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="#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 is half of a complete L2TP implementation.  It supports only the
  64 LNS side of the connection.<P>
  65
  66 L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
  67 protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection.  l2tpns
  68 implements PPP over L2TP only.<P>
  69
  70 There are a couple of other L2TP implementations, of which <A
  71 HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
  72 most popular.  l2tpd also will handle being either end of a tunnel, and
  73 is a lot more configurable than l2tpns.  However, due to the way it works,
  74 it is nowhere near as scalable.<P>
  75
  76 l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
  77 and send packets.  Using some packet manipulation it doesn't require a
  78 single interface per connection, as l2tpd does.<P>
  79
  80 This allows it to scale extremely well to very high loads and very high
  81 numbers of connections.<P>
  82
  83 It also has a plugin architecture which allows custom code to be run
  84 during processing.  An example of this is in the walled garden module
  85 included.<P>
  86
  87 <BR>
  88 <EM>Documentation is not my best skill.  If you find any problems
  89 with this document, or if you wish to contribute, please email <A
  90 HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
  91
  92 <H2 ID="Installation">Installation</H2>
  93 <H3 ID="Requirements">Requirements</H3>
  94
  95 <OL>
  96 <LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
  97 compiled in, or as a module.</LI>
  98
  99 <LI>libcli 1.8.0 or greater.<BR>You can get this from <A
 100 HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
 101 </OL>
 102
 103 <H3 ID="Compile">Compile</H3>
 104
 105 You can generally get away with just running <B>make</B> from the source
 106 directory.  This will compile the daemon, associated tools and any modules
 107 shipped with the distribution.<P>
 108
 109 <H3 ID="Install">Install</H3>
 110
 111 After you have successfully compiled everything, run <B>make
 112 install</B> to install it.  By default, the binaries are installed into
 113 <EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
 114 modules into <EM>/usr/lib/l2tpns</EM>.<P>
 115
 116 You will definately need to edit the configuration files before you
 117 start.  See the <A HREF="#Configuration">Configuration</A> section for
 118 more information.<P>
 119
 120 <H3 ID="Running">Running</H3>
 121
 122 You only need to run <B>/usr/sbin/l2tpns</B> as root to start it.  It does
 123 not detach to a daemon process, so you should perhaps run it from init.<P>
 124
 125 By default there is no log destination set, so all log messages will go to
 126 stdout.<P>
 127
 128 <H2 ID="Configuration">Configuration</H2>
 129
 130 All configuration of the software is done from the files installed into
 131 /etc/l2tpns.
 132
 133 <H3 ID="startup-config">startup-config</H3>
 134
 135 This is the main configuration file for l2tpns.  The format of the file is a
 136 list of commands that can be run through the command-line interface.  This
 137 file can also be written directly by the l2tpns process if a user runs the
 138 <EM>write memory</EM> command, so any comments will be lost.  However if your
 139 policy is not to write the config by the program, then feel free to comment
 140 the file with a # or ! at the beginning of the line.<P>
 141
 142 A list of the possible configuration directives follows.  Each of these
 143 should be set by a line like:<P>
 144 <PRE>
 145 set configstring "value"
 146 set ipaddress 192.168.1.1
 147 set boolean true
 148 </PRE>
 149
 150 <P>
 151 <UL>
 152 <LI><B>debug</B> (int)<BR>
 153 Sets the level of messages that will be written to the log file.  The value
 154 should be between 0 and 5, with 0 being no debugging, and 5 being the
 155 highest.  A rough description of the levels is:
 156         <OL>
 157         <LI VALUE=0>Critical Errors - Things are probably broken</LI>
 158         <LI>Errors - Things might have gone wrong, but probably will recover</LI>
 159         <LI>Warnings - Just in case you care what is not quite perfect</LI>
 160         <LI>Information - Parameters of control packets</LI>
 161         <LI>Calls - For tracing the execution of the code</LI>
 162         <LI>Packets - Everything, including a hex dump of all packets processed...  probably twice</LI>
 163         </OL><P>
 164 Note that the higher you set the debugging level, the slower the program
 165 will run.  Also, at level 5 a LOT of information will be logged.  This should
 166 only ever be used for working out why it doesn't work at all.
 167 </LI>
 168
 169 <LI><B>log_file</B> (string)<BR>
 170 This will be where all logging and debugging information is written
 171 to.  This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or
 172 the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
 173 is any one of the syslog logging facilities, such as local5.
 174 </LI>
 175
 176 <LI><B>pid_file</B> (string)<BR>
 177 If set, the process id will be written to the specified file.  The
 178 value must be an absolute path.
 179 </LI>
 180
 181 <LI><B>l2tp_secret</B> (string)<BR>
 182 The secret used by l2tpns for authenticating tunnel request.  Must be
 183 the same as the LAC, or authentication will fail.  Only actually be
 184 used if the LAC requests authentication.
 185 </LI>
 186
 187 <LI><B>primary_dns</B> (ip address)
 188 <LI><B>secondary_dns</B> (ip address)<BR>
 189 Whenever a PPP connection is established, DNS servers will be sent to the
 190 user, both a primary and a secondary.  If either is set to 0.0.0.0, then that
 191 one will not be sent.
 192 </LI>
 193
 194 <LI><B>save_state</B> (boolean)<BR>
 195 When l2tpns receives a STGTERM it will write out its current
 196 ip_address_pool, session and tunnel tables to disk prior to exiting to
 197 be re-loaded at startup.  The validity of this data is obviously quite
 198 short and the intent is to allow an sessions to be retained over a
 199 software upgrade.
 200 </LI>
 201
 202 <LI><B>primary_radius</B> (ip address)
 203 <LI><B>secondary_radius</B> (ip address)<BR>
 204 Sets the RADIUS servers used for both authentication and accounting.
 205 If the primary server does not respond, then the secondary RADIUS
 206 server will be tried.<br>
 207 <strong>Note:</strong> in addition to the source IP address and
 208 identifier, the RADIUS server <strong>must</strong> include the source
 209 port when detecting duplicates to supress (in order to cope with a
 210 large number of sessions comming on-line simultaneously l2tpns uses a
 211 set of udp sockets, each with a seperate identifier).
 212 </LI>
 213
 214 <LI><B>primary_radius_port</B> (short)
 215 <LI><B>secondary_radius_port</B> (short)<BR>
 216 Sets the authentication ports for the primary and secondary RADIUS
 217 servers.  The accounting port is one more than the authentication
 218 port.  If no RADIUS ports are given, the authentication port defaults
 219 to 1645, and the accounting port to 1646.
 220 </LI>
 221
 222 <LI><B>radius_accounting</B> (boolean)<BR>
 223 If set to true, then RADIUS accounting packets will be sent.  This
 224 means that a Start record will be sent when the session is
 225 successfully authenticated, and a Stop record will be sent when the
 226 session is closed.
 227 </LI>
 228
 229 <LI><B>radius_secret</B> (string)<BR>
 230 This secret will be used in all RADIUS queries.  If this is not set then
 231 RADIUS queries will fail.
 232 </LI>
 233
 234 <LI><B>bind_address</B> (ip address)<BR>
 235 When the tun interface is created, it is assigned the address
 236 specified here.  If no address is given, 1.1.1.1 is used.  Packets
 237 containing user traffic should be routed via this address if given,
 238 otherwise the primary address of the machine.
 239 </LI>
 240
 241 <LI><B>peer_address</B> (ip address)<BR>
 242 Address to send to clients as the default gateway.
 243 </L1>
 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 </LI>
 251
 252 <LI><B>throttle_speed</B> (int)<BR>
 253 Sets the default speed (in kbits/s) which sessions will be limited to.
 254 If this is set to 0, then throttling will not be used at all.  Note:
 255 You can set this by the CLI, but changes will not affect currently
 256 connected users.
 257 </LI>
 258
 259 <LI><B>throttle_buckets</B> (int)<BR>
 260 Number of token buckets to allocate for throttling.  Each throttled
 261 session requires two buckets (in and out).
 262 </LI>
 263
 264 <LI><B>accounting_dir</B> (string)<BR>
 265 If set to a directory, then every 5 minutes the current usage for
 266 every connected use will be dumped to a file in this directory.  Each
 267 file dumped begins with a header, where each line is prefixed by #.
 268 Following the header is a single line for every connected user, fields
 269 separated by a space.<BR> The fields are username, ip, qos,
 270 uptxoctets, downrxoctets.  The qos field is 1 if a standard user, and
 271 2 if the user is throttled.
 272 </LI>
 273
 274 <LI><B>setuid</B> (int)<BR>
 275 After starting up and binding the interface, change UID to this.  This
 276 doesn't work properly.
 277 </LI>
 278
 279 <LI><B>dump_speed</B> (boolean)<BR>
 280 If set to true, then the current bandwidth utilization will be logged every
 281 second.  Even if this is disabled, you can see this information by running
 282 the <EM>uptime</EM> command on the CLI.
 283 </LI>
 284
 285 <LI><B>cleanup_interval</B> (int)<BR>
 286 Interval between regular cleanups (in seconds).
 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 </LI>
 294
 295 <LI><B>scheduler_fifo</B> (boolean)<BR>
 296 Sets the scheduling policy for the l2tpns process to SCHED_FIFO.  This
 297 causes the kernel to immediately preempt any currently running SCHED_OTHER
 298 (normal) process in favour of l2tpns when it becomes runnable.
 299 Ignored on uniprocessor systems.
 300 </LI>
 301
 302 <LI><B>lock_pages</B> (boolean)<BR>
 303 Keep all pages mapped by the l2tpns process in memory.
 304 </LI>
 305
 306 <LI><B>icmp_rate</B> (int)<BR>
 307 Maximum number of host unreachable ICMP packets to send per second.
 308 </LI>
 309
 310 <LI><B>packet_limit</B> (int><BR>
 311 Maximum number of packets of downstream traffic to be handled each
 312 tenth of a second per session.  If zero, no limit is applied (default:
 313 0).  Intended as a DoS prevention mechanism and not a general
 314 throttling control (packets are dropped, not queued).
 315 </LI>
 316
 317 <LI><B>cluster_address</B> (ip address)<BR>
 318 Multicast cluster address (default:  239.192.13.13).  See the section
 319 on <A HREF="#Clustering">Clustering</A> for more information.
 320 </LI>
 321
 322 <LI><B>cluster_interface</B> (string)<BR>
 323 Interface for cluster packets (default: eth0).
 324 </LI>
 325
 326 <LI><B>cluster_hb_interval</B> (int)<BR>
 327 Interval in tenths of a second between cluster heartbeat/pings.
 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 </LI>
 335 </UL>
 336
 337 <P>BGP routing configuration is entered by the command:
 338 The routing configuration section is entered by the command
 339 <DL><DD><B>router bgp</B> <I>as</I></DL>
 340 where <I>as</I> specifies the local AS number.
 341
 342 <P>Subsequent lines prefixed with
 343 <DL><DD><B>neighbour</B> <I>peer</I></DL>
 344 define the attributes of BGP neighhbours.  Valid commands are:
 345 <DL>
 346   <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
 347   <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
 348 </DL>
 349
 350 Where <I>peer</I> specifies the BGP neighbour as either a hostname or
 351 IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
 352 <I>hold</I> are the timer values in seconds.
 353
 354 <P>Named access-lists are configured using one of the commands:
 355 <DL>
 356   <DD><B>ip access-list standard</B> <I>name</I>
 357   <DD><B>ip access-list extended</B> <I>name</I>
 358 </DL>
 359
 360 <P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
 361 define the body of the access-list.  Standard access-list syntax:
 362 <DL>
 363   <DD>{<B>permit</B>|<B>deny</B>}
 364     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 365     [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
 366 </DL>
 367
 368 Extended access-lists:
 369
 370 <DIV STYLE="margin-left: 4em; text-indent: -2em">
 371   <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
 372     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 373     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
 374   <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
 375     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 376         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 377     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 378         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 379         [<B>fragments</B>]
 380   <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
 381     {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
 382         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 383     {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
 384         [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
 385         [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
 386             {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
 387             ...|<B>fragments</B>]
 388 </DIV>
 389
 390 <H3 ID="users">users</H3>
 391
 392 Usernames and passwords for the command-line interface are stored in
 393 this file.  The format is <I>username</I><B>:</B><I>password</I> where
 394 <I>password</I> may either by plain text, an MD5 digest (prefixed by
 395 <B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
 396 plain text by the prefix <B>{crypt}</B>.<P>
 397
 398 The username <B>enable</B> has a special meaning and is used to set
 399 the enable password.<P>
 400
 401 <B>Note:</B> If this file doesn't exist, then anyone who can get to
 402 port 23 will be allowed access without a username / password.<P>
 403
 404 <H3 ID="ip-pool">ip_pool</H3>
 405
 406 This file is used to configure the IP address pool which user
 407 addresses are assigned from.  This file should contain either an IP
 408 address or a CIDR network per line.  e.g.:<P>
 409
 410 <PRE>
 411     192.168.1.1
 412     192.168.1.2
 413     192.168.1.3
 414     192.168.4.0/24
 415     172.16.0.0/16
 416     10.0.0.0/8
 417 </PRE>
 418
 419 Keep in mind that l2tpns can only handle 65535 connections per
 420 process, so don't put more than 65535 IP addresses in the
 421 configuration file.  They will be wasted.
 422
 423 <H3 ID="build-garden">build-garden</H3>
 424
 425 The garden plugin on startup creates a NAT table called "garden" then
 426 sources the <B>build-garden</B> script to populate that table.  All
 427 packets from gardened users will be sent through this table.  Example:
 428
 429 <PRE>
 430     iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
 431     iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
 432     iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
 433     iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
 434     iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
 435     iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
 436     iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
 437     iptables -t nat -A garden -p icmp -j ACCEPT
 438     iptables -t nat -A garden -j DROP
 439 </PRE>
 440
 441 <H2 ID="ControllingtheProcess">Controlling the Process</H2>
 442
 443 A running l2tpns process can be controlled in a number of ways.  The primary
 444 method of control is by the Command-Line Interface (CLI).<P>
 445
 446 You can also remotely send commands to modules via the nsctl client
 447 provided.<P>
 448
 449 Also, there are a number of signals that l2tpns understands and takes action
 450 when it receives them.
 451
 452 <H3 ID="Command-LineInterface">Command-Line Interface</H3>
 453
 454 You can access the command line interface by telnet'ing to port 23.
 455 There is no IP address restriction, so it's a good idea to firewall
 456 this port off from anyone who doesn't need access to it.  See
 457 <A HREF="#users">users</A> for information on restricting access based
 458 on a username and password.<P>
 459
 460 The CLI gives you real-time control over almost everything in
 461 the process.  The interface is designed to look like a Cisco
 462 device, and supports things like command history, line editing and
 463 context sensitive help.  This is provided by linking with the
 464 <A HREF="http://sourceforge.net/projects/libcli">libcli</A>
 465 library.  Some general documentation of the interface is
 466 <A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
 467 here</A>.<P>
 468
 469 After you have connected to the telnet port (and perhaps logged in), you
 470 will be presented with a <I>hostname</I><B>&gt;</B> prompt.<P>
 471
 472 Enter <EM>help</EM> to get a list of possible commands.  A brief
 473 overview of the more important commands follows:
 474
 475 <UL>
 476 <LI><B>show session</B><BR>
 477 Without specifying a session ID, this will list all tunnels currently
 478 connected.  If you specify a session ID, you will be given all
 479 information on a single tunnel.  Note that the full session list can
 480 be around 185 columns wide, so you should probably use a wide terminal
 481 to see the list properly.<P>
 482 The columns listed in the overview are:
 483 <TABLE>
 484         <TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
 485         <TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
 486         <TR><TD><B>Username</B></TD><TD>The username given in the PPP
 487         authentication.  If this is *, then LCP authentication has not
 488         completed.</TD></TR>
 489         <TR><TD><B>IP</B></TD><TD>The IP address given to the session.  If
 490         this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
 491         <TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
 492         session is being snooped.  See <EM>snoop</EM>.</TD></TR>
 493         <TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
 494         currently throttled.  See <EM>throttle</EM>.</TD></TR>
 495         <TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
 496         trapped in the walled garden.  This field is present even if the
 497         garden module is not loaded.</TD></TR>
 498         <TR><TD><B>opened</B></TD><TD>The number of seconds since the
 499         session started</TD></TR>
 500         <TR><TD><B>downloaded</B></TD><TD>Number of bytes downloaded by the user</TD></TR>
 501         <TR><TD><B>uploaded</B></TD><TD>Number of bytes uploaded by the user</TD></TR>
 502         <TR><TD><B>idle</B></TD><TD>The number of seconds since traffic was
 503         detected on the session</TD></TR>
 504         <TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
 505         connected to.</TD></TR>
 506         <TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
 507         provided during the session setup.  This field is generated by the
 508         LAC.</TD></TR>
 509 </TABLE>
 510 <P>
 511 </LI>
 512
 513 <LI><B>show users</B><BR>
 514 With no arguments, display a list of currently connected users.  If an
 515 argument is given, the session details for the given username are
 516 displayed.
 517 </LI>
 518
 519 <LI><B>show tunnel</B><BR>
 520 This will show all the open tunnels in a summary, or detail on a single
 521 tunnel if you give a tunnel id.<P>
 522 The columns listed in the overview are:
 523 <TABLE>
 524         <TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
 525         <TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
 526         provided by the LAC.  This has no relation to DNS, it is just
 527         a text field.</TD></TR>
 528         <TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
 529         <TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
 530         Opening</TD></TR>
 531         <TR><TD><B>Sessions</B></TD><TD>The number of open sessions on the
 532         tunnel</TD></TR>
 533 </TABLE>
 534 <P>
 535 </LI>
 536
 537 <LI><B>show pool</B><BR>
 538 Displays the current IP address pool allocation.  This will only display
 539 addresses that are in use, or are reserved for re-allocation to a
 540 disconnected user.<P>
 541 If an address is not currently in use, but has been used, then in the User
 542 column the username will be shown in square brackets, followed by the time
 543 since the address was used:
 544 <PRE>
 545 IP Address      Used  Session User
 546 192.168.100.6     N           [joe.user] 1548s
 547 </PRE>
 548 <P>
 549 </LI>
 550
 551 <LI><B>show radius</B><BR>
 552 Show a summary of the in-use RADIUS sessions.  This list should not be very
 553 long, as RADIUS sessions should be cleaned up as soon as they are used.  The
 554 columns listed are:
 555 <TABLE>
 556         <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request.  This is
 557         sent in the packet to the RADIUS server for identification.</TD></TR>
 558         <TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
 559         AUTH, IPCP, START, STOP, NULL.</TD></TR>
 560         <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
 561         request is associated with</TD></TR>
 562         <TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
 563         request, it will retry at this time.  This is a unix timestamp.</TD></TR>
 564         <TR><TD><B>Try</B></TD><TD>Retry count.  The RADIUS request is
 565         discarded after 3 retries.</TD></TR>
 566 </TABLE>
 567 <P>
 568 </LI>
 569
 570 <LI><B>show running-config</B><BR>
 571 This will list the current running configuration.  This is in a format that
 572 can either be pasted into the configuration file, or run directly at the
 573 command line.
 574 <P>
 575 </LI>
 576
 577 <LI><B>show counters</B><BR>
 578 Internally, counters are kept of key values, such as bytes and packets
 579 transferred, as well as function call counters.  This function displays all
 580 these counters, and is probably only useful for debugging.<P>
 581 You can reset these counters by running <EM>clear counters</EM>.
 582 <P>
 583 </LI>
 584
 585 <LI><B>show cluster</B><BR>
 586 Show cluster status.  Shows the cluster state for this server
 587 (Master/Slave), information about known peers and (for slaves) the
 588 master IP address, last packet seen and up-to-date status.<P>
 589 See <A HREF="#Clustering">Clustering</A> for more information.
 590 <P>
 591 </LI>
 592
 593 <LI><B>write memory</B><BR>
 594 This will write the current running configuration to the config file
 595 <B>startup-config</B>, which will be run on a restart.
 596 <P>
 597 </LI>
 598
 599 <LI><B>snoop</B><BR>
 600 You must specify a username, IP address and port.  All packets for the
 601 current session for that username will be forwarded to the given
 602 host/port.  Specify <EM>no snoop username</EM> to disable interception
 603 for the session.<P>
 604
 605 If you want interception to be permanent, you will have to modify the RADIUS
 606 response for the user.  See <A HREF="#Interception">Interception</A>.
 607 <P>
 608 </LI>
 609
 610 <LI><B>throttle</B><BR>
 611 You must specify a username, which will be throttled for the current
 612 session.  Specify <EM>no throttle username</EM> to disable throttling
 613 for the current session.<P>
 614
 615 If you want throttling to be permanent, you will have to modify the
 616 RADIUS response for the user.  See <A HREF="#Throttling">Throttling</A>.
 617 <P>
 618 </LI>
 619
 620 <LI><B>drop session</B><BR>
 621 This will cleanly disconnect a session.  You must specify a session id, which
 622 you can get from <EM>show session</EM>.  This will send a disconnect message
 623 to the remote end.
 624 <P>
 625 </LI>
 626
 627 <LI><B>drop tunnel</B><BR>
 628 This will cleanly disconnect a tunnel, as well as all sessions on that
 629 tunnel.  It will send a disconnect message for each session individually, and
 630 after 10 seconds it will send a tunnel disconnect message.
 631 <P>
 632 </LI>
 633
 634 <LI><B>uptime</B><BR>
 635 This will show how long the l2tpns process has been running, and the current
 636 bandwidth utilization:
 637 <PRE>
 638 17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
 639 Bandwidth: UDP-ETH:6/6  ETH-UDP:13/13  TOTAL:37.6   IN:3033 OUT:2569
 640 </PRE>
 641 The bandwidth line contains 4 sets of values.<BR>
 642 UDP-ETH is the current bandwidth going from the LAC to the ethernet
 643 (user uploads), in mbits/sec.<BR>
 644 ETH-UDP is the current bandwidth going from ethernet to the LAC (user
 645 downloads).<BR>
 646 TOTAL is the total aggregate bandwidth in mbits/s.<BR>
 647 IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
 648 <P>
 649 These counters are updated every second.
 650 <P>
 651 </LI>
 652
 653 <LI><B>configure terminal</B><BR>
 654 Enter configuration mode.  Use <EM>exit</EM> or ^Z to exit this mode.
 655 The following commands are valid in this mode:<P>
 656 </LI>
 657
 658 <LI><B>load plugin</B><BR>
 659 Load a plugin.  You must specify the plugin name, and it will search in
 660 /usr/lib/l2tpns for <EM>plugin</EM>.so.  You can unload a loaded plugin with
 661 <EM>remove plugin</EM>.
 662 <P>
 663 </LI>
 664
 665 <LI><B>set</B><BR>
 666 Set a configuration variable.  You must specify the variable name, and
 667 the value.  If the value contains any spaces, you should quote the
 668 value with double (") or single (') quotes.<P>
 669
 670 You can set any <A HREF="#startup-config">startup-config</A> value in
 671 this way, although some may require a restart to take effect.<P>
 672 </LI>
 673 </UL>
 674
 675 <H3 ID="nsctl">nsctl</H3>
 676
 677 nsctl allows messages to be passed to plugins.<P>
 678
 679 Arguments are <EM>command</EM> and optional <EM>args</EM>.  See
 680 <STRONG>nsctl</STRONG>(8) for more details.<P>
 681
 682 Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
 683 <EM>help</EM>.  Any other commands are passed to plugins for processing.
 684
 685 <H3 ID="Signals">Signals</H3>
 686
 687 While the process is running, you can send it a few different signals, using
 688 the kill command.
 689 <PRE>
 690 killall -HUP l2tpns
 691 </PRE>
 692
 693 The signals understood are:
 694 <UL>
 695 <LI>SIGHUP - Reload the config from disk and re-open log file<P></LI>
 696 <LI>SIGTERM / SIGINT - Shut down for a restart.  This will dump the current
 697 state to disk (if <EM>save_state</EM> is set to true).  Upon restart, the
 698 process will read this saved state to resume active sessions.<P>
 699 <LI>SIGQUIT - Shut down cleanly.  This will send a disconnect message for
 700 every active session and tunnel before shutting down.  This is a good idea
 701 when upgrading the code, as no sessions will be left with the remote end
 702 thinking they are open.</LI>
 703 </UL>
 704
 705 <H2 ID="Throttling">Throttling</H2>
 706
 707 l2tpns contains support for slowing down user sessions to whatever speed you
 708 desire.  You must first enable the global setting <EM>throttle_speed</EM>
 709 before this will be activated.<P>
 710
 711 If you wish a session to be throttled permanently, you should set the
 712 Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
 713 will be handled by the <EM>autothrottle</EM> module.<P>
 714
 715 Otherwise, you can enable and disable throttling an active session using
 716 the <EM>throttle</EM> CLI command.<P>
 717
 718 <H2 ID="Interception">Interception</H2>
 719
 720 You may have to deal with legal requirements to be able to intercept a
 721 user's traffic at any time.  l2tpns allows you to begin and end interception
 722 on the fly, as well as at authentication time.<P>
 723
 724 When a user is being intercepted, a copy of every packet they send and
 725 receive will be sent wrapped in a UDP packet to the IP address and port set
 726 in the <EM>snoop_host</EM> and <EM>snoop_port</EM> configuration
 727 variables.<P>
 728
 729 The UDP packet contains just the raw IP frame, with no extra headers.<P>
 730
 731 To enable interception on a connected user, use the <EM>snoop username</EM>
 732 and <EM>no snoop username</EM> CLI commands.  These will enable interception
 733 immediately.<P>
 734
 735 If you wish the user to be intercepted whenever they reconnect, you will
 736 need to modify the RADIUS response to include the Vendor-Specific value
 737 <B>Cisco-Avpair="intercept=yes"</B>.  For this feature to be enabled,
 738 you need to have the <EM>autosnoop</EM> module loaded.<P>
 739
 740 <H2 ID="Authentication">Authentication</H2>
 741
 742 Whenever a session connects, it is not fully set up until authentication is
 743 completed.  The remote end must send a PPP CHAP or PPP PAP authentication
 744 request to l2tpns.<P>
 745
 746 This request is sent to the RADIUS server, which will hopefully respond with
 747 Auth-Accept or Auth-Reject.<P>
 748
 749 If Auth-Accept is received, the session is set up and an IP address is
 750 assigned.  The RADIUS server can include a Framed-IP-Address field in the
 751 reply, and that address will be assigned to the client.  It can also include
 752 specific DNS servers, and a Framed-Route if that is required.<P>
 753
 754 If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
 755 at which point they should disconnect.  The exception to this is when the
 756 walled garden module is loaded, in which case the user still receives the
 757 PPP AUTHACK, but their session is flagged as being a garden'd user, and they
 758 should not receive any service.<P>
 759
 760 The RADIUS reply can also contain a Vendor-Specific attribute called
 761 Cisco-Avpair.  This field is a freeform text field that most Cisco
 762 devices understand to contain configuration instructions for the session.  In
 763 the case of l2tpns it is expected to be of the form
 764 <PRE>
 765 key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
 766 </PRE>
 767
 768 Each key-value pair is separated and passed to any modules loaded.  The
 769 <EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
 770 <EM>intercept</EM> and <EM>throttle</EM> respectively.  For example, to have
 771 a user who is to be throttled and intercepted, the Cisco-Avpair value should
 772 contain:
 773 <PRE>
 774 intercept=yes,throttle=yes
 775 </PRE>
 776
 777 <H2 ID="Plugins">Plugins</H2>
 778
 779 So as to make l2tpns as flexible as possible (I know the core code is pretty
 780 difficult to understand), it includes a plugin API, which you can use to
 781 hook into certain events.<P>
 782
 783 There are a few example modules included - autosnoop, autothrottle and
 784 garden.<P>
 785
 786 When an event happens that has a hook, l2tpns looks for a predefined
 787 function name in every loaded module, and runs them in the order the modules
 788 were loaded.<P>
 789
 790 The function should return <B>PLUGIN_RET_OK</B> if it is all OK.  If it returns
 791 <B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
 792 modules should be run for this event.<P>
 793 A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
 794 no further processing should be done for this event.  <EM>Use this with care.</EM>
 795
 796 Every event function called takes a specific structure named
 797 param_<EM>event</EM>, which varies in content with each event.  The
 798 function name for each event will be <B>plugin_<EM>event</EM></B>,
 799 so for the event <EM>timer</EM>, the function declaration should look like:
 800 <PRE>
 801 int plugin_timer(struct param_timer *data);
 802 </PRE>
 803
 804 A list of the available events follows, with a list of all the fields in the
 805 supplied structure:
 806 <TABLE CELLSPACING=0 CELLPADDING=0><TR BGCOLOR=LIGHTGREEN><TD>
 807 <TABLE CELLSPACING=1 CELLPADDING=3>
 808         <TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
 809         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
 810                 <TD>This is called after a RADIUS response has been
 811                 received, but before it has been processed by the
 812                 code.  This will allow you to modify the response in
 813                 some way.
 814                 </TD>
 815                 <TD>
 816                 <UL>
 817                         <LI>t - Tunnel ID</LI>
 818                         <LI>s - Session ID</LI>
 819                         <LI>username</LI>
 820                         <LI>password</LI>
 821                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 822                         <LI>continue_auth - Set to 0 to stop processing authentication modules</LI>
 823                 </UL>
 824                 </TD>
 825         </TR>
 826         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
 827                 <TD>This is called after a RADIUS response has been
 828                 received, and the basic checks have been performed.  This
 829                 is what the garden module uses to force authentication
 830                 to be accepted.
 831                 </TD>
 832                 <TD>
 833                 <UL>
 834                         <LI>t - Tunnel ID</LI>
 835                         <LI>s - Session ID</LI>
 836                         <LI>username</LI>
 837                         <LI>auth_allowed - This is already set to true or
 838                         false depending on whether authentication has been
 839                         allowed so far.  You can set this to 1 or 0 to force
 840                         allow or disallow authentication</LI>
 841                         <LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
 842                 </UL>
 843                 </TD>
 844         </TR>
 845         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
 846                 <TD>This is called whenever a session receives a
 847                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 848                 seriously slow down the system.</FONT>
 849                 </TD>
 850                 <TD>
 851                 <UL>
 852                         <LI>t - Tunnel ID</LI>
 853                         <LI>s - Session ID</LI>
 854                         <LI>buf - The raw packet data</LI>
 855                         <LI>len - The length of buf</LI>
 856                 </UL>
 857                 </TD>
 858         </TR>
 859         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
 860                 <TD>This is called whenever a session sends a
 861                 packet.  <FONT COLOR=RED>Use this sparingly, as this will
 862                 seriously slow down the system.</FONT>
 863                 </TD>
 864                 <TD>
 865                 <UL>
 866                         <LI>t - Tunnel ID</LI>
 867                         <LI>s - Session ID</LI>
 868                         <LI>buf - The raw packet data</LI>
 869                         <LI>len - The length of buf</LI>
 870                 </UL>
 871                 </TD>
 872         </TR>
 873         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>timer</B></TD>
 874                 <TD>This is run every second, no matter what is happening.
 875                 This is called from a signal handler, so make sure anything
 876                 you do is reentrant.
 877                 </TD>
 878                 <TD>
 879                 <UL>
 880                         <LI>time_now - The current unix timestamp</LI>
 881                 </UL>
 882                 </TD>
 883         </TR>
 884         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
 885                 <TD>This is called after a session is fully set up.  The
 886                 session is now ready to handle traffic.
 887                 </TD>
 888                 <TD>
 889                 <UL>
 890                         <LI>t - Tunnel ID</LI>
 891                         <LI>s - Session ID</LI>
 892                 </UL>
 893                 </TD>
 894         </TR>
 895         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>kill_session</B></TD>
 896                 <TD>This is called when a session is about to be shut down.
 897                 This may be called multiple times for the same session.
 898                 </TD>
 899                 <TD>
 900                 <UL>
 901                         <LI>t - Tunnel ID</LI>
 902                         <LI>s - Session ID</LI>
 903                 </UL>
 904                 </TD>
 905         </TR>
 906         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
 907                 <TD>This is called whenever a RADIUS response includes a
 908                 Cisco-Avpair value.  The value is split up into
 909                 <EM>key=value</EM> pairs, and each is processed through all
 910                 modules.
 911                 </TD>
 912                 <TD>
 913                 <UL>
 914                         <LI>t - Tunnel ID</LI>
 915                         <LI>s - Session ID</LI>
 916                         <LI>key</LI>
 917                         <LI>value</LI>
 918                 </UL>
 919                 </TD>
 920         </TR>
 921         <TR VALIGN=TOP BGCOLOR=WHITE><TD><B>control</B></TD>
 922                 <TD>This is called in whenever a nsctl packet is received.
 923                 This should handle the packet and form a response if
 924                 required.
 925                 </TD>
 926                 <TD>
 927                 <UL>
 928                         <LI>buf - The raw packet data</LI>
 929                         <LI>l - The raw packet data length</LI>
 930                         <LI>source_ip - Where the request came from</LI>
 931                         <LI>source_port - Where the request came from</LI>
 932                         <LI>response - Allocate a buffer and put your response in here</LI>
 933                         <LI>response_length - Length of response</LI>
 934                         <LI>send_response - true or false whether a response
 935                         should be sent.  If you set this to true, you must
 936                         allocate a response buffer.</LI>
 937                         <LI>type - Type of request (see nsctl.c)</LI>
 938                         <LI>id - ID of request</LI>
 939                         <LI>data - I'm really not sure</LI>
 940                         <LI>data_length - Length of data</LI>
 941                 </UL>
 942                 </TD>
 943         </TR>
 944 </TABLE>
 945 </TD></TR></TABLE>
 946
 947 <H2 ID="WalledGarden">Walled Garden</H2>
 948
 949 Walled Garden is implemented so that you can provide perhaps limited service
 950 to sessions that incorrectly authenticate.<P>
 951
 952 Whenever a session provides incorrect authentication, and the
 953 RADIUS server responds with Auth-Reject, the walled garden module
 954 (if loaded) will force authentication to succeed, but set the flag
 955 <EM>garden</EM> in the session structure, and adds an iptables rule to
 956 the <B>garden_users</B> chain to force all packets for the session's IP
 957 address to traverse the <B>garden</B> chain.<P>
 958
 959 This doesn't <EM>just work</EM>.  To set this all up, you will to
 960 setup the <B>garden</B> nat table with the
 961 <A HREF="#build-garden">build-garden</A> script with rules to limit
 962 user's traffic.  For example, to force all traffic except DNS to be
 963 forwarded to 192.168.1.1, add these entries to your
 964 <EM>build-garden</EM>:
 965 <PRE>
 966 iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
 967 iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
 968 </PRE>
 969
 970 l2tpns will add entries to the garden_users chain as appropriate.<P>
 971
 972 You can check the amount of traffic being captured using the following
 973 command:
 974 <PRE>
 975 iptables -t nat -L garden -nvx
 976 </PRE>
 977
 978 <H2 ID="Filtering">Filtering</H2>
 979
 980 Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
 981 the RADIUS reply.  <I>filter</I>.<B>in</B> specifies that the named
 982 access-list <I>filter</I> should be applied to traffic from the
 983 customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
 984 customer.
 985
 986 <H2 ID="Clustering">Clustering</H2>
 987
 988 An l2tpns cluster consists of of one* or more servers configured with
 989 the same configuration, notably the multicast <B>cluster_address</B>.<P>
 990
 991 *A stand-alone server is simply a degraded cluster.<P>
 992
 993 Initially servers come up as cluster slaves, and periodically (every
 994 <B>cluster_hb_interval</B>/10 seconds) send out ping packets
 995 containing the start time of the process to the multicast
 996 <B>cluster_address</B>.<P>
 997
 998 A cluster master sends heartbeat rather than ping packets, which
 999 contain those session and tunnel changes since the last heartbeat.<P>
1000
1001 When a slave has not seen a heartbeat within
1002 <B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
1003 examining the list of peers it has seen pings from and determines
1004 which of these and itself is the "best" candidate to be master.
1005 "Best" in this context means the server with the highest uptime (the
1006 highest IP address is used as a tie-breaker in the case of equal
1007 uptimes).<P>
1008
1009 After discovering a master, and determining that it is up-to-date (has
1010 seen an update for all in-use sessions and tunnels from heartbeat
1011 packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
1012 the <B>bind_address</B> and for all addresses/networks in
1013 <B>ip_pool</B>.  Any packets recieved by the slave which would alter
1014 the session state, as well as packets for throttled or gardened
1015 sessions are forwarded to the master for handling.  In addition, byte
1016 counters for session traffic are periodically forwarded.<P>
1017
1018 A master, when determining that it has at least one up-to-date slave
1019 will drop all routes (raising them again if all slaves disappear) and
1020 subsequently handle only packets forwarded to it by the slaves.<P>
1021
1022 <H2 ID="Routing">Routing</H2>
1023 If you are running a single instance, you may simply statically route
1024 the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
1025 arp).<P>
1026
1027 For a cluster, configure the members as BGP neighbours on your router
1028 and configure multi-path load-balancing.  Cisco uses "maximum-paths
1029 ibgp" for IBGP.  If this is not supported by your IOS revision, you
1030 can use "maximum-paths" (which works for EBGP) and set
1031 <B>as_number</B> to a private value such as 64512.<P>
1032
1033 <H2 ID="Performance">Performance</H2>
1034
1035 Performance is great.<P>
1036
1037 I'd like to include some pretty graphs here that show a linear performance
1038 increase, with no impact by number of connected sessions.<P>
1039
1040 That's really what it looks like.<P>
1041
1042 <BR>
1043 David Parrish<BR>
1044 <A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
1045 </BODY>
1046 </HTML>