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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, PPPOE and DHCPv6 server.<P>
  64
  65 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns implements PPP over L2TP only.<P>
  66
  67 There are a couple of other L2TP implementations, of which <A HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the most popular.  l2tpd also will handle being either end of a tunnel, and is a lot more configurable than l2tpns.  However, due to the way it works, it is nowhere near as scalable.<P>
  68
  69 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive and send packets.  Using some packet manipulation it doesn't require a single interface per connection, as l2tpd does.<P>
  70
  71 This allows it to scale extremely well to very high loads and very high numbers of connections.<P>
  72
  73 It also has a plugin architecture which allows custom code to be run during processing.  An example of this is in the walled garden module included.<P>
  74
  75 <BR>
  76 <EM>Documentation is not my best skill.  If you find any problems
  77 with this document, or if you wish to contribute, please email <A
  78 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
  79
  80 <H2 ID="Installation">Installation</H2>
  81 <H3 ID="Requirements">Requirements</H3>
  82
  83 <OL>
  84 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
  85 compiled in, or as a module.</LI>
  86
  87 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
  88 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
  89 </OL>
  90
  91 <H3 ID="Compile">Compile</H3>
  92
  93 You can generally get away with just running <B>make</B> from the source
  94 directory.  This will compile the daemon, associated tools and any modules
  95 shipped with the distribution.<P>
  96
  97 <H3 ID="Install">Install</H3>
  98
  99 After you have successfully compiled everything, run <B>make
 100 install</B> to install it.  By default, the binaries are installed into
 101 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
 102 modules into <EM>/usr/lib/l2tpns</EM>.<P>
 103
 104 You will definately need to edit the configuration files before you
 105 start.  See the <A HREF="#Configuration">Configuration</A> section for
 106 more information.<P>
 107
 108 <H3 ID="Running">Running</H3>
 109
 110 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it.  It does
 111 not detach to a daemon process, so you should perhaps run it from init.<P>
 112
 113 By default there is no log destination set, so all log messages will go to
 114 stdout.<P>
 115
 116 <H2 ID="Configuration">Configuration</H2>
 117
 118 All configuration of the software is done from the files installed into
 119 /etc/l2tpns.
 120
 121 <H3 ID="startup-config">startup-config</H3>
 122
 123 This is the main configuration file for l2tpns.  The format of the file is a
 124 list of commands that can be run through the command-line interface.  This
 125 file can also be written directly by the l2tpns process if a user runs the
 126 <EM>write memory</EM> command, so any comments will be lost.  However if your
 127 policy is not to write the config by the program, then feel free to comment
 128 the file with a # or ! at the beginning of the line.<P>
 129
 130 A list of the possible configuration directives follows.  Each of these
 131 should be set by a line like:<P>
 132 <PRE>
 133 set configstring "value"
 134 set ipaddress 192.168.1.1
 135 set boolean true
 136 </PRE>
 137
 138 <P>
 139 <UL>
 140 <LI><B>debug</B> (int)<BR>
 141 Sets the level of messages that will be written to the log file.  The value
 142 should be between 0 and 5, with 0 being no debugging, and 5 being the
 143 highest.  A rough description of the levels is:
 144         <OL>
 145         <LI VALUE=0>Critical Errors - Things are probably broken</LI>
 146         <LI>Errors - Things might have gone wrong, but probably will recover</LI>
 147         <LI>Warnings - Just in case you care what is not quite perfect</LI>
 148         <LI>Information - Parameters of control packets</LI>
 149         <LI>Calls - For tracing the execution of the code</LI>
 150         <LI>Packets - Everything, including a hex dump of all packets processed...  probably twice</LI>
 151         </OL><P>
 152 Note that the higher you set the debugging level, the slower the program
 153 will run.  Also, at level 5 a LOT of information will be logged.  This should
 154 only ever be used for working out why it doesn't work at all.
 155 </LI>
 156
 157 <LI><B>log_file</B> (string)<BR>
 158 This will be where all logging and debugging information is written to. This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM> is any one of the syslog logging facilities, such as local5.
 159 </LI>
 160
 161 <LI><B>pid_file</B> (string)<BR>
 162 If set, the process id will be written to the specified file.  The value must be an absolute path.
 163 </LI>
 164
 165 <LI><B>random_device</B>B> (string)<BR>
 166 Path to random data source (default /dev/urandom). Use "" to use the rand() library function.
 167 </LI>
 168
 169 <LI><B>l2tp_secret</B> (string)<BR>
 170 The secret used by l2tpns for authenticating tunnel request.  Must be
 171 the same as the LAC, or authentication will fail.  Only actually be
 172 used if the LAC requests authentication.
 173 </LI>
 174
 175 <LI><B>l2tp_mtu</B> (int)<BR>
 176 MTU of interface for L2TP traffic (default: 1500). Used to set link MRU and adjust TCP MSS.
 177 </LI>
 178
 179 <LI><B>ppp_restart_time</B> (int)<BR>
 180 <B>ppp_max_configure</B> (int)<BR>
 181 <B>ppp_max_failure</B> (int)<BR>
 182 PPP counter and timer values, as described in &sect;4.1 of
 183 <a href="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">RFC1661</a>.
 184 </LI>
 185
 186 <LI><B>primary_dns</B> (ip address)
 187 <LI><B>secondary_dns</B> (ip address)<BR>
 188 Whenever a PPP connection is established, DNS servers will be sent to the
 189 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 190 one will not be sent.
 191 </LI>
 192
 193 <LI><B>primary_radius</B> (ip address)
 194 <LI><B>secondary_radius</B> (ip address)<BR>
 195 Sets the RADIUS servers used for both authentication and accounting.
 196 If the primary server does not respond, then the secondary RADIUS
 197 server will be tried.<br>
 198 <strong>Note:</strong> in addition to the source IP address and
 199 identifier, the RADIUS server <strong>must</strong> include the source
 200 port when detecting duplicates to supress (in order to cope with a
 201 large number of sessions comming on-line simultaneously l2tpns uses a
 202 set of udp sockets, each with a seperate identifier).
 203 </LI>
 204
 205 <LI><B>primary_radius_port</B> (short)
 206 <LI><B>secondary_radius_port</B> (short)<BR>
 207 Sets the authentication ports for the primary and secondary RADIUS
 208 servers.  The accounting port is one more than the authentication
 209 port.  If no RADIUS ports are given, the authentication port defaults
 210 to 1645, and the accounting port to 1646.
 211 </LI>
 212
 213 <LI><B>radius_accounting</B> (boolean)<BR>
 214 If set to true, then RADIUS accounting packets will be sent.  This
 215 means that a Start record will be sent when the session is
 216 successfully authenticated, and a Stop record will be sent when the
 217 session is closed.
 218 </LI>
 219
 220 <LI><B>radius_secret</B> (string)<BR>
 221 This secret will be used in all RADIUS queries. If this is not set then RADIUS queries will fail.
 222 </LI>
 223
 224 <LI><B>radius_authtypes</B> (string)</BR>
 225 A comma separated list of supported RADIUS authentication methods
 226 (<B>pap</B> or <B>chap</B>), in order of preference (default <B>pap</B>).
 227 </LI>
 228
 229 <LI><B>radius_dae_port</B> (short)<BR>
 230 Port for DAE RADIUS (Packet of Death/Disconnect, Change of Authorization)
 231 requests (default: <B>3799</B>).
 232 </LI>
 233
 234 <LI><B>allow_duplicate_users</B> (boolean)</BR>
 235 Allow multiple logins with the same username.  If false (the default),
 236 any prior session with the same username will be dropped when a new
 237 session is established.
 238 </LI>
 239
 240 <LI><B>bind_address</B> (ip address)<BR>
 241 It's the listen address of the l2tp udp protocol sent and received to LAC. This address is also assigned to the tun interface if no iftun_address is specified. Packets containing user traffic should be routed via this address if given, otherwise the primary address of the machine.
 242 </LI>
 243
 244 <LI><B>iftun_address</B> (ip address)<BR>
 245 This parameter is used when you want a tun interface address different
 246 from the address of "bind_address" (For use in cases of specific configuration).
 247 If no address is given to iftun_address and bind_address, 1.1.1.1 is used.
 248 </LI>
 249
 250 <LI><B>bind_multi_address</B> (ip address)<BR>
 251 This parameter permit to listen several addresss of the l2tp udp protocol
 252 (and set several address to the tun interface).
 253 <BR>
 254 WHEN this parameter is set, It OVERWRITE the parameters "bind_address"
 255 and "iftun_address".
 256 <BR>
 257 these can be interesting when you want do load-balancing in cluster mode
 258 of the uploaded from the LAC. For example you can set a bgp.prepend(MY_AS)
 259 for Address1 on LNS1 and a bgp.prepend(MY_AS) for Address2 on LNS2
 260 (see BGP AS-path prepending).
 261 <BR>
 262 example of use with 2 address:
 263 <BR>
 264 set bind_multi_address "64.14.13.41, 64.14.13.42"
 265 </LI>
 266
 267 <LI><B>tundevicename</B> (string)<BR>
 268 Name of the tun interface (default: "tun0").
 269 </LI>
 270
 271 <LI><B>peer_address</B> (ip address)<BR>
 272 Address to send to clients as the default gateway.
 273 </LI>
 274
 275 <LI><B>send_garp</B> (boolean)<BR>
 276 Determines whether or not to send a gratuitous ARP for the
 277 bind_address when the server is ready to handle traffic (default:
 278 true).<BR>
 279 This value is ignored if BGP is configured.
 280 </LI>
 281
 282 <LI><B>throttle_speed</B> (int)<BR>
 283 Sets the default speed (in kbits/s) which sessions will be limited to.
 284 If this is set to 0, then throttling will not be used at all.  Note:
 285 You can set this by the CLI, but changes will not affect currently
 286 connected users.
 287 </LI>
 288
 289 <LI><B>throttle_buckets</B> (int)<BR>
 290 Number of token buckets to allocate for throttling.  Each throttled
 291 session requires two buckets (in and out).
 292 </LI>
 293
 294 <LI><B>accounting_dir</B> (string)<BR>
 295 If set to a directory, then every 5 minutes the current usage for
 296 every connected use will be dumped to a file in this directory.  Each
 297 file dumped begins with a header, where each line is prefixed by #.
 298 Following the header is a single line for every connected user, fields
 299 separated by a space.<BR> The fields are username, ip, qos,
 300 uptxoctets, downrxoctets, origin (optional). The qos field is 1 if a standard user, and
 301 2 if the user is throttled. The origin field is dump if account_all_origin is set to true
 302 (origin value: L=LAC data, R=Remote LNS data, P=PPPOE data).
 303 </LI>
 304
 305 <LI><B>account_all_origin</B> (boolean)<BR>
 306 If set to true, all origin of the usage is dumped to the accounting file (LAC+Remote LNS+PPPOE)(default false).
 307 </LI>
 308
 309 <LI><B>dump_speed</B> (boolean)<BR>
 310 If set to true, then the current bandwidth utilization will be logged every
 311 second.  Even if this is disabled, you can see this information by running
 312 the <EM>uptime</EM> command on the CLI.
 313 </LI>
 314
 315 <LI><B>multi_read_count</B> (int)<BR>
 316 Number of packets to read off each of the UDP and TUN fds when
 317 returned as readable by select (default:  10).  Avoids incurring the
 318 unnecessary system call overhead of select on busy servers.
 319 </LI>
 320
 321 <LI><B>scheduler_fifo</B> (boolean)<BR>
 322 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 323 causes the kernel to immediately preempt any currently running SCHED_OTHER
 324 (normal) process in favour of l2tpns when it becomes runnable.
 325 Ignored on uniprocessor systems.
 326 </LI>
 327
 328 <LI><B>lock_pages</B> (boolean)<BR>
 329 Keep all pages mapped by the l2tpns process in memory.
 330 </LI>
 331
 332 <LI><B>icmp_rate</B> (int)<BR>
 333 Maximum number of host unreachable ICMP packets to send per second.
 334 </LI>
 335
 336 <LI><B>packet_limit</B> (int><BR>
 337 Maximum number of packets of downstream traffic to be handled each
 338 tenth of a second per session.  If zero, no limit is applied (default:
 339 0).  Intended as a DoS prevention mechanism and not a general
 340 throttling control (packets are dropped, not queued).
 341 </LI>
 342
 343 <LI><B>cluster_address</B> (ip address)<BR>
 344 Multicast cluster address (default:  239.192.13.13).  See the section
 345 on <A HREF="#Clustering">Clustering</A> for more information.
 346 </LI>
 347
 348 <LI><B>cluster_interface</B> (string)<BR>
 349 Interface for cluster packets (default: eth0).
 350 </LI>
 351
 352 <LI><B>cluster_mcast_ttl</B> (int)<BR>
 353 TTL for multicast packets (default: 1).
 354 </LI>
 355
 356 <LI><B>cluster_hb_interval</B> (int)<BR>
 357 Interval in tenths of a second between cluster heartbeat/pings.
 358 </LI>
 359
 360 <LI><B>cluster_hb_timeout</B> (int)<BR>
 361 Cluster heartbeat timeout in tenths of a second.  A new master will be
 362 elected when this interval has been passed without seeing a heartbeat
 363 from the master.
 364 </LI>
 365
 366 <LI><B>cluster_master_min_adv</B> (int)<BR>
 367 Determines the minumum number of up to date slaves required before the
 368 master will drop routes (default: 1).
 369 </LI>
 370
 371 <LI><B>echo_timeout</B> (int)<BR>
 372 Time between last packet sent and LCP ECHO generation
 373 (default: 10 (seconds)).
 374 </LI>
 375
 376 <LI><B>idle_echo_timeout</B> (int)<BR>
 377 Drop sessions who have not responded within idle_echo_timeout seconds
 378 (default: 240 (seconds))
 379 </LI>
 380
 381 <LI><B>auth_tunnel_change_addr_src</B> (boolean)<BR>
 382 This parameter authorize to change the source IP of the tunnels l2tp.
 383 This parameter can be used when the remotes BAS/LAC are l2tpns server
 384 configured in cluster mode, but that the interface to remote LNS are
 385 not clustered (the tunnel can be coming from different source IP)
 386 (default: no).
 387 </LI>
 388
 389 <LI><B>disable_sending_hello</B> (boolean)<BR>
 390 Disable l2tp sending HELLO message for Apple compatibility.
 391 Some OS X implementation of l2tp no manage the L2TP "HELLO message".
 392 (default: no).
 393 </LI>
 394
 395 </UL>
 396
 397 <P><U><B>LAC configuration</B></U></P>
 398 <UL>
 399 <LI><B>bind_address_remotelns</B> (ip address)<BR>
 400 Address of the interface to listen the remote LNS tunnels.
 401 If no address is given, all interfaces are listened (Any Address).
 402 </LI>
 403
 404 <LI><B>bind_portremotelns</B> (short)<BR>
 405 Port to bind for the Remote LNS (default: 65432).
 406 </LI>
 407
 408 </UL>
 409
 410 <P>A static REMOTES LNS configuration can be entered by the command:</P>
 411 <DL> <DD><B>setforward</B> <I>MASK</I> <I>IP</I> <I>PORT</I> <I>SECRET</I> </DL>
 412
 413 where <I>MASK</I> specifies the mask of users who have forwarded to
 414 remote LNS (ex: "/friendISP@company.com").</BR>
 415 where <I>IP</I> specifies the IP of the  remote LNS (ex: "66.66.66.55").</BR>
 416 where <I>PORT</I> specifies the L2TP Port of the remote LNS
 417 (Normally should be 1701) (ex: 1701).</BR>
 418 where <I>SECRET</I> specifies the secret password the remote LNS (ex: mysecret).</BR>
 419 </BR>
 420 The static Remote LNS configuration can be used when the friend ISP not
 421 have a proxied Radius.</BR>
 422 If the proxied Radius is used, It will return the RADIUS attributes:</BR>
 423        Tunnel-Type: 1 = L2TP</BR>
 424        Tunnel-Medium-Type: 1 = IPv4</BR>
 425        Tunnel-Password: 1 = "LESECRETL2TP"</BR>
 426        Tunnel-Server-Endpoint: 1 = "88.xx.xx.x1"</BR>
 427        Tunnel-Assignment-Id: 1 = "friendisp_lns1"</BR>
 428        Tunnel-Type: 2 = L2TP</BR>
 429        Tunnel-Medium-Type: 2 = IPv4</BR>
 430        Tunnel-Password: 2 = "LESECRETL2TP"</BR>
 431        Tunnel-Server-Endpoint: 2 = "88.xx.xx.x2"</BR>
 432        Tunnel-Assignment-Id: 2 = "friendisp_lns2"</BR>
 433
 434 <P><U><B>PPPOE configuration</B></U></P>
 435
 436 <UL>
 437 <LI><B>pppoe_if_to_bind</B> (string)<BR>
 438 PPPOE server interface to bind (ex: "eth0.12"), If not specified the server PPPOE is not enabled.
 439 For the pppoe clustering, all the interfaces PPPOE of the clusters must use the same HW address (MAC address).
 440 </LI>
 441
 442 <LI><B>pppoe_service_name</B> (string)<BR>
 443 PPPOE service name (default: NULL).
 444 </LI>
 445
 446 <LI><B>pppoe_ac_name</B> (string)<BR>
 447 PPPOE  access concentrator name (default: "l2tpns-pppoe").
 448 </LI>
 449
 450 <LI><B>pppoe_only_equal_svc_name</B> (boolean)<BR>
 451 If set to yes, the PPPOE server only accepts clients with a "service-name"
 452 different from NULL and a "service-name" equal to server "service-name" (default: no).
 453 </LI>
 454
 455 </UL>
 456
 457 <P><U><B>BGP configuration</B></U></P>
 458
 459 <P>BGP routing configuration is entered by the command:
 460 The routing configuration section is entered by the command
 461 <DL><DD><B>router bgp</B> <I>as</I></DL>
 462 where <I>as</I> specifies the local AS number.
 463
 464 <P>Subsequent lines prefixed with
 465 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 466 define the attributes of BGP neighhbours.  Valid commands are:
 467 <DL>
 468   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 469   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 470 </DL>
 471
 472 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 473 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 474 <I>hold</I> are the timer values in seconds.
 475
 476 <P>Named access-lists are configured using one of the commands:
 477 <DL>
 478   <DD><B>ip access-list standard</B> <I>name</I>
 479   <DD><B>ip access-list extended</B> <I>name</I>
 480 </DL>
 481
 482 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 483 define the body of the access-list.  Standard access-list syntax:
 484 <DL>
 485   <DD>{<B>permit</B>|<B>deny</B>}
 486     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 487     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 488 </DL>
 489
 490 Extended access-lists:
 491
 492 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 493   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 494     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 495     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 496   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 497     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 498         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 499     {<I>host</I>|<I>destination destination-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         [<B>fragments</B>]
 502   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 503     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 504         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 505     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 506         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 507         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 508             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 509             ...|<B>fragments</B>]
 510 </DIV>
 511
 512 <H3 ID="users">users</H3>
 513
 514 Usernames and passwords for the command-line interface are stored in
 515 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 516 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 517 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 518 plain text by the prefix <B>{crypt}</B>.<P>
 519
 520 The username <B>enable</B> has a special meaning and is used to set
 521 the enable password.<P>
 522
 523 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 524 port 23 will be allowed access without a username / password.<P>
 525
 526 <H3 ID="ip-pool">ip_pool</H3>
 527
 528 This file is used to configure the IP address pool which user
 529 addresses are assigned from.  This file should contain either an IP
 530 address or a CIDR network per line.  e.g.:<P>
 531
 532 <PRE>
 533     192.168.1.1
 534     192.168.1.2
 535     192.168.1.3
 536     192.168.4.0/24
 537     172.16.0.0/16
 538     10.0.0.0/8
 539 </PRE>
 540
 541 Keep in mind that l2tpns can only handle 65535 connections per
 542 process, so don't put more than 65535 IP addresses in the
 543 configuration file.  They will be wasted.
 544
 545 <H3 ID="build-garden">build-garden</H3>
 546
 547 The garden plugin on startup creates a NAT table called "garden" then
 548 sources the <B>build-garden</B> script to populate that table.  All
 549 packets from gardened users will be sent through this table.  Example:
 550
 551 <PRE>
 552     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 553     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 554     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 555     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 556     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 557     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 558     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 559     iptables -t nat -A garden -p icmp -j ACCEPT
 560     iptables -t nat -A garden -j DROP
 561 </PRE>
 562
 563 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 564
 565 A running l2tpns process can be controlled in a number of ways.  The primary
 566 method of control is by the Command-Line Interface (CLI).<P>
 567
 568 You can also remotely send commands to modules via the nsctl client
 569 provided.<P>
 570
 571 Also, there are a number of signals that l2tpns understands and takes action
 572 when it receives them.
 573
 574 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 575
 576 You can access the command line interface by telnet'ing to port 23.
 577 There is no IP address restriction, so it's a good idea to firewall
 578 this port off from anyone who doesn't need access to it.  See
 579 <A HREF="#users">users</A> for information on restricting access based
 580 on a username and password.<P>
 581
 582 The CLI gives you real-time control over almost everything in
 583 the process.  The interface is designed to look like a Cisco
 584 device, and supports things like command history, line editing and
 585 context sensitive help.  This is provided by linking with the
 586 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 587 library.  Some general documentation of the interface is
 588 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 589 here</A>.<P>
 590
 591 After you have connected to the telnet port (and perhaps logged in), you
 592 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 593
 594 Enter <EM>help</EM> to get a list of possible commands.  A brief
 595 overview of the more important commands follows:
 596
 597 <UL>
 598 <LI><B>show session</B><BR>
 599 Without specifying a session ID, this will list all tunnels currently
 600 connected.  If you specify a session ID, you will be given all
 601 information on a single tunnel.  Note that the full session list can
 602 be around 185 columns wide, so you should probably use a wide terminal
 603 to see the list properly.<P>
 604 The columns listed in the overview are:
 605 <TABLE>
 606         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 607         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 608         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 609         authentication.  If this is *, then LCP authentication has not
 610         completed.</TD></TR>
 611         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 612         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 613         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 614         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 615         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 616         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 617         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 618         trapped in the walled garden.  This field is present even if the
 619         garden module is not loaded.</TD></TR>
 620         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 621         session started</TD></TR>
 622         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 623         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 624         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 625         detected on the session</TD></TR>
 626         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 627         connected to.</TD></TR>
 628         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 629         provided during the session setup.  This field is generated by the
 630         LAC.</TD></TR>
 631 </TABLE>
 632 <P>
 633 </LI>
 634
 635 <LI><B>show users</B><BR>
 636 With no arguments, display a list of currently connected users.  If an
 637 argument is given, the session details for the given username are
 638 displayed.
 639 </LI>
 640
 641 <LI><B>show tunnel</B><BR>
 642 This will show all the open tunnels in a summary, or detail on a single
 643 tunnel if you give a tunnel id.<P>
 644 The columns listed in the overview are:
 645 <TABLE>
 646         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 647         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 648         provided by the LAC.  This has no relation to DNS, it is just
 649         a text field.</TD></TR>
 650         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 651         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 652         Opening</TD></TR>
 653         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 654         tunnel</TD></TR>
 655 </TABLE>
 656 <P>
 657 </LI>
 658
 659 <LI><B>show pool</B><BR>
 660 Displays the current IP address pool allocation.  This will only display
 661 addresses that are in use, or are reserved for re-allocation to a
 662 disconnected user.<P>
 663 If an address is not currently in use, but has been used, then in the User
 664 column the username will be shown in square brackets, followed by the time
 665 since the address was used:
 666 <PRE>
 667 IP Address      Used  Session User
 668 192.168.100.6     N           [joe.user] 1548s
 669 </PRE>
 670 <P>
 671 </LI>
 672
 673 <LI><B>show radius</B><BR>
 674 Show a summary of the in-use RADIUS sessions.  This list should not be very
 675 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 676 columns listed are:
 677 <TABLE>
 678         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 679         sent in the packet to the RADIUS server for identification.</TD></TR>
 680         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 681         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 682         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 683         request is associated with</TD></TR>
 684         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 685         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 686         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 687         discarded after 3 retries.</TD></TR>
 688 </TABLE>
 689 <P>
 690 </LI>
 691
 692 <LI><B>show running-config</B><BR>
 693 This will list the current running configuration.  This is in a format that
 694 can either be pasted into the configuration file, or run directly at the
 695 command line.
 696 <P>
 697 </LI>
 698
 699 <LI><B>show counters</B><BR>
 700 Internally, counters are kept of key values, such as bytes and packets
 701 transferred, as well as function call counters.  This function displays all
 702 these counters, and is probably only useful for debugging.<P>
 703 You can reset these counters by running <EM>clear counters</EM>.
 704 <P>
 705 </LI>
 706
 707 <LI><B>show cluster</B><BR>
 708 Show cluster status.  Shows the cluster state for this server
 709 (Master/Slave), information about known peers and (for slaves) the
 710 master IP address, last packet seen and up-to-date status.<P>
 711 See <A HREF="#Clustering">Clustering</A> for more information.
 712 <P>
 713 </LI>
 714
 715 <LI><B>write memory</B><BR>
 716 This will write the current running configuration to the config file
 717 <B>startup-config</B>, which will be run on a restart.
 718 <P>
 719 </LI>
 720
 721 <LI><B>snoop</B><BR>
 722 You must specify a username, IP address and port.  All packets for the
 723 current session for that username will be forwarded to the given
 724 host/port.  Specify <EM>no snoop username</EM> to disable interception
 725 for the session.<P>
 726
 727 If you want interception to be permanent, you will have to modify the RADIUS
 728 response for the user.  See <A HREF="#Interception">Interception</A>.
 729 <P>
 730 </LI>
 731
 732 <LI><B>throttle</B><BR>
 733 You must specify a username, which will be throttled for the current
 734 session.  Specify <EM>no throttle username</EM> to disable throttling
 735 for the current session.<P>
 736
 737 If you want throttling to be permanent, you will have to modify the
 738 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 739 <P>
 740 </LI>
 741
 742 <LI><B>drop session</B><BR>
 743 This will cleanly disconnect a session.  You must specify a session id, which
 744 you can get from <EM>show session</EM>.  This will send a disconnect message
 745 to the remote end.
 746 <P>
 747 </LI>
 748
 749 <LI><B>drop tunnel</B><BR>
 750 This will cleanly disconnect a tunnel, as well as all sessions on that
 751 tunnel.  It will send a disconnect message for each session individually, and
 752 after 10 seconds it will send a tunnel disconnect message.
 753 <P>
 754 </LI>
 755
 756 <LI><B>uptime</B><BR>
 757 This will show how long the l2tpns process has been running, and the current
 758 bandwidth utilization:
 759 <PRE>
 760 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 761 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 762 </PRE>
 763 The bandwidth line contains 4 sets of values.<BR>
 764 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 765 (user uploads), in mbits/sec.<BR>
 766 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 767 downloads).<BR>
 768 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 769 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 770 <P>
 771 These counters are updated every second.
 772 <P>
 773 </LI>
 774
 775 <LI><B>configure terminal</B><BR>
 776 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 777 The following commands are valid in this mode:<P>
 778 </LI>
 779
 780 <LI><B>load plugin</B><BR>
 781 Load a plugin.  You must specify the plugin name, and it will search in
 782 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 783 <EM>remove plugin</EM>.
 784 <P>
 785 </LI>
 786
 787 <LI><B>set</B><BR>
 788 Set a configuration variable.  You must specify the variable name, and
 789 the value.  If the value contains any spaces, you should quote the
 790 value with double (") or single (') quotes.<P>
 791
 792 You can set any <A HREF="#startup-config">startup-config</A> value in
 793 this way, although some may require a restart to take effect.<P>
 794 </LI>
 795 </UL>
 796
 797 <H3 ID="nsctl">nsctl</H3>
 798
 799 nsctl allows messages to be passed to plugins.<P>
 800
 801 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 802 <STRONG>nsctl</STRONG>(8) for more details.<P>
 803
 804 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 805 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 806
 807 <H3 ID="Signals">Signals</H3>
 808
 809 While the process is running, you can send it a few different signals, using
 810 the kill command.
 811 <PRE>
 812 killall -HUP l2tpns
 813 </PRE>
 814
 815 The signals understood are:
 816 <DL>
 817 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 818 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 819 terminated.  This signal should be used to stop l2tpns on a
 820 <A HREF="#Clustering">cluster node</A> where there are other machines to
 821 continue handling traffic.</DD>
 822 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 823 complete.</DD>
 824 </DL>
 825
 826 <H2 ID="Throttling">Throttling</H2>
 827
 828 l2tpns contains support for slowing down user sessions to whatever speed you
 829 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 830 before this will be activated.<P>
 831
 832 If you wish a session to be throttled permanently, you should set the
 833 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 834 will be handled by the <EM>autothrottle</EM> module.<P>
 835
 836 Otherwise, you can enable and disable throttling an active session using
 837 the <EM>throttle</EM> CLI command.<P>
 838
 839 <H2 ID="Interception">Interception</H2>
 840
 841 You may have to deal with legal requirements to be able to intercept a
 842 user's traffic at any time.  l2tpns allows you to begin and end interception
 843 on the fly, as well as at authentication time.<P>
 844
 845 When a user is being intercepted, a copy of every packet they send and
 846 receive will be sent wrapped in a UDP packet to the IP address and port set
 847 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 848 variables.<P>
 849
 850 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 851
 852 To enable interception on a connected user, use the <EM>snoop username</EM>
 853 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 854 immediately.<P>
 855
 856 If you wish the user to be intercepted whenever they reconnect, you will
 857 need to modify the RADIUS response to include the Vendor-Specific value
 858 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 859 you need to have the <EM>autosnoop</EM> module loaded.<P>
 860
 861 <H2 ID="Authentication">Authentication</H2>
 862
 863 Whenever a session connects, it is not fully set up until authentication is
 864 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 865 request to l2tpns.<P>
 866
 867 This request is sent to the RADIUS server, which will hopefully respond with
 868 Auth-Accept or Auth-Reject.<P>
 869
 870 If Auth-Accept is received, the session is set up and an IP address is
 871 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 872 reply, and that address will be assigned to the client.  It can also include
 873 specific DNS servers, and a Framed-Route if that is required.<P>
 874
 875 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 876 at which point they should disconnect.  The exception to this is when the
 877 walled garden module is loaded, in which case the user still receives the
 878 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 879 should not receive any service.<P>
 880
 881 The RADIUS reply can also contain a Vendor-Specific attribute called
 882 Cisco-Avpair.  This field is a freeform text field that most Cisco
 883 devices understand to contain configuration instructions for the session.  In
 884 the case of l2tpns it is expected to be of the form
 885 <PRE>
 886 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 887 </PRE>
 888
 889 Each key-value pair is separated and passed to any modules loaded.  The
 890 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 891 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 892 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 893 contain:
 894 <PRE>
 895 intercept=yes,throttle=yes
 896 </PRE>
 897
 898 <H2 ID="Plugins">Plugins</H2>
 899
 900 So as to make l2tpns as flexible as possible (I know the core code is pretty
 901 difficult to understand), it includes a plugin API, which you can use to
 902 hook into certain events.<P>
 903
 904 There are a few example modules included - autosnoop, autothrottle and
 905 garden.<P>
 906
 907 When an event happens that has a hook, l2tpns looks for a predefined
 908 function name in every loaded module, and runs them in the order the modules
 909 were loaded.<P>
 910
 911 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 912 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 913 modules should be run for this event.<P>
 914 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 915 no further processing should be done for this event.  <EM>Use this with care.</EM>
 916
 917 Every event function called takes a specific structure named
 918 param_<EM>event</EM>, which varies in content with each event.  The
 919 function name for each event will be <B>plugin_<EM>event</EM></B>,
 920 so for the event <EM>timer</EM>, the function declaration should look like:
 921 <PRE>
 922 int plugin_timer(struct param_timer *data);
 923 </PRE>
 924
 925 A list of the available events follows, with a list of all the fields in the
 926 supplied structure:
 927 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 928 <TABLE CELLSPACING=1 CELLPADDING=3>
 929         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 930         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 931                 <TD>This is called after a RADIUS response has been
 932                 received, but before it has been processed by the
 933                 code.  This will allow you to modify the response in
 934                 some way.
 935                 </TD>
 936                 <TD>
 937                 <DL>
 938                         <DT>t<DD>Tunnel
 939                         <DT>s<DD>Session
 940                         <DT>username
 941                         <DT>password
 942                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 943                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 944                 </DL>
 945                 </TD>
 946         </TR>
 947         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 948                 <TD>This is called after a RADIUS response has been
 949                 received, and the basic checks have been performed.  This
 950                 is what the garden module uses to force authentication
 951                 to be accepted.
 952                 </TD>
 953                 <TD>
 954                 <DL>
 955                         <DT>t<DD>Tunnel
 956                         <DT>s<DD>Session
 957                         <DT>username
 958                         <DT>auth_allowed<DD>This is already set to true or
 959                         false depending on whether authentication has been
 960                         allowed so far.  You can set this to 1 or 0 to force
 961                         allow or disallow authentication
 962                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 963                 </DL>
 964                 </TD>
 965         </TR>
 966         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 967                 <TD>This is called whenever a session receives a
 968                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 969                 seriously slow down the system.</FONT>
 970                 </TD>
 971                 <TD>
 972                 <DL>
 973                         <DT>t<DD>Tunnel
 974                         <DT>s<DD>Session
 975                         <DT>buf<DD>The raw packet data
 976                         <DT>len<DD>The length of buf
 977                 </DL>
 978                 </TD>
 979         </TR>
 980         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 981                 <TD>This is called whenever a session sends 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>timer</B></TD>
 995                 <TD>This is run every second, no matter what is happening.
 996                 This is called from a signal handler, so make sure anything
 997                 you do is reentrant.
 998                 </TD>
 999                 <TD>
1000                 <DL>
1001                         <DT>time_now<DD>The current unix timestamp
1002                 </DL>
1003                 </TD>
1004         </TR>
1005         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
1006                 <TD>This is called after a session is fully set up.  The
1007                 session is now ready to handle traffic.
1008                 </TD>
1009                 <TD>
1010                 <DL>
1011                         <DT>t<DD>Tunnel
1012                         <DT>s<DD>Session
1013                 </DL>
1014                 </TD>
1015         </TR>
1016         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
1017                 <TD>This is called when a session is about to be shut down.
1018                 This may be called multiple times for the same session.
1019                 </TD>
1020                 <TD>
1021                 <DL>
1022                         <DT>t<DD>Tunnel
1023                         <DT>s<DD>Session
1024                 </DL>
1025                 </TD>
1026         </TR>
1027         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
1028                 <TD>This is called whenever a RADIUS response includes a
1029                 Cisco-Avpair value.  The value is split up into
1030                 <EM>key=value</EM> pairs, and each is processed through all
1031                 modules.
1032                 </TD>
1033                 <TD>
1034                 <DL>
1035                         <DT>t<DD>Tunnel
1036                         <DT>s<DD>Session
1037                         <DT>key
1038                         <DT>value
1039                 </DL>
1040                 </TD>
1041         </TR>
1042         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
1043                 <TD>This is called whenever a RADIUS CoA request is
1044                 received to reset any options to default values before
1045                 the new values are applied.
1046                 </TD>
1047                 <TD>
1048                 <DL>
1049                         <DT>t<DD>Tunnel
1050                         <DT>s<DD>Session
1051                 </DL>
1052                 </TD>
1053         </TR>
1054         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1055                 <TD>This is called in whenever a nsctl packet is received.
1056                 This should handle the packet and form a response if
1057                 required.
1058                 </TD>
1059                 <TD>
1060                 <DL>
1061                         <DT>iam_master<DD>Cluster master status
1062                         <DT>argc<DD>The number of arguments
1063                         <DT>argv<DD>Arguments
1064                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1065                         <DT>additional<DD>Extended response text
1066                 </DL>
1067                 </TD>
1068         </TR>
1069 </TABLE>
1070 </TD></TR></TABLE>
1071
1072 <H2 ID="WalledGarden">Walled Garden</H2>
1073
1074 Walled Garden is implemented so that you can provide perhaps limited service
1075 to sessions that incorrectly authenticate.<P>
1076
1077 Whenever a session provides incorrect authentication, and the
1078 RADIUS server responds with Auth-Reject, the walled garden module
1079 (if loaded) will force authentication to succeed, but set the flag
1080 <EM>garden</EM> in the session structure, and adds an iptables rule to
1081 the <B>garden_users</B> chain to force all packets for the session's IP
1082 address to traverse the <B>garden</B> chain.<P>
1083
1084 This doesn't <EM>just work</EM>.  To set this all up, you will to
1085 setup the <B>garden</B> nat table with the
1086 <A HREF="#build-garden">build-garden</A> script with rules to limit
1087 user's traffic.  For example, to force all traffic except DNS to be
1088 forwarded to 192.168.1.1, add these entries to your
1089 <EM>build-garden</EM>:
1090 <PRE>
1091 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1092 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1093 </PRE>
1094
1095 l2tpns will add entries to the garden_users chain as appropriate.<P>
1096
1097 You can check the amount of traffic being captured using the following
1098 command:
1099 <PRE>
1100 iptables -t nat -L garden -nvx
1101 </PRE>
1102
1103 <H2 ID="Filtering">Filtering</H2>
1104
1105 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1106 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1107 access-list <I>filter</I> should be applied to traffic from the
1108 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1109 customer.
1110
1111 <H2 ID="Clustering">Clustering</H2>
1112
1113 An l2tpns cluster consists of of one* or more servers configured with
1114 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1115
1116 *A stand-alone server is simply a degraded cluster.<P>
1117
1118 Initially servers come up as cluster slaves, and periodically (every
1119 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1120 containing the start time of the process to the multicast
1121 <B>cluster_address</B>.<P>
1122
1123 A cluster master sends heartbeat rather than ping packets, which
1124 contain those session and tunnel changes since the last heartbeat.<P>
1125
1126 When a slave has not seen a heartbeat within
1127 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1128 examining the list of peers it has seen pings from and determines
1129 which of these and itself is the "best" candidate to be master.
1130 "Best" in this context means the server with the highest uptime (the
1131 highest IP address is used as a tie-breaker in the case of equal
1132 uptimes).<P>
1133
1134 After discovering a master, and determining that it is up-to-date (has
1135 seen an update for all in-use sessions and tunnels from heartbeat
1136 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1137 the <B>bind_address</B> and for all addresses/networks in
1138 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1139 the session state, as well as packets for throttled or gardened
1140 sessions are forwarded to the master for handling.  In addition, byte
1141 counters for session traffic are periodically forwarded.<P>
1142
1143 A master, when determining that it has at least one up-to-date slave
1144 will drop all routes (raising them again if all slaves disappear) and
1145 subsequently handle only packets forwarded to it by the slaves.<P>
1146
1147 <H2 ID="Routing">Routing</H2>
1148 If you are running a single instance, you may simply statically route
1149 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1150 arp).<P>
1151
1152 For a cluster, configure the members as BGP neighbours on your router
1153 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1154 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1155 can use "maximum-paths" (which works for EBGP) and set
1156 <B>as_number</B> to a private value such as 64512.<P>
1157
1158 <H2 ID="Performance">Performance</H2>
1159
1160 Performance is great.<P>
1161
1162 I'd like to include some pretty graphs here that show a linear performance
1163 increase, with no impact by number of connected sessions.<P>
1164
1165 That's really what it looks like.<P>
1166
1167 <BR>
1168 David Parrish<BR>
1169 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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