tinc/doc/tinc.texi

\input texinfo   @c -*-texinfo-*-
@c $Id: tinc.texi,v 1.8.4.11 2001/01/06 20:02:21 guus Exp $
@c %**start of header
@setfilename tinc.info
@settitle tinc Manual
@setchapternewpage odd
@c %**end of header

@ifinfo
@direntry
* tinc: (tinc).              The tinc Manual.
@end direntry

This is the info manual for tinc, a Virtual Private Network daemon.

Copyright @copyright{} 1998,199,2000 Ivo Timmermans
<itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
Wessel Dankers <wsl@@nl.linux.org>.

$Id: tinc.texi,v 1.8.4.11 2001/01/06 20:02:21 guus Exp $

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

@end ifinfo

@titlepage
@title tinc Manual
@subtitle Setting up a Virtual Private Network with tinc
@author Ivo Timmermans and Guus Sliepen

@page
@vskip 0pt plus 1filll
@cindex copyright
Copyright @copyright{} 1998,1999,2000 Ivo Timmermans
<itimmermans@@bigfoot.com>, Guus Sliepen <guus@@sliepen.warande.net> and
Wessel Dankers <wsl@@nl.linux.org>.

$Id: tinc.texi,v 1.8.4.11 2001/01/06 20:02:21 guus Exp $

Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

Permission is granted to copy and distribute modified versions of this
manual under the conditions for verbatim copying, provided that the
entire resulting derived work is distributed under the terms of a
permission notice identical to this one.

@end titlepage

@c ==================================================================
@node Top, Introduction, (dir), (dir)

@menu
* Introduction::                Introduction
* Installing tinc - preparations::  
* Installing tinc - installation::  
* Configuring tinc::            
* Running tinc::                
* Technical information::       
* About us::                    
* Concept Index::               All used terms explained
@end menu


@contents

@c ==================================================================
@node    Introduction, Installing tinc - preparations, Top, Top
@chapter Introduction

@cindex tinc
tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
encryption to create a secure private network between hosts on the
Internet.

Because the tunnel appears to the IP level network code as a normal
network device, there is no need to adapt any existing software.

This tunneling allows VPN sites to share information with each other
over the Internet without exposing any information to others.

This document is the manual for tinc.  Included are chapters on how to
configure your computer to use tinc, as well as the configuration
process of tinc itself.

@menu
* VPNs::                        Virtual Private Networks in general
* tinc::                        about tinc
* Supported platforms::         
@end menu

@c ==================================================================
@node    VPNs, tinc, Introduction, Introduction
@section Virtual Private Networks

@cindex VPN
A Virtual Private Network or VPN is a network that can only be accessed
by a few elected computers that participate.  This goal is achievable in
more than just one way.

@cindex private
Private networks can consist of a single stand-alone ethernet LAN.  Or
even two computers hooked up using a null-modem cable.  In these cases,
it is
obvious that the network is @emph{private}, no one can access it from the
outside.  But if your computers are linked to the internet, the network
is not private anymore, unless one uses firewalls to block all private
traffic.  But then, there is no way to send private data to trusted
computers on the other end of the internet.

@cindex virtual
This problem can be solved by using @emph{virtual} networks.  Virtual
networks can live on top of other networks, but they use encapsulation to
keep using their private address space so they do not interfere with
each other.  Mostly, virtual networks appear like a singe LAN, even though
they can span the entire world.  But virtual networks can't be secured
by using firewalls, because the traffic that flows through it has to go
through the internet, where other people can look at it.

When one introduces encryption, we can form a true VPN.  Other people may
see encrypted traffic, but if they don't know how to decipher it (they
need to know the key for that), they cannot read the information that flows
through the VPN.  This is what tinc was made for.

@cindex virtual
tinc uses normal IP datagrams to encapsulate data that goes over the VPN
network link.  In this case it's also clear that the network is
@emph{virtual}, because no direct network link has to exist between to
participants.

As is the case with either type of VPN, anybody could eavesdrop.  Or
worse, alter data.  Hence it's probably advisable to encrypt the data
that flows over the network.


@c ==================================================================
@node    tinc, Supported platforms, VPNs, Introduction
@section tinc

@cindex vpnd
@cindex ethertap
I really don't quite remember what got us started, but it must have been
Guus' idea.  He wrote a simple implementation (about 50 lines of C) that
used the @emph{ethertap} device that Linux knows of since somewhere
about kernel 2.1.60.  It didn't work immediately and he improved it a
bit.  At this stage, the project was still simply called @samp{vpnd}.

Since then, a lot has changed---to say the least.

@cindex tincd
tinc now supports encryption, it consists of a single daemon (tincd) for
both the receiving and sending end, it has become largely
runtime-configurable---in short, it has become a full-fledged
professional package.

A lot can---and will be---changed. We have a number of things that we would like to
see in the future releases of tinc.  Not everything will be available in
the near future.  Our first objective is to make tinc work perfectly as
it stands, and then add more advanced features.

Meanwhile, we're always open-minded towards new ideas.  And we're
available too.


@c ==================================================================
@node    Supported platforms,  , tinc, Introduction
@section Supported platforms

tinc has been verified to work under Linux, FreeBSD and Solaris, with
various hardware architectures.  These are the three platforms
that are supported by the universial TUN/TAP device driver, so if
support for other operating systems is added to this driver, perhaps
tinc will run on them as well.  Without this driver, tinc will most
likely compile and run, but it will not be able to send or receive data
packets.

For an up to date list of supported platforms, please check the list on
our website:
@uref{http://tinc.nl.linux.org/platforms.html}.


@c ==================================================================
@subsection Linux

tinc was first written for Linux running on an intel x86 processor, so
this is the best supported platform.  The protocol however, and actually
anything about tinc, has been rewritten to support random byte ordering
and arbitrary word length.  So in theory it should run on other
processors that Linux runs on.  It has already been verified to run on
alpha and sparc processors as well.

tinc uses the ethertap device that is provided in the standard kernel
since version 2.1.60, so anything above that (2.2.x, 2.3.x, and 2.4.0)
kernel version is able to support tinc.


@c ==================================================================
@subsection FreeBSD

tinc on FreeBSD relies on the universial TUN/TAP driver for its data
acquisition from the kernel.  Therefore, tinc suports the same platforms
as this driver.  These are: FreeBSD 3.x, 4.x, 5.x.


@c ==================================================================
@subsection Solaris

tinc on Solaris relies on the universial TUN/TAP driver for its data
acquisition from the kernel.  Therefore, tinc suports the same platforms
as this driver.  These are: Solaris, 2.1.x.


@c
@c
@c
@c
@c
@c
@c       Preparing your system
@c
@c
@c
@c
@c

@c ==================================================================
@node    Installing tinc - preparations, Installing tinc - installation, Introduction, Top
@chapter Installing tinc: preparations

This chapter contains information on how to prepare your system to
support tinc.

@menu
* Configuring the kernel::      
* Libraries::                   
@end menu


@c ==================================================================
@node    Configuring the kernel, Libraries, Installing tinc - preparations, Installing tinc - preparations
@section Configuring the kernel

If you are running Linux, chances are good that your kernel already
supports all the devices that tinc needs for proper operation.  For
example, the standard kernel from Redhat Linux already has support for
ethertap and netlink compiled in.  Debian users can use the modconf
utility to select the modules.  If your Linux distribution supports this
method of selecting devices, look out for something called `ethertap',
and `netlink_dev'.  You need both these devices.

If you can install these devices in a similar manner, you may skip this
section.

@menu
* Configuration of the Linux kernel::  
* Configuration of the FreeBSD kernel::  
* Configuration of the Solaris kernel::  
@end menu


@c ==================================================================
@node       Configuration of the Linux kernel, Configuration of the FreeBSD kernel, Configuring the kernel, Configuring the kernel
@subsection Configuring the Linux kernel

Since this particular implementation only runs on 2.1 or higher Linux
kernels, you should grab one (2.2 is current at this time).  A 2.0 port
is not really possible, unless someone tells me someone ported the
ethertap and netlink devices back to 2.0.

If you are unfamiliar with the process of configuring and compiling a
new kernel, you should read the
@uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel
HOWTO} first.  Do that now!

Here are the options you have to turn on when configuring a new
kernel.

For kernel 2.2.x:

@example
Code maturity level options
[*] Prompt for development and/or incomplete code/drivers
Networking options
[*] Kernel/User netlink socket
<*> Netlink device emulation
Network device support
<*> Ethertap network tap
@end example

Note that if you want to run more than one instance of tinc or other
programs that use the ethertap, you have to compile the ethertap driver
as a module.

For kernel 2.3.x and 2.4.x:

@example
Code maturity level options
[*] Prompt for development and/or incomplete code/drivers
Networking options
[*] Kernel/User netlink socket
<*> Netlink device emulation
Network device support
<*> Universal TUN/TAP device driver support
@end example


Any other options not mentioned here are not relevant to tinc.  If you
decide to build any of these as dynamic kernel modules, it's a good idea
to add these lines to @file{/etc/modules.conf}.

@example
alias tap0 ethertap
alias char-major-36 netlink_dev
@end example

If you have a 2.4-pre kernel, you can choose both the TUN/TAP driver and
the `Ethertap network tap' device.  This latter is marked obsolete,
because the universal TUN/TAP driver is a newer implementation that is
supposed to be used in favour of ethertap.  For tinc, it doesn't really
matter which one you choose; based on the device file name, tinc will make
the right choice about what protocol to use. However, chances are that
although you can choose the obsolote ethertap driver, it will not function
at all. The TUN/TAP driver is the safe choice.

Finally, after having set up other options, build the kernel and boot
it.  Unfortunately it's not possible to insert these modules in a
running kernel.


@c ==================================================================
@node       Configuration of the FreeBSD kernel, Configuration of the Solaris kernel, Configuration of the Linux kernel, Configuring the kernel
@subsection Configuring the FreeBSD kernel

This section will contain information on how to configure your FreeBSD
kernel to support the universal TUN/TAP device.  For 5.0 and 4.1
systems, this is included in the kernel configuration, for earlier
systems (4.0 and 3.x), you need to install the universal TUN/TAP driver
yourself.

Unfortunately somebody still has to write the text.


@c ==================================================================
@node       Configuration of the Solaris kernel,  , Configuration of the FreeBSD kernel, Configuring the kernel
@subsection Configuring the Solaris kernel

This section will contain information on how to configure your Solaris
kernel to support the universal TUN/TAP device.  You need to install
this driver yourself.

Unfortunately somebody still has to write the text.


@c ==================================================================
@node    Libraries,  , Configuring the kernel, Installing tinc - preparations
@section Libraries

@cindex requirements
Before you can configure or build tinc, you need to have the OpenSSL
library installed on your system.  If you try to configure tinc without
having installed it, configure will give you an error message, and stop.

@menu
* OpenSSL::                     
@end menu


@c ==================================================================
@node       OpenSSL,  , Libraries, Libraries
@subsection OpenSSL

@cindex OpenSSL
For all cryptography-related functions, tinc uses the functions provided
by the OpenSSL library.  We recommend using version 0.9.5 or 0.9.6 of
this library.  Other versions may also work, but we can guarantee
nothing.

If this library is not installed, you wil get an error when configuring
tinc for build.  Support for running tinc without having OpenSSL
installed @emph{may} be added in the future.

You can use your operating system's package manager to install this if
available.  Make sure you install the development AND runtime versions
of this package.

If you have to install OpenSSL manually, you can get the source code
from @url{http://www.openssl.org/}.  Instructions on how to configure,
build and install this package are included within the package.  Please
make sure you build development and runtime libraries (which is the
default).

If you installed the OpenSSL libraries from source, it may be necessary
to let configure know where they are, by passing configure one of the
--with-openssl-* parameters.

@example
--with-openssl=DIR      OpenSSL library and headers prefix
--with-openssl-include=DIR OpenSSL headers directory
                        (Default is OPENSSL_DIR/include)
--with-openssl-lib=DIR  OpenSSL library directory
                        (Default is OPENSSL_DIR/lib)
@end example


@subsubheading License

Since the license under which OpenSSL is distributed is not directly
compatible with the terms of the GNU GPL
@uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we
include an addition to the GPL (see also the file COPYING.README):

@quotation
This program is released under the GPL with the additional exemption
that compiling, linking, and/or using OpenSSL is allowed.  You may
provide binary packages linked to the OpenSSL libraries, provided that
all other requirements of the GPL are met.
@end quotation


@c
@c
@c
@c      Installing tinc
@c
@c
@c
@c

@c ==================================================================
@node    Installing tinc - installation, Configuring tinc, Installing tinc - preparations, Top
@chapter Installing tinc: installation

If you use Redhat or Debian, you may want to install one of the
precompiled packages for your system.  These packages are equipped with
system startup scripts and sample configurations.

If you don't run either of these systems, or you want to compile tinc
for yourself, you can use the source.  The source is distributed under
the GNU General Public License (GPL).  Download the source from the
@uref{http://tinc.nl.linux.org/download.html, download page}, which has
the checksums of these files listed; you may wish to check these with
md5sum before continuing.

tinc comes in a convenient autoconf/automake package, which you can just
treat the same as any other package.  Which is just untar it, type
`configure' and then `make'.

More detailed instructions are in the file @file{INSTALL}, which is
included in the source distribution.

@menu
* Building tinc::               
* System files::                
* Interfaces::                  
@end menu


@c ==================================================================
@node    Building tinc, System files, Installing tinc - installation, Installing tinc - installation
@section Building tinc

Detailed instructions on configuring the source and building tinc can be
found in the file called @file{INSTALL}.


@c ==================================================================
@node    System files, Interfaces, Building tinc, Installing tinc - installation
@section System files

Before you can run tinc, you must make sure you have all the needed
files on your system.

@menu
* Device files::                
* Other files::                 
@end menu


@c ==================================================================
@node       Device files, Other files, System files, System files
@subsection Device files

First, you'll need the special device file(s) that form the interface
between the kernel and the daemon.

The permissions for these files have to be such that only the super user
may read/write to this file.  You'd want this, because otherwise
eavesdropping would become a bit too easy.  This does, however, imply
that you'd have to run tincd as root.

If you use the universal TUN/TAP driver, you have to create the
following device files (unless they already exist):

@example
mknod -m 600 /dev/... c .. ..
chown 0.0 /dev/...
@end example

If you want to have more devices, the device numbers will be .. .. ...

If you use Linux, and you run the new 2.4 kernel using the devfs
filesystem, then the tap device will be automatically generated as
@file{/dev/netlink/tap0}.

If you use Linux and have kernel 2.2.x, you have to make the ethertap
devices:

@example
mknod -m 600 /dev/tap0 c 36 16
chown 0.0 /dev/tap0
@end example

Any further ethertap devices have minor device number 16 through 31.


@c ==================================================================
@node       Other files,  , Device files, System files
@subsection Other files

@subsubheading @file{/etc/networks}

You may add a line to @file{/etc/networks} so that your VPN will get a
symbolic name.  For example:

@example
myvpn 10.0.0.0
@end example

This has nothing to do with the MyVPNIP configuration variable that will be
discussed later, it is only to make the output of the route command more
legible.

@subsubheading @file{/etc/services}

You may add this line to @file{/etc/services}.  The effect is that you
may supply a @samp{tinc} as a valid port number to some programs.  The
number 655 is registered with the IANA.

@example
tinc            655/tcp    TINC
tinc            655/udp    TINC
#                          Ivo Timmermans <itimmermans@@bigfoot.com>
@end example


@c ==================================================================
@node    Interfaces,  , System files, Installing tinc - installation
@section Interfaces

Before you can start transmitting data over the tinc tunnel, you must
set up the ethertap network devices.

First, decide which IP addresses you want to have associated with these
devices, and what network mask they must have.  You also need these
numbers when you are going to configure tinc itself.  @xref{Configuring
tinc}.

It doesn't matter much which part you do first, setting up the network
devices or configure tinc.  But they both have to be done before you try
to start a tincd.

The actual setup of the ethertap device is quite simple, just repeat
after me:

@example
ifconfig tap@emph{n} hw ether fe:fd:00:00:00:00
@end example

@cindex MAC address
@cindex hardware address
@strong{Note:} Since version 1.0pre3, all interface addresses are set to
this address, whereas previous versions required the MAC to match the
actual IP address.

@cindex ifconfig
To activate the device, you have to assign an IP address to it.  To set
an IP address @emph{IP} with network mask @emph{mask}, do the following:

@example
ifconfig tap@emph{n} @emph{xx}.@emph{xx}.@emph{xx}.@emph{xx} netmask @emph{mask}
@end example

@cindex netmask
The netmask is the mask of the @emph{entire} VPN network, not just your
own subnet.  It is the same netmask you will have to specify with the
VpnMask configuration variable.


@c
@c
@c
@c
@c         Configuring tinc
@c
@c
@c
@c


@c ==================================================================
@node    Configuring tinc, Running tinc, Installing tinc - installation, Top
@chapter Configuring tinc

@menu
* Multiple networks::           
* How connections work::        
* Configuration file::          
* Example::                     
@end menu

@c ==================================================================
@node    Multiple networks, How connections work, Configuring tinc, Configuring tinc
@section Multiple networks

@c from the manpage

It is perfectly OK for you to run more than one tinc daemon.
However, in its default form, you will soon notice that you can't use
two different configuration files without the -c option.

We have thought of another way of dealing with this: network names.  This
means that you call tincd with the -n argument, which will assign a name
to this daemon.

The effect of this is that the daemon will set its configuration
``root'' to /etc/tinc/nn/, where nn is your argument to the -n
option.  You'll notice that it appears in syslog as ``tinc.nn''.

However, it is not strictly necessary that you call tinc with the -n
option.  In this case, the network name would just be empty, and it will
be used as such.  tinc now looks for files in /etc/tinc/, instead of
/etc/tinc/nn/; the configuration file should be /etc/tinc/tinc.conf,
and the passphrases are now expected to be in /etc/tinc/passphrases/.

But it is highly recommended that you use this feature of tinc, because
it will be so much clearer whom your daemon talks to.  Hence, we will
assume that you use it.


@c ==================================================================
@node    How connections work, Configuration file, Multiple networks, Configuring tinc
@section How connections work

Before going on, first a bit on how tinc sees connections.

When tinc starts up, it reads in the configuration file and parses the
command-line options.  If it sees a `ConnectTo' value in the file, it
will try to connect to it, on the given port.  If this fails, tinc exits.


@c ==================================================================
@node    Configuration file, Example, How connections work, Configuring tinc
@section Configuration file

The actual configuration of the daemon is done in the file
@file{/etc/tinc/nn/tinc.conf}.

This file consists of comments (lines started with a #) or assignments
in the form of

@example
Variable = Value.
@end example

The variable names are case insensitive, and any spaces, tabs, newlines
and carriage returns are ignored.  Note: it is not required that you put
in the `=' sign, but doing so improves readability.  If you leave it
out, remember to replace it with at least one space character.

In this section all valid variables are listed in alphabetical order.
The default value is given between parentheses; required directives are
given in @strong{bold}.

@menu
* Main configuration variables::  
* Host configuration variables::  
* How to configure::            
@end menu


@c ==================================================================
@node    Main configuration variables, Host configuration variables, Configuration file, Configuration file
@subsection Main configuration variables

@table @asis
@item @strong{ConnectTo = <name>}
Specifies which host to connect to on startup.  Multiple ConnectTo
variables may be specified, if connecting to the first one fails then
tinc will try the next one, and so on.  It is possible to specify
hostnames for dynamic IP addresses (like those given on dyndns.org),
tinc will not cache the resolved IP address.

If you don't specify a host with ConnectTo, regardless of whether a
value for ConnectPort is given, tinc won't connect at all, and will
instead just listen for incoming connections.

@item Hostnames = <yes|no> (no)
This option selects whether IP addresses (both real and on the VPN)
should be resolved.  Since DNS lookups are blocking, it might affect
tinc's efficiency, even stopping the daemon for a few seconds everytime
it does a lookup if your DNS server is not responding.

This does not affect resolving hostnames to IP addresses from the
configuration file.

@item Interface = <device>
If you have more than one network interface in your computer, tinc will
by default listen on all of them for incoming connections.  It is
possible to bind tinc to a single interface like eth0 or ppp0 with this
variable.

@item InterfaceIP = <local address>
If your computer has more than one IP address on a single interface (for
example if you are running virtual hosts), tinc will by default listen
on all of them for incoming connections.  It is possible to bind tinc to
a single IP address with this variable.  It is still possible to listen
on several interfaces at the same time though, if they share the same IP
address.

@item KeyExpire = <seconds> (3600)
This option controls the time the encryption keys used to encrypt the
data are valid.  It is common practice to change keys at regular
intervals to make it even harder for crackers, even though it is thought
to be nearly impossible to crack a single key.

@item @strong{Name = <name>}
This is a symbolic name for this connection.  It can be anything 

@item PingTimeout = <seconds> (5)
The number of seconds of inactivity that tinc will wait before sending a
probe to the other end.  If that other end doesn't answer within that
same amount of seconds, the connection is terminated, and the others
will be notified of this.

@item PrivateKey = <key>
This is the RSA private key for tinc. However, for safety reasons it is
advised to store private keys of any kind in separate files. This prevents
accidental eavesdropping if you are editting the configuration file.

@item PrivateKeyFile = <path>
This is the full path name of the RSA private key file that was
generated by ``tincd --generate-keys''.  It must be a full path, not a
relative directory.

Note that exactly @strong{one of the above two options} must be specified.

@item TapDevice = <device> (/dev/tap0)
The ethertap device to use.  Note that you can only use one device per
daemon.  The info pages of the tinc package contain more information
about configuring an ethertap device for Linux.

@item VpnMask = <mask>
The mask that defines the scope of the entire VPN.  This option is not
used by the tinc daemon itself, but can be used by startup scripts to
configure the ethertap devices correctly.
@end table


@c ==================================================================
@node    Host configuration variables, How to configure, Main configuration variables, Configuration file
@subsection Host configuration variables

@table @asis
@item @strong{Address = <IP address|hostname>}
This variable is only required if you want to connect to this host.  It
must resolve to the external IP address where the host can be reached,
not the one that is internal to the VPN.

@item IndirectData = <yes|no> (no)
This option specifies whether other tinc daemons besides the one you
specified with ConnectTo can make a direct connection to you.  This is
especially useful if you are behind a firewall and it is impossible to
make a connection from the outside to your tinc daemon.  Otherwise, it
is best to leave this option out or set it to no.

@item Port = <port> (655)
Connect to the upstream host (given with the ConnectTo directive) on
port port.  port may be given in decimal (default), octal (when preceded
by a single zero) o hexadecimal (prefixed with 0x).  port is the port
number for both the UDP and the TCP (meta) connections.

@item PublicKey = <key>
This is the RSA public key for this host.

@item PublicKeyFile = <path>
This is the full path name of the RSA public key file that was generated
by ``tincd --generate-keys''.  It must be a full path, not a relative
directory.

Note that exactly @strong{one of the above two options} must be specified
in each host configuration file, if you want to be able to establish a
connection with that host.

@item Subnet = <IP address/maskbits>
This is the subnet range of all IP addresses that will be accepted by
the host that defines it.

The range must be contained in the IP address range of the tap device,
not the real IP address of the host running tincd.

maskbits is the number of bits set to 1 in the netmask part; for
example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
/22. This conforms to standard CIDR notation as described in
@uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}

@item TCPonly = <yes|no> (no)
If this variable is set to yes, then the packets are tunnelled over a
TCP connection instead of a UDP connection.  This is especially useful
for those who want to run a tinc daemon from behind a masquerading
firewall, or if UDP packet routing is disabled somehow.  @emph{This is
experimental code, try this at your own risk. It may not work at all.}
@end table


@c ==================================================================
@node    How to configure,  , Host configuration variables, Configuration file
@subsection How to configure

@subsubheading Step 1.  Creating the key files

For each host, you have to create a pair of RSA keys.  One key is your
private key, which is only known to you.  The other one is the public
key, which you should copy to all hosts wanting to authenticate to you.


@subsubheading Step 2.  Configuring each host

For every host in the VPN, you have to create two files.  First there is
the main configuration file, @file{/etc/tinc/vpn-name/tinc.conf}.  In
this file there should at least be three directives:

@table @samp
@item Name
You should fill in the name of this host (or rather, the name of this
leaf of the VPN).  It can be called after the hostname, the physical
location, the department, or the name of one of your boss' pets.  It can
be anything, as long as all these names are unique across the entire
VPN.

@item PrivateKey
Fill in the full pathname to the file that contains the private RSA key.

@item ConnectTo
This is the name of the host that you want to connect to (not a DNS
name, rather the name that is given with the Name parameter in that
hosts tinc.conf).  This is the upstream connection.  If your computer is
a central node, you might want to leave this out to make it stay idle
until someone connects to it.
@end table

@cindex host configuration file
Then you should create a file with the name you gave yourself in
tinc.conf (the `Name' parameter), located in
@file{/etc/tinc/vpn-name/hosts/}.  In this file, which we call the
`@emph{host configuration file}', only one variable is required:

@table @samp
@item Subnet
The IP range that this host accepts as being `local'.  All packets with
a destination address that is within this subnet will be sent to us.
@end table


@subsubheading Step 3.  Bringing it all together

Now for all hosts that you want to create a direct connection to, -- you
connect to them or they connect to you -- you get a copy of their host
configuration file and their public RSA key.

For each host configuration file, you add two variables:

@table @samp
@item Address
Enter the IP address or DNS hostname for this host.  This is only needed
if you connect to this host.

@item PublicKey
Put the full pathname to this hosts public RSA key here.
@end table

When you did this, you should be ready to create your first connection.
Pay attention to the system log, most errors will only be visible
there.  If you get an error, you can check @ref{Error messages}.


@c ==================================================================
@node    Example,  , Configuration file, Configuring tinc
@section Example


@cindex example
Imagine the following situation.  An A-based company wants to connect
three branch offices in B, C and D using the internet.  All four offices
have a 24/7 connection to the internet.

A is going to serve as the center of the network.  B and C will connect
to A, and D will connect to C.  Each office will be assigned their own IP
network, 10.x.0.0.

@example
A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
@end example

``gateway'' is the VPN IP address of the machine that is running the
tincd.  ``internet IP'' is the IP address of the firewall, which does not
need to run tincd, but it must do a port forwarding of TCP&UDP on port
655 (unless otherwise configured).

In this example, it is assumed that eth0 is the interface that points to
the inner (physical) LAN of the office, although this could also be the
same as the interface that leads to the internet.  The configuration of
the real interface is also shown as a comment, to give you an idea of
how these example host is set up.

@subsubheading For A

@emph{A} would be configured like this:

@example
#ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
ifconfig tap0 hw ether fe:fd:00:00:00:00
ifconfig tap0 10.1.54.1 netmask 255.0.0.0
@end example

and in /etc/tinc/tinc.conf:

@example
Name = A
PrivateKey = /etc/tinc/A.priv
VpnMask = 255.0.0.0
@end example

On all hosts, /etc/tinc/hosts/A contains:

@example
Subnet = 10.1.0.0/16
Address = 1.2.3.4
PublicKey = /etc/tinc/hosts/A.pub
@end example


@subsubheading For B

@example
#ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
ifconfig tap0 hw ether fe:fd:00:00:00:00
ifconfig tap0 10.2.1.12 netmask 255.0.0.0
@end example

and in /etc/tinc/tinc.conf:

@example
Name = B
ConnectTo = A
PrivateKey = /etc/tinc/B.priv
VpnMask = 255.0.0.0
@end example

Note here that the internal address (on eth0) doesn't have to be the
same as on the tap0 device.  Also, ConnectTo is given so that no-one can
connect to this node.

On all hosts, /etc/tinc/hosts/B:

@example
Subnet = 10.2.0.0/16
Address = 2.3.4.5
PublicKey = /etc/tinc/hosts/B.pub
@end example


@subsubheading For C

@example
#ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
ifconfig tap0 hw ether fe:fd:00:00:00:00
ifconfig tap0 10.3.69.254 netmask 255.0.0.0
@end example

and in /etc/tinc/A/tinc.conf:

@example
Name = C
ConnectTo = A
TapDevice = /dev/tap1
VpnMask = 255.0.0.0
@end example

C already has another daemon that runs on port 655, so they have to
reserve another port for tinc.  It can connect to other tinc daemons on
the regular port though, so no ConnectPort variable is needed.  They
also use the netname to distinguish between the two.  tinc is started
with `tincd -n A'.

On all hosts, /etc/tinc/hosts/C:

@example
Subnet = 10.3.0.0/16
Port = 2000
PublicKey = /etc/tinc/hosts/C.pub
@end example


@subsubheading For D

@example
#ifconfig tap0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
ifconfig tap0 hw ether fe:fd:0a:04:03:20
ifconfig tap0 10.4.3.32 netmask 255.0.0.0
@end example

and in /etc/tinc/tinc.conf:

@example
MyVirtualIP = 10.4.3.32/16
ConnectTo = 3.4.5.6
ConnectPort = 2000
VpnMask=255.0.0.0
@end example

D will be connecting to C, which has a tincd running for this network on
port 2000.  Hence they need to put in a ConnectPort, but it doesn't need
to have a different ListenPort.

@subsubheading Key files

A, B, C and D all have generate a public key with tincd -K, the output is
stored in /etc/tinc/hosts/X.pub (where X is A, B or D), except for C,
who stored it in /etc/tinc/A/hosts/C.pub.

A stores a copy of B's public key in /etc/tinc/hosts/B.pub

A stores a copy of C's public key in /etc/tinc/hosts/C.pub

B stores a copy of A's public key in /etc/tinc/hosts/A.pub

C stores a copy of A's public key in /etc/tinc/A/hosts/A.pub

C stores a copy of D's public key in /etc/tinc/A/hosts/D.pub

D stores a copy of C's public key in /etc/tinc/hosts/C.pub

@subsubheading Starting

A has to start their tincd first.  Then come B and C, where C has to
provide the option `-n A', because they have more than one tinc
network.  Finally, D's tincd is started.



@c ==================================================================
@node    Running tinc, Technical information, Configuring tinc, Top
@chapter Running tinc

Running tinc isn't just as easy as typing `tincd' and hoping everything
will just work out the way you wanted.  Instead, the use of tinc is a
project that involves trust relations and more than one computer.

@menu
* Managing keys::               
* Runtime options::             
* Error messages::              
@end menu


@c ==================================================================
@node    Managing keys, Runtime options, Running tinc, Running tinc
@section Managing keys

Before attempting to start tinc, you have to create public/private keypairs.
When tinc tries to make a connection, it exchanges some sensitive
data.  Before doing so, it likes to know if the other end is
trustworthy.

To do this, both ends must have some knowledge about the other.  In the
case of tinc this is the public keys.

To generate a public/private keypair, run `tincd -n vpn-name -K<bits>'.
<bits> is optional, you can use it to specify the length of the keys.
The length of the public/private keypairs
should be at least 1024 for reasonable security (reasonable being good enough
to keep the NSA busy for a few weeks).

Every computer that wants to participate in the VPN should do this. The
public keyfile should get the name of each tinc daemon and an extension .pub,
and it should be stored in the hosts directory.

When every computer has his own keys and configuration files, the files in the
hosts directory should be exchanged with each other computer that it wants to
talk to directly. Since only public keys are involved, you can safely do this
via email, telnet or ftp, or even putting the contents on a public billboard.


@c ==================================================================
@node    Runtime options, Error messages, Managing keys, Running tinc
@section Runtime options

Besides the settings in the configuration file, tinc also accepts some
command line options.

This list is a longer version of that in the manpage.  The latter is
generated automatically, so may be more up-to-date.

@cindex command line
@cindex runtime options
@cindex options
@c from the manpage
@table @samp
@item -c, --config=PATH
Read configuration options from the directory PATH.  The default is
@file{/etc/tinc/nn/}.

@item -d
Increase debug level.  The higher it gets, the more gets
logged.  Everything goes via syslog.

0 is the default, only some basic information connection attempts get
logged.  Setting it to 1 will log a bit more, still not very
disturbing.  With two -d's tincd will log protocol information, which can
get pretty noisy.  Three or more -d's will output every single packet
that goes out or comes in, which probably generates more data than the
packets themselves.

@item -k, --kill
Attempt to kill a running tincd and exit.  A TERM signal (15) gets sent
to the daemon that his its PID in /var/run/tinc.pid.

Because it kills only one tinc daemon, you should use -n here if you
started it that way.  It will then read the PID from
@file{/var/run/tinc.NETNAME.pid}.

@item -n, --net=NETNAME
Connect to net NETNAME.  @xref{Multiple networks}.

@item -K, --generate-keys[=BITS]
Generate public/private keypair of BITS length. If BITS is not specified,
1024 is the default. tinc will ask where you want to store the files,
but will default to the configuration directory (you can use the -c or -n option
in combination with -K). After that, tinc will quit.

@item --help
Display a short reminder of these runtime options and terminate.

@item --version
Output version information and exit.

@end table


@c ==================================================================
@node    Error messages,  , Runtime options, Running tinc
@section Error messages

What follows is a list of the most common error messages you can see
when configuring tinc.  Most of these messages are visible in the syslog
only, so keep an eye on it!

@table @strong
@item Could not open /dev/tap0: No such device
@table @bullet
@item You forgot to insmod netlink_dev.o
@item You forgot to compile `Netlink device emulation' in the kernel
@end table

@item Can't write to tun/tap device: No such device
@table @bullet
@item You forgot to insmod tun.o
@item You forgot to compile `Universal TUN/TAP driver' in the kernel
@end table

@item Packet with destination 1.2.3.4 is looping back to us!
@table @bullet
@item Something is not configured right. Packets are being sent out to the
tap device, but according to the Subnet directives in your host configuration
file, those packets should go to your own host. Most common mistake is that
you have a Subnet line in your host configuration file with a netmask which is
just as large as the netmask of the tap device. The latter should in almost all
cases be larger. Rethink your configuration.
Note that you will only see this message if you specified a debug
level of 5 or higher!
@end table

@item Network address and subnet mask do not match!
@table @bullet
@item The Subnet field must contain a network address. That means that
the lower order bits of the address must be zero. For example, 192.168.1.1/24
is wrong, you should use 192.168.1.0/24.
@item If you only want to use one IP address, set the netmask to /32.
@end table

@item This is a bug: net.c:253: 24: Some error
@table @bullet
@item This is something that should not have happened
Please report this, and tell us exactly what went wrong before you got
this message.  In normal operation, these errors should not occur.
@end table

@item Error reading RSA key file `rsa_key.priv': No such file or directory
@table @bullet
@item You must specify the complete pathname
Specifying a relative path does not make sense here.  tinc changes its
directory to / when starting (to avoid keeping a mount point busy); and
even if we built in a default directory to look for these files, the key
files are bound to be in a different directory.
@end table

@end table


@c ==================================================================
@node    Technical information, About us, Running tinc, Top
@chapter Technical information

@menu
* The Connection::              
* Security::                    
@end menu


@c ==================================================================
@node    The Connection, Security, Technical information, Technical information
@section The basic philosophy of the way tinc works
@cindex connection

tinc is a daemon that takes VPN data and transmit that to another host
computer over the existing Internet infrastructure.

@menu
* Protocol Preview::            
* The Meta-connection::         
@end menu


@c ==================================================================
@node    Protocol Preview, The Meta-connection, The Connection, The Connection
@subsection A preview of the way the tinc works

@cindex ethertap
@cindex frame type
The data itself is read from a character device file, the so-called
@emph{ethertap} device.  This device is associated with a network
interface.  Any data sent to this interface can be read from the device,
and any data written to the device gets sent from the interface.  Data to
and from the device is formatted as if it were a normal ethernet card,
so a frame is preceded by two MAC addresses and a @emph{frame type}
field.

So when tinc reads an ethernet frame from the device, it determines its
type.  Right now, tinc can only handle Internet Protocol version 4 (IPv4)
frames, because it needs IP headers for routing.
Plans to support other protocols and switching instead of routing are being made.
When tinc knows
which type of frame it has read, it can also read the source and
destination address from it.

Now it is time that the frame gets encrypted.  Currently the only
encryption algorithm available is blowfish.

@cindex encapsulating
When the encryption is ready, time has come to actually transport the
packet to the destination computer.  We do this by sending the packet
over an UDP connection to the destination host.  This is called
@emph{encapsulating}, the VPN packet (though now encrypted) is
encapsulated in another IP datagram.

When the destination receives this packet, the same thing happens, only
in reverse.  So it does a decrypt on the contents of the UDP datagram,
and it writes the decrypted information to its own ethertap device.

To let the kernel on the receiving end accept the packet, the destination MAC
address must match that of the tap interface. Because of the routing nature
of tinc, ARP is not possible. tinc solves this by always overwriting the
destination MAC address with fe:fd:0:0:0:0. That is also the reason why you must
set the MAC address of your tap interface to that address.


@c ==================================================================
@node    The Meta-connection,  , Protocol Preview, The Connection
@subsection The meta-connection

Having only an UDP connection available is not enough.  Though suitable
for transmitting data, we want to be able to reliably send other
information, such as routing and encryption information to somebody.

TCP is a better alternative, because it already contains protection
against information being lost, unlike UDP.

So we establish two connections.  One for the encrypted VPN data, and one
for other information, the meta-data.  Hence, we call the second
connection the meta-connection.  We can now be sure that the
meta-information doesn't get lost on the way to another computer.

@cindex data-protocol
@cindex meta-protocol
Like with any communication, we must have a protocol, so that everybody
knows what everything stands for, and how she should react.  Because we
have two connections, we also have two protocols.  The protocol used for
the UDP data is the ``data-protocol,'' the other one is the
``meta-protocol.''

The reason we don't use TCP for both protocols is that UDP is much
better for encapsulation, even while it is less reliable.  The real
problem is that when TCP would be used to encapsulate a TCP stream
that's on the private network, for every packet sent there would be
three ACK's sent instead of just one.  Furthermore, if there would be
a timeout, both TCP streams would sense the timeout, and both would
start resending packets.

@c ==================================================================
@node    Security,  , The Connection, Technical information
@section About tinc's encryption and other security-related issues.

@cindex tinc
@cindex Cabal
tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
alleged Cabal was/is an organization that was said to keep an eye on the
entire Internet.  As this is exactly what you @emph{don't} want, we named
the tinc project after TINC.

@cindex SVPN
But in order to be ``immune'' to eavesdropping, you'll have to encrypt
your data.  Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
exactly that: encrypt.

This chapter is a mixture of ideas, reasoning and explanation, please
don't take it too serious.

@menu
* Key Types::                   
@end menu

@c ==================================================================
@node    Key Types, , Security, Security
@subsection Key Types
@c FIXME: check if I'm not talking nonsense

There are several types of encryption keys.  Tinc uses two of them,
symmetric private keypairs and public/private keypairs.

Public/private keypairs are used in public key cryptography.  It enables
someone to send out a public key with which other people can encrypt their
data.  The encrypted data now can only be decrypted by the person who has
the private key that matches the public key.  So, a public key only allows
@emph{other} people to send encrypted messages to you.  This is very useful
in setting up private communications channels.  Just send out your public key
and other people can talk to you in a secure way.  But how can you know
the other person is who she says she is? This is done by sending out an
encrypted challenge that only the person with the right private key can decode
an respond to.

However, encryption with public/private keys is very slow. Symmetric key cryptography
is orders of magnitudes faster, but it is very hard to safely exchange the symmetric
keys, since they should be kept private.

The idea is to use public/private cryptography for authentication, and for
exchanging symmetric keys in a safe way. After that, all communications are encrypted
with the symmetric cipher.


@c ==================================================================
@node    About us, Concept Index, Technical information, Top
@chapter About us


@menu
* Contact Information::         
* Authors::                     
@end menu


@c ==================================================================
@node    Contact Information, Authors, About us, About us
@section Contact information

tinc's main page is at @url{http://tinc.nl.linux.org/},
this server is located in the Netherlands.

We have an IRC channel on the Open Projects IRC network.  Connect to
@uref{http://openprojects.nu/services/irc.html, irc.openprojects.net},
and join channel #tinc.


@c ==================================================================
@node    Authors,  , Contact Information, About us
@section Authors

@table @asis
@item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com})
Main coder/hacker and maintainer of the package.

@item Guus Sliepen (guus) (@email{guus@@sliepen.warande.net})
Originator of it all, co-author.

@item Wessel Dankers (Ubiq) (@email{wsl@@nl.linux.org})
For the name `tinc' and various suggestions.

@end table

We have received a lot of valuable input from users.  With their help,
tinc has become the flexible and robust tool that it is today.  We have
composed a list of contributions, in the file called @file{THANKS} in
the source distribution.


@c ==================================================================
@node    Concept Index,  , About us, Top
@c        node-name,    next, previous,        up
@unnumbered Concept Index

@c ==================================================================
@printindex cp


@c ==================================================================
@contents
@bye