+<?xml version="1.0"?>
+<!DOCTYPE article PUBLIC "-//OASIS//DTD DocBook XML V4.4//EN"
+ "http://docbook.org/xml/4.4/docbookx.dtd">
+
+<article>
+ <articleinfo>
+ <title>L2TPNS Manual</title>
+ </articleinfo>
+
+ <sect1 id="overview">
+ <title>Overview</title>
+ <para>
+ <command>l2tpns</command> is half of a complete L2TP
+ implementation. It supports only the LNS side of the
+ connection.
+ </para>
+
+ <para>
+ L2TP (Layer 2 Tunneling Protocol) is designed to allow any layer
+ 2 protocol (e.g. Ethernet, PPP) to be tunneled over an IP
+ connection. <command>l2tpns</command> implements PPP over L2TP
+ only.
+ </para>
+
+ <para>
+ There are a couple of other L2TP implementations, of which
+ <ulink url="http://sourceforge.net/projects/l2tpd">l2tpd</ulink>
+ is probably the most popular. l2tpd also will handle being
+ either end of a tunnel, and is a lot more configurable than
+ <command>l2tpns</command>. However, due to the way it works, it
+ is nowhere near as scalable.
+ </para>
+
+ <para>
+ <command>l2tpns</command> 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.
+ </para>
+
+ <para>
+ This allows it to scale extremely well to very high loads and
+ very high numbers of connections.
+ </para>
+
+ <para>
+ 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 included.
+ </para>
+ </sect1>
+
+ <sect1 id="installation">
+ <title>Installation</title>
+ <sect2 id="installation-requirements">
+ <title>Requirements</title>
+ <itemizedlist>
+ <listitem>
+ <para>
+ Linux kernel version 2.4 or above, with the Tun/Tap
+ interface either compiled in, or as a module.
+ </para>
+ </listitem>
+
+ <listitem>
+ <para>
+ libcli 1.8.5 or greater. You can get this from
+ <ulink url="http://sourceforge.net/projects/libcli">
+ SourceForge</ulink>
+ </para>
+ </listitem>
+ </itemizedlist>
+ </sect2>
+
+ <sect2 id="installation-compile">
+ <title>Compiling</title>
+ <para>
+ You can generally get away with just running
+ <command>make</command> from the source directory. This will
+ compile the daemon, associated tools and any modules shipped
+ with the distribution.
+ </para>
+ </sect2>
+
+ <sect2 id="installation-install">
+ <title>Installing</title>
+ <para>
+ After you have successfully compiled everything, run
+ <userinput>make install</userinput> to install it. By
+ default, the binaries are installed into
+ <filename>/usr/sbin</filename>, the configuration into
+ <filename>/etc/l2tpns</filename>, and the modules into
+ <filename>/usr/lib/l2tpns</filename>.
+ </para>
+
+ <para>
+ You will definately need to edit the configuration files
+ before you start. See <xref linkend="configuration"/> for
+ more information.
+ </para>
+ </sect2>
+
+ <sect2 id="installation-run">
+ <title>Running</title>
+ <para>
+ You only need to run <filename>/usr/sbin/l2tpns</filename> as
+ root to start it. It does not normally detach to a daemon
+ process (see the <option>-d</option> option), so you should
+ perhaps run it from <command>init</command>.
+ </para>
+
+ <para>
+ By default there is no log destination set, so all log
+ messages will go to stdout.
+ </para>
+ </sect2>
+ </sect1>
+
+ <sect1 id="configuration">
+ <title>Configuration</title>
+ <para>
+ All configuration of the software is done from the files
+ installed into <filename>/etc/l2tpns</filename>.
+ </para>
+
+ <sect2 id="config-startup">
+ <title><filename>startup-config</filename></title>
+ <para>
+ This is the main configuration file for
+ <command>l2tpns</command>. 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
+ <command>l2tpns</command> process if a user runs the
+ <userinput>write memory</userinput> 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 <literal>#</literal> or <literal>!</literal> at the
+ beginning of the line.
+ </para>
+
+ <para>
+ A list of the possible configuration directives follows. Each
+ of these should be set by a line like:
+<synopsis>
+set configstring "value"
+set ipaddress 192.168.1.1
+set boolean true
+</synopsis>
+ </para>
+
+ <variablelist>
+ <varlistentry>
+ <term><literal>debug</literal> (int)</term>
+ <listitem>
+ <para>
+ 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:
+
+ <variablelist>
+ <varlistentry>
+ <term><constant>0</constant>: Critical Errors</term>
+ <listitem>
+ <para>Things are probably broken</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>1</constant>: Errors</term>
+ <listitem>
+ <para>
+ Things might have gone wrong, but probably will
+ recover
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>2</constant>: Warnings</term>
+ <listitem>
+ <para>
+ Just in case you care what is not quite perfect
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>3</constant>: Information</term>
+ <listitem>
+ <para>Parameters of control packets</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>4</constant>: Calls</term>
+ <listitem>
+ <para>For tracing the execution of the code</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><constant>5</constant>: Packets</term>
+ <listitem>
+ <para>
+ Everything, including a hex dump of all packets
+ processed... probably twice
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+
+ <para>
+ Note that the higher you set the debugging level, the
+ slower the program will run. Also, at level 5 a
+ <emphasis>lot</emphasis> of information will be logged.
+ This should only ever be used for working out why it
+ doesn't work at all.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>log_file</literal> (string)</term>
+ <listitem>
+ <para>
+ This will be where all logging and debugging information
+ is written to. This may be either a filename, such as
+ <filename>/var/log/l2tpns</filename>, or the special
+ magic string
+ <literal>syslog:</literal><replaceable>facility</replaceable>,
+ where <replaceable>facility</replaceable> is any one of
+ the syslog logging facilities, such as
+ <literal>local5</literal>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>pid_file</literal> (string)</term>
+ <listitem>
+ <para>
+ If set, the process id will be written to the specified
+ file. The value must be an absolute path.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>random_device</literal> (string)</term>
+ <listitem>
+ <para>
+ Path to random data source (default
+ <filename>/dev/urandom</filename>). Use "" to use the
+ rand() library function.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>l2tp_secret</literal> (string)</term>
+ <listitem>
+ <para>
+ The secret used by <command>l2tpns</command> for
+ authenticating tunnel request. Must be the same as the
+ LAC, or authentication will fail. Only actually be used
+ if the LAC requests authentication.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>l2tp_mtu</literal> (int)</term>
+ <listitem>
+ <para>
+ MTU of interface for L2TP traffic (default:
+ <literal>1500</literal>). Used to set link MRU and
+ adjust TCP MSS.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>ppp_restart_time</literal> (int)</term>
+ <term><literal>ppp_max_configure</literal> (int)</term>
+ <term><literal>ppp_max_failure</literal> (int)</term>
+ <listitem>
+ <para>
+ PPP counter and timer values, as described in §4.1
+ of <ulink url="ftp://ftp.rfc-editor.org/in-notes/rfc1661.txt">
+ RFC1661</ulink>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>primary_dns</literal> (ip address)</term>
+ <term><literal>econdary_dns</literal> (ip address)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>primary_radius</literal> (ip address)</term>
+ <term><literal>secondary_radius</literal> (ip address)</term>
+ <listitem>
+ <para>
+ 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.
+
+ <note>
+ <para>
+ In addition to the source IP address and identifier,
+ the RADIUS server <emphasis>must</emphasis> include
+ the source port when detecting duplicates to supress
+ (in order to cope with a large number of sessions
+ comming on-line simultaneously
+ <command>l2tpns</command> uses a set of udp sockets,
+ each with a seperate identifier).
+ </para>
+ </note>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>primary_radius_port</literal> (short)</term>
+ <term><literal>secondary_radius_port</literal> (short)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>radius_accounting</literal> (boolean)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>radius_interim</literal> (int)</term>
+ <listitem>
+ <para>
+ If <literal>radius_accounting</literal> is on, defines
+ the interval between sending of RADIUS interim
+ accounting records (in seconds).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>radius_secret</literal> (string)</term>
+ <listitem>
+ <para>
+ This secret will be used in all RADIUS queries. If this
+ is not set then RADIUS queries will fail.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>radius_authtypes</literal> (string)</term>
+ <listitem>
+ <para>
+ A comma separated list of supported RADIUS
+ authentication methods (<literal>pap</literal> or
+ <literal>chap</literal>), in order of preference
+ (default <literal>pap</literal>).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>radius_dae_port</literal> (short)</term>
+ <listitem>
+ <para>
+ Port for DAE RADIUS (Packet of Death/Disconnect, Change
+ of Authorization) requests (default:
+ <literal>3799</literal>).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>allow_duplicate_users</literal> (boolean)</term>
+ <listitem>
+ <para>
+ Allow multiple logins with the same username. If false
+ (the default), any prior session with the same username
+ will be dropped when a new session is established.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>guest_account</literal> (string)</term>
+ <listitem>
+ <para>
+ Allow multiple logins matching this specific username.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>bind_address</literal> (ip address)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>peer_address</literal> (ip address)</term>
+ <listitem>
+ <para>Address to send to clients as the default gateway.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>send_garp</literal> (boolean)</term>
+ <listitem>
+ <para>
+ Determines whether or not to send a gratuitous ARP for
+ the bind_address when the server is ready to handle
+ traffic (default: <literal>true</literal>). This value
+ is ignored if BGP is configured.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>throttle_speed</literal> (int)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>throttle_buckets</literal> (int)</term>
+ <listitem>
+ <para>
+ Number of token buckets to allocate for throttling.
+ Each throttled session requires two buckets (in and
+ out).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>accounting_dir</literal> (string)</term>
+ <listitem>
+ <para>
+ 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 <code>#</code>.
+ Following the header is a single line for every
+ connected user, fields separated by a space.
+ </para>
+
+ <para>
+ The fields are username, ip, qos, uptxoctets,
+ downrxoctets. The qos field is 1 if a standard user,
+ and 2 if the user is throttled.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>dump_speed</literal> (boolean)</term>
+ <listitem>
+ <para>
+ 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 the
+ <userinput>uptime</userinput> command on the CLI.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>multi_read_count</literal> (int)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>scheduler_fifo</literal> (boolean)</term>
+ <listitem>
+ <para>
+ Sets the scheduling policy for the
+ <command>l2tpns</command> process to
+ <constant>SCHED_FIFO</constant>. This causes the kernel
+ to immediately preempt any currently running
+ <constant>SCHED_OTHER</constant> (normal) process in
+ favour of <command>l2tpns</command> when it becomes
+ runnable. Ignored on uniprocessor systems.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>lock_pages</literal> (boolean)</term>
+ <listitem>
+ <para>
+ Keep all pages mapped by the <command>l2tpns</command>
+ process in memory.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>icmp_rate</literal> (int)</term>
+ <listitem>
+ <para>
+ Maximum number of host unreachable ICMP packets to send
+ per second.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>packet_limit</literal> (int)</term>
+ <listitem>
+ <para>
+ 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).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>cluster_address</literal> (ip address)</term>
+ <listitem>
+ <para>
+ Multicast cluster address (default: 239.192.13.13).
+ See <xref linkend="clustering"/> for more information.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>cluster_interface</literal> (string)</term>
+ <listitem>
+ <para>Interface for cluster packets (default: eth0)</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>cluster_mcast_ttl</literal> (int)</term>
+ <listitem>
+ <para>TTL for multicast packets (default: 1).</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>cluster_hb_interval</literal> (int)</term>
+ <listitem>
+ <para>
+ Interval in tenths of a second between cluster
+ heartbeat/pings.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>cluster_hb_timeout</literal> (int)</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>cluster_master_min_adv</literal> (int)</term>
+ <listitem>
+ <para>
+ Determines the minumum number of up to date slaves
+ required before the master will drop routes (default: 1).
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term><literal>ipv6_prefix</literal> (ipv6 address)</term>
+ <listitem>
+ <para>
+ Enable negotiation of IPv6. This forms the the first 64
+ bits of the client allocated address. The remaining 64
+ come from the allocated IPv4 address and 4 bytes of 0s.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+
+ <sect3 id="config-startup-bgp">
+ <title>BGP</title>
+ <para>
+ BGP routing configuration is entered by the command:
+ <synopsis>router bgp <replaceable>as</replaceable></synopsis>
+ where <replaceable>as</replaceable> specifies the local AS
+ number.
+ </para>
+
+ <para>
+ Subsequent lines prefixed with
+ <synopsis>neighbour <replaceable>peer</replaceable></synopsis>
+ define the attributes of BGP neighhbours. Valid commands
+ are:
+<synopsis>
+neighbour <replaceable>peer</replaceable> remote-as <replaceable>as</replaceable>
+neighbour <replaceable>peer</replaceable> timers <replaceable>keepalive hold</replaceable>
+</synopsis>
+ </para>
+
+ <para>
+ Where <replaceable>peer</replaceable> specifies the BGP
+ neighbour as either a hostname or IP address,
+ <replaceable>as</replaceable> is the remote AS number and
+ <replaceable>keepalive</replaceable>,
+ <replaceable>hold</replaceable> are the timer values in
+ seconds.
+ </para>
+ </sect3>
+
+ <sect3 id="config-startup-acl">
+ <title>Access Lists</title>
+ <para>
+ Named access-lists are configured using one of the commands:
+<synopsis>
+ip access-list standard <replaceable>name</replaceable>
+ip access-list extended <replaceable>name</replaceable>
+</synopsis>
+ </para>
+
+ <para>
+ Subsequent lines prefixed with <literal>permit</literal> or
+ <literal>deny</literal> define the body of the access-list.
+ Standard access-list syntax:
+ </para>
+
+ <para role="hanging-indent">
+ {<literal>permit</literal>|<literal>deny</literal>}
+ {<replaceable>host</replaceable>|<replaceable>source
+ source-wildcard</replaceable>|<literal>any</literal>}
+ [{<replaceable>host</replaceable>|<replaceable>destination
+ destination-wildcard</replaceable>|<literal>any</literal>}]
+ </para>
+
+ <para>Extended access-lists:</para>
+ <para role="hanging-indent">
+ {<literal>permit</literal>|<literal>deny</literal>}
+ <literal>ip</literal>
+ {<replaceable>host</replaceable>|<replaceable>source
+ source-wildcard</replaceable>|<literal>any</literal>}
+ {<replaceable>host</replaceable>|<replaceable>destination
+ destination-wildcard</replaceable>|<literal>any</literal>}
+ [<literal>fragments</literal>]
+ </para>
+
+ <para role="hanging-indent">
+ {<literal>permit</literal>|<literal>deny</literal>}
+ <literal>udp</literal>
+ {<replaceable>host</replaceable>|<replaceable>source
+ source-wildcard</replaceable>|<literal>any</literal>}
+ [{<literal>eq</literal>|<literal>neq</literal>|<literal>gt</literal>|<literal>lt</literal>}
+ <replaceable>port</replaceable>|<literal>range</literal>
+ <replaceable>from</replaceable>
+ <replaceable>to</replaceable>]
+ {<replaceable>host</replaceable>|<replaceable>destination
+ destination-wildcard</replaceable>|<literal>any</literal>}
+ [{<literal>eq</literal>|<literal>neq</literal>|<literal>gt</literal>|<literal>lt</literal>}
+ <replaceable>port</replaceable>|<literal>range</literal>
+ <replaceable>from</replaceable>
+ <replaceable>to</replaceable>]
+ [<literal>fragments</literal>]
+ </para>
+
+ <para role="hanging-indent">
+ {<literal>permit</literal>|<literal>deny</literal>}
+ <literal>tcp</literal>
+ {<replaceable>host</replaceable>|<replaceable>source
+ source-wildcard</replaceable>|<literal>any</literal>}
+ [{<literal>eq</literal>|<literal>neq</literal>|<literal>gt</literal>|<literal>lt</literal>}
+ <replaceable>port</replaceable>|<literal>range</literal>
+ <replaceable>from</replaceable>
+ <replaceable>to</replaceable>]
+ {<replaceable>host</replaceable>|<replaceable>destination
+ destination-wildcard</replaceable>|<literal>any</literal>}
+ [{<literal>eq</literal>|<literal>neq</literal>|<literal>gt</literal>|<literal>lt</literal>}
+ <replaceable>port</replaceable>|<literal>range</literal>
+ <replaceable>from</replaceable>
+ <replaceable>to</replaceable>]
+ [{<literal>established</literal>|{<literal>match-any</literal>|<literal>match-all</literal>}
+ {<literal>+</literal>|<literal>-</literal>}{<literal>fin</literal>|<literal>syn</literal>|<literal>rst</literal>|<literal>psh</literal>|<literal>ack</literal>|<literal>urg</literal>}
+ ...|<literal>fragments</literal>]
+ </para>
+ </sect3>
+ </sect2>
+
+ <sect2 id="config-users">
+ <title><filename>users</filename></title>
+ <para>
+ Usernames and passwords for the command-line interface are
+ stored in this file. The format is
+<synopsis>
+<replaceable>username</replaceable>:<replaceable>password</replaceable>
+</synopsis>
+ where <replaceable>password</replaceable> may either by plain
+ text, an MD5 digest (prefixed by
+ <literal>$1</literal><replaceable>salt</replaceable><literal>$</literal>)
+ or a DES password, distinguished from plain text by the prefix
+ <literal>{crypt}</literal>.
+ </para>
+
+ <para>
+ The username <literal>enable</literal> has a special meaning
+ and is used to set the enable password.
+ </para>
+
+ <important>
+ <para>
+ If this file doesn't exist, then anyone who can get to port
+ 23 will be allowed access without a username or password.
+ </para>
+ </important>
+ </sect2>
+
+ <sect2 id="config-ip-pool">
+ <title><filename>ip_pool</filename></title>
+ <para>
+ 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.:
+
+<programlisting>
+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
+</programlisting>
+ </para>
+
+ <para>
+ Keep in mind that <command>l2tpns</command> can only handle
+ 65535 connections per process, so don't put more than 65535 IP
+ addresses in the configuration file. They will be
+ wasted.
+ </para>
+ </sect2>
+
+ <sect2 id="config-build-garden" xreflabel="build-garden">
+ <title><filename>build-garden</filename></title>
+ <para>
+ The garden plugin on startup creates a NAT table called
+ "garden" then sources the <filename>build-garden</filename>
+ script to populate that table. All packets from gardened
+ users will be sent through this table. Example:
+
+<programlisting>
+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
+</programlisting>
+ </para>
+ </sect2>
+ </sect1>
+
+ <sect1 id="operation">
+ <title>Operation</title>
+ <para>
+ A running l2tpns process can be controlled in a number of ways.
+ The primary method of control is by the Command-Line Interface
+ (CLI).
+ </para>
+
+ <para>
+ You can also remotely send commands to modules via the
+ <command>nsctl</command> client provided.
+ </para>
+
+ <para>
+ There are also a number of signals that l2tpns understands and
+ takes action when it receives them.
+ </para>
+
+ <sect2 id="operation-cli">
+ <title>Command-Line Interface</title>
+ <para>
+ You can access the command line interface by telneting 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 <xref linkend="config-users"/> for information on
+ restricting access based on a username and password.
+ </para>
+
+ <para>
+ The CLI gives you real-time control over almost everything in
+ 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 <ulink url="http://sourceforge.net/projects/libcli">
+ libcli</ulink> library. Some general documentation of the
+ interface is <ulink
+ url="http://sourceforge.net/docman/display_doc.php?docid=20501&group_id=79019">
+ here</ulink>.
+ </para>
+
+ <para>
+ After you have connected to the telnet port (and perhaps
+ logged in), you will be presented with a
+ <prompt><replaceable>hostname</replaceable>></prompt>
+ prompt.
+ </para>
+
+ <para>
+ Enter <userinput>help</userinput> to get a list of possible
+ commands, or press <userinput>?</userinput> for
+ context-specific help.
+ </para>
+
+ <para>
+ A brief overview of the more important commands
+ follows:
+
+ <variablelist>
+ <varlistentry id="operation-cli-show-session"
+ xreflabel="show session">
+ <term>
+ <userinput>show session [<replaceable>ID</replaceable>]
+ </userinput>
+ </term>
+
+ <listitem>
+ <para>
+ Detailed information for a specific session is
+ presented if you specify a session
+ <replaceable>ID</replaceable> argument.
+ </para>
+
+ <para>
+ If no <replaceable>ID</replaceable> is given, a
+ summary of all connected sessions is produced. Note
+ that this summary list can be around 185 columns wide,
+ so you should probably use a wide
+ terminal.
+ </para>
+
+ <para>
+ The columns listed in the summary are:
+
+ <informaltable>
+ <tgroup cols="3">
+ <colspec colname="col"/>
+ <colspec colname="desc"/>
+ <colspec colname="extra"/>
+ <tbody>
+ <row>
+ <entry><literal>SID</literal></entry>
+ <entry namest="desc" nameend="extra">Session ID</entry>
+ </row>
+ <row>
+ <entry><literal>TID</literal></entry>
+ <entry>Tunnel ID</entry>
+ <entry>
+ See also the <xref
+ linkend="operation-cli-show-tunnel"/> CLI
+ command.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>Username</literal></entry>
+ <entry>
+ The username given in the PPP authentication.
+ </entry>
+ <entry>
+ If this is *, then LCP authentication has
+ not completed.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>IP</literal></entry>
+ <entry>The IP address given to the session.</entry>
+ <entry>
+ If this is 0.0.0.0, IPCP negotiation has not
+ completed
+ </entry>
+ </row>
+ <row>
+ <entry><literal>I</literal></entry>
+ <entry>Intercept</entry>
+ <entry>
+ Y or N: indicates whether the session is
+ being snooped. See also the
+ <xref linkend="operation-cli-snoop"/>
+ CLI command.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>T</literal></entry>
+ <entry>Throttled</entry>
+ <entry>
+ Y or N: indicates whether the session is
+ currently throttled. See also the
+ <xref linkend="operation-cli-throttle"/>
+ CLI command.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>G</literal></entry>
+ <entry>Walled Garden</entry>
+ <entry>
+ Y or N: indicates whether the user is
+ trapped in the walled garden. This field is
+ present even if the garden module is not
+ loaded.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>6</literal></entry>
+ <entry>IPv6</entry>
+ <entry>
+ Y or N: indicates whether the session has
+ IPv6 active (IPV6CP open)
+ </entry>
+ </row>
+ <row>
+ <entry><literal>opened</literal></entry>
+ <entry namest="desc" nameend="extra">
+ The number of seconds since the
+ session started
+ </entry>
+ </row>
+ <row>
+ <entry><literal>downloaded</literal></entry>
+ <entry namest="desc" nameend="extra">
+ Number of bytes downloaded by the user
+ </entry>
+ </row>
+ <row>
+ <entry><literal>uploaded</literal></entry>
+ <entry namest="desc" nameend="extra">
+ Number of bytes uploaded by the user
+ </entry>
+ </row>
+ <row>
+ <entry><literal>idle</literal></entry>
+ <entry namest="desc" nameend="extra">
+ The number of seconds since traffic was
+ detected on the session
+ </entry>
+ </row>
+ <row>
+ <entry><literal>LAC</literal></entry>
+ <entry namest="desc" nameend="extra">
+ The IP address of the LAC the session is
+ connected to.
+ </entry>
+ </row>
+ <row>
+ <entry><literal>CLI</literal></entry>
+ <entry namest="desc" nameend="extra">
+ The Calling-Line-Identification field
+ provided during the session setup. This
+ field is generated by the LAC.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-user" xreflabel="show user">
+ <term>
+ <userinput>show users</userinput>
+ </term>
+ <term>
+ <userinput>show user <replaceable>username</replaceable>
+ </userinput>
+ </term>
+
+ <listitem>
+ <para>
+ With no arguments, display a list of currently
+ connected users. If an argument is given, the session
+ details for the given
+ <replaceable>username</replaceable> are displayed.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-tunnel" xreflabel="show tunnel">
+ <term>
+ <userinput>show tunnel [<replaceable>ID</replaceable>]</userinput>
+ </term>
+
+ <listitem>
+ <para>
+ Produce a summary list of all open tunnels, or detail
+ on a specific tunnel <replaceable>ID</replaceable>.
+ </para>
+
+ <para>
+ The columns listed in the summary are:
+
+ <informaltable>
+ <tgroup cols="2">
+ <tbody>
+ <row>
+ <entry>TID</entry>
+ <entry>Tunnel ID</entry>
+ </row>
+ <row>
+ <entry>Hostname</entry>
+ <entry>
+ The hostname for the tunnel as provided by
+ the LAC. This has no relation to DNS, it is
+ just a text field.
+ </entry>
+ </row>
+ <row>
+ <entry>IP</entry>
+ <entry>The IP address of the LAC</entry>
+ </row>
+ <row>
+ <entry>State</entry>
+ <entry>
+ Tunnel state: Free, Open, Dieing, Opening
+ </entry>
+ </row>
+ <row>
+ <entry>Sessions</entry>
+ <entry>The number of open sessions on the tunnel</entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-pool" xreflabel="show pool">
+ <term><userinput>show pool</userinput></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+
+ <para>
+ If an address is not currently in use, but has been
+ used, then in the User column the username will be
+ shown in square brackets, followed by the time since
+ the address was used:
+
+<screen>
+IP Address Used Session User
+192.168.100.6 N [joe.user] 1548s
+</screen>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-radius" xreflabel="show radius">
+ <term><userinput>show radius</userinput></term>
+ <listitem>
+ <para>
+ 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:
+
+ <informaltable>
+ <tgroup cols="2">
+ <tbody>
+ <row>
+ <entry>Radius</entry>
+ <entry>
+ The ID of the RADIUS request. This is sent
+ in the packet to the RADIUS server for
+ identification
+ </entry>
+ </row>
+ <row>
+ <entry>State</entry>
+ <entry>
+ The state of the request: WAIT, CHAP, AUTH,
+ IPCP, START, STOP or NULL
+ </entry>
+ </row>
+ <row>
+ <entry>Session</entry>
+ <entry>
+ The session ID that this RADIUS request is
+ associated with
+ </entry>
+ </row>
+ <row>
+ <entry>Retry</entry>
+ <entry>
+ If a response does not appear to the
+ request, it will retry at this time. This
+ is a Unix timestamp
+ </entry>
+ </row>
+ <row>
+ <entry>Try</entry>
+ <entry>
+ Retry count. The RADIUS request is
+ discarded after 3 retries
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-run" xreflabel="show run">
+ <term><userinput>show running-config</userinput></term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-counters"
+ xreflabel="show counters">
+ <term><userinput>show counters</userinput></term>
+ <listitem>
+ <para>
+ Internally, counters are kept of key values, such as
+ bytes and packets transferred, as well as function
+ call counters. This function displays all these
+ counters, and is probably only useful for debugging.
+ </para>
+
+ <para>
+ You can reset these counters by running
+ <userinput>clear counters</userinput>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-show-cluster"
+ xreflabel="show cluster">
+ <term><userinput>show cluster</userinput></term>
+ <listitem>
+ <para>
+ 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. See
+ <xref linkend="clustering"/> for more information.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-write-mem" xreflabel="write memory">
+ <term><userinput>write memory</userinput></term>
+ <listitem>
+ <para>
+ This will write the current running configuration to
+ the config file <filename>startup-config</filename>,
+ which will be run on a restart.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-snoop" xreflabel="snoop">
+ <term>
+ <userinput>snoop <replaceable>user</replaceable>
+ <replaceable>IP</replaceable>
+ <replaceable>port</replaceable></userinput>
+ </term>
+ <listitem>
+ <para>
+ 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
+ <userinput>no snoop
+ <replaceable>username</replaceable></userinput> to
+ disable interception for the session.
+ </para>
+
+ <para>
+ If you want interception to be permanent, you will
+ have to modify the RADIUS response for the user. See
+ <xref linkend="interception"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-throttle" xreflabel="throttle">
+ <term>
+ <userinput>throttle <replaceable>user</replaceable>
+ [in|out] <replaceable>rate</replaceable></userinput>
+ </term>
+ <listitem>
+ <para>
+ You must specify a username, which will be throttled
+ for the current session to
+ <replaceable>rate</replaceable> Kbps. Prefix
+ <replaceable>rate</replaceable> with
+ <userinput>in</userinput> or
+ <userinput>out</userinput> to set different upstream
+ and downstream rates.
+ </para>
+
+ <para>
+ Specify <userinput>no throttle
+ <replaceable>username</replaceable></userinput> to
+ disable throttling for the current session.
+ </para>
+
+ <para>
+ If you want throttling to be permanent, you will have
+ to modify the RADIUS response for the user. See <xref
+ linkend="throttling"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-drop-session"
+ xreflabel="drop session">
+ <term>
+ <userinput>drop <replaceable>session</replaceable></userinput>
+ </term>
+ <listitem>
+ <para>
+ This will cleanly disconnect the session specified by
+ <replaceable>session</replaceable> ID.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-drop-tunnel" xreflabel="drop tunnel">
+ <term>
+ <userinput>drop <replaceable>tunnel</replaceable></userinput>
+ </term>
+ <listitem>
+ <para>
+ This will cleanly disconnect the tunnel specified by
+ <replaceable>tunnel</replaceable> ID, as well as all
+ sessions on that tunnel.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-uptime" xreflabel="uptime">
+ <term><userinput>uptime</userinput></term>
+ <listitem>
+ <para>
+ This will show how long the <command>l2tpns</command>
+ process has been running, and the current bandwidth
+ utilization:
+
+<screen>
+17:10:35 up 8 days, 2212 users, load average: 0.21, 0.17, 0.16
+Bandwidth: UDP-ETH:6/6 ETH-UDP:13/13 TOTAL:37.6 IN:3033 OUT:2569
+</screen>
+
+ The bandwidth line contains 4 sets of values:
+
+ <informaltable>
+ <tgroup cols="2">
+ <tbody>
+ <row>
+ <entry>UDP-ETH</entry>
+ <entry>
+ The current bandwidth going from the LAC to
+ the ethernet (user uploads), in mbits/sec.
+ </entry>
+ </row>
+ <row>
+ <entry>ETH-UDP</entry>
+ <entry>
+ The current bandwidth going from ethernet to
+ the LAC (user downloads).
+ </entry>
+ </row>
+ <row>
+ <entry>TOTAL</entry>
+ <entry>The total aggregate bandwidth in mbits/s.</entry>
+ </row>
+ <row>
+ <entry>IN and OUT</entry>
+ <entry>
+ Packets/per-second going between UDP-ETH and
+ ETH-UDP.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+
+ These counters are updated every second.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-configure" xreflabel="configure">
+ <term><userinput>configure terminal</userinput></term>
+ <listitem>
+ <para>
+ Enter configuration mode. Use
+ <userinput>exit</userinput> or
+ <userinput>^Z</userinput> to exit this mode.
+ </para>
+
+ <para>
+ The following commands are valid in this mode:
+
+ <variablelist>
+ <varlistentry id="operation-cli-conf-load">
+ <term>
+ <userinput>load plugin
+ <replaceable>name</replaceable></userinput>
+ </term>
+ <listitem>
+ <para>
+ Load a plugin. You must specify the plugin
+ name, and it will search in
+ <filename>/usr/lib/l2tpns</filename> for
+ <filename><replaceable>name</replaceable>.so</filename>.
+ You can unload a loaded plugin with
+ <userinput>remove plugin
+ <replaceable>name</replaceable></userinput>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-conf-set">
+ <term><userinput>set</userinput> ...</term>
+ <listitem>
+ <para>
+ 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.
+ </para>
+
+ <para>
+ You can set any configuration value in this
+ way, although some may require a restart to
+ take effect. See <xref
+ linkend="config-startup"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-conf-router">
+ <term><userinput>router bgp</userinput> ...</term>
+ <listitem>
+ <para>
+ Configure BGP. See <xref
+ linkend="config-startup-bgp"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry id="operation-cli-conf-acl">
+ <term><userinput>ip access-list</userinput> ...</term>
+ <listitem>
+ <para>
+ Configure a named access list. See <xref
+ linkend="config-startup-acl"/>.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </sect2>
+
+ <sect2 id="operation-nsctl">
+ <title>nsctl</title>
+ <para>
+ <command>nsctl</command> sends messages to a running
+ <command>l2tpns</command> instance to be control plugins.
+ </para>
+
+ <para>
+ Arguments are <userinput>command</userinput> and optional
+ <replaceable>args</replaceable>. See
+ <literal>nsctl(8)</literal>.
+ </para>
+
+ <para>
+ Built-in command are <userinput>load_plugin</userinput>,
+ <userinput>unload_plugin</userinput> and
+ <userinput>help</userinput>. Any other commands are passed to
+ plugins for processing by the
+ <literal>plugin_control</literal> function.
+ </para>
+ </sect2>
+
+ <sect2 id="operation-signals">
+ <title>Signals</title>
+ <para>
+ While the process is running, you can send it a few different
+ signals, using the <command>kill</command> command.
+
+<screen>
+killall -HUP l2tpns
+</screen>
+
+ The signals understood are:
+
+ <variablelist>
+ <varlistentry>
+ <term>SIGHUP</term>
+ <listitem>
+ <para>Reload the config from disk and re-open log file.</para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGTERM</term>
+ <term>SIGINT</term>
+ <listitem>
+ <para>
+ Stop process. Tunnels and sessions are not
+ terminated. This signal should be used to stop
+ <command>l2tpns</command> on a cluster node where
+ there are other machines to continue handling traffic.
+ See <xref linkend="clustering"/>
+ </para>
+ </listitem>
+ </varlistentry>
+
+ <varlistentry>
+ <term>SIGQUIT</term>
+ <listitem>
+ <para>
+ Shut down tunnels and sessions, exit process when
+ complete.
+ </para>
+ </listitem>
+ </varlistentry>
+ </variablelist>
+ </para>
+ </sect2>
+ </sect1>
+
+ <sect1 id="throttling">
+ <title>Throttling</title>
+ <para>
+ <command>l2tpns</command> contains support for slowing down user
+ sessions to whatever speed you desire. The global setting
+ <literal>throttle_speed</literal> defines the default throttle
+ rate.
+ </para>
+
+ <para>
+ To throttle a sesion permanently, add a
+ <literal>Cisco-AVPair</literal> RADIUS attribute. The
+ <filename>autothrotle</filename> module interprets the following
+ attributes:
+
+ <informaltable>
+ <tgroup cols="2">
+ <tbody>
+ <row>
+ <entry><literal>throttle=yes</literal></entry>
+ <entry>
+ Throttle upstream/downstream traffic to the configured
+ <literal>throttle_speed</literal>.
+ </entry>
+ </row>
+
+ <row>
+ <entry>
+ <literal>throttle=<replaceable>rate</replaceable></literal>
+ </entry>
+ <entry>
+ Throttle upstream/downstream traffic to the specified
+ <replaceable>rate</replaceable> Kbps.
+ </entry>
+ </row>
+
+ <row>
+ <entry>
+ <literal>lcp:interface-config#1=service-policy input
+ <replaceable>rate</replaceable></literal>
+ </entry>
+
+ <entry morerows="1">
+ Alternate (Cisco) format: throttle
+ upstream/downstream to specified
+ <replaceable>rate</replaceable> Kbps.
+ </entry>
+ </row>
+
+ <row>
+ <entry>
+ <literal>lcp:interface-config#2=service-policy output
+ <replaceable>rate</replaceable></literal>
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+
+ <para>
+ You can also enable and disable throttling an active session
+ using the <xref linkend="operation-cli-throttle"/> CLI command.
+ </para>
+ </sect1>
+
+ <sect1 id="interception">
+ <title>Interception</title>
+ <para>
+ You may have to deal with legal requirements to be able to
+ intercept a user's traffic at any time.
+ <command>l2tpns</command> allows you to begin and end
+ interception on the fly, as well as at authentication time.
+ </para>
+
+ <para>
+ When a user is being intercepted, a copy of every packet they
+ send and receive will be sent wrapped in a UDP packet to a
+ specified host.
+ </para>
+
+ <para>
+ The UDP packet contains just the raw IP frame, with no extra
+ headers. The script <filename>scripts/l2tpns-capture</filename>
+ may be used as the end-point for such intercepts, writing the
+ data in PCAP format (suitable for inspection with
+ <command>tcpdump</command>).
+ </para>
+
+ <para>
+ To enable or disable interception of a connected user, use the
+ <xref linkend="operation-cli-snoop"/> and <userinput>no
+ snoop</userinput> CLI commands. These will enable interception
+ immediately.
+ </para>
+
+ <para>
+ 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
+ <literal>Cisco-AVPair="intercept=<replaceable>ip</replaceable>:<replaceable>port</replaceable>"</literal>.
+ For this feature to be enabled, you need to have the
+ <filename>autosnoop</filename> module loaded.
+ </para>
+ </sect1>
+
+ <sect1 id="plugins">
+ <title>Plugins</title>
+ <para>
+ So as to make <command>l2tpns</command> as flexible as possible,
+ a plugin API is include which you can use to hook into certain
+ events.
+ </para>
+
+ <para>
+ There are a some standard modules included which may be used as
+ examples: <filename>autosnoop</filename>,
+ <filename>autothrottle</filename>, <filename>garden</filename>,
+ <filename>sessionctl</filename>,
+ <filename>setrxspeed</filename>, <filename>snoopctl</filename>,
+ <filename>stripdomain</filename> and
+ <filename>throttlectl</filename>.
+ </para>
+
+ <para>
+ When an event occurs that has a hook, <command>l2tpns</command>
+ looks for a predefined function name in every loaded module, and
+ runs them in the order the modules were loaded.
+ </para>
+
+ <para>
+ The function should return <code>PLUGIN_RET_OK</code> if it is
+ all OK. If it returns <code>PLUGIN_RET_STOP</code>, then it is
+ assumed to have worked, but that no further modules should be
+ run for this event.
+ </para>
+
+ <para>
+ A return of <code>PLUGIN_RET_ERROR</code> means that this module
+ failed, and no further processing should be done for this event.
+ <note><para>Use this with care.</para></note>
+ </para>
+
+ <para>
+ Most event functions take a specific structure named
+ <code>param_<replaceable>event</replaceable></code>, which
+ varies in content with each event. The function name for each
+ event will be
+ <code>plugin_<replaceable>event</replaceable></code>, so for the
+ event <replaceable>timer</replaceable>, the function declaration
+ should look like:
+
+<programlisting>
+int plugin_timer(struct param_timer *data);
+</programlisting>
+
+ A list of the available events follows, with a list of all the
+ fields in the supplied structure:
+
+ <informaltable>
+ <tgroup cols="4">
+ <colspec colname="event"/>
+ <colspec colname="event_desc"/>
+ <colspec colname="member"/>
+ <colspec colname="member_desc"/>
+ <spanspec spanname="args" namest="member" nameend="member_desc"/>
+ <thead>
+ <row>
+ <entry>Event</entry>
+ <entry>Description</entry>
+ <entry spanname="args">Arguments</entry>
+ </row>
+ </thead>
+
+ <tbody>
+ <row>
+ <entry morerows="1"><code>plugin_init</code></entry>
+ <entry morerows="1">
+ <para>
+ Called when the plugin is loaded. A pointer to a
+ struct containing function pointers is passed as the
+ only argument, allowing the plugin to call back into
+ the main code.
+ </para>
+ <para>
+ Prior to loading the plugin, <command>l2tpns</command>
+ checks the API version the plugin was compiled
+ against. All plugins should contain:
+<programlisting>
+int plugin_api_version = PLUGIN_API_VERSION;
+</programlisting>
+ </para>
+ </entry>
+ <entry spanname="args"><code>struct pluginfuncs *</code></entry>
+ </row>
+ <row>
+ <entry spanname="args">
+ See <code>pluginfuncs</code> structure in
+ <code>plugin.h</code> for available functions.
+ </entry>
+ </row>
+
+ <row>
+ <entry morerows="1"><code>plugin_done</code></entry>
+ <entry morerows="1">
+ Called when the plugin is unloaded or
+ <command>l2tpns</command> is shutdown.
+ </entry>
+ <entry spanname="args"><code>void</code></entry>
+ </row>
+ <row>
+ <entry spanname="args">No arguments.</entry>
+ </row>
+
+ <row>
+ <entry morerows="6"><code>plugin_pre_auth</code></entry>
+ <entry morerows="6">
+ 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 some way.
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_pre_auth *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+ <row>
+ <entry><code>char *username</code></entry>
+ <entry>User name.</entry>
+ </row>
+ <row>
+ <entry><code>char *password</code></entry>
+ <entry>Password.</entry>
+ </row>
+ <row>
+ <entry><code>int protocol</code></entry>
+ <entry>
+ Authentication protocol: <literal>0xC023</literal> for PAP,
+ <literal>0xC223</literal> for CHAP.
+ </entry>
+ </row>
+ <row>
+ <entry><code>int continue_auth</code></entry>
+ <entry>Set to 0 to stop processing authentication modules.</entry>
+ </row>
+
+ <row>
+ <entry morerows="5"><code>plugin_post_auth</code></entry>
+ <entry morerows="5">
+ Called after a RADIUS response has been received, and
+ the basic checks have been performed. This is what
+ the <filename>garden</filename> module uses to force
+ authentication to be accepted.
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_post_auth *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+ <row>
+ <entry><code>char *username</code></entry>
+ <entry>User name.</entry>
+ </row>
+ <row>
+ <entry><code>short auth_allowed</code></entry>
+ <entry>
+ Initially true or false depending on whether
+ authentication has been allowed so far. You can
+ set this to 1 or 0 to force authentication to be
+ accepted or rejected.
+ </entry>
+ </row>
+ <row>
+ <entry><code>int protocol</code></entry>
+ <entry>
+ Authentication protocol: <literal>0xC023</literal> for PAP,
+ <literal>0xC223</literal> for CHAP.
+ </entry>
+ </row>
+
+ <row>
+ <entry morerows="1"><code>plugin_timer</code></entry>
+ <entry morerows="1">
+ Run once per second.
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_timer *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>time_t time_now</code></entry>
+ <entry>The current unix timestamp.</entry>
+ </row>
+
+ <row>
+ <entry morerows="2"><code>plugin_new_session</code></entry>
+ <entry morerows="2">
+ Called after a session is fully set up. The session
+ is now ready to handle traffic.
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_new_session *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+
+ <row>
+ <entry morerows="2"><code>plugin_kill_session</code></entry>
+ <entry morerows="2">
+ Called when a session is about to be shut down. This
+ may be called multiple times for the same session.
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_kill_session *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+
+ <row>
+ <entry morerows="5"><code>plugin_control</code></entry>
+ <entry morerows="5">
+ <para>
+ Called in whenever a <command>nsctl</command> packet
+ is received. This should handle the packet and form a
+ response if required.
+ </para>
+ <para>
+ Plugin-specific help strings may be included in the
+ output of <userinput>nsctl help</userinput> by
+ defining a <code>NULL</code> terminated list of
+ strings as follows:
+<programlisting>
+char *plugin_control_help[] = { <replaceable>...</replaceable>, NULL };
+</programlisting>
+ </para>
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_control *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>int iam_master</code></entry>
+ <entry>If true, this node is the cluster master.</entry>
+ </row>
+ <row>
+ <entry><code>int argc</code></entry>
+ <entry morerows="1"><command>nsctl</command> arguments.</entry>
+ </row>
+ <row>
+ <entry><code>char **argc</code></entry>
+ </row>
+ <row>
+ <entry><code>int reponse</code></entry>
+ <entry>
+ Response from control message (if handled): should be
+ either <code>NSCTL_RES_OK</code> or
+ <code>NSCTL_RES_ERR</code>.
+ </entry>
+ </row>
+ <row>
+ <entry><code>char *additional</code></entry>
+ <entry>
+ Additional information, output by
+ <command>nsctl</command> on receiving the response.
+ </entry>
+ </row>
+
+ <row>
+ <entry morerows="4"><code>plugin_radius_response</code></entry>
+ <entry morerows="4">
+ Called whenever a RADIUS response includes a
+ <literal>Cisco-AVPair</literal> value. The value is
+ split into
+ <replaceable>key</replaceable><literal>=</literal><replaceable>value</replaceable>
+ pairs. Will be called once for each pair in the
+ response.
+ </entry>
+ <entry spanname="args">
+ <code>struct plugin param_radius_response *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+ <row>
+ <entry><code>char *key</code></entry>
+ <entry morerows="1">Key and value.</entry>
+ </row>
+ <row>
+ <entry><code>char *value</code></entry>
+ </row>
+
+ <row>
+ <entry morerows="2"><code>plugin_radius_reset</code></entry>
+ <entry morerows="2">
+ Called whenever a RADIUS CoA request is received to
+ reset any options to default values before the new
+ values are applied.
+ </entry>
+ <entry spanname="args">
+ <code>struct param_radius_reset *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+
+ <row>
+ <entry morerows="3"><code>plugin_radius_account</code></entry>
+ <entry morerows="3">
+ Called when preparing a RADIUS accounting record to
+ allow additional data to be added to the packet.
+ </entry>
+ <entry spanname="args">
+ <code>struct param_radius_account *</code>
+ </entry>
+ </row>
+ <row>
+ <entry><code>tunnelt *t</code></entry>
+ <entry>Tunnel.</entry>
+ </row>
+ <row>
+ <entry><code>sessiont *s</code></entry>
+ <entry>Session.</entry>
+ </row>
+ <row>
+ <entry><code>uint8_t **packet</code></entry>
+ <entry>
+ Pointer to the end of the currently assembled
+ packet buffer. The value should be incremented by the
+ length of any data added.
+ </entry>
+ </row>
+
+ <row>
+ <entry morerows="1"><code>plugin_become_master</code></entry>
+ <entry morerows="1">
+ Called when a node elects itself cluster master.
+ </entry>
+ <entry spanname="args"><code>void</code></entry>
+ </row>
+ <row>
+ <entry spanname="args">No arguments.</entry>
+ </row>
+
+ <row>
+ <entry morerows="1"><code>plugin_new_session_master</code></entry>
+ <entry morerows="1">
+ Called once for each open session on becoming cluster
+ master.
+ </entry>
+ <entry spanname="args"><code>sessiont *</code></entry>
+ </row>
+ <row>
+ <entry spanname="args">
+ Session.
+ </entry>
+ </row>
+ </tbody>
+ </tgroup>
+ </informaltable>
+ </para>
+ </sect1>
+
+ <sect1 id="walled-garden">
+ <title>Walled Garden</title>
+ <para>
+ A "Walled Garden" is implemented so that you can provide perhaps
+ limited service to sessions that incorrectly authenticate.
+ </para>
+
+ <para>
+ Whenever a session provides incorrect authentication, and the
+ RADIUS server responds with Auth-Reject, the walled garden
+ module (if loaded) will force authentication to succeed, but set
+ the <literal>walled_garden</literal> flag in the session
+ structure, and adds an <command>iptables</command> rule to the
+ <literal>garden_users</literal> chain to cause all packets for
+ the session to traverse the <literal>garden</literal> chain.
+ </para>
+
+ <para>
+ This doesn't <emphasis>just work</emphasis>. To set this all
+ up, you will to setup the <literal>garden</literal> nat table
+ with the <xref linkend="config-build-garden"/> script with rules
+ to limit user's traffic.
+ </para>
+
+ <para>
+ For example, to force all traffic except DNS to be forwarded to
+ 192.168.1.1, add these entries to your
+ <filename>build-garden</filename> script:
+
+<programlisting>
+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
+</programlisting>
+ </para>
+
+ <para>
+ <command>l2tpns</command> will add entries to the
+ <literal>garden_users</literal> chain as appropriate.
+ </para>
+
+ <para>
+ You can check the amount of traffic being captured using the
+ following command:
+
+<screen>
+iptables -t nat -L garden -nvx
+</screen>
+ </para>
+ </sect1>
+
+ <sect1 id="filtering">
+ <title>Filtering</title>
+ <para>
+ Sessions may be filtered by specifying
+ <literal>Filter-Id</literal> attributes in the RADIUS reply.
+ <replaceable>filter</replaceable>.<literal>in</literal>
+ specifies that the named access-list
+ <replaceable>filter</replaceable> should be applied to traffic
+ from the customer,
+ <replaceable>filter</replaceable>.<literal>out</literal>
+ specifies a list for traffic to the customer.
+ </para>
+ </sect1>
+
+ <sect1 id="clustering">
+ <title>Clustering</title>
+ <para>
+ An <command>l2tpns</command> cluster consists of one* or more
+ servers configured with the same configuration, notably the
+ multicast <literal>cluster_address</literal>.
+ </para>
+
+ <para>*A stand-alone server is simply a degraded cluster.</para>
+
+ <para>
+ Initially servers come up as cluster slaves, and periodically
+ (every <literal>cluster_hb_interval</literal>/10 seconds) send
+ out ping packets containing the start time of the process to the
+ multicast <literal>cluster_address</literal>.
+ </para>
+
+ <para>
+ A cluster master sends heartbeat rather than ping packets, which
+ contain those session and tunnel changes since the last
+ heartbeat.
+ </para>
+
+ <para>
+ When a slave has not seen a heartbeat within
+ <literal>cluster_hb_timeout</literal>/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).
+ </para>
+
+ <para>
+ 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 <xref
+ linkend="routing"/>) for the <literal>bind_address</literal> and
+ for all addresses/networks in <filename>ip_pool</filename>.
+ </para>
+
+ <para>
+ 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.
+ </para>
+
+ <para>
+ The 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.
+ </para>
+
+ <para>*Configurable with <literal>cluster_master_min_adv</literal></para>
+ </sect1>
+
+ <sect1 id="routing">
+ <title>Routing</title>
+ <para>
+ If you are running a single instance, you may simply statically
+ route the IP pools to the <literal>bind_address</literal>
+ (<command>l2tpns</command> will send a gratuitous arp).
+ </para>
+
+ <para>
+ For a cluster, configure the members as BGP neighbours on your
+ router and configure multi-path load-balancing. Cisco uses
+ <userinput>maximum-paths ibgp</userinput> for IBGP. If this is
+ not supported by your IOS revision, you can use
+ <userinput>maximum-paths</userinput> (which works for EBGP) and
+ set <literal>as_number</literal> to a private value such as
+ 64512.
+ </para>
+ </sect1>
+</article>
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