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This is tinc.info, produced by makeinfo version 4.13 from tinc.texi.
INFO-DIR-SECTION Networking tools
START-INFO-DIR-ENTRY
* tinc: (tinc). The tinc Manual.
END-INFO-DIR-ENTRY
This is the info manual for tinc version 1.1pre2, a Virtual Private
Network daemon.
Copyright (C) 1998-2012 Ivo Timmermans, Guus Sliepen
<guus@tinc-vpn.org> and Wessel Dankers <wsl@tinc-vpn.org>.
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.

File: tinc.info, Node: Top, Next: Introduction, Up: (dir)
Top
***
* Menu:
* Introduction::
* Preparations::
* Installation::
* Configuration::
* Running tinc::
* Controlling tinc::
* Technical information::
* Platform specific information::
* About us::
* Concept Index:: All used terms explained

File: tinc.info, Node: Introduction, Next: Preparations, Prev: Top, Up: Top
1 Introduction
**************
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. The
encrypted tunnels 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:
* Virtual Private Networks::
* tinc:: About tinc
* Supported platforms::

File: tinc.info, Node: Virtual Private Networks, Next: tinc, Up: Introduction
1.1 Virtual Private Networks
============================
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.
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 _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.
This problem can be solved by using _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
the Internet. Mostly, virtual networks appear like a single 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.
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.
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.

File: tinc.info, Node: tinc, Next: Supported platforms, Prev: Virtual Private Networks, Up: Introduction
1.2 tinc
========
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 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 "vpnd".
Since then, a lot has changed--to say the least.
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.
Tinc also allows more than two sites to connect to eachother and
form a single VPN. Traditionally VPNs are created by making tunnels,
which only have two endpoints. Larger VPNs with more sites are created
by adding more tunnels. Tinc takes another approach: only endpoints
are specified, the software itself will take care of creating the
tunnels. This allows for easier configuration and improved scalability.
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.

File: tinc.info, Node: Supported platforms, Prev: tinc, Up: Introduction
1.3 Supported platforms
=======================
Tinc has been verified to work under Linux, FreeBSD, OpenBSD, NetBSD,
MacOS/X (Darwin), Solaris, and Windows (both natively and in a Cygwin
environment), with various hardware architectures. These are some of
the platforms that are supported by the universal tun/tap device driver
or other virtual network device drivers. Without such a 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: `http://www.tinc-vpn.org/platforms/'.

File: tinc.info, Node: Preparations, Next: Installation, Prev: Introduction, Up: Top
2 Preparations
**************
This chapter contains information on how to prepare your system to
support tinc.
* Menu:
* Configuring the kernel::
* Libraries::

File: tinc.info, Node: Configuring the kernel, Next: Libraries, Up: Preparations
2.1 Configuring the kernel
==========================
* Menu:
* Configuration of Linux kernels::
* Configuration of FreeBSD kernels::
* Configuration of OpenBSD kernels::
* Configuration of NetBSD kernels::
* Configuration of Solaris kernels::
* Configuration of Darwin (MacOS/X) kernels::
* Configuration of Windows::

File: tinc.info, Node: Configuration of Linux kernels, Next: Configuration of FreeBSD kernels, Up: Configuring the kernel
2.1.1 Configuration of Linux kernels
------------------------------------
For tinc to work, you need a kernel that supports the Universal tun/tap
device. Most distributions come with kernels that already support this.
Here are the options you have to turn on when configuring a new kernel:
Code maturity level options
[*] Prompt for development and/or incomplete code/drivers
Network device support
<M> Universal tun/tap device driver support
It's not necessary to compile this driver as a module, even if you
are going to run more than one instance of tinc.
If you decide to build the tun/tap driver as a kernel module, add
these lines to `/etc/modules.conf':
alias char-major-10-200 tun

File: tinc.info, Node: Configuration of FreeBSD kernels, Next: Configuration of OpenBSD kernels, Prev: Configuration of Linux kernels, Up: Configuring the kernel
2.1.2 Configuration of FreeBSD kernels
--------------------------------------
For FreeBSD version 4.1 and higher, tun and tap drivers are included in
the default kernel configuration. The tap driver can be loaded with
`kldload if_tap', or by adding `if_tap_load="YES"' to
`/boot/loader.conf'.

File: tinc.info, Node: Configuration of OpenBSD kernels, Next: Configuration of NetBSD kernels, Prev: Configuration of FreeBSD kernels, Up: Configuring the kernel
2.1.3 Configuration of OpenBSD kernels
--------------------------------------
For OpenBSD version 2.9 and higher, the tun driver is included in the
default kernel configuration. There is also a kernel patch from
`http://diehard.n-r-g.com/stuff/openbsd/' which adds a tap device to
OpenBSD which should work with tinc, but with recent versions of
OpenBSD, a tun device can act as a tap device by setting the link0
option with ifconfig.

File: tinc.info, Node: Configuration of NetBSD kernels, Next: Configuration of Solaris kernels, Prev: Configuration of OpenBSD kernels, Up: Configuring the kernel
2.1.4 Configuration of NetBSD kernels
-------------------------------------
For NetBSD version 1.5.2 and higher, the tun driver is included in the
default kernel configuration.
Tunneling IPv6 may not work on NetBSD's tun device.

File: tinc.info, Node: Configuration of Solaris kernels, Next: Configuration of Darwin (MacOS/X) kernels, Prev: Configuration of NetBSD kernels, Up: Configuring the kernel
2.1.5 Configuration of Solaris kernels
--------------------------------------
For Solaris 8 (SunOS 5.8) and higher, the tun driver may or may not be
included in the default kernel configuration. If it isn't, the source
can be downloaded from `http://vtun.sourceforge.net/tun/'. For x86 and
sparc64 architectures, precompiled versions can be found at
`http://www.monkey.org/~dugsong/fragroute/'. If the `net/if_tun.h'
header file is missing, install it from the source package.

File: tinc.info, Node: Configuration of Darwin (MacOS/X) kernels, Next: Configuration of Windows, Prev: Configuration of Solaris kernels, Up: Configuring the kernel
2.1.6 Configuration of Darwin (MacOS/X) kernels
-----------------------------------------------
Tinc on Darwin relies on a tunnel driver for its data acquisition from
the kernel. Tinc supports either the driver from
`http://tuntaposx.sourceforge.net/', which supports both tun and tap
style devices, and also the driver from from
`http://chrisp.de/en/projects/tunnel.html'. The former driver is
recommended. The tunnel driver must be loaded before starting tinc
with the following command:
kmodload tunnel

File: tinc.info, Node: Configuration of Windows, Prev: Configuration of Darwin (MacOS/X) kernels, Up: Configuring the kernel
2.1.7 Configuration of Windows
------------------------------
You will need to install the latest TAP-Win32 driver from OpenVPN. You
can download it from `http://openvpn.sourceforge.net'. Using the
Network Connections control panel, configure the TAP-Win32 network
interface in the same way as you would do from the tinc-up script, as
explained in the rest of the documentation.

File: tinc.info, Node: Libraries, Prev: Configuring the kernel, Up: Preparations
2.2 Libraries
=============
Before you can configure or build tinc, you need to have the OpenSSL,
zlib and lzo libraries installed on your system. If you try to
configure tinc without having them installed, configure will give you
an error message, and stop.
* Menu:
* OpenSSL::
* zlib::
* lzo::
* libevent::

File: tinc.info, Node: OpenSSL, Next: zlib, Up: Libraries
2.2.1 OpenSSL
-------------
For all cryptography-related functions, tinc uses the functions provided
by the OpenSSL library.
If this library is not installed, you wil get an error when
configuring tinc for build. Support for running tinc without having
OpenSSL installed _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 `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.
--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)
License
.......
The complete source code of tinc is covered by the GNU GPL version 2.
Since the license under which OpenSSL is distributed is not directly
compatible with the terms of the GNU GPL
`http://www.openssl.org/support/faq.html#LEGAL2', we include an
exemption to the GPL (see also the file COPYING.README) to allow
everyone to create a statically or dynamically linked executable:
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.
Since the LZO library used by tinc is also covered by the GPL, we
also present the following exemption:
Hereby I grant a special exception to the tinc VPN project
(http://www.tinc-vpn.org/) to link the LZO library with the
OpenSSL library (http://www.openssl.org).
Markus F.X.J. Oberhumer

File: tinc.info, Node: zlib, Next: lzo, Prev: OpenSSL, Up: Libraries
2.2.2 zlib
----------
For the optional compression of UDP packets, tinc uses the functions
provided by the zlib library.
If this library is not installed, you wil get an error when
configuring tinc for build. Support for running tinc without having
zlib installed _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 zlib manually, you can get the source code
from `http://www.gzip.org/zlib/'. 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).

File: tinc.info, Node: lzo, Next: libevent, Prev: zlib, Up: Libraries
2.2.3 lzo
---------
Another form of compression is offered using the lzo library.
If this library is not installed, you wil get an error when
configuring tinc for build. Support for running tinc without having lzo
installed _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 lzo manually, you can get the source code
from `http://www.oberhumer.com/opensource/lzo/'. 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).

File: tinc.info, Node: libevent, Prev: lzo, Up: Libraries
2.2.4 libevent
--------------
For the main event loop, tinc uses the libevent library.
If this library is not installed, you wil get an error when
configuring tinc for build.
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 libevent manually, you can get the source code
from `http://libevent.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).

File: tinc.info, Node: Installation, Next: Configuration, Prev: Preparations, Up: Top
3 Installation
**************
If you use 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 cannot use one of the precompiled packages, 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 download page (http://www.tinc-vpn.org/download/),
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 `INSTALL', which is included in the source distribution.
* Menu:
* Building and installing tinc::
* System files::

File: tinc.info, Node: Building and installing tinc, Next: System files, Up: Installation
3.1 Building and installing tinc
================================
Detailed instructions on configuring the source, building tinc and
installing tinc can be found in the file called `INSTALL'.
If you happen to have a binary package for tinc for your
distribution, you can use the package management tools of that
distribution to install tinc. The documentation that comes along with
your distribution will tell you how to do that.
* Menu:
* Darwin (MacOS/X) build environment::
* Cygwin (Windows) build environment::
* MinGW (Windows) build environment::

File: tinc.info, Node: Darwin (MacOS/X) build environment, Next: Cygwin (Windows) build environment, Up: Building and installing tinc
3.1.1 Darwin (MacOS/X) build environment
----------------------------------------
In order to build tinc on Darwin, you need to install the MacOS/X
Developer Tools from
`http://developer.apple.com/tools/macosxtools.html' and a recent
version of Fink from `http://www.finkproject.org/'.
After installation use fink to download and install the following
packages: autoconf25, automake, dlcompat, m4, openssl, zlib and lzo.

File: tinc.info, Node: Cygwin (Windows) build environment, Next: MinGW (Windows) build environment, Prev: Darwin (MacOS/X) build environment, Up: Building and installing tinc
3.1.2 Cygwin (Windows) build environment
----------------------------------------
If Cygwin hasn't already been installed, install it directly from
`http://www.cygwin.com/'.
When tinc is compiled in a Cygwin environment, it can only be run in
this environment, but all programs, including those started outside the
Cygwin environment, will be able to use the VPN. It will also support
all features.

File: tinc.info, Node: MinGW (Windows) build environment, Prev: Cygwin (Windows) build environment, Up: Building and installing tinc
3.1.3 MinGW (Windows) build environment
---------------------------------------
You will need to install the MinGW environment from
`http://www.mingw.org'.
When tinc is compiled using MinGW it runs natively under Windows, it
is not necessary to keep MinGW installed.
When detaching, tinc will install itself as a service, which will be
restarted automatically after reboots.

File: tinc.info, Node: System files, Prev: Building and installing tinc, Up: Installation
3.2 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::

File: tinc.info, Node: Device files, Next: Other files, Up: System files
3.2.1 Device files
------------------
Most operating systems nowadays come with the necessary device files by
default, or they have a mechanism to create them on demand.
If you use Linux and do not have udev installed, you may need to
create the following device file if it does not exist:
mknod -m 600 /dev/net/tun c 10 200

File: tinc.info, Node: Other files, Prev: Device files, Up: System files
3.2.2 Other files
-----------------
`/etc/networks'
...............
You may add a line to `/etc/networks' so that your VPN will get a
symbolic name. For example:
myvpn 10.0.0.0
`/etc/services'
...............
You may add this line to `/etc/services'. The effect is that you may
supply a `tinc' as a valid port number to some programs. The number
655 is registered with the IANA.
tinc 655/tcp TINC
tinc 655/udp TINC
# Ivo Timmermans <ivo@tinc-vpn.org>

File: tinc.info, Node: Configuration, Next: Running tinc, Prev: Installation, Up: Top
4 Configuration
***************
* Menu:
* Configuration introduction::
* Multiple networks::
* How connections work::
* Configuration files::
* Network interfaces::
* Example configuration::

File: tinc.info, Node: Configuration introduction, Next: Multiple networks, Up: Configuration
4.1 Configuration introduction
==============================
Before actually starting to configure tinc and editing files, make sure
you have read this entire section so you know what to expect. Then,
make it clear to yourself how you want to organize your VPN: What are
the nodes (computers running tinc)? What IP addresses/subnets do they
have? What is the network mask of the entire VPN? Do you need special
firewall rules? Do you have to set up masquerading or forwarding rules?
Do you want to run tinc in router mode or switch mode? These questions
can only be answered by yourself, you will not find the answers in this
documentation. Make sure you have an adequate understanding of
networks in general. A good resource on networking is the Linux
Network Administrators Guide (http://www.tldp.org/LDP/nag2/).
If you have everything clearly pictured in your mind, proceed in the
following order: First, create the initial configuration files and
public/private keypairs using the following command:
tincctl -n NETNAME init NAME
Second, use `tincctl -n NETNAME config ...' to further configure
tinc. Finally, export your host configuration file using `tincctl -n
NETNAME export' and send it to those people or computers you want tinc
to connect to. They should send you their host configuration file
back, which you can import using `tincctl -n NETNAME import'.
These steps are described in the subsections below.

File: tinc.info, Node: Multiple networks, Next: How connections work, Prev: Configuration introduction, Up: Configuration
4.2 Multiple networks
=====================
In order to allow you to run more than one tinc daemon on one computer,
for instance if your computer is part of more than one VPN, you can
assign a NETNAME to your VPN. It is not required if you only run one
tinc daemon, it doesn't even have to be the same on all the nodes of
your VPN, but it is recommended that you choose one anyway.
We will asume you use a netname throughout this document. This
means that you call tincctl with the -n argument, which will specify
the netname.
The effect of this option is that tinc will set its configuration
root to `/etc/tinc/NETNAME/', where NETNAME is your argument to the -n
option. You will also notice that log messages it appears in syslog as
coming from `tinc.NETNAME', and on Linux, unless specified otherwise,
the name of the virtual network interface will be the same as the
network name.
However, it is not strictly necessary that you call tinc with the -n
option. If you don not use it, the network name will just be empty, and
tinc will look for files in `/etc/tinc/' instead of
`/etc/tinc/NETNAME/'; the configuration file will then be
`/etc/tinc/tinc.conf', and the host configuration files are expected to
be in `/etc/tinc/hosts/'.

File: tinc.info, Node: How connections work, Next: Configuration files, Prev: Multiple networks, Up: Configuration
4.3 How connections work
========================
When tinc starts up, it parses the command-line options and then reads
in the configuration file tinc.conf. If it sees one or more
`ConnectTo' values pointing to other tinc daemons in that file, it will
try to connect to those other daemons. Whether this succeeds or not
and whether `ConnectTo' is specified or not, tinc will listen for
incoming connection from other deamons. If you did specify a
`ConnectTo' value and the other side is not responding, tinc will keep
retrying. This means that once started, tinc will stay running until
you tell it to stop, and failures to connect to other tinc daemons will
not stop your tinc daemon for trying again later. This means you don't
have to intervene if there are temporary network problems.
There is no real distinction between a server and a client in tinc.
If you wish, you can view a tinc daemon without a `ConnectTo' value as
a server, and one which does specify such a value as a client. It does
not matter if two tinc daemons have a `ConnectTo' value pointing to
each other however.
Connections specified using `ConnectTo' are so-called
meta-connections. Tinc daemons exchange information about all other
daemon they know about via these meta-connections. After learning
about all the daemons in the VPN, tinc will create other connections as
necessary in order to communicate with them. For example, if there are
three daemons named A, B and C, and A has `ConnectTo = B' in its
tinc.conf file, and C has `ConnectTo = B' in its tinc.conf file, then A
will learn about C from B, and will be able to exchange VPN packets
with C without the need to have `ConnectTo = C' in its tinc.conf file.
It could be that some daemons are located behind a Network Address
Translation (NAT) device, or behind a firewall. In the above scenario
with three daemons, if A and C are behind a NAT, B will automatically
help A and C punch holes through their NAT, in a way similar to the
STUN protocol, so that A and C can still communicate with each other
directly. It is not always possible to do this however, and firewalls
might also prevent direct communication. In that case, VPN packets
between A and C will be forwarded by B.
In effect, all nodes in the VPN will be able to talk to each other,
as long as their is a path of meta-connections between them, and
whenever possible, two nodes will communicate with each other directly.

File: tinc.info, Node: Configuration files, Next: Network interfaces, Prev: How connections work, Up: Configuration
4.4 Configuration files
=======================
The actual configuration of the daemon is done in the file
`/etc/tinc/NETNAME/tinc.conf' and at least one other file in the
directory `/etc/tinc/NETNAME/hosts/'.
These file consists of comments (lines started with a #) or
assignments in the form of
Variable = Value.
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.
The server configuration is complemented with host specific
configuration (see the next section). Although all host configuration
options for the local node listed in this document can also be put in
`/etc/tinc/NETNAME/tinc.conf', it is recommended to put host specific
configuration options in the host configuration file, as this makes it
easy to exchange with other nodes.
You can edit the config file manually, but it is recommended that
you use tincctl to change configuration variables for you.
In the following two subsections all valid variables are listed in
alphabetical order. The default value is given between parentheses,
other comments are between square brackets.
* Menu:
* Main configuration variables::
* Host configuration variables::
* Scripts::
* How to configure::

File: tinc.info, Node: Main configuration variables, Next: Host configuration variables, Up: Configuration files
4.4.1 Main configuration variables
----------------------------------
AddressFamily = <ipv4|ipv6|any> (any)
This option affects the address family of listening and outgoing
sockets. If any is selected, then depending on the operating
system both IPv4 and IPv6 or just IPv6 listening sockets will be
created.
BindToAddress = <ADDRESS> [<PORT>]
If your computer has more than one IPv4 or IPv6 address, tinc will
by default listen on all of them for incoming connections.
Multiple BindToAddress variables may be specified, in which case
listening sockets for each specified address are made.
If no PORT is specified, the socket will be bound to the port
specified by the Port option, or to port 655 if neither is given.
To only bind to a specific port but not to a specific address, use
"*" for the ADDRESS.
BindToInterface = <INTERFACE> [experimental]
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.
This option may not work on all platforms. Also, on some
platforms it will not actually bind to an interface, but rather to
the address that the interface has at the moment a socket is
created.
Broadcast = <no | mst | direct> (mst) [experimental]
This option selects the way broadcast packets are sent to other
daemons. _NOTE: all nodes in a VPN must use the same Broadcast
mode, otherwise routing loops can form._
no
Broadcast packets are never sent to other nodes.
mst
Broadcast packets are sent and forwarded via the VPN's
Minimum Spanning Tree. This ensures broadcast packets reach
all nodes.
direct
Broadcast packets are sent directly to all nodes that can be
reached directly. Broadcast packets received from other
nodes are never forwarded. If the IndirectData option is
also set, broadcast packets will only be sent to nodes which
we have a meta connection to.
ConnectTo = <NAME>
Specifies which other tinc daemon to connect to on startup.
Multiple ConnectTo variables may be specified, in which case
outgoing connections to each specified tinc daemon are made. The
names should be known to this tinc daemon (i.e., there should be a
host configuration file for the name on the ConnectTo line).
If you don't specify a host with ConnectTo, tinc won't try to
connect to other daemons at all, and will instead just listen for
incoming connections.
DecrementTTL = <yes | no> (no) [experimental]
When enabled, tinc will decrement the Time To Live field in IPv4
packets, or the Hop Limit field in IPv6 packets, before forwarding
a received packet to the virtual network device or to another node,
and will drop packets that have a TTL value of zero, in which case
it will send an ICMP Time Exceeded packet back.
Do not use this option if you use switch mode and want to use IPv6.
Device = <DEVICE> (`/dev/tap0', `/dev/net/tun' or other depending on platform)
The virtual network device to use. Tinc will automatically detect
what kind of device it is. Note that you can only use one device
per daemon. Under Windows, use INTERFACE instead of DEVICE. Note
that you can only use one device per daemon. See also *note
Device files::.
DeviceType = <TYPE> (platform dependent)
The type of the virtual network device. Tinc will normally
automatically select the right type of tun/tap interface, and this
option should not be used. However, this option can be used to
select one of the special interface types, if support for them is
compiled in.
dummy
Use a dummy interface. No packets are ever read or written
to a virtual network device. Useful for testing, or when
setting up a node that only forwards packets for other nodes.
raw_socket
Open a raw socket, and bind it to a pre-existing INTERFACE
(eth0 by default). All packets are read from this interface.
Packets received for the local node are written to the raw
socket. However, at least on Linux, the operating system
does not process IP packets destined for the local host.
multicast
Open a multicast UDP socket and bind it to the address and
port (separated by spaces) and optionally a TTL value
specified using DEVICE. Packets are read from and written to
this multicast socket. This can be used to connect to UML,
QEMU or KVM instances listening on the same multicast address.
Do NOT connect multiple tinc daemons to the same multicast
address, this will very likely cause routing loops. Also
note that this can cause decrypted VPN packets to be sent out
on a real network if misconfigured.
uml (not compiled in by default)
Create a UNIX socket with the filename specified by DEVICE,
or `/var/run/NETNAME.umlsocket' if not specified. Tinc will
wait for a User Mode Linux instance to connect to this socket.
vde (not compiled in by default)
Uses the libvdeplug library to connect to a Virtual
Distributed Ethernet switch, using the UNIX socket specified
by DEVICE, or `/var/run/vde.ctl' if not specified.
Also, in case tinc does not seem to correctly interpret packets
received from the virtual network device, it can be used to change
the way packets are interpreted:
tun (BSD and Linux)
Set type to tun. Depending on the platform, this can either
be with or without an address family header (see below).
tunnohead (BSD)
Set type to tun without an address family header. Tinc will
expect packets read from the virtual network device to start
with an IP header. On some platforms IPv6 packets cannot be
read from or written to the device in this mode.
tunifhead (BSD)
Set type to tun with an address family header. Tinc will
expect packets read from the virtual network device to start
with a four byte header containing the address family,
followed by an IP header. This mode should support both IPv4
and IPv6 packets.
tap (BSD and Linux)
Set type to tap. Tinc will expect packets read from the
virtual network device to start with an Ethernet header.
DirectOnly = <yes|no> (no) [experimental]
When this option is enabled, packets that cannot be sent directly
to the destination node, but which would have to be forwarded by
an intermediate node, are dropped instead. When combined with the
IndirectData option, packets for nodes for which we do not have a
meta connection with are also dropped.
ECDSAPrivateKeyFile = <PATH> (`/etc/tinc/NETNAME/ecdsa_key.priv')
The file in which the private ECDSA key of this tinc daemon
resides. This is only used if ExperimentalProtocol is enabled.
ExperimentalProtocol = <yes|no> (no) [experimental]
When this option is enabled, experimental protocol enhancements
will be used. Ephemeral ECDH will be used for key exchanges, and
ECDSA will be used instead of RSA for authentication. When
enabled, an ECDSA key must have been generated before with
`tincctl generate-ecdsa-keys'. The experimental protocol may
change at any time, and there is no guarantee that tinc will run
stable when it is used.
Forwarding = <off|internal|kernel> (internal) [experimental]
This option selects the way indirect packets are forwarded.
off
Incoming packets that are not meant for the local node, but
which should be forwarded to another node, are dropped.
internal
Incoming packets that are meant for another node are
forwarded by tinc internally.
This is the default mode, and unless you really know you need
another forwarding mode, don't change it.
kernel
Incoming packets are always sent to the TUN/TAP device, even
if the packets are not for the local node. This is less
efficient, but allows the kernel to apply its routing and
firewall rules on them, and can also help debugging.
GraphDumpFile = <FILENAME>
If this option is present, tinc will dump the current network
graph to the file FILENAME every minute, unless there were no
changes to the graph. The file is in a format that can be read by
graphviz tools. If FILENAME starts with a pipe symbol |, then the
rest of the filename is interpreted as a shell command that is
executed, the graph is then sent to stdin.
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, but whether hostnames should be resolved while
logging.
Interface = <INTERFACE>
Defines the name of the interface corresponding to the virtual
network device. Depending on the operating system and the type of
device this may or may not actually set the name of the interface.
Under Windows, this variable is used to select which network
interface will be used. If you specified a Device, this variable
is almost always already correctly set.
LocalDiscovery = <yes | no> (no)
When enabled, tinc will try to detect peers that are on the same
local network. This will allow direct communication using LAN
addresses, even if both peers are behind a NAT and they only
ConnectTo a third node outside the NAT, which normally would
prevent the peers from learning each other's LAN address.
Currently, local discovery is implemented by sending broadcast
packets to the LAN during path MTU discovery. This feature may
not work in all possible situations.
Mode = <router|switch|hub> (router)
This option selects the way packets are routed to other daemons.
router
In this mode Subnet variables in the host configuration files
will be used to form a routing table. Only unicast packets
of routable protocols (IPv4 and IPv6) are supported in this
mode.
This is the default mode, and unless you really know you need
another mode, don't change it.
switch
In this mode the MAC addresses of the packets on the VPN will
be used to dynamically create a routing table just like an
Ethernet switch does. Unicast, multicast and broadcast
packets of every protocol that runs over Ethernet are
supported in this mode at the cost of frequent broadcast ARP
requests and routing table updates.
This mode is primarily useful if you want to bridge Ethernet
segments.
hub
This mode is almost the same as the switch mode, but instead
every packet will be broadcast to the other daemons while no
routing table is managed.
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.
MACExpire = <SECONDS> (600)
This option controls the amount of time MAC addresses are kept
before they are removed. This only has effect when Mode is set to
"switch".
Name = <NAME> [required]
This is a symbolic name for this connection. The name should
consist only of alfanumeric and underscore characters (a-z, A-Z,
0-9 and _).
If Name starts with a $, then the contents of the environment
variable that follows will be used. In that case, invalid
characters will be converted to underscores. If Name is $HOST,
but no such environment variable exist, the hostname will be read
using the gethostnname() system call.
PingInterval = <SECONDS> (60)
The number of seconds of inactivity that tinc will wait before
sending a probe to the other end.
PingTimeout = <SECONDS> (5)
The number of seconds to wait for a response to pings or to allow
meta connections to block. If the other end doesn't respond within
this time, the connection is terminated, and the others will be
notified of this.
PriorityInheritance = <yes|no> (no) [experimental]
When this option is enabled the value of the TOS field of tunneled
IPv4 packets will be inherited by the UDP packets that are sent
out.
PrivateKey = <KEY> [obsolete]
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.
PrivateKeyFile = <PATH> (`/etc/tinc/NETNAME/rsa_key.priv')
This is the full path name of the RSA private key file that was
generated by `tincctl generate-keys'. It must be a full path, not
a relative directory.
Note that there must be exactly one of PrivateKey or PrivateKeyFile
specified in the configuration file.
ProcessPriority = <low|normal|high>
When this option is used the priority of the tincd process will be
adjusted. Increasing the priority may help to reduce latency and
packet loss on the VPN.
Proxy = socks4 | socks4 | http | exec ... [experimental]
Use a proxy when making outgoing connections. The following proxy
types are currently supported:
socks4 <ADDRESS> <PORT> [<USERNAME>]
Connects to the proxy using the SOCKS version 4 protocol.
Optionally, a USERNAME can be supplied which will be passed
on to the proxy server.
socks4 <ADDRESS> <PORT> [<USERNAME> <PASSWORD>]
Connect to the proxy using the SOCKS version 5 protocol. If
a USERNAME and PASSWORD are given, basic username/password
authentication will be used, otherwise no authentication will
be used.
http <ADDRESS> <PORT>
Connects to the proxy and sends a HTTP CONNECT request.
exec <COMMAND>
Executes the given command which should set up the outgoing
connection. The environment variables `NAME', `NODE',
`REMOTEADDRES' and `REMOTEPORT' are available.
ReplayWindow = <bytes> (16)
This is the size of the replay tracking window for each remote
node, in bytes. The window is a bitfield which tracks 1 packet
per bit, so for example the default setting of 16 will track up to
128 packets in the window. In high bandwidth scenarios, setting
this to a higher value can reduce packet loss from the interaction
of replay tracking with underlying real packet loss and/or
reordering. Setting this to zero will disable replay tracking
completely and pass all traffic, but leaves tinc vulnerable to
replay-based attacks on your traffic.
StrictSubnets <yes|no> (no) [experimental]
When this option is enabled tinc will only use Subnet statements
which are present in the host config files in the local
`/etc/tinc/NETNAME/hosts/' directory.
TunnelServer = <yes|no> (no) [experimental]
When this option is enabled tinc will no longer forward
information between other tinc daemons, and will only allow
connections with nodes for which host config files are present in
the local `/etc/tinc/NETNAME/hosts/' directory. Setting this
options also implicitly sets StrictSubnets.
UDPRcvBuf = <bytes> (OS default)
Sets the socket receive buffer size for the UDP socket, in bytes.
If unset, the default buffer size will be used by the operating
system.
UDPSndBuf = <bytes> Pq OS default
Sets the socket send buffer size for the UDP socket, in bytes. If
unset, the default buffer size will be used by the operating
system.

File: tinc.info, Node: Host configuration variables, Next: Scripts, Prev: Main configuration variables, Up: Configuration files
4.4.2 Host configuration variables
----------------------------------
Address = <IP ADDRESS|HOSTNAME> [<port>] [recommended]
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. If no
port is specified, the default Port is used.
Cipher = <CIPHER> (blowfish)
The symmetric cipher algorithm used to encrypt UDP packets. Any
cipher supported by OpenSSL is recognized. Furthermore,
specifying "none" will turn off packet encryption. It is best to
use only those ciphers which support CBC mode.
ClampMSS = <yes|no> (yes)
This option specifies whether tinc should clamp the maximum
segment size (MSS) of TCP packets to the path MTU. This helps in
situations where ICMP Fragmentation Needed or Packet too Big
messages are dropped by firewalls.
Compression = <LEVEL> (0)
This option sets the level of compression used for UDP packets.
Possible values are 0 (off), 1 (fast zlib) and any integer up to 9
(best zlib), 10 (fast lzo) and 11 (best lzo).
Digest = <DIGEST> (sha1)
The digest algorithm used to authenticate UDP packets. Any digest
supported by OpenSSL is recognized. Furthermore, specifying
"none" will turn off packet authentication.
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.
MACLength = <BYTES> (4)
The length of the message authentication code used to authenticate
UDP packets. Can be anything from 0 up to the length of the
digest produced by the digest algorithm.
PMTU = <MTU> (1514)
This option controls the initial path MTU to this node.
PMTUDiscovery = <yes|no> (yes)
When this option is enabled, tinc will try to discover the path
MTU to this node. After the path MTU has been discovered, it will
be enforced on the VPN.
Port = <PORT> (655)
This is the port this tinc daemon listens on. You can use decimal
portnumbers or symbolic names (as listed in `/etc/services').
PublicKey = <KEY> [obsolete]
This is the RSA public key for this host.
PublicKeyFile = <PATH> [obsolete]
This is the full path name of the RSA public key file that was
generated by `tincctl generate-keys'. It must be a full path, not
a relative directory.
From version 1.0pre4 on tinc will store the public key directly
into the host configuration file in PEM format, the above two
options then are not necessary. Either the PEM format is used, or
exactly *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.
Subnet = <ADDRESS[/PREFIXLENGTH[#WEIGHT]]>
The subnet which this tinc daemon will serve. Tinc tries to look
up which other daemon it should send a packet to by searching the
appropiate subnet. If the packet matches a subnet, it will be
sent to the daemon who has this subnet in his host configuration
file. Multiple subnet lines can be specified for each daemon.
Subnets can either be single MAC, IPv4 or IPv6 addresses, in which
case a subnet consisting of only that single address is assumed,
or they can be a IPv4 or IPv6 network address with a prefixlength.
For example, IPv4 subnets must be in a form like 192.168.1.0/24,
where 192.168.1.0 is the network address and 24 is the number of
bits set in the netmask. Note that subnets like 192.168.1.1/24
are invalid! Read a networking HOWTO/FAQ/guide if you don't
understand this. IPv6 subnets are notated like fec0:0:0:1::/64.
MAC addresses are notated like 0:1a:2b:3c:4d:5e.
Prefixlength 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 RFC1519 (http://www.ietf.org/rfc/rfc1519.txt)
A Subnet can be given a weight to indicate its priority over
identical Subnets owned by different nodes. The default weight is
10. Lower values indicate higher priority. Packets will be sent to
the node with the highest priority, unless that node is not
reachable, in which case the node with the next highest priority
will be tried, and so on.
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. Setting this options also implicitly sets
IndirectData.

File: tinc.info, Node: Scripts, Next: How to configure, Prev: Host configuration variables, Up: Configuration files
4.4.3 Scripts
-------------
Apart from reading the server and host configuration files, tinc can
also run scripts at certain moments. Under Windows (not Cygwin), the
scripts should have the extension .bat.
`/etc/tinc/NETNAME/tinc-up'
This is the most important script. If it is present it will be
executed right after the tinc daemon has been started and has
connected to the virtual network device. It should be used to set
up the corresponding network interface, but can also be used to
start other things. Under Windows you can use the Network
Connections control panel instead of creating this script.
`/etc/tinc/NETNAME/tinc-down'
This script is started right before the tinc daemon quits.
`/etc/tinc/NETNAME/hosts/HOST-up'
This script is started when the tinc daemon with name HOST becomes
reachable.
`/etc/tinc/NETNAME/hosts/HOST-down'
This script is started when the tinc daemon with name HOST becomes
unreachable.
`/etc/tinc/NETNAME/host-up'
This script is started when any host becomes reachable.
`/etc/tinc/NETNAME/host-down'
This script is started when any host becomes unreachable.
`/etc/tinc/NETNAME/subnet-up'
This script is started when a Subnet becomes reachable. The
Subnet and the node it belongs to are passed in environment
variables.
`/etc/tinc/NETNAME/subnet-down'
This script is started when a Subnet becomes unreachable.
The scripts are started without command line arguments, but can make
use of certain environment variables. Under UNIX like operating
systems the names of environment variables must be preceded by a $ in
scripts. Under Windows, in `.bat' files, they have to be put between %
signs.
`NETNAME'
If a netname was specified, this environment variable contains it.
`NAME'
Contains the name of this tinc daemon.
`DEVICE'
Contains the name of the virtual network device that tinc uses.
`INTERFACE'
Contains the name of the virtual network interface that tinc uses.
This should be used for commands like ifconfig.
`NODE'
When a host becomes (un)reachable, this is set to its name. If a
subnet becomes (un)reachable, this is set to the owner of that
subnet.
`REMOTEADDRESS'
When a host becomes (un)reachable, this is set to its real address.
`REMOTEPORT'
When a host becomes (un)reachable, this is set to the port number
it uses for communication with other tinc daemons.
`SUBNET'
When a subnet becomes (un)reachable, this is set to the subnet.

File: tinc.info, Node: How to configure, Prev: Scripts, Up: Configuration files
4.4.4 How to configure
----------------------
Step 1. Creating initial configuration files.
..............................................
The initial directory structure, configuration files and public/private
keypairs are created using the following command:
tincctl -n NETNAME init NAME
(You will need to run this as root, or use "sudo".) This will
create the configuration directory `/etc/tinc/NETNAME.', and inside it
will create another directory named `hosts/'. In the configuration
directory, it will create the file `tinc.conf' with the following
contents:
Name = NAME
It will also create private RSA and ECDSA keys, which will be stored
in the files `rsa_key.priv' and `ecdsa_key.priv'. It will also create
a host configuration file `hosts/NAME', which will contain the
corresponding public RSA and ECDSA keys.
Finally, on UNIX operating systems, it will create an executable
script `tinc-up', which will initially not do anything except warning
that you should edit it.
Step 2. Modifying the initial configuration.
.............................................
Unless you want to use tinc in switch mode, you should now configure
which range of addresses you will use on the VPN. Let's assume you
will be part of a VPN which uses the address range 192.168.0.0/16, and
you yourself have a smaller portion of that range: 192.168.2.0/24.
Then you should run the following command:
tincctl -n NETNAME config add subnet 192.168.2.0/24
This will add a Subnet statement to your host configuration file.
Try opening the file `/etc/tinc/NETNAME/hosts/NAME' in an editor. You
should now see a file containing the public RSA and ECDSA keys (which
looks like a bunch of random characters), and the following line at the
bottom:
Subnet = 192.168.2.0/24
If you will use more than one address range, you can add more
Subnets. For example, if you also use the IPv6 subnet fec0:0:0:2::/64,
you can add it as well:
tincctl -n NETNAME config add subnet fec0:0:0:2::/24
This will add another line to the file `hosts/NAME'. If you make a
mistake, you can undo it by simply using `config del' instead of
`config add'.
If you want other tinc daemons to create meta-connections to your
daemon, you should add your public IP address or hostname to your host
configuration file. For example, if your hostname is foo.example.org,
run:
tincctl -n NETNAME config add address foo.example.org
If you already know to which daemons your daemon should make
meta-connections, you should configure that now as well. Suppose you
want to connect to a daemon named "bar", run:
tincctl -n NETNAME config add connectto bar
Note that you specify the Name of the other daemon here, not an IP
address or hostname! When you start tinc, and it tries to make a
connection to "bar", it will look for a host configuration file named
`hosts/bar', and will read Address statements and public keys from that
file.
Step 2. Exchanging configuration files.
........................................
If your daemon has a ConnectTo = bar statement in its `tinc.conf' file,
or if bar has a ConnectTo your daemon, then you both need each other's
host configuration files. You should send `hosts/NAME' to bar, and bar
should send you his file which you should move to `hosts/bar'. If you
are on a UNIX platform, you can easily send an email containing the
necessary information using the following command (assuming the owner
of bar has the email address bar@example.org):
tincctl -n NETNAME export | mail -s "My config file" bar@example.org
If the owner of bar does the same to send his host configuration
file to you, you can probably pipe his email through the following
command, or you can just start this command in a terminal and
copy&paste the email:
tincctl -n NETNAME import
If you are the owner of bar yourself, and you have SSH access to
that computer, you can also swap the host configuration files using the
following commands:
tincctl -n NETNAME export | ssh bar.example.org tincctl -n NETNAME import
ssh bar.example.org tincctl -n NETNAME export | tincctl -n NETNAME import
You should repeat this for all nodes you ConnectTo, or which
ConnectTo you. However, remember that you do not need to ConnectTo all
nodes in the VPN; it is only necessary to create one or a few
meta-connections, after the connections are made tinc will learn about
all the other nodes in the VPN, and will automatically make other
connections as necessary.

File: tinc.info, Node: Network interfaces, Next: Example configuration, Prev: Configuration files, Up: Configuration
4.5 Network interfaces
======================
Before tinc can start transmitting data over the tunnel, it must set up
the virtual network interface.
First, decide which IP addresses you want to have associated with
these devices, and what network mask they must have.
Tinc will open a virtual network device (`/dev/tun', `/dev/tap0' or
similar), which will also create a network interface called something
like `tun0', `tap0'. If you are using the Linux tun/tap driver, the
network interface will by default have the same name as the NETNAME.
Under Windows you can change the name of the network interface from the
Network Connections control panel.
You can configure the network interface by putting ordinary
ifconfig, route, and other commands to a script named
`/etc/tinc/NETNAME/tinc-up'. When tinc starts, this script will be
executed. When tinc exits, it will execute the script named
`/etc/tinc/NETNAME/tinc-down', but normally you don't need to create
that script. You can manually open the script in an editor, or use the
following command:
tincctl -n NETNAME edit tinc-up
An example `tinc-up' script, that would be appropriate for the
scenario in the previous section, is:
#!/bin/sh
ifconfig $INTERFACE 192.168.2.1 netmask 255.255.0.0
ip addr add fec0:0:0:2::/48 dev $INTERFACE
The first command gives the interface an IPv4 address and a netmask.
The kernel will also automatically add an IPv4 route to this interface,
so normally you don't need to add route commands to the `tinc-up'
script. The kernel will also bring the interface up after this command. The
netmask is the mask of the _entire_ VPN network, not just your own
subnet. The second command gives the interface an IPv6 address and
netmask, which will also automatically add an IPv6 route. If you only
want to use "ip addr" commands on Linux, don't forget that it doesn't
bring the interface up, unlike ifconfig, so you need to add `ip link
set $INTERFACE up' in that case.
The exact syntax of the ifconfig and route commands differs from
platform to platform. You can look up the commands for setting
addresses and adding routes in *note Platform specific information::,
but it is best to consult the manpages of those utilities on your
platform.

File: tinc.info, Node: Example configuration, Prev: Network interfaces, Up: Configuration
4.6 Example configuration
=========================
Imagine the following situation. Branch A of our example `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.
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
Here, "gateway" is the VPN IP address of the machine that is running
the tincd, and "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 and
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. All branches use the
netname `company' for this particular VPN.
Each branch is set up using the `tincctl init' and `tincctl config'
commands, here we just show the end results:
For Branch A
............
_BranchA_ would be configured like this:
In `/etc/tinc/company/tinc-up':
#!/bin/sh
# Real interface of internal network:
# ifconfig eth0 10.1.54.1 netmask 255.255.0.0
ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
and in `/etc/tinc/company/tinc.conf':
Name = BranchA
On all hosts, `/etc/tinc/company/hosts/BranchA' contains:
Subnet = 10.1.0.0/16
Address = 1.2.3.4
-----BEGIN RSA PUBLIC KEY-----
...
-----END RSA PUBLIC KEY-----
Note that the IP addresses of eth0 and the VPN interface are the
same. This is quite possible, if you make sure that the netmasks of
the interfaces are different. It is in fact recommended to give both
real internal network interfaces and VPN interfaces the same IP address,
since that will make things a lot easier to remember and set up.
For Branch B
............
In `/etc/tinc/company/tinc-up':
#!/bin/sh
# Real interface of internal network:
# ifconfig eth0 10.2.43.8 netmask 255.255.0.0
ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
and in `/etc/tinc/company/tinc.conf':
Name = BranchB
ConnectTo = BranchA
Note here that the internal address (on eth0) doesn't have to be the
same as on the VPN interface. Also, ConnectTo is given so that this
node will always try to connect to BranchA.
On all hosts, in `/etc/tinc/company/hosts/BranchB':
Subnet = 10.2.0.0/16
Address = 2.3.4.5
-----BEGIN RSA PUBLIC KEY-----
...
-----END RSA PUBLIC KEY-----
For Branch C
............
In `/etc/tinc/company/tinc-up':
#!/bin/sh
# Real interface of internal network:
# ifconfig eth0 10.3.69.254 netmask 255.255.0.0
ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
and in `/etc/tinc/company/tinc.conf':
Name = BranchC
ConnectTo = BranchA
C already has another daemon that runs on port 655, so they have to
reserve another port for tinc. It knows the portnumber it has to listen
on from it's own host configuration file.
On all hosts, in `/etc/tinc/company/hosts/BranchC':
Address = 3.4.5.6
Subnet = 10.3.0.0/16
Port = 2000
-----BEGIN RSA PUBLIC KEY-----
...
-----END RSA PUBLIC KEY-----
For Branch D
............
In `/etc/tinc/company/tinc-up':
#!/bin/sh
# Real interface of internal network:
# ifconfig eth0 10.4.3.32 netmask 255.255.0.0
ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
and in `/etc/tinc/company/tinc.conf':
Name = BranchD
ConnectTo = BranchC
D will be connecting to C, which has a tincd running for this
network on port 2000. It knows the port number from the host
configuration file.
On all hosts, in `/etc/tinc/company/hosts/BranchD':
Subnet = 10.4.0.0/16
Address = 4.5.6.7
-----BEGIN RSA PUBLIC KEY-----
...
-----END RSA PUBLIC KEY-----
Key files
.........
A, B, C and D all have their own public/private keypairs:
The private RSA key is stored in `/etc/tinc/company/rsa_key.priv',
the private ECDSA key is stored in `/etc/tinc/company/ecdsa_key.priv',
and the public RSA and ECDSA keys are put into the host configuration
file in the `/etc/tinc/company/hosts/' directory.
Starting
........
After each branch has finished configuration and they have distributed
the host configuration files amongst them, they can start their tinc
daemons. They don't necessarily have to wait for the other branches to
have started their daemons, tinc will try connecting until they are
available.

File: tinc.info, Node: Running tinc, Next: Controlling tinc, Prev: Configuration, Up: Top
5 Running tinc
**************
If everything else is done, you can start tinc by typing the following
command:
tincctl -n NETNAME start
Tinc will detach from the terminal and continue to run in the
background like a good daemon. If there are any problems however you
can try to increase the debug level and look in the syslog to find out
what the problems are.
* Menu:
* Runtime options::
* Signals::
* Debug levels::
* Solving problems::
* Error messages::
* Sending bug reports::

File: tinc.info, Node: Runtime options, Next: Signals, Up: Running tinc
5.1 Runtime options
===================
Besides the settings in the configuration file, tinc also accepts some
command line options.
`-c, --config=PATH'
Read configuration options from the directory PATH. The default is
`/etc/tinc/NETNAME/'.
`-D, --no-detach'
Don't fork and detach. This will also disable the automatic
restart mechanism for fatal errors.
`-d, --debug=LEVEL'
Set debug level to LEVEL. The higher the debug level, the more
gets logged. Everything goes via syslog.
`-n, --net=NETNAME'
Use configuration for net NETNAME. This will let tinc read all
configuration files from `/etc/tinc/NETNAME/'. Specifying . for
NETNAME is the same as not specifying any NETNAME. *Note Multiple
networks::.
`--pidfile=FILENAME'
Store a cookie in FILENAME which allows tincctl to authenticate.
If unspecified, the default is `/var/run/tinc.NETNAME.pid'.
`-o, --option=[HOST.]KEY=VALUE'
Without specifying a HOST, this will set server configuration
variable KEY to VALUE. If specified as HOST.KEY=VALUE, this will
set the host configuration variable KEY of the host named HOST to
VALUE. This option can be used more than once to specify multiple
configuration variables.
`-L, --mlock'
Lock tinc into main memory. This will prevent sensitive data like
shared private keys to be written to the system swap
files/partitions.
`--logfile[=FILE]'
Write log entries to a file instead of to the system logging
facility. If FILE is omitted, the default is
`/var/log/tinc.NETNAME.log'.
`--bypass-security'
Disables encryption and authentication. Only useful for debugging.
`-R, --chroot'
Change process root directory to the directory where the config
file is located (`/etc/tinc/NETNAME/' as determined by -n/-net
option or as given by -c/-config option), for added security. The
chroot is performed after all the initialization is done, after
writing pid files and opening network sockets.
Note that this option alone does not do any good without -U/-user,
below.
Note also that tinc can't run scripts anymore (such as tinc-down
or host-up), unless it's setup to be runnable inside chroot
environment.
`-U, --user=USER'
Switch to the given USER after initialization, at the same time as
chroot is performed (see -chroot above). With this option tinc
drops privileges, for added security.
`--help'
Display a short reminder of these runtime options and terminate.
`--version'
Output version information and exit.

File: tinc.info, Node: Signals, Next: Debug levels, Prev: Runtime options, Up: Running tinc
5.2 Signals
===========
You can also send the following signals to a running tincd process:
`ALRM'
Forces tinc to try to connect to all uplinks immediately. Usually
tinc attempts to do this itself, but increases the time it waits
between the attempts each time it failed, and if tinc didn't
succeed to connect to an uplink the first time after it started,
it defaults to the maximum time of 15 minutes.
`HUP'
Partially rereads configuration files. Connections to hosts whose
host config file are removed are closed. New outgoing connections
specified in `tinc.conf' will be made. If the -logfile option is
used, this will also close and reopen the log file, useful when
log rotation is used.

File: tinc.info, Node: Debug levels, Next: Solving problems, Prev: Signals, Up: Running tinc
5.3 Debug levels
================
The tinc daemon can send a lot of messages to the syslog. The higher
the debug level, the more messages it will log. Each level inherits
all messages of the previous level:
`0'
This will log a message indicating tinc has started along with a
version number. It will also log any serious error.
`1'
This will log all connections that are made with other tinc
daemons.
`2'
This will log status and error messages from scripts and other
tinc daemons.
`3'
This will log all requests that are exchanged with other tinc
daemons. These include authentication, key exchange and connection
list updates.
`4'
This will log a copy of everything received on the meta socket.
`5'
This will log all network traffic over the virtual private network.

File: tinc.info, Node: Solving problems, Next: Error messages, Prev: Debug levels, Up: Running tinc
5.4 Solving problems
====================
If tinc starts without problems, but if the VPN doesn't work, you will
have to find the cause of the problem. The first thing to do is to
start tinc with a high debug level in the foreground, so you can
directly see everything tinc logs:
tincd -n NETNAME -d5 -D
If tinc does not log any error messages, then you might want to
check the following things:
* `tinc-up' script Does this script contain the right commands?
Normally you must give the interface the address of this host on
the VPN, and the netmask must be big enough so that the entire VPN
is covered.
* Subnet Does the Subnet (or Subnets) in the host configuration file
of this host match the portion of the VPN that belongs to this
host?
* Firewalls and NATs Do you have a firewall or a NAT device (a
masquerading firewall or perhaps an ADSL router that performs
masquerading)? If so, check that it allows TCP and UDP traffic on
port 655. If it masquerades and the host running tinc is behind
it, make sure that it forwards TCP and UDP traffic to port 655 to
the host running tinc. You can add `TCPOnly = yes' to your host
config file to force tinc to only use a single TCP connection,
this works through most firewalls and NATs.

File: tinc.info, Node: Error messages, Next: Sending bug reports, Prev: Solving problems, Up: Running tinc
5.5 Error messages
==================
What follows is a list of the most common error messages you might find
in the logs. Some of them will only be visible if the debug level is
high enough.
`Could not open /dev/tap0: No such device'
* You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
* You forgot to compile `Netlink device emulation' in the
kernel.
`Can't write to /dev/net/tun: No such device'
* You forgot to `modprobe tun'.
* You forgot to compile `Universal TUN/TAP driver' in the
kernel.
* The tun device is located somewhere else in `/dev/'.
`Network address and prefix length do not match!'
* The Subnet field must contain a _network_ address, trailing
bits should be 0.
* If you only want to use one IP address, set the netmask to
/32.
`Error reading RSA key file `rsa_key.priv': No such file or directory'
* You forgot to create a public/private keypair.
* Specify the complete pathname to the private key file with
the `PrivateKeyFile' option.
`Warning: insecure file permissions for RSA private key file `rsa_key.priv'!'
* The private key file is readable by users other than root.
Use chmod to correct the file permissions.
`Creating metasocket failed: Address family not supported'
* By default tinc tries to create both IPv4 and IPv6 sockets.
On some platforms this might not be implemented. If the logs
show `Ready' later on, then at least one metasocket was
created, and you can ignore this message. You can add
`AddressFamily = ipv4' to `tinc.conf' to prevent this from
happening.
`Cannot route packet: unknown IPv4 destination 1.2.3.4'
* You try to send traffic to a host on the VPN for which no
Subnet is known.
* If it is a broadcast address (ending in .255), it probably is
a samba server or a Windows host sending broadcast packets.
You can ignore it.
`Cannot route packet: ARP request for unknown address 1.2.3.4'
* You try to send traffic to a host on the VPN for which no
Subnet is known.
`Packet with destination 1.2.3.4 is looping back to us!'
* Something is not configured right. Packets are being sent out
to the virtual network 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
prefix length which is just as large as the prefix of the
virtual network interface. 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!
* Chances are that a `Subnet = ...' line in the host
configuration file of this tinc daemon is wrong. Change it
to a subnet that is accepted locally by another interface, or
if that is not the case, try changing the prefix length into
/32.
`Node foo (1.2.3.4) is not reachable'
* Node foo does not have a connection anymore, its tinc daemon
is not running or its connection to the Internet is broken.
`Received UDP packet from unknown source 1.2.3.4 (port 12345)'
* If you see this only sporadically, it is harmless and caused
by a node sending packets using an old key.
* If you see this often and another node is not reachable
anymore, then a NAT (masquerading firewall) is changing the
source address of UDP packets. You can add `TCPOnly = yes'
to host configuration files to force all VPN traffic to go
over a TCP connection.
`Got bad/bogus/unauthorized REQUEST from foo (1.2.3.4 port 12345)'
* Node foo does not have the right public/private keypair.
Generate new keypairs and distribute them again.
* An attacker tries to gain access to your VPN.
* A network error caused corruption of metadata sent from foo.

File: tinc.info, Node: Sending bug reports, Prev: Error messages, Up: Running tinc
5.6 Sending bug reports
=======================
If you really can't find the cause of a problem, or if you suspect tinc
is not working right, you can send us a bugreport, see *note Contact
information::. Be sure to include the following information in your
bugreport:
* A clear description of what you are trying to achieve and what the
problem is.
* What platform (operating system, version, hardware architecture)
and which version of tinc you use.
* If compiling tinc fails, a copy of `config.log' and the error
messages you get.
* Otherwise, a copy of `tinc.conf', `tinc-up' and all files in the
`hosts/' directory.
* The output of the commands `ifconfig -a' and `route -n' (or
`netstat -rn' if that doesn't work).
* The output of any command that fails to work as it should (like
ping or traceroute).

File: tinc.info, Node: Controlling tinc, Next: Technical information, Prev: Running tinc, Up: Top
6 Controlling tinc
******************
You can control and inspect a running tincd through the tincctl
command. A quick example:
tincctl -n NETNAME reload
* Menu:
* tincctl runtime options::
* tincctl environment variables::
* tincctl commands::
* tincctl examples::
* tincctl top::

File: tinc.info, Node: tincctl runtime options, Next: tincctl environment variables, Up: Controlling tinc
6.1 tincctl runtime options
===========================
`-c, --config=PATH'
Read configuration options from the directory PATH. The default is
`/etc/tinc/NETNAME/'.
`-n, --net=NETNAME'
Use configuration for net NETNAME. *Note Multiple networks::.
`--pidfile=FILENAME'
Use the cookie from FILENAME to authenticate with a running tinc
daemon. If unspecified, the default is
`/var/run/tinc.NETNAME.pid'.
`--help'
Display a short reminder of runtime options and commands, then
terminate.
`--version'
Output version information and exit.

File: tinc.info, Node: tincctl environment variables, Next: tincctl commands, Prev: tincctl runtime options, Up: Controlling tinc
6.2 tincctl environment variables
=================================
`NETNAME'
If no netname is specified on the command line with the `-n'
option, the value of this environment variable is used.

File: tinc.info, Node: tincctl commands, Next: tincctl examples, Prev: tincctl environment variables, Up: Controlling tinc
6.3 tincctl commands
====================
`init [NAME]'
Create initial configuration files and RSA and ECDSA keypairs with
default length. If no NAME for this node is given, it will be
asked for.
`config [get] VARIABLE'
Print the current value of configuration variable VARIABLE. If
more than one variable with the same name exists, the value of
each of them will be printed on a separate line.
`config [set] VARIABLE VALUE'
Set configuration variable VARIABLE to the given VALUE. All
previously existing configuration variables with the same name are
removed. To set a variable for a specific host, use the notation
HOST.VARIABLE.
`config add VARIABLE VALUE'
As above, but without removing any previously existing
configuration variables.
`config del VARIABLE [VALUE]'
Remove configuration variables with the same name and VALUE. If
no VALUE is given, all configuration variables with the same name
will be removed.
`edit FILENAME'
Start an editor for the given configuration file. You do not need
to specify the full path to the file.
`export'
Export the host configuration file of the local node to standard
output.
`export-all'
Export all host configuration files to standard output.
`import [--force]'
Import host configuration file(s) from standard input. Already
existing host configuration files are not overwritten unless the
option -force is used.
`start [tincd options]'
Start `tincd', optionally with the given extra options.
`stop'
Stop `tincd'.
`restart'
Restart `tincd'.
`reload'
Partially rereads configuration files. Connections to hosts whose
host config files are removed are closed. New outgoing connections
specified in `tinc.conf' will be made.
`pid'
Shows the PID of the currently running `tincd'.
`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).
`dump nodes'
Dump a list of all known nodes in the VPN.
`dump edges'
Dump a list of all known connections in the VPN.
`dump subnets'
Dump a list of all known subnets in the VPN.
`dump connections'
Dump a list of all meta connections with ourself.
`dump graph | digraph'
Dump a graph of the VPN in dotty format. Nodes are colored
according to their reachability: red nodes are unreachable, orange
nodes are indirectly reachable, green nodes are directly reachable.
Black nodes are either directly or indirectly reachable, but
direct reachability has not been tried yet.
`info NODE | SUBNET | ADDRESS'
Show information about a particular NODE, SUBNET or ADDRESS. If
an ADDRESS is given, any matching subnet will be shown.
`purge'
Purges all information remembered about unreachable nodes.
`debug LEVEL'
Sets debug level to LEVEL.
`log [LEVEL]'
Capture log messages from a running tinc daemon. An optional
debug level can be given that will be applied only for log
messages sent to tincctl.
`retry'
Forces tinc to try to connect to all uplinks immediately. Usually
tinc attempts to do this itself, but increases the time it waits
between the attempts each time it failed, and if tinc didn't
succeed to connect to an uplink the first time after it started,
it defaults to the maximum time of 15 minutes.
`disconnect NODE'
Closes the meta connection with the given NODE.
`top'
If tincctl is compiled with libcurses support, this will display
live traffic statistics for all the known nodes, similar to the
UNIX top command. See below for more information.
`pcap'
Dump VPN traffic going through the local tinc node in
pcap-savefile format to standard output, from where it can be
redirected to a file or piped through a program that can parse it
directly, such as tcpdump.

File: tinc.info, Node: tincctl examples, Next: tincctl top, Prev: tincctl commands, Up: Controlling tinc
6.4 tincctl examples
====================
Examples of some commands:
tincctl -n vpn dump graph | circo -Txlib
tincctl -n vpn pcap | tcpdump -r -
tincctl -n vpn top
Example of configuring tinc using tincctl:
tincctl -n vpn init foo
tincctl -n vpn config Subnet 192.168.1.0/24
tincctl -n vpn config bar.Address bar.example.com
tincctl -n vpn config ConnectTo bar
tincctl -n vpn export | gpg --clearsign | mail -s "My config" vpnmaster@example.com

File: tinc.info, Node: tincctl top, Prev: tincctl examples, Up: Controlling tinc
6.5 tincctl top
===============
The top command connects to a running tinc daemon and repeatedly
queries its per-node traffic counters. It displays a list of all the
known nodes in the left-most column, and the amount of bytes and
packets read from and sent to each node in the other columns. By
default, the information is updated every second. The behaviour of the
top command can be changed using the following keys:
<s>
Change the interval between updates. After pressing the <s> key,
enter the desired interval in seconds, followed by enter.
Fractional seconds are honored. Intervals lower than 0.1 seconds
are not allowed.
<c>
Toggle between displaying current traffic rates (in packets and
bytes per second) and cummulative traffic (total packets and bytes
since the tinc daemon started).
<n>
Sort the list of nodes by name.
<i>
Sort the list of nodes by incoming amount of bytes.
<I>
Sort the list of nodes by incoming amount of packets.
<o>
Sort the list of nodes by outgoing amount of bytes.
<O>
Sort the list of nodes by outgoing amount of packets.
<t>
Sort the list of nodes by sum of incoming and outgoing amount of
bytes.
<T>
Sort the list of nodes by sum of incoming and outgoing amount of
packets.
<b>
Show amount of traffic in bytes.
<k>
Show amount of traffic in kilobytes.
<M>
Show amount of traffic in megabytes.
<G>
Show amount of traffic in gigabytes.
<q>
Quit.

File: tinc.info, Node: Technical information, Next: Platform specific information, Prev: Controlling tinc, Up: Top
7 Technical information
***********************
* Menu:
* The connection::
* The meta-protocol::
* Security::

File: tinc.info, Node: The connection, Next: The meta-protocol, Up: Technical information
7.1 The connection
==================
Tinc is a daemon that takes VPN data and transmit that to another host
computer over the existing Internet infrastructure.
* Menu:
* The UDP tunnel::
* The meta-connection::

File: tinc.info, Node: The UDP tunnel, Next: The meta-connection, Up: The connection
7.1.1 The UDP tunnel
--------------------
The data itself is read from a character device file, the so-called
_virtual network 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. There
are two possible types of virtual network devices: `tun' style, which
are point-to-point devices which can only handle IPv4 and/or IPv6
packets, and `tap' style, which are Ethernet devices and handle
complete Ethernet frames.
So when tinc reads an Ethernet frame from the device, it determines
its type. When tinc is in it's default routing mode, it can handle IPv4
and IPv6 packets. Depending on the Subnet lines, it will send the
packets off to their destination IP address. In the `switch' and `hub'
mode, tinc will use broadcasts and MAC address discovery to deduce the
destination of the packets. Since the latter modes only depend on the
link layer information, any protocol that runs over Ethernet is
supported (for instance IPX and Appletalk). However, only `tap' style
devices provide this information.
After the destination has been determined, the packet will be
compressed (optionally), a sequence number will be added to the packet,
the packet will then be encrypted and a message authentication code
will be appended.
When that is done, 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 _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 checks the message authentication code,
decrypts the contents of the UDP datagram, checks the sequence number
and writes the decrypted information to its own virtual network device.
If the virtual network device is a `tun' device (a point-to-point
tunnel), there is no problem for the kernel to accept a packet.
However, if it is a `tap' device (this is the only available type on
FreeBSD), the destination MAC address must match that of the virtual
network interface. If tinc is in it's default routing mode, ARP does
not work, so the correct destination MAC can not be known by the
sending host. Tinc solves this by letting the receiving end detect the
MAC address of its own virtual network interface and overwriting the
destination MAC address of the received packet.
In switch or hub modes ARP does work so the sender already knows the
correct destination MAC address. In those modes every interface should
have a unique MAC address, so make sure they are not the same. Because
switch and hub modes rely on MAC addresses to function correctly, these
modes cannot be used on the following operating systems which don't
have a `tap' style virtual network device: OpenBSD, NetBSD, Darwin and
Solaris.

File: tinc.info, Node: The meta-connection, Prev: The UDP tunnel, Up: The connection
7.1.2 The meta-connection
-------------------------
Having only a 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 session key 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.
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 ACKs sent instead of just one. Furthermore, if there would be a
timeout, both TCP streams would sense the timeout, and both would start
re-sending packets.

File: tinc.info, Node: The meta-protocol, Next: Security, Prev: The connection, Up: Technical information
7.2 The meta-protocol
=====================
The meta protocol is used to tie all tinc daemons together, and
exchange information about which tinc daemon serves which virtual
subnet.
The meta protocol consists of requests that can be sent to the other
side. Each request has a unique number and several parameters. All
requests are represented in the standard ASCII character set. It is
possible to use tools such as telnet or netcat to connect to a tinc
daemon started with the -bypass-security option and to read and write
requests by hand, provided that one understands the numeric codes sent.
The authentication scheme is described in *note Authentication
protocol::. After a successful authentication, the server and the
client will exchange all the information about other tinc daemons and
subnets they know of, so that both sides (and all the other tinc
daemons behind them) have their information synchronised.
message
------------------------------------------------------------------
ADD_EDGE node1 node2 21.32.43.54 655 222 0
| | | | | +-> options
| | | | +----> weight
| | | +--------> UDP port of node2
| | +----------------> real address of node2
| +-------------------------> name of destination node
+-------------------------------> name of source node
ADD_SUBNET node 192.168.1.0/24
| | +--> prefixlength
| +--------> network address
+------------------> owner of this subnet
------------------------------------------------------------------
The ADD_EDGE messages are to inform other tinc daemons that a
connection between two nodes exist. The address of the destination node
is available so that VPN packets can be sent directly to that node.
The ADD_SUBNET messages inform other tinc daemons that certain
subnets belong to certain nodes. tinc will use it to determine to which
node a VPN packet has to be sent.
message
------------------------------------------------------------------
DEL_EDGE node1 node2
| +----> name of destination node
+----------> name of source node
DEL_SUBNET node 192.168.1.0/24
| | +--> prefixlength
| +--------> network address
+------------------> owner of this subnet
------------------------------------------------------------------
In case a connection between two daemons is closed or broken,
DEL_EDGE messages are sent to inform the other daemons of that fact.
Each daemon will calculate a new route to the the daemons, or mark them
unreachable if there isn't any.
message
------------------------------------------------------------------
REQ_KEY origin destination
| +--> name of the tinc daemon it wants the key from
+----------> name of the daemon that wants the key
ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
| | \______________/ | | +--> MAC length
| | | | +-----> digest algorithm
| | | +--------> cipher algorithm
| | +--> 128 bits key
| +--> name of the daemon that wants the key
+----------> name of the daemon that uses this key
KEY_CHANGED origin
+--> daemon that has changed it's packet key
------------------------------------------------------------------
The keys used to encrypt VPN packets are not sent out directly. This
is because it would generate a lot of traffic on VPNs with many
daemons, and chances are that not every tinc daemon will ever send a
packet to every other daemon. Instead, if a daemon needs a key it sends
a request for it via the meta connection of the nearest hop in the
direction of the destination.
daemon message
------------------------------------------------------------------
origin PING
dest. PONG
------------------------------------------------------------------
There is also a mechanism to check if hosts are still alive. Since
network failures or a crash can cause a daemon to be killed without
properly shutting down the TCP connection, this is necessary to keep an
up to date connection list. PINGs are sent at regular intervals, except
when there is also some other traffic. A little bit of salt (random
data) is added with each PING and PONG message, to make sure that long
sequences of PING/PONG messages without any other traffic won't result
in known plaintext.
This basically covers what is sent over the meta connection by tinc.

File: tinc.info, Node: Security, Prev: The meta-protocol, Up: Technical information
7.3 Security
============
Tinc got its name from "TINC," short for _There Is No Cabal_; the
alleged Cabal was/is an organisation that was said to keep an eye on the
entire Internet. As this is exactly what you _don't_ want, we named
the tinc project after TINC.
But in order to be "immune" to eavesdropping, you'll have to encrypt
your data. Because tinc is a _Secure_ VPN (SVPN) daemon, it does
exactly that: encrypt. Tinc by default uses blowfish encryption with
128 bit keys in CBC mode, 32 bit sequence numbers and 4 byte long
message authentication codes to make sure eavesdroppers cannot get and
cannot change any information at all from the packets they can
intercept. The encryption algorithm and message authentication
algorithm can be changed in the configuration. The length of the message
authentication codes is also adjustable. The length of the key for the
encryption algorithm is always the default length used by OpenSSL.
* Menu:
* Authentication protocol::
* Encryption of network packets::
* Security issues::

File: tinc.info, Node: Authentication protocol, Next: Encryption of network packets, Up: Security
7.3.1 Authentication protocol
-----------------------------
A new scheme for authentication in tinc has been devised, which offers
some improvements over the protocol used in 1.0pre2 and 1.0pre3.
Explanation is below.
daemon message
--------------------------------------------------------------------------
client <attempts connection>
server <accepts connection>
client ID client 12
| +---> version
+-------> name of tinc daemon
server ID server 12
| +---> version
+-------> name of tinc daemon
client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
\_________________________________/
+-> RSAKEYLEN bits totally random string S1,
encrypted with server's public RSA key
server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
\_________________________________/
+-> RSAKEYLEN bits totally random string S2,
encrypted with client's public RSA key
From now on:
- the client will symmetrically encrypt outgoing traffic using S1
- the server will symmetrically encrypt outgoing traffic using S2
client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
\_________________________________/
+-> CHALLEN bits totally random string H1
server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
\_________________________________/
+-> CHALLEN bits totally random string H2
client CHAL_REPLY 816a86
+-> 160 bits SHA1 of H2
server CHAL_REPLY 928ffe
+-> 160 bits SHA1 of H1
After the correct challenge replies are received, both ends have proved
their identity. Further information is exchanged.
client ACK 655 123 0
| | +-> options
| +----> estimated weight
+--------> listening port of client
server ACK 655 321 0
| | +-> options
| +----> estimated weight
+--------> listening port of server
--------------------------------------------------------------------------
This new scheme has several improvements, both in efficiency and
security.
First of all, the server sends exactly the same kind of messages
over the wire as the client. The previous versions of tinc first
authenticated the client, and then the server. This scheme even allows
both sides to send their messages simultaneously, there is no need to
wait for the other to send something first. This means that any
calculations that need to be done upon sending or receiving a message
can also be done in parallel. This is especially important when doing
RSA encryption/decryption. Given that these calculations are the main
part of the CPU time spent for the authentication, speed is improved by
a factor 2.
Second, only one RSA encrypted message is sent instead of two. This
reduces the amount of information attackers can see (and thus use for a
cryptographic attack). It also improves speed by a factor two, making
the total speedup a factor 4.
Third, and most important: The symmetric cipher keys are exchanged
first, the challenge is done afterwards. In the previous authentication
scheme, because a man-in-the-middle could pass the challenge/chal_reply
phase (by just copying the messages between the two real tinc daemons),
but no information was exchanged that was really needed to read the
rest of the messages, the challenge/chal_reply phase was of no real
use. The man-in-the-middle was only stopped by the fact that only after
the ACK messages were encrypted with the symmetric cipher. Potentially,
it could even send it's own symmetric key to the server (if it knew the
server's public key) and read some of the metadata the server would
send it (it was impossible for the mitm to read actual network packets
though). The new scheme however prevents this.
This new scheme makes sure that first of all, symmetric keys are
exchanged. The rest of the messages are then encrypted with the
symmetric cipher. Then, each side can only read received messages if
they have their private key. The challenge is there to let the other
side know that the private key is really known, because a challenge
reply can only be sent back if the challenge is decrypted correctly,
and that can only be done with knowledge of the private key.
Fourth: the first thing that is sent via the symmetric cipher
encrypted connection is a totally random string, so that there is no
known plaintext (for an attacker) in the beginning of the encrypted
stream.

File: tinc.info, Node: Encryption of network packets, Next: Security issues, Prev: Authentication protocol, Up: Security
7.3.2 Encryption of network packets
-----------------------------------
A data packet can only be sent if the encryption key is known to both
parties, and the connection is activated. If the encryption key is not
known, a request is sent to the destination using the meta connection
to retrieve it. The packet is stored in a queue while waiting for the
key to arrive.
The UDP packet containing the network packet from the VPN has the
following layout:
... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
\___________________/\_____/
| |
V +---> digest algorithm
Encrypted with symmetric cipher
So, the entire VPN packet is encrypted using a symmetric cipher,
including a 32 bits sequence number that is added in front of the
actual VPN packet, to act as a unique IV for each packet and to prevent
replay attacks. A message authentication code is added to the UDP
packet to prevent alteration of packets. By default the first 4 bytes
of the digest are used for this, but this can be changed using the
MACLength configuration variable.

File: tinc.info, Node: Security issues, Prev: Encryption of network packets, Up: Security
7.3.3 Security issues
---------------------
In August 2000, we discovered the existence of a security hole in all
versions of tinc up to and including 1.0pre2. This had to do with the
way we exchanged keys. Since then, we have been working on a new
authentication scheme to make tinc as secure as possible. The current
version uses the OpenSSL library and uses strong authentication with
RSA keys.
On the 29th of December 2001, Jerome Etienne posted a security
analysis of tinc 1.0pre4. Due to a lack of sequence numbers and a
message authentication code for each packet, an attacker could possibly
disrupt certain network services or launch a denial of service attack
by replaying intercepted packets. The current version adds sequence
numbers and message authentication codes to prevent such attacks.
On the 15th of September 2003, Peter Gutmann posted a security
analysis of tinc 1.0.1. He argues that the 32 bit sequence number used
by tinc is not a good IV, that tinc's default length of 4 bytes for the
MAC is too short, and he doesn't like tinc's use of RSA during
authentication. We do not know of a security hole in this version of
tinc, but tinc's security is not as strong as TLS or IPsec. We will
address these issues in tinc 2.0.
Cryptography is a hard thing to get right. We cannot make any
guarantees. Time, review and feedback are the only things that can
prove the security of any cryptographic product. If you wish to review
tinc or give us feedback, you are stronly encouraged to do so.

File: tinc.info, Node: Platform specific information, Next: About us, Prev: Technical information, Up: Top
8 Platform specific information
*******************************
* Menu:
* Interface configuration::
* Routes::

File: tinc.info, Node: Interface configuration, Next: Routes, Up: Platform specific information
8.1 Interface configuration
===========================
When configuring an interface, one normally assigns it an address and a
netmask. The address uniquely identifies the host on the network
attached to the interface. The netmask, combined with the address,
forms a subnet. It is used to add a route to the routing table
instructing the kernel to send all packets which fall into that subnet
to that interface. Because all packets for the entire VPN should go to
the virtual network interface used by tinc, the netmask should be such
that it encompasses the entire VPN.
For IPv4 addresses:
Linux `ifconfig' INTERFACE ADDRESS `netmask' NETMASK
Linux iproute2 `ip addr add' ADDRESS`/'PREFIXLENGTH `dev' INTERFACE
FreeBSD `ifconfig' INTERFACE ADDRESS `netmask' NETMASK
OpenBSD `ifconfig' INTERFACE ADDRESS `netmask' NETMASK
NetBSD `ifconfig' INTERFACE ADDRESS `netmask' NETMASK
Solaris `ifconfig' INTERFACE ADDRESS `netmask' NETMASK
Darwin (MacOS/X) `ifconfig' INTERFACE ADDRESS `netmask' NETMASK
Windows `netsh interface ip set address' INTERFACE `static' ADDRESS NETMASK
For IPv6 addresses:
Linux `ifconfig' INTERFACE `add' ADDRESS`/'PREFIXLENGTH
FreeBSD `ifconfig' INTERFACE `inet6' ADDRESS `prefixlen' PREFIXLENGTH
OpenBSD `ifconfig' INTERFACE `inet6' ADDRESS `prefixlen' PREFIXLENGTH
NetBSD `ifconfig' INTERFACE `inet6' ADDRESS `prefixlen' PREFIXLENGTH
Solaris `ifconfig' INTERFACE `inet6 plumb up'
`ifconfig' INTERFACE `inet6 addif' ADDRESS ADDRESS
Darwin (MacOS/X) `ifconfig' INTERFACE `inet6' ADDRESS `prefixlen' PREFIXLENGTH
Windows `netsh interface ipv6 add address' INTERFACE `static' ADDRESS/PREFIXLENGTH
On some platforms, when running tinc in switch mode, the VPN
interface must be set to tap mode with an ifconfig command:
OpenBSD `ifconfig' INTERFACE `link0'
On Linux, it is possible to create a persistent tun/tap interface
which will continue to exist even if tinc quit, although this is
normally not required. It can be useful to set up a tun/tap interface
owned by a non-root user, so tinc can be started without needing any
root privileges at all.
Linux `ip tuntap add dev' INTERFACE `mode' TUN|TAP `user' USERNAME

File: tinc.info, Node: Routes, Prev: Interface configuration, Up: Platform specific information
8.2 Routes
==========
In some cases it might be necessary to add more routes to the virtual
network interface. There are two ways to indicate which interface a
packet should go to, one is to use the name of the interface itself,
another way is to specify the (local) address that is assigned to that
interface (LOCAL_ADDRESS). The former way is unambiguous and therefore
preferable, but not all platforms support this.
Adding routes to IPv4 subnets:
Linux `route add -net' NETWORK_ADDRESS `netmask' NETMASK INTERFACE
Linux iproute2 `ip route add' NETWORK_ADDRESS`/'PREFIXLENGTH `dev' INTERFACE
FreeBSD `route add' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS
OpenBSD `route add' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS
NetBSD `route add' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS
Solaris `route add' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS `-interface'
Darwin (MacOS/X) `route add' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS
Windows `netsh routing ip add persistentroute' NETWORK_ADDRESS NETMASK INTERFACE
LOCAL_ADDRESS
Adding routes to IPv6 subnets:
Linux `route add -A inet6' NETWORK_ADDRESS`/'PREFIXLENGTH INTERFACE
Linux iproute2 `ip route add' NETWORK_ADDRESS`/'PREFIXLENGTH `dev' INTERFACE
FreeBSD `route add -inet6' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS
OpenBSD `route add -inet6' NETWORK_ADDRESS LOCAL_ADDRESS `-prefixlen' PREFIXLENGTH
NetBSD `route add -inet6' NETWORK_ADDRESS LOCAL_ADDRESS `-prefixlen' PREFIXLENGTH
Solaris `route add -inet6' NETWORK_ADDRESS`/'PREFIXLENGTH LOCAL_ADDRESS `-interface'
Darwin (MacOS/X) ?
Windows `netsh interface ipv6 add route' NETWORK ADDRESS/PREFIXLENGTH INTERFACE

File: tinc.info, Node: About us, Next: Concept Index, Prev: Platform specific information, Up: Top
9 About us
**********
* Menu:
* Contact information::
* Authors::

File: tinc.info, Node: Contact information, Next: Authors, Up: About us
9.1 Contact information
=======================
Tinc's website is at `http://www.tinc-vpn.org/', this server is located
in the Netherlands.
We have an IRC channel on the FreeNode and OFTC IRC networks.
Connect to irc.freenode.net (http://www.freenode.net/) or irc.oftc.net
(http://www.oftc.net/) and join channel #tinc.

File: tinc.info, Node: Authors, Prev: Contact information, Up: About us
9.2 Authors
===========
Ivo Timmermans (zarq)
Guus Sliepen (guus) (<guus@tinc-vpn.org>)
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 `THANKS' in
the source distribution.

File: tinc.info, Node: Concept Index, Prev: About us, Up: Top
Concept Index
*************
[index]
* Menu:
* ACK: Authentication protocol.
(line 10)
* ADD_EDGE: The meta-protocol. (line 23)
* ADD_SUBNET: The meta-protocol. (line 23)
* Address: Host configuration variables.
(line 6)
* AddressFamily: Main configuration variables.
(line 6)
* ANS_KEY: The meta-protocol. (line 64)
* authentication: Authentication protocol.
(line 6)
* binary package: Building and installing tinc.
(line 9)
* BindToAddress: Main configuration variables.
(line 12)
* BindToInterface: Main configuration variables.
(line 23)
* Broadcast: Main configuration variables.
(line 34)
* Cabal: Security. (line 6)
* CHAL_REPLY: Authentication protocol.
(line 10)
* CHALLENGE: Authentication protocol.
(line 10)
* CIDR notation: Host configuration variables.
(line 91)
* Cipher: Host configuration variables.
(line 12)
* ClampMSS: Host configuration variables.
(line 18)
* client: How connections work.
(line 18)
* command line: Runtime options. (line 9)
* Compression: Host configuration variables.
(line 24)
* connection: The connection. (line 6)
* ConnectTo: Main configuration variables.
(line 54)
* daemon: Running tinc. (line 11)
* data-protocol: The meta-connection. (line 18)
* debug level: Runtime options. (line 17)
* debug levels: Debug levels. (line 6)
* DecrementTTL: Main configuration variables.
(line 65)
* DEL_EDGE: The meta-protocol. (line 47)
* DEL_SUBNET: The meta-protocol. (line 47)
* DEVICE: Scripts. (line 55)
* Device: Main configuration variables.
(line 74)
* device files: Device files. (line 6)
* DeviceType: Main configuration variables.
(line 81)
* Digest: Host configuration variables.
(line 29)
* DirectOnly: Main configuration variables.
(line 146)
* dummy: Main configuration variables.
(line 88)
* ECDSAPrivateKeyFile: Main configuration variables.
(line 153)
* encapsulating: The UDP tunnel. (line 30)
* encryption: Encryption of network packets.
(line 6)
* environment variables: Scripts. (line 43)
* example: Example configuration.
(line 6)
* exec: Main configuration variables.
(line 326)
* ExperimentalProtocol: Main configuration variables.
(line 157)
* Forwarding: Main configuration variables.
(line 166)
* frame type: The UDP tunnel. (line 6)
* GraphDumpFile: Main configuration variables.
(line 186)
* Hostnames: Main configuration variables.
(line 194)
* http: Main configuration variables.
(line 323)
* hub: Main configuration variables.
(line 247)
* ID: Authentication protocol.
(line 10)
* IndirectData: Host configuration variables.
(line 34)
* INTERFACE: Scripts. (line 58)
* Interface: Main configuration variables.
(line 205)
* IRC: Contact information. (line 9)
* KEY_CHANGED: The meta-protocol. (line 64)
* KeyExpire: Main configuration variables.
(line 252)
* libevent: libevent. (line 6)
* libraries: Libraries. (line 6)
* license: OpenSSL. (line 36)
* LocalDiscovery: Main configuration variables.
(line 213)
* lzo: lzo. (line 6)
* MACExpire: Main configuration variables.
(line 258)
* MACLength: Host configuration variables.
(line 42)
* meta-protocol: The meta-connection. (line 18)
* META_KEY: Authentication protocol.
(line 10)
* Mode: Main configuration variables.
(line 224)
* multicast: Main configuration variables.
(line 100)
* multiple networks: Multiple networks. (line 6)
* NAME: Scripts. (line 52)
* Name: Main configuration variables.
(line 263)
* netmask: Network interfaces. (line 39)
* NETNAME <1>: tincctl environment variables.
(line 6)
* NETNAME: Scripts. (line 49)
* netname: Multiple networks. (line 6)
* Network Administrators Guide: Configuration introduction.
(line 15)
* NODE: Scripts. (line 62)
* OpenSSL: OpenSSL. (line 6)
* options: Runtime options. (line 9)
* PEM format: Host configuration variables.
(line 67)
* PING: The meta-protocol. (line 89)
* PingInterval: Main configuration variables.
(line 274)
* PingTimeout: Main configuration variables.
(line 278)
* platforms: Supported platforms. (line 6)
* PMTU: Host configuration variables.
(line 47)
* PMTUDiscovery: Host configuration variables.
(line 50)
* PONG: The meta-protocol. (line 89)
* Port: Host configuration variables.
(line 55)
* port numbers: Other files. (line 17)
* PriorityInheritance: Main configuration variables.
(line 284)
* private: Virtual Private Networks.
(line 10)
* PrivateKey: Main configuration variables.
(line 289)
* PrivateKeyFile: Main configuration variables.
(line 295)
* ProcessPriority: Main configuration variables.
(line 303)
* Proxy: Main configuration variables.
(line 308)
* PublicKey: Host configuration variables.
(line 59)
* PublicKeyFile: Host configuration variables.
(line 62)
* raw_socket: Main configuration variables.
(line 93)
* release: Supported platforms. (line 14)
* REMOTEADDRESS: Scripts. (line 67)
* REMOTEPORT: Scripts. (line 70)
* ReplayWindow: Main configuration variables.
(line 331)
* REQ_KEY: The meta-protocol. (line 64)
* requirements: Libraries. (line 6)
* router: Main configuration variables.
(line 227)
* runtime options: Runtime options. (line 9)
* scalability: tinc. (line 19)
* scripts: Scripts. (line 6)
* server: How connections work.
(line 18)
* signals: Signals. (line 6)
* socks4: Main configuration variables.
(line 312)
* socks5: Main configuration variables.
(line 317)
* StrictSubnets: Main configuration variables.
(line 342)
* SUBNET: Scripts. (line 74)
* Subnet: Host configuration variables.
(line 74)
* SVPN: Security. (line 11)
* switch: Main configuration variables.
(line 236)
* TCP: The meta-connection. (line 10)
* TCPonly: Host configuration variables.
(line 103)
* TINC: Security. (line 6)
* tinc: Introduction. (line 6)
* tinc-down: Scripts. (line 18)
* tinc-up <1>: Network interfaces. (line 19)
* tinc-up: Scripts. (line 10)
* tincd: tinc. (line 14)
* traditional VPNs: tinc. (line 19)
* tunifhead: Main configuration variables.
(line 135)
* TunnelServer: Main configuration variables.
(line 347)
* tunnohead: Main configuration variables.
(line 129)
* UDP <1>: Encryption of network packets.
(line 12)
* UDP: The UDP tunnel. (line 30)
* UDPRcvBuf: Main configuration variables.
(line 354)
* UDPSndBuf: Main configuration variables.
(line 359)
* UML: Main configuration variables.
(line 111)
* Universal tun/tap: Configuration of Linux kernels.
(line 6)
* VDE: Main configuration variables.
(line 116)
* virtual: Virtual Private Networks.
(line 18)
* virtual network device: The UDP tunnel. (line 6)
* VPN: Virtual Private Networks.
(line 6)
* vpnd: tinc. (line 6)
* website: Contact information. (line 6)
* zlib: zlib. (line 6)

Tag Table:
Node: Top811
Node: Introduction1131
Node: Virtual Private Networks1941
Node: tinc3667
Node: Supported platforms5194
Node: Preparations5893
Node: Configuring the kernel6149
Node: Configuration of Linux kernels6558
Node: Configuration of FreeBSD kernels7413
Node: Configuration of OpenBSD kernels7878
Node: Configuration of NetBSD kernels8486
Node: Configuration of Solaris kernels8891
Node: Configuration of Darwin (MacOS/X) kernels9552
Node: Configuration of Windows10241
Node: Libraries10755
Node: OpenSSL11156
Node: zlib13432
Node: lzo14261
Node: libevent15065
Node: Installation15760
Node: Building and installing tinc16776
Node: Darwin (MacOS/X) build environment17435
Node: Cygwin (Windows) build environment18002
Node: MinGW (Windows) build environment18590
Node: System files19114
Node: Device files19379
Node: Other files19795
Node: Configuration20408
Node: Configuration introduction20695
Node: Multiple networks22242
Node: How connections work23622
Node: Configuration files26195
Node: Main configuration variables27728
Node: Host configuration variables44334
Node: Scripts49564
Node: How to configure52243
Node: Network interfaces56861
Node: Example configuration59262
Node: Running tinc64414
Node: Runtime options65007
Node: Signals67711
Node: Debug levels68561
Node: Solving problems69497
Node: Error messages70927
Node: Sending bug reports75249
Node: Controlling tinc76201
Node: tincctl runtime options76598
Node: tincctl environment variables77297
Node: tincctl commands77641
Node: tincctl examples81866
Node: tincctl top82471
Node: Technical information84069
Node: The connection84304
Node: The UDP tunnel84616
Node: The meta-connection87677
Node: The meta-protocol89146
Node: Security94155
Node: Authentication protocol95285
Node: Encryption of network packets100289
Node: Security issues101662
Node: Platform specific information103279
Node: Interface configuration103507
Node: Routes105960
Node: About us107876
Node: Contact information108051
Node: Authors108455
Node: Concept Index108860

End Tag Table
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