There are two lzo compression levels.

[tinc] / doc / tinc.texi

diff --git a/doc/tinc.texi b/doc/tinc.texi
index 46af02d..838226b 100644 (file)
--- a/doc/tinc.texi
+++ b/doc/tinc.texi
@@ -1,4 +1,5 @@
 \input texinfo   @c -*-texinfo-*-
 \input texinfo   @c -*-texinfo-*-

+@c $Id: tinc.texi,v 1.8.4.37 2003/06/12 11:08:40 guus Exp $

 @c %**start of header
 @setfilename tinc.info
 @settitle tinc Manual
 @c %**start of header
 @setfilename tinc.info
 @settitle tinc Manual


@@ -6,43 +7,52 @@
 @c %**end of header
 
 @ifinfo
 @c %**end of header
 
 @ifinfo

+@dircategory Networking tools
+@direntry
+* tinc: (tinc).              The tinc Manual.
+@end direntry

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

-Copyright 1998 Ivo Timmermans <itimmermans@@bigfoot.com>
+Copyright @copyright{} 1998-2002 Ivo Timmermans
+<ivo@@o2w.nl>, Guus Sliepen <guus@@sliepen.eu.org> and
+Wessel Dankers <wsl@@nl.linux.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.
+$Id: tinc.texi,v 1.8.4.37 2003/06/12 11:08:40 guus Exp $

 
 

-     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.
+Permission is granted to make and distribute verbatim copies of this
+manual provided the copyright notice and this permission notice are
+preserved on all copies.
+
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided that the
+entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.

 
 @end ifinfo
 
 @titlepage
 @title tinc Manual
 @subtitle Setting up a Virtual Private Network with tinc
 
 @end ifinfo
 
 @titlepage
 @title tinc Manual
 @subtitle Setting up a Virtual Private Network with tinc

-@author Ivo Timmermans <itimmermans@@bigfoot.com>
+@author Ivo Timmermans and Guus Sliepen

 
 @page
 @vskip 0pt plus 1filll
 
 @page
 @vskip 0pt plus 1filll

-Copyright @copyright{} 1998 Ivo Timmermans <itimmermans@@bigfoot.com>
+@cindex copyright
+Copyright @copyright{} 1998-2002 Ivo Timmermans
+<ivo@@o2w.nl>, Guus Sliepen <guus@@sliepen.eu.org> and
+Wessel Dankers <wsl@@nl.linux.org>.
+
+$Id: tinc.texi,v 1.8.4.37 2003/06/12 11:08:40 guus Exp $

 
 

-     Permission is granted to make and distribute verbatim
-     copies of this manual provided the copyright notice and
-     this permission notice are preserved on all copies.
+Permission is granted to 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.
+Permission is granted to copy and distribute modified versions of this
+manual under the conditions for verbatim copying, provided that the
+entire resulting derived work is distributed under the terms of a
+permission notice identical to this one.

 
 @end titlepage
 
 
 @end titlepage
 


@@ -51,312 +61,770 @@ Copyright @copyright{} 1998 Ivo Timmermans <itimmermans@@bigfoot.com>
 
 @menu
 * Introduction::                Introduction
 
 @menu
 * Introduction::                Introduction

-* Configuring a Linux system::  Before compiling tinc
-* Installing tinc::             
-* Configuring tinc::            
-* Running tinc::                
-* Technical information::       
-* About us::                    
+* Preparations::
+* Installation::
+* Configuration::
+* Running tinc::
+* Technical information::
+* About us::

 * Concept Index::               All used terms explained
 @end menu
 
 * Concept Index::               All used terms explained
 @end menu
 

+
+@contents
+

 @c ==================================================================
 @c ==================================================================

-@node    Introduction, Configuring a Linux system, Top, Top
+@node    Introduction, Preparations, Top, Top

 @chapter Introduction
 
 @chapter Introduction
 

-@c straight from the www page
-
+@cindex tinc

 tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
 encryption to create a secure private network between hosts on the
 Internet.
 
 Because the tunnel appears to the IP level network code as a normal
 network device, there is no need to adapt any existing software.
 tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
 encryption to create a secure private network between hosts on the
 Internet.
 
 Because the tunnel appears to the IP level network code as a normal
 network device, there is no need to adapt any existing software.

-
-This tunneling allows VPN sites to share information with eachother
+The encrypted tunnels allows VPN sites to share information with each other

 over the Internet without exposing any information to others.
 
 over the Internet without exposing any information to others.
 

-This document is the manual for tinc. Included are chapters on how to
+This document is the manual for tinc.  Included are chapters on how to

 configure your computer to use tinc, as well as the configuration
 process of tinc itself.
 
 @menu
 * VPNs::                        Virtual Private Networks in general
 * tinc::                        about tinc
 configure your computer to use tinc, as well as the configuration
 process of tinc itself.
 
 @menu
 * VPNs::                        Virtual Private Networks in general
 * tinc::                        about tinc

+* Supported platforms::

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

+@cindex VPN

 A Virtual Private Network or VPN is a network that can only be accessed
 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
+by a few elected computers that participate.  This goal is achievable in

 more than just one way.
 
 @cindex private
 more than just one way.
 
 @cindex private

-For instance, a VPN can consist of a single standalone ethernet LAN. Or
-even two computers hooked up using a nullmodem cable@footnote{Though
-discussable, I think it qualifies as a VPN.}. In these cases, it is
-obvious that the network is @emph{private}. But there is another type
-of VPN, the type tinc was made for.
+Private networks can consist of a single stand-alone Ethernet LAN.  Or
+even two computers hooked up using a null-modem cable.  In these cases,
+it is
+obvious that the network is @emph{private}, no one can access it from the
+outside.  But if your computers are linked to the Internet, the network
+is not private anymore, unless one uses firewalls to block all private
+traffic.  But then, there is no way to send private data to trusted
+computers on the other end of the Internet.

 
 @cindex virtual
 
 @cindex virtual

-tinc uses normal IP datagrams to encapsulate data that goes over the VPN
-network link. In this case it's also clear that the network is
-@emph{virtual}, because no direct network link has to exist between to
-participants.
-
-As is the case with either type of VPN, anybody could eavesdrop. Or
-worse, alter data. Hence it's probably advisable to encrypt the data
+This problem can be solved by using @emph{virtual} networks.  Virtual
+networks can live on top of other networks, but they use encapsulation to
+keep using their private address space so they do not interfere with
+the Internet.  Mostly, virtual networks appear like a singe LAN, even though
+they can span the entire world.  But virtual networks can't be secured
+by using firewalls, because the traffic that flows through it has to go
+through the Internet, where other people can look at it.
+
+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.
 
 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.
+
+

 @c ==================================================================
 @c ==================================================================

-@node    tinc,  , VPNs, Introduction
+@node    tinc, Supported platforms, VPNs, Introduction

 @section tinc
 
 @section tinc
 

+@cindex vpnd

 I really don't quite remember what got us started, but it must have been
 I really don't quite remember what got us started, but it must have been

-Guus' idea. He wrote a simple implementation (about 50 lines of C) that
-used the @emph{ethertap} device that linux knows of since somewhere
-about kernel 2.1.60. It didn't work immediately and he improved it a
-bit. At this stage, the project was still simply called @samp{vpnd}.
+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 @samp{vpnd}.

 
 Since then, a lot has changed---to say the least.
 
 @cindex tincd
 tinc now supports encryption, it consists of a single daemon (tincd) for
 
 Since then, a lot has changed---to say the least.
 
 @cindex tincd
 tinc now supports encryption, it consists of a single daemon (tincd) for

-both the receiving and sending end, it hase becom largely
+both the receiving and sending end, it has become largely

 runtime-configurable---in short, it has become a full-fledged
 professional package.
 
 runtime-configurable---in short, it has become a full-fledged
 professional package.
 

-A lot can---and will be---changed. I have a few things that I'd 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
+@cindex Traditional VPNs
+@cindex scalability
+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.
 
 it stands, and then add more advanced features.
 

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

 available too.
 
 
 @c ==================================================================
 available too.
 
 
 @c ==================================================================

-@node    Configuring a Linux system, Installing tinc, Introduction, Top
-@chapter Configuring a Linux system
+@node    Supported platforms,  , tinc, Introduction
+@section Supported platforms
+
+@cindex platforms
+tinc has been verified to work under Linux, FreeBSD, OpenBSD and Solaris, 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.
+
+@cindex release
+For an up to date list of supported platforms, please check the list on
+our website:
+@uref{http://tinc.nl.linux.org/platforms}.
+
+
+@c ==================================================================
+@subsection Linux
+
+@cindex Linux
+tinc was first written for Linux running on an intel x86 processor, so
+this is the best supported platform.  The protocol however, and actually
+anything about tinc, has been rewritten to support random byte ordering
+and arbitrary word length.  So in theory it should run on other
+processors that Linux runs on.  It has already been verified to run on
+alpha and sparc processors as well.
+
+tinc uses the ethertap device or the universal tun/tap driver. The former is provided in the standard kernel
+from version 2.1.60 up to 2.3.x, but has been replaced in favour of the tun/tap driver in kernel versions 2.4.0 and later.
+
+
+@c ==================================================================
+@subsection FreeBSD
+
+@cindex FreeBSD
+tinc on FreeBSD relies on the universal tun/tap driver for its data
+acquisition from the kernel.  Therefore, tinc will work on the same platforms
+as this driver.  These are: FreeBSD 3.x, 4.x, 5.x.
+
+
+@c ==================================================================
+@subsection OpenBSD
+
+@cindex OpenBSD
+tinc on OpenBSD relies on the tun driver for its data
+acquisition from the kernel. It has been verified to work under at least OpenBSD 2.9.
+
+Tunneling IPv6 packets may not work on OpenBSD.
+
+
+@c ==================================================================
+@subsection Solaris
+
+@c ==================================================================
+@subsection NetBSD
+
+@cindex NetBSD
+tinc on NetBSD relies on the tun driver for its data
+acquisition from the kernel. It has been verified to work under at least NetBSD 1.5.2.
+
+Tunneling IPv6 does not work on OpenBSD.
+
+
+@c ==================================================================
+@subsection Solaris
+
+@cindex Solaris
+tinc on Solaris relies on the universal tun/tap driver for its data
+acquisition from the kernel.  Therefore, tinc will work on the same platforms
+as this driver.  These are: Solaris 8 (SunOS 5.8).

 
 

-This chapter contains information on how a Linux system is configured
-for the use of tinc.
+IPv6 packets cannot be tunneled on Solaris.
+
+@c ==================================================================
+@subsection Darwin (MacOS/X)
+
+@cindex Darwin
+@cindex MacOS/X
+tinc on Darwin relies on the tunnel driver for its data
+acquisition from the kernel. This driver is not part of Darwin but can be
+downloaded from @uref{http://chrisp.de/en/projects/tunnel.html}.
+
+IPv6 packets cannot be tunneled on Darwin.
+
+
+@c
+@c
+@c
+@c
+@c
+@c
+@c       Preparing your system
+@c
+@c
+@c
+@c
+@c
+
+@c ==================================================================
+@node    Preparations, Installation, Introduction, Top
+@chapter Preparations
+
+This chapter contains information on how to prepare your system to
+support tinc.

 
 @menu
 
 @menu

-* Configuring the kernel::      
-* Files Needed::                
-* Setting up the devices::      
+* Configuring the kernel::
+* Libraries::

 @end menu
 
 
 @c ==================================================================
 @end menu
 
 
 @c ==================================================================

-@node    Configuring the kernel, Files Needed, Configuring a Linux system, Configuring a Linux system
+@node    Configuring the kernel, Libraries, Preparations, Preparations

 @section Configuring the kernel
 
 @section Configuring the kernel
 

-Since this particular implementation only runs on 2.1 or higher Linux
-kernels, you should grab one (2.2 is current at this time). A 2.0 port
-is not really possible, unless someone tells me someone ported the
-ethertap and netlink devices back to 2.0.
+@cindex RedHat
+@cindex Debian
+@cindex netlink_dev
+@cindex tun
+@cindex ethertap
+If you are running Linux, chances are good that your kernel already supports
+all the devices that tinc needs for proper operation.  For example, the
+standard kernel from Redhat Linux already has support for ethertap and netlink
+compiled in.  Debian users can use the modconf utility to select the modules.
+If your Linux distribution supports this method of selecting devices, look out
+for something called `ethertap', and `netlink_dev' if it is using a kernel
+version prior to 2.4.0. In that case you will need both these devices.  If you
+are using kernel 2.4.0 or later, you need to select `tun'.
+
+@cindex Kernel-HOWTO
+If you can install these devices in a similar manner, you may skip this section.
+Otherwise, you will have to recompile the kernel in order to turn on the required features.
+If you are unfamiliar with the process of configuring and compiling a new kernel,
+you should read the @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel HOWTO} first.
+
+@menu
+* Configuration of Linux kernels 2.1.60 up to 2.4.0::
+* Configuration of Linux kernels 2.4.0 and higher::
+* Configuration of FreeBSD kernels::
+* Configuration of OpenBSD kernels::
+* Configuration of NetBSD kernels::
+* Configuration of Solaris kernels::
+* Configuration of Darwin (MacOS/X) kernels::
+@end menu

 
 

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

 
 

-Here are the options you have to turn on/off when configuring a new
-kernel.
+@c ==================================================================
+@node       Configuration of Linux kernels 2.1.60 up to 2.4.0, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel, Configuring the kernel
+@subsection Configuration of Linux kernels 2.1.60 up to 2.4.0
+
+Here are the options you have to turn on when configuring a new kernel:

 
 @example
 Code maturity level options
 [*] Prompt for development and/or incomplete code/drivers
 Networking options
 [*] Kernel/User netlink socket
 
 @example
 Code maturity level options
 [*] Prompt for development and/or incomplete code/drivers
 Networking options
 [*] Kernel/User netlink socket

-<*> Netlink device emulation
+<M> Netlink device emulation

 Network device support
 Network device support

-<*> Ethertap network tap
+<M> Ethertap network tap

 @end example
 
 @end example
 

-Any other options not mentioned here are not relevant to tinc. If you
-decide to build any of these as dynamic kernel modules, it's a good idea
-to add these lines to @file{/etc/modules.conf}.
+If you want to run more than one instance of tinc or other programs that use
+the ethertap, you have to compile the ethertap driver as a module, otherwise
+you can also choose to compile it directly into the kernel.
+
+If you decide to build any of these as dynamic kernel modules, it's a good idea
+to add these lines to @file{/etc/modules.conf}:

 
 @example
 
 @example

-alias tap0 ethertap

 alias char-major-36 netlink_dev
 alias char-major-36 netlink_dev

+alias tap0 ethertap
+options tap0 -o tap0 unit=0
+alias tap1 ethertap
+options tap1 -o tap1 unit=1
+...
+alias tap@emph{N} ethertap
+options tap@emph{N} -o tap@emph{N} unit=@emph{N}

 @end example
 
 @end example
 

-Finally, after having set up other options, build the kernel and boot
-it. Unfortunately it's not possible to insert these modules in a running
-kernel.
+Add as much alias/options lines as necessary.

 
 
 @c ==================================================================
 
 
 @c ==================================================================

-@node    Files Needed, Setting up the devices, Configuring the kernel, Configuring a Linux system
-@section Files Needed
+@node       Configuration of Linux kernels 2.4.0 and higher, Configuration of FreeBSD kernels, Configuration of Linux kernels 2.1.60 up to 2.4.0, Configuring the kernel
+@subsection Configuration of Linux kernels 2.4.0 and higher

 
 

-@subsubheading Device files
+Here are the options you have to turn on when configuring a new kernel:

 
 

-First, you'll need the special device file(s) that form the interface
-between the kernel and the daemon.
+@example
+Code maturity level options
+[*] Prompt for development and/or incomplete code/drivers
+Network device support
+<M> Universal tun/tap device driver support
+@end example
+
+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 have an early 2.4 kernel, you can choose both the tun/tap driver and the
+`Ethertap network tap' device.  This latter is marked obsolete, and chances are
+that it won't even function correctly anymore.  Make sure you select the
+universal tun/tap driver.
+
+If you decide to build the tun/tap driver as a kernel module, add these lines
+to @file{/etc/modules.conf}:

 
 @example
 
 @example

-mknod -m 600 /dev/tap0 c 36 16
-chown 0.0 /dev/tap0
+alias char-major-10-200 tun

 @end example
 
 @end example
 

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

 
 

-If you want to, you may also create more device files, which would be
-numbered 0...15, with minor device numbers 16...31. They all should be
-owned by root and have permission 600.
+@c ==================================================================
+@node       Configuration of FreeBSD kernels, Configuration of OpenBSD kernels, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel
+@subsection Configuration of FreeBSD kernels

 
 

+This section will contain information on how to configure your FreeBSD
+kernel to support the universal tun/tap device.  For 4.1 and higher
+versions, this is included in the default kernel configuration, for earlier
+systems (4.0 and earlier), you need to install the universal tun/tap driver
+yourself.
+
+Unfortunately somebody still has to write the text.
+
+
+@c ==================================================================
+@node       Configuration of OpenBSD kernels, Configuration of NetBSD kernels, Configuration of FreeBSD kernels, Configuring the kernel
+@subsection Configuration of OpenBSD kernels
+
+This section will contain information on how to configure your OpenBSD
+kernel to support the tun device.  For 2.9 and 3.0 systems,
+this is included in the default kernel configuration.
+
+Unfortunately somebody still has to write the text.
+
+
+@c ==================================================================
+@node       Configuration of NetBSD kernels, Configuration of Solaris kernels, Configuration of OpenBSD kernels, Configuring the kernel
+@subsection Configuration of NetBSD kernels
+
+This section will contain information on how to configure your NetBSD
+kernel to support the tun device.  For 1.5.2 systems,
+this is included in the default kernel configuration.
+
+Unfortunately somebody still has to write the text.
+
+
+@c ==================================================================
+@node       Configuration of Solaris kernels, Configuration of Darwin (MacOS/X) kernels, Configuration of NetBSD kernels, Configuring the kernel
+@subsection Configuration of Solaris kernels
+
+This section will contain information on how to configure your Solaris
+kernel to support the universal tun/tap device.  For Solaris 8 (SunOS 5.8),
+this is included in the default kernel configuration.
+
+Unfortunately somebody still has to write the text.

 
 

-@subsubheading @file{/etc/networks}

 
 

-You may add a line to @file{/etc/networks} so that your vpn will get a
-symoblic name. For example:
+@c ==================================================================
+@node       Configuration of Darwin (MacOS/X) kernels, , Configuration of Solaris kernels, Configuring the kernel
+@subsection Configuration of Darwin (MacOS/X) kernels
+
+Darwin does not come with a tunnel driver. You must download it at
+@uref{http://chrisp.de/en/projects/tunnel.html}. If compiling the source fails,
+try the binary module. The tunnel driver must be loaded before starting tinc
+with the following command:

 
 @example
 
 @example

-myvpn 10.0.0.0
+kmodload tunnel

 @end example
 
 @end example
 

+Once loaded, the tunnel driver will automatically create @file{/dev/tun0}..@file{/dev/tun3}
+and the corresponding network interfaces.

 
 

-@subsubheading @file{/etc/services}

 
 

-You may add this line to @file{/etc/services}. The effect is that you
-may supply a @samp{vpn} as a valid port number to some programs. The
-number 655 is registered with the IANA.
+@c ==================================================================
+@node    Libraries,  , Configuring the kernel, Preparations
+@section Libraries
+
+@cindex requirements
+@cindex 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::
+@end menu
+
+
+@c ==================================================================
+@node       OpenSSL, zlib, Libraries, Libraries
+@subsection OpenSSL
+
+@cindex 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 @emph{may} be added in the future.
+
+You can use your operating system's package manager to install this if
+available.  Make sure you install the development AND runtime versions
+of this package.
+
+If you have to install OpenSSL manually, you can get the source code
+from @url{http://www.openssl.org/}.  Instructions on how to configure,
+build and install this package are included within the package.  Please
+make sure you build development and runtime libraries (which is the
+default).
+
+If you installed the OpenSSL libraries from source, it may be necessary
+to let configure know where they are, by passing configure one of the
+--with-openssl-* parameters.

 
 @example
 
 @example

-tinc            655/tcp    TINC
-tinc            655/udp    TINC
-#                          Ivo Timmermans <itimmermans@@bigfoot.com>
+--with-openssl=DIR      OpenSSL library and headers prefix
+--with-openssl-include=DIR OpenSSL headers directory
+                        (Default is OPENSSL_DIR/include)
+--with-openssl-lib=DIR  OpenSSL library directory
+                        (Default is OPENSSL_DIR/lib)

 @end example
 
 
 @end example
 
 

+@subsubheading License
+
+@cindex license
+Since the license under which OpenSSL is distributed is not directly
+compatible with the terms of the GNU GPL
+@uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we
+include an addition to the GPL (see also the file COPYING.README):
+
+@quotation
+This program is released under the GPL with the additional exemption
+that compiling, linking, and/or using OpenSSL is allowed.  You may
+provide binary packages linked to the OpenSSL libraries, provided that
+all other requirements of the GPL are met.
+@end quotation
+
+

 @c ==================================================================
 @c ==================================================================

-@node    Setting up the devices,  , Files Needed, Configuring a Linux system
-@section Setting up the devices
+@node       zlib, lzo, OpenSSL, Libraries
+@subsection zlib

 
 

-Before you can start transmitting data over the tinc tunnel, you must
-set up the ethertap network devices.
+@cindex zlib
+For the optional compression of UDP packets, tinc uses the functions provided
+by the zlib library.

 
 

-First, decide which IP addresses you want to have associated with these
-devices, and what network mask they must have. You also need these
-numbers when you are going to configure tinc itself. @xref{Configuring
-tinc}.
+If this library is not installed, you wil get an error when configuring
+tinc for build.  Support for running tinc without having zlib
+installed @emph{may} be added in the future.
+
+You can use your operating system's package manager to install this if
+available.  Make sure you install the development AND runtime versions
+of this package.

 
 

-It doesn't matter much which part you do first, setting up the network
-devices or configure tinc. But they both have to be done before you try
-to start a tincd.
+If you have to install zlib manually, you can get the source code
+from @url{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).

 
 

-The actual setup of the ethertap device is quite simple, just repeat
-after me:
+
+@c ==================================================================
+@node       lzo,  , zlib, Libraries
+@subsection lzo
+
+@cindex 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 @emph{may} be added in the future.
+
+You can use your operating system's package manager to install this if
+available.  Make sure you install the development AND runtime versions
+of this package.
+
+If you have to install lzo manually, you can get the source code
+from @url{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).
+
+
+@c
+@c
+@c
+@c      Installing tinc
+@c
+@c
+@c
+@c
+
+@c ==================================================================
+@node    Installation, Configuration, Preparations, Top
+@chapter 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
+@uref{http://tinc.nl.linux.org/download, download page}, which has
+the checksums of these files listed; you may wish to check these with
+md5sum before continuing.
+
+tinc comes in a convenient autoconf/automake package, which you can just
+treat the same as any other package.  Which is just untar it, type
+`./configure' and then `make'.
+More detailed instructions are in the file @file{INSTALL}, which is
+included in the source distribution.
+
+@menu
+* Building and installing tinc::
+* System files::
+@end menu
+
+
+@c ==================================================================
+@node    Building and installing tinc, System files, Installation, Installation
+@section Building and installing tinc
+
+Detailed instructions on configuring the source, building tinc and installing tinc
+can be found in the file called @file{INSTALL}.
+
+@cindex binary package
+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::
+@end menu
+
+
+@c ==================================================================
+@node       Darwin (MacOS/X) build environment,  ,  , Building and installing tinc
+@subsection Darwin (MacOS/X) build environment
+
+In order to build tinc on Darwin, you need to install the MacOS/X Developer Tools
+from @uref{http://developer.apple.com/tools/macosxtools.html} and
+a recent version of Fink from @uref{http://fink.sourceforge.net/}.
+
+After installation use fink to download and install the following packages:
+autoconf25, automake, dlcompat, m4, openssl, zlib and lzo.
+
+
+@c ==================================================================
+@node    System files,  , Building and installing tinc, Installation
+@section System files
+
+Before you can run tinc, you must make sure you have all the needed
+files on your system.
+
+@menu
+* Device files::
+* Other files::
+@end menu
+
+
+@c ==================================================================
+@node       Device files, Other files, System files, System files
+@subsection Device files
+
+@cindex device files
+First, you'll need the special device file(s) that form the interface
+between the kernel and the daemon.
+
+The permissions for these files have to be such that only the super user
+may read/write to this file.  You'd want this, because otherwise
+eavesdropping would become a bit too easy.  This does, however, imply
+that you'd have to run tincd as root.
+
+If you use Linux and have a kernel version prior to 2.4.0, you have to make the
+ethertap devices:

 
 @example
 
 @example

-ifconfig tap@emph{n} hw ether fe:fd:@emph{xx}:@emph{xx}:@emph{xx}:@emph{xx}
+mknod -m 600 /dev/tap0 c 36 16
+mknod -m 600 /dev/tap1 c 36 17
+...
+mknod -m 600 /dev/tap@emph{N} c 36 @emph{N+16}

 @end example
 
 @end example
 

-The @emph{n} here is the number of the ethertap device you want to
-use. It should be the same @emph{n} as the one you use for
-@file{/dev/tap@emph{n}}. The @emph{xx}s are four hexadecimal numbers
-(0--ff). With previous versions of tincd, it didn't matter what they
-were. But newer kernels require properly set up ehternet addresses.
-In fact, the old behaviour was wrong. It is required that the @emph{xx}s
-match MyOwnVPNIP.
+There is a maximum of 16 ethertap devices.
+
+If you use the universal tun/tap driver, you have to create the
+following device file (unless it already exist):

 
 @example
 
 @example

-ifconfig tap@emph{n} @emph{IP} netmask @emph{mask}
+mknod -m 600 /dev/tun c 10 200

 @end example
 
 @end example
 

-This will activate the device with an IP address @emph{IP} with network
-mask @emph{mask}.
+If you use Linux, and you run the new 2.4 kernel using the devfs filesystem,
+then the tun/tap device will probably be automatically generated as
+@file{/dev/net/tun}.

 
 

+Unlike the ethertap device, you do not need multiple device files if
+you are planning to run multiple tinc daemons.

 
 
 @c ==================================================================
 
 
 @c ==================================================================

-@node    Installing tinc, Configuring tinc, Configuring a Linux system, Top
-@chapter Installing tinc
+@node       Other files,  , Device files, System files
+@subsection Other files

 
 

-First download it. This is the
-@uref{http://tinc.nl.linux.org/download.html, download
-page}, which has the checksums of these files listed; you may wish to
-check these with md5sum before continuing.
+@subsubheading @file{/etc/networks}

 
 

-tinc comes in a handy autoconf/automake package, which you can just
-treat the same as any other package. Which is just untar it, type
-`configure' and then `make'.
+You may add a line to @file{/etc/networks} so that your VPN will get a
+symbolic name.  For example:

 
 

-More detailed instructions are in the file @file{INSTALL}, which is
-included in the source distribution.
+@example
+myvpn 10.0.0.0
+@end example
+
+@subsubheading @file{/etc/services}
+
+@cindex port numbers
+You may add this line to @file{/etc/services}.  The effect is that you
+may supply a @samp{tinc} as a valid port number to some programs.  The
+number 655 is registered with the IANA.
+
+@example
+tinc            655/tcp    TINC
+tinc            655/udp    TINC
+#                          Ivo Timmermans <ivo@@o2w.nl>
+@end example
+
+
+@c
+@c
+@c
+@c
+@c         Configuring tinc
+@c
+@c
+@c
+@c

 
 
 @c ==================================================================
 
 
 @c ==================================================================

-@node    Configuring tinc, Running tinc, Installing tinc, Top
-@chapter Configuring tinc
+@node    Configuration, Running tinc, Installation, Top
+@chapter Configuration

 
 @menu
 
 @menu

-* Multiple networks::           
-* How connections work::        
-* Configuration file::          
-* Example::                     
+* Configuration introduction::
+* Multiple networks::
+* How connections work::
+* Configuration files::
+* Generating keypairs::
+* Network interfaces::
+* Example configuration::

 @end menu
 
 @end menu
 

+@c ==================================================================
+@node    Configuration introduction, Multiple networks, Configuration, Configuration
+@section Configuration introduction
+
+@cindex Network Administrators Guide
+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?
+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
+@uref{http://www.linuxdoc.org/LDP/nag2/, Linux Network Administrators Guide}.
+
+If you have everything clearly pictured in your mind,
+proceed in the following order:
+First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
+Then generate the keypairs.
+Finally, distribute the host configuration files.
+These steps are described in the subsections below.
+

 
 @c ==================================================================
 
 @c ==================================================================

-@node    Multiple networks, How connections work, Configuring tinc, Configuring tinc
+@node    Multiple networks, How connections work, Configuration introduction, Configuration

 @section Multiple networks
 
 @section Multiple networks
 

-@c from the manpage
-
-It is perfectly ok for you to run more than one tinc daemon.
-However, in its default form, you will soon notice that you can't use
-two different configuration files without the -c option.
+@cindex multiple networks
+@cindex netname
+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 sites of your VPN,
+but it is recommended that you choose one anyway.

 
 

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

 
 The effect of this is that the daemon will set its configuration
 
 The effect of this is that the daemon will set its configuration

-``root'' to /etc/tinc/nn/, where nn is your argument to the -n
-option. You'll notice that it appears in syslog as ``tincd.nn''.
+``root'' to /etc/tinc/netname/, where netname is your argument to the -n
+option.  You'll notice that it appears in syslog as ``tinc.netname''.

 
 However, it is not strictly necessary that you call tinc with the -n
 
 However, it is not strictly necessary that you call tinc with the -n

-option. In this case, the network name would just be empty, and it will
-be used as such. tinc now looks for files in /etc/tinc/, instead of
-/etc/tinc/nn/; the configuration file should be /etc/tinc/tincd.conf,
-and the passphrases are now expected to be in /etc/tinc/passphrases/.
+option.  In this case, the network name would just be empty, and it will
+be used as such.  tinc now looks for files in /etc/tinc/, instead of
+/etc/tinc/netname/; the configuration file should be /etc/tinc/tinc.conf,
+and the host configuration files are now expected to be in /etc/tinc/hosts/.

 
 But it is highly recommended that you use this feature of tinc, because
 
 But it is highly recommended that you use this feature of tinc, because

-it will be so much clearer whom your daemon talks to. Hence, we will
+it will be so much clearer whom your daemon talks to.  Hence, we will

 assume that you use it.
 
 
 @c ==================================================================
 assume that you use it.
 
 
 @c ==================================================================

-@node    How connections work, Configuration file, Multiple networks, Configuring tinc
+@node    How connections work, Configuration files, Multiple networks, Configuration

 @section How connections work
 
 @section How connections work
 

-Before going on, first a bit on how tinc sees connections.
-
-When tinc starts up, it reads in the configuration file and parses the
-commandline options. If it sees a `ConnectTo' value in the file, it will
-try to connect to it, on the given port. If this fails, tinc exits.
+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.
+
+@cindex client
+@cindex server
+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.

 
 
 @c ==================================================================
 
 
 @c ==================================================================

-@node    Configuration file, Example, How connections work, Configuring tinc
-@section Configuration file
+@node    Configuration files, Generating keypairs, How connections work, Configuration
+@section Configuration files

 
 The actual configuration of the daemon is done in the file
 
 The actual configuration of the daemon is done in the file

-@file{/etc/tinc/nn/tincd.conf}.
+@file{/etc/tinc/netname/tinc.conf} and at least one other file in the directory
+@file{/etc/tinc/netname/hosts/}.

 
 

-This file consists of comments (lines started with a #) or assignments
+These file consists of comments (lines started with a #) or assignments

 in the form of
 
 @example
 in the form of
 
 @example


@@ -364,800 +832,1095 @@ Variable = Value.
 @end example
 
 The variable names are case insensitive, and any spaces, tabs, newlines
 @end example
 
 The variable names are case insensitive, and any spaces, tabs, newlines

-and carriage returns are ignored. Note: it is not required that you put
+and carriage returns are ignored.  Note: it is not required that you put

 in the `=' sign, but doing so improves readability.  If you leave it
 out, remember to replace it with at least one space character.
 
 in the `=' sign, but doing so improves readability.  If you leave it
 out, remember to replace it with at least one space character.
 

+In this section all valid variables are listed in alphabetical order.
+The default value is given between parentheses,
+other comments are between square brackets and
+required directives are given in @strong{bold}.
+

 @menu
 @menu

-* Variables::                   
+* Main configuration variables::
+* Host configuration variables::
+* How to configure::

 @end menu
 
 @end menu
 

+

 @c ==================================================================
 @c ==================================================================

-@node    Variables,  , Configuration file, Configuration file
-@subsection Variables
+@node    Main configuration variables, Host configuration variables, Configuration files, Configuration files
+@subsection Main configuration variables

 
 

-Here are all valid variables, listed in alphabetical order:
+@table @asis
+@cindex AddressFamily
+@item 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.
+
+@cindex BindToAddress
+@item BindToAddress = <address> [experimental]
+If your computer has more than one IPv4 or IPv6 address, tinc
+will by default listen on all of them for incoming connections.
+It is possible to bind only to a single address with this variable.
+
+This option may not work on all platforms.
+
+@cindex BindToInterface
+@item 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.
+
+@cindex ConnectTo
+@item @strong{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.
+
+@cindex Device
+@item @strong{Device = <device>} (/dev/tap0 or /dev/net/tun)
+The virtual network device to use.  Note that you can only use one device per
+daemon.  See also @ref{Device files}.
+
+@cindex Hostnames
+@item Hostnames = <yes|no> (no)
+This option selects whether IP addresses (both real and on the VPN)
+should be resolved.  Since DNS lookups are blocking, it might affect
+tinc's efficiency, even stopping the daemon for a few seconds everytime
+it does a lookup if your DNS server is not responding.
+
+This does not affect resolving hostnames to IP addresses from the
+configuration file.
+
+@cindex Interface
+@item 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.
+Currently this option only affects the Linux tun/tap device.
+
+@cindex Mode
+@item Mode = <router|switch|hub> (router)
+This option selects the way packets are routed to other daemons.

 
 

-@c straight from the manpage

 @table @asis
 @table @asis

-@item AllowConnect = (yes|no)
-If set to yes, anyone may try to connect to you. If you set this to no,
-no incoming connections will be accepted. This does not affect the
-outgoing connections.
-
-@item ConnectPort = port
-Connect to the upstream host (given with the ConnectTo directive) on
-port port. port may be given in decimal (default), octal (when preceded
-by a single zero) or hexadecimal (prefixed with 0x).  port is the port
-number for both the UDP and the TCP (meta) connections.
-
-@item ConnectTo = (IP address|hostname)
-Specifies which host to connect to on startup. If the ConnectPort
-variable is omitted, then tinc will try to connect to port 655.
-
-If you don't specify a host with ConnectTo, regardless of whether a
-value for ConnectPort is given, tinc won't connect at all, and will
-instead just listen for incoming connections. Only the initiator of a
-tinc VPN should need this.
-
-@item ListenPort = port
-Listen on local port port. The computer connecting to this daemon should
-use this number as the argument for his ConnectPort. Again, the
-default is 655.
-
-@item MyOwnVPNIP = local address[/maskbits]
-The local address is the number that the daemon will propagate to
-other daemons on the network when it is identifying itself. Hence this
-will be the file name of the passphrase file that the other end expects
-to find the passphrase in.
-
-The local address is the IP address of the tap device, not the real IP
-address of the host running tincd. Due to changes in recent kernels, it
-is also necessary that you make the ethernet (also known as MAC) address
-equal to the IP address (see the example).
-
-maskbits is the number of bits set to 1 in the netmask part.
-
-@item MyVirtualIP = local address[/maskbits]
-This is an alias for MyOwnVPNIP.
-
-@item Passphrases = directory
-The directory where tinc will look for passphrases when someone tries to
-cennect. Please see the manpage for genauth(8) for more information
-about passphrases as used by tinc.
-
-@item PingTimeout = number
+@cindex router
+@item 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.
+
+@cindex switch
+@item 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.
+
+@cindex hub
+@item 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.
+@end table
+
+@cindex KeyExpire
+@item KeyExpire = <seconds> (3600)
+This option controls the time the encryption keys used to encrypt the data
+are valid.  It is common practice to change keys at regular intervals to
+make it even harder for crackers, even though it is thought to be nearly
+impossible to crack a single key.
+
+@cindex MACExpire
+@item 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".
+
+@cindex Name
+@item @strong{Name = <name>}
+This is a symbolic name for this connection.  It can be anything
+
+@cindex PingTimeout
+@item PingTimeout = <seconds> (60)

 The number of seconds of inactivity that tinc will wait before sending a
 The number of seconds of inactivity that tinc will wait before sending a

-probe to the other end. If that other end doesn't answer within that
+probe to the other end.  If that other end doesn't answer within that

 same amount of seconds, the connection is terminated, and the others
 will be notified of this.
 
 same amount of seconds, the connection is terminated, and the others
 will be notified of this.
 

-@item TapDevice = device
-The ethertap device to use. Note that you can only use one device per
-daemon. The info pages of the tinc package contain more information
-about configuring an ethertap device for linux.
+@cindex PriorityInheritance
+@item 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.

 
 

-@end table
+@cindex PrivateKey
+@item 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.

 
 

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

 
 

-@c ==================================================================
-@node    Example,  , Configuration file, Configuring tinc
-@section Example
+Note that there must be exactly one of PrivateKey
+or PrivateKeyFile
+specified in the configuration file.

 
 

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

 
 

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

 
 

-@example
-A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
-B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
-C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
-D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
-@end example
+@c ==================================================================
+@node    Host configuration variables, How to configure, Main configuration variables, Configuration files
+@subsection Host configuration variables

 
 

-``gateway'' is the VPN IP address of the machine that is running the
-tincd. ``internet IP'' is the IP address of the firewall, which does not
-need to run tincd, but it must do a port forwarding of TCP&UDP on port
-655 (unless otherwise configured).e
+@table @asis
+@cindex Address
+@item @strong{Address = <IP address|hostname>} [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.
+
+@cindex Cipher
+@item Cipher = <cipher> (blowfish)
+The symmetric cipher algorithm used to encrypt UDP packets.
+Any cipher supported by OpenSSL is recognized.
+
+@cindex Compression
+@item 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).
+
+@cindex Digest
+@item 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.
+
+@cindex IndirectData
+@item IndirectData = <yes|no> (no)
+This option specifies whether other tinc daemons besides the one you
+specified with ConnectTo can make a direct connection to you.  This is
+especially useful if you are behind a firewall and it is impossible to
+make a connection from the outside to your tinc daemon.  Otherwise, it
+is best to leave this option out or set it to no.
+
+@cindex MACLength
+@item MACLength = <length> (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.
+
+@cindex Port
+@item 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).
+
+@cindex PublicKey
+@item PublicKey = <key> [obsolete]
+This is the RSA public key for this host.
+
+@cindex PublicKeyFile
+@item PublicKeyFile = <path> [obsolete]
+This is the full path name of the RSA public key file that was generated
+by ``tincd --generate-keys''.  It must be a full path, not a relative
+directory.
+
+@cindex PEM format
+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
+@strong{one of the above two options} must be specified
+in each host configuration file, if you want to be able to establish a
+connection with that host.
+
+@cindex Subnet
+@item Subnet = <address[/prefixlength]>
+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.
+Shorthand notations are not supported.
+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 fec0:0:0:1:0:0:0:0/64.
+MAC addresses are notated like 0:1a:2b:3c:4d:5e.
+
+@cindex CIDR notation
+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
+@uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
+
+@cindex TCPonly
+@item TCPonly = <yes|no> (no) [experimental]
+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.
+@end table

 
 

-In this example, it is assumed that eth0 is the interface that points to
-the inner LAN of the office. This could be the same as the interface
-that leads to the internet.

 
 

-@subsubheading For A
+@c ==================================================================
+@node    How to configure,  , Host configuration variables, Configuration files
+@subsection How to configure
+
+@subsubheading Step 1.  Creating the main configuration file

 
 

-@emph{A} would be configured like this:
+The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
+Adapt the following example to create a basic configuration file:

 
 @example
 
 @example

-ifconfig tap0 hw ether fe:fd:0a:01:36:01
-ifconfig tap0 10.1.54.1 netmask 255.0.0.0
-ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
+Name = @emph{yourname}
+Device = @emph{/dev/tap0}
+PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv

 @end example
 
 @end example
 

-and in /etc/tinc/tincd.conf:
+Then, if you know to which other tinc daemon(s) yours is going to connect,
+add `ConnectTo' values.

 
 

-@example
-TapDevice = /dev/tap0
-MyVirtualIP = 10.1.54.1/16
-@end example
+@subsubheading Step 2.  Creating your host configuration file

 
 

-@subsubheading For B
+If you added a line containing `Name = yourname' in the main configuarion file,
+you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
+Adapt the following example to create a host configuration file:

 
 @example
 
 @example

-ifconfig tap0 hw ether fe:fd:0a:02:01:0c
-ifconfig tap0 10.2.1.12 netmask 255.0.0.0
-ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
+Address = @emph{your.real.hostname.org}
+Subnet = @emph{192.168.1.0/24}

 @end example
 
 @end example
 

-and in /etc/tinc/tincd.conf:
+You can also use an IP address instead of a hostname.
+The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
+If you have multiple address ranges you can specify more than one `Subnet'.
+You might also need to add a `Port' if you want your tinc daemon to run on a different port number than the default (655).

 
 

-@example
-TapDevice = /dev/tap0
-MyVirtualIP = 10.2.1.12/16
-ConnectTo = 1.2.3.4
-AllowConnect = no
-@end example

 
 

-Note here that the internal address (on eth0) doesn't have to be the
-same as on the tap0 device. Also, ConnectTo is given so that no-one can
-connect to this node.
+@c ==================================================================
+@node    Generating keypairs, Network interfaces, Configuration files, Configuration
+@section Generating keypairs

 
 

-@subsubheading For C
+@cindex key generation
+Now that you have already created the main configuration file and your host configuration file,
+you can easily create a public/private keypair by entering the following command:

 
 @example
 
 @example

-ifconfig tap0 hw ether fe:fd:0a:03:45:fe
-ifconfig tap0 10.3.69.254 netmask 255.0.0.0
-ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
+tincd -n @emph{netname} -K

 @end example
 
 @end example
 

-and in /etc/tinc/A/tincd.conf:
+tinc will generate a public and a private key and ask you where to put them.
+Just press enter to accept the defaults.

 
 

-@example
-MyVirtualIP = 10.3.69.254/16
-ConnectTo = 1.2.3.4
-ListenPort = 2000
-@end example

 
 

-C already has another daemon that runs on port 655, so they have to
-reserve another port for tinc. They also use the netname to distinguish
-between the two. tinc is started with `tincd -n A'.
+@c ==================================================================
+@node    Network interfaces, Example configuration, Generating keypairs, Configuration
+@section Network interfaces

 
 

-@subsubheading For D
+Before tinc can start transmitting data over the tunnel, it must
+set up the virtual network interface.

 
 

-@example
-ifconfig tap0 hw ether fe:fd:0a:04:03:20
-ifconfig tap0 10.4.3.32 netmask 255.0.0.0
-ifconfig tap0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
-@end example
+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 (@file{/dev/tun}, @file{/dev/tap0} or similar),
+which will also create a network interface called something like `tun0', `tap0', or,
+if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.

 
 

-and in /etc/tinc/tincd.conf:
+@cindex tinc-up
+You can configure the network interface by putting ordinary ifconfig, route, and other commands
+to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
+will be executed. When tinc exits, it will execute the script named
+@file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
+
+An example @file{tinc-up} script:

 
 @example
 
 @example

-MyVirtualIP = 10.4.3.32/16
-ConnectTo = 3.4.5.6
-ConnectPort = 2000
-AllowConnect = no
+#!/bin/sh
+ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0

 @end example
 
 @end example
 

-D will be connecting to C, which has a tincd running for this network on
-port 2000. Hence they need to put in a ConnectPort.
+This script gives the interface an IP address and a netmask.
+The kernel will also automatically add a route to this interface, so normally you don't need
+to add route commands to the @file{tinc-up} script.
+The kernel will also bring the interface up after this command.
+@cindex netmask
+The netmask is the mask of the @emph{entire} VPN network, not just your
+own subnet.

 
 

-@subsubheading Authentication

 
 

-A, B, C and D all generate a passphrase with genauth 2048, the output is
-stored in /etc/tinc/passphrases/local, except for C, where it should be
-/etc/tinc/A/passphrases/local.
+@c ==================================================================
+@node    Example configuration,  , Network interfaces, Configuration
+@section Example configuration

 
 

-A stores a copy of B's passphrase in /etc/tinc/passphrases/10.2.0.0

 
 

-A stores a copy of C's passphrase in /etc/tinc/passphrases/10.3.0.0
+@cindex example
+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.

 
 

-B stores a copy of A's passphrase in /etc/tinc/passphrases/10.1.0.0
+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.

 
 

-C stores a copy of A's passphrase in /etc/tinc/A/passphrases/10.1.0.0
+@example
+A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
+B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
+C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
+D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
+@end example

 
 

-C stores a copy of D's passphrase in /etc/tinc/A/passphrases/10.4.0.0
+``gateway'' is the VPN IP address of the machine that is running the
+tincd.  ``internet IP'' is the IP address of the firewall, which does not
+need to run tincd, but it must do a port forwarding of TCP&UDP on port
+655 (unless otherwise configured).

 
 

-D stores a copy of C's passphrase in /etc/tinc/passphrases/10.3.0.0
+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.

 
 

-@subsubheading Starting
+@subsubheading For Branch A

 
 

-A has to start their tincd first. Then come B and C, where C has to
-provide the option `-n A', because they have more than one tinc
-network. Finally, D's tincd is started.
+@emph{BranchA} would be configured like this:

 
 

+In @file{/etc/tinc/company/tinc-up}:

 
 

+@example
+# Real interface of internal network:
+# ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255

 
 

-@c ==================================================================
-@node    Running tinc, Technical information, Configuring tinc, Top
-@chapter Running tinc
+ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
+@end example

 
 

-Running tinc isn't just as easy as typing `tincd' and hoping everything
-will just work out the way you wanted. Instead, the use of tinc is a
-project that involves trust relations and more than one computer.
+and in @file{/etc/tinc/company/tinc.conf}:

 
 

-@menu
-* Managing keys::               
-* Runtime options::             
-@end menu
+@example
+Name = BranchA
+PrivateKeyFile = /etc/tinc/company/rsa_key.priv
+Device = /dev/tap0
+@end example

 
 

+On all hosts, /etc/tinc/company/hosts/BranchA contains:

 
 

-@c ==================================================================
-@node    Managing keys, Runtime options, Running tinc, Running tinc
-@section Managing keys
+@example
+Subnet = 10.1.0.0/16
+Address = 1.2.3.4

 
 

-Before attempting to start tinc, you have to create passphrases. When
-tinc tries to make a connection, it exchanges some sensitive
-data. Before doing so, it likes to know if the other end is
-trustworthy.
+-----BEGIN RSA PUBLIC KEY-----
+...
+-----END RSA PUBLIC KEY-----
+@end example

 
 

-To do this, both ends must have some knowledge about the other. In the
-case of tinc this is the authentication passphrase.
+Note that the IP addresses of eth0 and tap0 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 give both real internal network interfaces and tap interfaces the same IP address,
+since that will make things a lot easier to remember and set up.

 
 

-This passphrase is a number, which is chosen at random. This number is
-then sent to the other computers which want to talk to us directly. To
-avoid breaking security, this should be done over a known secure channel
-(such as ssh or similar).

 
 

-All passphrases are stored in the passphrases directory, which is
-normally /etc/tinc/nn/passphrases/, but it may be changed using the
-`Passphrases' option in the config file.
+@subsubheading For Branch B

 
 

-To generate a passphrase, run `genauth'. genauth takes one argument,
-which is the length of the passphrase in bits. The length of the
-passphrase should be in the range 1024--2048 for a key length of 128
-bits. genauth creates a random number of the specified length, and puts
-it to stdout.
+In @file{/etc/tinc/company/tinc-up}:

 
 

-Every computer that wants to participate in the VPN should do this, and
-store the output in the passphrases directory, in the file @file{local}.
+@example
+# Real interface of internal network:
+# ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255

 
 

-When every computer has his own local key, it should copy it to the
-computer that it wants to talk to directly. (i.e. the one it connects to
-during startup.) This should be done via a secure channel, because it is
-sensitive information. If this is not done securely, someone might break
-in on you later on.
+ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
+@end example

 
 

-Those non-local passphrase files must have the name of the VPN IP
-address that they will advertise to you. For instance, if a computer
-tells us it likes to be 10.1.1.3 with netmask 255.255.0.0, the file
-should still be called 10.1.1.3, and not 10.1.0.0.
+and in @file{/etc/tinc/company/tinc.conf}:

 
 

+@example
+Name = BranchB
+ConnectTo = BranchA
+PrivateKeyFile = /etc/tinc/company/rsa_key.priv
+@end example

 
 

-@c ==================================================================
-@node    Runtime options,  , Managing keys, Running tinc
-@section Runtime options
+Note here that the internal address (on eth0) doesn't have to be the
+same as on the tap0 device.  Also, ConnectTo is given so that no-one can
+connect to this node.

 
 

-Besides the settings in the configuration file, tinc also accepts some
-command line options.
+On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:

 
 

-This list is a longer version of that in the manpage. The latter is
-generated automatically, so may be more up-to-date.
+@example
+Subnet = 10.2.0.0/16
+Address = 2.3.4.5

 
 

-@c from the manpage
-@table @asis
-@item -c, --config=FILE
-Read configuration options from FILE. The default is
-@file{/etc/tinc/nn/tincd.conf}.
+-----BEGIN RSA PUBLIC KEY-----
+...
+-----END RSA PUBLIC KEY-----
+@end example

 
 

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

 
 

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

 
 

-@item -k, --kill
-Attempt to kill a running tincd and exit. A TERM signal (15) gets sent
-to the daemon that his its PID in /var/run/tincd.nn.pid.
+In @file{/etc/tinc/company/tinc-up}:

 
 

-Because it kills only one tincd, you should use -n here if you use it
-normally.
+@example
+# Real interface of internal network:
+# ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255

 
 

-@item -n, --net=NETNAME
-Connect to net NETNAME. @xref{Multiple networks}.
+ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
+@end example

 
 

-@item -t, --timeout=TIMEOUT
-Seconds to wait before giving a timeout. Should not be set too low,
-because every time tincd senses a timeout, it disconnects and reconnects
-again, which will cause unnecessary network traffic and log messages.
+and in @file{/etc/tinc/company/tinc.conf}:

 
 

-@item --help
-Display a short reminder of these runtime options and terminate.
+@example
+Name = BranchC
+ConnectTo = BranchA
+Device = /dev/tap1
+@end example

 
 

-@item --version
-Output version information and exit.
+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.

 
 

-@end table
+On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:

 
 

+@example
+Address = 3.4.5.6
+Subnet = 10.3.0.0/16
+Port = 2000

 
 

-@c ==================================================================
-@node    Technical information, About us, Running tinc, Top
-@chapter Technical information
+-----BEGIN RSA PUBLIC KEY-----
+...
+-----END RSA PUBLIC KEY-----
+@end example

 
 
 
 

-@c ==================================================================
-@menu
-* The Connection::              
-* Security::                    
-* The Protocol::                
-@end menu
+@subsubheading For Branch D

 
 

-@node    The Connection, Security, Technical information, Technical information
-@section The basic philosophy of the way tinc works
-@cindex Connection
+In @file{/etc/tinc/company/tinc-up}:

 
 

-tinc is a daemon that takes VPN data and transmit that to another host
-computer over the existing Internet infrastructure.
+@example
+# Real interface of internal network:
+# ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255

 
 

-@menu
-* Protocol Preview::            
-* The Meta-connection::         
-@end menu
+ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
+@end example

 
 

+and in @file{/etc/tinc/company/tinc.conf}:

 
 

-@c ==================================================================
-@node    Protocol Preview, The Meta-connection, The Connection, The Connection
-@subsection A preview of the way the tinc works
+@example
+Name = BranchD
+ConnectTo = BranchC
+Device = /dev/net/tun
+PrivateKeyFile = /etc/tinc/company/rsa_key.priv
+@end example

 
 

-@cindex ethertap
-@cindex frame type
-The data itself is read from a character device file, the so-called
-@emph{ethertap} device. This device is associated with a network
-interface. Any data sent to this interface can be read from the device,
-and any data written to the device gets sent from the interface. Data to
-and from the device is formatted as if it were a normal ethernet card,
-so a frame is preceded by two MAC addresses and a @emph{frame type}
-field.
-
-So when tinc reads an ethernet frame from the device, it determines its
-type. Right now, tinc can only handle Internet Protocol version 4 (IPv4)
-frames. Plans to support other protocols are being made. When tinc knows
-which type of frame it has read, it can also read the source and
-destination address from it.
-
-Now it is time that the frame gets encrypted. Currently the only
-encryption algorithm available is blowfish.
+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.
+Also note that since D uses the tun/tap driver, the network interface
+will not be called `tun' or `tap0' or something like that, but will
+have the same name as netname.

 
 

-@cindex encapsulating
-When the encryption is ready, time has come to actually transport the
-packet to the destination computer. We do this by sending the packet
-over an UDP connection to the destination host. This is called
-@emph{encapsulating}, the VPN packet (though now encrypted) is
-encapsulated in another IP datagram.
+On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:

 
 

-When the destination receives this packet, the same thing happens, only
-in reverse. So it does a decrypt on the contents of the UDP datagram,
-and it writes the decrypted information to its own ethertap device.
+@example
+Subnet = 10.4.0.0/16
+Address = 4.5.6.7

 
 

+-----BEGIN RSA PUBLIC KEY-----
+...
+-----END RSA PUBLIC KEY-----
+@end example

 
 

-@c ==================================================================
-@node    The Meta-connection,  , Protocol Preview, The Connection
-@subsection The meta-connection
+@subsubheading Key files

 
 

-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 encryption information to somebody.
+A, B, C and D all have generated a public/private keypair with the following command:

 
 

-TCP is a better alternative, because it already contains protection
-against information being lost, unlike UDP.
+@example
+tincd -n company -K
+@end example

 
 

-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.
+The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
+the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
+During key generation, tinc automatically guesses the right filenames based on the -n option and
+the Name directive in the @file{tinc.conf} file (if it is available).

 
 

-@cindex data-protocol
-@cindex meta-protocol
-Like with any communication, we must have a protocol, so that everybody
-knows what everything stands for, an how he 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.''
+@subsubheading 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.

 
 
 @c ==================================================================
 
 
 @c ==================================================================

-@node    Security, The Protocol, The Connection, Technical information
-@section About tinc's encryption and other security-related issues.
+@node    Running tinc, Technical information, Configuration, Top
+@chapter Running tinc

 
 

-@cindex tinc
-@cindex Cabal
-tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
-alleged Cabal was/is an organization that was said to keep an eye on the
-entire Internet. As this is exactly what you @emph{don't} want, we named
-the tinc project after TINC.
+If everything else is done, you can start tinc by typing the following command:

 
 

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

 
 

-This chapter is a mixture of ideas, reasoning and explanation, please
-don't take it too serious.
+@cindex daemon
+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
 
 @menu

-* Encryption::                  
-* Key Management::              
-* Authentification::            How to be sure we're talking to the right person
-* Protection::                  
+* Runtime options::
+* Error messages::

 @end menu
 
 
 @c ==================================================================
 @end menu
 
 
 @c ==================================================================

-@node    Encryption, Key Management, Security, Security
-@subsection Encryption
-
-Encryption algorithms come in lots of flavors, most of which are not
-safe enough to use on the Internet, if at all. Algorithms that we've
-considered using are: RSA, blowfish, twofish and IDEA.
-
-@itemize @bullet
-@item
-@cindex RSA
-@emph{RSA} is patented. A fee must be paid if you use it, so it can't
-be used in an Open Source program.
-
-@item
-@cindex blowfish
-@emph{blowfish} was the standard encryption method at least up to version
-0.2.23, but as Dekan pointed out, it may not be all that secure. It is
-also patented, but it may be used freely.
-
-@item
-@cindex twofish
-@emph{twofish} should be better, but i've not seen a useable
-ready-to-use implementation somewhere out of the US. I'll remember this
-as a future encryption method.
-
-@item
-@cindex IDEA
-@emph{IDEA} is patented, and free for non-commercial use. It is going to
-be the standard encryption method.
-
-@end itemize
-
-You may choose any of the last three encryption methods in tinc. Please
-note, however, that ALL computers on your VPN must currenttly use the
-same. This should (among other things) be more flexible, tinc could for
-instance load a new encryption library the minute it is needed.
-
-
-@c ==================================================================
-@node    Key Management, Authentification, Encryption, Security
-@subsection Key Management
-@c FIXME: recheck
-
-@cindex Diffie-Hellman
-You can't just send a private encryption key to your peer, because
-somebody else might already be listening to you. So you'll have to
-negotiate over a shared but secret key. One way to do this is by using
-the ``Diffie-Hellman key exchange'' protocol
-(@uref{http://www.rsa.com/rsalabs/faq/html/3-6-1.html}). The idea is as
-follows.
+@node    Runtime options, Error messages,  , Running tinc
+@section Runtime options

 
 

-You have two participants A and B that want to agree over a shared
-secret encryption key. Both parties have some large prime number p and a
-generator g. These numbers may be known to the outside world, and hence
-may be included in the source distribution.
+Besides the settings in the configuration file, tinc also accepts some
+command line options.

 
 

-@cindex secret key
-Both parties then generate a secret key. A generates a, and computes g^a
-mod p. This is then sent to B; while B computes g^b mod p, and transmits
-this to A, b being generated by B. Both a and b must be smaller than
-p-1.
+@cindex command line
+@cindex runtime options
+@cindex options
+@c from the manpage
+@table @samp
+@item --bypass-security
+Disables encryption and authentication.
+Only useful for debugging.

 
 

-These private keys are generated upon startup, and they are not changed
-while the connection exists. A possible feature in the future is to
-dynamically change the keys, every hour for example.
+@item -c, --config=PATH
+Read configuration options from the directory PATH.  The default is
+@file{/etc/tinc/netname/}.

 
 

-Both parties then calculate g^ab mod p = k. k is the new, shared, but
-still secret key.
+@cindex debug level
+@item -d, --debug=LEVEL
+Set debug level to LEVEL.  The higher the debug level, the more gets
+logged.  Everything goes via syslog.

 
 

-To obtain a key k of a sufficient length (128 bits in our vpnd), p
-should be 2^129-1 or more.
+@item -K, --generate-keys[=BITS]
+Generate public/private keypair of BITS length. If BITS is not specified,
+1024 is the default. tinc will ask where you want to store the files,
+but will default to the configuration directory (you can use the -c or -n option
+in combination with -K). After that, tinc will quit.

 
 

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

 
 

-@c ==================================================================
-@node    Authentification, Protection, Key Management, Security
-@subsection Authentification
-@c FIXME: recheck
+@item -k, --kill[=SIGNAL]
+Attempt to kill a running tincd (optionally with the specified SIGNAL instead of SIGTERM) and exit.
+Use it in conjunction with the -n option to make sure you kill the right tinc daemon.

 
 

-@cindex man-in-the-middle attack
-Because the Diffie-Hellman protocol is in itself vulnerable to the
-``man-in-the-middle attack,'' we should introduce an authentification
-system.
+@item -n, --net=NETNAME
+Connect to net NETNAME.  @xref{Multiple networks}.

 
 

-We will let A transmit a passphrase that is also known to B encrypted
-with g^a, before A sends this to B. This way, B can check whether A is
-really A or just someone else.
+@item -D, --no-detach
+Don't fork and detach.
+This will also disable the automatic restart mechanism for fatal errors.

 
 

-@cindex passphrase
-This passphrase should be 2304 bits for a symmetric encryption
-system. But since an asymmetric system is more secure, we could do with
-2048 bits. This only holds if the passphrase is very random. 
+@item -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.

 
 

-These passphrases could be stored in a file that is non-readable by
-anyone else but root; e.g. @file{/etc/vpn/passphrases}.
+@item --version
+Output version information and exit.

 
 

-The only thing that needs to be taken care of is how A announces its
-passphrase to B.
+@end table

 
 
 @c ==================================================================
 
 
 @c ==================================================================

-@node    Protection,  , Authentification, Security
-@subsection Protecting your data
+@node    Error messages,  , Runtime options, Running tinc
+@section Error messages

 
 

-Now we have securely hidden our data. But a malicious cracker may still
-bother you by randomly altering the encrypted data he intercepts.
+What follows is a list of the most common error messages you can see
+when configuring tinc.  Most of these messages are visible in the syslog
+only, so keep an eye on it!

 
 

+@table @strong
+@item Could not open /dev/tap0: No such device

 
 

-@c ==================================================================
-@node    The Protocol,  , Security, Technical information
-@section Detailed protocol specifications
+@itemize
+@item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
+@item You forgot to compile `Netlink device emulation' in the kernel.
+@end itemize

 
 

+@item Can't write to /dev/net/tun: No such device

 
 

+@itemize
+@item You forgot to `modprobe tun'.
+@item You forgot to compile `Universal TUN/TAP driver' in the kernel.
+@end itemize

 
 

-@menu
-* Data protocol::               
-* Meta protocol::               
-@end menu
+@item Packet with destination 1.2.3.4 is looping back to us!
+
+@itemize
+@item 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!
+@item 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. 
+@end itemize

 
 

-@c ==================================================================
-@node    Data protocol, Meta protocol, The Protocol, The Protocol
-@subsection The data protocol
+@item Network doesn't work, syslog shows only packets of length 46

 
 

-The data that is sent through the UDP connection is formatted as follows:
+@item Network address and prefix length do not match!

 
 

-@example
+@itemize
+@item The Subnet field must contain a @emph{network} address.
+@item If you only want to use one IP address, set the netmask to /32.
+@end itemize

 
 

-  bytes  |  Contents
-----------------------
-   0-1   |  The length of this packet, including all leading fields
-   2-5   |  The destination IP address
-  6-...  |  The encrypted data
+@item This is a bug: net.c:253: 24: Some error

 
 

-@end example
+@itemize
+@item This is something that should not have happened.
+Please report this, and tell us exactly what went wrong before you got
+this message.  In normal operation, these errors should not occur.
+@end itemize
+
+@item Error reading RSA key file `rsa_key.priv': No such file or directory

 
 

-The method that was used to encrypt the data should be made known via
-the meta-protocol, during early identification stages.
+@itemize
+@item You must specify the complete pathname.
+Specifying a relative path does not make sense here.  tinc changes its
+directory to / when starting (to avoid keeping a mount point busy).
+@end itemize

 
 

+@end table

 
 @c ==================================================================
 
 @c ==================================================================

-@node    Meta protocol,  , Data protocol, The Protocol
-@subsection The Meta protocol
+@node    Technical information, About us, Running tinc, Top
+@chapter Technical information

 
 

-This protocol consists of separate packets of enformation, that are
-generally formatted thusly:

 
 

-@example
+@menu
+* The connection::
+* The meta-protocol::
+* Security::
+@end menu

 
 

-  bytes  |  Contents
-----------------------
-    0    |  The request ID
-  1-...  |  (Optional: arguments)

 
 

-@end example
+@c ==================================================================
+@node    The connection, The meta-protocol, Technical information, Technical information
+@section The connection

 
 

-What follows is a listing of possible request IDs.
+@cindex connection
+tinc is a daemon that takes VPN data and transmit that to another host
+computer over the existing Internet infrastructure.

 
 

-@table @samp
-@item ACK
-Acknowledge. This generally means that the authentication has been
-accepted by the remote computer. Takes no arguments.
+@menu
+* The UDP tunnel::
+* The meta-connection::
+@end menu

 
 

-@example

 
 

-  bytes  |  Contents
-----------------------
-    0    |  `1'
+@c ==================================================================
+@node    The UDP tunnel, The meta-connection, The connection, The connection
+@subsection The UDP tunnel

 
 

-@end example
+@cindex virtual network device
+@cindex frame type
+The data itself is read from a character device file, the so-called
+@emph{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.

 
 

-@item AUTH_S_INIT
-@itemx AUTH_C_INIT
-Obsolete. Use @samp{BASIC_INFO}.
+@cindex encapsulating
+@cindex UDP
+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
+@emph{encapsulating}, the VPN packet (though now encrypted) is
+encapsulated in another IP datagram.

 
 

-@item AUTH_S_SPP
-@itemx AUTH_C_SPP
-Obsolete. Use @samp{PASSPHRASE}.
+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.

 
 

-@item AUTH_S_SKEY
-@itemx AUTH_C_SKEY
-Obsolete. Use @samp{PUBLIC_KEY}, @samp{REQ_KEY} and @samp{ANS_KEY}.

 
 

-@item AUTH_S_SACK
-@itemx AUTH_C_RACK
-Obsolete. Use @samp{ACK}.
+@c ==================================================================
+@node    The meta-connection,  , The UDP tunnel, The connection
+@subsection The meta-connection

 
 

-@item TERMREQ
-A request to terminate this connection, for whatever reason.
+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.

 
 

-@example
+@cindex TCP
+TCP is a better alternative, because it already contains protection
+against information being lost, unlike UDP.

 
 

-  bytes  |  Contents
-----------------------
-    0    |  `30'
-   1-4   |  The VPN IP address of the host that has exited
+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.

 
 

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

 
 

+The reason we don't use TCP for both protocols is that UDP is much
+better for encapsulation, even while it is less reliable.  The real
+problem is that when TCP would be used to encapsulate a TCP stream
+that's on the private network, for every packet sent there would be
+three 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.

 
 

-@item PINGTIMEOUT
-Terminate connection, but the reason must be a ping timeout.

 
 

+@c ==================================================================
+@node    The meta-protocol, Security, The connection, Technical information
+@section 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 @ref{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.
+
+@cindex ADD_EDGE
+@cindex ADD_SUBNET

 @example
 @example

-
-  bytes  |  Contents
-----------------------
-    0    |  `31'
-   1-4   |  The VPN IP address of the host that has exited
-
+daemon message
+--------------------------------------------------------------------------
+origin 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
+
+origin ADD_SUBNET node 192.168.1.0/24
+                     |         |     +--> prefixlength
+                     |         +--------> network address
+                     +------------------> owner of this subnet
+--------------------------------------------------------------------------

 @end example
 
 @end example
 

+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.

 
 

-@item PING
-Send probe to the other end, if he hasn't returned a @samp{PONG} within
-10 seconds, the connection is considered to be dead and will be
-terminated, we should try to notify the other by sending a
-@samp{PINGTIMEOUT} packet.
+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.

 
 

+@cindex DEL_EDGE
+@cindex DEL_SUBNET

 @example
 @example

-
-  bytes  |  Contents
-----------------------
-    0    |  `40'
-
+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
+------------------------------------------------------------------

 @end example
 
 @end example
 

+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.

 
 

-@item PONG
-See explanation for @samp{PING}
-
+@cindex REQ_KEY
+@cindex ANS_KEY
+@cindex KEY_CHANGED

 @example
 @example

-
-  bytes  |  Contents
-----------------------
-    0    |  `41'
-
+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
+--------------------------------------------------------------------------

 @end example
 
 @end example
 

+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.

 
 

-@item ADD_HOST
-Send an @samp{ADD_HOST} packet if you want to propagate all your current
-connections to a new computer on a network. If we get this request, we
-must forward it to everyone that hasn't got it yet.
-
+@cindex PING
+@cindex PONG

 @example
 @example

-
-  bytes  |  Contents
-----------------------
-    0    |  `60'
-   1-4   |  The real IP address of the new host
-   5-8   |  The VPN IP address of the new host
-   9-12  |  The VPN netmask
-  13-14  |  The port number that the new host listens on
-
+daemon message
+--------------------------------------------------------------------------
+origin PING
+dest.  PONG
+--------------------------------------------------------------------------

 @end example
 
 @end example
 

+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.

 
 

-@item BASIC_INFO
-This packet will contain all necessary basic information about
-ourselves, such as the port we listen on and our desired VPN IP address.
+This basically covers what is sent over the meta connection by
+tinc.

 
 

-@example

 
 

-  bytes  |  Contents
-----------------------
-    0    |  `61'
-    1    |  The protocol version.
-         |  This chapter describes version 4.
-   2-3   |  The port number that the new host listens on
-   4-7   |  The VPN IP address of the new host
-   8-11  |  The VPN netmask
+@c ==================================================================
+@node    Security,  , The meta-protocol, Technical information
+@section About tinc's encryption and other security-related issues.

 
 

-@end example
+@cindex TINC
+@cindex Cabal
+tinc got its name from ``TINC,'' short for @emph{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 @emph{don't} want, we named
+the tinc project after TINC.

 
 

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

 
 

-@item PASSPHRASE
-Send an encrypted passphrase. Should be encrypted with our
-@strong{public} key, and it must reach us before a @samp{PUBLIC_KEY}
-request.
+@menu
+* Authentication protocol::
+* Encryption of network packets::
+@end menu

 
 

+
+@c ==================================================================
+@node    Authentication protocol, Encryption of network packets, Security, Security
+@subsection Authentication protocol
+
+@cindex authentication
+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.
+
+@cindex ID
+@cindex META_KEY
+@cindex CHALLENGE
+@cindex CHAL_REPLY
+@cindex ACK

 @example
 @example

+daemon  message
+--------------------------------------------------------------------------
+client  <attempts connection>

 
 

-  bytes  |  Contents
-----------------------
-    0    |  `62'
-   1-2   |  The length of the encrypted passphrase
-  3-...  |  The encrypted passphrase
+server  <accepts connection>

 
 

-@end example
+client  ID client 12
+              |   +---> version
+              +-------> name of tinc daemon

 
 

+server  ID server 12
+              |   +---> version
+              +-------> name of tinc daemon

 
 

-@item PUBLIC_KEY
-This is only used during authentication of a new connection, later on we
-may use @samp{REQ_KEY} and @samp{ANS_KEY}.
+client  META_KEY 5f0823a93e35b69e...7086ec7866ce582b
+                 \_________________________________/
+                                 +-> RSAKEYLEN bits totally random string S1,
+                                     encrypted with server's public RSA key

 
 

-@example
-
-  bytes  |  Contents
-----------------------
-    0    |  `63'
-   1-2   |  The length of the key
-  3-...  |  The public key, given in base-36
+server  META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
+                 \_________________________________/
+                                 +-> RSAKEYLEN bits totally random string S2,
+                                     encrypted with client's public RSA key

 
 

-@end example
+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

 
 

-@item HOLD
-@itemx RESUME
-Unused.
+server  CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
+                  \_________________________________/
+                                 +-> CHALLEN bits totally random string H2

 
 

-@item CALCULATE
-@itemx CALC_RES
-@itemx ALMOST_KEY
-Never been in use.
+client  CHAL_REPLY 816a86
+                      +-> 160 bits SHA1 of H2

 
 

-@item REQ_KEY
-Request a public key from someone and return it to the sender of this
-request using a @samp{ANS_KEY} packet. If we get such request, we must
-forward it to the connection that leads to the destination.
+server  CHAL_REPLY 928ffe
+                      +-> 160 bits SHA1 of H1

 
 

-@example
+After the correct challenge replies are received, both ends have proved
+their identity. Further information is exchanged.

 
 

-  bytes  |  Contents
-----------------------
-    0    |  `160'
-   1-4   |  The source VPN IP address
-   5-8   |  The destination VPN IP address
-   9-14  |  `0'
+client  ACK 655 123 0
+             |   |  +-> options
+                |   +----> estimated weight
+                +--------> listening port of client

 
 

+server  ACK 655 321 0
+             |   |  +-> options
+                |   +----> estimated weight
+                +--------> listening port of server
+--------------------------------------------------------------------------

 @end example
 
 @end example
 

+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 send 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.

 
 

-@item ANS_KEY
-Answer to a @samp{REQ_KEY} request, forward it to the destination if it
-is not meant for us.
-
-@example
-
-  bytes  |  Contents
-----------------------
-    0    |  `161'
-   1-4   |  The source VPN IP address
-   5-8   |  The destination VPN IP address
-   9-12  |  The expiration date/time in seconds
-  13-14  |  The key length
-  15-... |  The public key in base-36

 
 

-@end example
+@c ==================================================================
+@node    Encryption of network packets,  , Authentication protocol, Security
+@subsection Encryption of network packet
+@cindex encryption

 
 

+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.

 
 

-@item KEY_CHANGED
-The source computer wants to tell that it has regenerated its private
-and public keys, so anything going there must be encrypted with a new
-shared key.
+@cindex UDP
+The UDP packet containing the network packet from the VPN has the following layout:

 
 @example
 
 @example

-
-  bytes  |  Contents
-----------------------
-    0    |  `162'
-   1-4   |  The source VPN IP address
-
+... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
+                             \___________________/\_____/
+                                       |             |
+                                       V             +---> digest algorithm
+                         Encrypted with symmetric cipher

 @end example
 
 @end example
 

-
-@end table
-
+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.

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


@@ -1165,8 +1928,8 @@ shared key.
 
 
 @menu
 
 
 @menu

-* Contact Information::         
-* Authors::                     
+* Contact Information::
+* Authors::

 @end menu
 
 
 @end menu
 
 


@@ -1174,11 +1937,13 @@ shared key.
 @node    Contact Information, Authors, About us, About us
 @section Contact information
 
 @node    Contact Information, Authors, About us, About us
 @section Contact information
 

-tinc's main page is at @url{http://tinc.nl.linux.org/},
+@cindex website
+tinc's website is at @url{http://tinc.nl.linux.org/},

 this server is located in the Netherlands.
 
 this server is located in the Netherlands.
 

-We have an IRC channel on the Open Projects IRC network. Connect to
-@uref{http://openprojects.nu/services/irc.html, irc.openprojects.net},
+@cindex IRC
+We have an IRC channel on the FreeNode IRC network. Connect to
+@uref{http://www.freenode.net/, irc.freenode.net}

 and join channel #tinc.
 
 
 and join channel #tinc.
 
 


@@ -1187,20 +1952,14 @@ and join channel #tinc.
 @section Authors
 
 @table @asis
 @section Authors
 
 @table @asis

-@item Ivo Timmermans (zarq) (@email{itimmermans@@bigfoot.com})
-Main coder/hacker and maintainer of the package.
-
-@item Guus Sliepen (guus)
-Originator of it all, co-author.
-
-@item Wessel Dankers (Ubiq)
-General obfuscator of the code.
-
+@item Ivo Timmermans (zarq) (@email{ivo@@o2w.nl})
+@item Guus Sliepen (guus) (@email{guus@@sliepen.eu.org})

 @end table
 
 @end table
 

-Thank you's to: Dekan, Emphyrio, vDong
-
-Greetings to: braque, Fluor, giggles, macro, smoke, tribbel
+We have received a lot of valuable input from users.  With their help,
+tinc has become the flexible and robust tool that it is today.  We have
+composed a list of contributions, in the file called @file{THANKS} in
+the source distribution.

 
 
 @c ==================================================================
 
 
 @c ==================================================================


@@ -1215,4 +1974,3 @@ Greetings to: braque, Fluor, giggles, macro, smoke, tribbel
 @c ==================================================================
 @contents
 @bye
 @c ==================================================================
 @contents
 @bye

-