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-<STYLE>
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<H1>L2TPNS Manual</H1>
<OL>
- <LI>Overview</LI>
- <LI>Installation</LI>
- <LI>Configuration</LI>
- <LI>Controlling the process</LI>
- <LI>Command-Line Interface</LI>
- <LI>Throttling</LI>
- <LI>Interception</LI>
- <LI>Authentication</LI>
- <LI>Plugins</LI>
- <LI>Walled Garden</LI>
- <LI>Clustering</LI>
- <LI>Performance</LI>
+ <LI><A HREF="#Overview">Overview</A></LI>
+ <LI><A HREF="#Installation">Installation</A>
+ <OL>
+ <LI><A HREF="#Requirements">Requirements</A></LI>
+ <LI><A HREF="#Compile">Compile</A></LI>
+ <LI><A HREF="#Install">Install</A></LI>
+ <LI><A HREF="#Running">Running</A></LI>
+ </OL>
+ </LI>
+ <LI><A HREF="#Configuration">Configuration</A>
+ <OL>
+ <LI><A HREF="#startup-config">startup-config</A></LI>
+ <LI><A HREF="#users">users</A></LI>
+ <LI><A HREF="#ip-pool">ip_pool</A></LI>
+ <LI><A HREF="#build-garden">build-garden</A></LI>
+ </OL>
+ </LI>
+ <LI><A HREF="#ControllingtheProcess">Controlling the Process</A>
+ <OL>
+ <LI><A HREF="#Command-LineInterface">Command-Line Interface</A></LI>
+ <LI><A HREF="#nsctl">nsctl</A></LI>
+ <LI><A HREF="#Signals">Signals</A></LI>
+ </OL>
+ </LI>
+ <LI><A HREF="#Throttling">Throttling</A></LI>
+ <LI><A HREF="#Interception">Interception</A></LI>
+ <LI><A HREF="#Authentication">Authentication</A></LI>
+ <LI><A HREF="#Plugins">Plugins</A></LI>
+ <LI><A HREF="#WalledGarden">Walled Garden</A></LI>
+ <LI><A HREF="#Filtering">Filtering</A></LI>
+ <LI><A HREF="#Clustering">Clustering</A></LI>
+ <LI><A HREF="#Routing">Routing</A></LI>
+ <LI><A HREF="#Performance">Performance</A></LI>
</OL>
-<H2>Overview</H2>
-L2TPNS is half of a complete L2TP implementation. It supports only the
+
+<H2 ID="Overview">Overview</H2>
+l2tpns is half of a complete L2TP implementation. It supports only the
LNS side of the connection.<P>
L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer 2
-protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. L2TPNS
+protocol (e.g. Ethernet, PPP) to be tunneled over an IP connection. l2tpns
implements PPP over L2TP only.<P>
-There are a couple of other L2TP imlementations, of which <A
+There are a couple of other L2TP im
plementations, of which <A
HREF="http://sourceforge.net/projects/l2tpd">l2tpd</A> is probably the
-most popular. l2tpd also will handle being either end of a tunnel, and
-is a lot more configurable than L2TPNS. However, due to the way it works,
+most popular. l2tpd also will handle being either end of a tunnel, and
+is a lot more configurable than l2tpns. However, due to the way it works,
it is nowhere near as scalable.<P>
-L2TPNS uses the TUN/TAP interface provided by the Linux kernel to receive
-and send packets. Using some packet manipulation it doesn't require a
+l2tpns uses the TUN/TAP interface provided by the Linux kernel to receive
+and send packets. Using some packet manipulation it doesn't require a
single interface per connection, as l2tpd does.<P>
This allows it to scale extremely well to very high loads and very high
numbers of connections.<P>
It also has a plugin architecture which allows custom code to be run
-during processing. An example of this is in the walled garden module
+during processing. An example of this is in the walled garden module
included.<P>
<BR>
-<EM>Documentation is not my best skill. If you find any problems
+<EM>Documentation is not my best skill. If you find any problems
with this document, or if you wish to contribute, please email <A
-HREF="mailto:
david@dparrish.com?subject=L2TPNS+Documentation">david@dparrish.com</A>.</EM><P>
+HREF="mailto:
l2tpns-users@lists.sourceforge.net?subject=L2TPNS+Documentation">the mailing list</A>.</EM><P>
-<H2>Installation</H2>
-<H3>Requirements</H3>
+<H2 ID="Installation">Installation</H2>
+<H3 ID="Requirements">Requirements</H3>
<OL>
<LI>Linux kernel version 2.4 or above, with the Tun/Tap interface either
compiled in, or as a module.</LI>
-<LI>libcli 1.
5 or greater.<BR>You can get this from <A
+<LI>libcli 1.
8.0 or greater.<BR>You can get this from <A
HREF="http://sourceforge.net/projects/libcli">http://sourceforge.net/projects/libcli</A></LI>
-
-<LI>The iproute2 user-space tools. These are used for throttling,
-so if you don't want to throttle then this is not required.<BR>You
-may also need to patch tc and the kernel to include HTB
-support. You can find the relevant patches and instructions at <A
-HREF="http://luxik.cdi.cz/~devik/qos/htb/">http://luxik.cdi.cz/~devik/qos/htb/</A>.</LI>
-
</OL>
-<H3>Compile</H3>
+<H3 ID="Compile">Compile</H3>
You can generally get away with just running <B>make</B> from the source
-directory. This will compile the daemon, associated tools and any modules
+directory. This will compile the daemon, associated tools and any modules
shipped with the distribution.<P>
-<H3>Install</H3>
+<H3 ID="Install">Install</H3>
After you have successfully compiled everything, run <B>make
-install</B> to install it. By default, the binaries are installed into
+install</B> to install it. By default, the binaries are installed into
<EM>/usr/sbin</EM>, the configuration into <EM>/etc/l2tpns</EM>, and the
modules into <EM>/usr/lib/l2tpns</EM>.<P>
-You will definately need to edit the configuration file before you start.
-See the Configuration section for more information.<P>
-
-You should also create the appropriate iptables chains if you want to use
-throttling or walled garden.
-<PRE>
-# Create the walled garden stuff
-iptables -t nat -N l2tpns
-iptables -t nat -F l2tpns
-iptables -t nat -A PREROUTING -j l2tpns
-iptables -t nat -A l2tpns -j garden_users
-# Create the throttling stuff
-iptables -t mangle -N l2tpns
-iptables -t mangle -F l2tpns
-iptables -t mangle -N throttle
-iptables -t mangle -F throttle
-iptables -t mangle -A PREROUTING -j l2tpns
-iptables -t mangle -A l2tpns -j throttle
-</PRE>
+You will definately need to edit the configuration files before you
+start. See the <A HREF="#Configuration">Configuration</A> section for
+more information.<P>
-<H3>Running it</H3>
+<H3 ID="Running">Running</H3>
-You only need to run <B>/usr/sbin/l2tpns</B> as root to start it. It does
+You only need to run <B>/usr/sbin/l2tpns</B> as root to start it. It does
not detach to a daemon process, so you should perhaps run it from init.<P>
By default there is no log destination set, so all log messages will go to
stdout.<P>
-<H2>Configuration</H2>
+<H2 ID="Configuration">Configuration</H2>
All configuration of the software is done from the files installed into
/etc/l2tpns.
-<H3>l2tpns.cfg</H3>
+<H3 ID="startup-config">startup-config</H3>
-This is the main configuration file for L2TPNS. The format of the file is a
-list of commands that can be run through the command-line interface. This
-file can also be written directly by the L2TPNS process if a user runs the
-<EM>write memory</EM> command, so any comments will be lost. However if your
+This is the main configuration file for l2tpns. The format of the file is a
+list of commands that can be run through the command-line interface. This
+file can also be written directly by the l2tpns process if a user runs the
+<EM>write memory</EM> command, so any comments will be lost. However if your
policy is not to write the config by the program, then feel free to comment
-the file with a # at the beginning of the line.<P>
+the file with a #
or ! at the beginning of the line.<P>
-A list of the possible configuration directives follows. Each of these
+A list of the possible configuration directives follows. Each of these
should be set by a line like:<P>
<PRE>
set configstring "value"
set boolean true
</PRE>
+<P>
<UL>
<LI><B>debug</B> (int)<BR>
-Sets the level of messages that will be written to the log file. The value
+Sets the level of messages that will be written to the log file. The value
should be between 0 and 5, with 0 being no debugging, and 5 being the
-highest. A rough description of the levels is:
+highest. A rough description of the levels is:
<OL>
<LI VALUE=0>Critical Errors - Things are probably broken</LI>
<LI>Errors - Things might have gone wrong, but probably will recover</LI>
<LI>Warnings - Just in case you care what is not quite perfect</LI>
<LI>Information - Parameters of control packets</LI>
<LI>Calls - For tracing the execution of the code</LI>
- <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
- </OL>
+ <LI>Packets - Everything, including a hex dump of all packets processed... probably twice</LI>
+ </OL><P>
Note that the higher you set the debugging level, the slower the program
-will run. Also, at level 5 a LOT of information will be logged. This should
+will run. Also, at level 5 a LOT of information will be logged. This should
only ever be used for working out why it doesn't work at all.
-<P>
</LI>
<LI><B>log_file</B> (string)<BR>
This will be where all logging and debugging information is written
-to. This can be either a filename, such as <EM>/var/log/l2tpns</EM>, or
+to. This may be either a filename, such as <EM>/var/log/l2tpns</EM>, or
the special magic string <EM>syslog:facility</EM>, where <EM>facility</EM>
is any one of the syslog logging facilities, such as local5.
-<P>
+</LI>
+
+<LI><B>pid_file</B> (string)<BR>
+If set, the process id will be written to the specified file. The
+value must be an absolute path.
</LI>
<LI><B>l2tp_secret</B> (string)<BR>
-This sets the string that L2TPNS will use for authenticating tunnel request.
-This must be the same as the LAC, or authentication will fail. This will
-only actually be used if the LAC requests authentication.
-<P>
+The secret used by l2tpns for authenticating tunnel request. Must be
+the same as the LAC, or authentication will fail. Only actually be
+used if the LAC requests authentication.
</LI>
-<LI><B>primary_dns</B> (ip address)<BR>
+<LI><B>primary_dns</B> (ip address)
+<LI><B>secondary_dns</B> (ip address)<BR>
Whenever a PPP connection is established, DNS servers will be sent to the
-user, both a primary and a secondary. If either is set to 0.0.0.0, then that
-one will not be sent.<BR>
-This sets the first DNS entry that will be sent.
-<P>
+user, both a primary and a secondary. If either is set to 0.0.0.0, then that
+one will not be sent.
</LI>
-<LI><B>secondary_dns</B> (ip address)<BR>
-See <EM>primary_dns</EM>.
-<P>
+<LI><B>primary_radius</B> (ip address)
+<LI><B>secondary_radius</B> (ip address)<BR>
+Sets the RADIUS servers used for both authentication and accounting.
+If the primary server does not respond, then the secondary RADIUS
+server will be tried.<br>
+<strong>Note:</strong> in addition to the source IP address and
+identifier, the RADIUS server <strong>must</strong> include the source
+port when detecting duplicates to supress (in order to cope with a
+large number of sessions comming on-line simultaneously l2tpns uses a
+set of udp sockets, each with a seperate identifier).
</LI>
-<LI><B>snoop_host</B> (ip address)<BR>
-Whenever a user is intercepted, a copy of their traffic will be sent to this
-IP address, using the port specified by <EM>snoop_port</EM>. Each packet
-will be sent as UDP.
-<P>
+<LI><B>primary_radius_port</B> (short)
+<LI><B>secondary_radius_port</B> (short)<BR>
+Sets the authentication ports for the primary and secondary RADIUS
+servers. The accounting port is one more than the authentication
+port. If no RADIUS ports are given, the authentication port defaults
+to 1645, and the accounting port to 1646.
</LI>
-<LI><B>snoop_port</B> (int)<BR>
-See <EM>snoop_host</EM>.
-<P>
+<LI><B>radius_accounting</B> (boolean)<BR>
+If set to true, then RADIUS accounting packets will be sent. This
+means that a Start record will be sent when the session is
+successfully authenticated, and a Stop record will be sent when the
+session is closed.
</LI>
-<LI><B>primary_radius</B> (ip address)<BR>
-This sets the primary radius server used for both authentication and
-accounting. If this server does not respond, then the secondary radius
-server will be used.
-<P>
+<LI><B>radius_secret</B> (string)<BR>
+This secret will be used in all RADIUS queries. If this is not set then
+RADIUS queries will fail.
</LI>
-<LI><B>secondary_radius</B> (ip address)<BR>
-See <EM>primary_radius</EM>.
-<P>
+<LI><B>bind_address</B> (ip address)<BR>
+When the tun interface is created, it is assigned the address
+specified here. If no address is given, 1.1.1.1 is used. Packets
+containing user traffic should be routed via this address if given,
+otherwise the primary address of the machine.
</LI>
-<LI><B>radius_accounting</B> (boolean)<BR>
-If set to true, then radius accounting packets will be sent. This means that
-a Start record will be sent when the session is successfully authenticated,
-and a Stop record will be sent when the session is closed.
-<P>
+<LI><B>peer_address</B> (ip address)<BR>
+Address to send to clients as the default gateway.
+</L1>
+
+<LI><B>send_garp</B> (boolean)<BR>
+Determines whether or not to send a gratuitous ARP for the
+bind_address when the server is ready to handle traffic (default:
+true).<BR>
+This value is ignored if BGP is configured.
</LI>
-<LI><B>radius_secret</B> (string)<BR>
-This secret will be used in all radius queries. If this is not set then
-radius queries will fail.
-<P>
+<LI><B>throttle_speed</B> (int)<BR>
+Sets the default speed (in kbits/s) which sessions will be limited to.
+If this is set to 0, then throttling will not be used at all. Note:
+You can set this by the CLI, but changes will not affect currently
+connected users.
</LI>
-<LI><B>bind_address</B> (ip address)<BR>
-When the tun interface is created, it is assigned the address specified
-here. If no address is given, 1.1.1.1 is used.<BR>
-If an address is given here, then packets containing user traffic should be
-routed via this address, otherwise the primary address of the machine.<BR>
-This is set automatically by the cluster master when taking over a failed
-machine.
-<P>
+<LI><B>throttle_buckets</B> (int)<BR>
+Number of token buckets to allocate for throttling. Each throttled
+session requires two buckets (in and out).
</LI>
-<LI><B>cluster_master</B> (ip address)<BR>
-This sets the address of the cluster master. See the <EM>Clustering</EM>
-section for more information on configuring a cluster.
-<P>
+<LI><B>accounting_dir</B> (string)<BR>
+If set to a directory, then every 5 minutes the current usage for
+every connected use will be dumped to a file in this directory. Each
+file dumped begins with a header, where each line is prefixed by #.
+Following the header is a single line for every connected user, fields
+separated by a space.<BR> The fields are username, ip, qos,
+uptxoctets, downrxoctets. The qos field is 1 if a standard user, and
+2 if the user is throttled.
</LI>
-<LI><B>throttle_speed</B> (int)<BR>
-Sets the speed (in kbits/s) which sessions will be limited to. If this is
-set to 0, then throttling will not be used at all. Note: You can set this by
-the CLI, but changes will not affect currently connected users.
-<P>
+<LI><B>setuid</B> (int)<BR>
+After starting up and binding the interface, change UID to this. This
+doesn't work properly.
</LI>
<LI><B>dump_speed</B> (boolean)<BR>
If set to true, then the current bandwidth utilization will be logged every
-second. Even if this is disabled, you can see this information by running
+second. Even if this is disabled, you can see this information by running
the <EM>uptime</EM> command on the CLI.
-<P>
</LI>
-<LI><B>setuid</B> (int)<BR>
-After starting up and binding the interface, change UID to this. This
-doesn't work properly.
-<P>
+<LI><B>cleanup_interval</B> (int)<BR>
+Interval between regular cleanups (in seconds).
</LI>
-<LI><B>accounting_dir</B> (string)<BR>
-If set to a directory, then every 5 minutes the current usage for every
-connected use will be dumped to a file. Each file dumped begins with a
-header, where each line is prefixed by #. Following the header is a single
-line for every connected user, fields separated by a space.<BR>
-The fields are username, ip, qos, uptxoctets, downrxoctets. The qos
-field is 1 if a standard user, and 2 if the user is throttled.
+<LI><B>multi_read_count</B> (int)<BR>
+Number of packets to read off each of the UDP and TUN fds when
+returned as readable by select (default: 10). Avoids incurring the
+unnecessary system call overhead of select on busy servers.
+</LI>
-<P>
+<LI><B>scheduler_fifo</B> (boolean)<BR>
+Sets the scheduling policy for the l2tpns process to SCHED_FIFO. This
+causes the kernel to immediately preempt any currently running SCHED_OTHER
+(normal) process in favour of l2tpns when it becomes runnable.
+Ignored on uniprocessor systems.
</LI>
-<LI><B>save_state</B> (boolean)<BR>
-If set to true, a state file will be dumped to disk when the process dies.
-This will be restored on startup, loading all active tunnels and sessions.
-<P>
+<LI><B>lock_pages</B> (boolean)<BR>
+Keep all pages mapped by the l2tpns process in memory.
</LI>
-</UL>
+<LI><B>icmp_rate</B> (int)<BR>
+Maximum number of host unreachable ICMP packets to send per second.
+</LI>
-<H3>l2tpns.users</H3>
+<LI><B>packet_limit</B> (int><BR>
+Maximum number of packets of downstream traffic to be handled each
+tenth of a second per session. If zero, no limit is applied (default:
+0). Intended as a DoS prevention mechanism and not a general
+throttling control (packets are dropped, not queued).
+</LI>
+
+<LI><B>cluster_address</B> (ip address)<BR>
+Multicast cluster address (default: 239.192.13.13). See the section
+on <A HREF="#Clustering">Clustering</A> for more information.
+</LI>
+
+<LI><B>cluster_interface</B> (string)<BR>
+Interface for cluster packets (default: eth0).
+</LI>
+
+<LI><B>cluster_hb_interval</B> (int)<BR>
+Interval in tenths of a second between cluster heartbeat/pings.
+</LI>
-This file's sole purpose is to manage access to the command-line
-interface. If this file doesn't exist, then anyone who can get to port
-23 will be allowed access without a username / password.<P>
+<LI><B>cluster_hb_timeout</B> (int)<BR>
+Cluster heartbeat timeout in tenths of a second. A new master will be
+elected when this interval has been passed without seeing a heartbeat
+from the master.
+</LI>
+</UL>
-If this is not what you want, then create this file and put in it a list of
-username / password pairs, separated by a <B>:</B>. e.g.:<P>
+<P>BGP routing configuration is entered by the command:
+The routing configuration section is entered by the command
+<DL><DD><B>router bgp</B> <I>as</I></DL>
+where <I>as</I> specifies the local AS number.
+
+<P>Subsequent lines prefixed with
+<DL><DD><B>neighbour</B> <I>peer</I></DL>
+define the attributes of BGP neighhbours. Valid commands are:
+<DL>
+ <DD><B>neighbour</B> <I>peer</I> <B>remote-as</B> <I>as</I>
+ <DD><B>neighbout</B> <I>peer</I> <B>timers</B> <I>keepalive hold</I>
+</DL>
+
+Where <I>peer</I> specifies the BGP neighbour as either a hostname or
+IP address, <I>as</I> is the remote AS number and <I>keepalive</I>,
+<I>hold</I> are the timer values in seconds.
+
+<P>Named access-lists are configured using one of the commands:
+<DL>
+ <DD><B>ip access-list standard</B> <I>name</I>
+ <DD><B>ip access-list extended</B> <I>name</I>
+</DL>
+
+<P>Subsequent lines prefixed with <B>permit</B> or <B>deny</B>
+define the body of the access-list. Standard access-list syntax:
+<DL>
+ <DD>{<B>permit</B>|<B>deny</B>}
+ {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
+ [{<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}]
+</DL>
+
+Extended access-lists:
+
+<DIV STYLE="margin-left: 4em; text-indent: -2em">
+ <P>{<B>permit</B>|<B>deny</B>} <B>ip</B>
+ {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
+ {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>} [<B>fragments</B>]
+ <P>{<B>permit</B>|<B>deny</B>} <B>udp</B>
+ {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
+ [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
+ {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
+ [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
+ [<B>fragments</B>]
+ <P>{<B>permit</B>|<B>deny</B>} <B>tcp</B>
+ {<I>host</I>|<I>source source-wildcard</I>|<B>any</B>}
+ [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
+ {<I>host</I>|<I>destination destination-wildcard</I>|<B>any</B>}
+ [{<B>eq</B>|<B>neq</B>|<B>gt</B>|<B>lt</B>} <I>port</I>|<B>range</B> <I>from</I> <I>to</I>]
+ [{<B>established</B>|{<B>match-any</B>|<B>match-all</B>}
+ {<B>+</B>|<B>-</B>}{<B>fin</B>|<B>syn</B>|<B>rst</B>|<B>psh</B>|<B>ack</B>|<B>urg</B>}
+ ...|<B>fragments</B>]
+</DIV>
+
+<H3 ID="users">users</H3>
+
+Usernames and passwords for the command-line interface are stored in
+this file. The format is <I>username</I><B>:</B><I>password</I> where
+<I>password</I> may either by plain text, an MD5 digest (prefixed by
+<B>$1</B><I>salt</I><B>$</B>) or a DES password, distinguished from
+plain text by the prefix <B>{crypt}</B>.<P>
+
+The username <B>enable</B> has a special meaning and is used to set
+the enable password.<P>
+
+<B>Note:</B> If this file doesn't exist, then anyone who can get to
+port 23 will be allowed access without a username / password.<P>
+
+<H3 ID="ip-pool">ip_pool</H3>
+
+This file is used to configure the IP address pool which user
+addresses are assigned from. This file should contain either an IP
+address or a CIDR network per line. e.g.:<P>
<PRE>
-user.1:randompassword
-fred:bhPe4rD1ME8.s
-bob:SP2RHKl3Q3qo6
+ 192.168.1.1
+ 192.168.1.2
+ 192.168.1.3
+ 192.168.4.0/24
+ 172.16.0.0/16
+ 10.0.0.0/8
</PRE>
-Keep in mind that the password should be in clear-text. There is no user
-privilege distinction, so anyone on this list will have full control of the
-system.<P>
+Keep in mind that l2tpns can only handle 65535 connections per
+process, so don't put more than 65535 IP addresses in the
+configuration file. They will be wasted.
-<H3>l2tpns.ip_pool</H3>
+<H3 ID="build-garden">build-garden</H3>
-This file is used to configure the IP address pool which user addresses are
-assigned from. This file should contain either an IP address or a IP mask
-per line. e.g.:<P>
+The garden plugin on startup creates a NAT table called "garden" then
+sources the <B>build-garden</B> script to populate that table. All
+packets from gardened users will be sent through this table. Example:
<PRE>
-192.168.1.1
-192.168.1.2
-192.168.1.3
-192.168.4.0/24
-172.16.0.0/16
-10.0.0.0/8
+ iptables -t nat -A garden -p tcp -m tcp --dport 25 -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p udp -m udp --dport 53 -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p tcp -m tcp --dport 53 -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p tcp -m tcp --dport 80 -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p tcp -m tcp --dport 110 -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p tcp -m tcp --dport 443 -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p icmp -m icmp --icmp-type echo-request -j DNAT --to 192.168.1.1
+ iptables -t nat -A garden -p icmp -j ACCEPT
+ iptables -t nat -A garden -j DROP
</PRE>
-Keep in mind that L2TPNS can only handle 65535 connections per process, so
-don't put more than 65535 IP addresses in the configuration file. They will
-be wasted.
+<H2 ID="ControllingtheProcess">Controlling the Process</H2>
-<H2>Controlling the process</H2>
-
-A running L2TPNS process can be controlled in a number of ways. The primary
+A running l2tpns process can be controlled in a number of ways. The primary
method of control is by the Command-Line Interface (CLI).<P>
You can also remotely send commands to modules via the nsctl client
-provided. This currently only works with the walled garden module, but
-modification is trivial to support other modules.<P>
+provided.<P>
-Also, there are a number of signals that L2TPNS understands and takes action
+Also, there are a number of signals that l2tpns understands and takes action
when it receives them.
-<H3>Command-Line Interface</H3>
+<H3 ID="Command-LineInterface">Command-Line Interface</H3>
-You can access the command line interface by telnet'ing to port 23. There is
-no IP address restriction, so it's a good idea to firewall this port off
-from anyone who doesn't need access to it. See l2tpns.users for information
-on restricting access based on a username and password.<P>
+You can access the command line interface by telnet'ing to port 23.
+There is no IP address restriction, so it's a good idea to firewall
+this port off from anyone who doesn't need access to it. See
+<A HREF="#users">users</A> for information on restricting access based
+on a username and password.<P>
The CLI gives you real-time control over almost everything in
-the process. The interface is designed to look like a CISCO
+the process. The interface is designed to look like a Cisco
device, and supports things like command history, line editing and
-context sensitive help. This is provided by linking with the <A
-HREF="http://sourceforge.net/projects/libcli">libcli</A> library.<P>
+context sensitive help. This is provided by linking with the
+<A HREF="http://sourceforge.net/projects/libcli">libcli</A>
+library. Some general documentation of the interface is
+<A HREF="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
+here</A>.<P>
After you have connected to the telnet port (and perhaps logged in), you
-will be presented with a
prompt <PRE>l2tpns></PRE><P>
+will be presented with a
<I>hostname</I><B>></B> prompt.<P>
-You can type <EM>help</EM> to get a list of all possible commands, but this
-list could be quite long. A brief overview of the more important commands
-follows:
+Enter <EM>help</EM> to get a list of possible commands. A brief
+overview of the more important commands follows:
<UL>
<LI><B>show session</B><BR>
Without specifying a session ID, this will list all tunnels currently
-connected. If you specify a session ID, you will be given all information on
-a single tunnel. Note that the full session list can be around 185 columns
-wide, so you should probably use a wide terminal to see the list
-properly.<P>
+connected. If you specify a session ID, you will be given all
+information on a single tunnel. Note that the full session list can
+be around 185 columns wide, so you should probably use a wide terminal
+
to see the list properly.<P>
The columns listed in the overview are:
<TABLE>
<TR><TD><B>SID</B></TD><TD>Session ID</TD></TR>
<TR><TD><B>TID</B></TD><TD>Tunnel ID - Use with <EM>show tunnel tid</EM></TD></TR>
<TR><TD><B>Username</B></TD><TD>The username given in the PPP
- authentication. If this is *, then LCP authentication has not
+ authentication. If this is *, then LCP authentication has not
completed.</TD></TR>
- <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
+ <TR><TD><B>IP</B></TD><TD>The IP address given to the session. If
this is 0.0.0.0, LCP negotiation has not completed.</TD></TR>
<TR><TD><B>I</B></TD><TD>Intercept - Y or N depending on whether the
- session is being snooped. See <EM>snoop</EM>.</TD></TR>
+ session is being snooped. See <EM>snoop</EM>.</TD></TR>
<TR><TD><B>T</B></TD><TD>Throttled - Y or N if the session is
- currently throttled. See <EM>throttle</EM>.</TD></TR>
+ currently throttled. See <EM>throttle</EM>.</TD></TR>
<TR><TD><B>G</B></TD><TD>Walled Garden - Y or N if the user is
- trapped in the walled garden. This field is present even if the
+ trapped in the walled garden. This field is present even if the
garden module is not loaded.</TD></TR>
<TR><TD><B>opened</B></TD><TD>The number of seconds since the
session started</TD></TR>
<TR><TD><B>LAC</B></TD><TD>The IP address of the LAC the session is
connected to.</TD></TR>
<TR><TD><B>CLI</B></TD><TD>The Calling-Line-Identification field
- provided during the session setup. This field is generated by the
+ provided during the session setup. This field is generated by the
LAC.</TD></TR>
</TABLE>
<P>
</LI>
+<LI><B>show users</B><BR>
+With no arguments, display a list of currently connected users. If an
+argument is given, the session details for the given username are
+displayed.
+</LI>
+
<LI><B>show tunnel</B><BR>
This will show all the open tunnels in a summary, or detail on a single
tunnel if you give a tunnel id.<P>
<TABLE>
<TR><TD><B>TID</B></TD><TD>Tunnel ID</TD></TR>
<TR><TD><B>Hostname</B></TD><TD>The hostname for the tunnel as
- provided by the LAC. This has no relation to DNS, it is just
+ provided by the LAC. This has no relation to DNS, it is just
a text field.</TD></TR>
<TR><TD><B>IP</B></TD><TD>The IP address of the LAC</TD></TR>
<TR><TD><B>State</B></TD><TD>Tunnel state - Free, Open, Dieing,
</LI>
<LI><B>show pool</B><BR>
-Displays the current IP address pool allocation. This will only display
+Displays the current IP address pool allocation. This will only display
addresses that are in use, or are reserved for re-allocation to a
disconnected user.<P>
If an address is not currently in use, but has been used, then in the User
</LI>
<LI><B>show radius</B><BR>
-Show a summary of the in-use radius sessions. This list should not be very
-long, as radius sessions should be cleaned up as soon as they are used. The
+Show a summary of the in-use RADIUS sessions. This list should not be very
+long, as RADIUS sessions should be cleaned up as soon as they are used. The
columns listed are:
<TABLE>
- <TR><TD><B>Radius</B></TD><TD>The ID of the radius request. This is
- sent in the packet to the radius server for identification.</TD></TR>
+ <TR><TD><B>Radius</B></TD><TD>The ID of the RADIUS request. This is
+ sent in the packet to the RADIUS server for identification.</TD></TR>
<TR><TD><B>State</B></TD><TD>The state of the request - WAIT, CHAP,
AUTH, IPCP, START, STOP, NULL.</TD></TR>
- <TR><TD><B>Session</B></TD><TD>The session ID that this radius
+ <TR><TD><B>Session</B></TD><TD>The session ID that this RADIUS
request is associated with</TD></TR>
<TR><TD><B>Retry</B></TD><TD>If a response does not appear to the
- request, it will retry at this time. This is a unix timestamp.</TD></TR>
- <TR><TD><B>Try</B></TD><TD>Retry count. The radius request is
+ request, it will retry at this time. This is a unix timestamp.</TD></TR>
+ <TR><TD><B>Try</B></TD><TD>Retry count. The RADIUS request is
discarded after 3 retries.</TD></TR>
</TABLE>
<P>
</LI>
<LI><B>show running-config</B><BR>
-This will list the current running configuration. This is in a format that
+This will list the current running configuration. This is in a format that
can either be pasted into the configuration file, or run directly at the
command line.
<P>
<LI><B>show counters</B><BR>
Internally, counters are kept of key values, such as bytes and packets
-transferred, as well as function call counters. This function displays all
+transferred, as well as function call counters. This function displays all
these counters, and is probably only useful for debugging.<P>
You can reset these counters by running <EM>clear counters</EM>.
<P>
</LI>
+<LI><B>show cluster</B><BR>
+Show cluster status. Shows the cluster state for this server
+(Master/Slave), information about known peers and (for slaves) the
+master IP address, last packet seen and up-to-date status.<P>
+See <A HREF="#Clustering">Clustering</A> for more information.
+<P>
+</LI>
+
<LI><B>write memory</B><BR>
This will write the current running configuration to the config file
-l2tpns.cfg, which will be run on a restart.
+<B>startup-config</B>, which will be run on a restart.
<P>
</LI>
<LI><B>snoop</B><BR>
-You must specify a username, which will be intercepted for the current
-session. Specify <EM>no snoop username</EM> to disable interception for the
-current session.<P>
-If you want interception to be permanent, you will have to modify the radius
-response for the user. See <EM>Interception</EM>.
+You must specify a username, IP address and port. All packets for the
+current session for that username will be forwarded to the given
+host/port. Specify <EM>no snoop username</EM> to disable interception
+for the session.<P>
+
+If you want interception to be permanent, you will have to modify the RADIUS
+response for the user. See <A HREF="#Interception">Interception</A>.
<P>
</LI>
<LI><B>throttle</B><BR>
You must specify a username, which will be throttled for the current
-session. Specify <EM>no throttle username</EM> to disable throttling for the
-current session.<P>
-If you want throttling to be permanent, you will have to modify the radius
-response for the user. See <EM>Throttling</EM>.
+session. Specify <EM>no throttle username</EM> to disable throttling
+for the current session.<P>
+
+If you want throttling to be permanent, you will have to modify the
+RADIUS response for the user. See <A HREF="#Throttling">Throttling</A>.
<P>
</LI>
<LI><B>drop session</B><BR>
-This will cleanly disconnect a session. You must specify a session id, which
-you can get from <EM>show session</EM>. This will send a disconnect message
+This will cleanly disconnect a session. You must specify a session id, which
+you can get from <EM>show session</EM>. This will send a disconnect message
to the remote end.
<P>
</LI>
<LI><B>drop tunnel</B><BR>
This will cleanly disconnect a tunnel, as well as all sessions on that
-tunnel. It will send a disconnect message for each session individually, and
+tunnel. It will send a disconnect message for each session individually, and
after 10 seconds it will send a tunnel disconnect message.
<P>
</LI>
-<LI><B>load plugin</B><BR>
-Load a plugin. You must specify the plugin name, and it will search in
-/usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
-<EM>remove plugin</EM>.
-<P>
-</LI>
-
-<LI><B>set</B><BR>
-Set a configuration variable. You must specify the variable name, and the
-value. If the value contains any spaces, you should quote the value with
-double quotes (").
-<P>
-</LI>
-
<LI><B>uptime</B><BR>
-This will show how long the L2TPNS process has been running, and the current
+This will show how long the l2tpns process has been running, and the current
bandwidth utilization:
<PRE>
17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
These counters are updated every second.
<P>
</LI>
+
+<LI><B>configure terminal</B><BR>
+Enter configuration mode. Use <EM>exit</EM> or ^Z to exit this mode.
+The following commands are valid in this mode:<P>
+</LI>
+
+<LI><B>load plugin</B><BR>
+Load a plugin. You must specify the plugin name, and it will search in
+/usr/lib/l2tpns for <EM>plugin</EM>.so. You can unload a loaded plugin with
+<EM>remove plugin</EM>.
+<P>
+</LI>
+
+<LI><B>set</B><BR>
+Set a configuration variable. You must specify the variable name, and
+the value. If the value contains any spaces, you should quote the
+value with double (") or single (') quotes.<P>
+
+You can set any <A HREF="#startup-config">startup-config</A> value in
+this way, although some may require a restart to take effect.<P>
+</LI>
</UL>
-<H3>nsctl</H3>
+<H3 ID="nsctl">nsctl</H3>
-nsctl
was implemented (badly) to allow messages to be passed to modules.<P>
+nsctl
allows messages to be passed to plugins.<P>
-You must pass at least 2 parameters: <EM>host</EM> and <EM>command</EM>. The
-host is the address of the L2TPNS server which you want to send the message
-to.<BR>
-Command can currently be either <EM>garden</EM> or <EM>ungarden</EM>. With
-both of these commands, you must give a session ID as the 3rd parameter.
-This will activate or deactivate the walled garden for a session
-temporarily.
+Arguments are <EM>command</EM> and optional <EM>args</EM>. See
+<STRONG>nsctl</STRONG>(8) for more details.<P>
-<H3>Signals</H3>
+Built-in command are <EM>load_plugin</EM>, <EM>unload_plugin</EM> and
+<EM>help</EM>. Any other commands are passed to plugins for processing.
+
+<H3 ID="Signals">Signals</H3>
While the process is running, you can send it a few different signals, using
the kill command.
The signals understood are:
<UL>
-<LI>SIGHUP - Reload the config from disk<P></LI>
-<LI>SIGTERM / SIGINT - Shut down for a restart. This will dump the current
-state to disk (if <EM>save_state</EM> is set to true). Upon restart, the
-process will read this saved state to resume active sessions. <P>
-This is really useful when doing an upgrade, as the code can change without
-dropping any users. However, if the internal structures such as
-<EM>sessiont</EM> or <EM>tunnelt</EM> change, then this saved state file
-will not reload, and none of the sessions will be recreated. This is bad.<P>
-If these structures do change, you should kill the server with SIGQUIT,
-which won't dump the state.</LI>
-<LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
-every active session and tunnel before shutting down. This is a good idea
-when upgrading the code, as no sessions will be left with the remote end
-thinking they are open.</LI>
+<LI>SIGHUP - Reload the config from disk and re-open log file</LI>
+<LI>SIGTERM / SIGINT - Shut down.</LI>
+<LI>SIGQUIT - Shut down cleanly. This will send a disconnect message for
+every active session and tunnel before shutting down.</LI>
</UL>
-<H2>Throttling</H2>
+<H2 ID="Throttling">Throttling</H2>
-L2TPNS contains support for slowing down user sessions to whatever speed you
-desire. You must first enable the global setting <EM>throttle_speed</EM>
-before this will be activated.
<P>
+l2tpns contains support for slowing down user sessions to whatever speed you
+desire. You must first enable the global setting <EM>throttle_speed</EM>
+before this will be activated.<P>
If you wish a session to be throttled permanently, you should set the
-Vendor-Specific radius value <B>Cisco-Avpair="throttle=yes"</B>, which
+Vendor-Specific RADIUS value <B>Cisco-Avpair="throttle=yes"</B>, which
will be handled by the <EM>autothrottle</EM> module.<P>
Otherwise, you can enable and disable throttling an active session using
the <EM>throttle</EM> CLI command.<P>
-Throttling is actually performed using a combination of iptables and tc.<BR>
-First, a HTB bucket is created using tc (unless one is already created and
-unused).<BR>
-Secondly, an iptables rule is inserted into the throttle chanin in the
-mangle table so all packets destined for the user's IP address go into the
-HTB.<P>
-
-You can check the packets being throttled using the tc command. Find the HTB
-handle by doing <EM>show session id</EM> in the CLI, next to the Filter
-Bucket tag. Then at the shell prompt, you can run:
-<PRE>
-tc -s class ls dev tun0 | grep -A3 <EM>1:870</EM>
-class htb 1:870 root prio 0 rate 28Kbit ceil 28Kbit burst 15Kb cburst 1634b
- Sent 27042557 bytes 41464 pkts (dropped 1876, overlimits 0)
- lended: 41471 borrowed: 0 giants: 0
- tokens: 3490743 ctokens: 353601
-</PRE>
-
-<H2>Interception</H2>
+<H2 ID="Interception">Interception</H2>
You may have to deal with legal requirements to be able to intercept a
-user's traffic at any time. L2TPNS allows you to begin and end interception
+user's traffic at any time. l2tpns allows you to begin and end interception
on the fly, as well as at authentication time.<P>
When a user is being intercepted, a copy of every packet they send and
The UDP packet contains just the raw IP frame, with no extra headers.<P>
To enable interception on a connected user, use the <EM>snoop username</EM>
-and <EM>no snoop username</EM> CLI commands. These will enable interception
+and <EM>no snoop username</EM> CLI commands. These will enable interception
immediately.<P>
If you wish the user to be intercepted whenever they reconnect, you will
-need to modify the radius response to include the Vendor-Specific value
-<B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
+need to modify the RADIUS response to include the Vendor-Specific value
+<B>Cisco-Avpair="intercept=yes"</B>. For this feature to be enabled,
you need to have the <EM>autosnoop</EM> module loaded.<P>
-<H2>Authentication</H2>
+<H2 ID="Authentication">Authentication</H2>
Whenever a session connects, it is not fully set up until authentication is
-completed. The remote end must send a PPP CHAP or PPP PAP authentication
+completed. The remote end must send a PPP CHAP or PPP PAP authentication
-This request is sent to the radius server, which will hopefully respond with
+This request is sent to the RADIUS server, which will hopefully respond with
Auth-Accept or Auth-Reject.<P>
If Auth-Accept is received, the session is set up and an IP address is
-assigned. The radius server can include a Framed-IP-Address field in the
-reply, and that address will be assigned to the client. It can also include
+assigned. The RADIUS server can include a Framed-IP-Address field in the
+reply, and that address will be assigned to the client. It can also include
specific DNS servers, and a Framed-Route if that is required.<P>
If Auth-Reject is received, then the client is sent a PPP AUTHNAK packet,
-at which point they should disconnect. The exception to this is when the
+at which point they should disconnect. The exception to this is when the
walled garden module is loaded, in which case the user still receives the
PPP AUTHACK, but their session is flagged as being a garden'd user, and they
should not receive any service.<P>
-The radius reply can also contain a Vendor-Specific attribute called
-Cisco-Avpair. This field is a freeform text field that most CISCO
-devices understand to contain configuration instructions for the session. In
-the case of L2TPNS it is expected to be of the form
+The RADIUS reply can also contain a Vendor-Specific attribute called
+Cisco-Avpair. This field is a freeform text field that most Cisco
+devices understand to contain configuration instructions for the session. In
+the case of l2tpns it is expected to be of the form
<PRE>
key=value,key2=value2,key3=value3,key<EM>n</EM>=<EM>value</EM>
</PRE>
-Each key-value pair is separated and passed to any modules loaded. The
+Each key-value pair is separated and passed to any modules loaded. The
<EM>autosnoop</EM> and <EM>autothrottle</EM> understand the keys
-<EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
+<EM>intercept</EM> and <EM>throttle</EM> respectively. For example, to have
a user who is to be throttled and intercepted, the Cisco-Avpair value should
contain:
<PRE>
intercept=yes,throttle=yes
</PRE>
-<H2>Plugins</H2>
+<H2 ID="Plugins">Plugins</H2>
-So as to make L2TPNS as flexible as possible (I know the core code is pretty
+So as to make l2tpns as flexible as possible (I know the core code is pretty
difficult to understand), it includes a plugin API, which you can use to
hook into certain events.<P>
There are a few example modules included - autosnoop, autothrottle and
garden.<P>
-When an event happens that has a hook, L2TPNS looks for a predefined
+When an event happens that has a hook, l2tpns looks for a predefined
function name in every loaded module, and runs them in the order the modules
were loaded.<P>
-The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
+The function should return <B>PLUGIN_RET_OK</B> if it is all OK. If it returns
<B>PLUGIN_RET_STOP</B>, then it is assumed to have worked, but that no further
modules should be run for this event.<P>
A return of <B>PLUGIN_RET_ERROR</B> means that this module failed, and
-no further processing should be done for this event. <EM>Use this with care.</EM>
+no further processing should be done for this event. <EM>Use this with care.</EM>
Every event function called takes a specific structure named
-param_<EM>event</EM>, which varies in content with each event. The
+param_<EM>event</EM>, which varies in content with each event. The
function name for each event will be <B>plugin_<EM>event</EM></B>,
so for the event <EM>timer</EM>, the function declaration should look like:
<PRE>
<TABLE CELLSPACING=1 CELLPADDING=3>
<TR BGCOLOR=LIGHTGREEN><TH><B>Event</B></TH><TH><B>Description</B></TH><TH><B>Parameters</B></TH></TR>
<TR VALIGN=TOP BGCOLOR=WHITE><TD><B>pre_auth</B></TD>
- <TD>This is called after a radius response has been
+ <TD>This is called after a RADIUS response has been
received, but before it has been processed by the
- code. This will allow you to modify the response in
+ code. This will allow you to modify the response in
some way.
</TD>
<TD>
</TD>
</TR>
<TR VALIGN=TOP BGCOLOR=WHITE><TD><B>post_auth</B></TD>
- <TD>This is called after a radius response has been
- received, and the basic checks have been performed. This
+ <TD>This is called after a RADIUS response has been
+ received, and the basic checks have been performed. This
is what the garden module uses to force authentication
to be accepted.
</TD>
<LI>username</LI>
<LI>auth_allowed - This is already set to true or
false depending on whether authentication has been
- allowed so far. You can set this to 1 or 0 to force
+ allowed so far. You can set this to 1 or 0 to force
allow or disallow authentication</LI>
<LI>protocol (0xC023 for PAP, 0xC223 for CHAP)</LI>
</UL>
</TR>
<TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_rx</B></TD>
<TD>This is called whenever a session receives a
- packet. <FONT COLOR=RED>Use this sparingly, as this will
+ packet. <FONT COLOR=RED>Use this sparingly, as this will
seriously slow down the system.</FONT>
</TD>
<TD>
</TR>
<TR VALIGN=TOP BGCOLOR=WHITE><TD><B>packet_tx</B></TD>
<TD>This is called whenever a session sends a
- packet. <FONT COLOR=RED>Use this sparingly, as this will
+ packet. <FONT COLOR=RED>Use this sparingly, as this will
seriously slow down the system.</FONT>
</TD>
<TD>
</TD>
</TR>
<TR VALIGN=TOP BGCOLOR=WHITE><TD><B>new_session</B></TD>
- <TD>This is called after a session is fully set up. The
+ <TD>This is called after a session is fully set up. The
session is now ready to handle traffic.
</TD>
<TD>
</TD>
</TR>
<TR VALIGN=TOP BGCOLOR=WHITE><TD><B>radius_response</B></TD>
- <TD>This is called whenever a radius response includes a
- Cisco-Avpair value. The value is split up into
+ <TD>This is called whenever a RADIUS response includes a
+ Cisco-Avpair value. The value is split up into
<EM>key=value</EM> pairs, and each is processed through all
modules.
</TD>
<LI>response - Allocate a buffer and put your response in here</LI>
<LI>response_length - Length of response</LI>
<LI>send_response - true or false whether a response
- should be sent. If you set this to true, you must
+ should be sent. If you set this to true, you must
allocate a response buffer.</LI>
<LI>type - Type of request (see nsctl.c)</LI>
<LI>id - ID of request</LI>
</TABLE>
</TD></TR></TABLE>
-<H2>Walled Garden</H2>
+<H2 ID="WalledGarden">Walled Garden</H2>
Walled Garden is implemented so that you can provide perhaps limited service
to sessions that incorrectly authenticate.<P>
Whenever a session provides incorrect authentication, and the
-radius server responds with Auth-Reject, the walled garden module
+RADIUS server responds with Auth-Reject, the walled garden module
(if loaded) will force authentication to succeed, but set the flag
<EM>garden</EM> in the session structure, and adds an iptables rule to
the <B>garden_users</B> chain to force all packets for the session's IP
address to traverse the <B>garden</B> chain.<P>
-This doesn't <EM>just work</EM>. To set this all up, you will need to create
-2 iptables chains on the nat table - <B>garden</B> and <B>garden_users</B>.
-<PRE>
-iptables -t nat -N garden
-iptables -t nat -F garden
-iptables -t nat -N garden_users
-iptables -t nat -F garden_users
-</PRE>
-
-You should add rules to the <B>garden</B> chain to limit user's traffic. For
-example, to force all traffic except DNS to be forwarded to 192.168.1.1, add
-these entries to your firewall startup script:
+This doesn't <EM>just work</EM>. To set this all up, you will to
+setup the <B>garden</B> nat table with the
+<A HREF="#build-garden">build-garden</A> script with rules to limit
+user's traffic. For example, to force all traffic except DNS to be
+forwarded to 192.168.1.1, add these entries to your
+<EM>build-garden</EM>:
<PRE>
iptables -t nat -A garden -p tcp --dport ! 53 -j DNAT --to 192.168.1.1
iptables -t nat -A garden -p udp --dport ! 53 -j DNAT --to 192.168.1.1
</PRE>
-
L2TPNS will add entries to the garden_users chain as appropriate.<P>
+
l2tpns will add entries to the garden_users chain as appropriate.<P>
You can check the amount of traffic being captured using the following
command:
iptables -t nat -L garden -nvx
</PRE>
-<H2>Clustering</H2>
+<H2 ID="Filtering">Filtering</H2>
+
+Sessions may be filtered by specifying <B>Filter-Id</B> attributes in
+the RADIUS reply. <I>filter</I>.<B>in</B> specifies that the named
+access-list <I>filter</I> should be applied to traffic from the
+customer, <I>filter</I>.<B>out</B> specifies a list for traffic to the
+customer.
+
+<H2 ID="Clustering">Clustering</H2>
+
+An l2tpns cluster consists of of one* or more servers configured with
+the same configuration, notably the multicast <B>cluster_address</B>.<P>
+
+*A stand-alone server is simply a degraded cluster.<P>
+
+Initially servers come up as cluster slaves, and periodically (every
+<B>cluster_hb_interval</B>/10 seconds) send out ping packets
+containing the start time of the process to the multicast
+<B>cluster_address</B>.<P>
+
+A cluster master sends heartbeat rather than ping packets, which
+contain those session and tunnel changes since the last heartbeat.<P>
+
+When a slave has not seen a heartbeat within
+<B>cluster_hb_timeout</B>/10 seconds it "elects" a new master by
+examining the list of peers it has seen pings from and determines
+which of these and itself is the "best" candidate to be master.
+"Best" in this context means the server with the highest uptime (the
+highest IP address is used as a tie-breaker in the case of equal
+uptimes).<P>
+
+After discovering a master, and determining that it is up-to-date (has
+seen an update for all in-use sessions and tunnels from heartbeat
+packets) will raise a route (see <A HREF="#Routing">Routing</A>) for
+the <B>bind_address</B> and for all addresses/networks in
+<B>ip_pool</B>. Any packets recieved by the slave which would alter
+the session state, as well as packets for throttled or gardened
+sessions are forwarded to the master for handling. In addition, byte
+counters for session traffic are periodically forwarded.<P>
+
+A master, when determining that it has at least one up-to-date slave
+will drop all routes (raising them again if all slaves disappear) and
+subsequently handle only packets forwarded to it by the slaves.<P>
+
+<H2 ID="Routing">Routing</H2>
+If you are running a single instance, you may simply statically route
+the IP pools to the <B>bind_address</B> (l2tpns will send a gratuitous
+arp).<P>
-Clustering is currently broken. But here's how it's supposed to work.<P>
+For a cluster, configure the members as BGP neighbours on your router
+and configure multi-path load-balancing. Cisco uses "maximum-paths
+ibgp" for IBGP. If this is not supported by your IOS revision, you
+can use "maximum-paths" (which works for EBGP) and set
+<B>as_number</B> to a private value such as 64512.<P>
-<H2>Performance</H2>
+<H2 ID="Performance">Performance</H2>
Performance is great.<P>
<BR>
David Parrish<BR>
-<A HREF="mailto:david@dparrish.com?subject=L2TPNS+Documentation">david@dparrsih.com</A>
+<A HREF="mailto:l2tpns-users@lists.sourceforge.net?subject=L2TPNS%20Documentation">l2tpns-users@lists.sourceforge.net</A>
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