1 \input texinfo @c -*-texinfo-*-
2 @c $Id: tinc.texi,v 1.8.4.40 2003/07/30 09:22:29 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 1.8.4.40 2003/07/30 09:22:29 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 1.8.4.40 2003/07/30 09:22:29 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, 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.
675 However, when compiled using MinGW, tinc will not be able to start
676 scripts or be able to receive signals.
679 @c ==================================================================
680 @node System files, , Building and installing tinc, Installation
681 @section System files
683 Before you can run tinc, you must make sure you have all the needed
684 files on your system.
692 @c ==================================================================
693 @node Device files, Other files, System files, System files
694 @subsection Device files
697 First, you'll need the special device file(s) that form the interface
698 between the kernel and the daemon.
700 The permissions for these files have to be such that only the super user
701 may read/write to this file. You'd want this, because otherwise
702 eavesdropping would become a bit too easy. This does, however, imply
703 that you'd have to run tincd as root.
705 If you use Linux and have a kernel version prior to 2.4.0, you have to make the
709 mknod -m 600 /dev/tap0 c 36 16
710 mknod -m 600 /dev/tap1 c 36 17
712 mknod -m 600 /dev/tap@emph{N} c 36 @emph{N+16}
715 There is a maximum of 16 ethertap devices.
717 If you use the universal tun/tap driver, you have to create the
718 following device file (unless it already exist):
721 mknod -m 600 /dev/tun c 10 200
724 If you use Linux, and you run the new 2.4 kernel using the devfs filesystem,
725 then the tun/tap device will probably be automatically generated as
728 Unlike the ethertap device, you do not need multiple device files if
729 you are planning to run multiple tinc daemons.
732 @c ==================================================================
733 @node Other files, , Device files, System files
734 @subsection Other files
736 @subsubheading @file{/etc/networks}
738 You may add a line to @file{/etc/networks} so that your VPN will get a
739 symbolic name. For example:
745 @subsubheading @file{/etc/services}
748 You may add this line to @file{/etc/services}. The effect is that you
749 may supply a @samp{tinc} as a valid port number to some programs. The
750 number 655 is registered with the IANA.
755 # Ivo Timmermans <ivo@@o2w.nl>
770 @c ==================================================================
771 @node Configuration, Running tinc, Installation, Top
772 @chapter Configuration
775 * Configuration introduction::
776 * Multiple networks::
777 * How connections work::
778 * Configuration files::
779 * Generating keypairs::
780 * Network interfaces::
781 * Example configuration::
784 @c ==================================================================
785 @node Configuration introduction, Multiple networks, Configuration, Configuration
786 @section Configuration introduction
788 @cindex Network Administrators Guide
789 Before actually starting to configure tinc and editing files,
790 make sure you have read this entire section so you know what to expect.
791 Then, make it clear to yourself how you want to organize your VPN:
792 What are the nodes (computers running tinc)?
793 What IP addresses/subnets do they have?
794 What is the network mask of the entire VPN?
795 Do you need special firewall rules?
796 Do you have to set up masquerading or forwarding rules?
797 These questions can only be answered by yourself,
798 you will not find the answers in this documentation.
799 Make sure you have an adequate understanding of networks in general.
800 A good resource on networking is the
801 @uref{http://www.linuxdoc.org/LDP/nag2/, Linux Network Administrators Guide}.
803 If you have everything clearly pictured in your mind,
804 proceed in the following order:
805 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
806 Then generate the keypairs.
807 Finally, distribute the host configuration files.
808 These steps are described in the subsections below.
811 @c ==================================================================
812 @node Multiple networks, How connections work, Configuration introduction, Configuration
813 @section Multiple networks
815 @cindex multiple networks
817 In order to allow you to run more than one tinc daemon on one computer,
818 for instance if your computer is part of more than one VPN,
819 you can assign a ``netname'' to your VPN.
820 It is not required if you only run one tinc daemon,
821 it doesn't even have to be the same on all the sites of your VPN,
822 but it is recommended that you choose one anyway.
824 We will asume you use a netname throughout this document.
825 This means that you call tincd with the -n argument,
826 which will assign a netname to this daemon.
828 The effect of this is that the daemon will set its configuration
829 ``root'' to /etc/tinc/netname/, where netname is your argument to the -n
830 option. You'll notice that it appears in syslog as ``tinc.netname''.
832 However, it is not strictly necessary that you call tinc with the -n
833 option. In this case, the network name would just be empty, and it will
834 be used as such. tinc now looks for files in /etc/tinc/, instead of
835 /etc/tinc/netname/; the configuration file should be /etc/tinc/tinc.conf,
836 and the host configuration files are now expected to be in /etc/tinc/hosts/.
838 But it is highly recommended that you use this feature of tinc, because
839 it will be so much clearer whom your daemon talks to. Hence, we will
840 assume that you use it.
843 @c ==================================================================
844 @node How connections work, Configuration files, Multiple networks, Configuration
845 @section How connections work
847 When tinc starts up, it parses the command-line options and then
848 reads in the configuration file tinc.conf.
849 If it sees one or more `ConnectTo' values pointing to other tinc daemons in that file,
850 it will try to connect to those other daemons.
851 Whether this succeeds or not and whether `ConnectTo' is specified or not,
852 tinc will listen for incoming connection from other deamons.
853 If you did specify a `ConnectTo' value and the other side is not responding,
854 tinc will keep retrying.
855 This means that once started, tinc will stay running until you tell it to stop,
856 and failures to connect to other tinc daemons will not stop your tinc daemon
857 for trying again later.
858 This means you don't have to intervene if there are temporary network problems.
862 There is no real distinction between a server and a client in tinc.
863 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
864 and one which does specify such a value as a client.
865 It does not matter if two tinc daemons have a `ConnectTo' value pointing to each other however.
868 @c ==================================================================
869 @node Configuration files, Generating keypairs, How connections work, Configuration
870 @section Configuration files
872 The actual configuration of the daemon is done in the file
873 @file{/etc/tinc/netname/tinc.conf} and at least one other file in the directory
874 @file{/etc/tinc/netname/hosts/}.
876 These file consists of comments (lines started with a #) or assignments
883 The variable names are case insensitive, and any spaces, tabs, newlines
884 and carriage returns are ignored. Note: it is not required that you put
885 in the `=' sign, but doing so improves readability. If you leave it
886 out, remember to replace it with at least one space character.
888 In this section all valid variables are listed in alphabetical order.
889 The default value is given between parentheses,
890 other comments are between square brackets and
891 required directives are given in @strong{bold}.
894 * Main configuration variables::
895 * Host configuration variables::
900 @c ==================================================================
901 @node Main configuration variables, Host configuration variables, Configuration files, Configuration files
902 @subsection Main configuration variables
905 @cindex AddressFamily
906 @item AddressFamily = <ipv4|ipv6|any> (any)
907 This option affects the address family of listening and outgoing sockets.
908 If "any" is selected, then depending on the operating system
909 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
911 @cindex BindToAddress
912 @item BindToAddress = <address> [experimental]
913 If your computer has more than one IPv4 or IPv6 address, tinc
914 will by default listen on all of them for incoming connections.
915 It is possible to bind only to a single address with this variable.
917 This option may not work on all platforms.
919 @cindex BindToInterface
920 @item BindToInterface = <interface> [experimental]
921 If you have more than one network interface in your computer, tinc will
922 by default listen on all of them for incoming connections. It is
923 possible to bind tinc to a single interface like eth0 or ppp0 with this
926 This option may not work on all platforms.
929 @item @strong{ConnectTo = <name>}
930 Specifies which other tinc daemon to connect to on startup.
931 Multiple ConnectTo variables may be specified,
932 in which case outgoing connections to each specified tinc daemon are made.
933 The names should be known to this tinc daemon
934 (i.e., there should be a host configuration file for the name on the ConnectTo line).
936 If you don't specify a host with ConnectTo,
937 tinc won't try to connect to other daemons at all,
938 and will instead just listen for incoming connections.
941 @item @strong{Device = <device>} (/dev/tap0 or /dev/net/tun)
942 The virtual network device to use. Note that you can only use one device per
943 daemon. See also @ref{Device files}.
946 @item Hostnames = <yes|no> (no)
947 This option selects whether IP addresses (both real and on the VPN)
948 should be resolved. Since DNS lookups are blocking, it might affect
949 tinc's efficiency, even stopping the daemon for a few seconds everytime
950 it does a lookup if your DNS server is not responding.
952 This does not affect resolving hostnames to IP addresses from the
956 @item Interface = <interface>
957 Defines the name of the interface corresponding to the virtual network device.
958 Depending on the operating system and the type of device this may or may not actually set the name of the interface
959 or choose the device corresponding to this interface.
962 @item Mode = <router|switch|hub> (router)
963 This option selects the way packets are routed to other daemons.
969 variables in the host configuration files will be used to form a routing table.
970 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
972 This is the default mode, and unless you really know you need another mode, don't change it.
976 In this mode the MAC addresses of the packets on the VPN will be used to
977 dynamically create a routing table just like an Ethernet switch does.
978 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
979 at the cost of frequent broadcast ARP requests and routing table updates.
981 This mode is primarily useful if you want to bridge Ethernet segments.
985 This mode is almost the same as the switch mode, but instead
986 every packet will be broadcast to the other daemons
987 while no routing table is managed.
991 @item KeyExpire = <seconds> (3600)
992 This option controls the time the encryption keys used to encrypt the data
993 are valid. It is common practice to change keys at regular intervals to
994 make it even harder for crackers, even though it is thought to be nearly
995 impossible to crack a single key.
998 @item MACExpire = <seconds> (600)
999 This option controls the amount of time MAC addresses are kept before they are removed.
1000 This only has effect when Mode is set to "switch".
1003 @item @strong{Name = <name>}
1004 This is a symbolic name for this connection. It can be anything
1007 @item PingTimeout = <seconds> (60)
1008 The number of seconds of inactivity that tinc will wait before sending a
1009 probe to the other end. If that other end doesn't answer within that
1010 same amount of seconds, the connection is terminated, and the others
1011 will be notified of this.
1013 @cindex PriorityInheritance
1014 @item PriorityInheritance = <yes|no> (no) [experimental]
1015 When this option is enabled the value of the TOS field of tunneled IPv4 packets
1016 will be inherited by the UDP packets that are sent out.
1019 @item PrivateKey = <key> [obsolete]
1020 This is the RSA private key for tinc. However, for safety reasons it is
1021 advised to store private keys of any kind in separate files. This prevents
1022 accidental eavesdropping if you are editting the configuration file.
1024 @cindex PrivateKeyFile
1025 @item @strong{PrivateKeyFile = <path>} [recommended]
1026 This is the full path name of the RSA private key file that was
1027 generated by ``tincd --generate-keys''. It must be a full path, not a
1030 Note that there must be exactly one of PrivateKey
1032 specified in the configuration file.
1037 @c ==================================================================
1038 @node Host configuration variables, How to configure, Main configuration variables, Configuration files
1039 @subsection Host configuration variables
1043 @item @strong{Address = <IP address|hostname>} [recommended]
1044 This variable is only required if you want to connect to this host. It
1045 must resolve to the external IP address where the host can be reached,
1046 not the one that is internal to the VPN.
1049 @item Cipher = <cipher> (blowfish)
1050 The symmetric cipher algorithm used to encrypt UDP packets.
1051 Any cipher supported by OpenSSL is recognized.
1054 @item Compression = <level> (0)
1055 This option sets the level of compression used for UDP packets.
1056 Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
1057 10 (fast lzo) and 11 (best lzo).
1060 @item Digest = <digest> (sha1)
1061 The digest algorithm used to authenticate UDP packets.
1062 Any digest supported by OpenSSL is recognized.
1063 Furthermore, specifying "none" will turn off packet authentication.
1065 @cindex IndirectData
1066 @item IndirectData = <yes|no> (no)
1067 This option specifies whether other tinc daemons besides the one you
1068 specified with ConnectTo can make a direct connection to you. This is
1069 especially useful if you are behind a firewall and it is impossible to
1070 make a connection from the outside to your tinc daemon. Otherwise, it
1071 is best to leave this option out or set it to no.
1074 @item MACLength = <length> (4)
1075 The length of the message authentication code used to authenticate UDP packets.
1076 Can be anything from 0
1077 up to the length of the digest produced by the digest algorithm.
1080 @item Port = <port> (655)
1081 This is the port this tinc daemon listens on.
1082 You can use decimal portnumbers or symbolic names (as listed in /etc/services).
1085 @item PublicKey = <key> [obsolete]
1086 This is the RSA public key for this host.
1088 @cindex PublicKeyFile
1089 @item PublicKeyFile = <path> [obsolete]
1090 This is the full path name of the RSA public key file that was generated
1091 by ``tincd --generate-keys''. It must be a full path, not a relative
1095 From version 1.0pre4 on tinc will store the public key directly into the
1096 host configuration file in PEM format, the above two options then are not
1097 necessary. Either the PEM format is used, or exactly
1098 @strong{one of the above two options} must be specified
1099 in each host configuration file, if you want to be able to establish a
1100 connection with that host.
1103 @item Subnet = <address[/prefixlength]>
1104 The subnet which this tinc daemon will serve.
1105 tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
1106 If the packet matches a subnet,
1107 it will be sent to the daemon who has this subnet in his host configuration file.
1108 Multiple subnet lines can be specified for each daemon.
1110 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1111 in which case a subnet consisting of only that single address is assumed,
1112 or they can be a IPv4 or IPv6 network address with a prefixlength.
1113 Shorthand notations are not supported.
1114 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1115 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1116 Note that subnets like 192.168.1.1/24 are invalid!
1117 Read a networking HOWTO/FAQ/guide if you don't understand this.
1118 IPv6 subnets are notated like fec0:0:0:1:0:0:0:0/64.
1119 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1121 @cindex CIDR notation
1122 prefixlength is the number of bits set to 1 in the netmask part; for
1123 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1124 /22. This conforms to standard CIDR notation as described in
1125 @uref{ftp://ftp.isi.edu/in-notes/rfc1519.txt, RFC1519}
1128 @item TCPonly = <yes|no> (no) [experimental]
1129 If this variable is set to yes, then the packets are tunnelled over a
1130 TCP connection instead of a UDP connection. This is especially useful
1131 for those who want to run a tinc daemon from behind a masquerading
1132 firewall, or if UDP packet routing is disabled somehow.
1133 Setting this options also implicitly sets IndirectData.
1137 @c ==================================================================
1138 @node How to configure, , Host configuration variables, Configuration files
1139 @subsection How to configure
1141 @subsubheading Step 1. Creating the main configuration file
1143 The main configuration file will be called @file{/etc/tinc/netname/tinc.conf}.
1144 Adapt the following example to create a basic configuration file:
1147 Name = @emph{yourname}
1148 Device = @emph{/dev/tap0}
1149 PrivateKeyFile = /etc/tinc/@emph{netname}/rsa_key.priv
1152 Then, if you know to which other tinc daemon(s) yours is going to connect,
1153 add `ConnectTo' values.
1155 @subsubheading Step 2. Creating your host configuration file
1157 If you added a line containing `Name = yourname' in the main configuarion file,
1158 you will need to create a host configuration file @file{/etc/tinc/netname/hosts/yourname}.
1159 Adapt the following example to create a host configuration file:
1162 Address = @emph{your.real.hostname.org}
1163 Subnet = @emph{192.168.1.0/24}
1166 You can also use an IP address instead of a hostname.
1167 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1168 If you have multiple address ranges you can specify more than one `Subnet'.
1169 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).
1172 @c ==================================================================
1173 @node Generating keypairs, Network interfaces, Configuration files, Configuration
1174 @section Generating keypairs
1176 @cindex key generation
1177 Now that you have already created the main configuration file and your host configuration file,
1178 you can easily create a public/private keypair by entering the following command:
1181 tincd -n @emph{netname} -K
1184 tinc will generate a public and a private key and ask you where to put them.
1185 Just press enter to accept the defaults.
1188 @c ==================================================================
1189 @node Network interfaces, Example configuration, Generating keypairs, Configuration
1190 @section Network interfaces
1192 Before tinc can start transmitting data over the tunnel, it must
1193 set up the virtual network interface.
1195 First, decide which IP addresses you want to have associated with these
1196 devices, and what network mask they must have.
1198 tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1199 which will also create a network interface called something like `tun0', `tap0', or,
1200 if you are using the Linux tun/tap driver, the network interface will by default have the same name as the netname.
1203 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1204 to a script named @file{/etc/tinc/netname/tinc-up}. When tinc starts, this script
1205 will be executed. When tinc exits, it will execute the script named
1206 @file{/etc/tinc/netname/tinc-down}, but normally you don't need to create that script.
1208 An example @file{tinc-up} script:
1212 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1215 This script gives the interface an IP address and a netmask.
1216 The kernel will also automatically add a route to this interface, so normally you don't need
1217 to add route commands to the @file{tinc-up} script.
1218 The kernel will also bring the interface up after this command.
1220 The netmask is the mask of the @emph{entire} VPN network, not just your
1224 @c ==================================================================
1225 @node Example configuration, , Network interfaces, Configuration
1226 @section Example configuration
1230 Imagine the following situation. Branch A of our example `company' wants to connect
1231 three branch offices in B, C and D using the Internet. All four offices
1232 have a 24/7 connection to the Internet.
1234 A is going to serve as the center of the network. B and C will connect
1235 to A, and D will connect to C. Each office will be assigned their own IP
1239 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1240 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1241 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1242 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1245 ``gateway'' is the VPN IP address of the machine that is running the
1246 tincd. ``internet IP'' is the IP address of the firewall, which does not
1247 need to run tincd, but it must do a port forwarding of TCP&UDP on port
1248 655 (unless otherwise configured).
1250 In this example, it is assumed that eth0 is the interface that points to
1251 the inner (physical) LAN of the office, although this could also be the
1252 same as the interface that leads to the Internet. The configuration of
1253 the real interface is also shown as a comment, to give you an idea of
1254 how these example host is set up. All branches use the netname `company'
1255 for this particular VPN.
1257 @subsubheading For Branch A
1259 @emph{BranchA} would be configured like this:
1261 In @file{/etc/tinc/company/tinc-up}:
1264 # Real interface of internal network:
1265 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0 broadcast 10.1.255.255
1267 ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
1270 and in @file{/etc/tinc/company/tinc.conf}:
1274 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1278 On all hosts, /etc/tinc/company/hosts/BranchA contains:
1281 Subnet = 10.1.0.0/16
1284 -----BEGIN RSA PUBLIC KEY-----
1286 -----END RSA PUBLIC KEY-----
1289 Note that the IP addresses of eth0 and tap0 are the same.
1290 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1291 It is in fact recommended to give give both real internal network interfaces and tap interfaces the same IP address,
1292 since that will make things a lot easier to remember and set up.
1295 @subsubheading For Branch B
1297 In @file{/etc/tinc/company/tinc-up}:
1300 # Real interface of internal network:
1301 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0 broadcast 10.2.255.255
1303 ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
1306 and in @file{/etc/tinc/company/tinc.conf}:
1311 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1314 Note here that the internal address (on eth0) doesn't have to be the
1315 same as on the tap0 device. Also, ConnectTo is given so that no-one can
1316 connect to this node.
1318 On all hosts, in @file{/etc/tinc/company/hosts/BranchB}:
1321 Subnet = 10.2.0.0/16
1324 -----BEGIN RSA PUBLIC KEY-----
1326 -----END RSA PUBLIC KEY-----
1330 @subsubheading For Branch C
1332 In @file{/etc/tinc/company/tinc-up}:
1335 # Real interface of internal network:
1336 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0 broadcast 10.3.255.255
1338 ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
1341 and in @file{/etc/tinc/company/tinc.conf}:
1349 C already has another daemon that runs on port 655, so they have to
1350 reserve another port for tinc. It knows the portnumber it has to listen on
1351 from it's own host configuration file.
1353 On all hosts, in @file{/etc/tinc/company/hosts/BranchC}:
1357 Subnet = 10.3.0.0/16
1360 -----BEGIN RSA PUBLIC KEY-----
1362 -----END RSA PUBLIC KEY-----
1366 @subsubheading For Branch D
1368 In @file{/etc/tinc/company/tinc-up}:
1371 # Real interface of internal network:
1372 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0 broadcast 10.4.255.255
1374 ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
1377 and in @file{/etc/tinc/company/tinc.conf}:
1382 Device = /dev/net/tun
1383 PrivateKeyFile = /etc/tinc/company/rsa_key.priv
1386 D will be connecting to C, which has a tincd running for this network on
1387 port 2000. It knows the port number from the host configuration file.
1388 Also note that since D uses the tun/tap driver, the network interface
1389 will not be called `tun' or `tap0' or something like that, but will
1390 have the same name as netname.
1392 On all hosts, in @file{/etc/tinc/company/hosts/BranchD}:
1395 Subnet = 10.4.0.0/16
1398 -----BEGIN RSA PUBLIC KEY-----
1400 -----END RSA PUBLIC KEY-----
1403 @subsubheading Key files
1405 A, B, C and D all have generated a public/private keypair with the following command:
1411 The private key is stored in @file{/etc/tinc/company/rsa_key.priv},
1412 the public key is put into the host configuration file in the @file{/etc/tinc/company/hosts/} directory.
1413 During key generation, tinc automatically guesses the right filenames based on the -n option and
1414 the Name directive in the @file{tinc.conf} file (if it is available).
1416 @subsubheading Starting
1418 After each branch has finished configuration and they have distributed
1419 the host configuration files amongst them, they can start their tinc daemons.
1420 They don't necessarily have to wait for the other branches to have started
1421 their daemons, tinc will try connecting until they are available.
1424 @c ==================================================================
1425 @node Running tinc, Technical information, Configuration, Top
1426 @chapter Running tinc
1428 If everything else is done, you can start tinc by typing the following command:
1431 tincd -n @emph{netname}
1435 tinc will detach from the terminal and continue to run in the background like a good daemon.
1436 If there are any problems however you can try to increase the debug level
1437 and look in the syslog to find out what the problems are.
1445 @c ==================================================================
1446 @node Runtime options, Error messages, , Running tinc
1447 @section Runtime options
1449 Besides the settings in the configuration file, tinc also accepts some
1450 command line options.
1452 @cindex command line
1453 @cindex runtime options
1457 @item -c, --config=PATH
1458 Read configuration options from the directory PATH. The default is
1459 @file{/etc/tinc/netname/}.
1461 @item -D, --no-detach
1462 Don't fork and detach.
1463 This will also disable the automatic restart mechanism for fatal errors.
1466 @item -d, --debug=LEVEL
1467 Set debug level to LEVEL. The higher the debug level, the more gets
1468 logged. Everything goes via syslog.
1470 @item -k, --kill[=SIGNAL]
1471 Attempt to kill a running tincd (optionally with the specified SIGNAL instead of SIGTERM) and exit.
1472 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1474 @item -n, --net=NETNAME
1475 Connect to net NETNAME. @xref{Multiple networks}.
1477 @item -K, --generate-keys[=BITS]
1478 Generate public/private keypair of BITS length. If BITS is not specified,
1479 1024 is the default. tinc will ask where you want to store the files,
1480 but will default to the configuration directory (you can use the -c or -n option
1481 in combination with -K). After that, tinc will quit.
1484 Lock tinc into main memory.
1485 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1487 @item --logfile[=FILE]
1488 Write log entries to a file instead of to the system logging facility.
1489 If FILE is omitted, the default is /var/log/tinc.NETNAME.log.
1491 @item --pidfile=FILE
1492 Write PID to FILE instead of /var/run/tinc.NETNAME.pid.
1494 @item --bypass-security
1495 Disables encryption and authentication.
1496 Only useful for debugging.
1499 Display a short reminder of these runtime options and terminate.
1502 Output version information and exit.
1507 @c ==================================================================
1508 @node Error messages, , Runtime options, Running tinc
1509 @section Error messages
1511 What follows is a list of the most common error messages you can see
1512 when configuring tinc. Most of these messages are visible in the syslog
1513 only, so keep an eye on it!
1516 @item Could not open /dev/tap0: No such device
1519 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1520 @item You forgot to compile `Netlink device emulation' in the kernel.
1523 @item Can't write to /dev/net/tun: No such device
1526 @item You forgot to `modprobe tun'.
1527 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1530 @item Packet with destination 1.2.3.4 is looping back to us!
1533 @item Something is not configured right. Packets are being sent out to the
1534 virtual network device, but according to the Subnet directives in your host configuration
1535 file, those packets should go to your own host. Most common mistake is that
1536 you have a Subnet line in your host configuration file with a prefix length which is
1537 just as large as the prefix of the virtual network interface. The latter should in almost all
1538 cases be larger. Rethink your configuration.
1539 Note that you will only see this message if you specified a debug
1540 level of 5 or higher!
1541 @item Chances are that a `Subnet = ...' line in the host configuration file of this tinc daemon is wrong.
1542 Change it to a subnet that is accepted locally by another interface,
1543 or if that is not the case, try changing the prefix length into /32.
1546 @item Network doesn't work, syslog shows only packets of length 46
1548 @item Network address and prefix length do not match!
1551 @item The Subnet field must contain a @emph{network} address.
1552 @item If you only want to use one IP address, set the netmask to /32.
1555 @item This is a bug: net.c:253: 24: Some error
1558 @item This is something that should not have happened.
1559 Please report this, and tell us exactly what went wrong before you got
1560 this message. In normal operation, these errors should not occur.
1563 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1566 @item You must specify the complete pathname.
1567 Specifying a relative path does not make sense here. tinc changes its
1568 directory to / when starting (to avoid keeping a mount point busy).
1573 @c ==================================================================
1574 @node Technical information, About us, Running tinc, Top
1575 @chapter Technical information
1580 * The meta-protocol::
1585 @c ==================================================================
1586 @node The connection, The meta-protocol, Technical information, Technical information
1587 @section The connection
1590 tinc is a daemon that takes VPN data and transmit that to another host
1591 computer over the existing Internet infrastructure.
1595 * The meta-connection::
1599 @c ==================================================================
1600 @node The UDP tunnel, The meta-connection, The connection, The connection
1601 @subsection The UDP tunnel
1603 @cindex virtual network device
1605 The data itself is read from a character device file, the so-called
1606 @emph{virtual network device}. This device is associated with a network
1607 interface. Any data sent to this interface can be read from the device,
1608 and any data written to the device gets sent from the interface.
1609 There are two possible types of virtual network devices:
1610 `tun' style, which are point-to-point devices which can only handle IPv4 and/or IPv6 packets,
1611 and `tap' style, which are Ethernet devices and handle complete Ethernet frames.
1613 So when tinc reads an Ethernet frame from the device, it determines its
1614 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
1615 packets. Depending on the Subnet lines, it will send the packets off to their destination IP address.
1616 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
1617 to deduce the destination of the packets.
1618 Since the latter modes only depend on the link layer information,
1619 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
1620 However, only `tap' style devices provide this information.
1622 After the destination has been determined,
1623 the packet will be compressed (optionally),
1624 a sequence number will be added to the packet,
1625 the packet will then be encrypted
1626 and a message authentication code will be appended.
1628 @cindex encapsulating
1630 When that is done, time has come to actually transport the
1631 packet to the destination computer. We do this by sending the packet
1632 over an UDP connection to the destination host. This is called
1633 @emph{encapsulating}, the VPN packet (though now encrypted) is
1634 encapsulated in another IP datagram.
1636 When the destination receives this packet, the same thing happens, only
1637 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
1638 checks the sequence number
1639 and writes the decrypted information to its own virtual network device.
1641 If the virtual network device is a `tun' device (a point-to-point tunnel),
1642 there is no problem for the kernel to accept a packet.
1643 However, if it is a `tap' device (this is the only available type on FreeBSD),
1644 the destination MAC address must match that of the virtual network interface.
1645 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC
1646 can not be known by the sending host.
1647 tinc solves this by letting the receiving end detect the MAC address of its own virtual network interface
1648 and overwriting the destination MAC address of the received packet.
1650 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
1651 In those modes every interface should have a unique MAC address, so make sure they are not the same.
1652 Because switch and hub modes rely on MAC addresses to function correctly,
1653 these modes cannot be used on the following operating systems which don't have a `tap' style virtual network device:
1654 OpenBSD, NetBSD, Darwin and Solaris.
1657 @c ==================================================================
1658 @node The meta-connection, , The UDP tunnel, The connection
1659 @subsection The meta-connection
1661 Having only a UDP connection available is not enough. Though suitable
1662 for transmitting data, we want to be able to reliably send other
1663 information, such as routing and session key information to somebody.
1666 TCP is a better alternative, because it already contains protection
1667 against information being lost, unlike UDP.
1669 So we establish two connections. One for the encrypted VPN data, and one
1670 for other information, the meta-data. Hence, we call the second
1671 connection the meta-connection. We can now be sure that the
1672 meta-information doesn't get lost on the way to another computer.
1674 @cindex data-protocol
1675 @cindex meta-protocol
1676 Like with any communication, we must have a protocol, so that everybody
1677 knows what everything stands for, and how she should react. Because we
1678 have two connections, we also have two protocols. The protocol used for
1679 the UDP data is the ``data-protocol,'' the other one is the
1682 The reason we don't use TCP for both protocols is that UDP is much
1683 better for encapsulation, even while it is less reliable. The real
1684 problem is that when TCP would be used to encapsulate a TCP stream
1685 that's on the private network, for every packet sent there would be
1686 three ACKs sent instead of just one. Furthermore, if there would be
1687 a timeout, both TCP streams would sense the timeout, and both would
1688 start re-sending packets.
1691 @c ==================================================================
1692 @node The meta-protocol, Security, The connection, Technical information
1693 @section The meta-protocol
1695 The meta protocol is used to tie all tinc daemons together, and
1696 exchange information about which tinc daemon serves which virtual
1699 The meta protocol consists of requests that can be sent to the other
1700 side. Each request has a unique number and several parameters. All
1701 requests are represented in the standard ASCII character set. It is
1702 possible to use tools such as telnet or netcat to connect to a tinc
1703 daemon started with the --bypass-security option
1704 and to read and write requests by hand, provided that one
1705 understands the numeric codes sent.
1707 The authentication scheme is described in @ref{Authentication protocol}. After a
1708 successful authentication, the server and the client will exchange all the
1709 information about other tinc daemons and subnets they know of, so that both
1710 sides (and all the other tinc daemons behind them) have their information
1717 --------------------------------------------------------------------------
1718 origin ADD_EDGE node1 node2 21.32.43.54 655 222 0
1719 | | | | | +-> options
1720 | | | | +----> weight
1721 | | | +--------> UDP port of node2
1722 | | +----------------> real address of node2
1723 | +-------------------------> name of destination node
1724 +-------------------------------> name of source node
1726 origin ADD_SUBNET node 192.168.1.0/24
1727 | | +--> prefixlength
1728 | +--------> network address
1729 +------------------> owner of this subnet
1730 --------------------------------------------------------------------------
1733 The ADD_EDGE messages are to inform other tinc daemons that a connection between
1734 two nodes exist. The address of the destination node is available so that
1735 VPN packets can be sent directly to that node.
1737 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
1738 to certain nodes. tinc will use it to determine to which node a VPN packet has
1745 ------------------------------------------------------------------
1746 DEL_EDGE node1 node2
1747 | +----> name of destination node
1748 +----------> name of source node
1750 DEL_SUBNET node 192.168.1.0/24
1751 | | +--> prefixlength
1752 | +--------> network address
1753 +------------------> owner of this subnet
1754 ------------------------------------------------------------------
1757 In case a connection between two daemons is closed or broken, DEL_EDGE messages
1758 are sent to inform the other daemons of that fact. Each daemon will calculate a
1759 new route to the the daemons, or mark them unreachable if there isn't any.
1766 ------------------------------------------------------------------
1767 REQ_KEY origin destination
1768 | +--> name of the tinc daemon it wants the key from
1769 +----------> name of the daemon that wants the key
1771 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
1772 | | \______________/ | | +--> MAC length
1773 | | | | +-----> digest algorithm
1774 | | | +--------> cipher algorithm
1775 | | +--> 128 bits key
1776 | +--> name of the daemon that wants the key
1777 +----------> name of the daemon that uses this key
1780 +--> daemon that has changed it's packet key
1781 --------------------------------------------------------------------------
1784 The keys used to encrypt VPN packets are not sent out directly. This is
1785 because it would generate a lot of traffic on VPNs with many daemons, and
1786 chances are that not every tinc daemon will ever send a packet to every
1787 other daemon. Instead, if a daemon needs a key it sends a request for it
1788 via the meta connection of the nearest hop in the direction of the
1795 --------------------------------------------------------------------------
1798 --------------------------------------------------------------------------
1801 There is also a mechanism to check if hosts are still alive. Since network
1802 failures or a crash can cause a daemon to be killed without properly
1803 shutting down the TCP connection, this is necessary to keep an up to date
1804 connection list. PINGs are sent at regular intervals, except when there
1805 is also some other traffic. A little bit of salt (random data) is added
1806 with each PING and PONG message, to make sure that long sequences of PING/PONG
1807 messages without any other traffic won't result in known plaintext.
1809 This basically covers what is sent over the meta connection by
1813 @c ==================================================================
1814 @node Security, , The meta-protocol, Technical information
1815 @section About tinc's encryption and other security-related issues.
1819 tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
1820 alleged Cabal was/is an organisation that was said to keep an eye on the
1821 entire Internet. As this is exactly what you @emph{don't} want, we named
1822 the tinc project after TINC.
1825 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
1826 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
1827 exactly that: encrypt.
1828 tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
1829 sequence numbers and 4 byte long message authentication codes to make sure
1830 eavesdroppers cannot get and cannot change any information at all from the
1831 packets they can intercept. The encryption algorithm and message authentication
1832 algorithm can be changed in the configuration. The length of the message
1833 authentication codes is also adjustable. The length of the key for the
1834 encryption algorithm is always the default length used by OpenSSL.
1837 * Authentication protocol::
1838 * Encryption of network packets::
1842 @c ==================================================================
1843 @node Authentication protocol, Encryption of network packets, Security, Security
1844 @subsection Authentication protocol
1846 @cindex authentication
1847 A new scheme for authentication in tinc has been devised, which offers some
1848 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
1858 --------------------------------------------------------------------------
1859 client <attempts connection>
1861 server <accepts connection>
1865 +-------> name of tinc daemon
1869 +-------> name of tinc daemon
1871 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
1872 \_________________________________/
1873 +-> RSAKEYLEN bits totally random string S1,
1874 encrypted with server's public RSA key
1876 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
1877 \_________________________________/
1878 +-> RSAKEYLEN bits totally random string S2,
1879 encrypted with client's public RSA key
1882 - the client will symmetrically encrypt outgoing traffic using S1
1883 - the server will symmetrically encrypt outgoing traffic using S2
1885 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
1886 \_________________________________/
1887 +-> CHALLEN bits totally random string H1
1889 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
1890 \_________________________________/
1891 +-> CHALLEN bits totally random string H2
1893 client CHAL_REPLY 816a86
1894 +-> 160 bits SHA1 of H2
1896 server CHAL_REPLY 928ffe
1897 +-> 160 bits SHA1 of H1
1899 After the correct challenge replies are received, both ends have proved
1900 their identity. Further information is exchanged.
1902 client ACK 655 123 0
1904 | +----> estimated weight
1905 +--------> listening port of client
1907 server ACK 655 321 0
1909 | +----> estimated weight
1910 +--------> listening port of server
1911 --------------------------------------------------------------------------
1914 This new scheme has several improvements, both in efficiency and security.
1916 First of all, the server sends exactly the same kind of messages over the wire
1917 as the client. The previous versions of tinc first authenticated the client,
1918 and then the server. This scheme even allows both sides to send their messages
1919 simultaneously, there is no need to wait for the other to send something first.
1920 This means that any calculations that need to be done upon sending or receiving
1921 a message can also be done in parallel. This is especially important when doing
1922 RSA encryption/decryption. Given that these calculations are the main part of
1923 the CPU time spent for the authentication, speed is improved by a factor 2.
1925 Second, only one RSA encrypted message is sent instead of two. This reduces the
1926 amount of information attackers can see (and thus use for a cryptographic
1927 attack). It also improves speed by a factor two, making the total speedup a
1930 Third, and most important:
1931 The symmetric cipher keys are exchanged first, the challenge is done
1932 afterwards. In the previous authentication scheme, because a man-in-the-middle
1933 could pass the challenge/chal_reply phase (by just copying the messages between
1934 the two real tinc daemons), but no information was exchanged that was really
1935 needed to read the rest of the messages, the challenge/chal_reply phase was of
1936 no real use. The man-in-the-middle was only stopped by the fact that only after
1937 the ACK messages were encrypted with the symmetric cipher. Potentially, it
1938 could even send it's own symmetric key to the server (if it knew the server's
1939 public key) and read some of the metadata the server would send it (it was
1940 impossible for the mitm to read actual network packets though). The new scheme
1941 however prevents this.
1943 This new scheme makes sure that first of all, symmetric keys are exchanged. The
1944 rest of the messages are then encrypted with the symmetric cipher. Then, each
1945 side can only read received messages if they have their private key. The
1946 challenge is there to let the other side know that the private key is really
1947 known, because a challenge reply can only be sent back if the challenge is
1948 decrypted correctly, and that can only be done with knowledge of the private
1951 Fourth: the first thing that is send via the symmetric cipher encrypted
1952 connection is a totally random string, so that there is no known plaintext (for
1953 an attacker) in the beginning of the encrypted stream.
1956 @c ==================================================================
1957 @node Encryption of network packets, , Authentication protocol, Security
1958 @subsection Encryption of network packet
1961 A data packet can only be sent if the encryption key is known to both
1962 parties, and the connection is activated. If the encryption key is not
1963 known, a request is sent to the destination using the meta connection
1964 to retrieve it. The packet is stored in a queue while waiting for the
1968 The UDP packet containing the network packet from the VPN has the following layout:
1971 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
1972 \___________________/\_____/
1974 V +---> digest algorithm
1975 Encrypted with symmetric cipher
1978 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
1979 sequence number that is added in front of the actual VPN packet, to act as a unique
1980 IV for each packet and to prevent replay attacks. A message authentication code
1981 is added to the UDP packet to prevent alteration of packets. By default the
1982 first 4 bytes of the digest are used for this, but this can be changed using
1983 the MACLength configuration variable.
1985 @c ==================================================================
1986 @node About us, Concept Index, Technical information, Top
1991 * Contact Information::
1996 @c ==================================================================
1997 @node Contact Information, Authors, About us, About us
1998 @section Contact information
2001 tinc's website is at @url{http://tinc.nl.linux.org/},
2002 this server is located in the Netherlands.
2005 We have an IRC channel on the FreeNode and OFTC IRC networks. Connect to
2006 @uref{http://www.freenode.net/, irc.freenode.net}
2008 @uref{http://www.oftc.net/, irc.oftc.net}
2009 and join channel #tinc.
2012 @c ==================================================================
2013 @node Authors, , Contact Information, About us
2017 @item Ivo Timmermans (zarq) (@email{ivo@@o2w.nl})
2018 @item Guus Sliepen (guus) (@email{guus@@sliepen.eu.org})
2021 We have received a lot of valuable input from users. With their help,
2022 tinc has become the flexible and robust tool that it is today. We have
2023 composed a list of contributions, in the file called @file{THANKS} in
2024 the source distribution.
2027 @c ==================================================================
2028 @node Concept Index, , About us, Top
2029 @c node-name, next, previous, up
2030 @unnumbered Concept Index
2032 @c ==================================================================
2036 @c ==================================================================