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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:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</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>pid_file</B> (string)<BR>
 177 If this is set, the process id will be written to this file. The filename must
 178 contain an absolute path.
 179 <P>
 180 </LI>
 181
 182 <LI><B>l2tp_secret</B> (string)<BR>
 183 This sets the string that l2tpns will use for authenticating tunnel request.
 184 This must be the same as the LAC, or authentication will fail.  This will
 185 only actually be used if the LAC requests authentication.
 186 <P>
 187 </LI>
 188
 189 <LI><B>primary_dns</B> (ip address)
 190 <LI><B>secondary_dns</B> (ip address)<BR>
 191 Whenever a PPP connection is established, DNS servers will be sent to the
 192 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 193 one will not be sent.
 194 <P>
 195 </LI>
 196
 197 <LI><B>save_state</B> (boolean)<BR>
 198 When l2tpns receives a STGTERM it will write out its current
 199 ip_address_pool, session and tunnel tables to disk prior to exiting to
 200 be re-loaded at startup.  The validity of this data is obviously quite
 201 short and the intent is to allow an sessions to be retained over a
 202 software upgrade.
 203 <P>
 204 </LI>
 205
 206 <LI><B>primary_radius</B> (ip address)
 207 <LI><B>secondary_radius</B> (ip address)<BR>
 208 This sets the radius servers used for both authentication and
 209 accounting.  If the primary server does not respond, then the
 210 secondary radius server will be tried.
 211 <P>
 212 </LI>
 213
 214 <LI><B>primary_radius_port</B> (short)
 215 <LI><B>secondary_radius_port</B> (short)<BR>
 216 This sets the authentication ports for the primary and secondary
 217 radius servers.  The accounting port is one more than the authentication
 218 port.  If no radius ports are given, the authentication port defaults to 1645,
 219 and the accounting port to 1646.
 220 <P>
 221 </LI>
 222
 223 <LI><B>radius_accounting</B> (boolean)<BR>
 224 If set to true, then radius accounting packets will be sent.  This
 225 means that a Start record will be sent when the session is
 226 successfully authenticated, and a Stop record will be sent when the
 227 session is closed.
 228 <P>
 229 </LI>
 230
 231 <LI><B>radius_secret</B> (string)<BR>
 232 This secret will be used in all radius queries.  If this is not set then
 233 radius queries will fail.
 234 <P>
 235 </LI>
 236
 237 <LI><B>bind_address</B> (ip address)<BR>
 238 When the tun interface is created, it is assigned the address
 239 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 240 containing user traffic should be routed via this address if given,
 241 otherwise the primary address of the machine.
 242 <P>
 243 </LI>
 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 <P>
 251 </LI>
 252
 253 <LI><B>throttle_speed</B> (int)<BR>
 254 Sets the speed (in kbits/s) which sessions will be limited to.  If this is
 255 set to 0, then throttling will not be used at all.  Note: You can set this by
 256 the CLI, but changes will not affect currently connected users.
 257 <P>
 258 </LI>
 259
 260 <LI><B>throttle_buckets</B> (int)<BR>
 261 Number of token buckets to allocate for throttling.  Each throttled
 262 session requires two buckets (in and out).
 263 <P>
 264 </LI>
 265
 266 <LI><B>accounting_dir</B> (string)<BR>
 267 If set to a directory, then every 5 minutes the current usage for
 268 every connected use will be dumped to a file in this directory.  Each
 269 file dumped begins with a header, where each line is prefixed by #.
 270 Following the header is a single line for every connected user, fields
 271 separated by a space.<BR> The fields are username, ip, qos,
 272 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 273 2 if the user is throttled.
 274 <P>
 275 </LI>
 276
 277 <LI><B>setuid</B> (int)<BR>
 278 After starting up and binding the interface, change UID to this.  This
 279 doesn't work properly.
 280 <P>
 281 </LI>
 282
 283 <LI><B>dump_speed</B> (boolean)<BR>
 284 If set to true, then the current bandwidth utilization will be logged every
 285 second.  Even if this is disabled, you can see this information by running
 286 the <EM>uptime</EM> command on the CLI.
 287 <P>
 288 </LI>
 289
 290 <LI><B>cleanup_interval</B> (int)<BR>
 291 Interval between regular cleanups (in seconds).
 292 <P>
 293 </LI>
 294
 295 <LI><B>multi_read_count</B> (int)<BR>
 296 Number of packets to read off each of the UDP and TUN fds when
 297 returned as readable by select (default:  10).  Avoids incurring the
 298 unnecessary system call overhead of select on busy servers.
 299 <P>
 300 </LI>
 301
 302 <LI><B>scheduler_fifo</B> (boolean)<BR>
 303 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 304 causes the kernel to immediately preempt any currently SCHED_OTHER
 305 (normal) process in favour of l2tpns when it becomes runnable.
 306 Ignored on uniprocessor systems.
 307 <P>
 308 </LI>
 309
 310 <LI><B>lock_pages</B> (boolean)<BR>
 311 Keep all pages mapped by the l2tpns process in memory.
 312 <P>
 313 </LI>
 314
 315 <LI><B>icmp_rate</B> (int)<BR>
 316 Maximum number of host unreachable icmp packets to send per second.
 317 <P>
 318 </LI>
 319
 320 <LI><B>cluster_address</B> (ip address)<BR>
 321 Multicast cluster address (default:  239.192.13.13).  See the section
 322 on <A HREF="#Clustering">Clustering</A> for more information.
 323 <P>
 324 </LI>
 325
 326 <LI><B>cluster_interface</B> (string)<BR>
 327 Interface for cluster packets (default: eth0).
 328 <P>
 329 </LI>
 330
 331 <LI><B>cluster_hb_interval</B> (int)<BR>
 332 Interval in tenths of a second between cluster heartbeat/pings.
 333 <P>
 334 </LI>
 335
 336 <LI><B>cluster_hb_timeout</B> (int)<BR>
 337 Cluster heartbeat timeout in tenths of a second.  A new master will be
 338 elected when this interval has been passed without seeing a heartbeat
 339 from the master.
 340 <P>
 341 </LI>
 342
 343 <LI><B>as_number</B> (int)<BR>
 344 Defines the local AS number for BGP (see <A HREF="#Routing">Routing</A>).
 345 <P>
 346 </LI>
 347
 348 <LI><B>bgp_peer1</B> (string)
 349 <LI><B>bgp_peer1_as</B> (int)
 350 <LI><B>bgp_peer2</B> (string)
 351 <LI><B>bgp_peer2_as</B> (int)<BR>
 352 <P>
 353 DNS name (or IP) and AS number of BGP peers.
 354 </LI>
 355 </UL>
 356
 357 <H3 ID="users">users</H3>
 358
 359 Usernames and passwords for the command-line interface are stored in
 360 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 361 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 362 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 363 plain text by the prefix <B>{crypt}</B>.<P>
 364
 365 The username <B>enable</B> has a special meaning and is used to set
 366 the enable password.<P>
 367
 368 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 369 port 23 will be allowed access without a username / password.<P>
 370
 371 <H3 ID="ip-pool">ip_pool</H3>
 372
 373 This file is used to configure the IP address pool which user
 374 addresses are assigned from.  This file should contain either an IP
 375 address or a CIDR network per line.  e.g.:<P>
 376
 377 <PRE>
 378     192.168.1.1
 379     192.168.1.2
 380     192.168.1.3
 381     192.168.4.0/24
 382     172.16.0.0/16
 383     10.0.0.0/8
 384 </PRE>
 385
 386 Keep in mind that l2tpns can only handle 65535 connections per
 387 process, so don't put more than 65535 IP addresses in the
 388 configuration file.  They will be wasted.
 389
 390 <H3 ID="build-garden">build-garden</H3>
 391
 392 The garden plugin on startup creates a NAT table called "garden" then
 393 sources the <B>build-garden</B> script to populate that table.  All
 394 packets from gardened users will be sent through this table.  Example:
 395
 396 <PRE>
 397     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 398     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 399     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 400     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 401     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 402     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 403     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 404     iptables -t nat -A garden -p icmp -j ACCEPT
 405     iptables -t nat -A garden -j DROP
 406 </PRE>
 407
 408 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 409
 410 A running l2tpns process can be controlled in a number of ways.  The primary
 411 method of control is by the Command-Line Interface (CLI).<P>
 412
 413 You can also remotely send commands to modules via the nsctl client
 414 provided.  This currently only works with the walled garden module, but
 415 modification is trivial to support other modules.<P>
 416
 417 Also, there are a number of signals that l2tpns understands and takes action
 418 when it receives them.
 419
 420 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 421
 422 You can access the command line interface by telnet'ing to port 23.
 423 There is no IP address restriction, so it's a good idea to firewall
 424 this port off from anyone who doesn't need access to it.  See
 425 <A HREF="#users">users</A> for information on restricting access based
 426 on a username and password.<P>
 427
 428 The CLI gives you real-time control over almost everything in
 429 the process.  The interface is designed to look like a Cisco
 430 device, and supports things like command history, line editing and
 431 context sensitive help.  This is provided by linking with the
 432 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 433 library.  Some general documentation of the interface is
 434 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 435 here</A>.<P>
 436
 437 After you have connected to the telnet port (and perhaps logged in), you
 438 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 439
 440 Enter <EM>help</EM> to get a list of possible commands.  A brief
 441 overview of the more important commands follows:
 442
 443 <UL>
 444 <LI><B>show session</B><BR>
 445 Without specifying a session ID, this will list all tunnels currently
 446 connected.  If you specify a session ID, you will be given all
 447 information on a single tunnel.  Note that the full session list can
 448 be around 185 columns wide, so you should probably use a wide terminal
 449 to see the list properly.<P>
 450 The columns listed in the overview are:
 451 <TABLE>
 452         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 453         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 454         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 455         authentication.  If this is *, then LCP authentication has not
 456         completed.</TD></TR>
 457         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 458         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 459         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 460         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 461         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 462         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 463         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 464         trapped in the walled garden.  This field is present even if the
 465         garden module is not loaded.</TD></TR>
 466         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 467         session started</TD></TR>
 468         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 469         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 470         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 471         detected on the session</TD></TR>
 472         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 473         connected to.</TD></TR>
 474         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 475         provided during the session setup.  This field is generated by the
 476         LAC.</TD></TR>
 477 </TABLE>
 478 <P>
 479 </LI>
 480
 481 <LI><B>show users</B><BR>
 482 With no arguments, display a list of currently connected users.  If an
 483 argument is given, the session details for the given username are
 484 displayed.
 485 </LI>
 486
 487 <LI><B>show tunnel</B><BR>
 488 This will show all the open tunnels in a summary, or detail on a single
 489 tunnel if you give a tunnel id.<P>
 490 The columns listed in the overview are:
 491 <TABLE>
 492         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 493         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 494         provided by the LAC.  This has no relation to DNS, it is just
 495         a text field.</TD></TR>
 496         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 497         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 498         Opening</TD></TR>
 499         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 500         tunnel</TD></TR>
 501 </TABLE>
 502 <P>
 503 </LI>
 504
 505 <LI><B>show pool</B><BR>
 506 Displays the current IP address pool allocation.  This will only display
 507 addresses that are in use, or are reserved for re-allocation to a
 508 disconnected user.<P>
 509 If an address is not currently in use, but has been used, then in the User
 510 column the username will be shown in square brackets, followed by the time
 511 since the address was used:
 512 <PRE>
 513 IP Address      Used  Session User
 514 192.168.100.6     N           [joe.user] 1548s
 515 </PRE>
 516 <P>
 517 </LI>
 518
 519 <LI><B>show radius</B><BR>
 520 Show a summary of the in-use radius sessions.  This list should not be very
 521 long, as radius sessions should be cleaned up as soon as they are used.  The
 522 columns listed are:
 523 <TABLE>
 524         <TR><TD><B>Radius</B></TD><TD>The ID of the radius request.  This is
 525         sent in the packet to the radius server for identification.</TD></TR>
 526         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 527         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 528         <TR><TD><B>Session</B></TD><TD>The session ID that this radius
 529         request is associated with</TD></TR>
 530         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 531         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 532         <TR><TD><B>Try</B></TD><TD>Retry count.  The radius request is
 533         discarded after 3 retries.</TD></TR>
 534 </TABLE>
 535 <P>
 536 </LI>
 537
 538 <LI><B>show running-config</B><BR>
 539 This will list the current running configuration.  This is in a format that
 540 can either be pasted into the configuration file, or run directly at the
 541 command line.
 542 <P>
 543 </LI>
 544
 545 <LI><B>show counters</B><BR>
 546 Internally, counters are kept of key values, such as bytes and packets
 547 transferred, as well as function call counters.  This function displays all
 548 these counters, and is probably only useful for debugging.<P>
 549 You can reset these counters by running <EM>clear counters</EM>.
 550 <P>
 551 </LI>
 552
 553 <LI><B>show cluster</B><BR>
 554 Show cluster status.  Shows the cluster state for this server
 555 (Master/Slave), information about known peers and (for slaves) the
 556 master IP address, last packet seen and up-to-date status.<P>
 557 See <A HREF="#Clustering">Clustering</A> for more information.
 558 <P>
 559 </LI>
 560
 561 <LI><B>write memory</B><BR>
 562 This will write the current running configuration to the config file
 563 <B>startup-config</B>, which will be run on a restart.
 564 <P>
 565 </LI>
 566
 567 <LI><B>snoop</B><BR>
 568 You must specify a username, IP address and port.  All packets for the
 569 current session for that username will be forwarded to the given
 570 host/port.  Specify <EM>no snoop username</EM> to disable interception
 571 for the session.<P>
 572
 573 If you want interception to be permanent, you will have to modify the radius
 574 response for the user.  See <A HREF="#Interception">Interception</A>.
 575 <P>
 576 </LI>
 577
 578 <LI><B>throttle</B><BR>
 579 You must specify a username, which will be throttled for the current
 580 session.  Specify <EM>no throttle username</EM> to disable throttling
 581 for the current session.<P>
 582
 583 If you want throttling to be permanent, you will have to modify the
 584 radius response for the user.  See <A HREF="#THrottling">Throttling</A>.
 585 <P>
 586 </LI>
 587
 588 <LI><B>drop session</B><BR>
 589 This will cleanly disconnect a session.  You must specify a session id, which
 590 you can get from <EM>show session</EM>.  This will send a disconnect message
 591 to the remote end.
 592 <P>
 593 </LI>
 594
 595 <LI><B>drop tunnel</B><BR>
 596 This will cleanly disconnect a tunnel, as well as all sessions on that
 597 tunnel.  It will send a disconnect message for each session individually, and
 598 after 10 seconds it will send a tunnel disconnect message.
 599 <P>
 600 </LI>
 601
 602 <LI><B>uptime</B><BR>
 603 This will show how long the l2tpns process has been running, and the current
 604 bandwidth utilization:
 605 <PRE>
 606 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 607 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 608 </PRE>
 609 The bandwidth line contains 4 sets of values.<BR>
 610 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 611 (user uploads), in mbits/sec.<BR>
 612 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 613 downloads).<BR>
 614 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 615 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 616 <P>
 617 These counters are updated every second.
 618 <P>
 619 </LI>
 620
 621 <LI><B>configure terminal</B><BR>
 622 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 623 The following commands are valid in this mode:<P>
 624 </LI>
 625
 626 <LI><B>load plugin</B><BR>
 627 Load a plugin.  You must specify the plugin name, and it will search in
 628 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 629 <EM>remove plugin</EM>.
 630 <P>
 631 </LI>
 632
 633 <LI><B>set</B><BR>
 634 Set a configuration variable.  You must specify the variable name, and
 635 the value.  If the value contains any spaces, you should quote the
 636 value with double (") or single (') quotes.<P>
 637
 638 You can set any <A HREF="#startup-config">startup-config</A> value in
 639 this way, although some may require a restart to take effect.<P>
 640 </LI>
 641 </UL>
 642
 643 <H3 ID="nsctl">nsctl</H3>
 644
 645 nsctl was implemented (badly) to allow messages to be passed to modules.<P>
 646
 647 You must pass at least 2 parameters: <EM>host</EM> and <EM>command</EM>.  The
 648 host is the address of the l2tpns server which you want to send the message
 649 to.<P>
 650
 651 Command can currently be either <EM>garden</EM> or <EM>ungarden</EM>.  With
 652 both of these commands, you must give a session ID as the 3rd parameter.
 653 This will activate or deactivate the walled garden for a session
 654 temporarily.
 655
 656 <H3 ID="Signals">Signals</H3>
 657
 658 While the process is running, you can send it a few different signals, using
 659 the kill command.
 660 <PRE>
 661 killall -HUP l2tpns
 662 </PRE>
 663
 664 The signals understood are:
 665 <UL>
 666 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
 667 <LI>SIGTERM / SIGINT - Shut down for a restart.  This will dump the current
 668 state to disk (if <EM>save_state</EM> is set to true).  Upon restart, the
 669 process will read this saved state to resume active sessions.<P>
 670 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 671 every active session and tunnel before shutting down.  This is a good idea
 672 when upgrading the code, as no sessions will be left with the remote end
 673 thinking they are open.</LI>
 674 </UL>
 675
 676 <H2 ID="Throttling">Throttling</H2>
 677
 678 l2tpns contains support for slowing down user sessions to whatever speed you
 679 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 680 before this will be activated.<P>
 681
 682 If you wish a session to be throttled permanently, you should set the
 683 Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
 684 will be handled by the <EM>autothrottle</EM> module.<P>
 685
 686 Otherwise, you can enable and disable throttling an active session using
 687 the <EM>throttle</EM> CLI command.<P>
 688
 689 <H2 ID="Interception">Interception</H2>
 690
 691 You may have to deal with legal requirements to be able to intercept a
 692 user's traffic at any time.  l2tpns allows you to begin and end interception
 693 on the fly, as well as at authentication time.<P>
 694
 695 When a user is being intercepted, a copy of every packet they send and
 696 receive will be sent wrapped in a UDP packet to the IP address and port set
 697 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 698 variables.<P>
 699
 700 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 701
 702 To enable interception on a connected user, use the <EM>snoop username</EM>
 703 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 704 immediately.<P>
 705
 706 If you wish the user to be intercepted whenever they reconnect, you will
 707 need to modify the radius response to include the Vendor-Specific value
 708 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 709 you need to have the <EM>autosnoop</EM> module loaded.<P>
 710
 711 <H2 ID="Authentication">Authentication</H2>
 712
 713 Whenever a session connects, it is not fully set up until authentication is
 714 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 715 request to l2tpns.<P>
 716
 717 This request is sent to the radius server, which will hopefully respond with
 718 Auth-Accept or Auth-Reject.<P>
 719
 720 If Auth-Accept is received, the session is set up and an IP address is
 721 assigned.  The radius server can include a Framed-IP-Address field in the
 722 reply, and that address will be assigned to the client.  It can also include
 723 specific DNS servers, and a Framed-Route if that is required.<P>
 724
 725 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 726 at which point they should disconnect.  The exception to this is when the
 727 walled garden module is loaded, in which case the user still receives the
 728 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 729 should not receive any service.<P>
 730
 731 The radius reply can also contain a Vendor-Specific attribute called
 732 Cisco-Avpair.  This field is a freeform text field that most Cisco
 733 devices understand to contain configuration instructions for the session.  In
 734 the case of l2tpns it is expected to be of the form
 735 <PRE>
 736 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 737 </PRE>
 738
 739 Each key-value pair is separated and passed to any modules loaded.  The
 740 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 741 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 742 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 743 contain:
 744 <PRE>
 745 intercept=yes,throttle=yes
 746 </PRE>
 747
 748 <H2 ID="Plugins">Plugins</H2>
 749
 750 So as to make l2tpns as flexible as possible (I know the core code is pretty
 751 difficult to understand), it includes a plugin API, which you can use to
 752 hook into certain events.<P>
 753
 754 There are a few example modules included - autosnoop, autothrottle and
 755 garden.<P>
 756
 757 When an event happens that has a hook, l2tpns looks for a predefined
 758 function name in every loaded module, and runs them in the order the modules
 759 were loaded.<P>
 760
 761 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 762 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 763 modules should be run for this event.<P>
 764 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 765 no further processing should be done for this event.  <EM>Use this with care.</EM>
 766
 767 Every event function called takes a specific structure named
 768 param_<EM>event</EM>, which varies in content with each event.  The
 769 function name for each event will be <B>plugin_<EM>event</EM></B>,
 770 so for the event <EM>timer</EM>, the function declaration should look like:
 771 <PRE>
 772 int plugin_timer(struct param_timer *data);
 773 </PRE>
 774
 775 A list of the available events follows, with a list of all the fields in the
 776 supplied structure:
 777 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 778 <TABLE CELLSPACING=1 CELLPADDING=3>
 779         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 780         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 781                 <TD>This is called after a radius response has been
 782                 received, but before it has been processed by the
 783                 code.  This will allow you to modify the response in
 784                 some way.
 785                 </TD>
 786                 <TD>
 787                 <UL>
 788                         <LI>t - Tunnel ID</LI>
 789                         <LI>s - Session ID</LI>
 790                         <LI>username</LI>
 791                         <LI>password</LI>
 792                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 793                         <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
 794                 </UL>
 795                 </TD>
 796         </TR>
 797         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 798                 <TD>This is called after a radius response has been
 799                 received, and the basic checks have been performed.  This
 800                 is what the garden module uses to force authentication
 801                 to be accepted.
 802                 </TD>
 803                 <TD>
 804                 <UL>
 805                         <LI>t - Tunnel ID</LI>
 806                         <LI>s - Session ID</LI>
 807                         <LI>username</LI>
 808                         <LI>auth_allowed - This is already set to true or
 809                         false depending on whether authentication has been
 810                         allowed so far.  You can set this to 1 or 0 to force
 811                         allow or disallow authentication</LI>
 812                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 813                 </UL>
 814                 </TD>
 815         </TR>
 816         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 817                 <TD>This is called whenever a session receives a
 818                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 819                 seriously slow down the system.</FONT>
 820                 </TD>
 821                 <TD>
 822                 <UL>
 823                         <LI>t - Tunnel ID</LI>
 824                         <LI>s - Session ID</LI>
 825                         <LI>buf - The raw packet data</LI>
 826                         <LI>len - The length of buf</LI>
 827                 </UL>
 828                 </TD>
 829         </TR>
 830         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 831                 <TD>This is called whenever a session sends a
 832                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 833                 seriously slow down the system.</FONT>
 834                 </TD>
 835                 <TD>
 836                 <UL>
 837                         <LI>t - Tunnel ID</LI>
 838                         <LI>s - Session ID</LI>
 839                         <LI>buf - The raw packet data</LI>
 840                         <LI>len - The length of buf</LI>
 841                 </UL>
 842                 </TD>
 843         </TR>
 844         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 845                 <TD>This is run every second, no matter what is happening.
 846                 This is called from a signal handler, so make sure anything
 847                 you do is reentrant.
 848                 </TD>
 849                 <TD>
 850                 <UL>
 851                         <LI>time_now - The current unix timestamp</LI>
 852                 </UL>
 853                 </TD>
 854         </TR>
 855         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 856                 <TD>This is called after a session is fully set up.  The
 857                 session is now ready to handle traffic.
 858                 </TD>
 859                 <TD>
 860                 <UL>
 861                         <LI>t - Tunnel ID</LI>
 862                         <LI>s - Session ID</LI>
 863                 </UL>
 864                 </TD>
 865         </TR>
 866         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 867                 <TD>This is called when a session is about to be shut down.
 868                 This may be called multiple times for the same session.
 869                 </TD>
 870                 <TD>
 871                 <UL>
 872                         <LI>t - Tunnel ID</LI>
 873                         <LI>s - Session ID</LI>
 874                 </UL>
 875                 </TD>
 876         </TR>
 877         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 878                 <TD>This is called whenever a radius response includes a
 879                 Cisco-Avpair value.  The value is split up into
 880                 <EM>key=value</EM> pairs, and each is processed through all
 881                 modules.
 882                 </TD>
 883                 <TD>
 884                 <UL>
 885                         <LI>t - Tunnel ID</LI>
 886                         <LI>s - Session ID</LI>
 887                         <LI>key</LI>
 888                         <LI>value</LI>
 889                 </UL>
 890                 </TD>
 891         </TR>
 892         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 893                 <TD>This is called in whenever a nsctl packet is received.
 894                 This should handle the packet and form a response if
 895                 required.
 896                 </TD>
 897                 <TD>
 898                 <UL>
 899                         <LI>buf - The raw packet data</LI>
 900                         <LI>l - The raw packet data length</LI>
 901                         <LI>source_ip - Where the request came from</LI>
 902                         <LI>source_port - Where the request came from</LI>
 903                         <LI>response - Allocate a buffer and put your response in here</LI>
 904                         <LI>response_length - Length of response</LI>
 905                         <LI>send_response - true or false whether a response
 906                         should be sent.  If you set this to true, you must
 907                         allocate a response buffer.</LI>
 908                         <LI>type - Type of request (see nsctl.c)</LI>
 909                         <LI>id - ID of request</LI>
 910                         <LI>data - I'm really not sure</LI>
 911                         <LI>data_length - Length of data</LI>
 912                 </UL>
 913                 </TD>
 914         </TR>
 915 </TABLE>
 916 </TD></TR></TABLE>
 917
 918 <H2 ID="WalledGarden">Walled Garden</H2>
 919
 920 Walled Garden is implemented so that you can provide perhaps limited service
 921 to sessions that incorrectly authenticate.<P>
 922
 923 Whenever a session provides incorrect authentication, and the
 924 radius server responds with Auth-Reject, the walled garden module
 925 (if loaded) will force authentication to succeed, but set the flag
 926 <EM>garden</EM> in the session structure, and adds an iptables rule to
 927 the <B>garden_users</B> chain to force all packets for the session's IP
 928 address to traverse the <B>garden</B> chain.<P>
 929
 930 This doesn't <EM>just work</EM>.  To set this all up, you will to
 931 setup the <B>garden</B> nat table with the
 932 <A HREF="#build-garden">build-garden</A> script with rules to limit
 933 user's traffic.  For example, to force all traffic except DNS to be
 934 forwarded to 192.168.1.1, add these entries to your
 935 <EM>build-garden</EM>:
 936 <PRE>
 937 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
 938 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
 939 </PRE>
 940
 941 l2tpns will add entries to the garden_users chain as appropriate.<P>
 942
 943 You can check the amount of traffic being captured using the following
 944 command:
 945 <PRE>
 946 iptables -t nat -L garden -nvx
 947 </PRE>
 948
 949 <H2 ID="Clustering">Clustering</H2>
 950
 951 An l2tpns cluster consists of of one* or more servers configured with
 952 the same configuration, notably the multicast <B>cluster_address</B>.<P>
 953
 954 *A stand-alone server is simply a degraded cluster.<P>
 955
 956 Initially servers come up as cluster slaves, and periodically (every
 957 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
 958 containing the start time of the process to the multicast
 959 <B>cluster_address</B>.<P>
 960
 961 A cluster master sends heartbeat rather than ping packets, which
 962 contain those session and tunnel changes since the last heartbeat.<P>
 963
 964 When a slave has not seen a heartbeat within
 965 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
 966 examining the list of peers it has seen pings from and determines
 967 which of these and itself is the "best" candidate to be master.
 968 "Best" in this context means the server with the highest uptime (the
 969 highest IP address is used as a tie-breaker in the case of equal
 970 uptimes).<P>
 971
 972 After discovering a master, and determining that it is up-to-date (has
 973 seen an update for all in-use sessions and tunnels from heartbeat
 974 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
 975 the <B>bind_address</B> and for all addresses/networks in
 976 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
 977 the session state, as well as packets for throttled or gardened
 978 sessions are forwarded to the master for handling.  In addition, byte
 979 counters for session traffic are periodically forwarded.<P>
 980
 981 A master, when determining that it has at least one up-to-date slave
 982 will drop all routes (raising them again if all slaves disappear) and
 983 subsequently handle only packets forwarded to it by the slaves.<P>
 984
 985 <H2 ID="Routing">Routing</H2>
 986 If you are running a single instance, you may simply statically route
 987 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
 988 arp).<P>
 989
 990 For a cluster, configure the members as BGP neighbours on your router
 991 and configure multi-path load-balancing.  Cisco uses "maximum-paths
 992 ibgp" for IBGP.  If this is not supported by your IOS revision, you
 993 can use "maximum-paths" (which works for EBGP) and set
 994 <B>as_number</B> to a private value such as 64512.<P>
 995
 996 <H2 ID="Performance">Performance</H2>
 997
 998 Performance is great.<P>
 999
1000 I'd like to include some pretty graphs here that show a linear performance
1001 increase, with no impact by number of connected sessions.<P>
1002
1003 That's really what it looks like.<P>
1004
1005 <BR>
1006 David Parrish<BR>
1007 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1008 </BODY>
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