Docs/manual.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   2     "http://www.w3.org/TR/html4/loose.dtd">
   3
   4 <HTML>
   5 <HEAD>
   6 <TITLE>L2TPNS Manual</TITLE>
   7 <STYLE TYPE="text/css">
   8 H1 {
   9         text-align: center;
  10 }
  11
  12 H2 {
  13         border-top: 1px solid black;
  14         border-bottom: 1px solid black;
  15         background-color: lightblue;
  16         padding-left: 10px;
  17 }
  18
  19 H3 {
  20         text-decoration: underline;
  21 }
  22 </STYLE>
  23 </HEAD>
  24 <BODY>
  25 <H1>L2TPNS Manual</H1>
  26 <OL>
  27     <LI><A HREF="#Overview">Overview</A></LI>
  28     <LI><A HREF="#Installation">Installation</A>
  29         <OL>
  30             <LI><A HREF="#Requirements">Requirements</A></LI>
  31             <LI><A HREF="#Compile">Compile</A></LI>
  32             <LI><A HREF="#Install">Install</A></LI>
  33             <LI><A HREF="#Running">Running</A></LI>
  34         </OL>
  35     </LI>
  36     <LI><A HREF="#Configuration">Configuration</A>
  37         <OL>
  38             <LI><A HREF="#startup-config">startup-config</A></LI>
  39             <LI><A HREF="#users">users</A></LI>
  40             <LI><A HREF="#ip-pool">ip_pool</A></LI>
  41             <LI><A HREF="#build-garden">build-garden</A></LI>
  42         </OL>
  43     </LI>
  44     <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
  45         <OL>
  46             <LI><A HREF="#Command-LineInterface">Command-Line Interface</A></LI>
  47             <LI><A HREF="#nsctl">nsctl</A></LI>
  48             <LI><A HREF="#Signals">Signals</A></LI>
  49         </OL>
  50     </LI>
  51     <LI><A HREF="#Throttling">Throttling</A></LI>
  52     <LI><A HREF="#Interception">Interception</A></LI>
  53     <LI><A HREF="#Authentication">Authentication</A></LI>
  54     <LI><A HREF="#Plugins">Plugins</A></LI>
  55     <LI><A HREF="#WalledGarden">Walled Garden</A></LI>
  56     <LI><A HREF="#Filtering">Filtering</A></LI>
  57     <LI><A HREF="#Clustering">Clustering</A></LI>
  58     <LI><A HREF="#Routing">Routing</A></LI>
  59     <LI><A HREF="#Performance">Performance</A></LI>
  60 </OL>
  61
  62 <H2 ID="Overview">Overview</H2>
  63 l2tpns a complete L2TP implementation. It supports the LAC, LNS and
  64  PPPOE server.<P>
  65
  66 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
  67 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection.  l2tpns
  68 implements PPP over L2TP only.<P>
  69
  70 There are a couple of other L2TP implementations, of which <A
  71 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
  72 most popular.  l2tpd also will handle being either end of a tunnel, and
  73 is a lot more configurable than l2tpns.  However, due to the way it works,
  74 it is nowhere near as scalable.<P>
  75
  76 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
  77 and send packets.  Using some packet manipulation it doesn't require a
  78 single interface per connection, as l2tpd does.<P>
  79
  80 This allows it to scale extremely well to very high loads and very high
  81 numbers of connections.<P>
  82
  83 It also has a plugin architecture which allows custom code to be run
  84 during processing.  An example of this is in the walled garden module
  85 included.<P>
  86
  87 <BR>
  88 <EM>Documentation is not my best skill.  If you find any problems
  89 with this document, or if you wish to contribute, please email <A
  90 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
  91
  92 <H2 ID="Installation">Installation</H2>
  93 <H3 ID="Requirements">Requirements</H3>
  94
  95 <OL>
  96 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
  97 compiled in, or as a module.</LI>
  98
  99 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
 100 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
 101 </OL>
 102
 103 <H3 ID="Compile">Compile</H3>
 104
 105 You can generally get away with just running <B>make</B> from the source
 106 directory.  This will compile the daemon, associated tools and any modules
 107 shipped with the distribution.<P>
 108
 109 <H3 ID="Install">Install</H3>
 110
 111 After you have successfully compiled everything, run <B>make
 112 install</B> to install it.  By default, the binaries are installed into
 113 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
 114 modules into <EM>/usr/lib/l2tpns</EM>.<P>
 115
 116 You will definately need to edit the configuration files before you
 117 start.  See the <A HREF="#Configuration">Configuration</A> section for
 118 more information.<P>
 119
 120 <H3 ID="Running">Running</H3>
 121
 122 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it.  It does
 123 not detach to a daemon process, so you should perhaps run it from init.<P>
 124
 125 By default there is no log destination set, so all log messages will go to
 126 stdout.<P>
 127
 128 <H2 ID="Configuration">Configuration</H2>
 129
 130 All configuration of the software is done from the files installed into
 131 /etc/l2tpns.
 132
 133 <H3 ID="startup-config">startup-config</H3>
 134
 135 This is the main configuration file for l2tpns.  The format of the file is a
 136 list of commands that can be run through the command-line interface.  This
 137 file can also be written directly by the l2tpns process if a user runs the
 138 <EM>write memory</EM> command, so any comments will be lost.  However if your
 139 policy is not to write the config by the program, then feel free to comment
 140 the file with a # or ! at the beginning of the line.<P>
 141
 142 A list of the possible configuration directives follows.  Each of these
 143 should be set by a line like:<P>
 144 <PRE>
 145 set configstring "value"
 146 set ipaddress 192.168.1.1
 147 set boolean true
 148 </PRE>
 149
 150 <P>
 151 <UL>
 152 <LI><B>debug</B> (int)<BR>
 153 Sets the level of messages that will be written to the log file.  The value
 154 should be between 0 and 5, with 0 being no debugging, and 5 being the
 155 highest.  A rough description of the levels is:
 156         <OL>
 157         <LI VALUE=0>Critical Errors - Things are probably broken</LI>
 158         <LI>Errors - Things might have gone wrong, but probably will recover</LI>
 159         <LI>Warnings - Just in case you care what is not quite perfect</LI>
 160         <LI>Information - Parameters of control packets</LI>
 161         <LI>Calls - For tracing the execution of the code</LI>
 162         <LI>Packets - Everything, including a hex dump of all packets processed...  probably twice</LI>
 163         </OL><P>
 164 Note that the higher you set the debugging level, the slower the program
 165 will run.  Also, at level 5 a LOT of information will be logged.  This should
 166 only ever be used for working out why it doesn't work at all.
 167 </LI>
 168
 169 <LI><B>log_file</B> (string)<BR>
 170 This will be where all logging and debugging information is written
 171 to.  This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or
 172 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
 173 is any one of the syslog logging facilities, such as local5.
 174 </LI>
 175
 176 <LI><B>pid_file</B> (string)<BR>
 177 If set, the process id will be written to the specified file.  The
 178 value must be an absolute path.
 179 </LI>
 180
 181 <LI><B>l2tp_secret</B> (string)<BR>
 182 The secret used by l2tpns for authenticating tunnel request.  Must be
 183 the same as the LAC, or authentication will fail.  Only actually be
 184 used if the LAC requests authentication.
 185 </LI>
 186
 187 <LI><B>l2tp_mtu</B> (int)<BR>
 188 MTU of interface for L2TP traffic (default: 1500).  Used to set link
 189 MRU and adjust TCP MSS.
 190 </LI>
 191
 192 <LI><B>ppp_restart_time</B> (int)<BR>
 193 <B>ppp_max_configure</B> (int)<BR>
 194 <B>ppp_max_failure</B> (int)<BR>
 195 PPP counter and timer values, as described in &sect;4.1 of
 196 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661</a>.
 197 </LI>
 198
 199 <LI><B>primary_dns</B> (ip address)
 200 <LI><B>secondary_dns</B> (ip address)<BR>
 201 Whenever a PPP connection is established, DNS servers will be sent to the
 202 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 203 one will not be sent.
 204 </LI>
 205
 206 <LI><B>primary_radius</B> (ip address)
 207 <LI><B>secondary_radius</B> (ip address)<BR>
 208 Sets the RADIUS servers used for both authentication and accounting.
 209 If the primary server does not respond, then the secondary RADIUS
 210 server will be tried.<br>
 211 <strong>Note:</strong> in addition to the source IP address and
 212 identifier, the RADIUS server <strong>must</strong> include the source
 213 port when detecting duplicates to supress (in order to cope with a
 214 large number of sessions comming on-line simultaneously l2tpns uses a
 215 set of udp sockets, each with a seperate identifier).
 216 </LI>
 217
 218 <LI><B>primary_radius_port</B> (short)
 219 <LI><B>secondary_radius_port</B> (short)<BR>
 220 Sets the authentication ports for the primary and secondary RADIUS
 221 servers.  The accounting port is one more than the authentication
 222 port.  If no RADIUS ports are given, the authentication port defaults
 223 to 1645, and the accounting port to 1646.
 224 </LI>
 225
 226 <LI><B>radius_accounting</B> (boolean)<BR>
 227 If set to true, then RADIUS accounting packets will be sent.  This
 228 means that a Start record will be sent when the session is
 229 successfully authenticated, and a Stop record will be sent when the
 230 session is closed.
 231 </LI>
 232
 233 <LI><B>radius_secret</B> (string)<BR>
 234 This secret will be used in all RADIUS queries.  If this is not set then
 235 RADIUS queries will fail.
 236 </LI>
 237
 238 <LI><B>radius_authtypes</B> (string)</BR>
 239 A comma separated list of supported RADIUS authentication methods
 240 (<B>pap</B> or <B>chap</B>), in order of preference (default <B>pap</B>).
 241 </LI>
 242
 243 <LI><B>radius_dae_port</B> (short)<BR>
 244 Port for DAE RADIUS (Packet of Death/Disconnect, Change of Authorization)
 245 requests (default: <B>3799</B>).
 246 </LI>
 247
 248 <LI><B>allow_duplicate_users</B> (boolean)</BR>
 249 Allow multiple logins with the same username.  If false (the default),
 250 any prior session with the same username will be dropped when a new
 251 session is established.
 252 </LI>
 253
 254 <LI><B>bind_address</B> (ip address)<BR>
 255 It's the listen address of the l2tp udp protocol sent and received
 256 to LAC. This address is also assigned to the tun interface if no
 257 iftun_address is specified. Packets containing user traffic should be
 258 routed via this address if given, otherwise the primary address of the
 259 machine.
 260 </LI>
 261
 262 <LI><B>iftun_address</B> (ip address)<BR>
 263 This parameter is used when you want a tun interface address different
 264 from the address of "bind_address" (For use in cases of specific configuration).
 265 If no address is given to iftun_address and bind_address, 1.1.1.1 is used.
 266 </LI>
 267
 268 <LI><B>bind_multi_address</B> (ip address)<BR>
 269 This parameter permit to listen several addresss of the l2tp udp protocol
 270 (and set several address to the tun interface).
 271 <BR>
 272 WHEN this parameter is set, It OVERWRITE the parameters "bind_address"
 273 and "iftun_address".
 274 <BR>
 275 these can be interesting when you want do load-balancing in cluster mode
 276 of the uploaded from the LAC. For example you can set a bgp.prepend(MY_AS)
 277 for Address1 on LNS1 and a bgp.prepend(MY_AS) for Address2 on LNS2
 278 (see BGP AS-path prepending).
 279 <BR>
 280 example of use with 2 address:
 281 <BR>
 282 set bind_multi_address "64.14.13.41, 64.14.13.42"
 283
 284 </LI>
 285
 286 <LI><B>tundevicename</B> (string)<BR>
 287 Name of the tun interface (default: "tun0").
 288 </LI>
 289
 290 <LI><B>peer_address</B> (ip address)<BR>
 291 Address to send to clients as the default gateway.
 292 </LI>
 293
 294 <LI><B>send_garp</B> (boolean)<BR>
 295 Determines whether or not to send a gratuitous ARP for the
 296 bind_address when the server is ready to handle traffic (default:
 297 true).<BR>
 298 This value is ignored if BGP is configured.
 299 </LI>
 300
 301 <LI><B>throttle_speed</B> (int)<BR>
 302 Sets the default speed (in kbits/s) which sessions will be limited to.
 303 If this is set to 0, then throttling will not be used at all.  Note:
 304 You can set this by the CLI, but changes will not affect currently
 305 connected users.
 306 </LI>
 307
 308 <LI><B>throttle_buckets</B> (int)<BR>
 309 Number of token buckets to allocate for throttling.  Each throttled
 310 session requires two buckets (in and out).
 311 </LI>
 312
 313 <LI><B>accounting_dir</B> (string)<BR>
 314 If set to a directory, then every 5 minutes the current usage for
 315 every connected use will be dumped to a file in this directory.  Each
 316 file dumped begins with a header, where each line is prefixed by #.
 317 Following the header is a single line for every connected user, fields
 318 separated by a space.<BR> The fields are username, ip, qos,
 319 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 320 2 if the user is throttled.
 321 </LI>
 322
 323 <LI><B>setuid</B> (int)<BR>
 324 After starting up and binding the interface, change UID to this.  This
 325 doesn't work properly.
 326 </LI>
 327
 328 <LI><B>dump_speed</B> (boolean)<BR>
 329 If set to true, then the current bandwidth utilization will be logged every
 330 second.  Even if this is disabled, you can see this information by running
 331 the <EM>uptime</EM> command on the CLI.
 332 </LI>
 333
 334 <LI><B>multi_read_count</B> (int)<BR>
 335 Number of packets to read off each of the UDP and TUN fds when
 336 returned as readable by select (default:  10).  Avoids incurring the
 337 unnecessary system call overhead of select on busy servers.
 338 </LI>
 339
 340 <LI><B>scheduler_fifo</B> (boolean)<BR>
 341 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 342 causes the kernel to immediately preempt any currently running SCHED_OTHER
 343 (normal) process in favour of l2tpns when it becomes runnable.
 344 Ignored on uniprocessor systems.
 345 </LI>
 346
 347 <LI><B>lock_pages</B> (boolean)<BR>
 348 Keep all pages mapped by the l2tpns process in memory.
 349 </LI>
 350
 351 <LI><B>icmp_rate</B> (int)<BR>
 352 Maximum number of host unreachable ICMP packets to send per second.
 353 </LI>
 354
 355 <LI><B>packet_limit</B> (int><BR>
 356 Maximum number of packets of downstream traffic to be handled each
 357 tenth of a second per session.  If zero, no limit is applied (default:
 358 0).  Intended as a DoS prevention mechanism and not a general
 359 throttling control (packets are dropped, not queued).
 360 </LI>
 361
 362 <LI><B>cluster_address</B> (ip address)<BR>
 363 Multicast cluster address (default:  239.192.13.13).  See the section
 364 on <A HREF="#Clustering">Clustering</A> for more information.
 365 </LI>
 366
 367 <LI><B>cluster_interface</B> (string)<BR>
 368 Interface for cluster packets (default: eth0).
 369 </LI>
 370
 371 <LI><B>cluster_mcast_ttl</B> (int)<BR>
 372 TTL for multicast packets (default: 1).
 373 </LI>
 374
 375 <LI><B>cluster_hb_interval</B> (int)<BR>
 376 Interval in tenths of a second between cluster heartbeat/pings.
 377 </LI>
 378
 379 <LI><B>cluster_hb_timeout</B> (int)<BR>
 380 Cluster heartbeat timeout in tenths of a second.  A new master will be
 381 elected when this interval has been passed without seeing a heartbeat
 382 from the master.
 383 </LI>
 384
 385 <LI><B>cluster_master_min_adv</B> (int)<BR>
 386 Determines the minumum number of up to date slaves required before the
 387 master will drop routes (default: 1).
 388 </LI>
 389
 390 <LI><B>echo_timeout</B> (int)<BR>
 391 Time between last packet sent and LCP ECHO generation
 392 (default: 10 (seconds)).
 393 </LI>
 394
 395 <LI><B>idle_echo_timeout</B> (int)<BR>
 396 Drop sessions who have not responded within idle_echo_timeout seconds
 397 (default: 240 (seconds))
 398 </LI>
 399
 400 <LI><B>auth_tunnel_change_addr_src</B> (boolean)<BR>
 401 This parameter authorize to change the source IP of the tunnels l2tp.
 402 This parameter can be used when the remotes BAS/LAC are l2tpns server
 403 configured in cluster mode, but that the interface to remote LNS are
 404 not clustered (the tunnel can be coming from different source IP)
 405 (default: no).
 406 </LI>
 407
 408 <LI><B>disable_sending_hello</B> (boolean)<BR>
 409 Disable l2tp sending HELLO message for Apple compatibility.
 410 Some OS X implementation of l2tp no manage the L2TP "HELLO message".
 411 (default: no).
 412 </LI>
 413
 414 </UL>
 415
 416 <P><U><B>LAC configuration</B></U></P>
 417 <UL>
 418 <LI><B>bind_address_remotelns</B> (ip address)<BR>
 419 Address of the interface to listen the remote LNS tunnels.
 420 If no address is given, all interfaces are listened (Any Address).
 421 </LI>
 422
 423 <LI><B>bind_portremotelns</B> (short)<BR>
 424 Port to bind for the Remote LNS (default: 65432).
 425 </LI>
 426
 427 </UL>
 428
 429 <P>A static REMOTES LNS configuration can be entered by the command:</P>
 430 <DL> <DD><B>setforward</B> <I>MASK</I> <I>IP</I> <I>PORT</I> <I>SECRET</I> </DL>
 431
 432 where <I>MASK</I> specifies the mask of users who have forwarded to
 433 remote LNS (ex: "/friendISP@company.com").</BR>
 434 where <I>IP</I> specifies the IP of the  remote LNS (ex: "66.66.66.55").</BR>
 435 where <I>PORT</I> specifies the L2TP Port of the remote LNS
 436 (Normally should be 1701) (ex: 1701).</BR>
 437 where <I>SECRET</I> specifies the secret password the remote LNS (ex: mysecret).</BR>
 438 </BR>
 439 The static Remote LNS configuration can be used when the friend ISP not
 440 have a proxied Radius.</BR>
 441 If the proxied Radius is used, It will return the RADIUS attributes:</BR>
 442        Tunnel-Type: 1 = L2TP</BR>
 443        Tunnel-Medium-Type: 1 = IPv4</BR>
 444        Tunnel-Password: 1 = "LESECRETL2TP"</BR>
 445        Tunnel-Server-Endpoint: 1 = "88.xx.xx.x1"</BR>
 446        Tunnel-Assignment-Id: 1 = "friendisp_lns1"</BR>
 447        Tunnel-Type: 2 = L2TP</BR>
 448        Tunnel-Medium-Type: 2 = IPv4</BR>
 449        Tunnel-Password: 2 = "LESECRETL2TP"</BR>
 450        Tunnel-Server-Endpoint: 2 = "88.xx.xx.x2"</BR>
 451        Tunnel-Assignment-Id: 2 = "friendisp_lns2"</BR>
 452
 453 <P><U><B>PPPOE configuration</B></U></P>
 454
 455 <UL>
 456 <LI><B>pppoe_if_to_bind</B> (string)<BR>
 457 PPPOE server interface to bind (ex: "eth0.12"), If not specified the server PPPOE is not enabled.
 458 For the pppoe clustering, all the interfaces PPPOE of the clusters must use the same HW address (MAC address).
 459 </LI>
 460
 461 <LI><B>pppoe_service_name</B> (string)<BR>
 462 PPPOE service name (default: NULL).
 463 </LI>
 464
 465 <LI><B>pppoe_ac_name</B> (string)<BR>
 466 PPPOE  access concentrator name (default: "l2tpns-pppoe").
 467 </LI>
 468
 469 <LI><B>pppoe_only_equal_svc_name</B> (boolean)<BR>
 470 If set to yes, the PPPOE server only accepts clients with a "service-name"
 471 different from NULL and a "service-name" equal to server "service-name" (default: no).
 472 </LI>
 473
 474 </UL>
 475
 476 <P><U><B>BGP configuration</B></U></P>
 477
 478 <P>BGP routing configuration is entered by the command:
 479 The routing configuration section is entered by the command
 480 <DL><DD><B>router bgp</B> <I>as</I></DL>
 481 where <I>as</I> specifies the local AS number.
 482
 483 <P>Subsequent lines prefixed with
 484 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 485 define the attributes of BGP neighhbours.  Valid commands are:
 486 <DL>
 487   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 488   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 489 </DL>
 490
 491 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 492 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 493 <I>hold</I> are the timer values in seconds.
 494
 495 <P>Named access-lists are configured using one of the commands:
 496 <DL>
 497   <DD><B>ip access-list standard</B> <I>name</I>
 498   <DD><B>ip access-list extended</B> <I>name</I>
 499 </DL>
 500
 501 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 502 define the body of the access-list.  Standard access-list syntax:
 503 <DL>
 504   <DD>{<B>permit</B>|<B>deny</B>}
 505     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 506     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 507 </DL>
 508
 509 Extended access-lists:
 510
 511 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 512   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 513     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 514     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 515   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 516     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 517         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 518     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 519         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 520         [<B>fragments</B>]
 521   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 522     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 523         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 524     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 525         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 526         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 527             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 528             ...|<B>fragments</B>]
 529 </DIV>
 530
 531 <H3 ID="users">users</H3>
 532
 533 Usernames and passwords for the command-line interface are stored in
 534 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 535 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 536 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 537 plain text by the prefix <B>{crypt}</B>.<P>
 538
 539 The username <B>enable</B> has a special meaning and is used to set
 540 the enable password.<P>
 541
 542 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 543 port 23 will be allowed access without a username / password.<P>
 544
 545 <H3 ID="ip-pool">ip_pool</H3>
 546
 547 This file is used to configure the IP address pool which user
 548 addresses are assigned from.  This file should contain either an IP
 549 address or a CIDR network per line.  e.g.:<P>
 550
 551 <PRE>
 552     192.168.1.1
 553     192.168.1.2
 554     192.168.1.3
 555     192.168.4.0/24
 556     172.16.0.0/16
 557     10.0.0.0/8
 558 </PRE>
 559
 560 Keep in mind that l2tpns can only handle 65535 connections per
 561 process, so don't put more than 65535 IP addresses in the
 562 configuration file.  They will be wasted.
 563
 564 <H3 ID="build-garden">build-garden</H3>
 565
 566 The garden plugin on startup creates a NAT table called "garden" then
 567 sources the <B>build-garden</B> script to populate that table.  All
 568 packets from gardened users will be sent through this table.  Example:
 569
 570 <PRE>
 571     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 572     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 573     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 574     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 575     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 576     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 577     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 578     iptables -t nat -A garden -p icmp -j ACCEPT
 579     iptables -t nat -A garden -j DROP
 580 </PRE>
 581
 582 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 583
 584 A running l2tpns process can be controlled in a number of ways.  The primary
 585 method of control is by the Command-Line Interface (CLI).<P>
 586
 587 You can also remotely send commands to modules via the nsctl client
 588 provided.<P>
 589
 590 Also, there are a number of signals that l2tpns understands and takes action
 591 when it receives them.
 592
 593 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 594
 595 You can access the command line interface by telnet'ing to port 23.
 596 There is no IP address restriction, so it's a good idea to firewall
 597 this port off from anyone who doesn't need access to it.  See
 598 <A HREF="#users">users</A> for information on restricting access based
 599 on a username and password.<P>
 600
 601 The CLI gives you real-time control over almost everything in
 602 the process.  The interface is designed to look like a Cisco
 603 device, and supports things like command history, line editing and
 604 context sensitive help.  This is provided by linking with the
 605 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 606 library.  Some general documentation of the interface is
 607 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 608 here</A>.<P>
 609
 610 After you have connected to the telnet port (and perhaps logged in), you
 611 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 612
 613 Enter <EM>help</EM> to get a list of possible commands.  A brief
 614 overview of the more important commands follows:
 615
 616 <UL>
 617 <LI><B>show session</B><BR>
 618 Without specifying a session ID, this will list all tunnels currently
 619 connected.  If you specify a session ID, you will be given all
 620 information on a single tunnel.  Note that the full session list can
 621 be around 185 columns wide, so you should probably use a wide terminal
 622 to see the list properly.<P>
 623 The columns listed in the overview are:
 624 <TABLE>
 625         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 626         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 627         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 628         authentication.  If this is *, then LCP authentication has not
 629         completed.</TD></TR>
 630         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 631         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 632         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 633         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 634         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 635         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 636         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 637         trapped in the walled garden.  This field is present even if the
 638         garden module is not loaded.</TD></TR>
 639         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 640         session started</TD></TR>
 641         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 642         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 643         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 644         detected on the session</TD></TR>
 645         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 646         connected to.</TD></TR>
 647         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 648         provided during the session setup.  This field is generated by the
 649         LAC.</TD></TR>
 650 </TABLE>
 651 <P>
 652 </LI>
 653
 654 <LI><B>show users</B><BR>
 655 With no arguments, display a list of currently connected users.  If an
 656 argument is given, the session details for the given username are
 657 displayed.
 658 </LI>
 659
 660 <LI><B>show tunnel</B><BR>
 661 This will show all the open tunnels in a summary, or detail on a single
 662 tunnel if you give a tunnel id.<P>
 663 The columns listed in the overview are:
 664 <TABLE>
 665         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 666         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 667         provided by the LAC.  This has no relation to DNS, it is just
 668         a text field.</TD></TR>
 669         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 670         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 671         Opening</TD></TR>
 672         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 673         tunnel</TD></TR>
 674 </TABLE>
 675 <P>
 676 </LI>
 677
 678 <LI><B>show pool</B><BR>
 679 Displays the current IP address pool allocation.  This will only display
 680 addresses that are in use, or are reserved for re-allocation to a
 681 disconnected user.<P>
 682 If an address is not currently in use, but has been used, then in the User
 683 column the username will be shown in square brackets, followed by the time
 684 since the address was used:
 685 <PRE>
 686 IP Address      Used  Session User
 687 192.168.100.6     N           [joe.user] 1548s
 688 </PRE>
 689 <P>
 690 </LI>
 691
 692 <LI><B>show radius</B><BR>
 693 Show a summary of the in-use RADIUS sessions.  This list should not be very
 694 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 695 columns listed are:
 696 <TABLE>
 697         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 698         sent in the packet to the RADIUS server for identification.</TD></TR>
 699         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 700         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 701         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 702         request is associated with</TD></TR>
 703         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 704         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 705         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 706         discarded after 3 retries.</TD></TR>
 707 </TABLE>
 708 <P>
 709 </LI>
 710
 711 <LI><B>show running-config</B><BR>
 712 This will list the current running configuration.  This is in a format that
 713 can either be pasted into the configuration file, or run directly at the
 714 command line.
 715 <P>
 716 </LI>
 717
 718 <LI><B>show counters</B><BR>
 719 Internally, counters are kept of key values, such as bytes and packets
 720 transferred, as well as function call counters.  This function displays all
 721 these counters, and is probably only useful for debugging.<P>
 722 You can reset these counters by running <EM>clear counters</EM>.
 723 <P>
 724 </LI>
 725
 726 <LI><B>show cluster</B><BR>
 727 Show cluster status.  Shows the cluster state for this server
 728 (Master/Slave), information about known peers and (for slaves) the
 729 master IP address, last packet seen and up-to-date status.<P>
 730 See <A HREF="#Clustering">Clustering</A> for more information.
 731 <P>
 732 </LI>
 733
 734 <LI><B>write memory</B><BR>
 735 This will write the current running configuration to the config file
 736 <B>startup-config</B>, which will be run on a restart.
 737 <P>
 738 </LI>
 739
 740 <LI><B>snoop</B><BR>
 741 You must specify a username, IP address and port.  All packets for the
 742 current session for that username will be forwarded to the given
 743 host/port.  Specify <EM>no snoop username</EM> to disable interception
 744 for the session.<P>
 745
 746 If you want interception to be permanent, you will have to modify the RADIUS
 747 response for the user.  See <A HREF="#Interception">Interception</A>.
 748 <P>
 749 </LI>
 750
 751 <LI><B>throttle</B><BR>
 752 You must specify a username, which will be throttled for the current
 753 session.  Specify <EM>no throttle username</EM> to disable throttling
 754 for the current session.<P>
 755
 756 If you want throttling to be permanent, you will have to modify the
 757 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 758 <P>
 759 </LI>
 760
 761 <LI><B>drop session</B><BR>
 762 This will cleanly disconnect a session.  You must specify a session id, which
 763 you can get from <EM>show session</EM>.  This will send a disconnect message
 764 to the remote end.
 765 <P>
 766 </LI>
 767
 768 <LI><B>drop tunnel</B><BR>
 769 This will cleanly disconnect a tunnel, as well as all sessions on that
 770 tunnel.  It will send a disconnect message for each session individually, and
 771 after 10 seconds it will send a tunnel disconnect message.
 772 <P>
 773 </LI>
 774
 775 <LI><B>uptime</B><BR>
 776 This will show how long the l2tpns process has been running, and the current
 777 bandwidth utilization:
 778 <PRE>
 779 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 780 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 781 </PRE>
 782 The bandwidth line contains 4 sets of values.<BR>
 783 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 784 (user uploads), in mbits/sec.<BR>
 785 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 786 downloads).<BR>
 787 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 788 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 789 <P>
 790 These counters are updated every second.
 791 <P>
 792 </LI>
 793
 794 <LI><B>configure terminal</B><BR>
 795 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 796 The following commands are valid in this mode:<P>
 797 </LI>
 798
 799 <LI><B>load plugin</B><BR>
 800 Load a plugin.  You must specify the plugin name, and it will search in
 801 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 802 <EM>remove plugin</EM>.
 803 <P>
 804 </LI>
 805
 806 <LI><B>set</B><BR>
 807 Set a configuration variable.  You must specify the variable name, and
 808 the value.  If the value contains any spaces, you should quote the
 809 value with double (") or single (') quotes.<P>
 810
 811 You can set any <A HREF="#startup-config">startup-config</A> value in
 812 this way, although some may require a restart to take effect.<P>
 813 </LI>
 814 </UL>
 815
 816 <H3 ID="nsctl">nsctl</H3>
 817
 818 nsctl allows messages to be passed to plugins.<P>
 819
 820 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 821 <STRONG>nsctl</STRONG>(8) for more details.<P>
 822
 823 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 824 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 825
 826 <H3 ID="Signals">Signals</H3>
 827
 828 While the process is running, you can send it a few different signals, using
 829 the kill command.
 830 <PRE>
 831 killall -HUP l2tpns
 832 </PRE>
 833
 834 The signals understood are:
 835 <DL>
 836 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 837 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 838 terminated.  This signal should be used to stop l2tpns on a
 839 <A HREF="#Clustering">cluster node</A> where there are other machines to
 840 continue handling traffic.</DD>
 841 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 842 complete.</DD>
 843 </DL>
 844
 845 <H2 ID="Throttling">Throttling</H2>
 846
 847 l2tpns contains support for slowing down user sessions to whatever speed you
 848 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 849 before this will be activated.<P>
 850
 851 If you wish a session to be throttled permanently, you should set the
 852 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 853 will be handled by the <EM>autothrottle</EM> module.<P>
 854
 855 Otherwise, you can enable and disable throttling an active session using
 856 the <EM>throttle</EM> CLI command.<P>
 857
 858 <H2 ID="Interception">Interception</H2>
 859
 860 You may have to deal with legal requirements to be able to intercept a
 861 user's traffic at any time.  l2tpns allows you to begin and end interception
 862 on the fly, as well as at authentication time.<P>
 863
 864 When a user is being intercepted, a copy of every packet they send and
 865 receive will be sent wrapped in a UDP packet to the IP address and port set
 866 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 867 variables.<P>
 868
 869 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 870
 871 To enable interception on a connected user, use the <EM>snoop username</EM>
 872 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 873 immediately.<P>
 874
 875 If you wish the user to be intercepted whenever they reconnect, you will
 876 need to modify the RADIUS response to include the Vendor-Specific value
 877 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 878 you need to have the <EM>autosnoop</EM> module loaded.<P>
 879
 880 <H2 ID="Authentication">Authentication</H2>
 881
 882 Whenever a session connects, it is not fully set up until authentication is
 883 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 884 request to l2tpns.<P>
 885
 886 This request is sent to the RADIUS server, which will hopefully respond with
 887 Auth-Accept or Auth-Reject.<P>
 888
 889 If Auth-Accept is received, the session is set up and an IP address is
 890 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 891 reply, and that address will be assigned to the client.  It can also include
 892 specific DNS servers, and a Framed-Route if that is required.<P>
 893
 894 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 895 at which point they should disconnect.  The exception to this is when the
 896 walled garden module is loaded, in which case the user still receives the
 897 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 898 should not receive any service.<P>
 899
 900 The RADIUS reply can also contain a Vendor-Specific attribute called
 901 Cisco-Avpair.  This field is a freeform text field that most Cisco
 902 devices understand to contain configuration instructions for the session.  In
 903 the case of l2tpns it is expected to be of the form
 904 <PRE>
 905 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 906 </PRE>
 907
 908 Each key-value pair is separated and passed to any modules loaded.  The
 909 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 910 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 911 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 912 contain:
 913 <PRE>
 914 intercept=yes,throttle=yes
 915 </PRE>
 916
 917 <H2 ID="Plugins">Plugins</H2>
 918
 919 So as to make l2tpns as flexible as possible (I know the core code is pretty
 920 difficult to understand), it includes a plugin API, which you can use to
 921 hook into certain events.<P>
 922
 923 There are a few example modules included - autosnoop, autothrottle and
 924 garden.<P>
 925
 926 When an event happens that has a hook, l2tpns looks for a predefined
 927 function name in every loaded module, and runs them in the order the modules
 928 were loaded.<P>
 929
 930 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 931 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 932 modules should be run for this event.<P>
 933 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 934 no further processing should be done for this event.  <EM>Use this with care.</EM>
 935
 936 Every event function called takes a specific structure named
 937 param_<EM>event</EM>, which varies in content with each event.  The
 938 function name for each event will be <B>plugin_<EM>event</EM></B>,
 939 so for the event <EM>timer</EM>, the function declaration should look like:
 940 <PRE>
 941 int plugin_timer(struct param_timer *data);
 942 </PRE>
 943
 944 A list of the available events follows, with a list of all the fields in the
 945 supplied structure:
 946 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 947 <TABLE CELLSPACING=1 CELLPADDING=3>
 948         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 949         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 950                 <TD>This is called after a RADIUS response has been
 951                 received, but before it has been processed by the
 952                 code.  This will allow you to modify the response in
 953                 some way.
 954                 </TD>
 955                 <TD>
 956                 <DL>
 957                         <DT>t<DD>Tunnel
 958                         <DT>s<DD>Session
 959                         <DT>username
 960                         <DT>password
 961                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 962                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 963                 </DL>
 964                 </TD>
 965         </TR>
 966         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 967                 <TD>This is called after a RADIUS response has been
 968                 received, and the basic checks have been performed.  This
 969                 is what the garden module uses to force authentication
 970                 to be accepted.
 971                 </TD>
 972                 <TD>
 973                 <DL>
 974                         <DT>t<DD>Tunnel
 975                         <DT>s<DD>Session
 976                         <DT>username
 977                         <DT>auth_allowed<DD>This is already set to true or
 978                         false depending on whether authentication has been
 979                         allowed so far.  You can set this to 1 or 0 to force
 980                         allow or disallow authentication
 981                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 982                 </DL>
 983                 </TD>
 984         </TR>
 985         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 986                 <TD>This is called whenever a session receives a
 987                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 988                 seriously slow down the system.</FONT>
 989                 </TD>
 990                 <TD>
 991                 <DL>
 992                         <DT>t<DD>Tunnel
 993                         <DT>s<DD>Session
 994                         <DT>buf<DD>The raw packet data
 995                         <DT>len<DD>The length of buf
 996                 </DL>
 997                 </TD>
 998         </TR>
 999         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
1000                 <TD>This is called whenever a session sends a
1001                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
1002                 seriously slow down the system.</FONT>
1003                 </TD>
1004                 <TD>
1005                 <DL>
1006                         <DT>t<DD>Tunnel
1007                         <DT>s<DD>Session
1008                         <DT>buf<DD>The raw packet data
1009                         <DT>len<DD>The length of buf
1010                 </DL>
1011                 </TD>
1012         </TR>
1013         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
1014                 <TD>This is run every second, no matter what is happening.
1015                 This is called from a signal handler, so make sure anything
1016                 you do is reentrant.
1017                 </TD>
1018                 <TD>
1019                 <DL>
1020                         <DT>time_now<DD>The current unix timestamp
1021                 </DL>
1022                 </TD>
1023         </TR>
1024         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
1025                 <TD>This is called after a session is fully set up.  The
1026                 session is now ready to handle traffic.
1027                 </TD>
1028                 <TD>
1029                 <DL>
1030                         <DT>t<DD>Tunnel
1031                         <DT>s<DD>Session
1032                 </DL>
1033                 </TD>
1034         </TR>
1035         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
1036                 <TD>This is called when a session is about to be shut down.
1037                 This may be called multiple times for the same session.
1038                 </TD>
1039                 <TD>
1040                 <DL>
1041                         <DT>t<DD>Tunnel
1042                         <DT>s<DD>Session
1043                 </DL>
1044                 </TD>
1045         </TR>
1046         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
1047                 <TD>This is called whenever a RADIUS response includes a
1048                 Cisco-Avpair value.  The value is split up into
1049                 <EM>key=value</EM> pairs, and each is processed through all
1050                 modules.
1051                 </TD>
1052                 <TD>
1053                 <DL>
1054                         <DT>t<DD>Tunnel
1055                         <DT>s<DD>Session
1056                         <DT>key
1057                         <DT>value
1058                 </DL>
1059                 </TD>
1060         </TR>
1061         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
1062                 <TD>This is called whenever a RADIUS CoA request is
1063                 received to reset any options to default values before
1064                 the new values are applied.
1065                 </TD>
1066                 <TD>
1067                 <DL>
1068                         <DT>t<DD>Tunnel
1069                         <DT>s<DD>Session
1070                 </DL>
1071                 </TD>
1072         </TR>
1073         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1074                 <TD>This is called in whenever a nsctl packet is received.
1075                 This should handle the packet and form a response if
1076                 required.
1077                 </TD>
1078                 <TD>
1079                 <DL>
1080                         <DT>iam_master<DD>Cluster master status
1081                         <DT>argc<DD>The number of arguments
1082                         <DT>argv<DD>Arguments
1083                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1084                         <DT>additional<DD>Extended response text
1085                 </DL>
1086                 </TD>
1087         </TR>
1088 </TABLE>
1089 </TD></TR></TABLE>
1090
1091 <H2 ID="WalledGarden">Walled Garden</H2>
1092
1093 Walled Garden is implemented so that you can provide perhaps limited service
1094 to sessions that incorrectly authenticate.<P>
1095
1096 Whenever a session provides incorrect authentication, and the
1097 RADIUS server responds with Auth-Reject, the walled garden module
1098 (if loaded) will force authentication to succeed, but set the flag
1099 <EM>garden</EM> in the session structure, and adds an iptables rule to
1100 the <B>garden_users</B> chain to force all packets for the session's IP
1101 address to traverse the <B>garden</B> chain.<P>
1102
1103 This doesn't <EM>just work</EM>.  To set this all up, you will to
1104 setup the <B>garden</B> nat table with the
1105 <A HREF="#build-garden">build-garden</A> script with rules to limit
1106 user's traffic.  For example, to force all traffic except DNS to be
1107 forwarded to 192.168.1.1, add these entries to your
1108 <EM>build-garden</EM>:
1109 <PRE>
1110 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1111 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1112 </PRE>
1113
1114 l2tpns will add entries to the garden_users chain as appropriate.<P>
1115
1116 You can check the amount of traffic being captured using the following
1117 command:
1118 <PRE>
1119 iptables -t nat -L garden -nvx
1120 </PRE>
1121
1122 <H2 ID="Filtering">Filtering</H2>
1123
1124 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1125 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1126 access-list <I>filter</I> should be applied to traffic from the
1127 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1128 customer.
1129
1130 <H2 ID="Clustering">Clustering</H2>
1131
1132 An l2tpns cluster consists of of one* or more servers configured with
1133 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1134
1135 *A stand-alone server is simply a degraded cluster.<P>
1136
1137 Initially servers come up as cluster slaves, and periodically (every
1138 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1139 containing the start time of the process to the multicast
1140 <B>cluster_address</B>.<P>
1141
1142 A cluster master sends heartbeat rather than ping packets, which
1143 contain those session and tunnel changes since the last heartbeat.<P>
1144
1145 When a slave has not seen a heartbeat within
1146 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1147 examining the list of peers it has seen pings from and determines
1148 which of these and itself is the "best" candidate to be master.
1149 "Best" in this context means the server with the highest uptime (the
1150 highest IP address is used as a tie-breaker in the case of equal
1151 uptimes).<P>
1152
1153 After discovering a master, and determining that it is up-to-date (has
1154 seen an update for all in-use sessions and tunnels from heartbeat
1155 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1156 the <B>bind_address</B> and for all addresses/networks in
1157 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1158 the session state, as well as packets for throttled or gardened
1159 sessions are forwarded to the master for handling.  In addition, byte
1160 counters for session traffic are periodically forwarded.<P>
1161
1162 A master, when determining that it has at least one up-to-date slave
1163 will drop all routes (raising them again if all slaves disappear) and
1164 subsequently handle only packets forwarded to it by the slaves.<P>
1165
1166 <H2 ID="Routing">Routing</H2>
1167 If you are running a single instance, you may simply statically route
1168 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1169 arp).<P>
1170
1171 For a cluster, configure the members as BGP neighbours on your router
1172 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1173 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1174 can use "maximum-paths" (which works for EBGP) and set
1175 <B>as_number</B> to a private value such as 64512.<P>
1176
1177 <H2 ID="Performance">Performance</H2>
1178
1179 Performance is great.<P>
1180
1181 I'd like to include some pretty graphs here that show a linear performance
1182 increase, with no impact by number of connected sessions.<P>
1183
1184 That's really what it looks like.<P>
1185
1186 <BR>
1187 David Parrish<BR>
1188 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1189 </BODY>
1190 </HTML>