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