_hb_timeout</B> (int)<BR>
 325 Cluster heartbeat timeout in tenths of a second.  A new master will be
 326 elected when this interval has been passed without seeing a heartbeat
 327 from the master.
 328 <P>
 329 </LI>
 330
 331 <LI><B>as_number</B> (int)<BR>
 332 Defines the local AS number for BGP (see <A HREF="#Routing">Routing</A>).
 333 <P>
 334 </LI>
 335
 336 <LI><B>bgp_peer1</B> (string)
 337 <LI><B>bgp_peer1_as</B> (int)
 338 <LI><B>bgp_peer2</B> (string)
 339 <LI><B>bgp_peer2_as</B> (int)<BR>
 340 <P>
 341 DNS name (or IP) and AS number of BGP peers.
 342 </LI>
 343 </UL>
 344
 345 <H3 ID="users">users</H3>
 346
 347 Usernames and passwords for the command-line interface are stored in
 348 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 349 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 350 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 351 plain text by the prefix <B>{crypt}</B>.<P>
 352
 353 The username <B>enable</B> has a special meaning and is used to set
 354 the enable password.<P>
 355
 356 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 357 port 23 will be allowed access without a username / password.<P>
 358
 359 <H3 ID="ip-pool">ip_pool</H3>
 360
 361 This file is used to configure the IP address pool which user
 362 addresses are assigned from.  This file should contain either an IP
 363 address or a CIDR network per line.  e.g.:<P>
 364
 365 <PRE>
 366     192.168.1.1
 367     192.168.1.2
 368     192.168.1.3
 369     192.168.4.0/24
 370     172.16.0.0/16
 371     10.0.0.0/8
 372 </PRE>
 373
 374 Keep in mind that l2tpns can only handle 65535 connections per
 375 process, so don't put more than 65535 IP addresses in the
 376 configuration file.  They will be wasted.
 377
 378 <H3 ID="build-garden">build-garden</H3>
 379
 380 The garden plugin on startup creates a NAT table called "garden" then
 381 sources the <B>build-garden</B> script to populate that table.  All
 382 packets from gardened users will be sent through this table.  Example:
 383
 384 <PRE>
 385     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 386     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 387     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 388     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 389     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 390     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 391     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 392     iptables -t nat -A garden -p icmp -j ACCEPT
 393     iptables -t nat -A garden -j DROP
 394 </PRE>
 395
 396 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 397
 398 A running l2tpns process can be controlled in a number of ways.  The primary
 399 method of control is by the Command-Line Interface (CLI).<P>
 400
 401 You can also remotely send commands to modules via the nsctl client
 402 provided.  This currently only works with the walled garden module, but
 403 modification is trivial to support other modules.<P>
 404
 405 Also, there are a number of signals that l2tpns understands and takes action
 406 when it receives them.
 407
 408 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 409
 410 You can access the command line interface by telnet'ing to port 23.
 411 There is no IP address restriction, so it's a good idea to firewall
 412 this port off from anyone who doesn't need access to it.  See
 413 <A HREF="#users">users</A> for information on restricting access based
 414 on a username and password.<P>
 415
 416 The CLI gives you real-time control over almost everything in
 417 the process.  The interface is designed to look like a Cisco
 418 device, and supports things like command history, line editing and
 419 context sensitive help.  This is provided by linking with the
 420 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 421 library.  Some general documentation of the interface is
 422 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 423 here</A>.<P>
 424
 425 After you have connected to the telnet port (and perhaps logged in), you
 426 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 427
 428 Enter <EM>help</EM> to get a list of possible commands.  A brief
 429 overview of the more important commands follows:
 430
 431 <UL>
 432 <LI><B>show session</B><BR>
 433 Without specifying a session ID, this will list all tunnels currently
 434 connected.  If you specify a session ID, you will be given all
 435 information on a single tunnel.  Note that the full session list can
 436 be around 185 columns wide, so you should probably use a wide terminal
 437 to see the list properly.<P>
 438 The columns listed in the overview are:
 439 <TABLE>
 440         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 441         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 442         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 443         authentication.  If this is *, then LCP authentication has not
 444         completed.</TD></TR>
 445         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 446         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 447         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 448         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 449         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 450         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 451         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 452         trapped in the walled garden.  This field is present even if the
 453         garden module is not loaded.</TD></TR>
 454         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 455         session started</TD></TR>
 456         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 457         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 458         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 459         detected on the session</TD></TR>
 460         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 461         connected to.</TD></TR>
 462         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 463         provided during the session setup.  This field is generated by the
 464         LAC.</TD></TR>
 465 </TABLE>
 466 <P>
 467 </LI>
 468
 469 <LI><B>show users</B><BR>
 470 With no arguments, display a list of currently connected users.  If an
 471 argument is given, the session details for the given username are
 472 displayed.
 473 </LI>
 474
 475 <LI><B>show tunnel</B><BR>
 476 This will show all the open tunnels in a summary, or detail on a single
 477 tunnel if you give a tunnel id.<P>
 478 The columns listed in the overview are:
 479 <TABLE>
 480         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 481         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 482         provided by the LAC.  This has no relation to DNS, it is just
 483         a text field.</TD></TR>
 484         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 485         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 486         Opening</TD></TR>
 487         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 488         tunnel</TD></TR>
 489 </TABLE>
 490 <P>
 491 </LI>
 492
 493 <LI><B>show pool</B><BR>
 494 Displays the current IP address pool allocation.  This will only display
 495 addresses that are in use, or are reserved for re-allocation to a
 496 disconnected user.<P>
 497 If an address is not currently in use, but has been used, then in the User
 498 column the username will be shown in square brackets, followed by the time
 499 since the address was used:
 500 <PRE>
 501 IP Address      Used  Session User
 502 192.168.100.6     N           [joe.user] 1548s
 503 </PRE>
 504 <P>
 505 </LI>
 506
 507 <LI><B>show radius</B><BR>
 508 Show a summary of the in-use radius sessions.  This list should not be very
 509 long, as radius sessions should be cleaned up as soon as they are used.  The
 510 columns listed are:
 511 <TABLE>
 512         <TR><TD><B>Radius</B></TD><TD>The ID of the radius request.  This is
 513         sent in the packet to the radius server for identification.</TD></TR>
 514         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 515         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 516         <TR><TD><B>Session</B></TD><TD>The session ID that this radius
 517         request is associated with</TD></TR>
 518         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 519         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 520         <TR><TD><B>Try</B></TD><TD>Retry count.  The radius request is
 521         discarded after 3 retries.</TD></TR>
 522 </TABLE>
 523 <P>
 524 </LI>
 525
 526 <LI><B>show running-config</B><BR>
 527 This will list the current running configuration.  This is in a format that
 528 can either be pasted into the configuration file, or run directly at the
 529 command line.
 530 <P>
 531 </LI>
 532
 533 <LI><B>show counters</B><BR>
 534 Internally, counters are kept of key values, such as bytes and packets
 535 transferred, as well as function call counters.  This function displays all
 536 these counters, and is probably only useful for debugging.<P>
 537 You can reset these counters by running <EM>clear counters</EM>.
 538 <P>
 539 </LI>
 540
 541 <LI><B>show cluster</B><BR>
 542 Show cluster status.  Shows the cluster state for this server
 543 (Master/Slave), information about known peers and (for slaves) the
 544 master IP address, last packet seen and up-to-date status.<P>
 545 See <A HREF="#Clustering">Clustering</A> for more information.
 546 <P>
 547 </LI>
 548
 549 <LI><B>write memory</B><BR>
 550 This will write the current running configuration to the config file
 551 <B>startup-config</B>, which will be run on a restart.
 552 <P>
 553 </LI>
 554
 555 <LI><B>snoop</B><BR>
 556 You must specify a username, IP address and port.  All packets for the
 557 current session for that username will be forwarded to the given
 558 host/port.  Specify <EM>no snoop username</EM> to disable interception
 559 for the session.<P>
 560
 561 If you want interception to be permanent, you will have to modify the radius
 562 response for the user.  See <A HREF="#Interception">Interception</A>.
 563 <P>
 564 </LI>
 565
 566 <LI><B>throttle</B><BR>
 567 You must specify a username, which will be throttled for the current
 568 session.  Specify <EM>no throttle username</EM> to disable throttling
 569 for the current session.<P>
 570
 571 If you want throttling to be permanent, you will have to modify the
 572 radius response for the user.  See <A HREF="#THrottling">Throttling</A>.
 573 <P>
 574 </LI>
 575
 576 <LI><B>drop session</B><BR>
 577 This will cleanly disconnect a session.  You must specify a session id, which
 578 you can get from <EM>show session</EM>.  This will send a disconnect message
 579 to the remote end.
 580 <P>
 581 </LI>
 582
 583 <LI><B>drop tunnel</B><BR>
 584 This will cleanly disconnect a tunnel, as well as all sessions on that
 585 tunnel.  It will send a disconnect message for each session individually, and
 586 after 10 seconds it will send a tunnel disconnect message.
 587 <P>
 588 </LI>
 589
 590 <LI><B>uptime</B><BR>
 591 This will show how long the l2tpns process has been running, and the current
 592 bandwidth utilization:
 593 <PRE>
 594 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 595 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 596 </PRE>
 597 The bandwidth line contains 4 sets of values.<BR>
 598 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 599 (user uploads), in mbits/sec.<BR>
 600 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 601 downloads).<BR>
 602 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 603 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 604 <P>
 605 These counters are updated every second.
 606 <P>
 607 </LI>
 608
 609 <LI><B>configure terminal</B><BR>
 610 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 611 The following commands are valid in this mode:<P>
 612 </LI>
 613
 614 <LI><B>load plugin</B><BR>
 615 Load a plugin.  You must specify the plugin name, and it will search in
 616 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 617 <EM>remove plugin</EM>.
 618 <P>
 619 </LI>
 620
 621 <LI><B>set</B><BR>
 622 Set a configuration variable.  You must specify the variable name, and
 623 the value.  If the value contains any spaces, you should quote the
 624 value with double (") or single (') quotes.<P>
 625
 626 You can set any <A HREF="#startup-config">startup-config</A> value in
 627 this way, although some may require a restart to take effect.<P>
 628 </LI>
 629 </UL>
 630
 631 <H3 ID="nsctl">nsctl</H3>
 632
 633 nsctl was implemented (badly) to allow messages to be passed to modules.<P>
 634
 635 You must pass at least 2 parameters: <EM>host</EM> and <EM>command</EM>.  The
 636 host is the address of the l2tpns server which you want to send the message
 637 to.<P>
 638
 639 Command can currently be either <EM>garden</EM> or <EM>ungarden</EM>.  With
 640 both of these commands, you must give a session ID as the 3rd parameter.
 641 This will activate or deactivate the walled garden for a session
 642 temporarily.
 643
 644 <H3 ID="Signals">Signals</H3>
 645
 646 While the process is running, you can send it a few different signals, using
 647 the kill command.
 648 <PRE>
 649 killall -HUP l2tpns
 650 </PRE>
 651
 652 The signals understood are:
 653 <UL>
 654 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
 655 <LI>SIGTERM / SIGINT - Shut down for a restart.  This will dump the current
 656 state to disk (if <EM>save_state</EM> is set to true).  Upon restart, the
 657 process will read this saved state to resume active sessions.<P>
 658 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 659 every active session and tunnel before shutting down.  This is a good idea
 660 when upgrading the code, as no sessions will be left with the remote end
 661 thinking they are open.</LI>
 662 </UL>
 663
 664 <H2 ID="Throttling">Throttling</H2>
 665
 666 l2tpns contains support for slowing down user sessions to whatever speed you
 667 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 668 before this will be activated.<P>
 669
 670 If you wish a session to be throttled permanently, you should set the
 671 Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
 672 will be handled by the <EM>autothrottle</EM> module.<P>
 673
 674 Otherwise, you can enable and disable throttling an active session using
 675 the <EM>throttle</EM> CLI command.<P>
 676
 677 <H2 ID="Interception">Interception</H2>
 678
 679 You may have to deal with legal requirements to be able to intercept a
 680 user's traffic at any time.  l2tpns allows you to begin and end interception
 681 on the fly, as well as at authentication time.<P>
 682
 683 When a user is being intercepted, a copy of every packet they send and
 684 receive will be sent wrapped in a UDP packet to the IP address and port set
 685 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 686 variables.<P>
 687
 688 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 689
 690 To enable interception on a connected user, use the <EM>snoop username</EM>
 691 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 692 immediately.<P>
 693
 694 If you wish the user to be intercepted whenever they reconnect, you will
 695 need to modify the radius response to include the Vendor-Specific value
 696 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 697 you need to have the <EM>autosnoop</EM> module loaded.<P>
 698
 699 <H2 ID="Authentication">Authentication</H2>
 700
 701 Whenever a session connects, it is not fully set up until authentication is
 702 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 703 request to l2tpns.<P>
 704
 705 This request is sent to the radius server, which will hopefully respond with
 706 Auth-Accept or Auth-Reject.<P>
 707
 708 If Auth-Accept is received, the session is set up and an IP address is
 709 assigned.  The radius server can include a Framed-IP-Address field in the
 710 reply, and that address will be assigned to the client.  It can also include
 711 specific DNS servers, and a Framed-Route if that is required.<P>
 712
 713 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 714 at which point they should disconnect.  The exception to this is when the
 715 walled garden module is loaded, in which case the user still receives the
 716 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 717 should not receive any service.<P>
 718
 719 The radius reply can also contain a Vendor-Specific attribute called
 720 Cisco-Avpair.  This field is a freeform text field that most Cisco
 721 devices understand to contain configuration instructions for the session.  In
 722 the case of l2tpns it is expected to be of the form
 723 <PRE>
 724 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 725 </PRE>
 726
 727 Each key-value pair is separated and passed to any modules loaded.  The
 728 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 729 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 730 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 731 contain:
 732 <PRE>
 733 intercept=yes,throttle=yes
 734 </PRE>
 735
 736 <H2 ID="Plugins">Plugins</H2>
 737
 738 So as to make l2tpns as flexible as possible (I know the core code is pretty
 739 difficult to understand), it includes a plugin API, which you can use to
 740 hook into certain events.<P>
 741
 742 There are a few example modules included - autosnoop, autothrottle and
 743 garden.<P>
 744
 745 When an event happens that has a hook, l2tpns looks for a predefined
 746 function name in every loaded module, and runs them in the order the modules
 747 were loaded.<P>
 748
 749 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 750 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 751 modules should be run for this event.<P>
 752 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 753 no further processing should be done for this event.  <EM>Use this with care.</EM>
 754
 755 Every event function called takes a specific structure named
 756 param_<EM>event</EM>, which varies in content with each event.  The
 757 function name for each event will be <B>plugin_<EM>event</EM></B>,
 758 so for the event <EM>timer</EM>, the function declaration should look like:
 759 <PRE>
 760 int plugin_timer(struct param_timer *data);
 761 </PRE>
 762
 763 A list of the available events follows, with a list of all the fields in the
 764 supplied structure:
 765 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 766 <TABLE CELLSPACING=1 CELLPADDING=3>
 767         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 768         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 769                 <TD>This is called after a radius response has been
 770                 received, but before it has been processed by the
 771                 code.  This will allow you to modify the response in
 772                 some way.
 773                 </TD>
 774                 <TD>
 775                 <UL>
 776                         <LI>t - Tunnel ID</LI>
 777                         <LI>s - Session ID</LI>
 778                         <LI>username</LI>
 779                         <LI>password</LI>
 780                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 781                         <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
 782                 </UL>
 783                 </TD>
 784         </TR>
 785         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 786                 <TD>This is called after a radius response has been
 787                 received, and the basic checks have been performed.  This
 788                 is what the garden module uses to force authentication
 789                 to be accepted.
 790                 </TD>
 791                 <TD>
 792                 <UL>
 793                         <LI>t - Tunnel ID</LI>
 794                         <LI>s - Session ID</LI>
 795                         <LI>username</LI>
 796                         <LI>auth_allowed - This is already set to true or
 797                         false depending on whether authentication has been
 798                         allowed so far.  You can set this to 1 or 0 to force
 799                         allow or disallow authentication</LI>
 800                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 801                 </UL>
 802                 </TD>
 803         </TR>
 804         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 805                 <TD>This is called whenever a session receives a
 806                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 807                 seriously slow down the system.</FONT>
 808                 </TD>
 809                 <TD>
 810                 <UL>
 811                         <LI>t - Tunnel ID</LI>
 812                         <LI>s - Session ID</LI>
 813                         <LI>buf - The raw packet data</LI>
 814                         <LI>len - The length of buf</LI>
 815                 </UL>
 816                 </TD>
 817         </TR>
 818         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 819                 <TD>This is called whenever a session sends a
 820                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 821                 seriously slow down the system.</FONT>
 822                 </TD>
 823                 <TD>
 824                 <UL>
 825                         <LI>t - Tunnel ID</LI>
 826                         <LI>s - Session ID</LI>
 827                         <LI>buf - The raw packet data</LI>
 828                         <LI>len - The length of buf</LI>
 829                 </UL>
 830                 </TD>
 831         </TR>
 832         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 833                 <TD>This is run every second, no matter what is happening.
 834                 This is called from a signal handler, so make sure anything
 835                 you do is reentrant.
 836                 </TD>
 837                 <TD>
 838                 <UL>
 839                         <LI>time_now - The current unix timestamp</LI>
 840                 </UL>
 841                 </TD>
 842         </TR>
 843         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 844                 <TD>This is called after a session is fully set up.  The
 845                 session is now ready to handle traffic.
 846                 </TD>
 847                 <TD>
 848                 <UL>
 849                         <LI>t - Tunnel ID</LI>
 850                         <LI>s - Session ID</LI>
 851                 </UL>
 852                 </TD>
 853         </TR>
 854         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 855                 <TD>This is called when a session is about to be shut down.
 856                 This may be called multiple times for the same session.
 857                 </TD>
 858                 <TD>
 859                 <UL>
 860                         <LI>t - Tunnel ID</LI>
 861                         <LI>s - Session ID</LI>
 862                 </UL>
 863                 </TD>
 864         </TR>
 865         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 866                 <TD>This is called whenever a radius response includes a
 867                 Cisco-Avpair value.  The value is split up into
 868                 <EM>key=value</EM> pairs, and each is processed through all
 869                 modules.
 870                 </TD>
 871                 <TD>
 872                 <UL>
 873                         <LI>t - Tunnel ID</LI>
 874                         <LI>s - Session ID</LI>
 875                         <LI>key</LI>
 876                         <LI>value</LI>
 877                 </UL>
 878                 </TD>
 879         </TR>
 880         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 881                 <TD>This is called in whenever a nsctl packet is received.
 882                 This should handle the packet and form a response if
 883                 required.
 884                 </TD>
 885                 <TD>
 886                 <UL>
 887                         <LI>buf - The raw packet data</LI>
 888                         <LI>l - The raw packet data length</LI>
 889                         <LI>source_ip - Where the request came from</LI>
 890                         <LI>source_port - Where the request came from</LI>
 891                         <LI>response - Allocate a buffer and put your response in here</LI>
 892                         <LI>response_length - Length of response</LI>
 893                         <LI>send_response - true or false whether a response
 894                         should be sent.  If you set this to true, you must
 895                         allocate a response buffer.</LI>
 896                         <LI>type - Type of request (see nsctl.c)</LI>
 897                         <LI>id - ID of request</LI>
 898                         <LI>data - I'm really not sure</LI>
 899                         <LI>data_length - Length of data</LI>
 900                 </UL>
 901                 </TD>
 902         </TR>
 903 </TABLE>
 904 </TD></TR></TABLE>
 905
 906 <H2 ID="WalledGarden">Walled Garden</H2>
 907
 908 Walled Garden is implemented so that you can provide perhaps limited service
 909 to sessions that incorrectly authenticate.<P>
 910
 911 Whenever a session provides incorrect authentication, and the
 912 radius server responds with Auth-Reject, the walled garden module
 913 (if loaded) will force authentication to succeed, but set the flag
 914 <EM>garden</EM> in the session structure, and adds an iptables rule to
 915 the <B>garden_users</B> chain to force all packets for the session's IP
 916 address to traverse the <B>garden</B> chain.<P>
 917
 918 This doesn't <EM>just work</EM>.  To set this all up, you will to
 919 setup the <B>garden</B> nat table with the
 920 <A HREF="#build-garden">build-garden</A> script with rules to limit
 921 user's traffic.  For example, to force all traffic except DNS to be
 922 forwarded to 192.168.1.1, add these entries to your
 923 <EM>build-garden</EM>:
 924 <PRE>
 925 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
 926 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
 927 </PRE>
 928
 929 l2tpns will add entries to the garden_users chain as appropriate.<P>
 930
 931 You can check the amount of traffic being captured using the following
 932 command:
 933 <PRE>
 934 iptables -t nat -L garden -nvx
 935 </PRE>
 936
 937 <H2 ID="Clustering">Clustering</H2>
 938
 939 An l2tpns cluster consists of of one* or more servers configured with
 940 the same configuration, notably the multicast <B>cluster_address</B>.<P>
 941
 942 *A stand-alone server is simply a degraded cluster.<P>
 943
 944 Initially servers come up as cluster slaves, and periodically (every
 945 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
 946 containing the start time of the process to the multicast
 947 <B>cluster_address</B>.<P>
 948
 949 A cluster master sends heartbeat rather than ping packets, which
 950 contain those session and tunnel changes since the last heartbeat.<P>
 951
 952 When a slave has not seen a heartbeat within
 953 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
 954 examining the list of peers it has seen pings from and determines
 955 which of these and itself is the "best" candidate to be master.
 956 "Best" in this context means the server with the highest uptime (the
 957 highest IP address is used as a tie-breaker in the case of equal
 958 uptimes).<P>
 959
 960 After discovering a master, and determining that it is up-to-date (has
 961 seen an update for all in-use sessions and tunnels from heartbeat
 962 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
 963 the <B>bind_address</B> and for all addresses/networks in
 964 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
 965 the session state, as well as packets for throttled or gardened
 966 sessions are forwarded to the master for handling.  In addition, byte
 967 counters for session traffic are periodically forwarded.<P>
 968
 969 A master, when determining that it has at least one up-to-date slave
 970 will drop all routes (raising them again if all slaves disappear) and
 971 subsequently handle only packets forwarded to it by the slaves.<P>
 972
 973 <H2 ID="Routing">Routing</H2>
 974 If you are running a single instance, you may simply statically route
 975 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
 976 arp).<P>
 977
 978 For a cluster, configure the members as BGP neighbours on your router
 979 and configure multi-path load-balancing.  Cisco uses "maximum-paths
 980 ibgp" for IBGP.  If this is not supported by your IOS revision, you
 981 can use "maximum-paths" (which works for EBGP) and set
 982 <B>as_number</B> to a private value such as 64512.<P>
 983
 984 <H2 ID="Performance">Performance</H2>
 985
 986 Performance is great.<P>
 987
 988 I'd like to include some pretty graphs here that show a linear performance
 989 increase, with no impact by number of connected sessions.<P>
 990
 991 That's really what it looks like.<P>
 992
 993 <BR>
 994 David Parrish<BR>
 995 <A HREF="mailto:david@dparrish.com?subject=L2TPNS%20Documentation">david@dparrish.com</A>
 996 </BODY>
 997 </HTML>