1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.42 2003/08/02 22:01:50 guus Exp $
10 @dircategory Networking tools
12 * tinc: (tinc). The tinc Manual.
15 This is the info manual for tinc, a Virtual Private Network daemon.
17 Copyright @copyright{} 1998-2003 Ivo Timmermans
18 <ivo@@o2w.nl>, Guus Sliepen <guus@@sliepen.eu.org> and
19 Wessel Dankers <wsl@@nl.linux.org>.
21 $Id: tinc.texi,v 1.8.4.42 2003/08/02 22:01:50 guus Exp $
23 Permission is granted to make and distribute verbatim copies of this
24 manual provided the copyright notice and this permission notice are
25 preserved on all copies.
27 Permission is granted to copy and distribute modified versions of this
28 manual under the conditions for verbatim copying, provided that the
29 entire resulting derived work is distributed under the terms of a
30 permission notice identical to this one.
36 @subtitle Setting up a Virtual Private Network with tinc
37 @author Ivo Timmermans and Guus Sliepen
40 @vskip 0pt plus 1filll
42 Copyright @copyright{} 1998-2003 Ivo Timmermans
43 <ivo@@o2w.nl>, Guus Sliepen <guus@@sliepen.eu.org> and
44 Wessel Dankers <wsl@@nl.linux.org>.
46 $Id: tinc.texi,v 1.8.4.42 2003/08/02 22:01:50 guus Exp $
48 Permission is granted to make and distribute verbatim copies of this
49 manual provided the copyright notice and this permission notice are
50 preserved on all copies.
52 Permission is granted to copy and distribute modified versions of this
53 manual under the conditions for verbatim copying, provided that the
54 entire resulting derived work is distributed under the terms of a
55 permission notice identical to this one.
59 @c ==================================================================
60 @node Top, Introduction, (dir), (dir)
63 * Introduction:: Introduction
68 * Technical information::
70 * Concept Index:: All used terms explained
76 @c ==================================================================
77 @node Introduction, Preparations, Top, Top
81 tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
82 encryption to create a secure private network between hosts on the
85 Because the tunnel appears to the IP level network code as a normal
86 network device, there is no need to adapt any existing software.
87 The encrypted tunnels allows VPN sites to share information with each other
88 over the Internet without exposing any information to others.
90 This document is the manual for tinc. Included are chapters on how to
91 configure your computer to use tinc, as well as the configuration
92 process of tinc itself.
95 * VPNs:: Virtual Private Networks in general
97 * Supported platforms::
100 @c ==================================================================
101 @node VPNs, tinc, Introduction, Introduction
102 @section Virtual Private Networks
105 A Virtual Private Network or VPN is a network that can only be accessed
106 by a few elected computers that participate. This goal is achievable in
107 more than just one way.
110 Private networks can consist of a single stand-alone Ethernet LAN. Or
111 even two computers hooked up using a null-modem cable. In these cases,
113 obvious that the network is @emph{private}, no one can access it from the
114 outside. But if your computers are linked to the Internet, the network
115 is not private anymore, unless one uses firewalls to block all private
116 traffic. But then, there is no way to send private data to trusted
117 computers on the other end of the Internet.
120 This problem can be solved by using @emph{virtual} networks. Virtual
121 networks can live on top of other networks, but they use encapsulation to
122 keep using their private address space so they do not interfere with
123 the Internet. Mostly, virtual networks appear like a singe LAN, even though
124 they can span the entire world. But virtual networks can't be secured
125 by using firewalls, because the traffic that flows through it has to go
126 through the Internet, where other people can look at it.
128 As is the case with either type of VPN, anybody could eavesdrop. Or
129 worse, alter data. Hence it's probably advisable to encrypt the data
130 that flows over the network.
132 When one introduces encryption, we can form a true VPN. Other people may
133 see encrypted traffic, but if they don't know how to decipher it (they
134 need to know the key for that), they cannot read the information that flows
135 through the VPN. This is what tinc was made for.
138 @c ==================================================================
139 @node tinc, Supported platforms, VPNs, Introduction
143 I really don't quite remember what got us started, but it must have been
144 Guus' idea. He wrote a simple implementation (about 50 lines of C) that
145 used the ethertap device that Linux knows of since somewhere
146 about kernel 2.1.60. It didn't work immediately and he improved it a
147 bit. At this stage, the project was still simply called @samp{vpnd}.
149 Since then, a lot has changed---to say the least.
152 tinc now supports encryption, it consists of a single daemon (tincd) for
153 both the receiving and sending end, it has become largely
154 runtime-configurable---in short, it has become a full-fledged
155 professional package.
157 @cindex Traditional VPNs
159 tinc also allows more than two sites to connect to eachother and form a single VPN.
160 Traditionally VPNs are created by making tunnels, which only have two endpoints.
161 Larger VPNs with more sites are created by adding more tunnels.
162 tinc takes another approach: only endpoints are specified,
163 the software itself will take care of creating the tunnels.
164 This allows for easier configuration and improved scalability.
166 A lot can---and will be---changed. We have a number of things that we would like to
167 see in the future releases of tinc. Not everything will be available in
168 the near future. Our first objective is to make tinc work perfectly as
169 it stands, and then add more advanced features.
171 Meanwhile, we're always open-minded towards new ideas. And we're
175 @c ==================================================================
176 @node Supported platforms, , tinc, Introduction
177 @section Supported platforms
180 tinc has been verified to work under Linux, FreeBSD, OpenBSD, NetBSD, MacOS/X (Darwin), Solaris, and Windows (in a Cygwin environment),
181 with various hardware architectures. These are some of the platforms
182 that are supported by the universal tun/tap device driver or other virtual network device drivers.
183 Without such a driver, tinc will most
184 likely compile and run, but it will not be able to send or receive data
188 For an up to date list of supported platforms, please check the list on
190 @uref{http://tinc.nl.linux.org/platforms}.
193 @c ==================================================================
197 tinc was first written for Linux running on an intel x86 processor, so
198 this is the best supported platform. The protocol however, and actually
199 anything about tinc, has been rewritten to support random byte ordering
200 and arbitrary word length. So in theory it should run on other
201 processors that Linux runs on. It has already been verified to run on
202 alpha and sparc processors as well.
204 tinc uses the ethertap device or the universal tun/tap driver. The former is provided in the standard kernel
205 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.
208 @c ==================================================================
212 tinc on FreeBSD relies on the universal tun/tap driver for its data
213 acquisition from the kernel. Therefore, tinc will work on the same platforms
214 as this driver. These are: FreeBSD 3.x, 4.x, 5.x.
217 @c ==================================================================
221 tinc on OpenBSD relies on the tun driver for its data
222 acquisition from the kernel. It has been verified to work under at least OpenBSD 2.9.
224 Tunneling IPv6 packets may not work on OpenBSD.
227 @c ==================================================================
230 @c ==================================================================
234 tinc on NetBSD relies on the tun driver for its data
235 acquisition from the kernel. It has been verified to work under at least NetBSD 1.5.2.
237 Tunneling IPv6 does not work on OpenBSD.
240 @c ==================================================================
244 tinc on Solaris relies on the universal tun/tap driver for its data
245 acquisition from the kernel. Therefore, tinc will work on the same platforms
246 as this driver. These are: Solaris 8 (SunOS 5.8).
248 IPv6 packets cannot be tunneled on Solaris.
250 @c ==================================================================
251 @subsection Darwin (MacOS/X)
255 tinc on Darwin relies on the tunnel driver for its data
256 acquisition from the kernel. This driver is not part of Darwin but can be
257 downloaded from @uref{http://chrisp.de/en/projects/tunnel.html}.
259 IPv6 packets cannot be tunneled on Darwin.
261 @c ==================================================================
262 @subsection Cygwin (Windows)
266 tinc on Windows, in a Cygwin environment, relies on the CIPE driver for its data
267 acquisition from the kernel. This driver is not part of Windows but can be
268 downloaded from @uref{http://cipe-win32.sourceforge.net/}.
270 @c ==================================================================
271 @subsection MinGW (Windows)
275 tinc on Windows (native), compiled using MinGW, relies on the CIPE driver for its data
276 acquisition from the kernel. This driver is not part of Windows but can be
277 downloaded from @uref{http://cipe-win32.sourceforge.net/}.
286 @c Preparing your system
293 @c ==================================================================
294 @node Preparations, Installation, Introduction, Top
295 @chapter Preparations
297 This chapter contains information on how to prepare your system to
301 * Configuring the kernel::
306 @c ==================================================================
307 @node Configuring the kernel, Libraries, Preparations, Preparations
308 @section Configuring the kernel
315 If you are running Linux, chances are good that your kernel already supports
316 all the devices that tinc needs for proper operation. For example, the
317 standard kernel from Redhat Linux already has support for ethertap and netlink
318 compiled in. Debian users can use the modconf utility to select the modules.
319 If your Linux distribution supports this method of selecting devices, look out
320 for something called `ethertap', and `netlink_dev' if it is using a kernel
321 version prior to 2.4.0. In that case you will need both these devices. If you
322 are using kernel 2.4.0 or later, you need to select `tun'.
325 If you can install these devices in a similar manner, you may skip this section.
326 Otherwise, you will have to recompile the kernel in order to turn on the required features.
327 If you are unfamiliar with the process of configuring and compiling a new kernel,
328 you should read the @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel HOWTO} first.
331 * Configuration of Linux kernels 2.1.60 up to 2.4.0::
332 * Configuration of Linux kernels 2.4.0 and higher::
333 * Configuration of FreeBSD kernels::
334 * Configuration of OpenBSD kernels::
335 * Configuration of NetBSD kernels::
336 * Configuration of Solaris kernels::
337 * Configuration of Darwin (MacOS/X) kernels::
338 * Configuration of Cygwin (Windows)::
339 * Configuration of MinGW (Windows)::
343 @c ==================================================================
344 @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
345 @subsection Configuration of Linux kernels 2.1.60 up to 2.4.0
347 Here are the options you have to turn on when configuring a new kernel:
350 Code maturity level options
351 [*] Prompt for development and/or incomplete code/drivers
353 [*] Kernel/User netlink socket
354 <M> Netlink device emulation
355 Network device support
356 <M> Ethertap network tap
359 If you want to run more than one instance of tinc or other programs that use
360 the ethertap, you have to compile the ethertap driver as a module, otherwise
361 you can also choose to compile it directly into the kernel.
363 If you decide to build any of these as dynamic kernel modules, it's a good idea
364 to add these lines to @file{/etc/modules.conf}:
367 alias char-major-36 netlink_dev
369 options tap0 -o tap0 unit=0
371 options tap1 -o tap1 unit=1
373 alias tap@emph{N} ethertap
374 options tap@emph{N} -o tap@emph{N} unit=@emph{N}
377 Add as much alias/options lines as necessary.
380 @c ==================================================================
381 @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
382 @subsection Configuration of Linux kernels 2.4.0 and higher
384 Here are the options you have to turn on when configuring a new kernel:
387 Code maturity level options
388 [*] Prompt for development and/or incomplete code/drivers
389 Network device support
390 <M> Universal tun/tap device driver support
393 It's not necessary to compile this driver as a module, even if you are going to
394 run more than one instance of tinc.
396 If you have an early 2.4 kernel, you can choose both the tun/tap driver and the
397 `Ethertap network tap' device. This latter is marked obsolete, and chances are
398 that it won't even function correctly anymore. Make sure you select the
399 universal tun/tap driver.
401 If you decide to build the tun/tap driver as a kernel module, add these lines
402 to @file{/etc/modules.conf}:
405 alias char-major-10-200 tun
409 @c ==================================================================
410 @node Configuration of FreeBSD kernels, Configuration of OpenBSD kernels, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel
411 @subsection Configuration of FreeBSD kernels
413 For FreeBSD version 4.1 and higher, the tap driver is included in the default kernel configuration, for earlier
414 systems (4.0 and earlier), you need to install the universal tun/tap driver
418 @c ==================================================================
419 @node Configuration of OpenBSD kernels, Configuration of NetBSD kernels, Configuration of FreeBSD kernels, Configuring the kernel
420 @subsection Configuration of OpenBSD kernels
422 For OpenBSD version 2.9 and higher,
423 the tun driver is included in the default kernel configuration.
426 @c ==================================================================
427 @node Configuration of NetBSD kernels, Configuration of Solaris kernels, Configuration of OpenBSD kernels, Configuring the kernel
428 @subsection Configuration of NetBSD kernels
430 For NetBSD version 1.5.2 and higher,
431 the tun driver is included in the default kernel configuration.
434 @c ==================================================================
435 @node Configuration of Solaris kernels, Configuration of Darwin (MacOS/X) kernels, Configuration of NetBSD kernels, Configuring the kernel
436 @subsection Configuration of Solaris kernels
438 For Solaris 8 (SunOS 5.8) and higher,
439 the tun driver is included in the default kernel configuration.
442 @c ==================================================================
443 @node Configuration of Darwin (MacOS/X) kernels, Configuration of Cygwin (Windows), Configuration of Solaris kernels, Configuring the kernel
444 @subsection Configuration of Darwin (MacOS/X) kernels
446 Darwin does not come with a tunnel driver. You must download it at
447 @uref{http://chrisp.de/en/projects/tunnel.html}. If compiling the source fails,
448 try the binary module. The tunnel driver must be loaded before starting tinc
449 with the following command:
455 Once loaded, the tunnel driver will automatically create @file{/dev/tun0}..@file{/dev/tun3}
456 and the corresponding network interfaces.
459 @c ==================================================================
460 @node Configuration of Cygwin (Windows), Configuration of MinGW (Windows), Configuration of Darwin (MacOS/X) kernels, Configuring the kernel
461 @subsection Configuration of Cygwin (Windows)
463 You will need to install the CIPE driver, you can download it from
464 @uref{http://cipe-win32.sourceforge.net}. Configure the CIPE network device in
465 the same way as you would do from the tinc-up script.
468 @c ==================================================================
469 @node Configuration of MinGW (Windows), , Configuration of Cygwin (Windows), Configuring the kernel
470 @subsection Configuration of MinGW (Windows)
472 You will need to install the CIPE driver, you can download it from
473 @uref{http://cipe-win32.sourceforge.net}. Configure the CIPE network device in
474 the same way as you would do from the tinc-up script.
477 @c ==================================================================
478 @node Libraries, , Configuring the kernel, Preparations
483 Before you can configure or build tinc, you need to have the OpenSSL,
484 zlib and lzo libraries installed on your system. If you try to configure tinc without
485 having them installed, configure will give you an error message, and stop.
494 @c ==================================================================
495 @node OpenSSL, zlib, Libraries, Libraries
499 For all cryptography-related functions, tinc uses the functions provided
500 by the OpenSSL library.
502 If this library is not installed, you wil get an error when configuring
503 tinc for build. Support for running tinc without having OpenSSL
504 installed @emph{may} be added in the future.
506 You can use your operating system's package manager to install this if
507 available. Make sure you install the development AND runtime versions
510 If you have to install OpenSSL manually, you can get the source code
511 from @url{http://www.openssl.org/}. Instructions on how to configure,
512 build and install this package are included within the package. Please
513 make sure you build development and runtime libraries (which is the
516 If you installed the OpenSSL libraries from source, it may be necessary
517 to let configure know where they are, by passing configure one of the
518 --with-openssl-* parameters.
521 --with-openssl=DIR OpenSSL library and headers prefix
522 --with-openssl-include=DIR OpenSSL headers directory
523 (Default is OPENSSL_DIR/include)
524 --with-openssl-lib=DIR OpenSSL library directory
525 (Default is OPENSSL_DIR/lib)
529 @subsubheading License
532 Since the license under which OpenSSL is distributed is not directly
533 compatible with the terms of the GNU GPL
534 @uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we
535 include an addition to the GPL (see also the file COPYING.README):
538 This program is released under the GPL with the additional exemption
539 that compiling, linking, and/or using OpenSSL is allowed. You may
540 provide binary packages linked to the OpenSSL libraries, provided that
541 all other requirements of the GPL are met.
545 @c ==================================================================
546 @node zlib, lzo, OpenSSL, Libraries
550 For the optional compression of UDP packets, tinc uses the functions provided
553 If this library is not installed, you wil get an error when configuring
554 tinc for build. Support for running tinc without having zlib
555 installed @emph{may} be added in the future.
557 You can use your operating system's package manager to install this if
558 available. Make sure you install the development AND runtime versions
561 If you have to install zlib manually, you can get the source code
562 from @url{http://www.gzip.org/zlib/}. Instructions on how to configure,
563 build and install this package are included within the package. Please
564 make sure you build development and runtime libraries (which is the
568 @c ==================================================================
569 @node lzo, , zlib, Libraries
573 Another form of compression is offered using the lzo library.
575 If this library is not installed, you wil get an error when configuring
576 tinc for build. Support for running tinc without having lzo
577 installed @emph{may} be added in the future.
579 You can use your operating system's package manager to install this if
580 available. Make sure you install the development AND runtime versions
583 If you have to install lzo manually, you can get the source code
584 from @url{http://www.oberhumer.com/opensource/lzo/}. Instructions on how to configure,
585 build and install this package are included within the package. Please
586 make sure you build development and runtime libraries (which is the
599 @c ==================================================================
600 @node Installation, Configuration, Preparations, Top
601 @chapter Installation
603 If you use Debian, you may want to install one of the
604 precompiled packages for your system. These packages are equipped with
605 system startup scripts and sample configurations.
607 If you cannot use one of the precompiled packages, or you want to compile tinc
608 for yourself, you can use the source. The source is distributed under
609 the GNU General Public License (GPL). Download the source from the
610 @uref{http://tinc.nl.linux.org/download, download page}, which has
611 the checksums of these files listed; you may wish to check these with
612 md5sum before continuing.
614 tinc comes in a convenient autoconf/automake package, which you can just
615 treat the same as any other package. Which is just untar it, type
616 `./configure' and then `make'.
617 More detailed instructions are in the file @file{INSTALL}, which is
618 included in the source distribution.
621 * Building and installing tinc::
626 @c ==================================================================
627 @node Building and installing tinc, System files, Installation, Installation
628 @section Building and installing tinc
630 Detailed instructions on configuring the source, building tinc and installing tinc
631 can be found in the file called @file{INSTALL}.
633 @cindex binary package
634 If you happen to have a binary package for tinc for your distribution,
635 you can use the package management tools of that distribution to install tinc.
636 The documentation that comes along with your distribution will tell you how to do that.
639 * Darwin (MacOS/X) build environment::
640 * Cygwin (Windows) build environment::
641 * MinGW (Windows) build environment::
645 @c ==================================================================
646 @node Darwin (MacOS/X) build environment, Cygwin (Windows) build environment, , Building and installing tinc
647 @subsection Darwin (MacOS/X) build environment
649 In order to build tinc on Darwin, you need to install the MacOS/X Developer Tools
650 from @uref{http://developer.apple.com/tools/macosxtools.html} and
651 a recent version of Fink from @uref{http://fink.sourceforge.net/}.
653 After installation use fink to download and install the following packages:
654 autoconf25, automake, dlcompat, m4, openssl, zlib and lzo.
656 @c ==================================================================
657 @node Cygwin (Windows) build environment, MinGW (Windows) build environment, Darwin (MacOS/X) build environment, Building and installing tinc
658 @subsection Cygwin (Windows) build environment
660 If Cygwin hasn't already been installed, install it directly from
661 @uref{http://www.cygwin.com/}.
663 When tinc is compiled in a Cygwin environment, it can only be run in this environment,
664 but all programs, including those started outside the Cygwin environment, will be able to use the VPN.
665 It will also support all features.
667 @c ==================================================================
668 @node MinGW (Windows) build environment, , Cygwin (Windows) build environment, Building and installing tinc
669 @subsection MinGW (Windows) build environment
671 You will need to install the MinGW environment from @uref{http://www.mingw.org}.
673 When tinc is compiled using MinGW it runs natively under Windows,
674 it is not necessary to keep MinGW installed.
676 When running natively, tinc is not able to start scripts,
677 nor is tinc able to receive signals.
678 When detaching, tinc will install itself as a service,
679 which will be restarted automatically after reboots.
682 @c ==================================================================
683 @node System files, , Building and installing tinc, Installation
684 @section System files
686 Before you can run tinc, you must make sure you have all the needed
687 files on your system.
695 @c ==================================================================
696 @node Device files, Other files, System files, System files
697 @subsection Device files
700 First, you'll need the special device file(s) that form the interface
701 between the kernel and the daemon.
703 The permissions for these files have to be such that only the super user
704 may read/write to this file. You'd want this, because otherwise
705 eavesdropping would become a bit too easy. This does, however, imply
706 that you'd have to run tincd as root.
708 If you use Linux and have a kernel version prior to 2.4.0, you have to make the
712 mknod -m 600 /dev/tap0 c 36 16
713 mknod -m 600 /dev/tap1 c 36 17
715 mknod -m 600 /dev/tap@emph{N} c 36 @emph{N+16}
718 There is a maximum of 16 ethertap devices.
720 If you use the universal tun/tap driver, you have to create the
721 following device file (unless it already exist):
724 mknod -m 600 /dev/tun c 10 200
727 If you use Linux, and you run the new 2.4 kernel using the devfs filesystem,
728 then the tun/tap device will probably be automatically generated as
731 Unlike the ethertap device, you do not need multiple device files if
732 you are planning to run multiple tinc daemons.
735 @c ==================================================================
736 @node Other files, , Device files, System files
737 @subsection Other files
739 @subsubheading @file{/etc/networks}
741 You may add a line to @file{/etc/networks} so that your VPN will get a
742 symbolic name. For example:
748 @subsubheading @file{/etc/services}
751 You may add this line to @file{/etc/services}. The effect is that you
752 may supply a @samp{tinc} as a valid port number to some programs. The
753 number 655 is registered with the IANA.
758 # Ivo Timmermans <ivo@@o2w.nl>
773 @c ==================================================================
774 @node Configuration, Running tinc, Installation, Top
775 @chapter Configuration
778 * Configuration introduction::
779 * Multiple networks::
780 * How connections work::
781 * Configuration files::
782 * Generating keypairs::
783 * Network interfaces::
784 * Example configuration::
787 @c ==================================================================
788 @node Configuration introduction, Multiple networks, Configuration, Configuration
789 @section Configuration introduction
791 @cindex Network Administrators Guide
792 Before actually starting to configure tinc and editing files,
793 make sure you have read this entire section so you know what to expect.
794 Then, make it clear to yourself how you want to organize your VPN:
795 What are the nodes (computers running tinc)?
796 What IP addresses/subnets do they have?
797 What is the network mask of the entire VPN?
798 Do you need special firewall rules?
799 Do you have to set up masquerading or forwarding rules?
800 Do you want to run tinc in router mode or switch mode?
801 These questions can only be answered by yourself,
802 you will not find the answers in this documentation.
803 Make sure you have an adequate understanding of networks in general.
804 A good resource on networking is the
805 @uref{http://www.linuxdoc.org/LDP/nag2/, Linux Network Administrators Guide}.
807 If you have everything clearly pictured in your mind,
808 proceed in the following order:
809 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
810 Then generate the keypairs.
811 Finally, distribute the host configuration files.
812 These steps are described in the subsections below.
815 @c ==================================================================
816 @node Multiple networks, How connections work, Configuration introduction, Configuration
817 @section Multiple networks
819 @cindex multiple networks
821 In order to allow you to run more than one tinc daemon on one computer,
822 for instance if your computer is part of more than one VPN,
823 you can assign a ``netname'' to your VPN.
824 It is not required if you only run one tinc daemon,
825 it doesn't even have to be the same on all the sites of your VPN,
826 but it is recommended that you choose one anyway.
828 We will asume you use a netname throughout this document.
829 This means that you call tincd with the -n argument,
830 which will assign a netname to this daemon.
832 The effect of this is that the daemon will set its configuration
833 ``root'' to /etc/tinc/netname/, where netname is your argument to the -n
834 option. You'll notice that it appears in syslog as ``tinc.netname''.
836 However, it is not strictly necessary that you call tinc with the -n
837 option. In this case, the network name would just be empty, and it will
838 be used as such. tinc now looks for files in /etc/tinc/, instead of
839 /etc/tinc/netname/; the configuration file should be /etc/tinc/tinc.conf,
840 and the host configuration files are now expected to be in /etc/tinc/hosts/.
842 But it is highly recommended that you use this feature of tinc, because
843 it will be so much clearer whom your daemon talks to. Hence, we will
844 assume that you use it.
847 @c ==================================================================
848 @node How connections work, Configuration files, Multiple networks, Configuration
849 @section How connections work
851 When tinc starts up, it parses the command-line options and then
852 reads in the configuration file tinc.conf.
853 If it sees one or more `ConnectTo' values pointing to other tinc daemons in that file,
854 it will try to connect to those other daemons.
855 Whether this succeeds or not and whether `ConnectTo' is specified or not,
856 tinc will listen for incoming connection from other deamons.
857 If you did specify a `ConnectTo' value and the other side is not responding,
858 tinc will keep retrying.
859 This means that once started, tinc will stay running until you tell it to stop,
860 and failures to connect to other tinc daemons will not stop your tinc daemon
861 for trying again later.
862 This means you don't have to intervene if there are temporary network problems.
866 There is no real distinction between a server and a client in tinc.
867 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
868 and one which does specify such a value as a client.
869 It does not matter if two tinc daemons have a `ConnectTo' value pointing to each other however.
872 @c ==================================================================
873 @node Configuration files, Generating keypairs, How connections work, Configuration
874 @section Configuration files
876 The actual configuration of the daemon is done in the file
877 @file{/etc/tinc/netname/tinc.conf} and at least one other file in the directory
878 @file{/etc/tinc/netname/hosts/}.
880 These file consists of comments (lines started with a #) or assignments
887 The variable names are case insensitive, and any spaces, tabs, newlines
888 and carriage returns are ignored. Note: it is not required that you put
889 in the `=' sign, but doing so improves readability. If you leave it
890 out, remember to replace it with at least one space character.
892 In this section all valid variables are listed in alphabetical order.
893 The default value is given between parentheses,
894 other comments are between square brackets and
895 required directives are given in @strong{bold}.
898 * Main configuration variables::
899 * Host configuration variables::
904 @c ==================================================================
905 @node Main configuration variables, Host configuration variables, Configuration files, Configuration files
906 @subsection Main configuration variables
909 @cindex AddressFamily
910 @item AddressFamily = <ipv4|ipv6|any> (any)
911 This option affects the address family of listening and outgoing sockets.
912 If "any" is selected, then depending on the operating system
913 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
915 @cindex BindToAddress
916 @item BindToAddress = <address> [experimental]
917 If your computer has more than one IPv4 or IPv6 address, tinc
918 will by default listen on all of them for incoming connections.
919 It is possible to bind only to a single address with this variable.
921 This option may not work on all platforms.
923 @cindex BindToInterface
924 @item BindToInterface = <interface> [experimental]
925 If you have more than one network interface in your computer, tinc will
926 by default listen on all of them for incoming connections. It is
927 possible to bind tinc to a single interface like eth0 or ppp0 with this
930 This option may not work on all platforms.
933 @item @strong{ConnectTo = <name>}
934 Specifies which other tinc daemon to connect to on startup.
935 Multiple ConnectTo variables may be specified,
936 in which case outgoing connections to each specified tinc daemon are made.
937 The names should be known to this tinc daemon
938 (i.e., there should be a host configuration file for the name on the ConnectTo line).
940 If you don't specify a host with ConnectTo,
941 tinc won't try to connect to other daemons at all,
942 and will instead just listen for incoming connections.
945 @item @strong{Device = <device>} (/dev/tap0 or /dev/net/tun)
946 The virtual network device to use. Note that you can only use one device per
947 daemon. See also @ref{Device files}.
950 @item Hostnames = <yes|no> (no)
951 This option selects whether IP addresses (both real and on the VPN)
952 should be resolved. Since DNS lookups are blocking, it might affect
953 tinc's efficiency, even stopping the daemon for a few seconds everytime
954 it does a lookup if your DNS server is not responding.
956 This does not affect resolving hostnames to IP addresses from the
960 @item Interface = <interface>
961 Defines the name of the interface corresponding to the virtual network device.
962 Depending on the operating system and the type of device this may or may not actually set the name of the interface
963 or choose the device corresponding to this interface.
966 @item Mode = <router|switch|hub> (router)
967 This option selects the way packets are routed to other daemons.
973 variables in the host configuration files will be used to form a routing table.
974 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
976 This is the default mode, and unless you really know you need another mode, don't change it.
980 In this mode the MAC addresses of the packets on the VPN will be used to
981 dynamically create a routing table just like an Ethernet switch does.
982 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
983 at the cost of frequent broadcast ARP requests and routing table updates.
985 This mode is primarily useful if you want to bridge Ethernet segments.
989 This mode is almost the same as the switch mode, but instead
990 every packet will be broadcast to the other daemons
991 while no routing table is managed.
995 @item KeyExpire = <seconds> (3600)
996 This option controls the time the encryption keys used to encrypt the data
997 are valid. It is common practice to change keys at regular intervals to
998 make it even harder for crackers, even though it is thought to be nearly
999 impossible to crack a single key.
1002 @item MACExpire = <seconds> (600)
1003 This option controls the amount of time MAC addresses are kept before they are removed.
1004 This only has effect when Mode is set to "switch".
1007 @item @strong{Name = <name>}
1008 This is a symbolic name for this connection. It can be anything
1011 @item PingTimeout = <seconds> (60)
1012 The number of seconds of inactivity that tinc will wait before sending a
1013 probe to the other end. If that other end doesn't answer within that
1014 same amount of seconds, the connection is terminated, and the others
1015 will be notified of this.
1017 @cindex PriorityInheritance
1018 @item PriorityInheritance = <yes|no> (no) [experimental]
1019 When this option is enabled the value of the TOS field of tunneled IPv4 packets
1020 will be inherited by the UDP packets that are sent out.
1023 @item PrivateKey = <key> [obsolete]
1024 This is the RSA private key for tinc. However, for safety reasons it is
1025 advised to store private keys of any kind in separate files. This prevents
1026 accidental eavesdropping if you are editting the configuration file.
1028 @cindex PrivateKeyFile
1029 @item @strong{PrivateKeyFile = <path>} [recommended]
1030 This is the full path name of the RSA private key file that was
1031 generated by ``tincd --generate-keys''. It must be a full path, not a
1034 Note that there must be exactly one of PrivateKey
1036 specified in the configuration file.
1041 @c ==================================================================
1042 @node Host configuration variables, How to configure, Main configuration variables, Configuration files
1043 @subsection Host configuration variables
1047 @item @strong{Address = <IP address|hostname>} [recommended]
1048 This variable is only required if you want to connect to this host. It
1049 must resolve to the external IP address where the host can be reached,
1050 not the one that is internal to the VPN.
1053 @item Cipher = <cipher> (blowfish)
1054 The symmetric cipher algorithm used to encrypt UDP packets.
1055 Any cipher supported by OpenSSL is recognized.
1058 @item Compression = <level> (0)
1059 This option sets the level of compression used for UDP packets.
1060 Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
1061 10 (fast lzo) and 11 (best lzo).
1064 @item Digest = <digest> (sha1)
1065 The digest algorithm used to authenticate UDP packets.
1066 Any digest supported by OpenSSL is recognized.
1067 Furthermore, specifying "none" will turn off packet authentication.
1069 @cindex IndirectData
1070 @item IndirectData = <yes|no> (no)
1071 This option specifies whether other tinc daemons besides the one you
1072 specified with ConnectTo can make a direct connection to you. This is
1073 especially useful if you are behind a firewall and it is impossible to
1074 make a connection from the outside to your tinc daemon. Otherwise, it
1075 is best to leave this option out or set it to no.
1078 @item MACLength = <length> (4)
1079 The length of the message authentication code used to authenticate UDP packets.
1080 Can be anything from 0
1081 up to the length of the digest produced by the digest algorithm.
1084 @item Port = <port> (655)
1085 This is the port this tinc daemon listens on.
1086 You can use decimal portnumbers or symbolic names (as listed in /etc/services).
1089 @item PublicKey = <key> [obsolete]
1090 This is the RSA public key for this host.
1092 @cindex PublicKeyFile
1093 @item PublicKeyFile = <path> [obsolete]
1094 This is the full path name of the RSA public key file that was generated
1095 by ``tincd --generate-keys''. It must be a full path, not a relative
1099 From version 1.0pre4 on tinc will store the public key directly into the
1100 host configuration file in PEM format, the above two options then are not
1101 necessary. Either the PEM format is used, or exactly
1102 @strong{one of the above two options} must be specified
1103 in each host configuration file, if you want to be able to establish a
1104 connection with that host.
1107 @item Subnet = <address[/prefixlength]>
1108 The subnet which this tinc daemon will serve.
1109 tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
1110 If the packet matches a subnet,
1111 it will be sent to the daemon who has this subnet in his host configuration file.
1112 Multiple subnet lines can be specified for each daemon.
1114 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1115 in which case a subnet consisting of only that single address is assumed,
1116 or they can be a IPv4 or IPv6 network address with a prefixlength.
1117 Shorthand notations are not supported.
1118 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1119 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1120 Note that subnets like 192.168.1.1/24 are invalid!
1121 Read a networking HOWTO/FAQ/guide if you don't understand this.
1122 IPv6 subnets are notated like fec0:0:0:1:0:0:0:0/64.
1123 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1125 @cindex CIDR notation
1126 prefixlength is the number of bits set to 1 in the netmask part; for
1127 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1128 /22. This conforms to standard CIDR notation as described in
1129 @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
1132 @item TCPonly = <yes|no> (no) [experimental]
1133 If this variable is set to yes, then the packets are tunnelled over a
1134 TCP connection instead of a UDP connection. This is especially useful
1135 for those who want to run a tinc daemon from behind a masquerading
1136 firewall, or if UDP packet routing is disabled somehow.
1137 Setting this options also implicitly sets IndirectData.
1141 @c ==================================================================
1142 @node How to configure, , Host configuration variables, Configuration files
1143 @subsection How to configure
1145 @subsubheading Step 1. Creating the main configuration file
1147 The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
1148 Adapt the following example to create a basic configuration file:
1151 Name = @emph{yourname}
1152 Device = @emph{/dev/tap0}
1153 PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv
1156 Then, if you know to which other tinc daemon(s) yours is going to connect,
1157 add `ConnectTo' values.
1159 @subsubheading Step 2. Creating your host configuration file
1161 If you added a line containing `Name = yourname' in the main configuarion file,
1162 you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
1163 Adapt the following example to create a host configuration file:
1166 Address = @emph{your.real.hostname.org}
1167 Subnet = @emph{192.168.1.0/24}
1170 You can also use an IP address instead of a hostname.
1171 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1172 If you have multiple address ranges you can specify more than one `Subnet'.
1173 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).
1176 @c ==================================================================
1177 @node Generating keypairs, Network interfaces, Configuration files, Configuration
1178 @section Generating keypairs
1180 @cindex key generation
1181 Now that you have already created the main configuration file and your host configuration file,
1182 you can easily create a public/private keypair by entering the following command:
1185 tincd -n @emph{netname} -K
1188 tinc will generate a public and a private key and ask you where to put them.
1189 Just press enter to accept the defaults.
1192 @c ==================================================================
1193 @node Network interfaces, Example configuration, Generating keypairs, Configuration
1194 @section Network interfaces
1196 Before tinc can start transmitting data over the tunnel, it must
1197 set up the virtual network interface.
1199 First, decide which IP addresses you want to have associated with these
1200 devices, and what network mask they must have.
1202 tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1203 which will also create a network interface called something like `tun0', `tap0', or,
1204 if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.
1207 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1208 to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
1209 will be executed. When tinc exits, it will execute the script named
1210 @file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
1212 An example @file{tinc-up} script:
1216 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1219 This script gives the interface an IP address and a netmask.
1220 The kernel will also automatically add a route to this interface, so normally you don't need
1221 to add route commands to the @file{tinc-up} script.
1222 The kernel will also bring the interface up after this command.
1224 The netmask is the mask of the @emph{entire} VPN network, not just your
1228 @c ==================================================================
1229 @node Example configuration, , Network interfaces, Configuration
1230 @section Example configuration
1234 Imagine the following situation. Branch A of our example `company' wants to connect
1235 three branch offices in B, C and D using the Internet. All four offices
1236 have a 24/7 connection to the Internet.
1238 A is going to serve as the center of the network. B and C will connect
1239 to A, and D will connect to C. Each office will be assigned their own IP
1243 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1244 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1245 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1246 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1249 ``gateway'' is the VPN IP address of the machine that is running the
1250 tincd. ``internet IP'' is the IP address of the firewall, which does not
1251 need to run tincd, but it must do a port forwarding of TCP&UDP on port
1252 655 (unless otherwise configured).
1254 In this example, it is assumed that eth0 is the interface that points to
1255 the inner (physical) LAN of the office, although this could also be the
1256 same as the interface that leads to the Internet. The configuration of
1257 the real interface is also shown as a comment, to give you an idea of
1258 how these example host is set up. All branches use the netname `company'
1259 for this particular VPN.
1261 @subsubheading For Branch A
1263 @emph{BranchA} would be configured like this:
1265 In @file{/etc/tinc/company/tinc-up}:
1268 # Real interface of internal network:
1269 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
1271 ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
1274 and in @file{/etc/tinc/company/tinc.conf}:
1278 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1282 On all hosts, /etc/tinc/company/hosts/BranchA contains:
1285 Subnet = 10.1.0.0/16
1288 -----BEGIN RSA PUBLIC KEY-----
1290 -----END RSA PUBLIC KEY-----
1293 Note that the IP addresses of eth0 and tap0 are the same.
1294 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1295 It is in fact recommended to give give both real internal network interfaces and tap interfaces the same IP address,
1296 since that will make things a lot easier to remember and set up.
1299 @subsubheading For Branch B
1301 In @file{/etc/tinc/company/tinc-up}:
1304 # Real interface of internal network:
1305 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
1307 ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
1310 and in @file{/etc/tinc/company/tinc.conf}:
1315 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1318 Note here that the internal address (on eth0) doesn't have to be the
1319 same as on the tap0 device. Also, ConnectTo is given so that no-one can
1320 connect to this node.
1322 On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:
1325 Subnet = 10.2.0.0/16
1328 -----BEGIN RSA PUBLIC KEY-----
1330 -----END RSA PUBLIC KEY-----
1334 @subsubheading For Branch C
1336 In @file{/etc/tinc/company/tinc-up}:
1339 # Real interface of internal network:
1340 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
1342 ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
1345 and in @file{/etc/tinc/company/tinc.conf}:
1353 C already has another daemon that runs on port 655, so they have to
1354 reserve another port for tinc. It knows the portnumber it has to listen on
1355 from it's own host configuration file.
1357 On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:
1361 Subnet = 10.3.0.0/16
1364 -----BEGIN RSA PUBLIC KEY-----
1366 -----END RSA PUBLIC KEY-----
1370 @subsubheading For Branch D
1372 In @file{/etc/tinc/company/tinc-up}:
1375 # Real interface of internal network:
1376 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
1378 ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
1381 and in @file{/etc/tinc/company/tinc.conf}:
1386 Device = /dev/net/tun
1387 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1390 D will be connecting to C, which has a tincd running for this network on
1391 port 2000. It knows the port number from the host configuration file.
1392 Also note that since D uses the tun/tap driver, the network interface
1393 will not be called `tun' or `tap0' or something like that, but will
1394 have the same name as netname.
1396 On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:
1399 Subnet = 10.4.0.0/16
1402 -----BEGIN RSA PUBLIC KEY-----
1404 -----END RSA PUBLIC KEY-----
1407 @subsubheading Key files
1409 A, B, C and D all have generated a public/private keypair with the following command:
1415 The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
1416 the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
1417 During key generation, tinc automatically guesses the right filenames based on the -n option and
1418 the Name directive in the @file{tinc.conf} file (if it is available).
1420 @subsubheading Starting
1422 After each branch has finished configuration and they have distributed
1423 the host configuration files amongst them, they can start their tinc daemons.
1424 They don't necessarily have to wait for the other branches to have started
1425 their daemons, tinc will try connecting until they are available.
1428 @c ==================================================================
1429 @node Running tinc, Technical information, Configuration, Top
1430 @chapter Running tinc
1432 If everything else is done, you can start tinc by typing the following command:
1435 tincd -n @emph{netname}
1439 tinc will detach from the terminal and continue to run in the background like a good daemon.
1440 If there are any problems however you can try to increase the debug level
1441 and look in the syslog to find out what the problems are.
1449 @c ==================================================================
1450 @node Runtime options, Error messages, , Running tinc
1451 @section Runtime options
1453 Besides the settings in the configuration file, tinc also accepts some
1454 command line options.
1456 @cindex command line
1457 @cindex runtime options
1461 @item -c, --config=PATH
1462 Read configuration options from the directory PATH. The default is
1463 @file{/etc/tinc/netname/}.
1465 @item -D, --no-detach
1466 Don't fork and detach.
1467 This will also disable the automatic restart mechanism for fatal errors.
1470 @item -d, --debug=LEVEL
1471 Set debug level to LEVEL. The higher the debug level, the more gets
1472 logged. Everything goes via syslog.
1474 @item -k, --kill[=SIGNAL]
1475 Attempt to kill a running tincd (optionally with the specified SIGNAL instead of SIGTERM) and exit.
1476 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1477 Under native Windows the optional argument is ignored,
1478 the service will always be stopped and removed.
1480 @item -n, --net=NETNAME
1481 Connect to net NETNAME. @xref{Multiple networks}.
1483 @item -K, --generate-keys[=BITS]
1484 Generate public/private keypair of BITS length. If BITS is not specified,
1485 1024 is the default. tinc will ask where you want to store the files,
1486 but will default to the configuration directory (you can use the -c or -n option
1487 in combination with -K). After that, tinc will quit.
1490 Lock tinc into main memory.
1491 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1493 @item --logfile[=FILE]
1494 Write log entries to a file instead of to the system logging facility.
1495 If FILE is omitted, the default is /var/log/tinc.NETNAME.log.
1497 @item --pidfile=FILE
1498 Write PID to FILE instead of /var/run/tinc.NETNAME.pid.
1500 @item --bypass-security
1501 Disables encryption and authentication.
1502 Only useful for debugging.
1505 Display a short reminder of these runtime options and terminate.
1508 Output version information and exit.
1513 @c ==================================================================
1514 @node Error messages, , Runtime options, Running tinc
1515 @section Error messages
1517 What follows is a list of the most common error messages you can see
1518 when configuring tinc. Most of these messages are visible in the syslog
1519 only, so keep an eye on it!
1522 @item Could not open /dev/tap0: No such device
1525 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1526 @item You forgot to compile `Netlink device emulation' in the kernel.
1529 @item Can't write to /dev/net/tun: No such device
1532 @item You forgot to `modprobe tun'.
1533 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1536 @item Packet with destination 1.2.3.4 is looping back to us!
1539 @item Something is not configured right. Packets are being sent out to the
1540 virtual network device, but according to the Subnet directives in your host configuration
1541 file, those packets should go to your own host. Most common mistake is that
1542 you have a Subnet line in your host configuration file with a prefix length which is
1543 just as large as the prefix of the virtual network interface. The latter should in almost all
1544 cases be larger. Rethink your configuration.
1545 Note that you will only see this message if you specified a debug
1546 level of 5 or higher!
1547 @item Chances are that a `Subnet = ...' line in the host configuration file of this tinc daemon is wrong.
1548 Change it to a subnet that is accepted locally by another interface,
1549 or if that is not the case, try changing the prefix length into /32.
1552 @item Network doesn't work, syslog shows only packets of length 46
1554 @item Network address and prefix length do not match!
1557 @item The Subnet field must contain a @emph{network} address.
1558 @item If you only want to use one IP address, set the netmask to /32.
1561 @item This is a bug: net.c:253: 24: Some error
1564 @item This is something that should not have happened.
1565 Please report this, and tell us exactly what went wrong before you got
1566 this message. In normal operation, these errors should not occur.
1569 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1572 @item You must specify the complete pathname.
1573 Specifying a relative path does not make sense here. tinc changes its
1574 directory to / when starting (to avoid keeping a mount point busy).
1579 @c ==================================================================
1580 @node Technical information, About us, Running tinc, Top
1581 @chapter Technical information
1586 * The meta-protocol::
1591 @c ==================================================================
1592 @node The connection, The meta-protocol, Technical information, Technical information
1593 @section The connection
1596 tinc is a daemon that takes VPN data and transmit that to another host
1597 computer over the existing Internet infrastructure.
1601 * The meta-connection::
1605 @c ==================================================================
1606 @node The UDP tunnel, The meta-connection, The connection, The connection
1607 @subsection The UDP tunnel
1609 @cindex virtual network device
1611 The data itself is read from a character device file, the so-called
1612 @emph{virtual network device}. This device is associated with a network
1613 interface. Any data sent to this interface can be read from the device,
1614 and any data written to the device gets sent from the interface.
1615 There are two possible types of virtual network devices:
1616 `tun' style, which are point-to-point devices which can only handle IPv4 and/or IPv6 packets,
1617 and `tap' style, which are Ethernet devices and handle complete Ethernet frames.
1619 So when tinc reads an Ethernet frame from the device, it determines its
1620 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
1621 packets. Depending on the Subnet lines, it will send the packets off to their destination IP address.
1622 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
1623 to deduce the destination of the packets.
1624 Since the latter modes only depend on the link layer information,
1625 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
1626 However, only `tap' style devices provide this information.
1628 After the destination has been determined,
1629 the packet will be compressed (optionally),
1630 a sequence number will be added to the packet,
1631 the packet will then be encrypted
1632 and a message authentication code will be appended.
1634 @cindex encapsulating
1636 When that is done, time has come to actually transport the
1637 packet to the destination computer. We do this by sending the packet
1638 over an UDP connection to the destination host. This is called
1639 @emph{encapsulating}, the VPN packet (though now encrypted) is
1640 encapsulated in another IP datagram.
1642 When the destination receives this packet, the same thing happens, only
1643 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
1644 checks the sequence number
1645 and writes the decrypted information to its own virtual network device.
1647 If the virtual network device is a `tun' device (a point-to-point tunnel),
1648 there is no problem for the kernel to accept a packet.
1649 However, if it is a `tap' device (this is the only available type on FreeBSD),
1650 the destination MAC address must match that of the virtual network interface.
1651 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC
1652 can not be known by the sending host.
1653 tinc solves this by letting the receiving end detect the MAC address of its own virtual network interface
1654 and overwriting the destination MAC address of the received packet.
1656 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
1657 In those modes every interface should have a unique MAC address, so make sure they are not the same.
1658 Because switch and hub modes rely on MAC addresses to function correctly,
1659 these modes cannot be used on the following operating systems which don't have a `tap' style virtual network device:
1660 OpenBSD, NetBSD, Darwin and Solaris.
1663 @c ==================================================================
1664 @node The meta-connection, , The UDP tunnel, The connection
1665 @subsection The meta-connection
1667 Having only a UDP connection available is not enough. Though suitable
1668 for transmitting data, we want to be able to reliably send other
1669 information, such as routing and session key information to somebody.
1672 TCP is a better alternative, because it already contains protection
1673 against information being lost, unlike UDP.
1675 So we establish two connections. One for the encrypted VPN data, and one
1676 for other information, the meta-data. Hence, we call the second
1677 connection the meta-connection. We can now be sure that the
1678 meta-information doesn't get lost on the way to another computer.
1680 @cindex data-protocol
1681 @cindex meta-protocol
1682 Like with any communication, we must have a protocol, so that everybody
1683 knows what everything stands for, and how she should react. Because we
1684 have two connections, we also have two protocols. The protocol used for
1685 the UDP data is the ``data-protocol,'' the other one is the
1688 The reason we don't use TCP for both protocols is that UDP is much
1689 better for encapsulation, even while it is less reliable. The real
1690 problem is that when TCP would be used to encapsulate a TCP stream
1691 that's on the private network, for every packet sent there would be
1692 three ACKs sent instead of just one. Furthermore, if there would be
1693 a timeout, both TCP streams would sense the timeout, and both would
1694 start re-sending packets.
1697 @c ==================================================================
1698 @node The meta-protocol, Security, The connection, Technical information
1699 @section The meta-protocol
1701 The meta protocol is used to tie all tinc daemons together, and
1702 exchange information about which tinc daemon serves which virtual
1705 The meta protocol consists of requests that can be sent to the other
1706 side. Each request has a unique number and several parameters. All
1707 requests are represented in the standard ASCII character set. It is
1708 possible to use tools such as telnet or netcat to connect to a tinc
1709 daemon started with the --bypass-security option
1710 and to read and write requests by hand, provided that one
1711 understands the numeric codes sent.
1713 The authentication scheme is described in @ref{Authentication protocol}. After a
1714 successful authentication, the server and the client will exchange all the
1715 information about other tinc daemons and subnets they know of, so that both
1716 sides (and all the other tinc daemons behind them) have their information
1723 --------------------------------------------------------------------------
1724 origin ADD_EDGE node1 node2 21.32.43.54 655 222 0
1725 | | | | | +-> options
1726 | | | | +----> weight
1727 | | | +--------> UDP port of node2
1728 | | +----------------> real address of node2
1729 | +-------------------------> name of destination node
1730 +-------------------------------> name of source node
1732 origin ADD_SUBNET node 192.168.1.0/24
1733 | | +--> prefixlength
1734 | +--------> network address
1735 +------------------> owner of this subnet
1736 --------------------------------------------------------------------------
1739 The ADD_EDGE messages are to inform other tinc daemons that a connection between
1740 two nodes exist. The address of the destination node is available so that
1741 VPN packets can be sent directly to that node.
1743 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
1744 to certain nodes. tinc will use it to determine to which node a VPN packet has
1751 ------------------------------------------------------------------
1752 DEL_EDGE node1 node2
1753 | +----> name of destination node
1754 +----------> name of source node
1756 DEL_SUBNET node 192.168.1.0/24
1757 | | +--> prefixlength
1758 | +--------> network address
1759 +------------------> owner of this subnet
1760 ------------------------------------------------------------------
1763 In case a connection between two daemons is closed or broken, DEL_EDGE messages
1764 are sent to inform the other daemons of that fact. Each daemon will calculate a
1765 new route to the the daemons, or mark them unreachable if there isn't any.
1772 ------------------------------------------------------------------
1773 REQ_KEY origin destination
1774 | +--> name of the tinc daemon it wants the key from
1775 +----------> name of the daemon that wants the key
1777 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
1778 | | \______________/ | | +--> MAC length
1779 | | | | +-----> digest algorithm
1780 | | | +--------> cipher algorithm
1781 | | +--> 128 bits key
1782 | +--> name of the daemon that wants the key
1783 +----------> name of the daemon that uses this key
1786 +--> daemon that has changed it's packet key
1787 --------------------------------------------------------------------------
1790 The keys used to encrypt VPN packets are not sent out directly. This is
1791 because it would generate a lot of traffic on VPNs with many daemons, and
1792 chances are that not every tinc daemon will ever send a packet to every
1793 other daemon. Instead, if a daemon needs a key it sends a request for it
1794 via the meta connection of the nearest hop in the direction of the
1801 --------------------------------------------------------------------------
1804 --------------------------------------------------------------------------
1807 There is also a mechanism to check if hosts are still alive. Since network
1808 failures or a crash can cause a daemon to be killed without properly
1809 shutting down the TCP connection, this is necessary to keep an up to date
1810 connection list. PINGs are sent at regular intervals, except when there
1811 is also some other traffic. A little bit of salt (random data) is added
1812 with each PING and PONG message, to make sure that long sequences of PING/PONG
1813 messages without any other traffic won't result in known plaintext.
1815 This basically covers what is sent over the meta connection by
1819 @c ==================================================================
1820 @node Security, , The meta-protocol, Technical information
1821 @section About tinc's encryption and other security-related issues.
1825 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1826 alleged Cabal was/is an organisation that was said to keep an eye on the
1827 entire Internet. As this is exactly what you @emph{don't} want, we named
1828 the tinc project after TINC.
1831 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1832 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1833 exactly that: encrypt.
1834 tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
1835 sequence numbers and 4 byte long message authentication codes to make sure
1836 eavesdroppers cannot get and cannot change any information at all from the
1837 packets they can intercept. The encryption algorithm and message authentication
1838 algorithm can be changed in the configuration. The length of the message
1839 authentication codes is also adjustable. The length of the key for the
1840 encryption algorithm is always the default length used by OpenSSL.
1843 * Authentication protocol::
1844 * Encryption of network packets::
1848 @c ==================================================================
1849 @node Authentication protocol, Encryption of network packets, Security, Security
1850 @subsection Authentication protocol
1852 @cindex authentication
1853 A new scheme for authentication in tinc has been devised, which offers some
1854 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
1864 --------------------------------------------------------------------------
1865 client <attempts connection>
1867 server <accepts connection>
1871 +-------> name of tinc daemon
1875 +-------> name of tinc daemon
1877 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
1878 \_________________________________/
1879 +-> RSAKEYLEN bits totally random string S1,
1880 encrypted with server's public RSA key
1882 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
1883 \_________________________________/
1884 +-> RSAKEYLEN bits totally random string S2,
1885 encrypted with client's public RSA key
1888 - the client will symmetrically encrypt outgoing traffic using S1
1889 - the server will symmetrically encrypt outgoing traffic using S2
1891 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
1892 \_________________________________/
1893 +-> CHALLEN bits totally random string H1
1895 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
1896 \_________________________________/
1897 +-> CHALLEN bits totally random string H2
1899 client CHAL_REPLY 816a86
1900 +-> 160 bits SHA1 of H2
1902 server CHAL_REPLY 928ffe
1903 +-> 160 bits SHA1 of H1
1905 After the correct challenge replies are received, both ends have proved
1906 their identity. Further information is exchanged.
1908 client ACK 655 123 0
1910 | +----> estimated weight
1911 +--------> listening port of client
1913 server ACK 655 321 0
1915 | +----> estimated weight
1916 +--------> listening port of server
1917 --------------------------------------------------------------------------
1920 This new scheme has several improvements, both in efficiency and security.
1922 First of all, the server sends exactly the same kind of messages over the wire
1923 as the client. The previous versions of tinc first authenticated the client,
1924 and then the server. This scheme even allows both sides to send their messages
1925 simultaneously, there is no need to wait for the other to send something first.
1926 This means that any calculations that need to be done upon sending or receiving
1927 a message can also be done in parallel. This is especially important when doing
1928 RSA encryption/decryption. Given that these calculations are the main part of
1929 the CPU time spent for the authentication, speed is improved by a factor 2.
1931 Second, only one RSA encrypted message is sent instead of two. This reduces the
1932 amount of information attackers can see (and thus use for a cryptographic
1933 attack). It also improves speed by a factor two, making the total speedup a
1936 Third, and most important:
1937 The symmetric cipher keys are exchanged first, the challenge is done
1938 afterwards. In the previous authentication scheme, because a man-in-the-middle
1939 could pass the challenge/chal_reply phase (by just copying the messages between
1940 the two real tinc daemons), but no information was exchanged that was really
1941 needed to read the rest of the messages, the challenge/chal_reply phase was of
1942 no real use. The man-in-the-middle was only stopped by the fact that only after
1943 the ACK messages were encrypted with the symmetric cipher. Potentially, it
1944 could even send it's own symmetric key to the server (if it knew the server's
1945 public key) and read some of the metadata the server would send it (it was
1946 impossible for the mitm to read actual network packets though). The new scheme
1947 however prevents this.
1949 This new scheme makes sure that first of all, symmetric keys are exchanged. The
1950 rest of the messages are then encrypted with the symmetric cipher. Then, each
1951 side can only read received messages if they have their private key. The
1952 challenge is there to let the other side know that the private key is really
1953 known, because a challenge reply can only be sent back if the challenge is
1954 decrypted correctly, and that can only be done with knowledge of the private
1957 Fourth: the first thing that is sent via the symmetric cipher encrypted
1958 connection is a totally random string, so that there is no known plaintext (for
1959 an attacker) in the beginning of the encrypted stream.
1962 @c ==================================================================
1963 @node Encryption of network packets, , Authentication protocol, Security
1964 @subsection Encryption of network packet
1967 A data packet can only be sent if the encryption key is known to both
1968 parties, and the connection is activated. If the encryption key is not
1969 known, a request is sent to the destination using the meta connection
1970 to retrieve it. The packet is stored in a queue while waiting for the
1974 The UDP packet containing the network packet from the VPN has the following layout:
1977 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
1978 \___________________/\_____/
1980 V +---> digest algorithm
1981 Encrypted with symmetric cipher
1984 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
1985 sequence number that is added in front of the actual VPN packet, to act as a unique
1986 IV for each packet and to prevent replay attacks. A message authentication code
1987 is added to the UDP packet to prevent alteration of packets. By default the
1988 first 4 bytes of the digest are used for this, but this can be changed using
1989 the MACLength configuration variable.
1991 @c ==================================================================
1992 @node About us, Concept Index, Technical information, Top
1997 * Contact Information::
2002 @c ==================================================================
2003 @node Contact Information, Authors, About us, About us
2004 @section Contact information
2007 tinc's website is at @url{http://tinc.nl.linux.org/},
2008 this server is located in the Netherlands.
2011 We have an IRC channel on the FreeNode and OFTC IRC networks. Connect to
2012 @uref{http://www.freenode.net/, irc.freenode.net}
2014 @uref{http://www.oftc.net/, irc.oftc.net}
2015 and join channel #tinc.
2018 @c ==================================================================
2019 @node Authors, , Contact Information, About us
2023 @item Ivo Timmermans (zarq) (@email{ivo@@o2w.nl})
2024 @item Guus Sliepen (guus) (@email{guus@@sliepen.eu.org})
2027 We have received a lot of valuable input from users. With their help,
2028 tinc has become the flexible and robust tool that it is today. We have
2029 composed a list of contributions, in the file called @file{THANKS} in
2030 the source distribution.
2033 @c ==================================================================
2034 @node Concept Index, , About us, Top
2035 @c node-name, next, previous, up
2036 @unnumbered Concept Index
2038 @c ==================================================================
2042 @c ==================================================================