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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>tundevicename</B> (string)<BR>
 269 Name of the tun interface (default: "tun0").
 270 </LI>
 271
 272 <LI><B>peer_address</B> (ip address)<BR>
 273 Address to send to clients as the default gateway.
 274 </LI>
 275
 276 <LI><B>send_garp</B> (boolean)<BR>
 277 Determines whether or not to send a gratuitous ARP for the
 278 bind_address when the server is ready to handle traffic (default:
 279 true).<BR>
 280 This value is ignored if BGP is configured.
 281 </LI>
 282
 283 <LI><B>throttle_speed</B> (int)<BR>
 284 Sets the default speed (in kbits/s) which sessions will be limited to.
 285 If this is set to 0, then throttling will not be used at all.  Note:
 286 You can set this by the CLI, but changes will not affect currently
 287 connected users.
 288 </LI>
 289
 290 <LI><B>throttle_buckets</B> (int)<BR>
 291 Number of token buckets to allocate for throttling.  Each throttled
 292 session requires two buckets (in and out).
 293 </LI>
 294
 295 <LI><B>accounting_dir</B> (string)<BR>
 296 If set to a directory, then every 5 minutes the current usage for
 297 every connected use will be dumped to a file in this directory.  Each
 298 file dumped begins with a header, where each line is prefixed by #.
 299 Following the header is a single line for every connected user, fields
 300 separated by a space.<BR> The fields are username, ip, qos,
 301 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 302 2 if the user is throttled.
 303 </LI>
 304
 305 <LI><B>setuid</B> (int)<BR>
 306 After starting up and binding the interface, change UID to this.  This
 307 doesn't work properly.
 308 </LI>
 309
 310 <LI><B>dump_speed</B> (boolean)<BR>
 311 If set to true, then the current bandwidth utilization will be logged every
 312 second.  Even if this is disabled, you can see this information by running
 313 the <EM>uptime</EM> command on the CLI.
 314 </LI>
 315
 316 <LI><B>multi_read_count</B> (int)<BR>
 317 Number of packets to read off each of the UDP and TUN fds when
 318 returned as readable by select (default:  10).  Avoids incurring the
 319 unnecessary system call overhead of select on busy servers.
 320 </LI>
 321
 322 <LI><B>scheduler_fifo</B> (boolean)<BR>
 323 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 324 causes the kernel to immediately preempt any currently running SCHED_OTHER
 325 (normal) process in favour of l2tpns when it becomes runnable.
 326 Ignored on uniprocessor systems.
 327 </LI>
 328
 329 <LI><B>lock_pages</B> (boolean)<BR>
 330 Keep all pages mapped by the l2tpns process in memory.
 331 </LI>
 332
 333 <LI><B>icmp_rate</B> (int)<BR>
 334 Maximum number of host unreachable ICMP packets to send per second.
 335 </LI>
 336
 337 <LI><B>packet_limit</B> (int><BR>
 338 Maximum number of packets of downstream traffic to be handled each
 339 tenth of a second per session.  If zero, no limit is applied (default:
 340 0).  Intended as a DoS prevention mechanism and not a general
 341 throttling control (packets are dropped, not queued).
 342 </LI>
 343
 344 <LI><B>cluster_address</B> (ip address)<BR>
 345 Multicast cluster address (default:  239.192.13.13).  See the section
 346 on <A HREF="#Clustering">Clustering</A> for more information.
 347 </LI>
 348
 349 <LI><B>cluster_interface</B> (string)<BR>
 350 Interface for cluster packets (default: eth0).
 351 </LI>
 352
 353 <LI><B>cluster_mcast_ttl</B> (int)<BR>
 354 TTL for multicast packets (default: 1).
 355 </LI>
 356
 357 <LI><B>cluster_hb_interval</B> (int)<BR>
 358 Interval in tenths of a second between cluster heartbeat/pings.
 359 </LI>
 360
 361 <LI><B>cluster_hb_timeout</B> (int)<BR>
 362 Cluster heartbeat timeout in tenths of a second.  A new master will be
 363 elected when this interval has been passed without seeing a heartbeat
 364 from the master.
 365 </LI>
 366
 367 <LI><B>cluster_master_min_adv</B> (int)<BR>
 368 Determines the minumum number of up to date slaves required before the
 369 master will drop routes (default: 1).
 370 </LI>
 371
 372 <LI><B>echo_timeout</B> (int)<BR>
 373 Time between last packet sent and LCP ECHO generation
 374 (default: 10 (seconds)).
 375 </LI>
 376
 377 <LI><B>idle_echo_timeout</B> (int)<BR>
 378 Drop sessions who have not responded within idle_echo_timeout seconds
 379 (default: 240 (seconds))
 380 </LI>
 381
 382 <LI><B>auth_tunnel_change_addr_src</B> (boolean)<BR>
 383 This parameter authorize to change the source IP of the tunnels l2tp.
 384 This parameter can be used when the remotes BAS/LAC are l2tpns server
 385 configured in cluster mode, but that the interface to remote LNS are
 386 not clustered (the tunnel can be coming from different source IP)
 387 (default: no).
 388 </LI>
 389
 390 <LI><B>disable_sending_hello</B> (boolean)<BR>
 391 Disable l2tp sending HELLO message for Apple compatibility.
 392 Some OS X implementation of l2tp no manage the L2TP "HELLO message".
 393 (default: no).
 394 </LI>
 395
 396 </UL>
 397
 398 <P><U><B>LAC configuration</B></U></P>
 399 <UL>
 400 <LI><B>bind_address_remotelns</B> (ip address)<BR>
 401 Address of the interface to listen the remote LNS tunnels.
 402 If no address is given, all interfaces are listened (Any Address).
 403 </LI>
 404
 405 <LI><B>bind_portremotelns</B> (short)<BR>
 406 Port to bind for the Remote LNS (default: 65432).
 407 </LI>
 408
 409 </UL>
 410
 411 <P>A static REMOTES LNS configuration can be entered by the command:</P>
 412 <DL> <DD><B>setforward</B> <I>MASK</I> <I>IP</I> <I>PORT</I> <I>SECRET</I> </DL>
 413
 414 where <I>MASK</I> specifies the mask of users who have forwarded to
 415 remote LNS (ex: "/friendISP@company.com").</BR>
 416 where <I>IP</I> specifies the IP of the  remote LNS (ex: "66.66.66.55").</BR>
 417 where <I>PORT</I> specifies the L2TP Port of the remote LNS
 418 (Normally should be 1701) (ex: 1701).</BR>
 419 where <I>SECRET</I> specifies the secret password the remote LNS (ex: mysecret).</BR>
 420 </BR>
 421 The static Remote LNS configuration can be used when the friend ISP not
 422 have a proxied Radius.</BR>
 423 If the proxied Radius is used, It will return the RADIUS attributes:</BR>
 424        Tunnel-Type: 1 = L2TP</BR>
 425        Tunnel-Medium-Type: 1 = IPv4</BR>
 426        Tunnel-Password: 1 = "LESECRETL2TP"</BR>
 427        Tunnel-Server-Endpoint: 1 = "88.xx.xx.x1"</BR>
 428        Tunnel-Assignment-Id: 1 = "friendisp_lns1"</BR>
 429        Tunnel-Type: 2 = L2TP</BR>
 430        Tunnel-Medium-Type: 2 = IPv4</BR>
 431        Tunnel-Password: 2 = "LESECRETL2TP"</BR>
 432        Tunnel-Server-Endpoint: 2 = "88.xx.xx.x2"</BR>
 433        Tunnel-Assignment-Id: 2 = "friendisp_lns2"</BR>
 434
 435 <P><U><B>PPPOE configuration</B></U></P>
 436
 437 <UL>
 438 <LI><B>pppoe_if_to_bind</B> (string)<BR>
 439 PPPOE server interface to bind (ex: "eth0.12"), If not specified the server PPPOE is not enabled.
 440 For the pppoe clustering, all the interfaces PPPOE of the clusters must use the same HW address (MAC address).
 441 </LI>
 442
 443 <LI><B>pppoe_service_name</B> (string)<BR>
 444 PPPOE service name (default: NULL).
 445 </LI>
 446
 447 <LI><B>pppoe_ac_name</B> (string)<BR>
 448 PPPOE  access concentrator name (default: "l2tpns-pppoe").
 449 </LI>
 450
 451 </UL>
 452
 453 <P><U><B>BGP configuration</B></U></P>
 454
 455 <P>BGP routing configuration is entered by the command:
 456 The routing configuration section is entered by the command
 457 <DL><DD><B>router bgp</B> <I>as</I></DL>
 458 where <I>as</I> specifies the local AS number.
 459
 460 <P>Subsequent lines prefixed with
 461 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 462 define the attributes of BGP neighhbours.  Valid commands are:
 463 <DL>
 464   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 465   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 466 </DL>
 467
 468 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 469 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 470 <I>hold</I> are the timer values in seconds.
 471
 472 <P>Named access-lists are configured using one of the commands:
 473 <DL>
 474   <DD><B>ip access-list standard</B> <I>name</I>
 475   <DD><B>ip access-list extended</B> <I>name</I>
 476 </DL>
 477
 478 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 479 define the body of the access-list.  Standard access-list syntax:
 480 <DL>
 481   <DD>{<B>permit</B>|<B>deny</B>}
 482     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 483     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 484 </DL>
 485
 486 Extended access-lists:
 487
 488 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 489   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 490     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 491     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 492   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 493     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 494         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 495     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 496         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 497         [<B>fragments</B>]
 498   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 499     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 500         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 501     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 502         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 503         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 504             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 505             ...|<B>fragments</B>]
 506 </DIV>
 507
 508 <H3 ID="users">users</H3>
 509
 510 Usernames and passwords for the command-line interface are stored in
 511 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 512 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 513 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 514 plain text by the prefix <B>{crypt}</B>.<P>
 515
 516 The username <B>enable</B> has a special meaning and is used to set
 517 the enable password.<P>
 518
 519 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 520 port 23 will be allowed access without a username / password.<P>
 521
 522 <H3 ID="ip-pool">ip_pool</H3>
 523
 524 This file is used to configure the IP address pool which user
 525 addresses are assigned from.  This file should contain either an IP
 526 address or a CIDR network per line.  e.g.:<P>
 527
 528 <PRE>
 529     192.168.1.1
 530     192.168.1.2
 531     192.168.1.3
 532     192.168.4.0/24
 533     172.16.0.0/16
 534     10.0.0.0/8
 535 </PRE>
 536
 537 Keep in mind that l2tpns can only handle 65535 connections per
 538 process, so don't put more than 65535 IP addresses in the
 539 configuration file.  They will be wasted.
 540
 541 <H3 ID="build-garden">build-garden</H3>
 542
 543 The garden plugin on startup creates a NAT table called "garden" then
 544 sources the <B>build-garden</B> script to populate that table.  All
 545 packets from gardened users will be sent through this table.  Example:
 546
 547 <PRE>
 548     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 549     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 550     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 551     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 552     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 553     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 554     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 555     iptables -t nat -A garden -p icmp -j ACCEPT
 556     iptables -t nat -A garden -j DROP
 557 </PRE>
 558
 559 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 560
 561 A running l2tpns process can be controlled in a number of ways.  The primary
 562 method of control is by the Command-Line Interface (CLI).<P>
 563
 564 You can also remotely send commands to modules via the nsctl client
 565 provided.<P>
 566
 567 Also, there are a number of signals that l2tpns understands and takes action
 568 when it receives them.
 569
 570 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 571
 572 You can access the command line interface by telnet'ing to port 23.
 573 There is no IP address restriction, so it's a good idea to firewall
 574 this port off from anyone who doesn't need access to it.  See
 575 <A HREF="#users">users</A> for information on restricting access based
 576 on a username and password.<P>
 577
 578 The CLI gives you real-time control over almost everything in
 579 the process.  The interface is designed to look like a Cisco
 580 device, and supports things like command history, line editing and
 581 context sensitive help.  This is provided by linking with the
 582 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 583 library.  Some general documentation of the interface is
 584 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 585 here</A>.<P>
 586
 587 After you have connected to the telnet port (and perhaps logged in), you
 588 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 589
 590 Enter <EM>help</EM> to get a list of possible commands.  A brief
 591 overview of the more important commands follows:
 592
 593 <UL>
 594 <LI><B>show session</B><BR>
 595 Without specifying a session ID, this will list all tunnels currently
 596 connected.  If you specify a session ID, you will be given all
 597 information on a single tunnel.  Note that the full session list can
 598 be around 185 columns wide, so you should probably use a wide terminal
 599 to see the list properly.<P>
 600 The columns listed in the overview are:
 601 <TABLE>
 602         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 603         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 604         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 605         authentication.  If this is *, then LCP authentication has not
 606         completed.</TD></TR>
 607         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 608         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 609         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 610         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 611         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 612         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 613         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 614         trapped in the walled garden.  This field is present even if the
 615         garden module is not loaded.</TD></TR>
 616         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 617         session started</TD></TR>
 618         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 619         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 620         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 621         detected on the session</TD></TR>
 622         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 623         connected to.</TD></TR>
 624         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 625         provided during the session setup.  This field is generated by the
 626         LAC.</TD></TR>
 627 </TABLE>
 628 <P>
 629 </LI>
 630
 631 <LI><B>show users</B><BR>
 632 With no arguments, display a list of currently connected users.  If an
 633 argument is given, the session details for the given username are
 634 displayed.
 635 </LI>
 636
 637 <LI><B>show tunnel</B><BR>
 638 This will show all the open tunnels in a summary, or detail on a single
 639 tunnel if you give a tunnel id.<P>
 640 The columns listed in the overview are:
 641 <TABLE>
 642         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 643         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 644         provided by the LAC.  This has no relation to DNS, it is just
 645         a text field.</TD></TR>
 646         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 647         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 648         Opening</TD></TR>
 649         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 650         tunnel</TD></TR>
 651 </TABLE>
 652 <P>
 653 </LI>
 654
 655 <LI><B>show pool</B><BR>
 656 Displays the current IP address pool allocation.  This will only display
 657 addresses that are in use, or are reserved for re-allocation to a
 658 disconnected user.<P>
 659 If an address is not currently in use, but has been used, then in the User
 660 column the username will be shown in square brackets, followed by the time
 661 since the address was used:
 662 <PRE>
 663 IP Address      Used  Session User
 664 192.168.100.6     N           [joe.user] 1548s
 665 </PRE>
 666 <P>
 667 </LI>
 668
 669 <LI><B>show radius</B><BR>
 670 Show a summary of the in-use RADIUS sessions.  This list should not be very
 671 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 672 columns listed are:
 673 <TABLE>
 674         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 675         sent in the packet to the RADIUS server for identification.</TD></TR>
 676         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 677         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 678         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 679         request is associated with</TD></TR>
 680         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 681         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 682         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 683         discarded after 3 retries.</TD></TR>
 684 </TABLE>
 685 <P>
 686 </LI>
 687
 688 <LI><B>show running-config</B><BR>
 689 This will list the current running configuration.  This is in a format that
 690 can either be pasted into the configuration file, or run directly at the
 691 command line.
 692 <P>
 693 </LI>
 694
 695 <LI><B>show counters</B><BR>
 696 Internally, counters are kept of key values, such as bytes and packets
 697 transferred, as well as function call counters.  This function displays all
 698 these counters, and is probably only useful for debugging.<P>
 699 You can reset these counters by running <EM>clear counters</EM>.
 700 <P>
 701 </LI>
 702
 703 <LI><B>show cluster</B><BR>
 704 Show cluster status.  Shows the cluster state for this server
 705 (Master/Slave), information about known peers and (for slaves) the
 706 master IP address, last packet seen and up-to-date status.<P>
 707 See <A HREF="#Clustering">Clustering</A> for more information.
 708 <P>
 709 </LI>
 710
 711 <LI><B>write memory</B><BR>
 712 This will write the current running configuration to the config file
 713 <B>startup-config</B>, which will be run on a restart.
 714 <P>
 715 </LI>
 716
 717 <LI><B>snoop</B><BR>
 718 You must specify a username, IP address and port.  All packets for the
 719 current session for that username will be forwarded to the given
 720 host/port.  Specify <EM>no snoop username</EM> to disable interception
 721 for the session.<P>
 722
 723 If you want interception to be permanent, you will have to modify the RADIUS
 724 response for the user.  See <A HREF="#Interception">Interception</A>.
 725 <P>
 726 </LI>
 727
 728 <LI><B>throttle</B><BR>
 729 You must specify a username, which will be throttled for the current
 730 session.  Specify <EM>no throttle username</EM> to disable throttling
 731 for the current session.<P>
 732
 733 If you want throttling to be permanent, you will have to modify the
 734 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 735 <P>
 736 </LI>
 737
 738 <LI><B>drop session</B><BR>
 739 This will cleanly disconnect a session.  You must specify a session id, which
 740 you can get from <EM>show session</EM>.  This will send a disconnect message
 741 to the remote end.
 742 <P>
 743 </LI>
 744
 745 <LI><B>drop tunnel</B><BR>
 746 This will cleanly disconnect a tunnel, as well as all sessions on that
 747 tunnel.  It will send a disconnect message for each session individually, and
 748 after 10 seconds it will send a tunnel disconnect message.
 749 <P>
 750 </LI>
 751
 752 <LI><B>uptime</B><BR>
 753 This will show how long the l2tpns process has been running, and the current
 754 bandwidth utilization:
 755 <PRE>
 756 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 757 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 758 </PRE>
 759 The bandwidth line contains 4 sets of values.<BR>
 760 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 761 (user uploads), in mbits/sec.<BR>
 762 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 763 downloads).<BR>
 764 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 765 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 766 <P>
 767 These counters are updated every second.
 768 <P>
 769 </LI>
 770
 771 <LI><B>configure terminal</B><BR>
 772 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 773 The following commands are valid in this mode:<P>
 774 </LI>
 775
 776 <LI><B>load plugin</B><BR>
 777 Load a plugin.  You must specify the plugin name, and it will search in
 778 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 779 <EM>remove plugin</EM>.
 780 <P>
 781 </LI>
 782
 783 <LI><B>set</B><BR>
 784 Set a configuration variable.  You must specify the variable name, and
 785 the value.  If the value contains any spaces, you should quote the
 786 value with double (") or single (') quotes.<P>
 787
 788 You can set any <A HREF="#startup-config">startup-config</A> value in
 789 this way, although some may require a restart to take effect.<P>
 790 </LI>
 791 </UL>
 792
 793 <H3 ID="nsctl">nsctl</H3>
 794
 795 nsctl allows messages to be passed to plugins.<P>
 796
 797 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 798 <STRONG>nsctl</STRONG>(8) for more details.<P>
 799
 800 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 801 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 802
 803 <H3 ID="Signals">Signals</H3>
 804
 805 While the process is running, you can send it a few different signals, using
 806 the kill command.
 807 <PRE>
 808 killall -HUP l2tpns
 809 </PRE>
 810
 811 The signals understood are:
 812 <DL>
 813 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 814 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 815 terminated.  This signal should be used to stop l2tpns on a
 816 <A HREF="#Clustering">cluster node</A> where there are other machines to
 817 continue handling traffic.</DD>
 818 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 819 complete.</DD>
 820 </DL>
 821
 822 <H2 ID="Throttling">Throttling</H2>
 823
 824 l2tpns contains support for slowing down user sessions to whatever speed you
 825 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 826 before this will be activated.<P>
 827
 828 If you wish a session to be throttled permanently, you should set the
 829 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 830 will be handled by the <EM>autothrottle</EM> module.<P>
 831
 832 Otherwise, you can enable and disable throttling an active session using
 833 the <EM>throttle</EM> CLI command.<P>
 834
 835 <H2 ID="Interception">Interception</H2>
 836
 837 You may have to deal with legal requirements to be able to intercept a
 838 user's traffic at any time.  l2tpns allows you to begin and end interception
 839 on the fly, as well as at authentication time.<P>
 840
 841 When a user is being intercepted, a copy of every packet they send and
 842 receive will be sent wrapped in a UDP packet to the IP address and port set
 843 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 844 variables.<P>
 845
 846 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 847
 848 To enable interception on a connected user, use the <EM>snoop username</EM>
 849 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 850 immediately.<P>
 851
 852 If you wish the user to be intercepted whenever they reconnect, you will
 853 need to modify the RADIUS response to include the Vendor-Specific value
 854 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 855 you need to have the <EM>autosnoop</EM> module loaded.<P>
 856
 857 <H2 ID="Authentication">Authentication</H2>
 858
 859 Whenever a session connects, it is not fully set up until authentication is
 860 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 861 request to l2tpns.<P>
 862
 863 This request is sent to the RADIUS server, which will hopefully respond with
 864 Auth-Accept or Auth-Reject.<P>
 865
 866 If Auth-Accept is received, the session is set up and an IP address is
 867 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 868 reply, and that address will be assigned to the client.  It can also include
 869 specific DNS servers, and a Framed-Route if that is required.<P>
 870
 871 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 872 at which point they should disconnect.  The exception to this is when the
 873 walled garden module is loaded, in which case the user still receives the
 874 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 875 should not receive any service.<P>
 876
 877 The RADIUS reply can also contain a Vendor-Specific attribute called
 878 Cisco-Avpair.  This field is a freeform text field that most Cisco
 879 devices understand to contain configuration instructions for the session.  In
 880 the case of l2tpns it is expected to be of the form
 881 <PRE>
 882 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 883 </PRE>
 884
 885 Each key-value pair is separated and passed to any modules loaded.  The
 886 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 887 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 888 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 889 contain:
 890 <PRE>
 891 intercept=yes,throttle=yes
 892 </PRE>
 893
 894 <H2 ID="Plugins">Plugins</H2>
 895
 896 So as to make l2tpns as flexible as possible (I know the core code is pretty
 897 difficult to understand), it includes a plugin API, which you can use to
 898 hook into certain events.<P>
 899
 900 There are a few example modules included - autosnoop, autothrottle and
 901 garden.<P>
 902
 903 When an event happens that has a hook, l2tpns looks for a predefined
 904 function name in every loaded module, and runs them in the order the modules
 905 were loaded.<P>
 906
 907 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 908 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 909 modules should be run for this event.<P>
 910 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 911 no further processing should be done for this event.  <EM>Use this with care.</EM>
 912
 913 Every event function called takes a specific structure named
 914 param_<EM>event</EM>, which varies in content with each event.  The
 915 function name for each event will be <B>plugin_<EM>event</EM></B>,
 916 so for the event <EM>timer</EM>, the function declaration should look like:
 917 <PRE>
 918 int plugin_timer(struct param_timer *data);
 919 </PRE>
 920
 921 A list of the available events follows, with a list of all the fields in the
 922 supplied structure:
 923 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 924 <TABLE CELLSPACING=1 CELLPADDING=3>
 925         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 926         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 927                 <TD>This is called after a RADIUS response has been
 928                 received, but before it has been processed by the
 929                 code.  This will allow you to modify the response in
 930                 some way.
 931                 </TD>
 932                 <TD>
 933                 <DL>
 934                         <DT>t<DD>Tunnel
 935                         <DT>s<DD>Session
 936                         <DT>username
 937                         <DT>password
 938                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 939                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 940                 </DL>
 941                 </TD>
 942         </TR>
 943         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 944                 <TD>This is called after a RADIUS response has been
 945                 received, and the basic checks have been performed.  This
 946                 is what the garden module uses to force authentication
 947                 to be accepted.
 948                 </TD>
 949                 <TD>
 950                 <DL>
 951                         <DT>t<DD>Tunnel
 952                         <DT>s<DD>Session
 953                         <DT>username
 954                         <DT>auth_allowed<DD>This is already set to true or
 955                         false depending on whether authentication has been
 956                         allowed so far.  You can set this to 1 or 0 to force
 957                         allow or disallow authentication
 958                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 959                 </DL>
 960                 </TD>
 961         </TR>
 962         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 963                 <TD>This is called whenever a session receives a
 964                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 965                 seriously slow down the system.</FONT>
 966                 </TD>
 967                 <TD>
 968                 <DL>
 969                         <DT>t<DD>Tunnel
 970                         <DT>s<DD>Session
 971                         <DT>buf<DD>The raw packet data
 972                         <DT>len<DD>The length of buf
 973                 </DL>
 974                 </TD>
 975         </TR>
 976         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 977                 <TD>This is called whenever a session sends a
 978                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 979                 seriously slow down the system.</FONT>
 980                 </TD>
 981                 <TD>
 982                 <DL>
 983                         <DT>t<DD>Tunnel
 984                         <DT>s<DD>Session
 985                         <DT>buf<DD>The raw packet data
 986                         <DT>len<DD>The length of buf
 987                 </DL>
 988                 </TD>
 989         </TR>
 990         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 991                 <TD>This is run every second, no matter what is happening.
 992                 This is called from a signal handler, so make sure anything
 993                 you do is reentrant.
 994                 </TD>
 995                 <TD>
 996                 <DL>
 997                         <DT>time_now<DD>The current unix timestamp
 998                 </DL>
 999                 </TD>
1000         </TR>
1001         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
1002                 <TD>This is called after a session is fully set up.  The
1003                 session is now ready to handle traffic.
1004                 </TD>
1005                 <TD>
1006                 <DL>
1007                         <DT>t<DD>Tunnel
1008                         <DT>s<DD>Session
1009                 </DL>
1010                 </TD>
1011         </TR>
1012         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
1013                 <TD>This is called when a session is about to be shut down.
1014                 This may be called multiple times for the same session.
1015                 </TD>
1016                 <TD>
1017                 <DL>
1018                         <DT>t<DD>Tunnel
1019                         <DT>s<DD>Session
1020                 </DL>
1021                 </TD>
1022         </TR>
1023         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
1024                 <TD>This is called whenever a RADIUS response includes a
1025                 Cisco-Avpair value.  The value is split up into
1026                 <EM>key=value</EM> pairs, and each is processed through all
1027                 modules.
1028                 </TD>
1029                 <TD>
1030                 <DL>
1031                         <DT>t<DD>Tunnel
1032                         <DT>s<DD>Session
1033                         <DT>key
1034                         <DT>value
1035                 </DL>
1036                 </TD>
1037         </TR>
1038         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
1039                 <TD>This is called whenever a RADIUS CoA request is
1040                 received to reset any options to default values before
1041                 the new values are applied.
1042                 </TD>
1043                 <TD>
1044                 <DL>
1045                         <DT>t<DD>Tunnel
1046                         <DT>s<DD>Session
1047                 </DL>
1048                 </TD>
1049         </TR>
1050         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1051                 <TD>This is called in whenever a nsctl packet is received.
1052                 This should handle the packet and form a response if
1053                 required.
1054                 </TD>
1055                 <TD>
1056                 <DL>
1057                         <DT>iam_master<DD>Cluster master status
1058                         <DT>argc<DD>The number of arguments
1059                         <DT>argv<DD>Arguments
1060                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1061                         <DT>additional<DD>Extended response text
1062                 </DL>
1063                 </TD>
1064         </TR>
1065 </TABLE>
1066 </TD></TR></TABLE>
1067
1068 <H2 ID="WalledGarden">Walled Garden</H2>
1069
1070 Walled Garden is implemented so that you can provide perhaps limited service
1071 to sessions that incorrectly authenticate.<P>
1072
1073 Whenever a session provides incorrect authentication, and the
1074 RADIUS server responds with Auth-Reject, the walled garden module
1075 (if loaded) will force authentication to succeed, but set the flag
1076 <EM>garden</EM> in the session structure, and adds an iptables rule to
1077 the <B>garden_users</B> chain to force all packets for the session's IP
1078 address to traverse the <B>garden</B> chain.<P>
1079
1080 This doesn't <EM>just work</EM>.  To set this all up, you will to
1081 setup the <B>garden</B> nat table with the
1082 <A HREF="#build-garden">build-garden</A> script with rules to limit
1083 user's traffic.  For example, to force all traffic except DNS to be
1084 forwarded to 192.168.1.1, add these entries to your
1085 <EM>build-garden</EM>:
1086 <PRE>
1087 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1088 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1089 </PRE>
1090
1091 l2tpns will add entries to the garden_users chain as appropriate.<P>
1092
1093 You can check the amount of traffic being captured using the following
1094 command:
1095 <PRE>
1096 iptables -t nat -L garden -nvx
1097 </PRE>
1098
1099 <H2 ID="Filtering">Filtering</H2>
1100
1101 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1102 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1103 access-list <I>filter</I> should be applied to traffic from the
1104 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1105 customer.
1106
1107 <H2 ID="Clustering">Clustering</H2>
1108
1109 An l2tpns cluster consists of of one* or more servers configured with
1110 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1111
1112 *A stand-alone server is simply a degraded cluster.<P>
1113
1114 Initially servers come up as cluster slaves, and periodically (every
1115 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1116 containing the start time of the process to the multicast
1117 <B>cluster_address</B>.<P>
1118
1119 A cluster master sends heartbeat rather than ping packets, which
1120 contain those session and tunnel changes since the last heartbeat.<P>
1121
1122 When a slave has not seen a heartbeat within
1123 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1124 examining the list of peers it has seen pings from and determines
1125 which of these and itself is the "best" candidate to be master.
1126 "Best" in this context means the server with the highest uptime (the
1127 highest IP address is used as a tie-breaker in the case of equal
1128 uptimes).<P>
1129
1130 After discovering a master, and determining that it is up-to-date (has
1131 seen an update for all in-use sessions and tunnels from heartbeat
1132 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1133 the <B>bind_address</B> and for all addresses/networks in
1134 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1135 the session state, as well as packets for throttled or gardened
1136 sessions are forwarded to the master for handling.  In addition, byte
1137 counters for session traffic are periodically forwarded.<P>
1138
1139 A master, when determining that it has at least one up-to-date slave
1140 will drop all routes (raising them again if all slaves disappear) and
1141 subsequently handle only packets forwarded to it by the slaves.<P>
1142
1143 <H2 ID="Routing">Routing</H2>
1144 If you are running a single instance, you may simply statically route
1145 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1146 arp).<P>
1147
1148 For a cluster, configure the members as BGP neighbours on your router
1149 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1150 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1151 can use "maximum-paths" (which works for EBGP) and set
1152 <B>as_number</B> to a private value such as 64512.<P>
1153
1154 <H2 ID="Performance">Performance</H2>
1155
1156 Performance is great.<P>
1157
1158 I'd like to include some pretty graphs here that show a linear performance
1159 increase, with no impact by number of connected sessions.<P>
1160
1161 That's really what it looks like.<P>
1162
1163 <BR>
1164 David Parrish<BR>
1165 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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