1 \input texinfo @c -*-texinfo-*-
8 @include tincinclude.texi
11 @dircategory Networking tools
13 * tinc: (tinc). The tinc Manual.
16 This is the info manual for @value{PACKAGE} version @value{VERSION}, a Virtual Private Network daemon.
18 Copyright @copyright{} 1998-2016 Ivo Timmermans,
19 Guus Sliepen <guus@@tinc-vpn.org> and
20 Wessel Dankers <wsl@@tinc-vpn.org>.
22 Permission is granted to make and distribute verbatim copies of this
23 manual provided the copyright notice and this permission notice are
24 preserved on all copies.
26 Permission is granted to copy and distribute modified versions of this
27 manual under the conditions for verbatim copying, provided that the
28 entire resulting derived work is distributed under the terms of a
29 permission notice identical to this one.
35 @subtitle Setting up a Virtual Private Network with tinc
36 @author Ivo Timmermans and Guus Sliepen
39 @vskip 0pt plus 1filll
40 This is the info manual for @value{PACKAGE} version @value{VERSION}, a Virtual Private Network daemon.
42 Copyright @copyright{} 1998-2016 Ivo Timmermans,
43 Guus Sliepen <guus@@tinc-vpn.org> and
44 Wessel Dankers <wsl@@tinc-vpn.org>.
46 Permission is granted to make and distribute verbatim copies of this
47 manual provided the copyright notice and this permission notice are
48 preserved on all copies.
50 Permission is granted to copy and distribute modified versions of this
51 manual under the conditions for verbatim copying, provided that the
52 entire resulting derived work is distributed under the terms of a
53 permission notice identical to this one.
58 @c ==================================================================
68 * Technical information::
69 * Platform specific information::
71 * Concept Index:: All used terms explained
75 @c ==================================================================
80 Tinc is a Virtual Private Network (VPN) daemon that uses tunneling and
81 encryption to create a secure private network between hosts on the
84 Because the tunnel appears to the IP level network code as a normal
85 network device, there is no need to adapt any existing software.
86 The encrypted tunnels allows VPN sites to share information with each other
87 over the Internet without exposing any information to others.
89 This document is the manual for tinc. Included are chapters on how to
90 configure your computer to use tinc, as well as the configuration
91 process of tinc itself.
94 * Virtual Private Networks::
96 * Supported platforms::
99 @c ==================================================================
100 @node Virtual Private Networks
101 @section Virtual Private Networks
104 A Virtual Private Network or VPN is a network that can only be accessed
105 by a few elected computers that participate. This goal is achievable in
106 more than just one way.
109 Private networks can consist of a single stand-alone Ethernet LAN. Or
110 even two computers hooked up using a null-modem cable. In these cases,
112 obvious that the network is @emph{private}, no one can access it from the
113 outside. But if your computers are linked to the Internet, the network
114 is not private anymore, unless one uses firewalls to block all private
115 traffic. But then, there is no way to send private data to trusted
116 computers on the other end of the Internet.
119 This problem can be solved by using @emph{virtual} networks. Virtual
120 networks can live on top of other networks, but they use encapsulation to
121 keep using their private address space so they do not interfere with
122 the Internet. Mostly, virtual networks appear like a single LAN, even though
123 they can span the entire world. But virtual networks can't be secured
124 by using firewalls, because the traffic that flows through it has to go
125 through the Internet, where other people can look at it.
127 As is the case with either type of VPN, anybody could eavesdrop. Or
128 worse, alter data. Hence it's probably advisable to encrypt the data
129 that flows over the network.
131 When one introduces encryption, we can form a true VPN. Other people may
132 see encrypted traffic, but if they don't know how to decipher it (they
133 need to know the key for that), they cannot read the information that flows
134 through the VPN. This is what tinc was made for.
137 @c ==================================================================
142 I really don't quite remember what got us started, but it must have been
143 Guus' idea. He wrote a simple implementation (about 50 lines of C) that
144 used the ethertap device that Linux knows of since somewhere
145 about kernel 2.1.60. It didn't work immediately and he improved it a
146 bit. At this stage, the project was still simply called "vpnd".
148 Since then, a lot has changed---to say the least.
151 Tinc now supports encryption, it consists of a single daemon (tincd) for
152 both the receiving and sending end, it has become largely
153 runtime-configurable---in short, it has become a full-fledged
154 professional package.
156 @cindex traditional VPNs
158 Tinc also allows more than two sites to connect to eachother and form a single VPN.
159 Traditionally VPNs are created by making tunnels, which only have two endpoints.
160 Larger VPNs with more sites are created by adding more tunnels.
161 Tinc takes another approach: only endpoints are specified,
162 the software itself will take care of creating the tunnels.
163 This allows for easier configuration and improved scalability.
165 A lot can---and will be---changed. We have a number of things that we would like to
166 see in the future releases of tinc. Not everything will be available in
167 the near future. Our first objective is to make tinc work perfectly as
168 it stands, and then add more advanced features.
170 Meanwhile, we're always open-minded towards new ideas. And we're
174 @c ==================================================================
175 @node Supported platforms
176 @section Supported platforms
179 Tinc has been verified to work under Linux, FreeBSD, OpenBSD, NetBSD, Mac OS X (Darwin), Solaris, and Windows (both natively and in a Cygwin environment),
180 with various hardware architectures. These are some of the platforms
181 that are supported by the universal tun/tap device driver or other virtual network device drivers.
182 Without such a driver, tinc will most
183 likely compile and run, but it will not be able to send or receive data
187 For an up to date list of supported platforms, please check the list on
189 @uref{http://www.tinc-vpn.org/platforms/}.
197 @c Preparing your system
204 @c ==================================================================
206 @chapter Preparations
208 This chapter contains information on how to prepare your system to
212 * Configuring the kernel::
217 @c ==================================================================
218 @node Configuring the kernel
219 @section Configuring the kernel
222 * Configuration of Linux kernels::
223 * Configuration of FreeBSD kernels::
224 * Configuration of OpenBSD kernels::
225 * Configuration of NetBSD kernels::
226 * Configuration of Solaris kernels::
227 * Configuration of Darwin (Mac OS X) kernels::
228 * Configuration of Windows::
232 @c ==================================================================
233 @node Configuration of Linux kernels
234 @subsection Configuration of Linux kernels
236 @cindex Universal tun/tap
237 For tinc to work, you need a kernel that supports the Universal tun/tap device.
238 Most distributions come with kernels that already support this.
239 Here are the options you have to turn on when configuring a new kernel:
242 Code maturity level options
243 [*] Prompt for development and/or incomplete code/drivers
244 Network device support
245 <M> Universal tun/tap device driver support
248 It's not necessary to compile this driver as a module, even if you are going to
249 run more than one instance of tinc.
251 If you decide to build the tun/tap driver as a kernel module, add these lines
252 to @file{/etc/modules.conf}:
255 alias char-major-10-200 tun
259 @c ==================================================================
260 @node Configuration of FreeBSD kernels
261 @subsection Configuration of FreeBSD kernels
263 For FreeBSD version 4.1 and higher, tun and tap drivers are included in the default kernel configuration.
264 The tap driver can be loaded with @code{kldload if_tap}, or by adding @code{if_tap_load="YES"} to @file{/boot/loader.conf}.
267 @c ==================================================================
268 @node Configuration of OpenBSD kernels
269 @subsection Configuration of OpenBSD kernels
271 For OpenBSD version 2.9 and higher,
272 the tun driver is included in the default kernel configuration.
273 There is also a kernel patch from @uref{http://diehard.n-r-g.com/stuff/openbsd/}
274 which adds a tap device to OpenBSD which should work with tinc,
275 but with recent versions of OpenBSD,
276 a tun device can act as a tap device by setting the link0 option with ifconfig.
279 @c ==================================================================
280 @node Configuration of NetBSD kernels
281 @subsection Configuration of NetBSD kernels
283 For NetBSD version 1.5.2 and higher,
284 the tun driver is included in the default kernel configuration.
286 Tunneling IPv6 may not work on NetBSD's tun device.
289 @c ==================================================================
290 @node Configuration of Solaris kernels
291 @subsection Configuration of Solaris kernels
293 For Solaris 8 (SunOS 5.8) and higher,
294 the tun driver may or may not be included in the default kernel configuration.
295 If it isn't, the source can be downloaded from @uref{http://vtun.sourceforge.net/tun/}.
296 For x86 and sparc64 architectures, precompiled versions can be found at @uref{http://www.monkey.org/~dugsong/fragroute/}.
297 If the @file{net/if_tun.h} header file is missing, install it from the source package.
300 @c ==================================================================
301 @node Configuration of Darwin (Mac OS X) kernels
302 @subsection Configuration of Darwin (Mac OS X) kernels
304 Tinc on Darwin relies on a tunnel driver for its data acquisition from the kernel.
305 OS X version 10.6.8 and later have a built-in tun driver called "utun".
306 Tinc also supports the driver from @uref{http://tuntaposx.sourceforge.net/},
307 which supports both tun and tap style devices.
309 By default, tinc expects the tuntaposx driver to be installed.
310 To use the utun driver, set add @code{Device = utunX} to @file{tinc.conf},
311 where X is the desired number for the utun interface.
312 You can also omit the number, in which case the first free number will be chosen.
315 @c ==================================================================
316 @node Configuration of Windows
317 @subsection Configuration of Windows
319 You will need to install the latest TAP-Win32 driver from OpenVPN.
320 You can download it from @uref{http://openvpn.sourceforge.net}.
321 Using the Network Connections control panel,
322 configure the TAP-Win32 network interface in the same way as you would do from the tinc-up script,
323 as explained in the rest of the documentation.
326 @c ==================================================================
332 Before you can configure or build tinc, you need to have the OpenSSL,
333 zlib and lzo libraries installed on your system. If you try to configure tinc without
334 having them installed, configure will give you an error message, and stop.
343 @c ==================================================================
348 For all cryptography-related functions, tinc uses the functions provided
349 by the OpenSSL library.
351 If this library is not installed, you will get an error when configuring
352 tinc for build. Support for running tinc with other cryptographic libraries
353 installed @emph{may} be added in the future.
355 You can use your operating system's package manager to install this if
356 available. Make sure you install the development AND runtime versions
359 If you have to install OpenSSL manually, you can get the source code
360 from @url{http://www.openssl.org/}. Instructions on how to configure,
361 build and install this package are included within the package. Please
362 make sure you build development and runtime libraries (which is the
365 If you installed the OpenSSL libraries from source, it may be necessary
366 to let configure know where they are, by passing configure one of the
367 --with-openssl-* parameters.
370 --with-openssl=DIR OpenSSL library and headers prefix
371 --with-openssl-include=DIR OpenSSL headers directory
372 (Default is OPENSSL_DIR/include)
373 --with-openssl-lib=DIR OpenSSL library directory
374 (Default is OPENSSL_DIR/lib)
378 @subsubheading License
381 The complete source code of tinc is covered by the GNU GPL version 2.
382 Since the license under which OpenSSL is distributed is not directly
383 compatible with the terms of the GNU GPL
384 @uref{http://www.openssl.org/support/faq.html#LEGAL2}, we
385 include an exemption to the GPL (see also the file COPYING.README) to allow
386 everyone to create a statically or dynamically linked executable:
389 This program is released under the GPL with the additional exemption
390 that compiling, linking, and/or using OpenSSL is allowed. You may
391 provide binary packages linked to the OpenSSL libraries, provided that
392 all other requirements of the GPL are met.
395 Since the LZO library used by tinc is also covered by the GPL,
396 we also present the following exemption:
399 Hereby I grant a special exception to the tinc VPN project
400 (http://www.tinc-vpn.org/) to link the LZO library with the OpenSSL library
401 (http://www.openssl.org).
403 Markus F.X.J. Oberhumer
407 @c ==================================================================
412 For the optional compression of UDP packets, tinc uses the functions provided
415 If this library is not installed, you will get an error when running the
416 configure script. You can either install the zlib library, or disable support
417 for zlib compression by using the "--disable-zlib" option when running the
418 configure script. Note that if you disable support for zlib, the resulting
419 binary will not work correctly on VPNs where zlib compression is used.
421 You can use your operating system's package manager to install this if
422 available. Make sure you install the development AND runtime versions
425 If you have to install zlib manually, you can get the source code
426 from @url{http://www.gzip.org/zlib/}. Instructions on how to configure,
427 build and install this package are included within the package. Please
428 make sure you build development and runtime libraries (which is the
432 @c ==================================================================
437 Another form of compression is offered using the LZO library.
439 If this library is not installed, you will get an error when running the
440 configure script. You can either install the LZO library, or disable support
441 for LZO compression by using the "--disable-lzo" option when running the
442 configure script. Note that if you disable support for LZO, the resulting
443 binary will not work correctly on VPNs where LZO compression is used.
445 You can use your operating system's package manager to install this if
446 available. Make sure you install the development AND runtime versions
449 If you have to install lzo manually, you can get the source code
450 from @url{http://www.oberhumer.com/opensource/lzo/}. Instructions on how to configure,
451 build and install this package are included within the package. Please
452 make sure you build development and runtime libraries (which is the
465 @c ==================================================================
467 @chapter Installation
469 If you use Debian, you may want to install one of the
470 precompiled packages for your system. These packages are equipped with
471 system startup scripts and sample configurations.
473 If you cannot use one of the precompiled packages, or you want to compile tinc
474 for yourself, you can use the source. The source is distributed under
475 the GNU General Public License (GPL). Download the source from the
476 @uref{http://www.tinc-vpn.org/download/, download page}, which has
477 the checksums of these files listed; you may wish to check these with
478 md5sum before continuing.
480 Tinc comes in a convenient autoconf/automake package, which you can just
481 treat the same as any other package. Which is just untar it, type
482 `./configure' and then `make'.
483 More detailed instructions are in the file @file{INSTALL}, which is
484 included in the source distribution.
487 * Building and installing tinc::
492 @c ==================================================================
493 @node Building and installing tinc
494 @section Building and installing tinc
496 Detailed instructions on configuring the source, building tinc and installing tinc
497 can be found in the file called @file{INSTALL}.
499 @cindex binary package
500 If you happen to have a binary package for tinc for your distribution,
501 you can use the package management tools of that distribution to install tinc.
502 The documentation that comes along with your distribution will tell you how to do that.
505 * Darwin (Mac OS X) build environment::
506 * Cygwin (Windows) build environment::
507 * MinGW (Windows) build environment::
511 @c ==================================================================
512 @node Darwin (Mac OS X) build environment
513 @subsection Darwin (Mac OS X) build environment
515 In order to build tinc on Darwin, you need to install the Mac OS X Developer Tools
516 from @uref{http://developer.apple.com/tools/macosxtools.html} and
517 preferably a recent version of Fink from @uref{http://www.finkproject.org/}.
519 After installation use fink to download and install the following packages:
520 autoconf25, automake, dlcompat, m4, openssl, zlib and lzo.
522 @c ==================================================================
523 @node Cygwin (Windows) build environment
524 @subsection Cygwin (Windows) build environment
526 If Cygwin hasn't already been installed, install it directly from
527 @uref{http://www.cygwin.com/}.
529 When tinc is compiled in a Cygwin environment, it can only be run in this environment,
530 but all programs, including those started outside the Cygwin environment, will be able to use the VPN.
531 It will also support all features.
533 @c ==================================================================
534 @node MinGW (Windows) build environment
535 @subsection MinGW (Windows) build environment
537 You will need to install the MinGW environment from @uref{http://www.mingw.org}.
539 When tinc is compiled using MinGW it runs natively under Windows,
540 it is not necessary to keep MinGW installed.
542 When detaching, tinc will install itself as a service,
543 which will be restarted automatically after reboots.
546 @c ==================================================================
548 @section System files
550 Before you can run tinc, you must make sure you have all the needed
551 files on your system.
559 @c ==================================================================
561 @subsection Device files
564 Most operating systems nowadays come with the necessary device files by default,
565 or they have a mechanism to create them on demand.
567 If you use Linux and do not have udev installed,
568 you may need to create the following device file if it does not exist:
571 mknod -m 600 /dev/net/tun c 10 200
575 @c ==================================================================
577 @subsection Other files
579 @subsubheading @file{/etc/networks}
581 You may add a line to @file{/etc/networks} so that your VPN will get a
582 symbolic name. For example:
588 @subsubheading @file{/etc/services}
591 You may add this line to @file{/etc/services}. The effect is that you
592 may supply a @samp{tinc} as a valid port number to some programs. The
593 number 655 is registered with the IANA.
598 # Ivo Timmermans <ivo@@tinc-vpn.org>
613 @c ==================================================================
615 @chapter Configuration
618 * Configuration introduction::
619 * Multiple networks::
620 * How connections work::
621 * Configuration files::
622 * Generating keypairs::
623 * Network interfaces::
624 * Example configuration::
627 @c ==================================================================
628 @node Configuration introduction
629 @section Configuration introduction
631 Before actually starting to configure tinc and editing files,
632 make sure you have read this entire section so you know what to expect.
633 Then, make it clear to yourself how you want to organize your VPN:
634 What are the nodes (computers running tinc)?
635 What IP addresses/subnets do they have?
636 What is the network mask of the entire VPN?
637 Do you need special firewall rules?
638 Do you have to set up masquerading or forwarding rules?
639 Do you want to run tinc in router mode or switch mode?
640 These questions can only be answered by yourself,
641 you will not find the answers in this documentation.
642 Make sure you have an adequate understanding of networks in general.
643 @cindex Network Administrators Guide
644 A good resource on networking is the
645 @uref{http://www.tldp.org/LDP/nag2/, Linux Network Administrators Guide}.
647 If you have everything clearly pictured in your mind,
648 proceed in the following order:
649 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
650 Then generate the keypairs.
651 Finally, distribute the host configuration files.
652 These steps are described in the subsections below.
655 @c ==================================================================
656 @node Multiple networks
657 @section Multiple networks
659 @cindex multiple networks
661 In order to allow you to run more than one tinc daemon on one computer,
662 for instance if your computer is part of more than one VPN,
663 you can assign a @var{netname} to your VPN.
664 It is not required if you only run one tinc daemon,
665 it doesn't even have to be the same on all the sites of your VPN,
666 but it is recommended that you choose one anyway.
668 We will assume you use a netname throughout this document.
669 This means that you call tincd with the -n argument,
670 which will assign a netname to this daemon.
672 The effect of this is that the daemon will set its configuration
673 root to @file{@value{sysconfdir}/tinc/@var{netname}/}, where @var{netname} is your argument to the -n
674 option. You'll notice that it appears in syslog as @file{tinc.@var{netname}}.
676 However, it is not strictly necessary that you call tinc with the -n
677 option. In this case, the network name would just be empty, and it will
678 be used as such. tinc now looks for files in @file{@value{sysconfdir}/tinc/}, instead of
679 @file{@value{sysconfdir}/tinc/@var{netname}/}; the configuration file should be @file{@value{sysconfdir}/tinc/tinc.conf},
680 and the host configuration files are now expected to be in @file{@value{sysconfdir}/tinc/hosts/}.
682 But it is highly recommended that you use this feature of tinc, because
683 it will be so much clearer whom your daemon talks to. Hence, we will
684 assume that you use it.
687 @c ==================================================================
688 @node How connections work
689 @section How connections work
691 When tinc starts up, it parses the command-line options and then
692 reads in the configuration file tinc.conf.
693 If it sees one or more `ConnectTo' values pointing to other tinc daemons in that file,
694 it will try to connect to those other daemons.
695 Whether this succeeds or not and whether `ConnectTo' is specified or not,
696 tinc will listen for incoming connection from other daemons.
697 If you did specify a `ConnectTo' value and the other side is not responding,
698 tinc will keep retrying.
699 This means that once started, tinc will stay running until you tell it to stop,
700 and failures to connect to other tinc daemons will not stop your tinc daemon
701 for trying again later.
702 This means you don't have to intervene if there are temporary network problems.
706 There is no real distinction between a server and a client in tinc.
707 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
708 and one which does specify such a value as a client.
709 It does not matter if two tinc daemons have a `ConnectTo' value pointing to each other however.
712 @c ==================================================================
713 @node Configuration files
714 @section Configuration files
716 The actual configuration of the daemon is done in the file
717 @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf} and at least one other file in the directory
718 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/}.
720 An optional directory @file{@value{sysconfdir}/tinc/@var{netname}/conf.d} can be added from which
721 any .conf file will be read.
723 These file consists of comments (lines started with a #) or assignments
730 The variable names are case insensitive, and any spaces, tabs, newlines
731 and carriage returns are ignored. Note: it is not required that you put
732 in the `=' sign, but doing so improves readability. If you leave it
733 out, remember to replace it with at least one space character.
735 The server configuration is complemented with host specific configuration (see
736 the next section). Although all host configuration options for the local node
737 listed in this document can also be put in
738 @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf}, it is recommended to
739 put host specific configuration options in the host configuration file, as this
740 makes it easy to exchange with other nodes.
742 In this section all valid variables are listed in alphabetical order.
743 The default value is given between parentheses,
744 other comments are between square brackets.
747 * Main configuration variables::
748 * Host configuration variables::
754 @c ==================================================================
755 @node Main configuration variables
756 @subsection Main configuration variables
759 @cindex AddressFamily
760 @item AddressFamily = <ipv4|ipv6|any> (any)
761 This option affects the address family of listening and outgoing sockets.
762 If any is selected, then depending on the operating system
763 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
765 @cindex BindToAddress
766 @item BindToAddress = <@var{address}> [<@var{port}>] [experimental]
767 If your computer has more than one IPv4 or IPv6 address, tinc
768 will by default listen on all of them for incoming connections.
769 Multiple BindToAddress variables may be specified,
770 in which case listening sockets for each specified address are made.
772 If no @var{port} is specified, the socket will be bound to the port specified by the Port option,
773 or to port 655 if neither is given.
774 To only bind to a specific port but not to a specific address, use "*" for the @var{address}.
776 This option may not work on all platforms.
778 @cindex BindToInterface
779 @item BindToInterface = <@var{interface}> [experimental]
780 If you have more than one network interface in your computer, tinc will
781 by default listen on all of them for incoming connections. It is
782 possible to bind tinc to a single interface like eth0 or ppp0 with this
785 This option may not work on all platforms.
788 @item Broadcast = <no | mst | direct> (mst) [experimental]
789 This option selects the way broadcast packets are sent to other daemons.
790 @emph{NOTE: all nodes in a VPN must use the same Broadcast mode, otherwise routing loops can form.}
794 Broadcast packets are never sent to other nodes.
797 Broadcast packets are sent and forwarded via the VPN's Minimum Spanning Tree.
798 This ensures broadcast packets reach all nodes.
801 Broadcast packets are sent directly to all nodes that can be reached directly.
802 Broadcast packets received from other nodes are never forwarded.
803 If the IndirectData option is also set, broadcast packets will only be sent to nodes which we have a meta connection to.
807 @item ConnectTo = <@var{name}>
808 Specifies which other tinc daemon to connect to on startup.
809 Multiple ConnectTo variables may be specified,
810 in which case outgoing connections to each specified tinc daemon are made.
811 The names should be known to this tinc daemon
812 (i.e., there should be a host configuration file for the name on the ConnectTo line).
814 If you don't specify a host with ConnectTo,
815 tinc won't try to connect to other daemons at all,
816 and will instead just listen for incoming connections.
819 @item DecrementTTL = <yes | no> (no) [experimental]
820 When enabled, tinc will decrement the Time To Live field in IPv4 packets, or the Hop Limit field in IPv6 packets,
821 before forwarding a received packet to the virtual network device or to another node,
822 and will drop packets that have a TTL value of zero,
823 in which case it will send an ICMP Time Exceeded packet back.
825 Do not use this option if you use switch mode and want to use IPv6.
828 @item Device = <@var{device}> (@file{/dev/tap0}, @file{/dev/net/tun} or other depending on platform)
829 The virtual network device to use.
830 Tinc will automatically detect what kind of device it is.
831 Under Windows, use @var{Interface} instead of @var{Device}.
832 Note that you can only use one device per daemon.
833 See also @ref{Device files}.
836 @item DeviceType = <@var{type}> (platform dependent)
837 The type of the virtual network device.
838 Tinc will normally automatically select the right type of tun/tap interface, and this option should not be used.
839 However, this option can be used to select one of the special interface types, if support for them is compiled in.
844 Use a dummy interface.
845 No packets are ever read or written to a virtual network device.
846 Useful for testing, or when setting up a node that only forwards packets for other nodes.
850 Open a raw socket, and bind it to a pre-existing
851 @var{Interface} (eth0 by default).
852 All packets are read from this interface.
853 Packets received for the local node are written to the raw socket.
854 However, at least on Linux, the operating system does not process IP packets destined for the local host.
858 Open a multicast UDP socket and bind it to the address and port (separated by spaces) and optionally a TTL value specified using @var{Device}.
859 Packets are read from and written to this multicast socket.
860 This can be used to connect to UML, QEMU or KVM instances listening on the same multicast address.
861 Do NOT connect multiple tinc daemons to the same multicast address, this will very likely cause routing loops.
862 Also note that this can cause decrypted VPN packets to be sent out on a real network if misconfigured.
865 @item uml (not compiled in by default)
866 Create a UNIX socket with the filename specified by
867 @var{Device}, or @file{@value{localstatedir}/run/@var{netname}.umlsocket}
869 Tinc will wait for a User Mode Linux instance to connect to this socket.
872 @item vde (not compiled in by default)
873 Uses the libvdeplug library to connect to a Virtual Distributed Ethernet switch,
874 using the UNIX socket specified by
875 @var{Device}, or @file{@value{localstatedir}/run/vde.ctl}
879 Also, in case tinc does not seem to correctly interpret packets received from the virtual network device,
880 it can be used to change the way packets are interpreted:
883 @item tun (BSD and Linux)
885 Depending on the platform, this can either be with or without an address family header (see below).
888 @item tunnohead (BSD)
889 Set type to tun without an address family header.
890 Tinc will expect packets read from the virtual network device to start with an IP header.
891 On some platforms IPv6 packets cannot be read from or written to the device in this mode.
894 @item tunifhead (BSD)
895 Set type to tun with an address family header.
896 Tinc will expect packets read from the virtual network device
897 to start with a four byte header containing the address family,
898 followed by an IP header.
899 This mode should support both IPv4 and IPv6 packets.
904 This is only supported on OS X version 10.6.8 and higher, but doesn't require the tuntaposx module.
905 This mode should support both IPv4 and IPv6 packets.
907 @item tap (BSD and Linux)
909 Tinc will expect packets read from the virtual network device
910 to start with an Ethernet header.
914 @item DirectOnly = <yes|no> (no) [experimental]
915 When this option is enabled, packets that cannot be sent directly to the destination node,
916 but which would have to be forwarded by an intermediate node, are dropped instead.
917 When combined with the IndirectData option,
918 packets for nodes for which we do not have a meta connection with are also dropped.
921 @item Forwarding = <off|internal|kernel> (internal) [experimental]
922 This option selects the way indirect packets are forwarded.
926 Incoming packets that are not meant for the local node,
927 but which should be forwarded to another node, are dropped.
930 Incoming packets that are meant for another node are forwarded by tinc internally.
932 This is the default mode, and unless you really know you need another forwarding mode, don't change it.
935 Incoming packets are always sent to the TUN/TAP device, even if the packets are not for the local node.
936 This is less efficient, but allows the kernel to apply its routing and firewall rules on them,
937 and can also help debugging.
940 @cindex GraphDumpFile
941 @item GraphDumpFile = <@var{filename}> [experimental]
942 If this option is present,
943 tinc will dump the current network graph to the file @var{filename}
944 every minute, unless there were no changes to the graph.
945 The file is in a format that can be read by graphviz tools.
946 If @var{filename} starts with a pipe symbol |,
947 then the rest of the filename is interpreted as a shell command
948 that is executed, the graph is then sent to stdin.
951 @item Hostnames = <yes|no> (no)
952 This option selects whether IP addresses (both real and on the VPN)
953 should be resolved. Since DNS lookups are blocking, it might affect
954 tinc's efficiency, even stopping the daemon for a few seconds every time
955 it does a lookup if your DNS server is not responding.
957 This does not affect resolving hostnames to IP addresses from the
958 configuration file, but whether hostnames should be resolved while logging.
961 @item IffOneQueue = <yes|no> (no) [experimental]
962 (Linux only) Set IFF_ONE_QUEUE flag on TUN/TAP devices.
965 @item Interface = <@var{interface}>
966 Defines the name of the interface corresponding to the virtual network device.
967 Depending on the operating system and the type of device this may or may not actually set the name of the interface.
968 Under Windows, this variable is used to select which network interface will be used.
969 If you specified a Device, this variable is almost always already correctly set.
972 @item KeyExpire = <@var{seconds}> (3600)
973 This option controls the time the encryption keys used to encrypt the data
974 are valid. It is common practice to change keys at regular intervals to
975 make it even harder for crackers, even though it is thought to be nearly
976 impossible to crack a single key.
978 @cindex LocalDiscovery
979 @item LocalDiscovery = <yes | no> (no) [experimental]
980 When enabled, tinc will try to detect peers that are on the same local network.
981 This will allow direct communication using LAN addresses, even if both peers are behind a NAT
982 and they only ConnectTo a third node outside the NAT,
983 which normally would prevent the peers from learning each other's LAN address.
985 Currently, local discovery is implemented by sending broadcast packets to the LAN during path MTU discovery.
986 This feature may not work in all possible situations.
989 @item MACExpire = <@var{seconds}> (600)
990 This option controls the amount of time MAC addresses are kept before they are removed.
991 This only has effect when Mode is set to "switch".
994 @item MaxTimeout = <@var{seconds}> (900)
995 This is the maximum delay before trying to reconnect to other tinc daemons.
998 @item Mode = <router|switch|hub> (router)
999 This option selects the way packets are routed to other daemons.
1005 variables in the host configuration files will be used to form a routing table.
1006 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
1008 This is the default mode, and unless you really know you need another mode, don't change it.
1012 In this mode the MAC addresses of the packets on the VPN will be used to
1013 dynamically create a routing table just like an Ethernet switch does.
1014 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
1015 at the cost of frequent broadcast ARP requests and routing table updates.
1017 This mode is primarily useful if you want to bridge Ethernet segments.
1021 This mode is almost the same as the switch mode, but instead
1022 every packet will be broadcast to the other daemons
1023 while no routing table is managed.
1027 @item Name = <@var{name}> [required]
1028 This is a symbolic name for this connection.
1029 The name must consist only of alphanumeric and underscore characters (a-z, A-Z, 0-9 and _).
1031 If Name starts with a $, then the contents of the environment variable that follows will be used.
1032 In that case, invalid characters will be converted to underscores.
1033 If Name is $HOST, but no such environment variable exist,
1034 the hostname will be read using the gethostname() system call.
1036 @cindex PingInterval
1037 @item PingInterval = <@var{seconds}> (60)
1038 The number of seconds of inactivity that tinc will wait before sending a
1039 probe to the other end.
1042 @item PingTimeout = <@var{seconds}> (5)
1043 The number of seconds to wait for a response to pings or to allow meta
1044 connections to block. If the other end doesn't respond within this time,
1045 the connection is terminated, and the others will be notified of this.
1047 @cindex PriorityInheritance
1048 @item PriorityInheritance = <yes|no> (no) [experimental]
1049 When this option is enabled the value of the TOS field of tunneled IPv4 packets
1050 will be inherited by the UDP packets that are sent out.
1053 @item PrivateKey = <@var{key}> [obsolete]
1054 This is the RSA private key for tinc. However, for safety reasons it is
1055 advised to store private keys of any kind in separate files. This prevents
1056 accidental eavesdropping if you are editing the configuration file.
1058 @cindex PrivateKeyFile
1059 @item PrivateKeyFile = <@var{path}> (@file{@value{sysconfdir}/tinc/@var{netname}/rsa_key.priv})
1060 This is the full path name of the RSA private key file that was
1061 generated by @samp{tincd --generate-keys}. It must be a full path, not a
1064 @cindex ProcessPriority
1065 @item ProcessPriority = <low|normal|high>
1066 When this option is used the priority of the tincd process will be adjusted.
1067 Increasing the priority may help to reduce latency and packet loss on the VPN.
1070 @item Proxy = socks4 | socks5 | http | exec @var{...} [experimental]
1071 Use a proxy when making outgoing connections.
1072 The following proxy types are currently supported:
1076 @item socks4 <@var{address}> <@var{port}> [<@var{username}>]
1077 Connects to the proxy using the SOCKS version 4 protocol.
1078 Optionally, a @var{username} can be supplied which will be passed on to the proxy server.
1081 @item socks5 <@var{address}> <@var{port}> [<@var{username}> <@var{password}>]
1082 Connect to the proxy using the SOCKS version 5 protocol.
1083 If a @var{username} and @var{password} are given, basic username/password authentication will be used,
1084 otherwise no authentication will be used.
1087 @item http <@var{address}> <@var{port}>
1088 Connects to the proxy and sends a HTTP CONNECT request.
1091 @item exec <@var{command}>
1092 Executes the given command which should set up the outgoing connection.
1093 The environment variables @env{NAME}, @env{NODE}, @env{REMOTEADDRES} and @env{REMOTEPORT} are available.
1096 @cindex ReplayWindow
1097 @item ReplayWindow = <bytes> (16)
1098 This is the size of the replay tracking window for each remote node, in bytes.
1099 The window is a bitfield which tracks 1 packet per bit, so for example
1100 the default setting of 16 will track up to 128 packets in the window. In high
1101 bandwidth scenarios, setting this to a higher value can reduce packet loss from
1102 the interaction of replay tracking with underlying real packet loss and/or
1103 reordering. Setting this to zero will disable replay tracking completely and
1104 pass all traffic, but leaves tinc vulnerable to replay-based attacks on your
1107 @cindex StrictSubnets
1108 @item StrictSubnets = <yes|no> (no) [experimental]
1109 When this option is enabled tinc will only use Subnet statements which are
1110 present in the host config files in the local
1111 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
1112 Subnets learned via connections to other nodes and which are not
1113 present in the local host config files are ignored.
1115 @cindex TunnelServer
1116 @item TunnelServer = <yes|no> (no) [experimental]
1117 When this option is enabled tinc will no longer forward information between other tinc daemons,
1118 and will only allow connections with nodes for which host config files are present in the local
1119 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
1120 Setting this options also implicitly sets StrictSubnets.
1123 @item UDPRcvBuf = <bytes> (OS default)
1124 Sets the socket receive buffer size for the UDP socket, in bytes.
1125 If unset, the default buffer size will be used by the operating system.
1128 @item UDPSndBuf = <bytes> Pq OS default
1129 Sets the socket send buffer size for the UDP socket, in bytes.
1130 If unset, the default buffer size will be used by the operating system.
1135 @c ==================================================================
1136 @node Host configuration variables
1137 @subsection Host configuration variables
1141 @item Address = <@var{IP address}|@var{hostname}> [<port>] [recommended]
1142 This variable is only required if you want to connect to this host. It
1143 must resolve to the external IP address where the host can be reached,
1144 not the one that is internal to the VPN.
1145 If no port is specified, the default Port is used.
1146 Multiple Address variables can be specified, in which case each address will be
1147 tried until a working connection has been established.
1150 @item Cipher = <@var{cipher}> (blowfish)
1151 The symmetric cipher algorithm used to encrypt UDP packets.
1152 Any cipher supported by OpenSSL is recognized.
1153 Furthermore, specifying "none" will turn off packet encryption.
1154 It is best to use only those ciphers which support CBC mode.
1157 @item ClampMSS = <yes|no> (yes)
1158 This option specifies whether tinc should clamp the maximum segment size (MSS)
1159 of TCP packets to the path MTU. This helps in situations where ICMP
1160 Fragmentation Needed or Packet too Big messages are dropped by firewalls.
1163 @item Compression = <@var{level}> (0)
1164 This option sets the level of compression used for UDP packets.
1165 Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
1166 10 (fast lzo) and 11 (best lzo).
1169 @item Digest = <@var{digest}> (sha1)
1170 The digest algorithm used to authenticate UDP packets.
1171 Any digest supported by OpenSSL is recognized.
1172 Furthermore, specifying "none" will turn off packet authentication.
1174 @cindex IndirectData
1175 @item IndirectData = <yes|no> (no)
1176 This option specifies whether other tinc daemons besides the one you
1177 specified with ConnectTo can make a direct connection to you. This is
1178 especially useful if you are behind a firewall and it is impossible to
1179 make a connection from the outside to your tinc daemon. Otherwise, it
1180 is best to leave this option out or set it to no.
1183 @item MACLength = <@var{bytes}> (4)
1184 The length of the message authentication code used to authenticate UDP packets.
1185 Can be anything from 0
1186 up to the length of the digest produced by the digest algorithm.
1189 @item PMTU = <@var{mtu}> (1514)
1190 This option controls the initial path MTU to this node.
1192 @cindex PMTUDiscovery
1193 @item PMTUDiscovery = <yes|no> (yes)
1194 When this option is enabled, tinc will try to discover the path MTU to this node.
1195 After the path MTU has been discovered, it will be enforced on the VPN.
1198 @item Port = <@var{port}> (655)
1199 This is the port this tinc daemon listens on.
1200 You can use decimal portnumbers or symbolic names (as listed in @file{/etc/services}).
1203 @item PublicKey = <@var{key}> [obsolete]
1204 This is the RSA public key for this host.
1206 @cindex PublicKeyFile
1207 @item PublicKeyFile = <@var{path}> [obsolete]
1208 This is the full path name of the RSA public key file that was generated
1209 by @samp{tincd --generate-keys}. It must be a full path, not a relative
1213 From version 1.0pre4 on tinc will store the public key directly into the
1214 host configuration file in PEM format, the above two options then are not
1215 necessary. Either the PEM format is used, or exactly
1216 @strong{one of the above two options} must be specified
1217 in each host configuration file, if you want to be able to establish a
1218 connection with that host.
1221 @item Subnet = <@var{address}[/@var{prefixlength}[#@var{weight}]]>
1222 The subnet which this tinc daemon will serve.
1223 Tinc tries to look up which other daemon it should send a packet to by searching the appropriate subnet.
1224 If the packet matches a subnet,
1225 it will be sent to the daemon who has this subnet in his host configuration file.
1226 Multiple subnet lines can be specified for each daemon.
1228 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1229 in which case a subnet consisting of only that single address is assumed,
1230 or they can be a IPv4 or IPv6 network address with a prefixlength.
1231 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1232 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1233 Note that subnets like 192.168.1.1/24 are invalid!
1234 Read a networking HOWTO/FAQ/guide if you don't understand this.
1235 IPv6 subnets are notated like fec0:0:0:1::/64.
1236 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1238 @cindex CIDR notation
1239 Prefixlength is the number of bits set to 1 in the netmask part; for
1240 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1241 /22. This conforms to standard CIDR notation as described in
1242 @uref{http://www.ietf.org/rfc/rfc1519.txt, RFC1519}
1244 @cindex Subnet weight
1245 A Subnet can be given a weight to indicate its priority over identical Subnets
1246 owned by different nodes. The default weight is 10. Lower values indicate
1247 higher priority. Packets will be sent to the node with the highest priority,
1248 unless that node is not reachable, in which case the node with the next highest
1249 priority will be tried, and so on.
1252 @item TCPonly = <yes|no> (no) [deprecated]
1253 If this variable is set to yes, then the packets are tunnelled over a
1254 TCP connection instead of a UDP connection. This is especially useful
1255 for those who want to run a tinc daemon from behind a masquerading
1256 firewall, or if UDP packet routing is disabled somehow.
1257 Setting this options also implicitly sets IndirectData.
1259 Since version 1.0.10, tinc will automatically detect whether communication via
1260 UDP is possible or not.
1264 @c ==================================================================
1269 Apart from reading the server and host configuration files,
1270 tinc can also run scripts at certain moments.
1271 Below is a list of filenames of scripts and a description of when they are run.
1272 A script is only run if it exists and if it is executable.
1274 Scripts are run synchronously;
1275 this means that tinc will temporarily stop processing packets until the called script finishes executing.
1276 This guarantees that scripts will execute in the exact same order as the events that trigger them.
1277 If you need to run commands asynchronously, you have to ensure yourself that they are being run in the background.
1279 Under Windows (not Cygwin), the scripts must have the extension .bat.
1283 @item @value{sysconfdir}/tinc/@var{netname}/tinc-up
1284 This is the most important script.
1285 If it is present it will be executed right after the tinc daemon has been
1286 started and has connected to the virtual network device.
1287 It should be used to set up the corresponding network interface,
1288 but can also be used to start other things.
1290 Under Windows you can use the Network Connections control panel instead of creating this script.
1293 @item @value{sysconfdir}/tinc/@var{netname}/tinc-down
1294 This script is started right before the tinc daemon quits.
1296 @item @value{sysconfdir}/tinc/@var{netname}/hosts/@var{host}-up
1297 This script is started when the tinc daemon with name @var{host} becomes reachable.
1299 @item @value{sysconfdir}/tinc/@var{netname}/hosts/@var{host}-down
1300 This script is started when the tinc daemon with name @var{host} becomes unreachable.
1302 @item @value{sysconfdir}/tinc/@var{netname}/host-up
1303 This script is started when any host becomes reachable.
1305 @item @value{sysconfdir}/tinc/@var{netname}/host-down
1306 This script is started when any host becomes unreachable.
1308 @item @value{sysconfdir}/tinc/@var{netname}/subnet-up
1309 This script is started when a subnet becomes reachable.
1310 The Subnet and the node it belongs to are passed in environment variables.
1312 @item @value{sysconfdir}/tinc/@var{netname}/subnet-down
1313 This script is started when a subnet becomes unreachable.
1316 @cindex environment variables
1317 The scripts are started without command line arguments,
1318 but can make use of certain environment variables.
1319 Under UNIX like operating systems the names of environment variables must be preceded by a $ in scripts.
1320 Under Windows, in @file{.bat} files, they have to be put between % signs.
1325 If a netname was specified, this environment variable contains it.
1329 Contains the name of this tinc daemon.
1333 Contains the name of the virtual network device that tinc uses.
1337 Contains the name of the virtual network interface that tinc uses.
1338 This should be used for commands like ifconfig.
1342 When a host becomes (un)reachable, this is set to its name.
1343 If a subnet becomes (un)reachable, this is set to the owner of that subnet.
1345 @cindex REMOTEADDRESS
1347 When a host becomes (un)reachable, this is set to its real address.
1351 When a host becomes (un)reachable,
1352 this is set to the port number it uses for communication with other tinc daemons.
1356 When a subnet becomes (un)reachable, this is set to the subnet.
1360 When a subnet becomes (un)reachable, this is set to the subnet weight.
1365 @c ==================================================================
1366 @node How to configure
1367 @subsection How to configure
1369 @subsubheading Step 1. Creating the main configuration file
1371 The main configuration file will be called @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf}.
1372 Adapt the following example to create a basic configuration file:
1375 Name = @var{yourname}
1376 Device = @file{/dev/tap0}
1379 Then, if you know to which other tinc daemon(s) yours is going to connect,
1380 add `ConnectTo' values.
1382 @subsubheading Step 2. Creating your host configuration file
1384 If you added a line containing `Name = yourname' in the main configuration file,
1385 you will need to create a host configuration file @file{@value{sysconfdir}/tinc/@var{netname}/hosts/yourname}.
1386 Adapt the following example to create a host configuration file:
1389 Address = your.real.hostname.org
1390 Subnet = 192.168.1.0/24
1393 You can also use an IP address instead of a hostname.
1394 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1395 If you have multiple address ranges you can specify more than one `Subnet'.
1396 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).
1399 @c ==================================================================
1400 @node Generating keypairs
1401 @section Generating keypairs
1403 @cindex key generation
1404 Now that you have already created the main configuration file and your host configuration file,
1405 you can easily create a public/private keypair by entering the following command:
1408 tincd -n @var{netname} -K
1411 Tinc will generate a public and a private key and ask you where to put them.
1412 Just press enter to accept the defaults.
1415 @c ==================================================================
1416 @node Network interfaces
1417 @section Network interfaces
1419 Before tinc can start transmitting data over the tunnel, it must
1420 set up the virtual network interface.
1422 First, decide which IP addresses you want to have associated with these
1423 devices, and what network mask they must have.
1425 Tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1426 which will also create a network interface called something like @samp{tun0}, @samp{tap0}.
1427 If you are using the Linux tun/tap driver, the network interface will by default have the same name as the @var{netname}.
1428 Under Windows you can change the name of the network interface from the Network Connections control panel.
1431 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1432 to a script named @file{@value{sysconfdir}/tinc/@var{netname}/tinc-up}.
1433 When tinc starts, this script will be executed. When tinc exits, it will execute the script named
1434 @file{@value{sysconfdir}/tinc/@var{netname}/tinc-down}, but normally you don't need to create that script.
1436 An example @file{tinc-up} script:
1440 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1443 This script gives the interface an IP address and a netmask.
1444 The kernel will also automatically add a route to this interface, so normally you don't need
1445 to add route commands to the @file{tinc-up} script.
1446 The kernel will also bring the interface up after this command.
1448 The netmask is the mask of the @emph{entire} VPN network, not just your
1451 The exact syntax of the ifconfig and route commands differs from platform to platform.
1452 You can look up the commands for setting addresses and adding routes in @ref{Platform specific information},
1453 but it is best to consult the manpages of those utilities on your platform.
1456 @c ==================================================================
1457 @node Example configuration
1458 @section Example configuration
1462 Imagine the following situation. Branch A of our example `company' wants to connect
1463 three branch offices in B, C and D using the Internet. All four offices
1464 have a 24/7 connection to the Internet.
1466 A is going to serve as the center of the network. B and C will connect
1467 to A, and D will connect to C. Each office will be assigned their own IP
1471 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1472 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1473 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1474 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1477 Here, ``gateway'' is the VPN IP address of the machine that is running the
1478 tincd, and ``internet IP'' is the IP address of the firewall, which does not
1479 need to run tincd, but it must do a port forwarding of TCP and UDP on port
1480 655 (unless otherwise configured).
1482 In this example, it is assumed that eth0 is the interface that points to
1483 the inner (physical) LAN of the office, although this could also be the
1484 same as the interface that leads to the Internet. The configuration of
1485 the real interface is also shown as a comment, to give you an idea of
1486 how these example host is set up. All branches use the netname `company'
1487 for this particular VPN.
1489 @subsubheading For Branch A
1491 @emph{BranchA} would be configured like this:
1493 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1496 # Real interface of internal network:
1497 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0
1499 ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
1502 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1509 On all hosts, @file{@value{sysconfdir}/tinc/company/hosts/BranchA} contains:
1512 Subnet = 10.1.0.0/16
1515 -----BEGIN RSA PUBLIC KEY-----
1517 -----END RSA PUBLIC KEY-----
1520 Note that the IP addresses of eth0 and tap0 are the same.
1521 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1522 It is in fact recommended to give both real internal network interfaces and tap interfaces the same IP address,
1523 since that will make things a lot easier to remember and set up.
1526 @subsubheading For Branch B
1528 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1531 # Real interface of internal network:
1532 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0
1534 ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
1537 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1544 Note here that the internal address (on eth0) doesn't have to be the
1545 same as on the tap0 device. Also, ConnectTo is given so that this node will
1546 always try to connect to BranchA.
1548 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchB}:
1551 Subnet = 10.2.0.0/16
1554 -----BEGIN RSA PUBLIC KEY-----
1556 -----END RSA PUBLIC KEY-----
1560 @subsubheading For Branch C
1562 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1565 # Real interface of internal network:
1566 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0
1568 ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
1571 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1579 C already has another daemon that runs on port 655, so they have to
1580 reserve another port for tinc. It knows the portnumber it has to listen on
1581 from it's own host configuration file.
1583 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchC}:
1587 Subnet = 10.3.0.0/16
1590 -----BEGIN RSA PUBLIC KEY-----
1592 -----END RSA PUBLIC KEY-----
1596 @subsubheading For Branch D
1598 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1601 # Real interface of internal network:
1602 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0
1604 ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
1607 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1612 Device = /dev/net/tun
1615 D will be connecting to C, which has a tincd running for this network on
1616 port 2000. It knows the port number from the host configuration file.
1617 Also note that since D uses the tun/tap driver, the network interface
1618 will not be called `tun' or `tap0' or something like that, but will
1619 have the same name as netname.
1621 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchD}:
1624 Subnet = 10.4.0.0/16
1627 -----BEGIN RSA PUBLIC KEY-----
1629 -----END RSA PUBLIC KEY-----
1632 @subsubheading Key files
1634 A, B, C and D all have generated a public/private keypair with the following command:
1640 The private key is stored in @file{@value{sysconfdir}/tinc/company/rsa_key.priv},
1641 the public key is put into the host configuration file in the @file{@value{sysconfdir}/tinc/company/hosts/} directory.
1642 During key generation, tinc automatically guesses the right filenames based on the -n option and
1643 the Name directive in the @file{tinc.conf} file (if it is available).
1645 @subsubheading Starting
1647 After each branch has finished configuration and they have distributed
1648 the host configuration files amongst them, they can start their tinc daemons.
1649 They don't necessarily have to wait for the other branches to have started
1650 their daemons, tinc will try connecting until they are available.
1653 @c ==================================================================
1655 @chapter Running tinc
1657 If everything else is done, you can start tinc by typing the following command:
1660 tincd -n @var{netname}
1664 Tinc will detach from the terminal and continue to run in the background like a good daemon.
1665 If there are any problems however you can try to increase the debug level
1666 and look in the syslog to find out what the problems are.
1672 * Solving problems::
1674 * Sending bug reports::
1678 @c ==================================================================
1679 @node Runtime options
1680 @section Runtime options
1682 Besides the settings in the configuration file, tinc also accepts some
1683 command line options.
1685 @cindex command line
1686 @cindex runtime options
1690 @item -c, --config=@var{path}
1691 Read configuration options from the directory @var{path}. The default is
1692 @file{@value{sysconfdir}/tinc/@var{netname}/}.
1694 @item -D, --no-detach
1695 Don't fork and detach.
1696 This will also disable the automatic restart mechanism for fatal errors.
1699 @item -d, --debug=@var{level}
1700 Set debug level to @var{level}. The higher the debug level, the more gets
1701 logged. Everything goes via syslog.
1703 @item -k, --kill[=@var{signal}]
1704 Attempt to kill a running tincd (optionally with the specified @var{signal} instead of SIGTERM) and exit.
1705 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1706 Under native Windows the optional argument is ignored,
1707 the service will always be stopped and removed.
1709 @item -n, --net=@var{netname}
1710 Use configuration for net @var{netname}.
1711 This will let tinc read all configuration files from
1712 @file{@value{sysconfdir}/tinc/@var{netname}/}.
1713 Specifying . for @var{netname} is the same as not specifying any @var{netname}.
1714 @xref{Multiple networks}.
1716 @item -K, --generate-keys[=@var{bits}]
1717 Generate public/private keypair of @var{bits} length. If @var{bits} is not specified,
1718 2048 is the default. tinc will ask where you want to store the files,
1719 but will default to the configuration directory (you can use the -c or -n option
1720 in combination with -K). After that, tinc will quit.
1722 @item -o, --option=[@var{HOST}.]@var{KEY}=@var{VALUE}
1723 Without specifying a @var{HOST}, this will set server configuration variable @var{KEY} to @var{VALUE}.
1724 If specified as @var{HOST}.@var{KEY}=@var{VALUE},
1725 this will set the host configuration variable @var{KEY} of the host named @var{HOST} to @var{VALUE}.
1726 This option can be used more than once to specify multiple configuration variables.
1729 Lock tinc into main memory.
1730 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1732 @item --logfile[=@var{file}]
1733 Write log entries to a file instead of to the system logging facility.
1734 If @var{file} is omitted, the default is @file{@value{localstatedir}/log/tinc.@var{netname}.log}.
1736 @item --pidfile=@var{file}
1737 Write PID to @var{file} instead of @file{@value{localstatedir}/run/tinc.@var{netname}.pid}.
1739 @item --bypass-security
1740 Disables encryption and authentication.
1741 Only useful for debugging.
1744 Change process root directory to the directory where the config file is
1745 located (@file{@value{sysconfdir}/tinc/@var{netname}/} as determined by
1746 -n/--net option or as given by -c/--config option), for added security.
1747 The chroot is performed after all the initialization is done, after
1748 writing pid files and opening network sockets.
1750 Note that this option alone does not do any good without -U/--user, below.
1752 Note also that tinc can't run scripts anymore (such as tinc-down or host-up),
1753 unless it's setup to be runnable inside chroot environment.
1755 @item -U, --user=@var{user}
1756 Switch to the given @var{user} after initialization, at the same time as
1757 chroot is performed (see --chroot above). With this option tinc drops
1758 privileges, for added security.
1761 Display a short reminder of these runtime options and terminate.
1764 Output version information and exit.
1768 @c ==================================================================
1773 You can also send the following signals to a running tincd process:
1779 Forces tinc to try to connect to all uplinks immediately.
1780 Usually tinc attempts to do this itself,
1781 but increases the time it waits between the attempts each time it failed,
1782 and if tinc didn't succeed to connect to an uplink the first time after it started,
1783 it defaults to the maximum time of 15 minutes.
1786 Partially rereads configuration files.
1787 Connections to hosts whose host config file are removed are closed.
1788 New outgoing connections specified in @file{tinc.conf} will be made.
1789 If the --logfile option is used, this will also close and reopen the log file,
1790 useful when log rotation is used.
1793 Temporarily increases debug level to 5.
1794 Send this signal again to revert to the original level.
1797 Dumps the connection list to syslog.
1800 Dumps virtual network device statistics, all known nodes, edges and subnets to syslog.
1803 Purges all information remembered about unreachable nodes.
1807 @c ==================================================================
1809 @section Debug levels
1811 @cindex debug levels
1812 The tinc daemon can send a lot of messages to the syslog.
1813 The higher the debug level, the more messages it will log.
1814 Each level inherits all messages of the previous level:
1820 This will log a message indicating tinc has started along with a version number.
1821 It will also log any serious error.
1824 This will log all connections that are made with other tinc daemons.
1827 This will log status and error messages from scripts and other tinc daemons.
1830 This will log all requests that are exchanged with other tinc daemons. These include
1831 authentication, key exchange and connection list updates.
1834 This will log a copy of everything received on the meta socket.
1837 This will log all network traffic over the virtual private network.
1841 @c ==================================================================
1842 @node Solving problems
1843 @section Solving problems
1845 If tinc starts without problems, but if the VPN doesn't work, you will have to find the cause of the problem.
1846 The first thing to do is to start tinc with a high debug level in the foreground,
1847 so you can directly see everything tinc logs:
1850 tincd -n @var{netname} -d5 -D
1853 If tinc does not log any error messages, then you might want to check the following things:
1856 @item @file{tinc-up} script
1857 Does this script contain the right commands?
1858 Normally you must give the interface the address of this host on the VPN, and the netmask must be big enough so that the entire VPN is covered.
1861 Does the Subnet (or Subnets) in the host configuration file of this host match the portion of the VPN that belongs to this host?
1863 @item Firewalls and NATs
1864 Do you have a firewall or a NAT device (a masquerading firewall or perhaps an ADSL router that performs masquerading)?
1865 If so, check that it allows TCP and UDP traffic on port 655.
1866 If it masquerades and the host running tinc is behind it, make sure that it forwards TCP and UDP traffic to port 655 to the host running tinc.
1867 You can add @samp{TCPOnly = yes} to your host config file to force tinc to only use a single TCP connection,
1868 this works through most firewalls and NATs. Since version 1.0.10, tinc will automatically fall back to TCP if direct communication via UDP is not possible.
1873 @c ==================================================================
1874 @node Error messages
1875 @section Error messages
1877 What follows is a list of the most common error messages you might find in the logs.
1878 Some of them will only be visible if the debug level is high enough.
1881 @item Could not open /dev/tap0: No such device
1884 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1885 @item You forgot to compile `Netlink device emulation' in the kernel.
1888 @item Can't write to /dev/net/tun: No such device
1891 @item You forgot to `modprobe tun'.
1892 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1893 @item The tun device is located somewhere else in @file{/dev/}.
1896 @item Network address and prefix length do not match!
1899 @item The Subnet field must contain a @emph{network} address, trailing bits should be 0.
1900 @item If you only want to use one IP address, set the netmask to /32.
1903 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1906 @item You forgot to create a public/private keypair.
1907 @item Specify the complete pathname to the private key file with the @samp{PrivateKeyFile} option.
1910 @item Warning: insecure file permissions for RSA private key file `rsa_key.priv'!
1913 @item The private key file is readable by users other than root.
1914 Use chmod to correct the file permissions.
1917 @item Creating metasocket failed: Address family not supported
1920 @item By default tinc tries to create both IPv4 and IPv6 sockets.
1921 On some platforms this might not be implemented.
1922 If the logs show @samp{Ready} later on, then at least one metasocket was created,
1923 and you can ignore this message.
1924 You can add @samp{AddressFamily = ipv4} to @file{tinc.conf} to prevent this from happening.
1927 @item Cannot route packet: unknown IPv4 destination 1.2.3.4
1930 @item You try to send traffic to a host on the VPN for which no Subnet is known.
1931 @item If it is a broadcast address (ending in .255), it probably is a samba server or a Windows host sending broadcast packets.
1935 @item Cannot route packet: ARP request for unknown address 1.2.3.4
1938 @item You try to send traffic to a host on the VPN for which no Subnet is known.
1941 @item Packet with destination 1.2.3.4 is looping back to us!
1944 @item Something is not configured right. Packets are being sent out to the
1945 virtual network device, but according to the Subnet directives in your host configuration
1946 file, those packets should go to your own host. Most common mistake is that
1947 you have a Subnet line in your host configuration file with a prefix length which is
1948 just as large as the prefix of the virtual network interface. The latter should in almost all
1949 cases be larger. Rethink your configuration.
1950 Note that you will only see this message if you specified a debug
1951 level of 5 or higher!
1952 @item Chances are that a @samp{Subnet = ...} line in the host configuration file of this tinc daemon is wrong.
1953 Change it to a subnet that is accepted locally by another interface,
1954 or if that is not the case, try changing the prefix length into /32.
1957 @item Node foo (1.2.3.4) is not reachable
1960 @item Node foo does not have a connection anymore, its tinc daemon is not running or its connection to the Internet is broken.
1963 @item Received UDP packet from unknown source 1.2.3.4 (port 12345)
1966 @item If you see this only sporadically, it is harmless and caused by a node sending packets using an old key.
1969 @item Got bad/bogus/unauthorized REQUEST from foo (1.2.3.4 port 12345)
1972 @item Node foo does not have the right public/private keypair.
1973 Generate new keypairs and distribute them again.
1974 @item An attacker tries to gain access to your VPN.
1975 @item A network error caused corruption of metadata sent from foo.
1980 @c ==================================================================
1981 @node Sending bug reports
1982 @section Sending bug reports
1984 If you really can't find the cause of a problem, or if you suspect tinc is not working right,
1985 you can send us a bugreport, see @ref{Contact information}.
1986 Be sure to include the following information in your bugreport:
1989 @item A clear description of what you are trying to achieve and what the problem is.
1990 @item What platform (operating system, version, hardware architecture) and which version of tinc you use.
1991 @item If compiling tinc fails, a copy of @file{config.log} and the error messages you get.
1992 @item Otherwise, a copy of @file{tinc.conf}, @file{tinc-up} and all files in the @file{hosts/} directory.
1993 @item The output of the commands @samp{ifconfig -a} and @samp{route -n} (or @samp{netstat -rn} if that doesn't work).
1994 @item The output of any command that fails to work as it should (like ping or traceroute).
1997 @c ==================================================================
1998 @node Technical information
1999 @chapter Technical information
2004 * The meta-protocol::
2009 @c ==================================================================
2010 @node The connection
2011 @section The connection
2014 Tinc is a daemon that takes VPN data and transmit that to another host
2015 computer over the existing Internet infrastructure.
2019 * The meta-connection::
2023 @c ==================================================================
2024 @node The UDP tunnel
2025 @subsection The UDP tunnel
2027 @cindex virtual network device
2029 The data itself is read from a character device file, the so-called
2030 @emph{virtual network device}. This device is associated with a network
2031 interface. Any data sent to this interface can be read from the device,
2032 and any data written to the device gets sent from the interface.
2033 There are two possible types of virtual network devices:
2034 `tun' style, which are point-to-point devices which can only handle IPv4 and/or IPv6 packets,
2035 and `tap' style, which are Ethernet devices and handle complete Ethernet frames.
2037 So when tinc reads an Ethernet frame from the device, it determines its
2038 type. When tinc is in its default routing mode, it can handle IPv4 and IPv6
2039 packets. Depending on the Subnet lines, it will send the packets off to their destination IP address.
2040 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
2041 to deduce the destination of the packets.
2042 Since the latter modes only depend on the link layer information,
2043 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
2044 However, only `tap' style devices provide this information.
2046 After the destination has been determined,
2047 the packet will be compressed (optionally),
2048 a sequence number will be added to the packet,
2049 the packet will then be encrypted
2050 and a message authentication code will be appended.
2052 @cindex encapsulating
2054 When that is done, time has come to actually transport the
2055 packet to the destination computer. We do this by sending the packet
2056 over an UDP connection to the destination host. This is called
2057 @emph{encapsulating}, the VPN packet (though now encrypted) is
2058 encapsulated in another IP datagram.
2060 When the destination receives this packet, the same thing happens, only
2061 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
2062 checks the sequence number
2063 and writes the decrypted information to its own virtual network device.
2065 If the virtual network device is a `tun' device (a point-to-point tunnel),
2066 there is no problem for the kernel to accept a packet.
2067 However, if it is a `tap' device (this is the only available type on FreeBSD),
2068 the destination MAC address must match that of the virtual network interface.
2069 If tinc is in its default routing mode, ARP does not work, so the correct destination MAC
2070 can not be known by the sending host.
2071 Tinc solves this by letting the receiving end detect the MAC address of its own virtual network interface
2072 and overwriting the destination MAC address of the received packet.
2074 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
2075 In those modes every interface should have a unique MAC address, so make sure they are not the same.
2076 Because switch and hub modes rely on MAC addresses to function correctly,
2077 these modes cannot be used on the following operating systems which don't have a `tap' style virtual network device:
2078 OpenBSD, NetBSD, Darwin and Solaris.
2081 @c ==================================================================
2082 @node The meta-connection
2083 @subsection The meta-connection
2085 Having only a UDP connection available is not enough. Though suitable
2086 for transmitting data, we want to be able to reliably send other
2087 information, such as routing and session key information to somebody.
2090 TCP is a better alternative, because it already contains protection
2091 against information being lost, unlike UDP.
2093 So we establish two connections. One for the encrypted VPN data, and one
2094 for other information, the meta-data. Hence, we call the second
2095 connection the meta-connection. We can now be sure that the
2096 meta-information doesn't get lost on the way to another computer.
2098 @cindex data-protocol
2099 @cindex meta-protocol
2100 Like with any communication, we must have a protocol, so that everybody
2101 knows what everything stands for, and how she should react. Because we
2102 have two connections, we also have two protocols. The protocol used for
2103 the UDP data is the ``data-protocol,'' the other one is the
2106 The reason we don't use TCP for both protocols is that UDP is much
2107 better for encapsulation, even while it is less reliable. The real
2108 problem is that when TCP would be used to encapsulate a TCP stream
2109 that's on the private network, for every packet sent there would be
2110 three ACKs sent instead of just one. Furthermore, if there would be
2111 a timeout, both TCP streams would sense the timeout, and both would
2112 start re-sending packets.
2115 @c ==================================================================
2116 @node The meta-protocol
2117 @section The meta-protocol
2119 The meta protocol is used to tie all tinc daemons together, and
2120 exchange information about which tinc daemon serves which virtual
2123 The meta protocol consists of requests that can be sent to the other
2124 side. Each request has a unique number and several parameters. All
2125 requests are represented in the standard ASCII character set. It is
2126 possible to use tools such as telnet or netcat to connect to a tinc
2127 daemon started with the --bypass-security option
2128 and to read and write requests by hand, provided that one
2129 understands the numeric codes sent.
2131 The authentication scheme is described in @ref{Authentication protocol}. After a
2132 successful authentication, the server and the client will exchange all the
2133 information about other tinc daemons and subnets they know of, so that both
2134 sides (and all the other tinc daemons behind them) have their information
2141 ------------------------------------------------------------------
2142 ADD_EDGE node1 node2 21.32.43.54 655 222 0
2143 | | | | | +-> options
2144 | | | | +----> weight
2145 | | | +--------> UDP port of node2
2146 | | +----------------> real address of node2
2147 | +-------------------------> name of destination node
2148 +-------------------------------> name of source node
2150 ADD_SUBNET node 192.168.1.0/24
2151 | | +--> prefixlength
2152 | +--------> network address
2153 +------------------> owner of this subnet
2154 ------------------------------------------------------------------
2157 The ADD_EDGE messages are to inform other tinc daemons that a connection between
2158 two nodes exist. The address of the destination node is available so that
2159 VPN packets can be sent directly to that node.
2161 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
2162 to certain nodes. tinc will use it to determine to which node a VPN packet has
2169 ------------------------------------------------------------------
2170 DEL_EDGE node1 node2
2171 | +----> name of destination node
2172 +----------> name of source node
2174 DEL_SUBNET node 192.168.1.0/24
2175 | | +--> prefixlength
2176 | +--------> network address
2177 +------------------> owner of this subnet
2178 ------------------------------------------------------------------
2181 In case a connection between two daemons is closed or broken, DEL_EDGE messages
2182 are sent to inform the other daemons of that fact. Each daemon will calculate a
2183 new route to the the daemons, or mark them unreachable if there isn't any.
2190 ------------------------------------------------------------------
2191 REQ_KEY origin destination
2192 | +--> name of the tinc daemon it wants the key from
2193 +----------> name of the daemon that wants the key
2195 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
2196 | | \______________/ | | +--> MAC length
2197 | | | | +-----> digest algorithm
2198 | | | +--------> cipher algorithm
2199 | | +--> 128 bits key
2200 | +--> name of the daemon that wants the key
2201 +----------> name of the daemon that uses this key
2204 +--> daemon that has changed it's packet key
2205 ------------------------------------------------------------------
2208 The keys used to encrypt VPN packets are not sent out directly. This is
2209 because it would generate a lot of traffic on VPNs with many daemons, and
2210 chances are that not every tinc daemon will ever send a packet to every
2211 other daemon. Instead, if a daemon needs a key it sends a request for it
2212 via the meta connection of the nearest hop in the direction of the
2219 ------------------------------------------------------------------
2222 ------------------------------------------------------------------
2225 There is also a mechanism to check if hosts are still alive. Since network
2226 failures or a crash can cause a daemon to be killed without properly
2227 shutting down the TCP connection, this is necessary to keep an up to date
2228 connection list. PINGs are sent at regular intervals, except when there
2229 is also some other traffic. A little bit of salt (random data) is added
2230 with each PING and PONG message, to make sure that long sequences of PING/PONG
2231 messages without any other traffic won't result in known plaintext.
2233 This basically covers what is sent over the meta connection by tinc.
2236 @c ==================================================================
2242 Tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
2243 alleged Cabal was/is an organisation that was said to keep an eye on the
2244 entire Internet. As this is exactly what you @emph{don't} want, we named
2245 the tinc project after TINC.
2248 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
2249 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
2250 exactly that: encrypt.
2251 Tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
2252 sequence numbers and 4 byte long message authentication codes to make sure
2253 eavesdroppers cannot get and cannot change any information at all from the
2254 packets they can intercept. The encryption algorithm and message authentication
2255 algorithm can be changed in the configuration. The length of the message
2256 authentication codes is also adjustable. The length of the key for the
2257 encryption algorithm is always the default length used by OpenSSL.
2260 * Authentication protocol::
2261 * Encryption of network packets::
2266 @c ==================================================================
2267 @node Authentication protocol
2268 @subsection Authentication protocol
2270 @cindex authentication
2271 A new scheme for authentication in tinc has been devised, which offers some
2272 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
2282 --------------------------------------------------------------------------
2283 client <attempts connection>
2285 server <accepts connection>
2289 +-------> name of tinc daemon
2293 +-------> name of tinc daemon
2295 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
2296 \_________________________________/
2297 +-> RSAKEYLEN bits totally random string S1,
2298 encrypted with server's public RSA key
2300 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
2301 \_________________________________/
2302 +-> RSAKEYLEN bits totally random string S2,
2303 encrypted with client's public RSA key
2306 - the client will symmetrically encrypt outgoing traffic using S1
2307 - the server will symmetrically encrypt outgoing traffic using S2
2309 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
2310 \_________________________________/
2311 +-> CHALLEN bits totally random string H1
2313 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
2314 \_________________________________/
2315 +-> CHALLEN bits totally random string H2
2317 client CHAL_REPLY 816a86
2318 +-> 160 bits SHA1 of H2
2320 server CHAL_REPLY 928ffe
2321 +-> 160 bits SHA1 of H1
2323 After the correct challenge replies are received, both ends have proved
2324 their identity. Further information is exchanged.
2326 client ACK 655 123 0
2328 | +----> estimated weight
2329 +--------> listening port of client
2331 server ACK 655 321 0
2333 | +----> estimated weight
2334 +--------> listening port of server
2335 --------------------------------------------------------------------------
2338 This new scheme has several improvements, both in efficiency and security.
2340 First of all, the server sends exactly the same kind of messages over the wire
2341 as the client. The previous versions of tinc first authenticated the client,
2342 and then the server. This scheme even allows both sides to send their messages
2343 simultaneously, there is no need to wait for the other to send something first.
2344 This means that any calculations that need to be done upon sending or receiving
2345 a message can also be done in parallel. This is especially important when doing
2346 RSA encryption/decryption. Given that these calculations are the main part of
2347 the CPU time spent for the authentication, speed is improved by a factor 2.
2349 Second, only one RSA encrypted message is sent instead of two. This reduces the
2350 amount of information attackers can see (and thus use for a cryptographic
2351 attack). It also improves speed by a factor two, making the total speedup a
2354 Third, and most important:
2355 The symmetric cipher keys are exchanged first, the challenge is done
2356 afterwards. In the previous authentication scheme, because a man-in-the-middle
2357 could pass the challenge/chal_reply phase (by just copying the messages between
2358 the two real tinc daemons), but no information was exchanged that was really
2359 needed to read the rest of the messages, the challenge/chal_reply phase was of
2360 no real use. The man-in-the-middle was only stopped by the fact that only after
2361 the ACK messages were encrypted with the symmetric cipher. Potentially, it
2362 could even send it's own symmetric key to the server (if it knew the server's
2363 public key) and read some of the metadata the server would send it (it was
2364 impossible for the mitm to read actual network packets though). The new scheme
2365 however prevents this.
2367 This new scheme makes sure that first of all, symmetric keys are exchanged. The
2368 rest of the messages are then encrypted with the symmetric cipher. Then, each
2369 side can only read received messages if they have their private key. The
2370 challenge is there to let the other side know that the private key is really
2371 known, because a challenge reply can only be sent back if the challenge is
2372 decrypted correctly, and that can only be done with knowledge of the private
2375 Fourth: the first thing that is sent via the symmetric cipher encrypted
2376 connection is a totally random string, so that there is no known plaintext (for
2377 an attacker) in the beginning of the encrypted stream.
2380 @c ==================================================================
2381 @node Encryption of network packets
2382 @subsection Encryption of network packets
2385 A data packet can only be sent if the encryption key is known to both
2386 parties, and the connection is activated. If the encryption key is not
2387 known, a request is sent to the destination using the meta connection
2388 to retrieve it. The packet is stored in a queue while waiting for the
2392 The UDP packet containing the network packet from the VPN has the following layout:
2395 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
2396 \___________________/\_____/
2398 V +---> digest algorithm
2399 Encrypted with symmetric cipher
2402 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
2403 sequence number that is added in front of the actual VPN packet, to act as a unique
2404 IV for each packet and to prevent replay attacks. A message authentication code
2405 is added to the UDP packet to prevent alteration of packets. By default the
2406 first 4 bytes of the digest are used for this, but this can be changed using
2407 the MACLength configuration variable.
2409 @c ==================================================================
2410 @node Security issues
2411 @subsection Security issues
2413 In August 2000, we discovered the existence of a security hole in all versions
2414 of tinc up to and including 1.0pre2. This had to do with the way we exchanged
2415 keys. Since then, we have been working on a new authentication scheme to make
2416 tinc as secure as possible. The current version uses the OpenSSL library and
2417 uses strong authentication with RSA keys.
2419 On the 29th of December 2001, Jerome Etienne posted a security analysis of tinc
2420 1.0pre4. Due to a lack of sequence numbers and a message authentication code
2421 for each packet, an attacker could possibly disrupt certain network services or
2422 launch a denial of service attack by replaying intercepted packets. The current
2423 version adds sequence numbers and message authentication codes to prevent such
2426 On the 15th of September 2003, Peter Gutmann posted a security analysis of tinc
2427 1.0.1. He argues that the 32 bit sequence number used by tinc is not a good IV,
2428 that tinc's default length of 4 bytes for the MAC is too short, and he doesn't
2429 like tinc's use of RSA during authentication. We do not know of a security hole
2430 in this version of tinc, but tinc's security is not as strong as TLS or IPsec.
2431 We will address these issues in tinc 2.0.
2433 Cryptography is a hard thing to get right. We cannot make any
2434 guarantees. Time, review and feedback are the only things that can
2435 prove the security of any cryptographic product. If you wish to review
2436 tinc or give us feedback, you are stronly encouraged to do so.
2439 @c ==================================================================
2440 @node Platform specific information
2441 @chapter Platform specific information
2444 * Interface configuration::
2448 @c ==================================================================
2449 @node Interface configuration
2450 @section Interface configuration
2452 When configuring an interface, one normally assigns it an address and a
2453 netmask. The address uniquely identifies the host on the network attached to
2454 the interface. The netmask, combined with the address, forms a subnet. It is
2455 used to add a route to the routing table instructing the kernel to send all
2456 packets which fall into that subnet to that interface. Because all packets for
2457 the entire VPN should go to the virtual network interface used by tinc, the
2458 netmask should be such that it encompasses the entire VPN.
2462 @multitable {Darwin (Mac OS X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2464 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2465 @item Linux iproute2
2466 @tab @code{ip addr add} @var{address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2468 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2470 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2472 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2474 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2475 @item Darwin (Mac OS X)
2476 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2478 @tab @code{netsh interface ip set address} @var{interface} @code{static} @var{address} @var{netmask}
2483 @multitable {Darwin (Mac OS X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2485 @tab @code{ifconfig} @var{interface} @code{add} @var{address}@code{/}@var{prefixlength}
2487 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2489 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2491 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2493 @tab @code{ifconfig} @var{interface} @code{inet6 plumb up}
2495 @tab @code{ifconfig} @var{interface} @code{inet6 addif} @var{address} @var{address}
2496 @item Darwin (Mac OS X)
2497 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2499 @tab @code{netsh interface ipv6 add address} @var{interface} @code{static} @var{address}/@var{prefixlength}
2502 On some platforms, when running tinc in switch mode, the VPN interface must be set to tap mode with an ifconfig command:
2504 @multitable {Darwin (Mac OS X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2506 @tab @code{ifconfig} @var{interface} @code{link0}
2509 On Linux, it is possible to create a persistent tun/tap interface which will
2510 continue to exist even if tinc quit, although this is normally not required.
2511 It can be useful to set up a tun/tap interface owned by a non-root user, so
2512 tinc can be started without needing any root privileges at all.
2514 @multitable {Darwin (Mac OS X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2516 @tab @code{ip tuntap add dev} @var{interface} @code{mode} @var{tun|tap} @code{user} @var{username}
2519 @c ==================================================================
2523 In some cases it might be necessary to add more routes to the virtual network
2524 interface. There are two ways to indicate which interface a packet should go
2525 to, one is to use the name of the interface itself, another way is to specify
2526 the (local) address that is assigned to that interface (@var{local_address}). The
2527 former way is unambiguous and therefore preferable, but not all platforms
2530 Adding routes to IPv4 subnets:
2532 @multitable {Darwin (Mac OS X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2534 @tab @code{route add -net} @var{network_address} @code{netmask} @var{netmask} @var{interface}
2535 @item Linux iproute2
2536 @tab @code{ip route add} @var{network_address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2538 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2540 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2542 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2544 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address} @code{-interface}
2545 @item Darwin (Mac OS X)
2546 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @code{-interface} @var{interface}
2548 @tab @code{netsh routing ip add persistentroute} @var{network_address} @var{netmask} @var{interface} @var{local_address}
2551 Adding routes to IPv6 subnets:
2553 @multitable {Darwin (Mac OS X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2555 @tab @code{route add -A inet6} @var{network_address}@code{/}@var{prefixlength} @var{interface}
2556 @item Linux iproute2
2557 @tab @code{ip route add} @var{network_address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2559 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2561 @tab @code{route add -inet6} @var{network_address} @var{local_address} @code{-prefixlen} @var{prefixlength}
2563 @tab @code{route add -inet6} @var{network_address} @var{local_address} @code{-prefixlen} @var{prefixlength}
2565 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @var{local_address} @code{-interface}
2566 @item Darwin (Mac OS X)
2567 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @code{-interface} @var{interface}
2569 @tab @code{netsh interface ipv6 add route} @var{network address}/@var{prefixlength} @var{interface}
2573 @c ==================================================================
2579 * Contact information::
2584 @c ==================================================================
2585 @node Contact information
2586 @section Contact information
2589 Tinc's website is at @url{http://www.tinc-vpn.org/},
2590 this server is located in the Netherlands.
2593 We have an IRC channel on the FreeNode and OFTC IRC networks. Connect to
2594 @uref{http://www.freenode.net/, irc.freenode.net}
2596 @uref{http://www.oftc.net/, irc.oftc.net}
2597 and join channel #tinc.
2600 @c ==================================================================
2605 @item Ivo Timmermans (zarq)
2606 @item Guus Sliepen (guus) (@email{guus@@tinc-vpn.org})
2609 We have received a lot of valuable input from users. With their help,
2610 tinc has become the flexible and robust tool that it is today. We have
2611 composed a list of contributions, in the file called @file{THANKS} in
2612 the source distribution.
2615 @c ==================================================================
2617 @unnumbered Concept Index
2619 @c ==================================================================
2623 @c ==================================================================