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