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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
"http://www.w3.org/TR/html4/loose.dtd">
<HTML>
<HEAD>
<TITLE>L2TPNS Manual</TITLE>
<STYLE>
<STYLE TYPE="text/css">
H1 {
text-align: center;
}
@ -21,34 +24,55 @@ H3 {
<BODY>
<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>
<H2>Overview</H2>
L2TPNS is half of a complete L2TP implementation. It supports only the
</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="#Walled Garden">Walled Garden</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 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
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,
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
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>
@ -64,58 +88,35 @@ included.<P>
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>
<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
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
<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 will definately need to edit the configuration files before you
start. See the <A HREF="#Configuration">Configuration</A> 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>
<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
not detach to a daemon process, so you should perhaps run it from init.<P>
@ -123,19 +124,19 @@ 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
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
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
should be set by a line like:<P>
@ -157,7 +158,7 @@ highest. A rough description of the levels is:
<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>
</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
only ever be used for working out why it doesn't work at all.
@ -173,53 +174,42 @@ is any one of the syslog logging facilities, such as local5.
</LI>
<LI><B>l2tp_secret</B> (string)<BR>
This sets the string that L2TPNS will use for authenticating tunnel request.
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>
</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.
one will not be sent.
<P>
</LI>
<LI><B>secondary_dns</B> (ip address)<BR>
See <EM>primary_dns</EM>.
<P>
</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>
<LI><B>snoop_port</B> (int)<BR>
See <EM>snoop_host</EM>.
<P>
</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.
<LI><B>save_state</B> (boolean)<BR>
When l2tpns receives a STGTERM it will write out its current
ip_address_pool, session and tunnel tables to disk prior to exiting to
be re-loaded at startup. The validity of this data is obviously quite
short and the intent is to allow an sessions to be retained over a
software upgrade.
<P>
</LI>
<LI><B>primary_radius</B> (ip address)
<LI><B>secondary_radius</B> (ip address)<BR>
See <EM>primary_radius</EM>.
This 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.
<P>
</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.
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>
@ -230,18 +220,18 @@ radius queries will fail.
</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.
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.
<P>
</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.
<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.
<P>
</LI>
@ -252,10 +242,14 @@ the CLI, but changes will not affect currently connected users.
<P>
</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
the <EM>uptime</EM> command on the CLI.
<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.
<P>
</LI>
@ -265,49 +259,99 @@ doesn't work properly.
<P>
</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>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
the <EM>uptime</EM> command on the CLI.
<P>
</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.
<LI><B>cleanup_interval</B> (int)<BR>
Interval between regular cleanups (in seconds).
<P>
</LI>
<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.
<P>
</LI>
<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 SCHED_OTHER
(normal) process in favour of l2tpns when it becomes runnable.
Ignored on uniprocessor systems.
<P>
</LI>
<LI><B>lock_pages</B> (boolean)<BR>
Keep all pages mapped by the l2tpns process in memory.
<P>
</LI>
<LI><B>icmp_rate</B> (int)<BR>
Maximum number of host unreachable icmp packets to send per second.
<P>
</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.
<P>
</LI>
<LI><B>cluster_interface</B> (string)<BR>
Interface for cluster packets (default: eth0).
<P>
</LI>
<LI><B>cluster_hb_interval</B> (int)<BR>
Interval in tenths of a second between cluster heartbeat/pings.
<P>
</LI>
<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.
<P>
</LI>
<LI><B>as_number</B> (int)<BR>
Defines the local AS number for BGP (see <A HREF="#Routing">Routing</A>).
<P>
</LI>
<LI><B>bgp_peer1</B> (string)
<LI><B>bgp_peer1_as</B> (int)
<LI><B>bgp_peer2</B> (string)
<LI><B>bgp_peer2_as</B> (int)<BR>
<P>
DNS name (or IP) and AS number of BGP peers.
</LI>
</UL>
<H3>l2tpns.users</H3>
<H3 ID="users">users</H3>
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>
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>
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>
The username <B>enable</B> has a special meaning and is used to set
the enable password.<P>
<PRE>
user.1:randompassword
fred:bhPe4rD1ME8.s
bob:SP2RHKl3Q3qo6
</PRE>
<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>
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>
<H3 ID="ip-pool">ip_pool</H3>
<H3>l2tpns.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 IP mask
per line. e.g.:<P>
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>
192.168.1.1
@ -318,49 +362,70 @@ per line. e.g.:<P>
10.0.0.0/8
</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.
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>Controlling the process</H2>
<H3 ID="build-garden">build-garden</H3>
A running L2TPNS process can be controlled in a number of ways. The primary
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>
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>
<H2 ID="ControllingtheProcess">Controlling the Process</H2>
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>
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&gt;</PRE><P>
will be presented with a <I>hostname</I><B>&gt;</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>
@ -392,6 +457,12 @@ The columns listed in the overview are:
<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>
@ -458,27 +529,38 @@ 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>
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 <EM>Interception</EM>.
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>
@ -496,22 +578,8 @@ 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
@ -528,21 +596,43 @@ IN and OUT are packets/per-second going between UDP-ETH and ETH-UDP.
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>
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>
host is the address of the l2tpns server which you want to send the message
to.<P>
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.
<H3>Signals</H3>
<H3 ID="Signals">Signals</H3>
While the process is running, you can send it a few different signals, using
the kill command.
@ -552,25 +642,19 @@ killall -HUP l2tpns
The signals understood are:
<UL>
<LI>SIGHUP - Reload the config from disk<P></LI>
<LI>SIGHUP - Reload the config from disk and re-open log file<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>
</UL>
<H2>Throttling</H2>
<H2 ID="Throttling">Throttling</H2>
L2TPNS contains support for slowing down user sessions to whatever speed you
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>
@ -581,28 +665,10 @@ 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
@ -621,11 +687,11 @@ 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
request to L2TPNS.<P>
request to l2tpns.<P>
This request is sent to the radius server, which will hopefully respond with
Auth-Accept or Auth-Reject.<P>
@ -642,9 +708,9 @@ 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
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 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>
@ -658,16 +724,16 @@ contain:
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>
@ -828,7 +894,7 @@ supplied structure:
</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>
@ -840,24 +906,18 @@ radius server responds with Auth-Reject, the walled garden module
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:
@ -865,11 +925,54 @@ command:
iptables -t nat -L garden -nvx
</PRE>
<H2>Clustering</H2>
<H2 ID="Clustering">Clustering</H2>
Clustering is currently broken. But here's how it's supposed to work.<P>
An l2tpns cluster consists of of one* or more servers configured with
the same configuration, notably the multicast <B>cluster_address</B>.<P>
<H2>Performance</H2>
*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>
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 ID="Performance">Performance</H2>
Performance is great.<P>

2
INSTALL
View file

@ -2,7 +2,7 @@ Brief Installation guide for L2TPNS
1. Requirements
* libcli 1.7.0 or greater
* libcli 1.8.0 or greater
You can get it from http://sourceforge.net/projects/libcli.
* A kernel with iptables support.