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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>ppp_keepalive</B> (int)<BR>
 382 Change this value to no to force generation of LCP ECHO every
 383 echo_timeout seconds, even there are activity on the link.
 384 (default: yes)
 385 </LI>
 386
 387 <LI><B>auth_tunnel_change_addr_src</B> (boolean)<BR>
 388 This parameter authorize to change the source IP of the tunnels l2tp.
 389 This parameter can be used when the remotes BAS/LAC are l2tpns server
 390 configured in cluster mode, but that the interface to remote LNS are
 391 not clustered (the tunnel can be coming from different source IP)
 392 (default: no).
 393 </LI>
 394
 395 <LI><B>disable_sending_hello</B> (boolean)<BR>
 396 Disable l2tp sending HELLO message for Apple compatibility.
 397 Some OS X implementation of l2tp no manage the L2TP "HELLO message".
 398 (default: no).
 399 </LI>
 400
 401 </UL>
 402
 403 <P><U><B>LAC configuration</B></U></P>
 404 <UL>
 405 <LI><B>bind_address_remotelns</B> (ip address)<BR>
 406 Address of the interface to listen the remote LNS tunnels.
 407 If no address is given, all interfaces are listened (Any Address).
 408 </LI>
 409
 410 <LI><B>bind_portremotelns</B> (short)<BR>
 411 Port to bind for the Remote LNS (default: 65432).
 412 </LI>
 413
 414 </UL>
 415
 416 <P>A static REMOTES LNS configuration can be entered by the command:</P>
 417 <DL> <DD><B>setforward</B> <I>MASK</I> <I>IP</I> <I>PORT</I> <I>SECRET</I> </DL>
 418
 419 where <I>MASK</I> specifies the mask of users who have forwarded to
 420 remote LNS (ex: "/friendISP@company.com").</BR>
 421 where <I>IP</I> specifies the IP of the  remote LNS (ex: "66.66.66.55").</BR>
 422 where <I>PORT</I> specifies the L2TP Port of the remote LNS
 423 (Normally should be 1701) (ex: 1701).</BR>
 424 where <I>SECRET</I> specifies the secret password the remote LNS (ex: mysecret).</BR>
 425 </BR>
 426 The static Remote LNS configuration can be used when the friend ISP not
 427 have a proxied Radius.</BR>
 428 If the proxied Radius is used, It will return the RADIUS attributes:</BR>
 429        Tunnel-Type: 1 = L2TP</BR>
 430        Tunnel-Medium-Type: 1 = IPv4</BR>
 431        Tunnel-Password: 1 = "LESECRETL2TP"</BR>
 432        Tunnel-Server-Endpoint: 1 = "88.xx.xx.x1"</BR>
 433        Tunnel-Assignment-Id: 1 = "friendisp_lns1"</BR>
 434        Tunnel-Type: 2 = L2TP</BR>
 435        Tunnel-Medium-Type: 2 = IPv4</BR>
 436        Tunnel-Password: 2 = "LESECRETL2TP"</BR>
 437        Tunnel-Server-Endpoint: 2 = "88.xx.xx.x2"</BR>
 438        Tunnel-Assignment-Id: 2 = "friendisp_lns2"</BR>
 439
 440 <P><U><B>PPPOE configuration</B></U></P>
 441
 442 <UL>
 443 <LI><B>pppoe_if_to_bind</B> (string)<BR>
 444 PPPOE server interface to bind (ex: "eth0.12"), If not specified the server PPPOE is not enabled.
 445 For the pppoe clustering, all the interfaces PPPOE of the clusters must use the same HW address (MAC address).
 446 </LI>
 447
 448 <LI><B>pppoe_service_name</B> (string)<BR>
 449 PPPOE service name (default: NULL).
 450 </LI>
 451
 452 <LI><B>pppoe_ac_name</B> (string)<BR>
 453 PPPOE  access concentrator name (default: "l2tpns-pppoe").
 454 </LI>
 455
 456 <LI><B>pppoe_only_equal_svc_name</B> (boolean)<BR>
 457 If set to yes, the PPPOE server only accepts clients with a "service-name"
 458 different from NULL and a "service-name" equal to server "service-name" (default: no).
 459 </LI>
 460
 461 </UL>
 462
 463 <P><U><B>BGP configuration</B></U></P>
 464
 465 <P>BGP routing configuration is entered by the command:
 466 The routing configuration section is entered by the command
 467 <DL><DD><B>router bgp</B> <I>as</I></DL>
 468 where <I>as</I> specifies the local AS number.
 469
 470 <P>Subsequent lines prefixed with
 471 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 472 define the attributes of BGP neighhbours.  Valid commands are:
 473 <DL>
 474   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 475   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 476 </DL>
 477
 478 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 479 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 480 <I>hold</I> are the timer values in seconds.
 481
 482 <P>Named access-lists are configured using one of the commands:
 483 <DL>
 484   <DD><B>ip access-list standard</B> <I>name</I>
 485   <DD><B>ip access-list extended</B> <I>name</I>
 486 </DL>
 487
 488 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 489 define the body of the access-list.  Standard access-list syntax:
 490 <DL>
 491   <DD>{<B>permit</B>|<B>deny</B>}
 492     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 493     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 494 </DL>
 495
 496 Extended access-lists:
 497
 498 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 499   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 500     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 501     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 502   <P>{<B>permit</B>|<B>deny</B>} <B>udp</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>fragments</B>]
 508   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 509     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 510         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 511     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 512         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 513         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 514             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 515             ...|<B>fragments</B>]
 516 </DIV>
 517
 518 <H3 ID="users">users</H3>
 519
 520 Usernames and passwords for the command-line interface are stored in
 521 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 522 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 523 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 524 plain text by the prefix <B>{crypt}</B>.<P>
 525
 526 The username <B>enable</B> has a special meaning and is used to set
 527 the enable password.<P>
 528
 529 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 530 port 23 will be allowed access without a username / password.<P>
 531
 532 <H3 ID="ip-pool">ip_pool</H3>
 533
 534 This file is used to configure the IP address pool which user
 535 addresses are assigned from.  This file should contain either an IP
 536 address or a CIDR network per line.  e.g.:<P>
 537
 538 <PRE>
 539     192.168.1.1
 540     192.168.1.2
 541     192.168.1.3
 542     192.168.4.0/24
 543     172.16.0.0/16
 544     10.0.0.0/8
 545 </PRE>
 546
 547 Keep in mind that l2tpns can only handle 65535 connections per
 548 process, so don't put more than 65535 IP addresses in the
 549 configuration file.  They will be wasted.
 550
 551 <H3 ID="build-garden">build-garden</H3>
 552
 553 The garden plugin on startup creates a NAT table called "garden" then
 554 sources the <B>build-garden</B> script to populate that table.  All
 555 packets from gardened users will be sent through this table.  Example:
 556
 557 <PRE>
 558     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 559     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 560     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 561     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 562     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 563     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 564     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 565     iptables -t nat -A garden -p icmp -j ACCEPT
 566     iptables -t nat -A garden -j DROP
 567 </PRE>
 568
 569 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 570
 571 A running l2tpns process can be controlled in a number of ways.  The primary
 572 method of control is by the Command-Line Interface (CLI).<P>
 573
 574 You can also remotely send commands to modules via the nsctl client
 575 provided.<P>
 576
 577 Also, there are a number of signals that l2tpns understands and takes action
 578 when it receives them.
 579
 580 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 581
 582 You can access the command line interface by telnet'ing to port 23.
 583 There is no IP address restriction, so it's a good idea to firewall
 584 this port off from anyone who doesn't need access to it.  See
 585 <A HREF="#users">users</A> for information on restricting access based
 586 on a username and password.<P>
 587
 588 The CLI gives you real-time control over almost everything in
 589 the process.  The interface is designed to look like a Cisco
 590 device, and supports things like command history, line editing and
 591 context sensitive help.  This is provided by linking with the
 592 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 593 library.  Some general documentation of the interface is
 594 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 595 here</A>.<P>
 596
 597 After you have connected to the telnet port (and perhaps logged in), you
 598 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 599
 600 Enter <EM>help</EM> to get a list of possible commands.  A brief
 601 overview of the more important commands follows:
 602
 603 <UL>
 604 <LI><B>show session</B><BR>
 605 Without specifying a session ID, this will list all tunnels currently
 606 connected.  If you specify a session ID, you will be given all
 607 information on a single tunnel.  Note that the full session list can
 608 be around 185 columns wide, so you should probably use a wide terminal
 609 to see the list properly.<P>
 610 The columns listed in the overview are:
 611 <TABLE>
 612         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 613         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 614         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 615         authentication.  If this is *, then LCP authentication has not
 616         completed.</TD></TR>
 617         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 618         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 619         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 620         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 621         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 622         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 623         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 624         trapped in the walled garden.  This field is present even if the
 625         garden module is not loaded.</TD></TR>
 626         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 627         session started</TD></TR>
 628         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 629         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 630         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 631         detected on the session</TD></TR>
 632         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 633         connected to.</TD></TR>
 634         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 635         provided during the session setup.  This field is generated by the
 636         LAC.</TD></TR>
 637 </TABLE>
 638 <P>
 639 </LI>
 640
 641 <LI><B>show users</B><BR>
 642 With no arguments, display a list of currently connected users.  If an
 643 argument is given, the session details for the given username are
 644 displayed.
 645 </LI>
 646
 647 <LI><B>show tunnel</B><BR>
 648 This will show all the open tunnels in a summary, or detail on a single
 649 tunnel if you give a tunnel id.<P>
 650 The columns listed in the overview are:
 651 <TABLE>
 652         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 653         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 654         provided by the LAC.  This has no relation to DNS, it is just
 655         a text field.</TD></TR>
 656         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 657         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 658         Opening</TD></TR>
 659         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 660         tunnel</TD></TR>
 661 </TABLE>
 662 <P>
 663 </LI>
 664
 665 <LI><B>show pool</B><BR>
 666 Displays the current IP address pool allocation.  This will only display
 667 addresses that are in use, or are reserved for re-allocation to a
 668 disconnected user.<P>
 669 If an address is not currently in use, but has been used, then in the User
 670 column the username will be shown in square brackets, followed by the time
 671 since the address was used:
 672 <PRE>
 673 IP Address      Used  Session User
 674 192.168.100.6     N           [joe.user] 1548s
 675 </PRE>
 676 <P>
 677 </LI>
 678
 679 <LI><B>show radius</B><BR>
 680 Show a summary of the in-use RADIUS sessions.  This list should not be very
 681 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 682 columns listed are:
 683 <TABLE>
 684         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 685         sent in the packet to the RADIUS server for identification.</TD></TR>
 686         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 687         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 688         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 689         request is associated with</TD></TR>
 690         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 691         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 692         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 693         discarded after 3 retries.</TD></TR>
 694 </TABLE>
 695 <P>
 696 </LI>
 697
 698 <LI><B>show running-config</B><BR>
 699 This will list the current running configuration.  This is in a format that
 700 can either be pasted into the configuration file, or run directly at the
 701 command line.
 702 <P>
 703 </LI>
 704
 705 <LI><B>show counters</B><BR>
 706 Internally, counters are kept of key values, such as bytes and packets
 707 transferred, as well as function call counters.  This function displays all
 708 these counters, and is probably only useful for debugging.<P>
 709 You can reset these counters by running <EM>clear counters</EM>.
 710 <P>
 711 </LI>
 712
 713 <LI><B>show cluster</B><BR>
 714 Show cluster status.  Shows the cluster state for this server
 715 (Master/Slave), information about known peers and (for slaves) the
 716 master IP address, last packet seen and up-to-date status.<P>
 717 See <A HREF="#Clustering">Clustering</A> for more information.
 718 <P>
 719 </LI>
 720
 721 <LI><B>write memory</B><BR>
 722 This will write the current running configuration to the config file
 723 <B>startup-config</B>, which will be run on a restart.
 724 <P>
 725 </LI>
 726
 727 <LI><B>snoop</B><BR>
 728 You must specify a username, IP address and port.  All packets for the
 729 current session for that username will be forwarded to the given
 730 host/port.  Specify <EM>no snoop username</EM> to disable interception
 731 for the session.<P>
 732
 733 If you want interception to be permanent, you will have to modify the RADIUS
 734 response for the user.  See <A HREF="#Interception">Interception</A>.
 735 <P>
 736 </LI>
 737
 738 <LI><B>throttle</B><BR>
 739 You must specify a username, which will be throttled for the current
 740 session.  Specify <EM>no throttle username</EM> to disable throttling
 741 for the current session.<P>
 742
 743 If you want throttling to be permanent, you will have to modify the
 744 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 745 <P>
 746 </LI>
 747
 748 <LI><B>drop session</B><BR>
 749 This will cleanly disconnect a session.  You must specify a session id, which
 750 you can get from <EM>show session</EM>.  This will send a disconnect message
 751 to the remote end.
 752 <P>
 753 </LI>
 754
 755 <LI><B>drop tunnel</B><BR>
 756 This will cleanly disconnect a tunnel, as well as all sessions on that
 757 tunnel.  It will send a disconnect message for each session individually, and
 758 after 10 seconds it will send a tunnel disconnect message.
 759 <P>
 760 </LI>
 761
 762 <LI><B>uptime</B><BR>
 763 This will show how long the l2tpns process has been running, and the current
 764 bandwidth utilization:
 765 <PRE>
 766 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 767 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 768 </PRE>
 769 The bandwidth line contains 4 sets of values.<BR>
 770 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 771 (user uploads), in mbits/sec.<BR>
 772 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 773 downloads).<BR>
 774 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 775 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 776 <P>
 777 These counters are updated every second.
 778 <P>
 779 </LI>
 780
 781 <LI><B>configure terminal</B><BR>
 782 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 783 The following commands are valid in this mode:<P>
 784 </LI>
 785
 786 <LI><B>load plugin</B><BR>
 787 Load a plugin.  You must specify the plugin name, and it will search in
 788 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 789 <EM>remove plugin</EM>.
 790 <P>
 791 </LI>
 792
 793 <LI><B>set</B><BR>
 794 Set a configuration variable.  You must specify the variable name, and
 795 the value.  If the value contains any spaces, you should quote the
 796 value with double (") or single (') quotes.<P>
 797
 798 You can set any <A HREF="#startup-config">startup-config</A> value in
 799 this way, although some may require a restart to take effect.<P>
 800 </LI>
 801 </UL>
 802
 803 <H3 ID="nsctl">nsctl</H3>
 804
 805 nsctl allows messages to be passed to plugins.<P>
 806
 807 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 808 <STRONG>nsctl</STRONG>(8) for more details.<P>
 809
 810 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 811 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 812
 813 <H3 ID="Signals">Signals</H3>
 814
 815 While the process is running, you can send it a few different signals, using
 816 the kill command.
 817 <PRE>
 818 killall -HUP l2tpns
 819 </PRE>
 820
 821 The signals understood are:
 822 <DL>
 823 <DT>SIGHUP</DT><DD>Reload the config from disk and re-open log file.</DD>
 824 <DT>SIGTERM, SIGINT</DT><DD>Stop process.  Tunnels and sessions are not
 825 terminated.  This signal should be used to stop l2tpns on a
 826 <A HREF="#Clustering">cluster node</A> where there are other machines to
 827 continue handling traffic.</DD>
 828 <DT>SIGQUIT</DT><DD>Shut down tunnels and sessions, exit process when
 829 complete.</DD>
 830 </DL>
 831
 832 <H2 ID="Throttling">Throttling</H2>
 833
 834 l2tpns contains support for slowing down user sessions to whatever speed you
 835 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 836 before this will be activated.<P>
 837
 838 If you wish a session to be throttled permanently, you should set the
 839 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 840 will be handled by the <EM>autothrottle</EM> module.<P>
 841
 842 Otherwise, you can enable and disable throttling an active session using
 843 the <EM>throttle</EM> CLI command.<P>
 844
 845 <H2 ID="Interception">Interception</H2>
 846
 847 You may have to deal with legal requirements to be able to intercept a
 848 user's traffic at any time.  l2tpns allows you to begin and end interception
 849 on the fly, as well as at authentication time.<P>
 850
 851 When a user is being intercepted, a copy of every packet they send and
 852 receive will be sent wrapped in a UDP packet to the IP address and port set
 853 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 854 variables.<P>
 855
 856 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 857
 858 To enable interception on a connected user, use the <EM>snoop username</EM>
 859 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 860 immediately.<P>
 861
 862 If you wish the user to be intercepted whenever they reconnect, you will
 863 need to modify the RADIUS response to include the Vendor-Specific value
 864 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 865 you need to have the <EM>autosnoop</EM> module loaded.<P>
 866
 867 <H2 ID="Authentication">Authentication</H2>
 868
 869 Whenever a session connects, it is not fully set up until authentication is
 870 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 871 request to l2tpns.<P>
 872
 873 This request is sent to the RADIUS server, which will hopefully respond with
 874 Auth-Accept or Auth-Reject.<P>
 875
 876 If Auth-Accept is received, the session is set up and an IP address is
 877 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 878 reply, and that address will be assigned to the client.  It can also include
 879 specific DNS servers, and a Framed-Route if that is required.<P>
 880
 881 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 882 at which point they should disconnect.  The exception to this is when the
 883 walled garden module is loaded, in which case the user still receives the
 884 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 885 should not receive any service.<P>
 886
 887 The RADIUS reply can also contain a Vendor-Specific attribute called
 888 Cisco-Avpair.  This field is a freeform text field that most Cisco
 889 devices understand to contain configuration instructions for the session.  In
 890 the case of l2tpns it is expected to be of the form
 891 <PRE>
 892 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 893 </PRE>
 894
 895 Each key-value pair is separated and passed to any modules loaded.  The
 896 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 897 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 898 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 899 contain:
 900 <PRE>
 901 intercept=yes,throttle=yes
 902 </PRE>
 903
 904 <H2 ID="Plugins">Plugins</H2>
 905
 906 So as to make l2tpns as flexible as possible (I know the core code is pretty
 907 difficult to understand), it includes a plugin API, which you can use to
 908 hook into certain events.<P>
 909
 910 There are a few example modules included - autosnoop, autothrottle and
 911 garden.<P>
 912
 913 When an event happens that has a hook, l2tpns looks for a predefined
 914 function name in every loaded module, and runs them in the order the modules
 915 were loaded.<P>
 916
 917 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 918 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 919 modules should be run for this event.<P>
 920 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 921 no further processing should be done for this event.  <EM>Use this with care.</EM>
 922
 923 Every event function called takes a specific structure named
 924 param_<EM>event</EM>, which varies in content with each event.  The
 925 function name for each event will be <B>plugin_<EM>event</EM></B>,
 926 so for the event <EM>timer</EM>, the function declaration should look like:
 927 <PRE>
 928 int plugin_timer(struct param_timer *data);
 929 </PRE>
 930
 931 A list of the available events follows, with a list of all the fields in the
 932 supplied structure:
 933 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 934 <TABLE CELLSPACING=1 CELLPADDING=3>
 935         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 936         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 937                 <TD>This is called after a RADIUS response has been
 938                 received, but before it has been processed by the
 939                 code.  This will allow you to modify the response in
 940                 some way.
 941                 </TD>
 942                 <TD>
 943                 <DL>
 944                         <DT>t<DD>Tunnel
 945                         <DT>s<DD>Session
 946                         <DT>username
 947                         <DT>password
 948                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 949                         <DT>continue_auth<DD>Set to 0 to stop processing authentication modules
 950                 </DL>
 951                 </TD>
 952         </TR>
 953         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 954                 <TD>This is called after a RADIUS response has been
 955                 received, and the basic checks have been performed.  This
 956                 is what the garden module uses to force authentication
 957                 to be accepted.
 958                 </TD>
 959                 <TD>
 960                 <DL>
 961                         <DT>t<DD>Tunnel
 962                         <DT>s<DD>Session
 963                         <DT>username
 964                         <DT>auth_allowed<DD>This is already set to true or
 965                         false depending on whether authentication has been
 966                         allowed so far.  You can set this to 1 or 0 to force
 967                         allow or disallow authentication
 968                         <DT>protocol<DD>0xC023 for PAP, 0xC223 for CHAP
 969                 </DL>
 970                 </TD>
 971         </TR>
 972         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 973                 <TD>This is called whenever a session receives a
 974                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 975                 seriously slow down the system.</FONT>
 976                 </TD>
 977                 <TD>
 978                 <DL>
 979                         <DT>t<DD>Tunnel
 980                         <DT>s<DD>Session
 981                         <DT>buf<DD>The raw packet data
 982                         <DT>len<DD>The length of buf
 983                 </DL>
 984                 </TD>
 985         </TR>
 986         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 987                 <TD>This is called whenever a session sends a
 988                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 989                 seriously slow down the system.</FONT>
 990                 </TD>
 991                 <TD>
 992                 <DL>
 993                         <DT>t<DD>Tunnel
 994                         <DT>s<DD>Session
 995                         <DT>buf<DD>The raw packet data
 996                         <DT>len<DD>The length of buf
 997                 </DL>
 998                 </TD>
 999         </TR>
1000         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
1001                 <TD>This is run every second, no matter what is happening.
1002                 This is called from a signal handler, so make sure anything
1003                 you do is reentrant.
1004                 </TD>
1005                 <TD>
1006                 <DL>
1007                         <DT>time_now<DD>The current unix timestamp
1008                 </DL>
1009                 </TD>
1010         </TR>
1011         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
1012                 <TD>This is called after a session is fully set up.  The
1013                 session is now ready to handle traffic.
1014                 </TD>
1015                 <TD>
1016                 <DL>
1017                         <DT>t<DD>Tunnel
1018                         <DT>s<DD>Session
1019                 </DL>
1020                 </TD>
1021         </TR>
1022         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
1023                 <TD>This is called when a session is about to be shut down.
1024                 This may be called multiple times for the same session.
1025                 </TD>
1026                 <TD>
1027                 <DL>
1028                         <DT>t<DD>Tunnel
1029                         <DT>s<DD>Session
1030                 </DL>
1031                 </TD>
1032         </TR>
1033         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
1034                 <TD>This is called whenever a RADIUS response includes a
1035                 Cisco-Avpair value.  The value is split up into
1036                 <EM>key=value</EM> pairs, and each is processed through all
1037                 modules.
1038                 </TD>
1039                 <TD>
1040                 <DL>
1041                         <DT>t<DD>Tunnel
1042                         <DT>s<DD>Session
1043                         <DT>key
1044                         <DT>value
1045                 </DL>
1046                 </TD>
1047         </TR>
1048         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_reset</B></TD>
1049                 <TD>This is called whenever a RADIUS CoA request is
1050                 received to reset any options to default values before
1051                 the new values are applied.
1052                 </TD>
1053                 <TD>
1054                 <DL>
1055                         <DT>t<DD>Tunnel
1056                         <DT>s<DD>Session
1057                 </DL>
1058                 </TD>
1059         </TR>
1060         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
1061                 <TD>This is called in whenever a nsctl packet is received.
1062                 This should handle the packet and form a response if
1063                 required.
1064                 </TD>
1065                 <TD>
1066                 <DL>
1067                         <DT>iam_master<DD>Cluster master status
1068                         <DT>argc<DD>The number of arguments
1069                         <DT>argv<DD>Arguments
1070                         <DT>response<DD>Return value: NSCTL_RES_OK or NSCTL_RES_ERR
1071                         <DT>additional<DD>Extended response text
1072                 </DL>
1073                 </TD>
1074         </TR>
1075 </TABLE>
1076 </TD></TR></TABLE>
1077
1078 <H2 ID="WalledGarden">Walled Garden</H2>
1079
1080 Walled Garden is implemented so that you can provide perhaps limited service
1081 to sessions that incorrectly authenticate.<P>
1082
1083 Whenever a session provides incorrect authentication, and the
1084 RADIUS server responds with Auth-Reject, the walled garden module
1085 (if loaded) will force authentication to succeed, but set the flag
1086 <EM>garden</EM> in the session structure, and adds an iptables rule to
1087 the <B>garden_users</B> chain to force all packets for the session's IP
1088 address to traverse the <B>garden</B> chain.<P>
1089
1090 This doesn't <EM>just work</EM>.  To set this all up, you will to
1091 setup the <B>garden</B> nat table with the
1092 <A HREF="#build-garden">build-garden</A> script with rules to limit
1093 user's traffic.  For example, to force all traffic except DNS to be
1094 forwarded to 192.168.1.1, add these entries to your
1095 <EM>build-garden</EM>:
1096 <PRE>
1097 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
1098 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
1099 </PRE>
1100
1101 l2tpns will add entries to the garden_users chain as appropriate.<P>
1102
1103 You can check the amount of traffic being captured using the following
1104 command:
1105 <PRE>
1106 iptables -t nat -L garden -nvx
1107 </PRE>
1108
1109 <H2 ID="Filtering">Filtering</H2>
1110
1111 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
1112 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
1113 access-list <I>filter</I> should be applied to traffic from the
1114 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
1115 customer.
1116
1117 <H2 ID="Clustering">Clustering</H2>
1118
1119 An l2tpns cluster consists of of one* or more servers configured with
1120 the same configuration, notably the multicast <B>cluster_address</B>.<P>
1121
1122 *A stand-alone server is simply a degraded cluster.<P>
1123
1124 Initially servers come up as cluster slaves, and periodically (every
1125 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
1126 containing the start time of the process to the multicast
1127 <B>cluster_address</B>.<P>
1128
1129 A cluster master sends heartbeat rather than ping packets, which
1130 contain those session and tunnel changes since the last heartbeat.<P>
1131
1132 When a slave has not seen a heartbeat within
1133 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1134 examining the list of peers it has seen pings from and determines
1135 which of these and itself is the "best" candidate to be master.
1136 "Best" in this context means the server with the highest uptime (the
1137 highest IP address is used as a tie-breaker in the case of equal
1138 uptimes).<P>
1139
1140 After discovering a master, and determining that it is up-to-date (has
1141 seen an update for all in-use sessions and tunnels from heartbeat
1142 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1143 the <B>bind_address</B> and for all addresses/networks in
1144 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1145 the session state, as well as packets for throttled or gardened
1146 sessions are forwarded to the master for handling.  In addition, byte
1147 counters for session traffic are periodically forwarded.<P>
1148
1149 A master, when determining that it has at least one up-to-date slave
1150 will drop all routes (raising them again if all slaves disappear) and
1151 subsequently handle only packets forwarded to it by the slaves.<P>
1152
1153 <H2 ID="Routing">Routing</H2>
1154 If you are running a single instance, you may simply statically route
1155 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1156 arp).<P>
1157
1158 For a cluster, configure the members as BGP neighbours on your router
1159 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1160 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1161 can use "maximum-paths" (which works for EBGP) and set
1162 <B>as_number</B> to a private value such as 64512.<P>
1163
1164 <H2 ID="Performance">Performance</H2>
1165
1166 Performance is great.<P>
1167
1168 I'd like to include some pretty graphs here that show a linear performance
1169 increase, with no impact by number of connected sessions.<P>
1170
1171 That's really what it looks like.<P>
1172
1173 <BR>
1174 David Parrish<BR>
1175 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1176 </BODY>
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