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