1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.39 2003/07/21 19:58:58 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 1.8.4.39 2003/07/21 19:58:58 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 1.8.4.39 2003/07/21 19:58:58 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/}.
277 @c Preparing your system
284 @c ==================================================================
285 @node Preparations, Installation, Introduction, Top
286 @chapter Preparations
288 This chapter contains information on how to prepare your system to
292 * Configuring the kernel::
297 @c ==================================================================
298 @node Configuring the kernel, Libraries, Preparations, Preparations
299 @section Configuring the kernel
306 If you are running Linux, chances are good that your kernel already supports
307 all the devices that tinc needs for proper operation. For example, the
308 standard kernel from Redhat Linux already has support for ethertap and netlink
309 compiled in. Debian users can use the modconf utility to select the modules.
310 If your Linux distribution supports this method of selecting devices, look out
311 for something called `ethertap', and `netlink_dev' if it is using a kernel
312 version prior to 2.4.0. In that case you will need both these devices. If you
313 are using kernel 2.4.0 or later, you need to select `tun'.
316 If you can install these devices in a similar manner, you may skip this section.
317 Otherwise, you will have to recompile the kernel in order to turn on the required features.
318 If you are unfamiliar with the process of configuring and compiling a new kernel,
319 you should read the @uref{http://howto.linuxberg.com/LDP/HOWTO/Kernel-HOWTO.html, Kernel HOWTO} first.
322 * Configuration of Linux kernels 2.1.60 up to 2.4.0::
323 * Configuration of Linux kernels 2.4.0 and higher::
324 * Configuration of FreeBSD kernels::
325 * Configuration of OpenBSD kernels::
326 * Configuration of NetBSD kernels::
327 * Configuration of Solaris kernels::
328 * Configuration of Darwin (MacOS/X) kernels::
329 * Configuration of Cygwin (Windows)::
333 @c ==================================================================
334 @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
335 @subsection Configuration of Linux kernels 2.1.60 up to 2.4.0
337 Here are the options you have to turn on when configuring a new kernel:
340 Code maturity level options
341 [*] Prompt for development and/or incomplete code/drivers
343 [*] Kernel/User netlink socket
344 <M> Netlink device emulation
345 Network device support
346 <M> Ethertap network tap
349 If you want to run more than one instance of tinc or other programs that use
350 the ethertap, you have to compile the ethertap driver as a module, otherwise
351 you can also choose to compile it directly into the kernel.
353 If you decide to build any of these as dynamic kernel modules, it's a good idea
354 to add these lines to @file{/etc/modules.conf}:
357 alias char-major-36 netlink_dev
359 options tap0 -o tap0 unit=0
361 options tap1 -o tap1 unit=1
363 alias tap@emph{N} ethertap
364 options tap@emph{N} -o tap@emph{N} unit=@emph{N}
367 Add as much alias/options lines as necessary.
370 @c ==================================================================
371 @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
372 @subsection Configuration of Linux kernels 2.4.0 and higher
374 Here are the options you have to turn on when configuring a new kernel:
377 Code maturity level options
378 [*] Prompt for development and/or incomplete code/drivers
379 Network device support
380 <M> Universal tun/tap device driver support
383 It's not necessary to compile this driver as a module, even if you are going to
384 run more than one instance of tinc.
386 If you have an early 2.4 kernel, you can choose both the tun/tap driver and the
387 `Ethertap network tap' device. This latter is marked obsolete, and chances are
388 that it won't even function correctly anymore. Make sure you select the
389 universal tun/tap driver.
391 If you decide to build the tun/tap driver as a kernel module, add these lines
392 to @file{/etc/modules.conf}:
395 alias char-major-10-200 tun
399 @c ==================================================================
400 @node Configuration of FreeBSD kernels, Configuration of OpenBSD kernels, Configuration of Linux kernels 2.4.0 and higher, Configuring the kernel
401 @subsection Configuration of FreeBSD kernels
403 This section will contain information on how to configure your FreeBSD
404 kernel to support the universal tun/tap device. For 4.1 and higher
405 versions, this is included in the default kernel configuration, for earlier
406 systems (4.0 and earlier), you need to install the universal tun/tap driver
409 Unfortunately somebody still has to write the text.
412 @c ==================================================================
413 @node Configuration of OpenBSD kernels, Configuration of NetBSD kernels, Configuration of FreeBSD kernels, Configuring the kernel
414 @subsection Configuration of OpenBSD kernels
416 This section will contain information on how to configure your OpenBSD
417 kernel to support the tun device. For 2.9 and 3.0 systems,
418 this is included in the default kernel configuration.
420 Unfortunately somebody still has to write the text.
423 @c ==================================================================
424 @node Configuration of NetBSD kernels, Configuration of Solaris kernels, Configuration of OpenBSD kernels, Configuring the kernel
425 @subsection Configuration of NetBSD kernels
427 This section will contain information on how to configure your NetBSD
428 kernel to support the tun device. For 1.5.2 systems,
429 this is included in the default kernel configuration.
431 Unfortunately somebody still has to write the text.
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 This section will contain information on how to configure your Solaris
439 kernel to support the universal tun/tap device. For Solaris 8 (SunOS 5.8),
440 this is included in the default kernel configuration.
442 Unfortunately somebody still has to write the text.
445 @c ==================================================================
446 @node Configuration of Darwin (MacOS/X) kernels, Configuration of Cygwin (Windows), Configuration of Solaris kernels, Configuring the kernel
447 @subsection Configuration of Darwin (MacOS/X) kernels
449 Darwin does not come with a tunnel driver. You must download it at
450 @uref{http://chrisp.de/en/projects/tunnel.html}. If compiling the source fails,
451 try the binary module. The tunnel driver must be loaded before starting tinc
452 with the following command:
458 Once loaded, the tunnel driver will automatically create @file{/dev/tun0}..@file{/dev/tun3}
459 and the corresponding network interfaces.
462 @c ==================================================================
463 @node Configuration of Cygwin (Windows), , Configuration of Darwin (MacOS/X) kernels, Configuring the kernel
464 @subsection Configuration of Cygwin (Windows)
466 If Cygwin hasn't already been installed, install it directly from
467 @uref{http://www.cygwin.com/}. You will also need to install the
468 CIPE driver, you can download it from @uref{http://cipe-win32.sourceforge.net}.
469 Configure the CIPE network device in the same way as you would do from the tinc-up script.
472 @c ==================================================================
473 @node Libraries, , Configuring the kernel, Preparations
478 Before you can configure or build tinc, you need to have the OpenSSL,
479 zlib and lzo libraries installed on your system. If you try to configure tinc without
480 having them installed, configure will give you an error message, and stop.
489 @c ==================================================================
490 @node OpenSSL, zlib, Libraries, Libraries
494 For all cryptography-related functions, tinc uses the functions provided
495 by the OpenSSL library.
497 If this library is not installed, you wil get an error when configuring
498 tinc for build. Support for running tinc without having OpenSSL
499 installed @emph{may} be added in the future.
501 You can use your operating system's package manager to install this if
502 available. Make sure you install the development AND runtime versions
505 If you have to install OpenSSL manually, you can get the source code
506 from @url{http://www.openssl.org/}. Instructions on how to configure,
507 build and install this package are included within the package. Please
508 make sure you build development and runtime libraries (which is the
511 If you installed the OpenSSL libraries from source, it may be necessary
512 to let configure know where they are, by passing configure one of the
513 --with-openssl-* parameters.
516 --with-openssl=DIR OpenSSL library and headers prefix
517 --with-openssl-include=DIR OpenSSL headers directory
518 (Default is OPENSSL_DIR/include)
519 --with-openssl-lib=DIR OpenSSL library directory
520 (Default is OPENSSL_DIR/lib)
524 @subsubheading License
527 Since the license under which OpenSSL is distributed is not directly
528 compatible with the terms of the GNU GPL
529 @uref{http://www.openssl.org/support/faq.html#LEGAL2}, therefore we
530 include an addition to the GPL (see also the file COPYING.README):
533 This program is released under the GPL with the additional exemption
534 that compiling, linking, and/or using OpenSSL is allowed. You may
535 provide binary packages linked to the OpenSSL libraries, provided that
536 all other requirements of the GPL are met.
540 @c ==================================================================
541 @node zlib, lzo, OpenSSL, Libraries
545 For the optional compression of UDP packets, tinc uses the functions provided
548 If this library is not installed, you wil get an error when configuring
549 tinc for build. Support for running tinc without having zlib
550 installed @emph{may} be added in the future.
552 You can use your operating system's package manager to install this if
553 available. Make sure you install the development AND runtime versions
556 If you have to install zlib manually, you can get the source code
557 from @url{http://www.gzip.org/zlib/}. Instructions on how to configure,
558 build and install this package are included within the package. Please
559 make sure you build development and runtime libraries (which is the
563 @c ==================================================================
564 @node lzo, , zlib, Libraries
568 Another form of compression is offered using the lzo library.
570 If this library is not installed, you wil get an error when configuring
571 tinc for build. Support for running tinc without having lzo
572 installed @emph{may} be added in the future.
574 You can use your operating system's package manager to install this if
575 available. Make sure you install the development AND runtime versions
578 If you have to install lzo manually, you can get the source code
579 from @url{http://www.oberhumer.com/opensource/lzo/}. Instructions on how to configure,
580 build and install this package are included within the package. Please
581 make sure you build development and runtime libraries (which is the
594 @c ==================================================================
595 @node Installation, Configuration, Preparations, Top
596 @chapter Installation
598 If you use Debian, you may want to install one of the
599 precompiled packages for your system. These packages are equipped with
600 system startup scripts and sample configurations.
602 If you cannot use one of the precompiled packages, or you want to compile tinc
603 for yourself, you can use the source. The source is distributed under
604 the GNU General Public License (GPL). Download the source from the
605 @uref{http://tinc.nl.linux.org/download, download page}, which has
606 the checksums of these files listed; you may wish to check these with
607 md5sum before continuing.
609 tinc comes in a convenient autoconf/automake package, which you can just
610 treat the same as any other package. Which is just untar it, type
611 `./configure' and then `make'.
612 More detailed instructions are in the file @file{INSTALL}, which is
613 included in the source distribution.
616 * Building and installing tinc::
621 @c ==================================================================
622 @node Building and installing tinc, System files, Installation, Installation
623 @section Building and installing tinc
625 Detailed instructions on configuring the source, building tinc and installing tinc
626 can be found in the file called @file{INSTALL}.
628 @cindex binary package
629 If you happen to have a binary package for tinc for your distribution,
630 you can use the package management tools of that distribution to install tinc.
631 The documentation that comes along with your distribution will tell you how to do that.
634 * Darwin (MacOS/X) build environment::
638 @c ==================================================================
639 @node Darwin (MacOS/X) build environment, , , Building and installing tinc
640 @subsection Darwin (MacOS/X) build environment
642 In order to build tinc on Darwin, you need to install the MacOS/X Developer Tools
643 from @uref{http://developer.apple.com/tools/macosxtools.html} and
644 a recent version of Fink from @uref{http://fink.sourceforge.net/}.
646 After installation use fink to download and install the following packages:
647 autoconf25, automake, dlcompat, m4, openssl, zlib and lzo.
650 @c ==================================================================
651 @node System files, , Building and installing tinc, Installation
652 @section System files
654 Before you can run tinc, you must make sure you have all the needed
655 files on your system.
663 @c ==================================================================
664 @node Device files, Other files, System files, System files
665 @subsection Device files
668 First, you'll need the special device file(s) that form the interface
669 between the kernel and the daemon.
671 The permissions for these files have to be such that only the super user
672 may read/write to this file. You'd want this, because otherwise
673 eavesdropping would become a bit too easy. This does, however, imply
674 that you'd have to run tincd as root.
676 If you use Linux and have a kernel version prior to 2.4.0, you have to make the
680 mknod -m 600 /dev/tap0 c 36 16
681 mknod -m 600 /dev/tap1 c 36 17
683 mknod -m 600 /dev/tap@emph{N} c 36 @emph{N+16}
686 There is a maximum of 16 ethertap devices.
688 If you use the universal tun/tap driver, you have to create the
689 following device file (unless it already exist):
692 mknod -m 600 /dev/tun c 10 200
695 If you use Linux, and you run the new 2.4 kernel using the devfs filesystem,
696 then the tun/tap device will probably be automatically generated as
699 Unlike the ethertap device, you do not need multiple device files if
700 you are planning to run multiple tinc daemons.
703 @c ==================================================================
704 @node Other files, , Device files, System files
705 @subsection Other files
707 @subsubheading @file{/etc/networks}
709 You may add a line to @file{/etc/networks} so that your VPN will get a
710 symbolic name. For example:
716 @subsubheading @file{/etc/services}
719 You may add this line to @file{/etc/services}. The effect is that you
720 may supply a @samp{tinc} as a valid port number to some programs. The
721 number 655 is registered with the IANA.
726 # Ivo Timmermans <ivo@@o2w.nl>
741 @c ==================================================================
742 @node Configuration, Running tinc, Installation, Top
743 @chapter Configuration
746 * Configuration introduction::
747 * Multiple networks::
748 * How connections work::
749 * Configuration files::
750 * Generating keypairs::
751 * Network interfaces::
752 * Example configuration::
755 @c ==================================================================
756 @node Configuration introduction, Multiple networks, Configuration, Configuration
757 @section Configuration introduction
759 @cindex Network Administrators Guide
760 Before actually starting to configure tinc and editing files,
761 make sure you have read this entire section so you know what to expect.
762 Then, make it clear to yourself how you want to organize your VPN:
763 What are the nodes (computers running tinc)?
764 What IP addresses/subnets do they have?
765 What is the network mask of the entire VPN?
766 Do you need special firewall rules?
767 Do you have to set up masquerading or forwarding rules?
768 These questions can only be answered by yourself,
769 you will not find the answers in this documentation.
770 Make sure you have an adequate understanding of networks in general.
771 A good resource on networking is the
772 @uref{http://www.linuxdoc.org/LDP/nag2/, Linux Network Administrators Guide}.
774 If you have everything clearly pictured in your mind,
775 proceed in the following order:
776 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
777 Then generate the keypairs.
778 Finally, distribute the host configuration files.
779 These steps are described in the subsections below.
782 @c ==================================================================
783 @node Multiple networks, How connections work, Configuration introduction, Configuration
784 @section Multiple networks
786 @cindex multiple networks
788 In order to allow you to run more than one tinc daemon on one computer,
789 for instance if your computer is part of more than one VPN,
790 you can assign a ``netname'' to your VPN.
791 It is not required if you only run one tinc daemon,
792 it doesn't even have to be the same on all the sites of your VPN,
793 but it is recommended that you choose one anyway.
795 We will asume you use a netname throughout this document.
796 This means that you call tincd with the -n argument,
797 which will assign a netname to this daemon.
799 The effect of this is that the daemon will set its configuration
800 ``root'' to /etc/tinc/netname/, where netname is your argument to the -n
801 option. You'll notice that it appears in syslog as ``tinc.netname''.
803 However, it is not strictly necessary that you call tinc with the -n
804 option. In this case, the network name would just be empty, and it will
805 be used as such. tinc now looks for files in /etc/tinc/, instead of
806 /etc/tinc/netname/; the configuration file should be /etc/tinc/tinc.conf,
807 and the host configuration files are now expected to be in /etc/tinc/hosts/.
809 But it is highly recommended that you use this feature of tinc, because
810 it will be so much clearer whom your daemon talks to. Hence, we will
811 assume that you use it.
814 @c ==================================================================
815 @node How connections work, Configuration files, Multiple networks, Configuration
816 @section How connections work
818 When tinc starts up, it parses the command-line options and then
819 reads in the configuration file tinc.conf.
820 If it sees one or more `ConnectTo' values pointing to other tinc daemons in that file,
821 it will try to connect to those other daemons.
822 Whether this succeeds or not and whether `ConnectTo' is specified or not,
823 tinc will listen for incoming connection from other deamons.
824 If you did specify a `ConnectTo' value and the other side is not responding,
825 tinc will keep retrying.
826 This means that once started, tinc will stay running until you tell it to stop,
827 and failures to connect to other tinc daemons will not stop your tinc daemon
828 for trying again later.
829 This means you don't have to intervene if there are temporary network problems.
833 There is no real distinction between a server and a client in tinc.
834 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
835 and one which does specify such a value as a client.
836 It does not matter if two tinc daemons have a `ConnectTo' value pointing to each other however.
839 @c ==================================================================
840 @node Configuration files, Generating keypairs, How connections work, Configuration
841 @section Configuration files
843 The actual configuration of the daemon is done in the file
844 @file{/etc/tinc/netname/tinc.conf} and at least one other file in the directory
845 @file{/etc/tinc/netname/hosts/}.
847 These file consists of comments (lines started with a #) or assignments
854 The variable names are case insensitive, and any spaces, tabs, newlines
855 and carriage returns are ignored. Note: it is not required that you put
856 in the `=' sign, but doing so improves readability. If you leave it
857 out, remember to replace it with at least one space character.
859 In this section all valid variables are listed in alphabetical order.
860 The default value is given between parentheses,
861 other comments are between square brackets and
862 required directives are given in @strong{bold}.
865 * Main configuration variables::
866 * Host configuration variables::
871 @c ==================================================================
872 @node Main configuration variables, Host configuration variables, Configuration files, Configuration files
873 @subsection Main configuration variables
876 @cindex AddressFamily
877 @item AddressFamily = <ipv4|ipv6|any> (any)
878 This option affects the address family of listening and outgoing sockets.
879 If "any" is selected, then depending on the operating system
880 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
882 @cindex BindToAddress
883 @item BindToAddress = <address> [experimental]
884 If your computer has more than one IPv4 or IPv6 address, tinc
885 will by default listen on all of them for incoming connections.
886 It is possible to bind only to a single address with this variable.
888 This option may not work on all platforms.
890 @cindex BindToInterface
891 @item BindToInterface = <interface> [experimental]
892 If you have more than one network interface in your computer, tinc will
893 by default listen on all of them for incoming connections. It is
894 possible to bind tinc to a single interface like eth0 or ppp0 with this
897 This option may not work on all platforms.
900 @item @strong{ConnectTo = <name>}
901 Specifies which other tinc daemon to connect to on startup.
902 Multiple ConnectTo variables may be specified,
903 in which case outgoing connections to each specified tinc daemon are made.
904 The names should be known to this tinc daemon
905 (i.e., there should be a host configuration file for the name on the ConnectTo line).
907 If you don't specify a host with ConnectTo,
908 tinc won't try to connect to other daemons at all,
909 and will instead just listen for incoming connections.
912 @item @strong{Device = <device>} (/dev/tap0 or /dev/net/tun)
913 The virtual network device to use. Note that you can only use one device per
914 daemon. See also @ref{Device files}.
917 @item Hostnames = <yes|no> (no)
918 This option selects whether IP addresses (both real and on the VPN)
919 should be resolved. Since DNS lookups are blocking, it might affect
920 tinc's efficiency, even stopping the daemon for a few seconds everytime
921 it does a lookup if your DNS server is not responding.
923 This does not affect resolving hostnames to IP addresses from the
927 @item Interface = <interface>
928 Defines the name of the interface corresponding to the virtual network device.
929 Depending on the operating system and the type of device this may or may not actually set the name.
930 Currently this option only affects the Linux tun/tap device.
933 @item Mode = <router|switch|hub> (router)
934 This option selects the way packets are routed to other daemons.
940 variables in the host configuration files will be used to form a routing table.
941 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
945 In this mode the MAC addresses of the packets on the VPN will be used to
946 dynamically create a routing table just like an Ethernet switch does.
947 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
948 at the cost of frequent broadcast ARP requests and routing table updates.
952 This mode is almost the same as the switch mode, but instead
953 every packet will be broadcast to the other daemons
954 while no routing table is managed.
958 @item KeyExpire = <seconds> (3600)
959 This option controls the time the encryption keys used to encrypt the data
960 are valid. It is common practice to change keys at regular intervals to
961 make it even harder for crackers, even though it is thought to be nearly
962 impossible to crack a single key.
965 @item MACExpire = <seconds> (600)
966 This option controls the amount of time MAC addresses are kept before they are removed.
967 This only has effect when Mode is set to "switch".
970 @item @strong{Name = <name>}
971 This is a symbolic name for this connection. It can be anything
974 @item PingTimeout = <seconds> (60)
975 The number of seconds of inactivity that tinc will wait before sending a
976 probe to the other end. If that other end doesn't answer within that
977 same amount of seconds, the connection is terminated, and the others
978 will be notified of this.
980 @cindex PriorityInheritance
981 @item PriorityInheritance = <yes|no> (no) [experimental]
982 When this option is enabled the value of the TOS field of tunneled IPv4 packets
983 will be inherited by the UDP packets that are sent out.
986 @item PrivateKey = <key> [obsolete]
987 This is the RSA private key for tinc. However, for safety reasons it is
988 advised to store private keys of any kind in separate files. This prevents
989 accidental eavesdropping if you are editting the configuration file.
991 @cindex PrivateKeyFile
992 @item @strong{PrivateKeyFile = <path>} [recommended]
993 This is the full path name of the RSA private key file that was
994 generated by ``tincd --generate-keys''. It must be a full path, not a
997 Note that there must be exactly one of PrivateKey
999 specified in the configuration file.
1004 @c ==================================================================
1005 @node Host configuration variables, How to configure, Main configuration variables, Configuration files
1006 @subsection Host configuration variables
1010 @item @strong{Address = <IP address|hostname>} [recommended]
1011 This variable is only required if you want to connect to this host. It
1012 must resolve to the external IP address where the host can be reached,
1013 not the one that is internal to the VPN.
1016 @item Cipher = <cipher> (blowfish)
1017 The symmetric cipher algorithm used to encrypt UDP packets.
1018 Any cipher supported by OpenSSL is recognized.
1021 @item Compression = <level> (0)
1022 This option sets the level of compression used for UDP packets.
1023 Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
1024 10 (fast lzo) and 11 (best lzo).
1027 @item Digest = <digest> (sha1)
1028 The digest algorithm used to authenticate UDP packets.
1029 Any digest supported by OpenSSL is recognized.
1030 Furthermore, specifying "none" will turn off packet authentication.
1032 @cindex IndirectData
1033 @item IndirectData = <yes|no> (no)
1034 This option specifies whether other tinc daemons besides the one you
1035 specified with ConnectTo can make a direct connection to you. This is
1036 especially useful if you are behind a firewall and it is impossible to
1037 make a connection from the outside to your tinc daemon. Otherwise, it
1038 is best to leave this option out or set it to no.
1041 @item MACLength = <length> (4)
1042 The length of the message authentication code used to authenticate UDP packets.
1043 Can be anything from 0
1044 up to the length of the digest produced by the digest algorithm.
1047 @item Port = <port> (655)
1048 This is the port this tinc daemon listens on.
1049 You can use decimal portnumbers or symbolic names (as listed in /etc/services).
1052 @item PublicKey = <key> [obsolete]
1053 This is the RSA public key for this host.
1055 @cindex PublicKeyFile
1056 @item PublicKeyFile = <path> [obsolete]
1057 This is the full path name of the RSA public key file that was generated
1058 by ``tincd --generate-keys''. It must be a full path, not a relative
1062 From version 1.0pre4 on tinc will store the public key directly into the
1063 host configuration file in PEM format, the above two options then are not
1064 necessary. Either the PEM format is used, or exactly
1065 @strong{one of the above two options} must be specified
1066 in each host configuration file, if you want to be able to establish a
1067 connection with that host.
1070 @item Subnet = <address[/prefixlength]>
1071 The subnet which this tinc daemon will serve.
1072 tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
1073 If the packet matches a subnet,
1074 it will be sent to the daemon who has this subnet in his host configuration file.
1075 Multiple subnet lines can be specified for each daemon.
1077 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1078 in which case a subnet consisting of only that single address is assumed,
1079 or they can be a IPv4 or IPv6 network address with a prefixlength.
1080 Shorthand notations are not supported.
1081 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1082 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1083 Note that subnets like 192.168.1.1/24 are invalid!
1084 Read a networking HOWTO/FAQ/guide if you don't understand this.
1085 IPv6 subnets are notated like fec0:0:0:1:0:0:0:0/64.
1086 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1088 @cindex CIDR notation
1089 prefixlength is the number of bits set to 1 in the netmask part; for
1090 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1091 /22. This conforms to standard CIDR notation as described in
1092 @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
1095 @item TCPonly = <yes|no> (no) [experimental]
1096 If this variable is set to yes, then the packets are tunnelled over a
1097 TCP connection instead of a UDP connection. This is especially useful
1098 for those who want to run a tinc daemon from behind a masquerading
1099 firewall, or if UDP packet routing is disabled somehow.
1100 Setting this options also implicitly sets IndirectData.
1104 @c ==================================================================
1105 @node How to configure, , Host configuration variables, Configuration files
1106 @subsection How to configure
1108 @subsubheading Step 1. Creating the main configuration file
1110 The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
1111 Adapt the following example to create a basic configuration file:
1114 Name = @emph{yourname}
1115 Device = @emph{/dev/tap0}
1116 PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv
1119 Then, if you know to which other tinc daemon(s) yours is going to connect,
1120 add `ConnectTo' values.
1122 @subsubheading Step 2. Creating your host configuration file
1124 If you added a line containing `Name = yourname' in the main configuarion file,
1125 you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
1126 Adapt the following example to create a host configuration file:
1129 Address = @emph{your.real.hostname.org}
1130 Subnet = @emph{192.168.1.0/24}
1133 You can also use an IP address instead of a hostname.
1134 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1135 If you have multiple address ranges you can specify more than one `Subnet'.
1136 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).
1139 @c ==================================================================
1140 @node Generating keypairs, Network interfaces, Configuration files, Configuration
1141 @section Generating keypairs
1143 @cindex key generation
1144 Now that you have already created the main configuration file and your host configuration file,
1145 you can easily create a public/private keypair by entering the following command:
1148 tincd -n @emph{netname} -K
1151 tinc will generate a public and a private key and ask you where to put them.
1152 Just press enter to accept the defaults.
1155 @c ==================================================================
1156 @node Network interfaces, Example configuration, Generating keypairs, Configuration
1157 @section Network interfaces
1159 Before tinc can start transmitting data over the tunnel, it must
1160 set up the virtual network interface.
1162 First, decide which IP addresses you want to have associated with these
1163 devices, and what network mask they must have.
1165 tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1166 which will also create a network interface called something like `tun0', `tap0', or,
1167 if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.
1170 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1171 to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
1172 will be executed. When tinc exits, it will execute the script named
1173 @file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
1175 An example @file{tinc-up} script:
1179 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1182 This script gives the interface an IP address and a netmask.
1183 The kernel will also automatically add a route to this interface, so normally you don't need
1184 to add route commands to the @file{tinc-up} script.
1185 The kernel will also bring the interface up after this command.
1187 The netmask is the mask of the @emph{entire} VPN network, not just your
1191 @c ==================================================================
1192 @node Example configuration, , Network interfaces, Configuration
1193 @section Example configuration
1197 Imagine the following situation. Branch A of our example `company' wants to connect
1198 three branch offices in B, C and D using the Internet. All four offices
1199 have a 24/7 connection to the Internet.
1201 A is going to serve as the center of the network. B and C will connect
1202 to A, and D will connect to C. Each office will be assigned their own IP
1206 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1207 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1208 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1209 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1212 ``gateway'' is the VPN IP address of the machine that is running the
1213 tincd. ``internet IP'' is the IP address of the firewall, which does not
1214 need to run tincd, but it must do a port forwarding of TCP&UDP on port
1215 655 (unless otherwise configured).
1217 In this example, it is assumed that eth0 is the interface that points to
1218 the inner (physical) LAN of the office, although this could also be the
1219 same as the interface that leads to the Internet. The configuration of
1220 the real interface is also shown as a comment, to give you an idea of
1221 how these example host is set up. All branches use the netname `company'
1222 for this particular VPN.
1224 @subsubheading For Branch A
1226 @emph{BranchA} would be configured like this:
1228 In @file{/etc/tinc/company/tinc-up}:
1231 # Real interface of internal network:
1232 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
1234 ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
1237 and in @file{/etc/tinc/company/tinc.conf}:
1241 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1245 On all hosts, /etc/tinc/company/hosts/BranchA contains:
1248 Subnet = 10.1.0.0/16
1251 -----BEGIN RSA PUBLIC KEY-----
1253 -----END RSA PUBLIC KEY-----
1256 Note that the IP addresses of eth0 and tap0 are the same.
1257 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1258 It is in fact recommended to give give both real internal network interfaces and tap interfaces the same IP address,
1259 since that will make things a lot easier to remember and set up.
1262 @subsubheading For Branch B
1264 In @file{/etc/tinc/company/tinc-up}:
1267 # Real interface of internal network:
1268 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
1270 ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
1273 and in @file{/etc/tinc/company/tinc.conf}:
1278 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1281 Note here that the internal address (on eth0) doesn't have to be the
1282 same as on the tap0 device. Also, ConnectTo is given so that no-one can
1283 connect to this node.
1285 On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:
1288 Subnet = 10.2.0.0/16
1291 -----BEGIN RSA PUBLIC KEY-----
1293 -----END RSA PUBLIC KEY-----
1297 @subsubheading For Branch C
1299 In @file{/etc/tinc/company/tinc-up}:
1302 # Real interface of internal network:
1303 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
1305 ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
1308 and in @file{/etc/tinc/company/tinc.conf}:
1316 C already has another daemon that runs on port 655, so they have to
1317 reserve another port for tinc. It knows the portnumber it has to listen on
1318 from it's own host configuration file.
1320 On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:
1324 Subnet = 10.3.0.0/16
1327 -----BEGIN RSA PUBLIC KEY-----
1329 -----END RSA PUBLIC KEY-----
1333 @subsubheading For Branch D
1335 In @file{/etc/tinc/company/tinc-up}:
1338 # Real interface of internal network:
1339 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
1341 ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
1344 and in @file{/etc/tinc/company/tinc.conf}:
1349 Device = /dev/net/tun
1350 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1353 D will be connecting to C, which has a tincd running for this network on
1354 port 2000. It knows the port number from the host configuration file.
1355 Also note that since D uses the tun/tap driver, the network interface
1356 will not be called `tun' or `tap0' or something like that, but will
1357 have the same name as netname.
1359 On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:
1362 Subnet = 10.4.0.0/16
1365 -----BEGIN RSA PUBLIC KEY-----
1367 -----END RSA PUBLIC KEY-----
1370 @subsubheading Key files
1372 A, B, C and D all have generated a public/private keypair with the following command:
1378 The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
1379 the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
1380 During key generation, tinc automatically guesses the right filenames based on the -n option and
1381 the Name directive in the @file{tinc.conf} file (if it is available).
1383 @subsubheading Starting
1385 After each branch has finished configuration and they have distributed
1386 the host configuration files amongst them, they can start their tinc daemons.
1387 They don't necessarily have to wait for the other branches to have started
1388 their daemons, tinc will try connecting until they are available.
1391 @c ==================================================================
1392 @node Running tinc, Technical information, Configuration, Top
1393 @chapter Running tinc
1395 If everything else is done, you can start tinc by typing the following command:
1398 tincd -n @emph{netname}
1402 tinc will detach from the terminal and continue to run in the background like a good daemon.
1403 If there are any problems however you can try to increase the debug level
1404 and look in the syslog to find out what the problems are.
1412 @c ==================================================================
1413 @node Runtime options, Error messages, , Running tinc
1414 @section Runtime options
1416 Besides the settings in the configuration file, tinc also accepts some
1417 command line options.
1419 @cindex command line
1420 @cindex runtime options
1424 @item --bypass-security
1425 Disables encryption and authentication.
1426 Only useful for debugging.
1428 @item -c, --config=PATH
1429 Read configuration options from the directory PATH. The default is
1430 @file{/etc/tinc/netname/}.
1433 @item -d, --debug=LEVEL
1434 Set debug level to LEVEL. The higher the debug level, the more gets
1435 logged. Everything goes via syslog.
1437 @item -K, --generate-keys[=BITS]
1438 Generate public/private keypair of BITS length. If BITS is not specified,
1439 1024 is the default. tinc will ask where you want to store the files,
1440 but will default to the configuration directory (you can use the -c or -n option
1441 in combination with -K). After that, tinc will quit.
1444 Display a short reminder of these runtime options and terminate.
1446 @item -k, --kill[=SIGNAL]
1447 Attempt to kill a running tincd (optionally with the specified SIGNAL instead of SIGTERM) and exit.
1448 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1450 @item -n, --net=NETNAME
1451 Connect to net NETNAME. @xref{Multiple networks}.
1453 @item -D, --no-detach
1454 Don't fork and detach.
1455 This will also disable the automatic restart mechanism for fatal errors.
1458 Lock tinc into main memory.
1459 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1462 Output version information and exit.
1467 @c ==================================================================
1468 @node Error messages, , Runtime options, Running tinc
1469 @section Error messages
1471 What follows is a list of the most common error messages you can see
1472 when configuring tinc. Most of these messages are visible in the syslog
1473 only, so keep an eye on it!
1476 @item Could not open /dev/tap0: No such device
1479 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1480 @item You forgot to compile `Netlink device emulation' in the kernel.
1483 @item Can't write to /dev/net/tun: No such device
1486 @item You forgot to `modprobe tun'.
1487 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1490 @item Packet with destination 1.2.3.4 is looping back to us!
1493 @item Something is not configured right. Packets are being sent out to the
1494 virtual network device, but according to the Subnet directives in your host configuration
1495 file, those packets should go to your own host. Most common mistake is that
1496 you have a Subnet line in your host configuration file with a prefix length which is
1497 just as large as the prefix of the virtual network interface. The latter should in almost all
1498 cases be larger. Rethink your configuration.
1499 Note that you will only see this message if you specified a debug
1500 level of 5 or higher!
1501 @item Chances are that a `Subnet = ...' line in the host configuration file of this tinc daemon is wrong.
1502 Change it to a subnet that is accepted locally by another interface,
1503 or if that is not the case, try changing the prefix length into /32.
1506 @item Network doesn't work, syslog shows only packets of length 46
1508 @item Network address and prefix length do not match!
1511 @item The Subnet field must contain a @emph{network} address.
1512 @item If you only want to use one IP address, set the netmask to /32.
1515 @item This is a bug: net.c:253: 24: Some error
1518 @item This is something that should not have happened.
1519 Please report this, and tell us exactly what went wrong before you got
1520 this message. In normal operation, these errors should not occur.
1523 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1526 @item You must specify the complete pathname.
1527 Specifying a relative path does not make sense here. tinc changes its
1528 directory to / when starting (to avoid keeping a mount point busy).
1533 @c ==================================================================
1534 @node Technical information, About us, Running tinc, Top
1535 @chapter Technical information
1540 * The meta-protocol::
1545 @c ==================================================================
1546 @node The connection, The meta-protocol, Technical information, Technical information
1547 @section The connection
1550 tinc is a daemon that takes VPN data and transmit that to another host
1551 computer over the existing Internet infrastructure.
1555 * The meta-connection::
1559 @c ==================================================================
1560 @node The UDP tunnel, The meta-connection, The connection, The connection
1561 @subsection The UDP tunnel
1563 @cindex virtual network device
1565 The data itself is read from a character device file, the so-called
1566 @emph{virtual network device}. This device is associated with a network
1567 interface. Any data sent to this interface can be read from the device,
1568 and any data written to the device gets sent from the interface.
1569 There are two possible types of virtual network devices:
1570 `tun' style, which are point-to-point devices which can only handle IPv4 and/or IPv6 packets,
1571 and `tap' style, which are Ethernet devices and handle complete Ethernet frames.
1573 So when tinc reads an Ethernet frame from the device, it determines its
1574 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
1575 packets. Depending on the Subnet lines, it will send the packets off to their destination IP address.
1576 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
1577 to deduce the destination of the packets.
1578 Since the latter modes only depend on the link layer information,
1579 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
1580 However, only `tap' style devices provide this information.
1582 After the destination has been determined,
1583 the packet will be compressed (optionally),
1584 a sequence number will be added to the packet,
1585 the packet will then be encrypted
1586 and a message authentication code will be appended.
1588 @cindex encapsulating
1590 When that is done, time has come to actually transport the
1591 packet to the destination computer. We do this by sending the packet
1592 over an UDP connection to the destination host. This is called
1593 @emph{encapsulating}, the VPN packet (though now encrypted) is
1594 encapsulated in another IP datagram.
1596 When the destination receives this packet, the same thing happens, only
1597 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
1598 checks the sequence number
1599 and writes the decrypted information to its own virtual network device.
1601 If the virtual network device is a `tun' device (a point-to-point tunnel),
1602 there is no problem for the kernel to accept a packet.
1603 However, if it is a `tap' device (this is the only available type on FreeBSD),
1604 the destination MAC address must match that of the virtual network interface.
1605 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC
1606 can not be known by the sending host.
1607 tinc solves this by letting the receiving end detect the MAC address of its own virtual network interface
1608 and overwriting the destination MAC address of the received packet.
1610 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
1611 In those modes every interface should have a unique MAC address, so make sure they are not the same.
1612 Because switch and hub modes rely on MAC addresses to function correctly,
1613 these modes cannot be used on the following operating systems which don't have a `tap' style virtual network device:
1614 OpenBSD, NetBSD, Darwin and Solaris.
1617 @c ==================================================================
1618 @node The meta-connection, , The UDP tunnel, The connection
1619 @subsection The meta-connection
1621 Having only a UDP connection available is not enough. Though suitable
1622 for transmitting data, we want to be able to reliably send other
1623 information, such as routing and session key information to somebody.
1626 TCP is a better alternative, because it already contains protection
1627 against information being lost, unlike UDP.
1629 So we establish two connections. One for the encrypted VPN data, and one
1630 for other information, the meta-data. Hence, we call the second
1631 connection the meta-connection. We can now be sure that the
1632 meta-information doesn't get lost on the way to another computer.
1634 @cindex data-protocol
1635 @cindex meta-protocol
1636 Like with any communication, we must have a protocol, so that everybody
1637 knows what everything stands for, and how she should react. Because we
1638 have two connections, we also have two protocols. The protocol used for
1639 the UDP data is the ``data-protocol,'' the other one is the
1642 The reason we don't use TCP for both protocols is that UDP is much
1643 better for encapsulation, even while it is less reliable. The real
1644 problem is that when TCP would be used to encapsulate a TCP stream
1645 that's on the private network, for every packet sent there would be
1646 three ACKs sent instead of just one. Furthermore, if there would be
1647 a timeout, both TCP streams would sense the timeout, and both would
1648 start re-sending packets.
1651 @c ==================================================================
1652 @node The meta-protocol, Security, The connection, Technical information
1653 @section The meta-protocol
1655 The meta protocol is used to tie all tinc daemons together, and
1656 exchange information about which tinc daemon serves which virtual
1659 The meta protocol consists of requests that can be sent to the other
1660 side. Each request has a unique number and several parameters. All
1661 requests are represented in the standard ASCII character set. It is
1662 possible to use tools such as telnet or netcat to connect to a tinc
1663 daemon started with the --bypass-security option
1664 and to read and write requests by hand, provided that one
1665 understands the numeric codes sent.
1667 The authentication scheme is described in @ref{Authentication protocol}. After a
1668 successful authentication, the server and the client will exchange all the
1669 information about other tinc daemons and subnets they know of, so that both
1670 sides (and all the other tinc daemons behind them) have their information
1677 --------------------------------------------------------------------------
1678 origin ADD_EDGE node1 node2 21.32.43.54 655 222 0
1679 | | | | | +-> options
1680 | | | | +----> weight
1681 | | | +--------> UDP port of node2
1682 | | +----------------> real address of node2
1683 | +-------------------------> name of destination node
1684 +-------------------------------> name of source node
1686 origin ADD_SUBNET node 192.168.1.0/24
1687 | | +--> prefixlength
1688 | +--------> network address
1689 +------------------> owner of this subnet
1690 --------------------------------------------------------------------------
1693 The ADD_EDGE messages are to inform other tinc daemons that a connection between
1694 two nodes exist. The address of the destination node is available so that
1695 VPN packets can be sent directly to that node.
1697 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
1698 to certain nodes. tinc will use it to determine to which node a VPN packet has
1705 ------------------------------------------------------------------
1706 DEL_EDGE node1 node2
1707 | +----> name of destination node
1708 +----------> name of source node
1710 DEL_SUBNET node 192.168.1.0/24
1711 | | +--> prefixlength
1712 | +--------> network address
1713 +------------------> owner of this subnet
1714 ------------------------------------------------------------------
1717 In case a connection between two daemons is closed or broken, DEL_EDGE messages
1718 are sent to inform the other daemons of that fact. Each daemon will calculate a
1719 new route to the the daemons, or mark them unreachable if there isn't any.
1726 ------------------------------------------------------------------
1727 REQ_KEY origin destination
1728 | +--> name of the tinc daemon it wants the key from
1729 +----------> name of the daemon that wants the key
1731 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
1732 | | \______________/ | | +--> MAC length
1733 | | | | +-----> digest algorithm
1734 | | | +--------> cipher algorithm
1735 | | +--> 128 bits key
1736 | +--> name of the daemon that wants the key
1737 +----------> name of the daemon that uses this key
1740 +--> daemon that has changed it's packet key
1741 --------------------------------------------------------------------------
1744 The keys used to encrypt VPN packets are not sent out directly. This is
1745 because it would generate a lot of traffic on VPNs with many daemons, and
1746 chances are that not every tinc daemon will ever send a packet to every
1747 other daemon. Instead, if a daemon needs a key it sends a request for it
1748 via the meta connection of the nearest hop in the direction of the
1755 --------------------------------------------------------------------------
1758 --------------------------------------------------------------------------
1761 There is also a mechanism to check if hosts are still alive. Since network
1762 failures or a crash can cause a daemon to be killed without properly
1763 shutting down the TCP connection, this is necessary to keep an up to date
1764 connection list. PINGs are sent at regular intervals, except when there
1765 is also some other traffic. A little bit of salt (random data) is added
1766 with each PING and PONG message, to make sure that long sequences of PING/PONG
1767 messages without any other traffic won't result in known plaintext.
1769 This basically covers what is sent over the meta connection by
1773 @c ==================================================================
1774 @node Security, , The meta-protocol, Technical information
1775 @section About tinc's encryption and other security-related issues.
1779 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1780 alleged Cabal was/is an organisation that was said to keep an eye on the
1781 entire Internet. As this is exactly what you @emph{don't} want, we named
1782 the tinc project after TINC.
1785 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1786 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1787 exactly that: encrypt.
1788 tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
1789 sequence numbers and 4 byte long message authentication codes to make sure
1790 eavesdroppers cannot get and cannot change any information at all from the
1791 packets they can intercept. The encryption algorithm and message authentication
1792 algorithm can be changed in the configuration. The length of the message
1793 authentication codes is also adjustable. The length of the key for the
1794 encryption algorithm is always the default length used by OpenSSL.
1797 * Authentication protocol::
1798 * Encryption of network packets::
1802 @c ==================================================================
1803 @node Authentication protocol, Encryption of network packets, Security, Security
1804 @subsection Authentication protocol
1806 @cindex authentication
1807 A new scheme for authentication in tinc has been devised, which offers some
1808 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
1818 --------------------------------------------------------------------------
1819 client <attempts connection>
1821 server <accepts connection>
1825 +-------> name of tinc daemon
1829 +-------> name of tinc daemon
1831 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
1832 \_________________________________/
1833 +-> RSAKEYLEN bits totally random string S1,
1834 encrypted with server's public RSA key
1836 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
1837 \_________________________________/
1838 +-> RSAKEYLEN bits totally random string S2,
1839 encrypted with client's public RSA key
1842 - the client will symmetrically encrypt outgoing traffic using S1
1843 - the server will symmetrically encrypt outgoing traffic using S2
1845 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
1846 \_________________________________/
1847 +-> CHALLEN bits totally random string H1
1849 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
1850 \_________________________________/
1851 +-> CHALLEN bits totally random string H2
1853 client CHAL_REPLY 816a86
1854 +-> 160 bits SHA1 of H2
1856 server CHAL_REPLY 928ffe
1857 +-> 160 bits SHA1 of H1
1859 After the correct challenge replies are received, both ends have proved
1860 their identity. Further information is exchanged.
1862 client ACK 655 123 0
1864 | +----> estimated weight
1865 +--------> listening port of client
1867 server ACK 655 321 0
1869 | +----> estimated weight
1870 +--------> listening port of server
1871 --------------------------------------------------------------------------
1874 This new scheme has several improvements, both in efficiency and security.
1876 First of all, the server sends exactly the same kind of messages over the wire
1877 as the client. The previous versions of tinc first authenticated the client,
1878 and then the server. This scheme even allows both sides to send their messages
1879 simultaneously, there is no need to wait for the other to send something first.
1880 This means that any calculations that need to be done upon sending or receiving
1881 a message can also be done in parallel. This is especially important when doing
1882 RSA encryption/decryption. Given that these calculations are the main part of
1883 the CPU time spent for the authentication, speed is improved by a factor 2.
1885 Second, only one RSA encrypted message is sent instead of two. This reduces the
1886 amount of information attackers can see (and thus use for a cryptographic
1887 attack). It also improves speed by a factor two, making the total speedup a
1890 Third, and most important:
1891 The symmetric cipher keys are exchanged first, the challenge is done
1892 afterwards. In the previous authentication scheme, because a man-in-the-middle
1893 could pass the challenge/chal_reply phase (by just copying the messages between
1894 the two real tinc daemons), but no information was exchanged that was really
1895 needed to read the rest of the messages, the challenge/chal_reply phase was of
1896 no real use. The man-in-the-middle was only stopped by the fact that only after
1897 the ACK messages were encrypted with the symmetric cipher. Potentially, it
1898 could even send it's own symmetric key to the server (if it knew the server's
1899 public key) and read some of the metadata the server would send it (it was
1900 impossible for the mitm to read actual network packets though). The new scheme
1901 however prevents this.
1903 This new scheme makes sure that first of all, symmetric keys are exchanged. The
1904 rest of the messages are then encrypted with the symmetric cipher. Then, each
1905 side can only read received messages if they have their private key. The
1906 challenge is there to let the other side know that the private key is really
1907 known, because a challenge reply can only be sent back if the challenge is
1908 decrypted correctly, and that can only be done with knowledge of the private
1911 Fourth: the first thing that is send via the symmetric cipher encrypted
1912 connection is a totally random string, so that there is no known plaintext (for
1913 an attacker) in the beginning of the encrypted stream.
1916 @c ==================================================================
1917 @node Encryption of network packets, , Authentication protocol, Security
1918 @subsection Encryption of network packet
1921 A data packet can only be sent if the encryption key is known to both
1922 parties, and the connection is activated. If the encryption key is not
1923 known, a request is sent to the destination using the meta connection
1924 to retrieve it. The packet is stored in a queue while waiting for the
1928 The UDP packet containing the network packet from the VPN has the following layout:
1931 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
1932 \___________________/\_____/
1934 V +---> digest algorithm
1935 Encrypted with symmetric cipher
1938 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
1939 sequence number that is added in front of the actual VPN packet, to act as a unique
1940 IV for each packet and to prevent replay attacks. A message authentication code
1941 is added to the UDP packet to prevent alteration of packets. By default the
1942 first 4 bytes of the digest are used for this, but this can be changed using
1943 the MACLength configuration variable.
1945 @c ==================================================================
1946 @node About us, Concept Index, Technical information, Top
1951 * Contact Information::
1956 @c ==================================================================
1957 @node Contact Information, Authors, About us, About us
1958 @section Contact information
1961 tinc's website is at @url{http://tinc.nl.linux.org/},
1962 this server is located in the Netherlands.
1965 We have an IRC channel on the FreeNode IRC network. Connect to
1966 @uref{http://www.freenode.net/, irc.freenode.net}
1967 and join channel #tinc.
1970 @c ==================================================================
1971 @node Authors, , Contact Information, About us
1975 @item Ivo Timmermans (zarq) (@email{ivo@@o2w.nl})
1976 @item Guus Sliepen (guus) (@email{guus@@sliepen.eu.org})
1979 We have received a lot of valuable input from users. With their help,
1980 tinc has become the flexible and robust tool that it is today. We have
1981 composed a list of contributions, in the file called @file{THANKS} in
1982 the source distribution.
1985 @c ==================================================================
1986 @node Concept Index, , About us, Top
1987 @c node-name, next, previous, up
1988 @unnumbered Concept Index
1990 @c ==================================================================
1994 @c ==================================================================