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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="#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 </UL>
 470
 471 <P><U><B>BGP configuration</B></U></P>
 472
 473 <P>BGP routing configuration is entered by the command:
 474 The routing configuration section is entered by the command
 475 <DL><DD><B>router bgp</B> <I>as</I></DL>
 476 where <I>as</I> specifies the local AS number.
 477
 478 <P>Subsequent lines prefixed with
 479 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 480 define the attributes of BGP neighhbours.  Valid commands are:
 481 <DL>
 482   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 483   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 484 </DL>
 485
 486 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 487 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 488 <I>hold</I> are the timer values in seconds.
 489
 490 <P>Named access-lists are configured using one of the commands:
 491 <DL>
 492   <DD><B>ip access-list standard</B> <I>name</I>
 493   <DD><B>ip access-list extended</B> <I>name</I>
 494 </DL>
 495
 496 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 497 define the body of the access-list.  Standard access-list syntax:
 498 <DL>
 499   <DD>{<B>permit</B>|<B>deny</B>}
 500     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 501     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 502 </DL>
 503
 504 Extended access-lists:
 505
 506 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 507   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 508     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 509     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 510   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 511     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 512         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 513     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 514         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 515         [<B>fragments</B>]
 516   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 517     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 518         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 519     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 520         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 521         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 522             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 523             ...|<B>fragments</B>]
 524 </DIV>
 525
 526 <H3 ID="users">users</H3>
 527
 528 Usernames and passwords for the command-line interface are stored in
 529 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 530 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 531 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 532 plain text by the prefix <B>{crypt}</B>.<P>
 533
 534 The username <B>enable</B> has a special meaning and is used to set
 535 the enable password.<P>
 536
 537 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 538 port 23 will be allowed access without a username / password.<P>
 539
 540 <H3 ID="ip-pool">ip_pool</H3>
 541
 542 This file is used to configure the IP address pool which user
 543 addresses are assigned from.  This file should contain either an IP
 544 address or a CIDR network per line.  e.g.:<P>
 545
 546 <PRE>
 547     192.168.1.1
 548     192.168.1.2
 549     192.168.1.3
 550     192.168.4.0/24
 551     172.16.0.0/16
 552     10.0.0.0/8
 553 </PRE>
 554
 555 Keep in mind that l2tpns can only handle 65535 connections per
 556 process, so don't put more than 65535 IP addresses in the
 557 configuration file.  They will be wasted.
 558
 559 <H3 ID="build-garden">build-garden</H3>
 560
 561 The garden plugin on startup creates a NAT table called "garden" then
 562 sources the <B>build-garden</B> script to populate that table.  All
 563 packets from gardened users will be sent through this table.  Example:
 564
 565 <PRE>
 566     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 567     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 568     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 569     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 570     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 571     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 572     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 573     iptables -t nat -A garden -p icmp -j ACCEPT
 574     iptables -t nat -A garden -j DROP
 575 </PRE>
 576
 577 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 578
 579 A running l2tpns process can be controlled in a number of ways.  The primary
 580 method of control is by the Command-Line Interface (CLI).<P>
 581
 582 You can also remotely send commands to modules via the nsctl client
 583 provided.<P>
 584
 585 Also, there are a number of signals that l2tpns understands and takes action
 586 when it receives them.
 587
 588 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 589
 590 You can access the command line interface by telnet'ing to port 23.
 591 There is no IP address restriction, so it's a good idea to firewall
 592 this port off from anyone who doesn't need access to it.  See
 593 <A HREF="#users">users</A> for information on restricting access based
 594 on a username and password.<P>
 595
 596 The CLI gives you real-time control over almost everything in
 597 the process.  The interface is designed to look like a Cisco
 598 device, and supports things like command history, line editing and
 599 context sensitive help.  This is provided by linking with the
 600 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 601 library.  Some general documentation of the interface is
 602 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 603 here</A>.<P>
 604
 605 After you have connected to the telnet port (and perhaps logged in), you
 606 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 607
 608 Enter <EM>help</EM> to get a list of possible commands.  A brief
 609 overview of the more important commands follows:
 610
 611 <UL>
 612 <LI><B>show session</B><BR>
 613 Without specifying a session ID, this will list all tunnels currently
 614 connected.  If you specify a session ID, you will be given all
 615 information on a single tunnel.  Note that the full session list can
 616 be around 185 columns wide, so you should probably use a wide terminal
 617 to see the list properly.<P>
 618 The columns listed in the overview are:
 619 <TABLE>
 620         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 621         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 622         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 623         authentication.  If this is *, then LCP authentication has not
 624         completed.</TD></TR>
 625         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 626         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 627         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 628         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 629         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 630         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 631         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 632         trapped in the walled garden.  This field is present even if the
 633         garden module is not loaded.</TD></TR>
 634         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 635         session started</TD></TR>
 636         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 637         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 638         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 639         detected on the session</TD></TR>
 640         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 641         connected to.</TD></TR>
 642         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 643         provided during the session setup.  This field is generated by the
 644         LAC.</TD></TR>
 645 </TABLE>
 646 <P>
 647 </LI>
 648
 649 <LI><B>show users</B><BR>
 650 With no arguments, display a list of currently connected users.  If an
 651 argument is given, the session details for the given username are
 652 displayed.
 653 </LI>
 654
 655 <LI><B>show tunnel</B><BR>
 656 This will show all the open tunnels in a summary, or detail on a single
 657 tunnel if you give a tunnel id.<P>
 658 The columns listed in the overview are:
 659 <TABLE>
 660         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 661         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 662         provided by the LAC.  This has no relation to DNS, it is just
 663         a text field.</TD></TR>
 664         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 665         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 666         Opening</TD></TR>
 667         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 668         tunnel</TD></TR>
 669 </TABLE>
 670 <P>
 671 </LI>
 672
 673 <LI><B>show pool</B><BR>
 674 Displays the current IP address pool allocation.  This will only display
 675 addresses that are in use, or are reserved for re-allocation to a
 676 disconnected user.<P>
 677 If an address is not currently in use, but has been used, then in the User
 678 column the username will be shown in square brackets, followed by the time
 679 since the address was used:
 680 <PRE>
 681 IP Address      Used  Session User
 682 192.168.100.6     N           [joe.user] 1548s
 683 </PRE>
 684 <P>
 685 </LI>
 686
 687 <LI><B>show radius</B><BR>
 688 Show a summary of the in-use RADIUS sessions.  This list should not be very
 689 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 690 columns listed are:
 691 <TABLE>
 692         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 693         sent in the packet to the RADIUS server for identification.</TD></TR>
 694         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 695         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 696         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 697         request is associated with</TD></TR>
 698         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 699         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 700         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 701         discarded after 3 retries.</TD></TR>
 702 </TABLE>
 703 <P>
 704 </LI>
 705
 706 <LI><B>show running-config</B><BR>
 707 This will list the current running configuration.  This is in a format that
 708 can either be pasted into the configuration file, or run directly at the
 709 command line.
 710 <P>
 711 </LI>
 712
 713 <LI><B>show counters</B><BR>
 714 Internally, counters are kept of key values, such as bytes and packets
 715 transferred, as well as function call counters.  This function displays all
 716 these counters, and is probably only useful for debugging.<P>
 717 You can reset these counters by running <EM>clear counters</EM>.
 718 <P>
 719 </LI>
 720
 721 <LI><B>show cluster</B><BR>
 722 Show cluster status.  Shows the cluster state for this server
 723 (Master/Slave), information about known peers and (for slaves) the
 724 master IP address, last packet seen and up-to-date status.<P>
 725 See <A HREF="#Clustering">Clustering</A> for more information.
 726 <P>
 727 </LI>
 728
 729 <LI><B>write memory</B><BR>
 730 This will write the current running configuration to the config file
 731 <B>startup-config</B>, which will be run on a restart.
 732 <P>
 733 </LI>
 734
 735 <LI><B>snoop</B><BR>
 736 You must specify a username, IP address and port.  All packets for the
 737 current session for that username will be forwarded to the given
 738 host/port.  Specify <EM>no snoop username</EM> to disable interception
 739 for the session.<P>
 740
 741 If you want interception to be permanent, you will have to modify the RADIUS
 742 response for the user.  See <A HREF="#Interception">Interception</A>.
 743 <P>
 744 </LI>
 745
 746 <LI><B>throttle</B><BR>
 747 You must specify a username, which will be throttled for the current
 748 session.  Specify <EM>no throttle username</EM> to disable throttling
 749 for the current session.<P>
 750
 751 If you want throttling to be permanent, you will have to modify the
 752 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 753 <P>
 754 </LI>
 755
 756 <LI><B>drop session</B><BR>
 757 This will cleanly disconnect a session.  You must specify a session id, which
 758 you can get from <EM>show session</EM>.  This will send a disconnect message
 759 to the remote end.
 760 <P>
 761 </LI>
 762
 763 <LI><B>drop tunnel</B><BR>
 764 This will cleanly disconnect a tunnel, as well as all sessions on that
 765 tunnel.  It will send a disconnect message for each session individually, and
 766 after 10 seconds it will send a tunnel disconnect message.
 767 <P>
 768 </LI>
 769
 770 <LI><B>uptime</B><BR>
 771 This will show how long the l2tpns process has been running, and the current
 772 bandwidth utilization:
 773 <PRE>
 774 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 775 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 776 </PRE>
 777 The bandwidth line contains 4 sets of values.<BR>
 778 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 779 (user uploads), in mbits/sec.<BR>
 780 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 781 downloads).<BR>
 782 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 783 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 784 <P>
 785 These counters are updated every second.
 786 <P>
 787 </LI>
 788
 789 <LI><B>configure terminal</B><BR>
 790 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 791 The following commands are valid in this mode:<P>
 792 </LI>
 793
 794 <LI><B>load plugin</B><BR>
 795 Load a plugin.  You must specify the plugin name, and it will search in
 796 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 797 <EM>remove plugin</EM>.
 798 <P>
 799 </LI>
 800
 801 <LI><B>set</B><BR>
 802 Set a configuration variable.  You must specify the variable name, and
 803 the value.  If the value contains any spaces, you should quote the
 804 value with double (") or single (') quotes.<P>
 805
 806 You can set any <A HREF="#startup-config">startup-config</A> value in
 807 this way, although some may require a restart to take effect.<P>
 808 </LI>
 809 </UL>
 810
 811 <H3 ID="nsctl">nsctl</H3>
 812
 813 nsctl allows messages to be passed to plugins.<P>
 814
 815 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 816 <STRONG>nsctl</STRONG>(8) for more details.<P>
 817
 818 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 819 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 820
 821 <H3 ID="Signals">Signals</H3>
 822
 823 While the process is running, you can send it a few different signals, using
 824 the kill command.
 825 <PRE>
 826 killall -HUP l2tpns
 827 </PRE>
 828
 829 The signals understood are:
 830 <DL>
 831 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 832 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 833 terminated.  This signal should be used to stop l2tpns on a
 834 <A HREF="#Clustering">cluster node</A> where there are other machines to
 835 continue handling traffic.</DD>
 836 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 837 complete.</DD>
 838 </DL>
 839
 840 <H2 ID="Throttling">Throttling</H2>
 841
 842 l2tpns contains support for slowing down user sessions to whatever speed you
 843 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 844 before this will be activated.<P>
 845
 846 If you wish a session to be throttled permanently, you should set the
 847 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 848 will be handled by the <EM>autothrottle</EM> module.<P>
 849
 850 Otherwise, you can enable and disable throttling an active session using
 851 the <EM>throttle</EM> CLI command.<P>
 852
 853 <H2 ID="Interception">Interception</H2>
 854
 855 You may have to deal with legal requirements to be able to intercept a
 856 user's traffic at any time.  l2tpns allows you to begin and end interception
 857 on the fly, as well as at authentication time.<P>
 858
 859 When a user is being intercepted, a copy of every packet they send and
 860 receive will be sent wrapped in a UDP packet to the IP address and port set
 861 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 862 variables.<P>
 863
 864 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 865
 866 To enable interception on a connected user, use the <EM>snoop username</EM>
 867 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 868 immediately.<P>
 869
 870 If you wish the user to be intercepted whenever they reconnect, you will
 871 need to modify the RADIUS response to include the Vendor-Specific value
 872 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 873 you need to have the <EM>autosnoop</EM> module loaded.<P>
 874
 875 <H2 ID="Authentication">Authentication</H2>
 876
 877 Whenever a session connects, it is not fully set up until authentication is
 878 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 879 request to l2tpns.<P>
 880
 881 This request is sent to the RADIUS server, which will hopefully respond with
 882 Auth-Accept or Auth-Reject.<P>
 883
 884 If Auth-Accept is received, the session is set up and an IP address is
 885 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 886 reply, and that address will be assigned to the client.  It can also include
 887 specific DNS servers, and a Framed-Route if that is required.<P>
 888
 889 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 890 at which point they should disconnect.  The exception to this is when the
 891 walled garden module is loaded, in which case the user still receives the
 892 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 893 should not receive any service.<P>
 894
 895 The RADIUS reply can also contain a Vendor-Specific attribute called
 896 Cisco-Avpair.  This field is a freeform text field that most Cisco
 897 devices understand to contain configuration instructions for the session.  In
 898 the case of l2tpns it is expected to be of the form
 899 <PRE>
 900 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 901 </PRE>
 902
 903 Each key-value pair is separated and passed to any modules loaded.  The
 904 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 905 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 906 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 907 contain:
 908 <PRE>
 909 intercept=yes,throttle=yes
 910 </PRE>
 911
 912 <H2 ID="Plugins">Plugins</H2>
 913
 914 So as to make l2tpns as flexible as possible (I know the core code is pretty
 915 difficult to understand), it includes a plugin API, which you can use to
 916 hook into certain events.<P>
 917
 918 There are a few example modules included - autosnoop, autothrottle and
 919 garden.<P>
 920
 921 When an event happens that has a hook, l2tpns looks for a predefined
 922 function name in every loaded module, and runs them in the order the modules
 923 were loaded.<P>
 924
 925 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 926 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 927 modules should be run for this event.<P>
 928 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 929 no further processing should be done for this event.  <EM>Use this with care.</EM>
 930
 931 Every event function called takes a specific structure named
 932 param_<EM>event</EM>, which varies in content with each event.  The
 933 function name for each event will be <B>plugin_<EM>event</EM></B>,
 934 so for the event <EM>timer</EM>, the function declaration should look like:
 935 <PRE>
 936 int plugin_timer(struct param_timer *data);
 937 </PRE>
 938
 939 A list of the available events follows, with a list of all the fields in the
 940 supplied structure:
 941 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 942 <TABLE CELLSPACING=1 CELLPADDING=3>
 943         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 944         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 945                 <TD>This is called after a RADIUS response has been
 946                 received, but before it has been processed by the
 947                 code.  This will allow you to modify the response in
 948                 some way.
 949                 </TD>
 950                 <TD>
 951                 <DL>
 952                         <DT>t<DD>Tunnel
 953                         <DT>s<DD>Session
 954                         <DT>username
 955                         <DT>password
 956                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 957                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 958                 </DL>
 959                 </TD>
 960         </TR>
 961         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 962                 <TD>This is called after a RADIUS response has been
 963                 received, and the basic checks have been performed.  This
 964                 is what the garden module uses to force authentication
 965                 to be accepted.
 966                 </TD>
 967                 <TD>
 968                 <DL>
 969                         <DT>t<DD>Tunnel
 970                         <DT>s<DD>Session
 971                         <DT>username
 972                         <DT>auth_allowed<DD>This is already set to true or
 973                         false depending on whether authentication has been
 974                         allowed so far.  You can set this to 1 or 0 to force
 975                         allow or disallow authentication
 976                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 977                 </DL>
 978                 </TD>
 979         </TR>
 980         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 981                 <TD>This is called whenever a session receives a
 982                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 983                 seriously slow down the system.</FONT>
 984                 </TD>
 985                 <TD>
 986                 <DL>
 987                         <DT>t<DD>Tunnel
 988                         <DT>s<DD>Session
 989                         <DT>buf<DD>The raw packet data
 990                         <DT>len<DD>The length of buf
 991                 </DL>
 992                 </TD>
 993         </TR>
 994         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 995                 <TD>This is called whenever a session sends a
 996                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 997                 seriously slow down the system.</FONT>
 998                 </TD>
 999                 <TD>
1000                 <DL>
1001                         <DT>t<DD>Tunnel
1002                         <DT>s<DD>Session
1003                         <DT>buf<DD>The raw packet data
1004                         <DT>len<DD>The length of buf
1005                 </DL>
1006                 </TD>
1007         </TR>
1008         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
1009                 <TD>This is run every second, no matter what is happening.
1010                 This is called from a signal handler, so make sure anything
1011                 you do is reentrant.
1012                 </TD>
1013                 <TD>
1014                 <DL>
1015                         <DT>time_now<DD>The current unix timestamp
1016                 </DL>
1017                 </TD>
1018         </TR>
1019         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
1020                 <TD>This is called after a session is fully set up.  The
1021                 session is now ready to handle traffic.
1022                 </TD>
1023                 <TD>
1024                 <DL>
1025                         <DT>t<DD>Tunnel
1026                         <DT>s<DD>Session
1027                 </DL>
1028                 </TD>
1029         </TR>
1030         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
1031                 <TD>This is called when a session is about to be shut down.
1032                 This may be called multiple times for the same session.
1033                 </TD>
1034                 <TD>
1035                 <DL>
1036                         <DT>t<DD>Tunnel
1037                         <DT>s<DD>Session
1038                 </DL>
1039                 </TD>
1040         </TR>
1041         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
1042                 <TD>This is called whenever a RADIUS response includes a
1043                 Cisco-Avpair value.  The value is split up into
1044                 <EM>key=value</EM> pairs, and each is processed through all
1045                 modules.
1046                 </TD>
1047                 <TD>
1048                 <DL>
1049                         <DT>t<DD>Tunnel
1050                         <DT>s<DD>Session
1051                         <DT>key
1052                         <DT>value
1053                 </DL>
1054                 </TD>
1055         </TR>
1056         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
1057                 <TD>This is called whenever a RADIUS CoA request is
1058                 received to reset any options to default values before
1059                 the new values are applied.
1060                 </TD>
1061                 <TD>
1062                 <DL>
1063                         <DT>t<DD>Tunnel
1064                         <DT>s<DD>Session
1065                 </DL>
1066                 </TD>
1067         </TR>
1068         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1069                 <TD>This is called in whenever a nsctl packet is received.
1070                 This should handle the packet and form a response if
1071                 required.
1072                 </TD>
1073                 <TD>
1074                 <DL>
1075                         <DT>iam_master<DD>Cluster master status
1076                         <DT>argc<DD>The number of arguments
1077                         <DT>argv<DD>Arguments
1078                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1079                         <DT>additional<DD>Extended response text
1080                 </DL>
1081                 </TD>
1082         </TR>
1083 </TABLE>
1084 </TD></TR></TABLE>
1085
1086 <H2 ID="WalledGarden">Walled Garden</H2>
1087
1088 Walled Garden is implemented so that you can provide perhaps limited service
1089 to sessions that incorrectly authenticate.<P>
1090
1091 Whenever a session provides incorrect authentication, and the
1092 RADIUS server responds with Auth-Reject, the walled garden module
1093 (if loaded) will force authentication to succeed, but set the flag
1094 <EM>garden</EM> in the session structure, and adds an iptables rule to
1095 the <B>garden_users</B> chain to force all packets for the session's IP
1096 address to traverse the <B>garden</B> chain.<P>
1097
1098 This doesn't <EM>just work</EM>.  To set this all up, you will to
1099 setup the <B>garden</B> nat table with the
1100 <A HREF="#build-garden">build-garden</A> script with rules to limit
1101 user's traffic.  For example, to force all traffic except DNS to be
1102 forwarded to 192.168.1.1, add these entries to your
1103 <EM>build-garden</EM>:
1104 <PRE>
1105 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1106 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1107 </PRE>
1108
1109 l2tpns will add entries to the garden_users chain as appropriate.<P>
1110
1111 You can check the amount of traffic being captured using the following
1112 command:
1113 <PRE>
1114 iptables -t nat -L garden -nvx
1115 </PRE>
1116
1117 <H2 ID="Filtering">Filtering</H2>
1118
1119 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1120 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1121 access-list <I>filter</I> should be applied to traffic from the
1122 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1123 customer.
1124
1125 <H2 ID="Clustering">Clustering</H2>
1126
1127 An l2tpns cluster consists of of one* or more servers configured with
1128 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1129
1130 *A stand-alone server is simply a degraded cluster.<P>
1131
1132 Initially servers come up as cluster slaves, and periodically (every
1133 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1134 containing the start time of the process to the multicast
1135 <B>cluster_address</B>.<P>
1136
1137 A cluster master sends heartbeat rather than ping packets, which
1138 contain those session and tunnel changes since the last heartbeat.<P>
1139
1140 When a slave has not seen a heartbeat within
1141 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1142 examining the list of peers it has seen pings from and determines
1143 which of these and itself is the "best" candidate to be master.
1144 "Best" in this context means the server with the highest uptime (the
1145 highest IP address is used as a tie-breaker in the case of equal
1146 uptimes).<P>
1147
1148 After discovering a master, and determining that it is up-to-date (has
1149 seen an update for all in-use sessions and tunnels from heartbeat
1150 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1151 the <B>bind_address</B> and for all addresses/networks in
1152 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1153 the session state, as well as packets for throttled or gardened
1154 sessions are forwarded to the master for handling.  In addition, byte
1155 counters for session traffic are periodically forwarded.<P>
1156
1157 A master, when determining that it has at least one up-to-date slave
1158 will drop all routes (raising them again if all slaves disappear) and
1159 subsequently handle only packets forwarded to it by the slaves.<P>
1160
1161 <H2 ID="Routing">Routing</H2>
1162 If you are running a single instance, you may simply statically route
1163 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1164 arp).<P>
1165
1166 For a cluster, configure the members as BGP neighbours on your router
1167 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1168 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1169 can use "maximum-paths" (which works for EBGP) and set
1170 <B>as_number</B> to a private value such as 64512.<P>
1171
1172 <H2 ID="Performance">Performance</H2>
1173
1174 Performance is great.<P>
1175
1176 I'd like to include some pretty graphs here that show a linear performance
1177 increase, with no impact by number of connected sessions.<P>
1178
1179 That's really what it looks like.<P>
1180
1181 <BR>
1182 David Parrish<BR>
1183 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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