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{} 1998-2012 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{} 1998-2012 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, MacOS/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 (MacOS/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 (MacOS/X) kernels
302 @subsection Configuration of Darwin (MacOS/X) kernels
304 Tinc on Darwin relies on a tunnel driver for its data acquisition from the kernel.
305 Tinc supports either the driver from @uref{http://tuntaposx.sourceforge.net/},
306 which supports both tun and tap style devices,
307 and also the driver from from @uref{http://chrisp.de/en/projects/tunnel.html}.
308 The former driver is recommended.
309 The tunnel driver must be loaded before starting tinc with the following command:
316 @c ==================================================================
317 @node Configuration of Windows
318 @subsection Configuration of Windows
320 You will need to install the latest TAP-Win32 driver from OpenVPN.
321 You can download it from @uref{http://openvpn.sourceforge.net}.
322 Using the Network Connections control panel,
323 configure the TAP-Win32 network interface in the same way as you would do from the tinc-up script,
324 as explained in the rest of the documentation.
327 @c ==================================================================
333 Before you can configure or build tinc, you need to have the OpenSSL,
334 zlib and lzo libraries installed on your system. If you try to configure tinc without
335 having them installed, configure will give you an error message, and stop.
344 @c ==================================================================
349 For all cryptography-related functions, tinc uses the functions provided
350 by the OpenSSL library.
352 If this library is not installed, you wil get an error when configuring
353 tinc for build. Support for running tinc with other cryptographic libraries
354 installed @emph{may} be added in the future.
356 You can use your operating system's package manager to install this if
357 available. Make sure you install the development AND runtime versions
360 If you have to install OpenSSL manually, you can get the source code
361 from @url{http://www.openssl.org/}. Instructions on how to configure,
362 build and install this package are included within the package. Please
363 make sure you build development and runtime libraries (which is the
366 If you installed the OpenSSL libraries from source, it may be necessary
367 to let configure know where they are, by passing configure one of the
368 --with-openssl-* parameters.
371 --with-openssl=DIR OpenSSL library and headers prefix
372 --with-openssl-include=DIR OpenSSL headers directory
373 (Default is OPENSSL_DIR/include)
374 --with-openssl-lib=DIR OpenSSL library directory
375 (Default is OPENSSL_DIR/lib)
379 @subsubheading License
382 The complete source code of tinc is covered by the GNU GPL version 2.
383 Since the license under which OpenSSL is distributed is not directly
384 compatible with the terms of the GNU GPL
385 @uref{http://www.openssl.org/support/faq.html#LEGAL2}, we
386 include an exemption to the GPL (see also the file COPYING.README) to allow
387 everyone to create a statically or dynamically linked executable:
390 This program is released under the GPL with the additional exemption
391 that compiling, linking, and/or using OpenSSL is allowed. You may
392 provide binary packages linked to the OpenSSL libraries, provided that
393 all other requirements of the GPL are met.
396 Since the LZO library used by tinc is also covered by the GPL,
397 we also present the following exemption:
400 Hereby I grant a special exception to the tinc VPN project
401 (http://www.tinc-vpn.org/) to link the LZO library with the OpenSSL library
402 (http://www.openssl.org).
404 Markus F.X.J. Oberhumer
408 @c ==================================================================
413 For the optional compression of UDP packets, tinc uses the functions provided
416 If this library is not installed, you wil get an error when running the
417 configure script. You can either install the zlib library, or disable support
418 for zlib compression by using the "--disable-zlib" option when running the
419 configure script. Note that if you disable support for zlib, the resulting
420 binary will not work correctly on VPNs where zlib compression is used.
422 You can use your operating system's package manager to install this if
423 available. Make sure you install the development AND runtime versions
426 If you have to install zlib manually, you can get the source code
427 from @url{http://www.gzip.org/zlib/}. Instructions on how to configure,
428 build and install this package are included within the package. Please
429 make sure you build development and runtime libraries (which is the
433 @c ==================================================================
438 Another form of compression is offered using the LZO library.
440 If this library is not installed, you wil get an error when running the
441 configure script. You can either install the LZO library, or disable support
442 for LZO compression by using the "--disable-lzo" option when running the
443 configure script. Note that if you disable support for LZO, the resulting
444 binary will not work correctly on VPNs where LZO compression is used.
446 You can use your operating system's package manager to install this if
447 available. Make sure you install the development AND runtime versions
450 If you have to install lzo manually, you can get the source code
451 from @url{http://www.oberhumer.com/opensource/lzo/}. Instructions on how to configure,
452 build and install this package are included within the package. Please
453 make sure you build development and runtime libraries (which is the
466 @c ==================================================================
468 @chapter Installation
470 If you use Debian, you may want to install one of the
471 precompiled packages for your system. These packages are equipped with
472 system startup scripts and sample configurations.
474 If you cannot use one of the precompiled packages, or you want to compile tinc
475 for yourself, you can use the source. The source is distributed under
476 the GNU General Public License (GPL). Download the source from the
477 @uref{http://www.tinc-vpn.org/download/, download page}, which has
478 the checksums of these files listed; you may wish to check these with
479 md5sum before continuing.
481 Tinc comes in a convenient autoconf/automake package, which you can just
482 treat the same as any other package. Which is just untar it, type
483 `./configure' and then `make'.
484 More detailed instructions are in the file @file{INSTALL}, which is
485 included in the source distribution.
488 * Building and installing tinc::
493 @c ==================================================================
494 @node Building and installing tinc
495 @section Building and installing tinc
497 Detailed instructions on configuring the source, building tinc and installing tinc
498 can be found in the file called @file{INSTALL}.
500 @cindex binary package
501 If you happen to have a binary package for tinc for your distribution,
502 you can use the package management tools of that distribution to install tinc.
503 The documentation that comes along with your distribution will tell you how to do that.
506 * Darwin (MacOS/X) build environment::
507 * Cygwin (Windows) build environment::
508 * MinGW (Windows) build environment::
512 @c ==================================================================
513 @node Darwin (MacOS/X) build environment
514 @subsection Darwin (MacOS/X) build environment
516 In order to build tinc on Darwin, you need to install the MacOS/X Developer Tools
517 from @uref{http://developer.apple.com/tools/macosxtools.html} and
518 a recent version of Fink from @uref{http://www.finkproject.org/}.
520 After installation use fink to download and install the following packages:
521 autoconf25, automake, dlcompat, m4, openssl, zlib and lzo.
523 @c ==================================================================
524 @node Cygwin (Windows) build environment
525 @subsection Cygwin (Windows) build environment
527 If Cygwin hasn't already been installed, install it directly from
528 @uref{http://www.cygwin.com/}.
530 When tinc is compiled in a Cygwin environment, it can only be run in this environment,
531 but all programs, including those started outside the Cygwin environment, will be able to use the VPN.
532 It will also support all features.
534 @c ==================================================================
535 @node MinGW (Windows) build environment
536 @subsection MinGW (Windows) build environment
538 You will need to install the MinGW environment from @uref{http://www.mingw.org}.
540 When tinc is compiled using MinGW it runs natively under Windows,
541 it is not necessary to keep MinGW installed.
543 When detaching, tinc will install itself as a service,
544 which will be restarted automatically after reboots.
547 @c ==================================================================
549 @section System files
551 Before you can run tinc, you must make sure you have all the needed
552 files on your system.
560 @c ==================================================================
562 @subsection Device files
565 Most operating systems nowadays come with the necessary device files by default,
566 or they have a mechanism to create them on demand.
568 If you use Linux and do not have udev installed,
569 you may need to create the following device file if it does not exist:
572 mknod -m 600 /dev/net/tun c 10 200
576 @c ==================================================================
578 @subsection Other files
580 @subsubheading @file{/etc/networks}
582 You may add a line to @file{/etc/networks} so that your VPN will get a
583 symbolic name. For example:
589 @subsubheading @file{/etc/services}
592 You may add this line to @file{/etc/services}. The effect is that you
593 may supply a @samp{tinc} as a valid port number to some programs. The
594 number 655 is registered with the IANA.
599 # Ivo Timmermans <ivo@@tinc-vpn.org>
614 @c ==================================================================
616 @chapter Configuration
619 * Configuration introduction::
620 * Multiple networks::
621 * How connections work::
622 * Configuration files::
623 * Generating keypairs::
624 * Network interfaces::
625 * Example configuration::
628 @c ==================================================================
629 @node Configuration introduction
630 @section Configuration introduction
632 Before actually starting to configure tinc and editing files,
633 make sure you have read this entire section so you know what to expect.
634 Then, make it clear to yourself how you want to organize your VPN:
635 What are the nodes (computers running tinc)?
636 What IP addresses/subnets do they have?
637 What is the network mask of the entire VPN?
638 Do you need special firewall rules?
639 Do you have to set up masquerading or forwarding rules?
640 Do you want to run tinc in router mode or switch mode?
641 These questions can only be answered by yourself,
642 you will not find the answers in this documentation.
643 Make sure you have an adequate understanding of networks in general.
644 @cindex Network Administrators Guide
645 A good resource on networking is the
646 @uref{http://www.tldp.org/LDP/nag2/, Linux Network Administrators Guide}.
648 If you have everything clearly pictured in your mind,
649 proceed in the following order:
650 First, generate the configuration files (@file{tinc.conf}, your host configuration file, @file{tinc-up} and perhaps @file{tinc-down}).
651 Then generate the keypairs.
652 Finally, distribute the host configuration files.
653 These steps are described in the subsections below.
656 @c ==================================================================
657 @node Multiple networks
658 @section Multiple networks
660 @cindex multiple networks
662 In order to allow you to run more than one tinc daemon on one computer,
663 for instance if your computer is part of more than one VPN,
664 you can assign a @var{netname} to your VPN.
665 It is not required if you only run one tinc daemon,
666 it doesn't even have to be the same on all the sites of your VPN,
667 but it is recommended that you choose one anyway.
669 We will asume you use a netname throughout this document.
670 This means that you call tincd with the -n argument,
671 which will assign a netname to this daemon.
673 The effect of this is that the daemon will set its configuration
674 root to @file{@value{sysconfdir}/tinc/@var{netname}/}, where @var{netname} is your argument to the -n
675 option. You'll notice that it appears in syslog as @file{tinc.@var{netname}}.
677 However, it is not strictly necessary that you call tinc with the -n
678 option. In this case, the network name would just be empty, and it will
679 be used as such. tinc now looks for files in @file{@value{sysconfdir}/tinc/}, instead of
680 @file{@value{sysconfdir}/tinc/@var{netname}/}; the configuration file should be @file{@value{sysconfdir}/tinc/tinc.conf},
681 and the host configuration files are now expected to be in @file{@value{sysconfdir}/tinc/hosts/}.
683 But it is highly recommended that you use this feature of tinc, because
684 it will be so much clearer whom your daemon talks to. Hence, we will
685 assume that you use it.
688 @c ==================================================================
689 @node How connections work
690 @section How connections work
692 When tinc starts up, it parses the command-line options and then
693 reads in the configuration file tinc.conf.
694 If it sees one or more `ConnectTo' values pointing to other tinc daemons in that file,
695 it will try to connect to those other daemons.
696 Whether this succeeds or not and whether `ConnectTo' is specified or not,
697 tinc will listen for incoming connection from other deamons.
698 If you did specify a `ConnectTo' value and the other side is not responding,
699 tinc will keep retrying.
700 This means that once started, tinc will stay running until you tell it to stop,
701 and failures to connect to other tinc daemons will not stop your tinc daemon
702 for trying again later.
703 This means you don't have to intervene if there are temporary network problems.
707 There is no real distinction between a server and a client in tinc.
708 If you wish, you can view a tinc daemon without a `ConnectTo' value as a server,
709 and one which does specify such a value as a client.
710 It does not matter if two tinc daemons have a `ConnectTo' value pointing to each other however.
713 @c ==================================================================
714 @node Configuration files
715 @section Configuration files
717 The actual configuration of the daemon is done in the file
718 @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf} and at least one other file in the directory
719 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/}.
721 These file consists of comments (lines started with a #) or assignments
728 The variable names are case insensitive, and any spaces, tabs, newlines
729 and carriage returns are ignored. Note: it is not required that you put
730 in the `=' sign, but doing so improves readability. If you leave it
731 out, remember to replace it with at least one space character.
733 The server configuration is complemented with host specific configuration (see
734 the next section). Although all host configuration options for the local node
735 listed in this document can also be put in
736 @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf}, it is recommended to
737 put host specific configuration options in the host configuration file, as this
738 makes it easy to exchange with other nodes.
740 In this section all valid variables are listed in alphabetical order.
741 The default value is given between parentheses,
742 other comments are between square brackets.
745 * Main configuration variables::
746 * Host configuration variables::
752 @c ==================================================================
753 @node Main configuration variables
754 @subsection Main configuration variables
757 @cindex AddressFamily
758 @item AddressFamily = <ipv4|ipv6|any> (any)
759 This option affects the address family of listening and outgoing sockets.
760 If any is selected, then depending on the operating system
761 both IPv4 and IPv6 or just IPv6 listening sockets will be created.
763 @cindex BindToAddress
764 @item BindToAddress = <@var{address}> [<@var{port}>] [experimental]
765 If your computer has more than one IPv4 or IPv6 address, tinc
766 will by default listen on all of them for incoming connections.
767 Multiple BindToAddress variables may be specified,
768 in which case listening sockets for each specified address are made.
770 If no @var{port} is specified, the socket will be bound to the port specified by the Port option,
771 or to port 655 if neither is given.
772 To only bind to a specific port but not to a specific address, use "*" for the @var{address}.
774 This option may not work on all platforms.
776 @cindex BindToInterface
777 @item BindToInterface = <@var{interface}> [experimental]
778 If you have more than one network interface in your computer, tinc will
779 by default listen on all of them for incoming connections. It is
780 possible to bind tinc to a single interface like eth0 or ppp0 with this
783 This option may not work on all platforms.
786 @item Broadcast = <no | mst | direct> (mst) [experimental]
787 This option selects the way broadcast packets are sent to other daemons.
788 @emph{NOTE: all nodes in a VPN must use the same Broadcast mode, otherwise routing loops can form.}
792 Broadcast packets are never sent to other nodes.
795 Broadcast packets are sent and forwarded via the VPN's Minimum Spanning Tree.
796 This ensures broadcast packets reach all nodes.
799 Broadcast packets are sent directly to all nodes that can be reached directly.
800 Broadcast packets received from other nodes are never forwarded.
801 If the IndirectData option is also set, broadcast packets will only be sent to nodes which we have a meta connection to.
805 @item ConnectTo = <@var{name}>
806 Specifies which other tinc daemon to connect to on startup.
807 Multiple ConnectTo variables may be specified,
808 in which case outgoing connections to each specified tinc daemon are made.
809 The names should be known to this tinc daemon
810 (i.e., there should be a host configuration file for the name on the ConnectTo line).
812 If you don't specify a host with ConnectTo,
813 tinc won't try to connect to other daemons at all,
814 and will instead just listen for incoming connections.
817 @item DecrementTTL = <yes | no> (no) [experimental]
818 When enabled, tinc will decrement the Time To Live field in IPv4 packets, or the Hop Limit field in IPv6 packets,
819 before forwarding a received packet to the virtual network device or to another node,
820 and will drop packets that have a TTL value of zero,
821 in which case it will send an ICMP Time Exceeded packet back.
823 Do not use this option if you use switch mode and want to use IPv6.
826 @item Device = <@var{device}> (@file{/dev/tap0}, @file{/dev/net/tun} or other depending on platform)
827 The virtual network device to use.
828 Tinc will automatically detect what kind of device it is.
829 Note that you can only use one device per daemon.
830 Under Windows, use @var{Interface} instead of @var{Device}.
831 Note that you can only use one device per daemon.
832 See also @ref{Device files}.
835 @item DeviceType = <@var{type}> (platform dependent)
836 The type of the virtual network device.
837 Tinc will normally automatically select the right type of tun/tap interface, and this option should not be used.
838 However, this option can be used to select one of the special interface types, if support for them is compiled in.
843 Use a dummy interface.
844 No packets are ever read or written to a virtual network device.
845 Useful for testing, or when setting up a node that only forwards packets for other nodes.
849 Open a raw socket, and bind it to a pre-existing
850 @var{Interface} (eth0 by default).
851 All packets are read from this interface.
852 Packets received for the local node are written to the raw socket.
853 However, at least on Linux, the operating system does not process IP packets destined for the local host.
857 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}.
858 Packets are read from and written to this multicast socket.
859 This can be used to connect to UML, QEMU or KVM instances listening on the same multicast address.
860 Do NOT connect multiple tinc daemons to the same multicast address, this will very likely cause routing loops.
861 Also note that this can cause decrypted VPN packets to be sent out on a real network if misconfigured.
864 @item uml (not compiled in by default)
865 Create a UNIX socket with the filename specified by
866 @var{Device}, or @file{@value{localstatedir}/run/@var{netname}.umlsocket}
868 Tinc will wait for a User Mode Linux instance to connect to this socket.
871 @item vde (not compiled in by default)
872 Uses the libvdeplug library to connect to a Virtual Distributed Ethernet switch,
873 using the UNIX socket specified by
874 @var{Device}, or @file{@value{localstatedir}/run/vde.ctl}
878 Also, in case tinc does not seem to correctly interpret packets received from the virtual network device,
879 it can be used to change the way packets are interpreted:
882 @item tun (BSD and Linux)
884 Depending on the platform, this can either be with or without an address family header (see below).
887 @item tunnohead (BSD)
888 Set type to tun without an address family header.
889 Tinc will expect packets read from the virtual network device to start with an IP header.
890 On some platforms IPv6 packets cannot be read from or written to the device in this mode.
893 @item tunifhead (BSD)
894 Set type to tun with an address family header.
895 Tinc will expect packets read from the virtual network device
896 to start with a four byte header containing the address family,
897 followed by an IP header.
898 This mode should support both IPv4 and IPv6 packets.
900 @item tap (BSD and Linux)
902 Tinc will expect packets read from the virtual network device
903 to start with an Ethernet header.
907 @item DirectOnly = <yes|no> (no) [experimental]
908 When this option is enabled, packets that cannot be sent directly to the destination node,
909 but which would have to be forwarded by an intermediate node, are dropped instead.
910 When combined with the IndirectData option,
911 packets for nodes for which we do not have a meta connection with are also dropped.
914 @item Forwarding = <off|internal|kernel> (internal) [experimental]
915 This option selects the way indirect packets are forwarded.
919 Incoming packets that are not meant for the local node,
920 but which should be forwarded to another node, are dropped.
923 Incoming packets that are meant for another node are forwarded by tinc internally.
925 This is the default mode, and unless you really know you need another forwarding mode, don't change it.
928 Incoming packets are always sent to the TUN/TAP device, even if the packets are not for the local node.
929 This is less efficient, but allows the kernel to apply its routing and firewall rules on them,
930 and can also help debugging.
933 @cindex GraphDumpFile
934 @item GraphDumpFile = <@var{filename}> [experimental]
935 If this option is present,
936 tinc will dump the current network graph to the file @var{filename}
937 every minute, unless there were no changes to the graph.
938 The file is in a format that can be read by graphviz tools.
939 If @var{filename} starts with a pipe symbol |,
940 then the rest of the filename is interpreted as a shell command
941 that is executed, the graph is then sent to stdin.
944 @item Hostnames = <yes|no> (no)
945 This option selects whether IP addresses (both real and on the VPN)
946 should be resolved. Since DNS lookups are blocking, it might affect
947 tinc's efficiency, even stopping the daemon for a few seconds everytime
948 it does a lookup if your DNS server is not responding.
950 This does not affect resolving hostnames to IP addresses from the
951 configuration file, but whether hostnames should be resolved while logging.
954 @item Interface = <@var{interface}>
955 Defines the name of the interface corresponding to the virtual network device.
956 Depending on the operating system and the type of device this may or may not actually set the name of the interface.
957 Under Windows, this variable is used to select which network interface will be used.
958 If you specified a Device, this variable is almost always already correctly set.
960 @cindex LocalDiscovery
961 @item LocalDiscovery = <yes | no> (no) [experimental]
962 When enabled, tinc will try to detect peers that are on the same local network.
963 This will allow direct communication using LAN addresses, even if both peers are behind a NAT
964 and they only ConnectTo a third node outside the NAT,
965 which normally would prevent the peers from learning each other's LAN address.
967 Currently, local discovery is implemented by sending broadcast packets to the LAN during path MTU discovery.
968 This feature may not work in all possible situations.
971 @item Mode = <router|switch|hub> (router)
972 This option selects the way packets are routed to other daemons.
978 variables in the host configuration files will be used to form a routing table.
979 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
981 This is the default mode, and unless you really know you need another mode, don't change it.
985 In this mode the MAC addresses of the packets on the VPN will be used to
986 dynamically create a routing table just like an Ethernet switch does.
987 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
988 at the cost of frequent broadcast ARP requests and routing table updates.
990 This mode is primarily useful if you want to bridge Ethernet segments.
994 This mode is almost the same as the switch mode, but instead
995 every packet will be broadcast to the other daemons
996 while no routing table is managed.
1000 @item KeyExpire = <@var{seconds}> (3600)
1001 This option controls the time the encryption keys used to encrypt the data
1002 are valid. It is common practice to change keys at regular intervals to
1003 make it even harder for crackers, even though it is thought to be nearly
1004 impossible to crack a single key.
1007 @item MACExpire = <@var{seconds}> (600)
1008 This option controls the amount of time MAC addresses are kept before they are removed.
1009 This only has effect when Mode is set to "switch".
1012 @item Name = <@var{name}> [required]
1013 This is a symbolic name for this connection.
1014 The name should consist only of alfanumeric and underscore characters (a-z, A-Z, 0-9 and _).
1016 If Name starts with a $, then the contents of the environment variable that follows will be used.
1017 In that case, invalid characters will be converted to underscores.
1018 If Name is $HOST, but no such environment variable exist,
1019 the hostname will be read using the gethostnname() system call.
1021 @cindex PingInterval
1022 @item PingInterval = <@var{seconds}> (60)
1023 The number of seconds of inactivity that tinc will wait before sending a
1024 probe to the other end.
1027 @item PingTimeout = <@var{seconds}> (5)
1028 The number of seconds to wait for a response to pings or to allow meta
1029 connections to block. If the other end doesn't respond within this time,
1030 the connection is terminated, and the others will be notified of this.
1032 @cindex PriorityInheritance
1033 @item PriorityInheritance = <yes|no> (no) [experimental]
1034 When this option is enabled the value of the TOS field of tunneled IPv4 packets
1035 will be inherited by the UDP packets that are sent out.
1038 @item PrivateKey = <@var{key}> [obsolete]
1039 This is the RSA private key for tinc. However, for safety reasons it is
1040 advised to store private keys of any kind in separate files. This prevents
1041 accidental eavesdropping if you are editting the configuration file.
1043 @cindex PrivateKeyFile
1044 @item PrivateKeyFile = <@var{path}> (@file{@value{sysconfdir}/tinc/@var{netname}/rsa_key.priv})
1045 This is the full path name of the RSA private key file that was
1046 generated by @samp{tincd --generate-keys}. It must be a full path, not a
1049 Note that there must be exactly one of PrivateKey
1051 specified in the configuration file.
1053 @cindex ProcessPriority
1054 @item ProcessPriority = <low|normal|high>
1055 When this option is used the priority of the tincd process will be adjusted.
1056 Increasing the priority may help to reduce latency and packet loss on the VPN.
1059 @item Proxy = socks4 | socks4 | http | exec @var{...} [experimental]
1060 Use a proxy when making outgoing connections.
1061 The following proxy types are currently supported:
1065 @item socks4 <@var{address}> <@var{port}> [<@var{username}>]
1066 Connects to the proxy using the SOCKS version 4 protocol.
1067 Optionally, a @var{username} can be supplied which will be passed on to the proxy server.
1070 @item socks4 <@var{address}> <@var{port}> [<@var{username}> <@var{password}>]
1071 Connect to the proxy using the SOCKS version 5 protocol.
1072 If a @var{username} and @var{password} are given, basic username/password authentication will be used,
1073 otherwise no authentication will be used.
1076 @item http <@var{address}> <@var{port}>
1077 Connects to the proxy and sends a HTTP CONNECT request.
1080 @item exec <@var{command}>
1081 Executes the given command which should set up the outgoing connection.
1082 The environment variables @env{NAME}, @env{NODE}, @env{REMOTEADDRES} and @env{REMOTEPORT} are available.
1085 @cindex ReplayWindow
1086 @item ReplayWindow = <bytes> (16)
1087 This is the size of the replay tracking window for each remote node, in bytes.
1088 The window is a bitfield which tracks 1 packet per bit, so for example
1089 the default setting of 16 will track up to 128 packets in the window. In high
1090 bandwidth scenarios, setting this to a higher value can reduce packet loss from
1091 the interaction of replay tracking with underlying real packet loss and/or
1092 reordering. Setting this to zero will disable replay tracking completely and
1093 pass all traffic, but leaves tinc vulnerable to replay-based attacks on your
1097 @cindex StrictSubnets
1098 @item StrictSubnets <yes|no> (no) [experimental]
1099 When this option is enabled tinc will only use Subnet statements which are
1100 present in the host config files in the local
1101 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
1103 @cindex TunnelServer
1104 @item TunnelServer = <yes|no> (no) [experimental]
1105 When this option is enabled tinc will no longer forward information between other tinc daemons,
1106 and will only allow connections with nodes for which host config files are present in the local
1107 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
1108 Setting this options also implicitly sets StrictSubnets.
1111 @item UDPRcvBuf = <bytes> (OS default)
1112 Sets the socket receive buffer size for the UDP socket, in bytes.
1113 If unset, the default buffer size will be used by the operating system.
1116 @item UDPSndBuf = <bytes> Pq OS default
1117 Sets the socket send buffer size for the UDP socket, in bytes.
1118 If unset, the default buffer size will be used by the operating system.
1123 @c ==================================================================
1124 @node Host configuration variables
1125 @subsection Host configuration variables
1129 @item Address = <@var{IP address}|@var{hostname}> [<port>] [recommended]
1130 This variable is only required if you want to connect to this host. It
1131 must resolve to the external IP address where the host can be reached,
1132 not the one that is internal to the VPN.
1133 If no port is specified, the default Port is used.
1136 @item Cipher = <@var{cipher}> (blowfish)
1137 The symmetric cipher algorithm used to encrypt UDP packets.
1138 Any cipher supported by OpenSSL is recognized.
1139 Furthermore, specifying "none" will turn off packet encryption.
1140 It is best to use only those ciphers which support CBC mode.
1143 @item ClampMSS = <yes|no> (yes)
1144 This option specifies whether tinc should clamp the maximum segment size (MSS)
1145 of TCP packets to the path MTU. This helps in situations where ICMP
1146 Fragmentation Needed or Packet too Big messages are dropped by firewalls.
1149 @item Compression = <@var{level}> (0)
1150 This option sets the level of compression used for UDP packets.
1151 Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
1152 10 (fast lzo) and 11 (best lzo).
1155 @item Digest = <@var{digest}> (sha1)
1156 The digest algorithm used to authenticate UDP packets.
1157 Any digest supported by OpenSSL is recognized.
1158 Furthermore, specifying "none" will turn off packet authentication.
1160 @cindex IndirectData
1161 @item IndirectData = <yes|no> (no)
1162 This option specifies whether other tinc daemons besides the one you
1163 specified with ConnectTo can make a direct connection to you. This is
1164 especially useful if you are behind a firewall and it is impossible to
1165 make a connection from the outside to your tinc daemon. Otherwise, it
1166 is best to leave this option out or set it to no.
1169 @item MACLength = <@var{bytes}> (4)
1170 The length of the message authentication code used to authenticate UDP packets.
1171 Can be anything from 0
1172 up to the length of the digest produced by the digest algorithm.
1175 @item PMTU = <@var{mtu}> (1514)
1176 This option controls the initial path MTU to this node.
1178 @cindex PMTUDiscovery
1179 @item PMTUDiscovery = <yes|no> (yes)
1180 When this option is enabled, tinc will try to discover the path MTU to this node.
1181 After the path MTU has been discovered, it will be enforced on the VPN.
1184 @item Port = <@var{port}> (655)
1185 This is the port this tinc daemon listens on.
1186 You can use decimal portnumbers or symbolic names (as listed in @file{/etc/services}).
1189 @item PublicKey = <@var{key}> [obsolete]
1190 This is the RSA public key for this host.
1192 @cindex PublicKeyFile
1193 @item PublicKeyFile = <@var{path}> [obsolete]
1194 This is the full path name of the RSA public key file that was generated
1195 by @samp{tincd --generate-keys}. It must be a full path, not a relative
1199 From version 1.0pre4 on tinc will store the public key directly into the
1200 host configuration file in PEM format, the above two options then are not
1201 necessary. Either the PEM format is used, or exactly
1202 @strong{one of the above two options} must be specified
1203 in each host configuration file, if you want to be able to establish a
1204 connection with that host.
1207 @item Subnet = <@var{address}[/@var{prefixlength}[#@var{weight}]]>
1208 The subnet which this tinc daemon will serve.
1209 Tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
1210 If the packet matches a subnet,
1211 it will be sent to the daemon who has this subnet in his host configuration file.
1212 Multiple subnet lines can be specified for each daemon.
1214 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1215 in which case a subnet consisting of only that single address is assumed,
1216 or they can be a IPv4 or IPv6 network address with a prefixlength.
1217 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1218 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1219 Note that subnets like 192.168.1.1/24 are invalid!
1220 Read a networking HOWTO/FAQ/guide if you don't understand this.
1221 IPv6 subnets are notated like fec0:0:0:1::/64.
1222 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1224 @cindex CIDR notation
1225 Prefixlength is the number of bits set to 1 in the netmask part; for
1226 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1227 /22. This conforms to standard CIDR notation as described in
1228 @uref{http://www.ietf.org/rfc/rfc1519.txt, RFC1519}
1230 @cindex Subnet weight
1231 A Subnet can be given a weight to indicate its priority over identical Subnets
1232 owned by different nodes. The default weight is 10. Lower values indicate
1233 higher priority. Packets will be sent to the node with the highest priority,
1234 unless that node is not reachable, in which case the node with the next highest
1235 priority will be tried, and so on.
1238 @item TCPonly = <yes|no> (no) [deprecated]
1239 If this variable is set to yes, then the packets are tunnelled over a
1240 TCP connection instead of a UDP connection. This is especially useful
1241 for those who want to run a tinc daemon from behind a masquerading
1242 firewall, or if UDP packet routing is disabled somehow.
1243 Setting this options also implicitly sets IndirectData.
1245 Since version 1.0.10, tinc will automatically detect whether communication via
1246 UDP is possible or not.
1250 @c ==================================================================
1255 Apart from reading the server and host configuration files,
1256 tinc can also run scripts at certain moments.
1257 Under Windows (not Cygwin), the scripts should have the extension .bat.
1261 @item @value{sysconfdir}/tinc/@var{netname}/tinc-up
1262 This is the most important script.
1263 If it is present it will be executed right after the tinc daemon has been
1264 started and has connected to the virtual network device.
1265 It should be used to set up the corresponding network interface,
1266 but can also be used to start other things.
1267 Under Windows you can use the Network Connections control panel instead of creating this script.
1270 @item @value{sysconfdir}/tinc/@var{netname}/tinc-down
1271 This script is started right before the tinc daemon quits.
1273 @item @value{sysconfdir}/tinc/@var{netname}/hosts/@var{host}-up
1274 This script is started when the tinc daemon with name @var{host} becomes reachable.
1276 @item @value{sysconfdir}/tinc/@var{netname}/hosts/@var{host}-down
1277 This script is started when the tinc daemon with name @var{host} becomes unreachable.
1279 @item @value{sysconfdir}/tinc/@var{netname}/host-up
1280 This script is started when any host becomes reachable.
1282 @item @value{sysconfdir}/tinc/@var{netname}/host-down
1283 This script is started when any host becomes unreachable.
1285 @item @value{sysconfdir}/tinc/@var{netname}/subnet-up
1286 This script is started when a Subnet becomes reachable.
1287 The Subnet and the node it belongs to are passed in environment variables.
1289 @item @value{sysconfdir}/tinc/@var{netname}/subnet-down
1290 This script is started when a Subnet becomes unreachable.
1293 @cindex environment variables
1294 The scripts are started without command line arguments,
1295 but can make use of certain environment variables.
1296 Under UNIX like operating systems the names of environment variables must be preceded by a $ in scripts.
1297 Under Windows, in @file{.bat} files, they have to be put between % signs.
1302 If a netname was specified, this environment variable contains it.
1306 Contains the name of this tinc daemon.
1310 Contains the name of the virtual network device that tinc uses.
1314 Contains the name of the virtual network interface that tinc uses.
1315 This should be used for commands like ifconfig.
1319 When a host becomes (un)reachable, this is set to its name.
1320 If a subnet becomes (un)reachable, this is set to the owner of that subnet.
1322 @cindex REMOTEADDRESS
1324 When a host becomes (un)reachable, this is set to its real address.
1328 When a host becomes (un)reachable,
1329 this is set to the port number it uses for communication with other tinc daemons.
1333 When a subnet becomes (un)reachable, this is set to the subnet.
1337 When a subnet becomes (un)reachable, this is set to the subnet weight.
1342 @c ==================================================================
1343 @node How to configure
1344 @subsection How to configure
1346 @subsubheading Step 1. Creating the main configuration file
1348 The main configuration file will be called @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf}.
1349 Adapt the following example to create a basic configuration file:
1352 Name = @var{yourname}
1353 Device = @file{/dev/tap0}
1356 Then, if you know to which other tinc daemon(s) yours is going to connect,
1357 add `ConnectTo' values.
1359 @subsubheading Step 2. Creating your host configuration file
1361 If you added a line containing `Name = yourname' in the main configuarion file,
1362 you will need to create a host configuration file @file{@value{sysconfdir}/tinc/@var{netname}/hosts/yourname}.
1363 Adapt the following example to create a host configuration file:
1366 Address = your.real.hostname.org
1367 Subnet = 192.168.1.0/24
1370 You can also use an IP address instead of a hostname.
1371 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1372 If you have multiple address ranges you can specify more than one `Subnet'.
1373 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).
1376 @c ==================================================================
1377 @node Generating keypairs
1378 @section Generating keypairs
1380 @cindex key generation
1381 Now that you have already created the main configuration file and your host configuration file,
1382 you can easily create a public/private keypair by entering the following command:
1385 tincd -n @var{netname} -K
1388 Tinc will generate a public and a private key and ask you where to put them.
1389 Just press enter to accept the defaults.
1392 @c ==================================================================
1393 @node Network interfaces
1394 @section Network interfaces
1396 Before tinc can start transmitting data over the tunnel, it must
1397 set up the virtual network interface.
1399 First, decide which IP addresses you want to have associated with these
1400 devices, and what network mask they must have.
1402 Tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1403 which will also create a network interface called something like @samp{tun0}, @samp{tap0}.
1404 If you are using the Linux tun/tap driver, the network interface will by default have the same name as the @var{netname}.
1405 Under Windows you can change the name of the network interface from the Network Connections control panel.
1408 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1409 to a script named @file{@value{sysconfdir}/tinc/@var{netname}/tinc-up}.
1410 When tinc starts, this script will be executed. When tinc exits, it will execute the script named
1411 @file{@value{sysconfdir}/tinc/@var{netname}/tinc-down}, but normally you don't need to create that script.
1413 An example @file{tinc-up} script:
1417 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1420 This script gives the interface an IP address and a netmask.
1421 The kernel will also automatically add a route to this interface, so normally you don't need
1422 to add route commands to the @file{tinc-up} script.
1423 The kernel will also bring the interface up after this command.
1425 The netmask is the mask of the @emph{entire} VPN network, not just your
1428 The exact syntax of the ifconfig and route commands differs from platform to platform.
1429 You can look up the commands for setting addresses and adding routes in @ref{Platform specific information},
1430 but it is best to consult the manpages of those utilities on your platform.
1433 @c ==================================================================
1434 @node Example configuration
1435 @section Example configuration
1439 Imagine the following situation. Branch A of our example `company' wants to connect
1440 three branch offices in B, C and D using the Internet. All four offices
1441 have a 24/7 connection to the Internet.
1443 A is going to serve as the center of the network. B and C will connect
1444 to A, and D will connect to C. Each office will be assigned their own IP
1448 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1449 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1450 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1451 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1454 Here, ``gateway'' is the VPN IP address of the machine that is running the
1455 tincd, and ``internet IP'' is the IP address of the firewall, which does not
1456 need to run tincd, but it must do a port forwarding of TCP and UDP on port
1457 655 (unless otherwise configured).
1459 In this example, it is assumed that eth0 is the interface that points to
1460 the inner (physical) LAN of the office, although this could also be the
1461 same as the interface that leads to the Internet. The configuration of
1462 the real interface is also shown as a comment, to give you an idea of
1463 how these example host is set up. All branches use the netname `company'
1464 for this particular VPN.
1466 @subsubheading For Branch A
1468 @emph{BranchA} would be configured like this:
1470 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1473 # Real interface of internal network:
1474 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0
1476 ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
1479 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1486 On all hosts, @file{@value{sysconfdir}/tinc/company/hosts/BranchA} contains:
1489 Subnet = 10.1.0.0/16
1492 -----BEGIN RSA PUBLIC KEY-----
1494 -----END RSA PUBLIC KEY-----
1497 Note that the IP addresses of eth0 and tap0 are the same.
1498 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1499 It is in fact recommended to give both real internal network interfaces and tap interfaces the same IP address,
1500 since that will make things a lot easier to remember and set up.
1503 @subsubheading For Branch B
1505 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1508 # Real interface of internal network:
1509 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0
1511 ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
1514 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1521 Note here that the internal address (on eth0) doesn't have to be the
1522 same as on the tap0 device. Also, ConnectTo is given so that this node will
1523 always try to connect to BranchA.
1525 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchB}:
1528 Subnet = 10.2.0.0/16
1531 -----BEGIN RSA PUBLIC KEY-----
1533 -----END RSA PUBLIC KEY-----
1537 @subsubheading For Branch C
1539 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1542 # Real interface of internal network:
1543 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0
1545 ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
1548 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1556 C already has another daemon that runs on port 655, so they have to
1557 reserve another port for tinc. It knows the portnumber it has to listen on
1558 from it's own host configuration file.
1560 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchC}:
1564 Subnet = 10.3.0.0/16
1567 -----BEGIN RSA PUBLIC KEY-----
1569 -----END RSA PUBLIC KEY-----
1573 @subsubheading For Branch D
1575 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1578 # Real interface of internal network:
1579 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0
1581 ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
1584 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1589 Device = /dev/net/tun
1592 D will be connecting to C, which has a tincd running for this network on
1593 port 2000. It knows the port number from the host configuration file.
1594 Also note that since D uses the tun/tap driver, the network interface
1595 will not be called `tun' or `tap0' or something like that, but will
1596 have the same name as netname.
1598 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchD}:
1601 Subnet = 10.4.0.0/16
1604 -----BEGIN RSA PUBLIC KEY-----
1606 -----END RSA PUBLIC KEY-----
1609 @subsubheading Key files
1611 A, B, C and D all have generated a public/private keypair with the following command:
1617 The private key is stored in @file{@value{sysconfdir}/tinc/company/rsa_key.priv},
1618 the public key is put into the host configuration file in the @file{@value{sysconfdir}/tinc/company/hosts/} directory.
1619 During key generation, tinc automatically guesses the right filenames based on the -n option and
1620 the Name directive in the @file{tinc.conf} file (if it is available).
1622 @subsubheading Starting
1624 After each branch has finished configuration and they have distributed
1625 the host configuration files amongst them, they can start their tinc daemons.
1626 They don't necessarily have to wait for the other branches to have started
1627 their daemons, tinc will try connecting until they are available.
1630 @c ==================================================================
1632 @chapter Running tinc
1634 If everything else is done, you can start tinc by typing the following command:
1637 tincd -n @var{netname}
1641 Tinc will detach from the terminal and continue to run in the background like a good daemon.
1642 If there are any problems however you can try to increase the debug level
1643 and look in the syslog to find out what the problems are.
1649 * Solving problems::
1651 * Sending bug reports::
1655 @c ==================================================================
1656 @node Runtime options
1657 @section Runtime options
1659 Besides the settings in the configuration file, tinc also accepts some
1660 command line options.
1662 @cindex command line
1663 @cindex runtime options
1667 @item -c, --config=@var{path}
1668 Read configuration options from the directory @var{path}. The default is
1669 @file{@value{sysconfdir}/tinc/@var{netname}/}.
1671 @item -D, --no-detach
1672 Don't fork and detach.
1673 This will also disable the automatic restart mechanism for fatal errors.
1676 @item -d, --debug=@var{level}
1677 Set debug level to @var{level}. The higher the debug level, the more gets
1678 logged. Everything goes via syslog.
1680 @item -k, --kill[=@var{signal}]
1681 Attempt to kill a running tincd (optionally with the specified @var{signal} instead of SIGTERM) and exit.
1682 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1683 Under native Windows the optional argument is ignored,
1684 the service will always be stopped and removed.
1686 @item -n, --net=@var{netname}
1687 Use configuration for net @var{netname}.
1688 This will let tinc read all configuration files from
1689 @file{@value{sysconfdir}/tinc/@var{netname}/}.
1690 Specifying . for @var{netname} is the same as not specifying any @var{netname}.
1691 @xref{Multiple networks}.
1693 @item -K, --generate-keys[=@var{bits}]
1694 Generate public/private keypair of @var{bits} length. If @var{bits} is not specified,
1695 2048 is the default. tinc will ask where you want to store the files,
1696 but will default to the configuration directory (you can use the -c or -n option
1697 in combination with -K). After that, tinc will quit.
1699 @item -o, --option=[@var{HOST}.]@var{KEY}=@var{VALUE}
1700 Without specifying a @var{HOST}, this will set server configuration variable @var{KEY} to @var{VALUE}.
1701 If specified as @var{HOST}.@var{KEY}=@var{VALUE},
1702 this will set the host configuration variable @var{KEY} of the host named @var{HOST} to @var{VALUE}.
1703 This option can be used more than once to specify multiple configuration variables.
1706 Lock tinc into main memory.
1707 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1709 @item --logfile[=@var{file}]
1710 Write log entries to a file instead of to the system logging facility.
1711 If @var{file} is omitted, the default is @file{@value{localstatedir}/log/tinc.@var{netname}.log}.
1713 @item --pidfile=@var{file}
1714 Write PID to @var{file} instead of @file{@value{localstatedir}/run/tinc.@var{netname}.pid}.
1716 @item --bypass-security
1717 Disables encryption and authentication.
1718 Only useful for debugging.
1721 Change process root directory to the directory where the config file is
1722 located (@file{@value{sysconfdir}/tinc/@var{netname}/} as determined by
1723 -n/--net option or as given by -c/--config option), for added security.
1724 The chroot is performed after all the initialization is done, after
1725 writing pid files and opening network sockets.
1727 Note that this option alone does not do any good without -U/--user, below.
1729 Note also that tinc can't run scripts anymore (such as tinc-down or host-up),
1730 unless it's setup to be runnable inside chroot environment.
1732 @item -U, --user=@var{user}
1733 Switch to the given @var{user} after initialization, at the same time as
1734 chroot is performed (see --chroot above). With this option tinc drops
1735 privileges, for added security.
1738 Display a short reminder of these runtime options and terminate.
1741 Output version information and exit.
1745 @c ==================================================================
1750 You can also send the following signals to a running tincd process:
1756 Forces tinc to try to connect to all uplinks immediately.
1757 Usually tinc attempts to do this itself,
1758 but increases the time it waits between the attempts each time it failed,
1759 and if tinc didn't succeed to connect to an uplink the first time after it started,
1760 it defaults to the maximum time of 15 minutes.
1763 Partially rereads configuration files.
1764 Connections to hosts whose host config file are removed are closed.
1765 New outgoing connections specified in @file{tinc.conf} will be made.
1766 If the --logfile option is used, this will also close and reopen the log file,
1767 useful when log rotation is used.
1770 Temporarily increases debug level to 5.
1771 Send this signal again to revert to the original level.
1774 Dumps the connection list to syslog.
1777 Dumps virtual network device statistics, all known nodes, edges and subnets to syslog.
1780 Purges all information remembered about unreachable nodes.
1784 @c ==================================================================
1786 @section Debug levels
1788 @cindex debug levels
1789 The tinc daemon can send a lot of messages to the syslog.
1790 The higher the debug level, the more messages it will log.
1791 Each level inherits all messages of the previous level:
1797 This will log a message indicating tinc has started along with a version number.
1798 It will also log any serious error.
1801 This will log all connections that are made with other tinc daemons.
1804 This will log status and error messages from scripts and other tinc daemons.
1807 This will log all requests that are exchanged with other tinc daemons. These include
1808 authentication, key exchange and connection list updates.
1811 This will log a copy of everything received on the meta socket.
1814 This will log all network traffic over the virtual private network.
1818 @c ==================================================================
1819 @node Solving problems
1820 @section Solving problems
1822 If tinc starts without problems, but if the VPN doesn't work, you will have to find the cause of the problem.
1823 The first thing to do is to start tinc with a high debug level in the foreground,
1824 so you can directly see everything tinc logs:
1827 tincd -n @var{netname} -d5 -D
1830 If tinc does not log any error messages, then you might want to check the following things:
1833 @item @file{tinc-up} script
1834 Does this script contain the right commands?
1835 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.
1838 Does the Subnet (or Subnets) in the host configuration file of this host match the portion of the VPN that belongs to this host?
1840 @item Firewalls and NATs
1841 Do you have a firewall or a NAT device (a masquerading firewall or perhaps an ADSL router that performs masquerading)?
1842 If so, check that it allows TCP and UDP traffic on port 655.
1843 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.
1844 You can add @samp{TCPOnly = yes} to your host config file to force tinc to only use a single TCP connection,
1845 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.
1850 @c ==================================================================
1851 @node Error messages
1852 @section Error messages
1854 What follows is a list of the most common error messages you might find in the logs.
1855 Some of them will only be visible if the debug level is high enough.
1858 @item Could not open /dev/tap0: No such device
1861 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1862 @item You forgot to compile `Netlink device emulation' in the kernel.
1865 @item Can't write to /dev/net/tun: No such device
1868 @item You forgot to `modprobe tun'.
1869 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1870 @item The tun device is located somewhere else in @file{/dev/}.
1873 @item Network address and prefix length do not match!
1876 @item The Subnet field must contain a @emph{network} address, trailing bits should be 0.
1877 @item If you only want to use one IP address, set the netmask to /32.
1880 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1883 @item You forgot to create a public/private keypair.
1884 @item Specify the complete pathname to the private key file with the @samp{PrivateKeyFile} option.
1887 @item Warning: insecure file permissions for RSA private key file `rsa_key.priv'!
1890 @item The private key file is readable by users other than root.
1891 Use chmod to correct the file permissions.
1894 @item Creating metasocket failed: Address family not supported
1897 @item By default tinc tries to create both IPv4 and IPv6 sockets.
1898 On some platforms this might not be implemented.
1899 If the logs show @samp{Ready} later on, then at least one metasocket was created,
1900 and you can ignore this message.
1901 You can add @samp{AddressFamily = ipv4} to @file{tinc.conf} to prevent this from happening.
1904 @item Cannot route packet: unknown IPv4 destination 1.2.3.4
1907 @item You try to send traffic to a host on the VPN for which no Subnet is known.
1908 @item If it is a broadcast address (ending in .255), it probably is a samba server or a Windows host sending broadcast packets.
1912 @item Cannot route packet: ARP request for unknown address 1.2.3.4
1915 @item You try to send traffic to a host on the VPN for which no Subnet is known.
1918 @item Packet with destination 1.2.3.4 is looping back to us!
1921 @item Something is not configured right. Packets are being sent out to the
1922 virtual network device, but according to the Subnet directives in your host configuration
1923 file, those packets should go to your own host. Most common mistake is that
1924 you have a Subnet line in your host configuration file with a prefix length which is
1925 just as large as the prefix of the virtual network interface. The latter should in almost all
1926 cases be larger. Rethink your configuration.
1927 Note that you will only see this message if you specified a debug
1928 level of 5 or higher!
1929 @item Chances are that a @samp{Subnet = ...} line in the host configuration file of this tinc daemon is wrong.
1930 Change it to a subnet that is accepted locally by another interface,
1931 or if that is not the case, try changing the prefix length into /32.
1934 @item Node foo (1.2.3.4) is not reachable
1937 @item Node foo does not have a connection anymore, its tinc daemon is not running or its connection to the Internet is broken.
1940 @item Received UDP packet from unknown source 1.2.3.4 (port 12345)
1943 @item If you see this only sporadically, it is harmless and caused by a node sending packets using an old key.
1946 @item Got bad/bogus/unauthorized REQUEST from foo (1.2.3.4 port 12345)
1949 @item Node foo does not have the right public/private keypair.
1950 Generate new keypairs and distribute them again.
1951 @item An attacker tries to gain access to your VPN.
1952 @item A network error caused corruption of metadata sent from foo.
1957 @c ==================================================================
1958 @node Sending bug reports
1959 @section Sending bug reports
1961 If you really can't find the cause of a problem, or if you suspect tinc is not working right,
1962 you can send us a bugreport, see @ref{Contact information}.
1963 Be sure to include the following information in your bugreport:
1966 @item A clear description of what you are trying to achieve and what the problem is.
1967 @item What platform (operating system, version, hardware architecture) and which version of tinc you use.
1968 @item If compiling tinc fails, a copy of @file{config.log} and the error messages you get.
1969 @item Otherwise, a copy of @file{tinc.conf}, @file{tinc-up} and all files in the @file{hosts/} directory.
1970 @item The output of the commands @samp{ifconfig -a} and @samp{route -n} (or @samp{netstat -rn} if that doesn't work).
1971 @item The output of any command that fails to work as it should (like ping or traceroute).
1974 @c ==================================================================
1975 @node Technical information
1976 @chapter Technical information
1981 * The meta-protocol::
1986 @c ==================================================================
1987 @node The connection
1988 @section The connection
1991 Tinc is a daemon that takes VPN data and transmit that to another host
1992 computer over the existing Internet infrastructure.
1996 * The meta-connection::
2000 @c ==================================================================
2001 @node The UDP tunnel
2002 @subsection The UDP tunnel
2004 @cindex virtual network device
2006 The data itself is read from a character device file, the so-called
2007 @emph{virtual network device}. This device is associated with a network
2008 interface. Any data sent to this interface can be read from the device,
2009 and any data written to the device gets sent from the interface.
2010 There are two possible types of virtual network devices:
2011 `tun' style, which are point-to-point devices which can only handle IPv4 and/or IPv6 packets,
2012 and `tap' style, which are Ethernet devices and handle complete Ethernet frames.
2014 So when tinc reads an Ethernet frame from the device, it determines its
2015 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
2016 packets. Depending on the Subnet lines, it will send the packets off to their destination IP address.
2017 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
2018 to deduce the destination of the packets.
2019 Since the latter modes only depend on the link layer information,
2020 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
2021 However, only `tap' style devices provide this information.
2023 After the destination has been determined,
2024 the packet will be compressed (optionally),
2025 a sequence number will be added to the packet,
2026 the packet will then be encrypted
2027 and a message authentication code will be appended.
2029 @cindex encapsulating
2031 When that is done, time has come to actually transport the
2032 packet to the destination computer. We do this by sending the packet
2033 over an UDP connection to the destination host. This is called
2034 @emph{encapsulating}, the VPN packet (though now encrypted) is
2035 encapsulated in another IP datagram.
2037 When the destination receives this packet, the same thing happens, only
2038 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
2039 checks the sequence number
2040 and writes the decrypted information to its own virtual network device.
2042 If the virtual network device is a `tun' device (a point-to-point tunnel),
2043 there is no problem for the kernel to accept a packet.
2044 However, if it is a `tap' device (this is the only available type on FreeBSD),
2045 the destination MAC address must match that of the virtual network interface.
2046 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC
2047 can not be known by the sending host.
2048 Tinc solves this by letting the receiving end detect the MAC address of its own virtual network interface
2049 and overwriting the destination MAC address of the received packet.
2051 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
2052 In those modes every interface should have a unique MAC address, so make sure they are not the same.
2053 Because switch and hub modes rely on MAC addresses to function correctly,
2054 these modes cannot be used on the following operating systems which don't have a `tap' style virtual network device:
2055 OpenBSD, NetBSD, Darwin and Solaris.
2058 @c ==================================================================
2059 @node The meta-connection
2060 @subsection The meta-connection
2062 Having only a UDP connection available is not enough. Though suitable
2063 for transmitting data, we want to be able to reliably send other
2064 information, such as routing and session key information to somebody.
2067 TCP is a better alternative, because it already contains protection
2068 against information being lost, unlike UDP.
2070 So we establish two connections. One for the encrypted VPN data, and one
2071 for other information, the meta-data. Hence, we call the second
2072 connection the meta-connection. We can now be sure that the
2073 meta-information doesn't get lost on the way to another computer.
2075 @cindex data-protocol
2076 @cindex meta-protocol
2077 Like with any communication, we must have a protocol, so that everybody
2078 knows what everything stands for, and how she should react. Because we
2079 have two connections, we also have two protocols. The protocol used for
2080 the UDP data is the ``data-protocol,'' the other one is the
2083 The reason we don't use TCP for both protocols is that UDP is much
2084 better for encapsulation, even while it is less reliable. The real
2085 problem is that when TCP would be used to encapsulate a TCP stream
2086 that's on the private network, for every packet sent there would be
2087 three ACKs sent instead of just one. Furthermore, if there would be
2088 a timeout, both TCP streams would sense the timeout, and both would
2089 start re-sending packets.
2092 @c ==================================================================
2093 @node The meta-protocol
2094 @section The meta-protocol
2096 The meta protocol is used to tie all tinc daemons together, and
2097 exchange information about which tinc daemon serves which virtual
2100 The meta protocol consists of requests that can be sent to the other
2101 side. Each request has a unique number and several parameters. All
2102 requests are represented in the standard ASCII character set. It is
2103 possible to use tools such as telnet or netcat to connect to a tinc
2104 daemon started with the --bypass-security option
2105 and to read and write requests by hand, provided that one
2106 understands the numeric codes sent.
2108 The authentication scheme is described in @ref{Authentication protocol}. After a
2109 successful authentication, the server and the client will exchange all the
2110 information about other tinc daemons and subnets they know of, so that both
2111 sides (and all the other tinc daemons behind them) have their information
2118 ------------------------------------------------------------------
2119 ADD_EDGE node1 node2 21.32.43.54 655 222 0
2120 | | | | | +-> options
2121 | | | | +----> weight
2122 | | | +--------> UDP port of node2
2123 | | +----------------> real address of node2
2124 | +-------------------------> name of destination node
2125 +-------------------------------> name of source node
2127 ADD_SUBNET node 192.168.1.0/24
2128 | | +--> prefixlength
2129 | +--------> network address
2130 +------------------> owner of this subnet
2131 ------------------------------------------------------------------
2134 The ADD_EDGE messages are to inform other tinc daemons that a connection between
2135 two nodes exist. The address of the destination node is available so that
2136 VPN packets can be sent directly to that node.
2138 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
2139 to certain nodes. tinc will use it to determine to which node a VPN packet has
2146 ------------------------------------------------------------------
2147 DEL_EDGE node1 node2
2148 | +----> name of destination node
2149 +----------> name of source node
2151 DEL_SUBNET node 192.168.1.0/24
2152 | | +--> prefixlength
2153 | +--------> network address
2154 +------------------> owner of this subnet
2155 ------------------------------------------------------------------
2158 In case a connection between two daemons is closed or broken, DEL_EDGE messages
2159 are sent to inform the other daemons of that fact. Each daemon will calculate a
2160 new route to the the daemons, or mark them unreachable if there isn't any.
2167 ------------------------------------------------------------------
2168 REQ_KEY origin destination
2169 | +--> name of the tinc daemon it wants the key from
2170 +----------> name of the daemon that wants the key
2172 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
2173 | | \______________/ | | +--> MAC length
2174 | | | | +-----> digest algorithm
2175 | | | +--------> cipher algorithm
2176 | | +--> 128 bits key
2177 | +--> name of the daemon that wants the key
2178 +----------> name of the daemon that uses this key
2181 +--> daemon that has changed it's packet key
2182 ------------------------------------------------------------------
2185 The keys used to encrypt VPN packets are not sent out directly. This is
2186 because it would generate a lot of traffic on VPNs with many daemons, and
2187 chances are that not every tinc daemon will ever send a packet to every
2188 other daemon. Instead, if a daemon needs a key it sends a request for it
2189 via the meta connection of the nearest hop in the direction of the
2196 ------------------------------------------------------------------
2199 ------------------------------------------------------------------
2202 There is also a mechanism to check if hosts are still alive. Since network
2203 failures or a crash can cause a daemon to be killed without properly
2204 shutting down the TCP connection, this is necessary to keep an up to date
2205 connection list. PINGs are sent at regular intervals, except when there
2206 is also some other traffic. A little bit of salt (random data) is added
2207 with each PING and PONG message, to make sure that long sequences of PING/PONG
2208 messages without any other traffic won't result in known plaintext.
2210 This basically covers what is sent over the meta connection by tinc.
2213 @c ==================================================================
2219 Tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
2220 alleged Cabal was/is an organisation that was said to keep an eye on the
2221 entire Internet. As this is exactly what you @emph{don't} want, we named
2222 the tinc project after TINC.
2225 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
2226 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
2227 exactly that: encrypt.
2228 Tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
2229 sequence numbers and 4 byte long message authentication codes to make sure
2230 eavesdroppers cannot get and cannot change any information at all from the
2231 packets they can intercept. The encryption algorithm and message authentication
2232 algorithm can be changed in the configuration. The length of the message
2233 authentication codes is also adjustable. The length of the key for the
2234 encryption algorithm is always the default length used by OpenSSL.
2237 * Authentication protocol::
2238 * Encryption of network packets::
2243 @c ==================================================================
2244 @node Authentication protocol
2245 @subsection Authentication protocol
2247 @cindex authentication
2248 A new scheme for authentication in tinc has been devised, which offers some
2249 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
2259 --------------------------------------------------------------------------
2260 client <attempts connection>
2262 server <accepts connection>
2266 +-------> name of tinc daemon
2270 +-------> name of tinc daemon
2272 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
2273 \_________________________________/
2274 +-> RSAKEYLEN bits totally random string S1,
2275 encrypted with server's public RSA key
2277 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
2278 \_________________________________/
2279 +-> RSAKEYLEN bits totally random string S2,
2280 encrypted with client's public RSA key
2283 - the client will symmetrically encrypt outgoing traffic using S1
2284 - the server will symmetrically encrypt outgoing traffic using S2
2286 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
2287 \_________________________________/
2288 +-> CHALLEN bits totally random string H1
2290 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
2291 \_________________________________/
2292 +-> CHALLEN bits totally random string H2
2294 client CHAL_REPLY 816a86
2295 +-> 160 bits SHA1 of H2
2297 server CHAL_REPLY 928ffe
2298 +-> 160 bits SHA1 of H1
2300 After the correct challenge replies are received, both ends have proved
2301 their identity. Further information is exchanged.
2303 client ACK 655 123 0
2305 | +----> estimated weight
2306 +--------> listening port of client
2308 server ACK 655 321 0
2310 | +----> estimated weight
2311 +--------> listening port of server
2312 --------------------------------------------------------------------------
2315 This new scheme has several improvements, both in efficiency and security.
2317 First of all, the server sends exactly the same kind of messages over the wire
2318 as the client. The previous versions of tinc first authenticated the client,
2319 and then the server. This scheme even allows both sides to send their messages
2320 simultaneously, there is no need to wait for the other to send something first.
2321 This means that any calculations that need to be done upon sending or receiving
2322 a message can also be done in parallel. This is especially important when doing
2323 RSA encryption/decryption. Given that these calculations are the main part of
2324 the CPU time spent for the authentication, speed is improved by a factor 2.
2326 Second, only one RSA encrypted message is sent instead of two. This reduces the
2327 amount of information attackers can see (and thus use for a cryptographic
2328 attack). It also improves speed by a factor two, making the total speedup a
2331 Third, and most important:
2332 The symmetric cipher keys are exchanged first, the challenge is done
2333 afterwards. In the previous authentication scheme, because a man-in-the-middle
2334 could pass the challenge/chal_reply phase (by just copying the messages between
2335 the two real tinc daemons), but no information was exchanged that was really
2336 needed to read the rest of the messages, the challenge/chal_reply phase was of
2337 no real use. The man-in-the-middle was only stopped by the fact that only after
2338 the ACK messages were encrypted with the symmetric cipher. Potentially, it
2339 could even send it's own symmetric key to the server (if it knew the server's
2340 public key) and read some of the metadata the server would send it (it was
2341 impossible for the mitm to read actual network packets though). The new scheme
2342 however prevents this.
2344 This new scheme makes sure that first of all, symmetric keys are exchanged. The
2345 rest of the messages are then encrypted with the symmetric cipher. Then, each
2346 side can only read received messages if they have their private key. The
2347 challenge is there to let the other side know that the private key is really
2348 known, because a challenge reply can only be sent back if the challenge is
2349 decrypted correctly, and that can only be done with knowledge of the private
2352 Fourth: the first thing that is sent via the symmetric cipher encrypted
2353 connection is a totally random string, so that there is no known plaintext (for
2354 an attacker) in the beginning of the encrypted stream.
2357 @c ==================================================================
2358 @node Encryption of network packets
2359 @subsection Encryption of network packets
2362 A data packet can only be sent if the encryption key is known to both
2363 parties, and the connection is activated. If the encryption key is not
2364 known, a request is sent to the destination using the meta connection
2365 to retrieve it. The packet is stored in a queue while waiting for the
2369 The UDP packet containing the network packet from the VPN has the following layout:
2372 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
2373 \___________________/\_____/
2375 V +---> digest algorithm
2376 Encrypted with symmetric cipher
2379 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
2380 sequence number that is added in front of the actual VPN packet, to act as a unique
2381 IV for each packet and to prevent replay attacks. A message authentication code
2382 is added to the UDP packet to prevent alteration of packets. By default the
2383 first 4 bytes of the digest are used for this, but this can be changed using
2384 the MACLength configuration variable.
2386 @c ==================================================================
2387 @node Security issues
2388 @subsection Security issues
2390 In August 2000, we discovered the existence of a security hole in all versions
2391 of tinc up to and including 1.0pre2. This had to do with the way we exchanged
2392 keys. Since then, we have been working on a new authentication scheme to make
2393 tinc as secure as possible. The current version uses the OpenSSL library and
2394 uses strong authentication with RSA keys.
2396 On the 29th of December 2001, Jerome Etienne posted a security analysis of tinc
2397 1.0pre4. Due to a lack of sequence numbers and a message authentication code
2398 for each packet, an attacker could possibly disrupt certain network services or
2399 launch a denial of service attack by replaying intercepted packets. The current
2400 version adds sequence numbers and message authentication codes to prevent such
2403 On the 15th of September 2003, Peter Gutmann posted a security analysis of tinc
2404 1.0.1. He argues that the 32 bit sequence number used by tinc is not a good IV,
2405 that tinc's default length of 4 bytes for the MAC is too short, and he doesn't
2406 like tinc's use of RSA during authentication. We do not know of a security hole
2407 in this version of tinc, but tinc's security is not as strong as TLS or IPsec.
2408 We will address these issues in tinc 2.0.
2410 Cryptography is a hard thing to get right. We cannot make any
2411 guarantees. Time, review and feedback are the only things that can
2412 prove the security of any cryptographic product. If you wish to review
2413 tinc or give us feedback, you are stronly encouraged to do so.
2416 @c ==================================================================
2417 @node Platform specific information
2418 @chapter Platform specific information
2421 * Interface configuration::
2425 @c ==================================================================
2426 @node Interface configuration
2427 @section Interface configuration
2429 When configuring an interface, one normally assigns it an address and a
2430 netmask. The address uniquely identifies the host on the network attached to
2431 the interface. The netmask, combined with the address, forms a subnet. It is
2432 used to add a route to the routing table instructing the kernel to send all
2433 packets which fall into that subnet to that interface. Because all packets for
2434 the entire VPN should go to the virtual network interface used by tinc, the
2435 netmask should be such that it encompasses the entire VPN.
2439 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2441 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2442 @item Linux iproute2
2443 @tab @code{ip addr add} @var{address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2445 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2447 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2449 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2451 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2452 @item Darwin (MacOS/X)
2453 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2455 @tab @code{netsh interface ip set address} @var{interface} @code{static} @var{address} @var{netmask}
2460 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2462 @tab @code{ifconfig} @var{interface} @code{add} @var{address}@code{/}@var{prefixlength}
2464 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2466 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2468 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2470 @tab @code{ifconfig} @var{interface} @code{inet6 plumb up}
2472 @tab @code{ifconfig} @var{interface} @code{inet6 addif} @var{address} @var{address}
2473 @item Darwin (MacOS/X)
2474 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2476 @tab @code{netsh interface ipv6 add address} @var{interface} @code{static} @var{address}/@var{prefixlength}
2479 On some platforms, when running tinc in switch mode, the VPN interface must be set to tap mode with an ifconfig command:
2481 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2483 @tab @code{ifconfig} @var{interface} @code{link0}
2486 On Linux, it is possible to create a persistent tun/tap interface which will
2487 continue to exist even if tinc quit, although this is normally not required.
2488 It can be useful to set up a tun/tap interface owned by a non-root user, so
2489 tinc can be started without needing any root privileges at all.
2491 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2493 @tab @code{ip tuntap add dev} @var{interface} @code{mode} @var{tun|tap} @code{user} @var{username}
2496 @c ==================================================================
2500 In some cases it might be necessary to add more routes to the virtual network
2501 interface. There are two ways to indicate which interface a packet should go
2502 to, one is to use the name of the interface itself, another way is to specify
2503 the (local) address that is assigned to that interface (@var{local_address}). The
2504 former way is unambiguous and therefore preferable, but not all platforms
2507 Adding routes to IPv4 subnets:
2509 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2511 @tab @code{route add -net} @var{network_address} @code{netmask} @var{netmask} @var{interface}
2512 @item Linux iproute2
2513 @tab @code{ip route add} @var{network_address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2515 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2517 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2519 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2521 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address} @code{-interface}
2522 @item Darwin (MacOS/X)
2523 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2525 @tab @code{netsh routing ip add persistentroute} @var{network_address} @var{netmask} @var{interface} @var{local_address}
2528 Adding routes to IPv6 subnets:
2530 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2532 @tab @code{route add -A inet6} @var{network_address}@code{/}@var{prefixlength} @var{interface}
2533 @item Linux iproute2
2534 @tab @code{ip route add} @var{network_address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2536 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2538 @tab @code{route add -inet6} @var{network_address} @var{local_address} @code{-prefixlen} @var{prefixlength}
2540 @tab @code{route add -inet6} @var{network_address} @var{local_address} @code{-prefixlen} @var{prefixlength}
2542 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @var{local_address} @code{-interface}
2543 @item Darwin (MacOS/X)
2546 @tab @code{netsh interface ipv6 add route} @var{network address}/@var{prefixlength} @var{interface}
2550 @c ==================================================================
2556 * Contact information::
2561 @c ==================================================================
2562 @node Contact information
2563 @section Contact information
2566 Tinc's website is at @url{http://www.tinc-vpn.org/},
2567 this server is located in the Netherlands.
2570 We have an IRC channel on the FreeNode and OFTC IRC networks. Connect to
2571 @uref{http://www.freenode.net/, irc.freenode.net}
2573 @uref{http://www.oftc.net/, irc.oftc.net}
2574 and join channel #tinc.
2577 @c ==================================================================
2582 @item Ivo Timmermans (zarq)
2583 @item Guus Sliepen (guus) (@email{guus@@tinc-vpn.org})
2586 We have received a lot of valuable input from users. With their help,
2587 tinc has become the flexible and robust tool that it is today. We have
2588 composed a list of contributions, in the file called @file{THANKS} in
2589 the source distribution.
2592 @c ==================================================================
2594 @unnumbered Concept Index
2596 @c ==================================================================
2600 @c ==================================================================