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