Docs/manual.html

   1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
   2     "http://www.w3.org/TR/html4/loose.dtd">
   3
   4 <HTML>
   5 <HEAD>
   6 <TITLE>L2TPNS Manual</TITLE>
   7 <STYLE TYPE="text/css">
   8 H1 {
   9         text-align: center;
  10 }
  11
  12 H2 {
  13         border-top: 1px solid black;
  14         border-bottom: 1px solid black;
  15         background-color: lightblue;
  16         padding-left: 10px;
  17 }
  18
  19 H3 {
  20         text-decoration: underline;
  21 }
  22 </STYLE>
  23 </HEAD>
  24 <BODY>
  25 <H1>L2TPNS Manual</H1>
  26 <OL>
  27     <LI><A HREF="#Overview">Overview</A></LI>
  28     <LI><A HREF="#Installation">Installation</A>
  29         <OL>
  30             <LI><A HREF="#Requirements">Requirements</A></LI>
  31             <LI><A HREF="#Compile">Compile</A></LI>
  32             <LI><A HREF="#Install">Install</A></LI>
  33             <LI><A HREF="#Running">Running</A></LI>
  34         </OL>
  35     </LI>
  36     <LI><A HREF="#Configuration">Configuration</A>
  37         <OL>
  38             <LI><A HREF="#startup-config">startup-config</A></LI>
  39             <LI><A HREF="#users">users</A></LI>
  40             <LI><A HREF="#ip-pool">ip_pool</A></LI>
  41             <LI><A HREF="#build-garden">build-garden</A></LI>
  42         </OL>
  43     </LI>
  44     <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
  45         <OL>
  46             <LI><A HREF="#Command-LineInterface">Command-Line Interface</A></LI>
  47             <LI><A HREF="#nsctl">nsctl</A></LI>
  48             <LI><A HREF="#Signals">Signals</A></LI>
  49         </OL>
  50     </LI>
  51     <LI><A HREF="#Throttling">Throttling</A></LI>
  52     <LI><A HREF="#Interception">Interception</A></LI>
  53     <LI><A HREF="#Authentication">Authentication</A></LI>
  54     <LI><A HREF="#Plugins">Plugins</A></LI>
  55     <LI><A HREF="#Walled Garden">Walled Garden</A></LI>
  56     <LI><A HREF="#Clustering">Clustering</A></LI>
  57     <LI><A HREF="#Routing">Routing</A></LI>
  58     <LI><A HREF="#Performance">Performance</A></LI>
  59 </OL>
  60
  61 <H2 ID="Overview">Overview</H2>
  62 l2tpns is half of a complete L2TP implementation.  It supports only the
  63 LNS side of the connection.<P>
  64
  65 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
  66 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection.  l2tpns
  67 implements PPP over L2TP only.<P>
  68
  69 There are a couple of other L2TP imlementations, of which <A
  70 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
  71 most popular.  l2tpd also will handle being either end of a tunnel, and
  72 is a lot more configurable than l2tpns.  However, due to the way it works,
  73 it is nowhere near as scalable.<P>
  74
  75 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
  76 and send packets.  Using some packet manipulation it doesn't require a
  77 single interface per connection, as l2tpd does.<P>
  78
  79 This allows it to scale extremely well to very high loads and very high
  80 numbers of connections.<P>
  81
  82 It also has a plugin architecture which allows custom code to be run
  83 during processing.  An example of this is in the walled garden module
  84 included.<P>
  85
  86 <BR>
  87 <EM>Documentation is not my best skill.  If you find any problems
  88 with this document, or if you wish to contribute, please email <A
  89 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
  90
  91 <H2 ID="Installation">Installation</H2>
  92 <H3 ID="Requirements">Requirements</H3>
  93
  94 <OL>
  95 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
  96 compiled in, or as a module.</LI>
  97
  98 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
  99 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
 100 </OL>
 101
 102 <H3 ID="Compile">Compile</H3>
 103
 104 You can generally get away with just running <B>make</B> from the source
 105 directory.  This will compile the daemon, associated tools and any modules
 106 shipped with the distribution.<P>
 107
 108 <H3 ID="Install">Install</H3>
 109
 110 After you have successfully compiled everything, run <B>make
 111 install</B> to install it.  By default, the binaries are installed into
 112 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
 113 modules into <EM>/usr/lib/l2tpns</EM>.<P>
 114
 115 You will definately need to edit the configuration files before you
 116 start.  See the <A HREF="#Configuration">Configuration</A> section for
 117 more information.<P>
 118
 119 <H3 ID="Running">Running</H3>
 120
 121 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it.  It does
 122 not detach to a daemon process, so you should perhaps run it from init.<P>
 123
 124 By default there is no log destination set, so all log messages will go to
 125 stdout.<P>
 126
 127 <H2 ID="Configuration">Configuration</H2>
 128
 129 All configuration of the software is done from the files installed into
 130 /etc/l2tpns.
 131
 132 <H3 ID="startup-config">startup-config</H3>
 133
 134 This is the main configuration file for l2tpns.  The format of the file is a
 135 list of commands that can be run through the command-line interface.  This
 136 file can also be written directly by the l2tpns process if a user runs the
 137 <EM>write memory</EM> command, so any comments will be lost.  However if your
 138 policy is not to write the config by the program, then feel free to comment
 139 the file with a # or ! at the beginning of the line.<P>
 140
 141 A list of the possible configuration directives follows.  Each of these
 142 should be set by a line like:<P>
 143 <PRE>
 144 set configstring "value"
 145 set ipaddress 192.168.1.1
 146 set boolean true
 147 </PRE>
 148
 149 <UL>
 150 <LI><B>debug</B> (int)<BR>
 151 Sets the level of messages that will be written to the log file.  The value
 152 should be between 0 and 5, with 0 being no debugging, and 5 being the
 153 highest.  A rough description of the levels is:
 154         <OL>
 155         <LI VALUE=0>Critical Errors - Things are probably broken</LI>
 156         <LI>Errors - Things might have gone wrong, but probably will recover</LI>
 157         <LI>Warnings - Just in case you care what is not quite perfect</LI>
 158         <LI>Information - Parameters of control packets</LI>
 159         <LI>Calls - For tracing the execution of the code</LI>
 160         <LI>Packets - Everything, including a hex dump of all packets processed...  probably twice</LI>
 161         </OL><P>
 162 Note that the higher you set the debugging level, the slower the program
 163 will run.  Also, at level 5 a LOT of information will be logged.  This should
 164 only ever be used for working out why it doesn't work at all.
 165 <P>
 166 </LI>
 167
 168 <LI><B>log_file</B> (string)<BR>
 169 This will be where all logging and debugging information is written
 170 to.  This can be either a filename, such as <EM>/var/log/l2tpns</EM>, or
 171 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
 172 is any one of the syslog logging facilities, such as local5.
 173 <P>
 174 </LI>
 175
 176 <LI><B>pid_file</B> (string)<BR>
 177 If this is set, the process id will be written to this file. The filename must
 178 contain an absolute path.
 179 <P>
 180 </LI>
 181
 182 <LI><B>l2tp_secret</B> (string)<BR>
 183 This sets the string that l2tpns will use for authenticating tunnel request.
 184 This must be the same as the LAC, or authentication will fail.  This will
 185 only actually be used if the LAC requests authentication.
 186 <P>
 187 </LI>
 188
 189 <LI><B>primary_dns</B> (ip address)
 190 <LI><B>secondary_dns</B> (ip address)<BR>
 191 Whenever a PPP connection is established, DNS servers will be sent to the
 192 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 193 one will not be sent.
 194 <P>
 195 </LI>
 196
 197 <LI><B>save_state</B> (boolean)<BR>
 198 When l2tpns receives a STGTERM it will write out its current
 199 ip_address_pool, session and tunnel tables to disk prior to exiting to
 200 be re-loaded at startup.  The validity of this data is obviously quite
 201 short and the intent is to allow an sessions to be retained over a
 202 software upgrade.
 203 <P>
 204 </LI>
 205
 206 <LI><B>primary_radius</B> (ip address)
 207 <LI><B>secondary_radius</B> (ip address)<BR>
 208 This sets the radius servers used for both authentication and
 209 accounting.  If the primary server does not respond, then the
 210 secondary radius server will be tried.
 211 <P>
 212 </LI>
 213
 214 <LI><B>primary_radius_port</B> (short)
 215 <LI><B>secondary_radius_port</B> (short)<BR>
 216 This sets the authentication ports for the primary and secondary
 217 radius servers.  The accounting port is one more than the authentication
 218 port.  If no radius ports are given, the authentication port defaults to 1645,
 219 and the accounting port to 1646.
 220 <P>
 221 </LI>
 222
 223 <LI><B>radius_accounting</B> (boolean)<BR>
 224 If set to true, then radius accounting packets will be sent.  This
 225 means that a Start record will be sent when the session is
 226 successfully authenticated, and a Stop record will be sent when the
 227 session is closed.
 228 <P>
 229 </LI>
 230
 231 <LI><B>radius_secret</B> (string)<BR>
 232 This secret will be used in all radius queries.  If this is not set then
 233 radius queries will fail.
 234 <P>
 235 </LI>
 236
 237 <LI><B>bind_address</B> (ip address)<BR>
 238 When the tun interface is created, it is assigned the address
 239 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 240 containing user traffic should be routed via this address if given,
 241 otherwise the primary address of the machine.
 242 <P>
 243 </LI>
 244
 245 <LI><B>send_garp</B> (boolean)<BR>
 246 Determines whether or not to send a gratuitous ARP for the
 247 bind_address when the server is ready to handle traffic (default:
 248 true).<BR>
 249 This value is ignored if BGP is configured.
 250 <P>
 251 </LI>
 252
 253 <LI><B>throttle_speed</B> (int)<BR>
 254 Sets the speed (in kbits/s) which sessions will be limited to.  If this is
 255 set to 0, then throttling will not be used at all.  Note: You can set this by
 256 the CLI, but changes will not affect currently connected users.
 257 <P>
 258 </LI>
 259
 260 <LI><B>accounting_dir</B> (string)<BR>
 261 If set to a directory, then every 5 minutes the current usage for
 262 every connected use will be dumped to a file in this directory.  Each
 263 file dumped begins with a header, where each line is prefixed by #.
 264 Following the header is a single line for every connected user, fields
 265 separated by a space.<BR> The fields are username, ip, qos,
 266 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 267 2 if the user is throttled.
 268 <P>
 269 </LI>
 270
 271 <LI><B>setuid</B> (int)<BR>
 272 After starting up and binding the interface, change UID to this.  This
 273 doesn't work properly.
 274 <P>
 275 </LI>
 276
 277 <LI><B>dump_speed</B> (boolean)<BR>
 278 If set to true, then the current bandwidth utilization will be logged every
 279 second.  Even if this is disabled, you can see this information by running
 280 the <EM>uptime</EM> command on the CLI.
 281 <P>
 282 </LI>
 283
 284 <LI><B>cleanup_interval</B> (int)<BR>
 285 Interval between regular cleanups (in seconds).
 286 <P>
 287 </LI>
 288
 289 <LI><B>multi_read_count</B> (int)<BR>
 290 Number of packets to read off each of the UDP and TUN fds when
 291 returned as readable by select (default:  10).  Avoids incurring the
 292 unnecessary system call overhead of select on busy servers.
 293 <P>
 294 </LI>
 295
 296 <LI><B>scheduler_fifo</B> (boolean)<BR>
 297 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 298 causes the kernel to immediately preempt any currently SCHED_OTHER
 299 (normal) process in favour of l2tpns when it becomes runnable.
 300 Ignored on uniprocessor systems.
 301 <P>
 302 </LI>
 303
 304 <LI><B>lock_pages</B> (boolean)<BR>
 305 Keep all pages mapped by the l2tpns process in memory.
 306 <P>
 307 </LI>
 308
 309 <LI><B>icmp_rate</B> (int)<BR>
 310 Maximum number of host unreachable icmp packets to send per second.
 311 <P>
 312 </LI>
 313
 314 <LI><B>cluster_address</B> (ip address)<BR>
 315 Multicast cluster address (default:  239.192.13.13).  See the section
 316 on <A HREF="#Clustering">Clustering</A> for more information.
 317 <P>
 318 </LI>
 319
 320 <LI><B>cluster_interface</B> (string)<BR>
 321 Interface for cluster packets (default: eth0).
 322 <P>
 323 </LI>
 324
 325 <LI><B>cluster_hb_interval</B> (int)<BR>
 326 Interval in tenths of a second between cluster heartbeat/pings.
 327 <P>
 328 </LI>
 329
 330 <LI><B>cluster_hb_timeout</B> (int)<BR>
 331 Cluster heartbeat timeout in tenths of a second.  A new master will be
 332 elected when this interval has been passed without seeing a heartbeat
 333 from the master.
 334 <P>
 335 </LI>
 336
 337 <LI><B>as_number</B> (int)<BR>
 338 Defines the local AS number for BGP (see <A HREF="#Routing">Routing</A>).
 339 <P>
 340 </LI>
 341
 342 <LI><B>bgp_peer1</B> (string)
 343 <LI><B>bgp_peer1_as</B> (int)
 344 <LI><B>bgp_peer2</B> (string)
 345 <LI><B>bgp_peer2_as</B> (int)<BR>
 346 <P>
 347 DNS name (or IP) and AS number of BGP peers.
 348 </LI>
 349 </UL>
 350
 351 <H3 ID="users">users</H3>
 352
 353 Usernames and passwords for the command-line interface are stored in
 354 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 355 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 356 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 357 plain text by the prefix <B>{crypt}</B>.<P>
 358
 359 The username <B>enable</B> has a special meaning and is used to set
 360 the enable password.<P>
 361
 362 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 363 port 23 will be allowed access without a username / password.<P>
 364
 365 <H3 ID="ip-pool">ip_pool</H3>
 366
 367 This file is used to configure the IP address pool which user
 368 addresses are assigned from.  This file should contain either an IP
 369 address or a CIDR network per line.  e.g.:<P>
 370
 371 <PRE>
 372     192.168.1.1
 373     192.168.1.2
 374     192.168.1.3
 375     192.168.4.0/24
 376     172.16.0.0/16
 377     10.0.0.0/8
 378 </PRE>
 379
 380 Keep in mind that l2tpns can only handle 65535 connections per
 381 process, so don't put more than 65535 IP addresses in the
 382 configuration file.  They will be wasted.
 383
 384 <H3 ID="build-garden">build-garden</H3>
 385
 386 The garden plugin on startup creates a NAT table called "garden" then
 387 sources the <B>build-garden</B> script to populate that table.  All
 388 packets from gardened users will be sent through this table.  Example:
 389
 390 <PRE>
 391     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 392     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 393     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 394     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 395     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 396     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 397     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 398     iptables -t nat -A garden -p icmp -j ACCEPT
 399     iptables -t nat -A garden -j DROP
 400 </PRE>
 401
 402 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 403
 404 A running l2tpns process can be controlled in a number of ways.  The primary
 405 method of control is by the Command-Line Interface (CLI).<P>
 406
 407 You can also remotely send commands to modules via the nsctl client
 408 provided.  This currently only works with the walled garden module, but
 409 modification is trivial to support other modules.<P>
 410
 411 Also, there are a number of signals that l2tpns understands and takes action
 412 when it receives them.
 413
 414 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 415
 416 You can access the command line interface by telnet'ing to port 23.
 417 There is no IP address restriction, so it's a good idea to firewall
 418 this port off from anyone who doesn't need access to it.  See
 419 <A HREF="#users">users</A> for information on restricting access based
 420 on a username and password.<P>
 421
 422 The CLI gives you real-time control over almost everything in
 423 the process.  The interface is designed to look like a Cisco
 424 device, and supports things like command history, line editing and
 425 context sensitive help.  This is provided by linking with the
 426 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 427 library.  Some general documentation of the interface is
 428 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 429 here</A>.<P>
 430
 431 After you have connected to the telnet port (and perhaps logged in), you
 432 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 433
 434 Enter <EM>help</EM> to get a list of possible commands.  A brief
 435 overview of the more important commands follows:
 436
 437 <UL>
 438 <LI><B>show session</B><BR>
 439 Without specifying a session ID, this will list all tunnels currently
 440 connected.  If you specify a session ID, you will be given all
 441 information on a single tunnel.  Note that the full session list can
 442 be around 185 columns wide, so you should probably use a wide terminal
 443 to see the list properly.<P>
 444 The columns listed in the overview are:
 445 <TABLE>
 446         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 447         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 448         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 449         authentication.  If this is *, then LCP authentication has not
 450         completed.</TD></TR>
 451         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 452         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 453         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 454         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 455         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 456         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 457         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 458         trapped in the walled garden.  This field is present even if the
 459         garden module is not loaded.</TD></TR>
 460         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 461         session started</TD></TR>
 462         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 463         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 464         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 465         detected on the session</TD></TR>
 466         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 467         connected to.</TD></TR>
 468         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 469         provided during the session setup.  This field is generated by the
 470         LAC.</TD></TR>
 471 </TABLE>
 472 <P>
 473 </LI>
 474
 475 <LI><B>show users</B><BR>
 476 With no arguments, display a list of currently connected users.  If an
 477 argument is given, the session details for the given username are
 478 displayed.
 479 </LI>
 480
 481 <LI><B>show tunnel</B><BR>
 482 This will show all the open tunnels in a summary, or detail on a single
 483 tunnel if you give a tunnel id.<P>
 484 The columns listed in the overview are:
 485 <TABLE>
 486         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 487         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 488         provided by the LAC.  This has no relation to DNS, it is just
 489         a text field.</TD></TR>
 490         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 491         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 492         Opening</TD></TR>
 493         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 494         tunnel</TD></TR>
 495 </TABLE>
 496 <P>
 497 </LI>
 498
 499 <LI><B>show pool</B><BR>
 500 Displays the current IP address pool allocation.  This will only display
 501 addresses that are in use, or are reserved for re-allocation to a
 502 disconnected user.<P>
 503 If an address is not currently in use, but has been used, then in the User
 504 column the username will be shown in square brackets, followed by the time
 505 since the address was used:
 506 <PRE>
 507 IP Address      Used  Session User
 508 192.168.100.6     N           [joe.user] 1548s
 509 </PRE>
 510 <P>
 511 </LI>
 512
 513 <LI><B>show radius</B><BR>
 514 Show a summary of the in-use radius sessions.  This list should not be very
 515 long, as radius sessions should be cleaned up as soon as they are used.  The
 516 columns listed are:
 517 <TABLE>
 518         <TR><TD><B>Radius</B></TD><TD>The ID of the radius request.  This is
 519         sent in the packet to the radius server for identification.</TD></TR>
 520         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 521         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 522         <TR><TD><B>Session</B></TD><TD>The session ID that this radius
 523         request is associated with</TD></TR>
 524         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 525         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 526         <TR><TD><B>Try</B></TD><TD>Retry count.  The radius request is
 527         discarded after 3 retries.</TD></TR>
 528 </TABLE>
 529 <P>
 530 </LI>
 531
 532 <LI><B>show running-config</B><BR>
 533 This will list the current running configuration.  This is in a format that
 534 can either be pasted into the configuration file, or run directly at the
 535 command line.
 536 <P>
 537 </LI>
 538
 539 <LI><B>show counters</B><BR>
 540 Internally, counters are kept of key values, such as bytes and packets
 541 transferred, as well as function call counters.  This function displays all
 542 these counters, and is probably only useful for debugging.<P>
 543 You can reset these counters by running <EM>clear counters</EM>.
 544 <P>
 545 </LI>
 546
 547 <LI><B>show cluster</B><BR>
 548 Show cluster status.  Shows the cluster state for this server
 549 (Master/Slave), information about known peers and (for slaves) the
 550 master IP address, last packet seen and up-to-date status.<P>
 551 See <A HREF="#Clustering">Clustering</A> for more information.
 552 <P>
 553 </LI>
 554
 555 <LI><B>write memory</B><BR>
 556 This will write the current running configuration to the config file
 557 <B>startup-config</B>, which will be run on a restart.
 558 <P>
 559 </LI>
 560
 561 <LI><B>snoop</B><BR>
 562 You must specify a username, IP address and port.  All packets for the
 563 current session for that username will be forwarded to the given
 564 host/port.  Specify <EM>no snoop username</EM> to disable interception
 565 for the session.<P>
 566
 567 If you want interception to be permanent, you will have to modify the radius
 568 response for the user.  See <A HREF="#Interception">Interception</A>.
 569 <P>
 570 </LI>
 571
 572 <LI><B>throttle</B><BR>
 573 You must specify a username, which will be throttled for the current
 574 session.  Specify <EM>no throttle username</EM> to disable throttling
 575 for the current session.<P>
 576
 577 If you want throttling to be permanent, you will have to modify the
 578 radius response for the user.  See <A HREF="#THrottling">Throttling</A>.
 579 <P>
 580 </LI>
 581
 582 <LI><B>drop session</B><BR>
 583 This will cleanly disconnect a session.  You must specify a session id, which
 584 you can get from <EM>show session</EM>.  This will send a disconnect message
 585 to the remote end.
 586 <P>
 587 </LI>
 588
 589 <LI><B>drop tunnel</B><BR>
 590 This will cleanly disconnect a tunnel, as well as all sessions on that
 591 tunnel.  It will send a disconnect message for each session individually, and
 592 after 10 seconds it will send a tunnel disconnect message.
 593 <P>
 594 </LI>
 595
 596 <LI><B>uptime</B><BR>
 597 This will show how long the l2tpns process has been running, and the current
 598 bandwidth utilization:
 599 <PRE>
 600 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 601 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 602 </PRE>
 603 The bandwidth line contains 4 sets of values.<BR>
 604 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 605 (user uploads), in mbits/sec.<BR>
 606 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 607 downloads).<BR>
 608 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 609 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 610 <P>
 611 These counters are updated every second.
 612 <P>
 613 </LI>
 614
 615 <LI><B>configure terminal</B><BR>
 616 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 617 The following commands are valid in this mode:<P>
 618 </LI>
 619
 620 <LI><B>load plugin</B><BR>
 621 Load a plugin.  You must specify the plugin name, and it will search in
 622 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 623 <EM>remove plugin</EM>.
 624 <P>
 625 </LI>
 626
 627 <LI><B>set</B><BR>
 628 Set a configuration variable.  You must specify the variable name, and
 629 the value.  If the value contains any spaces, you should quote the
 630 value with double (") or single (') quotes.<P>
 631
 632 You can set any <A HREF="#startup-config">startup-config</A> value in
 633 this way, although some may require a restart to take effect.<P>
 634 </LI>
 635 </UL>
 636
 637 <H3 ID="nsctl">nsctl</H3>
 638
 639 nsctl was implemented (badly) to allow messages to be passed to modules.<P>
 640
 641 You must pass at least 2 parameters: <EM>host</EM> and <EM>command</EM>.  The
 642 host is the address of the l2tpns server which you want to send the message
 643 to.<P>
 644
 645 Command can currently be either <EM>garden</EM> or <EM>ungarden</EM>.  With
 646 both of these commands, you must give a session ID as the 3rd parameter.
 647 This will activate or deactivate the walled garden for a session
 648 temporarily.
 649
 650 <H3 ID="Signals">Signals</H3>
 651
 652 While the process is running, you can send it a few different signals, using
 653 the kill command.
 654 <PRE>
 655 killall -HUP l2tpns
 656 </PRE>
 657
 658 The signals understood are:
 659 <UL>
 660 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
 661 <LI>SIGTERM / SIGINT - Shut down for a restart.  This will dump the current
 662 state to disk (if <EM>save_state</EM> is set to true).  Upon restart, the
 663 process will read this saved state to resume active sessions.<P>
 664 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 665 every active session and tunnel before shutting down.  This is a good idea
 666 when upgrading the code, as no sessions will be left with the remote end
 667 thinking they are open.</LI>
 668 </UL>
 669
 670 <H2 ID="Throttling">Throttling</H2>
 671
 672 l2tpns contains support for slowing down user sessions to whatever speed you
 673 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 674 before this will be activated.<P>
 675
 676 If you wish a session to be throttled permanently, you should set the
 677 Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
 678 will be handled by the <EM>autothrottle</EM> module.<P>
 679
 680 Otherwise, you can enable and disable throttling an active session using
 681 the <EM>throttle</EM> CLI command.<P>
 682
 683 <H2 ID="Interception">Interception</H2>
 684
 685 You may have to deal with legal requirements to be able to intercept a
 686 user's traffic at any time.  l2tpns allows you to begin and end interception
 687 on the fly, as well as at authentication time.<P>
 688
 689 When a user is being intercepted, a copy of every packet they send and
 690 receive will be sent wrapped in a UDP packet to the IP address and port set
 691 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 692 variables.<P>
 693
 694 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 695
 696 To enable interception on a connected user, use the <EM>snoop username</EM>
 697 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 698 immediately.<P>
 699
 700 If you wish the user to be intercepted whenever they reconnect, you will
 701 need to modify the radius response to include the Vendor-Specific value
 702 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 703 you need to have the <EM>autosnoop</EM> module loaded.<P>
 704
 705 <H2 ID="Authentication">Authentication</H2>
 706
 707 Whenever a session connects, it is not fully set up until authentication is
 708 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 709 request to l2tpns.<P>
 710
 711 This request is sent to the radius server, which will hopefully respond with
 712 Auth-Accept or Auth-Reject.<P>
 713
 714 If Auth-Accept is received, the session is set up and an IP address is
 715 assigned.  The radius server can include a Framed-IP-Address field in the
 716 reply, and that address will be assigned to the client.  It can also include
 717 specific DNS servers, and a Framed-Route if that is required.<P>
 718
 719 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 720 at which point they should disconnect.  The exception to this is when the
 721 walled garden module is loaded, in which case the user still receives the
 722 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 723 should not receive any service.<P>
 724
 725 The radius reply can also contain a Vendor-Specific attribute called
 726 Cisco-Avpair.  This field is a freeform text field that most Cisco
 727 devices understand to contain configuration instructions for the session.  In
 728 the case of l2tpns it is expected to be of the form
 729 <PRE>
 730 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 731 </PRE>
 732
 733 Each key-value pair is separated and passed to any modules loaded.  The
 734 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 735 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 736 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 737 contain:
 738 <PRE>
 739 intercept=yes,throttle=yes
 740 </PRE>
 741
 742 <H2 ID="Plugins">Plugins</H2>
 743
 744 So as to make l2tpns as flexible as possible (I know the core code is pretty
 745 difficult to understand), it includes a plugin API, which you can use to
 746 hook into certain events.<P>
 747
 748 There are a few example modules included - autosnoop, autothrottle and
 749 garden.<P>
 750
 751 When an event happens that has a hook, l2tpns looks for a predefined
 752 function name in every loaded module, and runs them in the order the modules
 753 were loaded.<P>
 754
 755 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 756 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 757 modules should be run for this event.<P>
 758 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 759 no further processing should be done for this event.  <EM>Use this with care.</EM>
 760
 761 Every event function called takes a specific structure named
 762 param_<EM>event</EM>, which varies in content with each event.  The
 763 function name for each event will be <B>plugin_<EM>event</EM></B>,
 764 so for the event <EM>timer</EM>, the function declaration should look like:
 765 <PRE>
 766 int plugin_timer(struct param_timer *data);
 767 </PRE>
 768
 769 A list of the available events follows, with a list of all the fields in the
 770 supplied structure:
 771 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 772 <TABLE CELLSPACING=1 CELLPADDING=3>
 773         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 774         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 775                 <TD>This is called after a radius response has been
 776                 received, but before it has been processed by the
 777                 code.  This will allow you to modify the response in
 778                 some way.
 779                 </TD>
 780                 <TD>
 781                 <UL>
 782                         <LI>t - Tunnel ID</LI>
 783                         <LI>s - Session ID</LI>
 784                         <LI>username</LI>
 785                         <LI>password</LI>
 786                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 787                         <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
 788                 </UL>
 789                 </TD>
 790         </TR>
 791         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 792                 <TD>This is called after a radius response has been
 793                 received, and the basic checks have been performed.  This
 794                 is what the garden module uses to force authentication
 795                 to be accepted.
 796                 </TD>
 797                 <TD>
 798                 <UL>
 799                         <LI>t - Tunnel ID</LI>
 800                         <LI>s - Session ID</LI>
 801                         <LI>username</LI>
 802                         <LI>auth_allowed - This is already set to true or
 803                         false depending on whether authentication has been
 804                         allowed so far.  You can set this to 1 or 0 to force
 805                         allow or disallow authentication</LI>
 806                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 807                 </UL>
 808                 </TD>
 809         </TR>
 810         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 811                 <TD>This is called whenever a session receives a
 812                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 813                 seriously slow down the system.</FONT>
 814                 </TD>
 815                 <TD>
 816                 <UL>
 817                         <LI>t - Tunnel ID</LI>
 818                         <LI>s - Session ID</LI>
 819                         <LI>buf - The raw packet data</LI>
 820                         <LI>len - The length of buf</LI>
 821                 </UL>
 822                 </TD>
 823         </TR>
 824         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 825                 <TD>This is called whenever a session sends a
 826                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 827                 seriously slow down the system.</FONT>
 828                 </TD>
 829                 <TD>
 830                 <UL>
 831                         <LI>t - Tunnel ID</LI>
 832                         <LI>s - Session ID</LI>
 833                         <LI>buf - The raw packet data</LI>
 834                         <LI>len - The length of buf</LI>
 835                 </UL>
 836                 </TD>
 837         </TR>
 838         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 839                 <TD>This is run every second, no matter what is happening.
 840                 This is called from a signal handler, so make sure anything
 841                 you do is reentrant.
 842                 </TD>
 843                 <TD>
 844                 <UL>
 845                         <LI>time_now - The current unix timestamp</LI>
 846                 </UL>
 847                 </TD>
 848         </TR>
 849         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 850                 <TD>This is called after a session is fully set up.  The
 851                 session is now ready to handle traffic.
 852                 </TD>
 853                 <TD>
 854                 <UL>
 855                         <LI>t - Tunnel ID</LI>
 856                         <LI>s - Session ID</LI>
 857                 </UL>
 858                 </TD>
 859         </TR>
 860         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 861                 <TD>This is called when a session is about to be shut down.
 862                 This may be called multiple times for the same session.
 863                 </TD>
 864                 <TD>
 865                 <UL>
 866                         <LI>t - Tunnel ID</LI>
 867                         <LI>s - Session ID</LI>
 868                 </UL>
 869                 </TD>
 870         </TR>
 871         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 872                 <TD>This is called whenever a radius response includes a
 873                 Cisco-Avpair value.  The value is split up into
 874                 <EM>key=value</EM> pairs, and each is processed through all
 875                 modules.
 876                 </TD>
 877                 <TD>
 878                 <UL>
 879                         <LI>t - Tunnel ID</LI>
 880                         <LI>s - Session ID</LI>
 881                         <LI>key</LI>
 882                         <LI>value</LI>
 883                 </UL>
 884                 </TD>
 885         </TR>
 886         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 887                 <TD>This is called in whenever a nsctl packet is received.
 888                 This should handle the packet and form a response if
 889                 required.
 890                 </TD>
 891                 <TD>
 892                 <UL>
 893                         <LI>buf - The raw packet data</LI>
 894                         <LI>l - The raw packet data length</LI>
 895                         <LI>source_ip - Where the request came from</LI>
 896                         <LI>source_port - Where the request came from</LI>
 897                         <LI>response - Allocate a buffer and put your response in here</LI>
 898                         <LI>response_length - Length of response</LI>
 899                         <LI>send_response - true or false whether a response
 900                         should be sent.  If you set this to true, you must
 901                         allocate a response buffer.</LI>
 902                         <LI>type - Type of request (see nsctl.c)</LI>
 903                         <LI>id - ID of request</LI>
 904                         <LI>data - I'm really not sure</LI>
 905                         <LI>data_length - Length of data</LI>
 906                 </UL>
 907                 </TD>
 908         </TR>
 909 </TABLE>
 910 </TD></TR></TABLE>
 911
 912 <H2 ID="WalledGarden">Walled Garden</H2>
 913
 914 Walled Garden is implemented so that you can provide perhaps limited service
 915 to sessions that incorrectly authenticate.<P>
 916
 917 Whenever a session provides incorrect authentication, and the
 918 radius server responds with Auth-Reject, the walled garden module
 919 (if loaded) will force authentication to succeed, but set the flag
 920 <EM>garden</EM> in the session structure, and adds an iptables rule to
 921 the <B>garden_users</B> chain to force all packets for the session's IP
 922 address to traverse the <B>garden</B> chain.<P>
 923
 924 This doesn't <EM>just work</EM>.  To set this all up, you will to
 925 setup the <B>garden</B> nat table with the
 926 <A HREF="#build-garden">build-garden</A> script with rules to limit
 927 user's traffic.  For example, to force all traffic except DNS to be
 928 forwarded to 192.168.1.1, add these entries to your
 929 <EM>build-garden</EM>:
 930 <PRE>
 931 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
 932 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
 933 </PRE>
 934
 935 l2tpns will add entries to the garden_users chain as appropriate.<P>
 936
 937 You can check the amount of traffic being captured using the following
 938 command:
 939 <PRE>
 940 iptables -t nat -L garden -nvx
 941 </PRE>
 942
 943 <H2 ID="Clustering">Clustering</H2>
 944
 945 An l2tpns cluster consists of of one* or more servers configured with
 946 the same configuration, notably the multicast <B>cluster_address</B>.<P>
 947
 948 *A stand-alone server is simply a degraded cluster.<P>
 949
 950 Initially servers come up as cluster slaves, and periodically (every
 951 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
 952 containing the start time of the process to the multicast
 953 <B>cluster_address</B>.<P>
 954
 955 A cluster master sends heartbeat rather than ping packets, which
 956 contain those session and tunnel changes since the last heartbeat.<P>
 957
 958 When a slave has not seen a heartbeat within
 959 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
 960 examining the list of peers it has seen pings from and determines
 961 which of these and itself is the "best" candidate to be master.
 962 "Best" in this context means the server with the highest uptime (the
 963 highest IP address is used as a tie-breaker in the case of equal
 964 uptimes).<P>
 965
 966 After discovering a master, and determining that it is up-to-date (has
 967 seen an update for all in-use sessions and tunnels from heartbeat
 968 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
 969 the <B>bind_address</B> and for all addresses/networks in
 970 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
 971 the session state, as well as packets for throttled or gardened
 972 sessions are forwarded to the master for handling.  In addition, byte
 973 counters for session traffic are periodically forwarded.<P>
 974
 975 A master, when determining that it has at least one up-to-date slave
 976 will drop all routes (raising them again if all slaves disappear) and
 977 subsequently handle only packets forwarded to it by the slaves.<P>
 978
 979 <H2 ID="Routing">Routing</H2>
 980 If you are running a single instance, you may simply statically route
 981 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
 982 arp).<P>
 983
 984 For a cluster, configure the members as BGP neighbours on your router
 985 and configure multi-path load-balancing.  Cisco uses "maximum-paths
 986 ibgp" for IBGP.  If this is not supported by your IOS revision, you
 987 can use "maximum-paths" (which works for EBGP) and set
 988 <B>as_number</B> to a private value such as 64512.<P>
 989
 990 <H2 ID="Performance">Performance</H2>
 991
 992 Performance is great.<P>
 993
 994 I'd like to include some pretty graphs here that show a linear performance
 995 increase, with no impact by number of connected sessions.<P>
 996
 997 That's really what it looks like.<P>
 998
 999 <BR>
1000 David Parrish<BR>
1001 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1002 </BODY>
1003 </HTML>