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{} 1998-2013 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{} 1998-2013 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 IffOneQueue = <yes|no> (no) [experimental]
955 (Linux only) Set IFF_ONE_QUEUE flag on TUN/TAP devices.
958 @item Interface = <@var{interface}>
959 Defines the name of the interface corresponding to the virtual network device.
960 Depending on the operating system and the type of device this may or may not actually set the name of the interface.
961 Under Windows, this variable is used to select which network interface will be used.
962 If you specified a Device, this variable is almost always already correctly set.
965 @item KeyExpire = <@var{seconds}> (3600)
966 This option controls the time the encryption keys used to encrypt the data
967 are valid. It is common practice to change keys at regular intervals to
968 make it even harder for crackers, even though it is thought to be nearly
969 impossible to crack a single key.
971 @cindex LocalDiscovery
972 @item LocalDiscovery = <yes | no> (no) [experimental]
973 When enabled, tinc will try to detect peers that are on the same local network.
974 This will allow direct communication using LAN addresses, even if both peers are behind a NAT
975 and they only ConnectTo a third node outside the NAT,
976 which normally would prevent the peers from learning each other's LAN address.
978 Currently, local discovery is implemented by sending broadcast packets to the LAN during path MTU discovery.
979 This feature may not work in all possible situations.
982 @item MACExpire = <@var{seconds}> (600)
983 This option controls the amount of time MAC addresses are kept before they are removed.
984 This only has effect when Mode is set to "switch".
987 @item MaxTimeout = <@var{seconds}> (900)
988 This is the maximum delay before trying to reconnect to other tinc daemons.
991 @item Mode = <router|switch|hub> (router)
992 This option selects the way packets are routed to other daemons.
998 variables in the host configuration files will be used to form a routing table.
999 Only unicast packets of routable protocols (IPv4 and IPv6) are supported in this mode.
1001 This is the default mode, and unless you really know you need another mode, don't change it.
1005 In this mode the MAC addresses of the packets on the VPN will be used to
1006 dynamically create a routing table just like an Ethernet switch does.
1007 Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
1008 at the cost of frequent broadcast ARP requests and routing table updates.
1010 This mode is primarily useful if you want to bridge Ethernet segments.
1014 This mode is almost the same as the switch mode, but instead
1015 every packet will be broadcast to the other daemons
1016 while no routing table is managed.
1020 @item Name = <@var{name}> [required]
1021 This is a symbolic name for this connection.
1022 The name should consist only of alfanumeric and underscore characters (a-z, A-Z, 0-9 and _).
1024 If Name starts with a $, then the contents of the environment variable that follows will be used.
1025 In that case, invalid characters will be converted to underscores.
1026 If Name is $HOST, but no such environment variable exist,
1027 the hostname will be read using the gethostnname() system call.
1029 @cindex PingInterval
1030 @item PingInterval = <@var{seconds}> (60)
1031 The number of seconds of inactivity that tinc will wait before sending a
1032 probe to the other end.
1035 @item PingTimeout = <@var{seconds}> (5)
1036 The number of seconds to wait for a response to pings or to allow meta
1037 connections to block. If the other end doesn't respond within this time,
1038 the connection is terminated, and the others will be notified of this.
1040 @cindex PriorityInheritance
1041 @item PriorityInheritance = <yes|no> (no) [experimental]
1042 When this option is enabled the value of the TOS field of tunneled IPv4 packets
1043 will be inherited by the UDP packets that are sent out.
1046 @item PrivateKey = <@var{key}> [obsolete]
1047 This is the RSA private key for tinc. However, for safety reasons it is
1048 advised to store private keys of any kind in separate files. This prevents
1049 accidental eavesdropping if you are editting the configuration file.
1051 @cindex PrivateKeyFile
1052 @item PrivateKeyFile = <@var{path}> (@file{@value{sysconfdir}/tinc/@var{netname}/rsa_key.priv})
1053 This is the full path name of the RSA private key file that was
1054 generated by @samp{tincd --generate-keys}. It must be a full path, not a
1057 @cindex ProcessPriority
1058 @item ProcessPriority = <low|normal|high>
1059 When this option is used the priority of the tincd process will be adjusted.
1060 Increasing the priority may help to reduce latency and packet loss on the VPN.
1063 @item Proxy = socks4 | socks5 | http | exec @var{...} [experimental]
1064 Use a proxy when making outgoing connections.
1065 The following proxy types are currently supported:
1069 @item socks4 <@var{address}> <@var{port}> [<@var{username}>]
1070 Connects to the proxy using the SOCKS version 4 protocol.
1071 Optionally, a @var{username} can be supplied which will be passed on to the proxy server.
1074 @item socks5 <@var{address}> <@var{port}> [<@var{username}> <@var{password}>]
1075 Connect to the proxy using the SOCKS version 5 protocol.
1076 If a @var{username} and @var{password} are given, basic username/password authentication will be used,
1077 otherwise no authentication will be used.
1080 @item http <@var{address}> <@var{port}>
1081 Connects to the proxy and sends a HTTP CONNECT request.
1084 @item exec <@var{command}>
1085 Executes the given command which should set up the outgoing connection.
1086 The environment variables @env{NAME}, @env{NODE}, @env{REMOTEADDRES} and @env{REMOTEPORT} are available.
1089 @cindex ReplayWindow
1090 @item ReplayWindow = <bytes> (16)
1091 This is the size of the replay tracking window for each remote node, in bytes.
1092 The window is a bitfield which tracks 1 packet per bit, so for example
1093 the default setting of 16 will track up to 128 packets in the window. In high
1094 bandwidth scenarios, setting this to a higher value can reduce packet loss from
1095 the interaction of replay tracking with underlying real packet loss and/or
1096 reordering. Setting this to zero will disable replay tracking completely and
1097 pass all traffic, but leaves tinc vulnerable to replay-based attacks on your
1100 @cindex StrictSubnets
1101 @item StrictSubnets = <yes|no> (no) [experimental]
1102 When this option is enabled tinc will only use Subnet statements which are
1103 present in the host config files in the local
1104 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
1106 @cindex TunnelServer
1107 @item TunnelServer = <yes|no> (no) [experimental]
1108 When this option is enabled tinc will no longer forward information between other tinc daemons,
1109 and will only allow connections with nodes for which host config files are present in the local
1110 @file{@value{sysconfdir}/tinc/@var{netname}/hosts/} directory.
1111 Setting this options also implicitly sets StrictSubnets.
1114 @item UDPRcvBuf = <bytes> (OS default)
1115 Sets the socket receive buffer size for the UDP socket, in bytes.
1116 If unset, the default buffer size will be used by the operating system.
1119 @item UDPSndBuf = <bytes> Pq OS default
1120 Sets the socket send buffer size for the UDP socket, in bytes.
1121 If unset, the default buffer size will be used by the operating system.
1126 @c ==================================================================
1127 @node Host configuration variables
1128 @subsection Host configuration variables
1132 @item Address = <@var{IP address}|@var{hostname}> [<port>] [recommended]
1133 This variable is only required if you want to connect to this host. It
1134 must resolve to the external IP address where the host can be reached,
1135 not the one that is internal to the VPN.
1136 If no port is specified, the default Port is used.
1137 Multiple Address variables can be specified, in which case each address will be
1138 tried until a working connection has been established.
1141 @item Cipher = <@var{cipher}> (blowfish)
1142 The symmetric cipher algorithm used to encrypt UDP packets.
1143 Any cipher supported by OpenSSL is recognized.
1144 Furthermore, specifying "none" will turn off packet encryption.
1145 It is best to use only those ciphers which support CBC mode.
1148 @item ClampMSS = <yes|no> (yes)
1149 This option specifies whether tinc should clamp the maximum segment size (MSS)
1150 of TCP packets to the path MTU. This helps in situations where ICMP
1151 Fragmentation Needed or Packet too Big messages are dropped by firewalls.
1154 @item Compression = <@var{level}> (0)
1155 This option sets the level of compression used for UDP packets.
1156 Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
1157 10 (fast lzo) and 11 (best lzo).
1160 @item Digest = <@var{digest}> (sha1)
1161 The digest algorithm used to authenticate UDP packets.
1162 Any digest supported by OpenSSL is recognized.
1163 Furthermore, specifying "none" will turn off packet authentication.
1165 @cindex IndirectData
1166 @item IndirectData = <yes|no> (no)
1167 This option specifies whether other tinc daemons besides the one you
1168 specified with ConnectTo can make a direct connection to you. This is
1169 especially useful if you are behind a firewall and it is impossible to
1170 make a connection from the outside to your tinc daemon. Otherwise, it
1171 is best to leave this option out or set it to no.
1174 @item MACLength = <@var{bytes}> (4)
1175 The length of the message authentication code used to authenticate UDP packets.
1176 Can be anything from 0
1177 up to the length of the digest produced by the digest algorithm.
1180 @item PMTU = <@var{mtu}> (1514)
1181 This option controls the initial path MTU to this node.
1183 @cindex PMTUDiscovery
1184 @item PMTUDiscovery = <yes|no> (yes)
1185 When this option is enabled, tinc will try to discover the path MTU to this node.
1186 After the path MTU has been discovered, it will be enforced on the VPN.
1189 @item Port = <@var{port}> (655)
1190 This is the port this tinc daemon listens on.
1191 You can use decimal portnumbers or symbolic names (as listed in @file{/etc/services}).
1194 @item PublicKey = <@var{key}> [obsolete]
1195 This is the RSA public key for this host.
1197 @cindex PublicKeyFile
1198 @item PublicKeyFile = <@var{path}> [obsolete]
1199 This is the full path name of the RSA public key file that was generated
1200 by @samp{tincd --generate-keys}. It must be a full path, not a relative
1204 From version 1.0pre4 on tinc will store the public key directly into the
1205 host configuration file in PEM format, the above two options then are not
1206 necessary. Either the PEM format is used, or exactly
1207 @strong{one of the above two options} must be specified
1208 in each host configuration file, if you want to be able to establish a
1209 connection with that host.
1212 @item Subnet = <@var{address}[/@var{prefixlength}[#@var{weight}]]>
1213 The subnet which this tinc daemon will serve.
1214 Tinc tries to look up which other daemon it should send a packet to by searching the appropiate subnet.
1215 If the packet matches a subnet,
1216 it will be sent to the daemon who has this subnet in his host configuration file.
1217 Multiple subnet lines can be specified for each daemon.
1219 Subnets can either be single MAC, IPv4 or IPv6 addresses,
1220 in which case a subnet consisting of only that single address is assumed,
1221 or they can be a IPv4 or IPv6 network address with a prefixlength.
1222 For example, IPv4 subnets must be in a form like 192.168.1.0/24,
1223 where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
1224 Note that subnets like 192.168.1.1/24 are invalid!
1225 Read a networking HOWTO/FAQ/guide if you don't understand this.
1226 IPv6 subnets are notated like fec0:0:0:1::/64.
1227 MAC addresses are notated like 0:1a:2b:3c:4d:5e.
1229 @cindex CIDR notation
1230 Prefixlength is the number of bits set to 1 in the netmask part; for
1231 example: netmask 255.255.255.0 would become /24, 255.255.252.0 becomes
1232 /22. This conforms to standard CIDR notation as described in
1233 @uref{http://www.ietf.org/rfc/rfc1519.txt, RFC1519}
1235 @cindex Subnet weight
1236 A Subnet can be given a weight to indicate its priority over identical Subnets
1237 owned by different nodes. The default weight is 10. Lower values indicate
1238 higher priority. Packets will be sent to the node with the highest priority,
1239 unless that node is not reachable, in which case the node with the next highest
1240 priority will be tried, and so on.
1243 @item TCPonly = <yes|no> (no) [deprecated]
1244 If this variable is set to yes, then the packets are tunnelled over a
1245 TCP connection instead of a UDP connection. This is especially useful
1246 for those who want to run a tinc daemon from behind a masquerading
1247 firewall, or if UDP packet routing is disabled somehow.
1248 Setting this options also implicitly sets IndirectData.
1250 Since version 1.0.10, tinc will automatically detect whether communication via
1251 UDP is possible or not.
1255 @c ==================================================================
1260 Apart from reading the server and host configuration files,
1261 tinc can also run scripts at certain moments.
1262 Under Windows (not Cygwin), the scripts should have the extension .bat.
1266 @item @value{sysconfdir}/tinc/@var{netname}/tinc-up
1267 This is the most important script.
1268 If it is present it will be executed right after the tinc daemon has been
1269 started and has connected to the virtual network device.
1270 It should be used to set up the corresponding network interface,
1271 but can also be used to start other things.
1272 Under Windows you can use the Network Connections control panel instead of creating this script.
1275 @item @value{sysconfdir}/tinc/@var{netname}/tinc-down
1276 This script is started right before the tinc daemon quits.
1278 @item @value{sysconfdir}/tinc/@var{netname}/hosts/@var{host}-up
1279 This script is started when the tinc daemon with name @var{host} becomes reachable.
1281 @item @value{sysconfdir}/tinc/@var{netname}/hosts/@var{host}-down
1282 This script is started when the tinc daemon with name @var{host} becomes unreachable.
1284 @item @value{sysconfdir}/tinc/@var{netname}/host-up
1285 This script is started when any host becomes reachable.
1287 @item @value{sysconfdir}/tinc/@var{netname}/host-down
1288 This script is started when any host becomes unreachable.
1290 @item @value{sysconfdir}/tinc/@var{netname}/subnet-up
1291 This script is started when a Subnet becomes reachable.
1292 The Subnet and the node it belongs to are passed in environment variables.
1294 @item @value{sysconfdir}/tinc/@var{netname}/subnet-down
1295 This script is started when a Subnet becomes unreachable.
1298 @cindex environment variables
1299 The scripts are started without command line arguments,
1300 but can make use of certain environment variables.
1301 Under UNIX like operating systems the names of environment variables must be preceded by a $ in scripts.
1302 Under Windows, in @file{.bat} files, they have to be put between % signs.
1307 If a netname was specified, this environment variable contains it.
1311 Contains the name of this tinc daemon.
1315 Contains the name of the virtual network device that tinc uses.
1319 Contains the name of the virtual network interface that tinc uses.
1320 This should be used for commands like ifconfig.
1324 When a host becomes (un)reachable, this is set to its name.
1325 If a subnet becomes (un)reachable, this is set to the owner of that subnet.
1327 @cindex REMOTEADDRESS
1329 When a host becomes (un)reachable, this is set to its real address.
1333 When a host becomes (un)reachable,
1334 this is set to the port number it uses for communication with other tinc daemons.
1338 When a subnet becomes (un)reachable, this is set to the subnet.
1342 When a subnet becomes (un)reachable, this is set to the subnet weight.
1347 @c ==================================================================
1348 @node How to configure
1349 @subsection How to configure
1351 @subsubheading Step 1. Creating the main configuration file
1353 The main configuration file will be called @file{@value{sysconfdir}/tinc/@var{netname}/tinc.conf}.
1354 Adapt the following example to create a basic configuration file:
1357 Name = @var{yourname}
1358 Device = @file{/dev/tap0}
1361 Then, if you know to which other tinc daemon(s) yours is going to connect,
1362 add `ConnectTo' values.
1364 @subsubheading Step 2. Creating your host configuration file
1366 If you added a line containing `Name = yourname' in the main configuarion file,
1367 you will need to create a host configuration file @file{@value{sysconfdir}/tinc/@var{netname}/hosts/yourname}.
1368 Adapt the following example to create a host configuration file:
1371 Address = your.real.hostname.org
1372 Subnet = 192.168.1.0/24
1375 You can also use an IP address instead of a hostname.
1376 The `Subnet' specifies the address range that is local for @emph{your part of the VPN only}.
1377 If you have multiple address ranges you can specify more than one `Subnet'.
1378 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).
1381 @c ==================================================================
1382 @node Generating keypairs
1383 @section Generating keypairs
1385 @cindex key generation
1386 Now that you have already created the main configuration file and your host configuration file,
1387 you can easily create a public/private keypair by entering the following command:
1390 tincd -n @var{netname} -K
1393 Tinc will generate a public and a private key and ask you where to put them.
1394 Just press enter to accept the defaults.
1397 @c ==================================================================
1398 @node Network interfaces
1399 @section Network interfaces
1401 Before tinc can start transmitting data over the tunnel, it must
1402 set up the virtual network interface.
1404 First, decide which IP addresses you want to have associated with these
1405 devices, and what network mask they must have.
1407 Tinc will open a virtual network device (@file{/dev/tun}, @file{/dev/tap0} or similar),
1408 which will also create a network interface called something like @samp{tun0}, @samp{tap0}.
1409 If you are using the Linux tun/tap driver, the network interface will by default have the same name as the @var{netname}.
1410 Under Windows you can change the name of the network interface from the Network Connections control panel.
1413 You can configure the network interface by putting ordinary ifconfig, route, and other commands
1414 to a script named @file{@value{sysconfdir}/tinc/@var{netname}/tinc-up}.
1415 When tinc starts, this script will be executed. When tinc exits, it will execute the script named
1416 @file{@value{sysconfdir}/tinc/@var{netname}/tinc-down}, but normally you don't need to create that script.
1418 An example @file{tinc-up} script:
1422 ifconfig $INTERFACE 192.168.1.1 netmask 255.255.0.0
1425 This script gives the interface an IP address and a netmask.
1426 The kernel will also automatically add a route to this interface, so normally you don't need
1427 to add route commands to the @file{tinc-up} script.
1428 The kernel will also bring the interface up after this command.
1430 The netmask is the mask of the @emph{entire} VPN network, not just your
1433 The exact syntax of the ifconfig and route commands differs from platform to platform.
1434 You can look up the commands for setting addresses and adding routes in @ref{Platform specific information},
1435 but it is best to consult the manpages of those utilities on your platform.
1438 @c ==================================================================
1439 @node Example configuration
1440 @section Example configuration
1444 Imagine the following situation. Branch A of our example `company' wants to connect
1445 three branch offices in B, C and D using the Internet. All four offices
1446 have a 24/7 connection to the Internet.
1448 A is going to serve as the center of the network. B and C will connect
1449 to A, and D will connect to C. Each office will be assigned their own IP
1453 A: net 10.1.0.0 mask 255.255.0.0 gateway 10.1.54.1 internet IP 1.2.3.4
1454 B: net 10.2.0.0 mask 255.255.0.0 gateway 10.2.1.12 internet IP 2.3.4.5
1455 C: net 10.3.0.0 mask 255.255.0.0 gateway 10.3.69.254 internet IP 3.4.5.6
1456 D: net 10.4.0.0 mask 255.255.0.0 gateway 10.4.3.32 internet IP 4.5.6.7
1459 Here, ``gateway'' is the VPN IP address of the machine that is running the
1460 tincd, and ``internet IP'' is the IP address of the firewall, which does not
1461 need to run tincd, but it must do a port forwarding of TCP and UDP on port
1462 655 (unless otherwise configured).
1464 In this example, it is assumed that eth0 is the interface that points to
1465 the inner (physical) LAN of the office, although this could also be the
1466 same as the interface that leads to the Internet. The configuration of
1467 the real interface is also shown as a comment, to give you an idea of
1468 how these example host is set up. All branches use the netname `company'
1469 for this particular VPN.
1471 @subsubheading For Branch A
1473 @emph{BranchA} would be configured like this:
1475 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1478 # Real interface of internal network:
1479 # ifconfig eth0 10.1.54.1 netmask 255.255.0.0
1481 ifconfig $INTERFACE 10.1.54.1 netmask 255.0.0.0
1484 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1491 On all hosts, @file{@value{sysconfdir}/tinc/company/hosts/BranchA} contains:
1494 Subnet = 10.1.0.0/16
1497 -----BEGIN RSA PUBLIC KEY-----
1499 -----END RSA PUBLIC KEY-----
1502 Note that the IP addresses of eth0 and tap0 are the same.
1503 This is quite possible, if you make sure that the netmasks of the interfaces are different.
1504 It is in fact recommended to give both real internal network interfaces and tap interfaces the same IP address,
1505 since that will make things a lot easier to remember and set up.
1508 @subsubheading For Branch B
1510 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1513 # Real interface of internal network:
1514 # ifconfig eth0 10.2.43.8 netmask 255.255.0.0
1516 ifconfig $INTERFACE 10.2.1.12 netmask 255.0.0.0
1519 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1526 Note here that the internal address (on eth0) doesn't have to be the
1527 same as on the tap0 device. Also, ConnectTo is given so that this node will
1528 always try to connect to BranchA.
1530 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchB}:
1533 Subnet = 10.2.0.0/16
1536 -----BEGIN RSA PUBLIC KEY-----
1538 -----END RSA PUBLIC KEY-----
1542 @subsubheading For Branch C
1544 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1547 # Real interface of internal network:
1548 # ifconfig eth0 10.3.69.254 netmask 255.255.0.0
1550 ifconfig $INTERFACE 10.3.69.254 netmask 255.0.0.0
1553 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1561 C already has another daemon that runs on port 655, so they have to
1562 reserve another port for tinc. It knows the portnumber it has to listen on
1563 from it's own host configuration file.
1565 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchC}:
1569 Subnet = 10.3.0.0/16
1572 -----BEGIN RSA PUBLIC KEY-----
1574 -----END RSA PUBLIC KEY-----
1578 @subsubheading For Branch D
1580 In @file{@value{sysconfdir}/tinc/company/tinc-up}:
1583 # Real interface of internal network:
1584 # ifconfig eth0 10.4.3.32 netmask 255.255.0.0
1586 ifconfig $INTERFACE 10.4.3.32 netmask 255.0.0.0
1589 and in @file{@value{sysconfdir}/tinc/company/tinc.conf}:
1594 Device = /dev/net/tun
1597 D will be connecting to C, which has a tincd running for this network on
1598 port 2000. It knows the port number from the host configuration file.
1599 Also note that since D uses the tun/tap driver, the network interface
1600 will not be called `tun' or `tap0' or something like that, but will
1601 have the same name as netname.
1603 On all hosts, in @file{@value{sysconfdir}/tinc/company/hosts/BranchD}:
1606 Subnet = 10.4.0.0/16
1609 -----BEGIN RSA PUBLIC KEY-----
1611 -----END RSA PUBLIC KEY-----
1614 @subsubheading Key files
1616 A, B, C and D all have generated a public/private keypair with the following command:
1622 The private key is stored in @file{@value{sysconfdir}/tinc/company/rsa_key.priv},
1623 the public key is put into the host configuration file in the @file{@value{sysconfdir}/tinc/company/hosts/} directory.
1624 During key generation, tinc automatically guesses the right filenames based on the -n option and
1625 the Name directive in the @file{tinc.conf} file (if it is available).
1627 @subsubheading Starting
1629 After each branch has finished configuration and they have distributed
1630 the host configuration files amongst them, they can start their tinc daemons.
1631 They don't necessarily have to wait for the other branches to have started
1632 their daemons, tinc will try connecting until they are available.
1635 @c ==================================================================
1637 @chapter Running tinc
1639 If everything else is done, you can start tinc by typing the following command:
1642 tincd -n @var{netname}
1646 Tinc will detach from the terminal and continue to run in the background like a good daemon.
1647 If there are any problems however you can try to increase the debug level
1648 and look in the syslog to find out what the problems are.
1654 * Solving problems::
1656 * Sending bug reports::
1660 @c ==================================================================
1661 @node Runtime options
1662 @section Runtime options
1664 Besides the settings in the configuration file, tinc also accepts some
1665 command line options.
1667 @cindex command line
1668 @cindex runtime options
1672 @item -c, --config=@var{path}
1673 Read configuration options from the directory @var{path}. The default is
1674 @file{@value{sysconfdir}/tinc/@var{netname}/}.
1676 @item -D, --no-detach
1677 Don't fork and detach.
1678 This will also disable the automatic restart mechanism for fatal errors.
1681 @item -d, --debug=@var{level}
1682 Set debug level to @var{level}. The higher the debug level, the more gets
1683 logged. Everything goes via syslog.
1685 @item -k, --kill[=@var{signal}]
1686 Attempt to kill a running tincd (optionally with the specified @var{signal} instead of SIGTERM) and exit.
1687 Use it in conjunction with the -n option to make sure you kill the right tinc daemon.
1688 Under native Windows the optional argument is ignored,
1689 the service will always be stopped and removed.
1691 @item -n, --net=@var{netname}
1692 Use configuration for net @var{netname}.
1693 This will let tinc read all configuration files from
1694 @file{@value{sysconfdir}/tinc/@var{netname}/}.
1695 Specifying . for @var{netname} is the same as not specifying any @var{netname}.
1696 @xref{Multiple networks}.
1698 @item -K, --generate-keys[=@var{bits}]
1699 Generate public/private keypair of @var{bits} length. If @var{bits} is not specified,
1700 2048 is the default. tinc will ask where you want to store the files,
1701 but will default to the configuration directory (you can use the -c or -n option
1702 in combination with -K). After that, tinc will quit.
1704 @item -o, --option=[@var{HOST}.]@var{KEY}=@var{VALUE}
1705 Without specifying a @var{HOST}, this will set server configuration variable @var{KEY} to @var{VALUE}.
1706 If specified as @var{HOST}.@var{KEY}=@var{VALUE},
1707 this will set the host configuration variable @var{KEY} of the host named @var{HOST} to @var{VALUE}.
1708 This option can be used more than once to specify multiple configuration variables.
1711 Lock tinc into main memory.
1712 This will prevent sensitive data like shared private keys to be written to the system swap files/partitions.
1714 @item --logfile[=@var{file}]
1715 Write log entries to a file instead of to the system logging facility.
1716 If @var{file} is omitted, the default is @file{@value{localstatedir}/log/tinc.@var{netname}.log}.
1718 @item --pidfile=@var{file}
1719 Write PID to @var{file} instead of @file{@value{localstatedir}/run/tinc.@var{netname}.pid}.
1721 @item --bypass-security
1722 Disables encryption and authentication.
1723 Only useful for debugging.
1726 Change process root directory to the directory where the config file is
1727 located (@file{@value{sysconfdir}/tinc/@var{netname}/} as determined by
1728 -n/--net option or as given by -c/--config option), for added security.
1729 The chroot is performed after all the initialization is done, after
1730 writing pid files and opening network sockets.
1732 Note that this option alone does not do any good without -U/--user, below.
1734 Note also that tinc can't run scripts anymore (such as tinc-down or host-up),
1735 unless it's setup to be runnable inside chroot environment.
1737 @item -U, --user=@var{user}
1738 Switch to the given @var{user} after initialization, at the same time as
1739 chroot is performed (see --chroot above). With this option tinc drops
1740 privileges, for added security.
1743 Display a short reminder of these runtime options and terminate.
1746 Output version information and exit.
1750 @c ==================================================================
1755 You can also send the following signals to a running tincd process:
1761 Forces tinc to try to connect to all uplinks immediately.
1762 Usually tinc attempts to do this itself,
1763 but increases the time it waits between the attempts each time it failed,
1764 and if tinc didn't succeed to connect to an uplink the first time after it started,
1765 it defaults to the maximum time of 15 minutes.
1768 Partially rereads configuration files.
1769 Connections to hosts whose host config file are removed are closed.
1770 New outgoing connections specified in @file{tinc.conf} will be made.
1771 If the --logfile option is used, this will also close and reopen the log file,
1772 useful when log rotation is used.
1775 Temporarily increases debug level to 5.
1776 Send this signal again to revert to the original level.
1779 Dumps the connection list to syslog.
1782 Dumps virtual network device statistics, all known nodes, edges and subnets to syslog.
1785 Purges all information remembered about unreachable nodes.
1789 @c ==================================================================
1791 @section Debug levels
1793 @cindex debug levels
1794 The tinc daemon can send a lot of messages to the syslog.
1795 The higher the debug level, the more messages it will log.
1796 Each level inherits all messages of the previous level:
1802 This will log a message indicating tinc has started along with a version number.
1803 It will also log any serious error.
1806 This will log all connections that are made with other tinc daemons.
1809 This will log status and error messages from scripts and other tinc daemons.
1812 This will log all requests that are exchanged with other tinc daemons. These include
1813 authentication, key exchange and connection list updates.
1816 This will log a copy of everything received on the meta socket.
1819 This will log all network traffic over the virtual private network.
1823 @c ==================================================================
1824 @node Solving problems
1825 @section Solving problems
1827 If tinc starts without problems, but if the VPN doesn't work, you will have to find the cause of the problem.
1828 The first thing to do is to start tinc with a high debug level in the foreground,
1829 so you can directly see everything tinc logs:
1832 tincd -n @var{netname} -d5 -D
1835 If tinc does not log any error messages, then you might want to check the following things:
1838 @item @file{tinc-up} script
1839 Does this script contain the right commands?
1840 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.
1843 Does the Subnet (or Subnets) in the host configuration file of this host match the portion of the VPN that belongs to this host?
1845 @item Firewalls and NATs
1846 Do you have a firewall or a NAT device (a masquerading firewall or perhaps an ADSL router that performs masquerading)?
1847 If so, check that it allows TCP and UDP traffic on port 655.
1848 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.
1849 You can add @samp{TCPOnly = yes} to your host config file to force tinc to only use a single TCP connection,
1850 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.
1855 @c ==================================================================
1856 @node Error messages
1857 @section Error messages
1859 What follows is a list of the most common error messages you might find in the logs.
1860 Some of them will only be visible if the debug level is high enough.
1863 @item Could not open /dev/tap0: No such device
1866 @item You forgot to `modprobe netlink_dev' or `modprobe ethertap'.
1867 @item You forgot to compile `Netlink device emulation' in the kernel.
1870 @item Can't write to /dev/net/tun: No such device
1873 @item You forgot to `modprobe tun'.
1874 @item You forgot to compile `Universal TUN/TAP driver' in the kernel.
1875 @item The tun device is located somewhere else in @file{/dev/}.
1878 @item Network address and prefix length do not match!
1881 @item The Subnet field must contain a @emph{network} address, trailing bits should be 0.
1882 @item If you only want to use one IP address, set the netmask to /32.
1885 @item Error reading RSA key file `rsa_key.priv': No such file or directory
1888 @item You forgot to create a public/private keypair.
1889 @item Specify the complete pathname to the private key file with the @samp{PrivateKeyFile} option.
1892 @item Warning: insecure file permissions for RSA private key file `rsa_key.priv'!
1895 @item The private key file is readable by users other than root.
1896 Use chmod to correct the file permissions.
1899 @item Creating metasocket failed: Address family not supported
1902 @item By default tinc tries to create both IPv4 and IPv6 sockets.
1903 On some platforms this might not be implemented.
1904 If the logs show @samp{Ready} later on, then at least one metasocket was created,
1905 and you can ignore this message.
1906 You can add @samp{AddressFamily = ipv4} to @file{tinc.conf} to prevent this from happening.
1909 @item Cannot route packet: unknown IPv4 destination 1.2.3.4
1912 @item You try to send traffic to a host on the VPN for which no Subnet is known.
1913 @item If it is a broadcast address (ending in .255), it probably is a samba server or a Windows host sending broadcast packets.
1917 @item Cannot route packet: ARP request for unknown address 1.2.3.4
1920 @item You try to send traffic to a host on the VPN for which no Subnet is known.
1923 @item Packet with destination 1.2.3.4 is looping back to us!
1926 @item Something is not configured right. Packets are being sent out to the
1927 virtual network device, but according to the Subnet directives in your host configuration
1928 file, those packets should go to your own host. Most common mistake is that
1929 you have a Subnet line in your host configuration file with a prefix length which is
1930 just as large as the prefix of the virtual network interface. The latter should in almost all
1931 cases be larger. Rethink your configuration.
1932 Note that you will only see this message if you specified a debug
1933 level of 5 or higher!
1934 @item Chances are that a @samp{Subnet = ...} line in the host configuration file of this tinc daemon is wrong.
1935 Change it to a subnet that is accepted locally by another interface,
1936 or if that is not the case, try changing the prefix length into /32.
1939 @item Node foo (1.2.3.4) is not reachable
1942 @item Node foo does not have a connection anymore, its tinc daemon is not running or its connection to the Internet is broken.
1945 @item Received UDP packet from unknown source 1.2.3.4 (port 12345)
1948 @item If you see this only sporadically, it is harmless and caused by a node sending packets using an old key.
1951 @item Got bad/bogus/unauthorized REQUEST from foo (1.2.3.4 port 12345)
1954 @item Node foo does not have the right public/private keypair.
1955 Generate new keypairs and distribute them again.
1956 @item An attacker tries to gain access to your VPN.
1957 @item A network error caused corruption of metadata sent from foo.
1962 @c ==================================================================
1963 @node Sending bug reports
1964 @section Sending bug reports
1966 If you really can't find the cause of a problem, or if you suspect tinc is not working right,
1967 you can send us a bugreport, see @ref{Contact information}.
1968 Be sure to include the following information in your bugreport:
1971 @item A clear description of what you are trying to achieve and what the problem is.
1972 @item What platform (operating system, version, hardware architecture) and which version of tinc you use.
1973 @item If compiling tinc fails, a copy of @file{config.log} and the error messages you get.
1974 @item Otherwise, a copy of @file{tinc.conf}, @file{tinc-up} and all files in the @file{hosts/} directory.
1975 @item The output of the commands @samp{ifconfig -a} and @samp{route -n} (or @samp{netstat -rn} if that doesn't work).
1976 @item The output of any command that fails to work as it should (like ping or traceroute).
1979 @c ==================================================================
1980 @node Technical information
1981 @chapter Technical information
1986 * The meta-protocol::
1991 @c ==================================================================
1992 @node The connection
1993 @section The connection
1996 Tinc is a daemon that takes VPN data and transmit that to another host
1997 computer over the existing Internet infrastructure.
2001 * The meta-connection::
2005 @c ==================================================================
2006 @node The UDP tunnel
2007 @subsection The UDP tunnel
2009 @cindex virtual network device
2011 The data itself is read from a character device file, the so-called
2012 @emph{virtual network device}. This device is associated with a network
2013 interface. Any data sent to this interface can be read from the device,
2014 and any data written to the device gets sent from the interface.
2015 There are two possible types of virtual network devices:
2016 `tun' style, which are point-to-point devices which can only handle IPv4 and/or IPv6 packets,
2017 and `tap' style, which are Ethernet devices and handle complete Ethernet frames.
2019 So when tinc reads an Ethernet frame from the device, it determines its
2020 type. When tinc is in it's default routing mode, it can handle IPv4 and IPv6
2021 packets. Depending on the Subnet lines, it will send the packets off to their destination IP address.
2022 In the `switch' and `hub' mode, tinc will use broadcasts and MAC address discovery
2023 to deduce the destination of the packets.
2024 Since the latter modes only depend on the link layer information,
2025 any protocol that runs over Ethernet is supported (for instance IPX and Appletalk).
2026 However, only `tap' style devices provide this information.
2028 After the destination has been determined,
2029 the packet will be compressed (optionally),
2030 a sequence number will be added to the packet,
2031 the packet will then be encrypted
2032 and a message authentication code will be appended.
2034 @cindex encapsulating
2036 When that is done, time has come to actually transport the
2037 packet to the destination computer. We do this by sending the packet
2038 over an UDP connection to the destination host. This is called
2039 @emph{encapsulating}, the VPN packet (though now encrypted) is
2040 encapsulated in another IP datagram.
2042 When the destination receives this packet, the same thing happens, only
2043 in reverse. So it checks the message authentication code, decrypts the contents of the UDP datagram,
2044 checks the sequence number
2045 and writes the decrypted information to its own virtual network device.
2047 If the virtual network device is a `tun' device (a point-to-point tunnel),
2048 there is no problem for the kernel to accept a packet.
2049 However, if it is a `tap' device (this is the only available type on FreeBSD),
2050 the destination MAC address must match that of the virtual network interface.
2051 If tinc is in it's default routing mode, ARP does not work, so the correct destination MAC
2052 can not be known by the sending host.
2053 Tinc solves this by letting the receiving end detect the MAC address of its own virtual network interface
2054 and overwriting the destination MAC address of the received packet.
2056 In switch or hub modes ARP does work so the sender already knows the correct destination MAC address.
2057 In those modes every interface should have a unique MAC address, so make sure they are not the same.
2058 Because switch and hub modes rely on MAC addresses to function correctly,
2059 these modes cannot be used on the following operating systems which don't have a `tap' style virtual network device:
2060 OpenBSD, NetBSD, Darwin and Solaris.
2063 @c ==================================================================
2064 @node The meta-connection
2065 @subsection The meta-connection
2067 Having only a UDP connection available is not enough. Though suitable
2068 for transmitting data, we want to be able to reliably send other
2069 information, such as routing and session key information to somebody.
2072 TCP is a better alternative, because it already contains protection
2073 against information being lost, unlike UDP.
2075 So we establish two connections. One for the encrypted VPN data, and one
2076 for other information, the meta-data. Hence, we call the second
2077 connection the meta-connection. We can now be sure that the
2078 meta-information doesn't get lost on the way to another computer.
2080 @cindex data-protocol
2081 @cindex meta-protocol
2082 Like with any communication, we must have a protocol, so that everybody
2083 knows what everything stands for, and how she should react. Because we
2084 have two connections, we also have two protocols. The protocol used for
2085 the UDP data is the ``data-protocol,'' the other one is the
2088 The reason we don't use TCP for both protocols is that UDP is much
2089 better for encapsulation, even while it is less reliable. The real
2090 problem is that when TCP would be used to encapsulate a TCP stream
2091 that's on the private network, for every packet sent there would be
2092 three ACKs sent instead of just one. Furthermore, if there would be
2093 a timeout, both TCP streams would sense the timeout, and both would
2094 start re-sending packets.
2097 @c ==================================================================
2098 @node The meta-protocol
2099 @section The meta-protocol
2101 The meta protocol is used to tie all tinc daemons together, and
2102 exchange information about which tinc daemon serves which virtual
2105 The meta protocol consists of requests that can be sent to the other
2106 side. Each request has a unique number and several parameters. All
2107 requests are represented in the standard ASCII character set. It is
2108 possible to use tools such as telnet or netcat to connect to a tinc
2109 daemon started with the --bypass-security option
2110 and to read and write requests by hand, provided that one
2111 understands the numeric codes sent.
2113 The authentication scheme is described in @ref{Authentication protocol}. After a
2114 successful authentication, the server and the client will exchange all the
2115 information about other tinc daemons and subnets they know of, so that both
2116 sides (and all the other tinc daemons behind them) have their information
2123 ------------------------------------------------------------------
2124 ADD_EDGE node1 node2 21.32.43.54 655 222 0
2125 | | | | | +-> options
2126 | | | | +----> weight
2127 | | | +--------> UDP port of node2
2128 | | +----------------> real address of node2
2129 | +-------------------------> name of destination node
2130 +-------------------------------> name of source node
2132 ADD_SUBNET node 192.168.1.0/24
2133 | | +--> prefixlength
2134 | +--------> network address
2135 +------------------> owner of this subnet
2136 ------------------------------------------------------------------
2139 The ADD_EDGE messages are to inform other tinc daemons that a connection between
2140 two nodes exist. The address of the destination node is available so that
2141 VPN packets can be sent directly to that node.
2143 The ADD_SUBNET messages inform other tinc daemons that certain subnets belong
2144 to certain nodes. tinc will use it to determine to which node a VPN packet has
2151 ------------------------------------------------------------------
2152 DEL_EDGE node1 node2
2153 | +----> name of destination node
2154 +----------> name of source node
2156 DEL_SUBNET node 192.168.1.0/24
2157 | | +--> prefixlength
2158 | +--------> network address
2159 +------------------> owner of this subnet
2160 ------------------------------------------------------------------
2163 In case a connection between two daemons is closed or broken, DEL_EDGE messages
2164 are sent to inform the other daemons of that fact. Each daemon will calculate a
2165 new route to the the daemons, or mark them unreachable if there isn't any.
2172 ------------------------------------------------------------------
2173 REQ_KEY origin destination
2174 | +--> name of the tinc daemon it wants the key from
2175 +----------> name of the daemon that wants the key
2177 ANS_KEY origin destination 4ae0b0a82d6e0078 91 64 4
2178 | | \______________/ | | +--> MAC length
2179 | | | | +-----> digest algorithm
2180 | | | +--------> cipher algorithm
2181 | | +--> 128 bits key
2182 | +--> name of the daemon that wants the key
2183 +----------> name of the daemon that uses this key
2186 +--> daemon that has changed it's packet key
2187 ------------------------------------------------------------------
2190 The keys used to encrypt VPN packets are not sent out directly. This is
2191 because it would generate a lot of traffic on VPNs with many daemons, and
2192 chances are that not every tinc daemon will ever send a packet to every
2193 other daemon. Instead, if a daemon needs a key it sends a request for it
2194 via the meta connection of the nearest hop in the direction of the
2201 ------------------------------------------------------------------
2204 ------------------------------------------------------------------
2207 There is also a mechanism to check if hosts are still alive. Since network
2208 failures or a crash can cause a daemon to be killed without properly
2209 shutting down the TCP connection, this is necessary to keep an up to date
2210 connection list. PINGs are sent at regular intervals, except when there
2211 is also some other traffic. A little bit of salt (random data) is added
2212 with each PING and PONG message, to make sure that long sequences of PING/PONG
2213 messages without any other traffic won't result in known plaintext.
2215 This basically covers what is sent over the meta connection by tinc.
2218 @c ==================================================================
2224 Tinc got its name from ``TINC,'' short for @emph{There Is No Cabal}; the
2225 alleged Cabal was/is an organisation that was said to keep an eye on the
2226 entire Internet. As this is exactly what you @emph{don't} want, we named
2227 the tinc project after TINC.
2230 But in order to be ``immune'' to eavesdropping, you'll have to encrypt
2231 your data. Because tinc is a @emph{Secure} VPN (SVPN) daemon, it does
2232 exactly that: encrypt.
2233 Tinc by default uses blowfish encryption with 128 bit keys in CBC mode, 32 bit
2234 sequence numbers and 4 byte long message authentication codes to make sure
2235 eavesdroppers cannot get and cannot change any information at all from the
2236 packets they can intercept. The encryption algorithm and message authentication
2237 algorithm can be changed in the configuration. The length of the message
2238 authentication codes is also adjustable. The length of the key for the
2239 encryption algorithm is always the default length used by OpenSSL.
2242 * Authentication protocol::
2243 * Encryption of network packets::
2248 @c ==================================================================
2249 @node Authentication protocol
2250 @subsection Authentication protocol
2252 @cindex authentication
2253 A new scheme for authentication in tinc has been devised, which offers some
2254 improvements over the protocol used in 1.0pre2 and 1.0pre3. Explanation is
2264 --------------------------------------------------------------------------
2265 client <attempts connection>
2267 server <accepts connection>
2271 +-------> name of tinc daemon
2275 +-------> name of tinc daemon
2277 client META_KEY 5f0823a93e35b69e...7086ec7866ce582b
2278 \_________________________________/
2279 +-> RSAKEYLEN bits totally random string S1,
2280 encrypted with server's public RSA key
2282 server META_KEY 6ab9c1640388f8f0...45d1a07f8a672630
2283 \_________________________________/
2284 +-> RSAKEYLEN bits totally random string S2,
2285 encrypted with client's public RSA key
2288 - the client will symmetrically encrypt outgoing traffic using S1
2289 - the server will symmetrically encrypt outgoing traffic using S2
2291 client CHALLENGE da02add1817c1920989ba6ae2a49cecbda0
2292 \_________________________________/
2293 +-> CHALLEN bits totally random string H1
2295 server CHALLENGE 57fb4b2ccd70d6bb35a64c142f47e61d57f
2296 \_________________________________/
2297 +-> CHALLEN bits totally random string H2
2299 client CHAL_REPLY 816a86
2300 +-> 160 bits SHA1 of H2
2302 server CHAL_REPLY 928ffe
2303 +-> 160 bits SHA1 of H1
2305 After the correct challenge replies are received, both ends have proved
2306 their identity. Further information is exchanged.
2308 client ACK 655 123 0
2310 | +----> estimated weight
2311 +--------> listening port of client
2313 server ACK 655 321 0
2315 | +----> estimated weight
2316 +--------> listening port of server
2317 --------------------------------------------------------------------------
2320 This new scheme has several improvements, both in efficiency and security.
2322 First of all, the server sends exactly the same kind of messages over the wire
2323 as the client. The previous versions of tinc first authenticated the client,
2324 and then the server. This scheme even allows both sides to send their messages
2325 simultaneously, there is no need to wait for the other to send something first.
2326 This means that any calculations that need to be done upon sending or receiving
2327 a message can also be done in parallel. This is especially important when doing
2328 RSA encryption/decryption. Given that these calculations are the main part of
2329 the CPU time spent for the authentication, speed is improved by a factor 2.
2331 Second, only one RSA encrypted message is sent instead of two. This reduces the
2332 amount of information attackers can see (and thus use for a cryptographic
2333 attack). It also improves speed by a factor two, making the total speedup a
2336 Third, and most important:
2337 The symmetric cipher keys are exchanged first, the challenge is done
2338 afterwards. In the previous authentication scheme, because a man-in-the-middle
2339 could pass the challenge/chal_reply phase (by just copying the messages between
2340 the two real tinc daemons), but no information was exchanged that was really
2341 needed to read the rest of the messages, the challenge/chal_reply phase was of
2342 no real use. The man-in-the-middle was only stopped by the fact that only after
2343 the ACK messages were encrypted with the symmetric cipher. Potentially, it
2344 could even send it's own symmetric key to the server (if it knew the server's
2345 public key) and read some of the metadata the server would send it (it was
2346 impossible for the mitm to read actual network packets though). The new scheme
2347 however prevents this.
2349 This new scheme makes sure that first of all, symmetric keys are exchanged. The
2350 rest of the messages are then encrypted with the symmetric cipher. Then, each
2351 side can only read received messages if they have their private key. The
2352 challenge is there to let the other side know that the private key is really
2353 known, because a challenge reply can only be sent back if the challenge is
2354 decrypted correctly, and that can only be done with knowledge of the private
2357 Fourth: the first thing that is sent via the symmetric cipher encrypted
2358 connection is a totally random string, so that there is no known plaintext (for
2359 an attacker) in the beginning of the encrypted stream.
2362 @c ==================================================================
2363 @node Encryption of network packets
2364 @subsection Encryption of network packets
2367 A data packet can only be sent if the encryption key is known to both
2368 parties, and the connection is activated. If the encryption key is not
2369 known, a request is sent to the destination using the meta connection
2370 to retrieve it. The packet is stored in a queue while waiting for the
2374 The UDP packet containing the network packet from the VPN has the following layout:
2377 ... | IP header | UDP header | seqno | VPN packet | MAC | UDP trailer
2378 \___________________/\_____/
2380 V +---> digest algorithm
2381 Encrypted with symmetric cipher
2384 So, the entire VPN packet is encrypted using a symmetric cipher, including a 32 bits
2385 sequence number that is added in front of the actual VPN packet, to act as a unique
2386 IV for each packet and to prevent replay attacks. A message authentication code
2387 is added to the UDP packet to prevent alteration of packets. By default the
2388 first 4 bytes of the digest are used for this, but this can be changed using
2389 the MACLength configuration variable.
2391 @c ==================================================================
2392 @node Security issues
2393 @subsection Security issues
2395 In August 2000, we discovered the existence of a security hole in all versions
2396 of tinc up to and including 1.0pre2. This had to do with the way we exchanged
2397 keys. Since then, we have been working on a new authentication scheme to make
2398 tinc as secure as possible. The current version uses the OpenSSL library and
2399 uses strong authentication with RSA keys.
2401 On the 29th of December 2001, Jerome Etienne posted a security analysis of tinc
2402 1.0pre4. Due to a lack of sequence numbers and a message authentication code
2403 for each packet, an attacker could possibly disrupt certain network services or
2404 launch a denial of service attack by replaying intercepted packets. The current
2405 version adds sequence numbers and message authentication codes to prevent such
2408 On the 15th of September 2003, Peter Gutmann posted a security analysis of tinc
2409 1.0.1. He argues that the 32 bit sequence number used by tinc is not a good IV,
2410 that tinc's default length of 4 bytes for the MAC is too short, and he doesn't
2411 like tinc's use of RSA during authentication. We do not know of a security hole
2412 in this version of tinc, but tinc's security is not as strong as TLS or IPsec.
2413 We will address these issues in tinc 2.0.
2415 Cryptography is a hard thing to get right. We cannot make any
2416 guarantees. Time, review and feedback are the only things that can
2417 prove the security of any cryptographic product. If you wish to review
2418 tinc or give us feedback, you are stronly encouraged to do so.
2421 @c ==================================================================
2422 @node Platform specific information
2423 @chapter Platform specific information
2426 * Interface configuration::
2430 @c ==================================================================
2431 @node Interface configuration
2432 @section Interface configuration
2434 When configuring an interface, one normally assigns it an address and a
2435 netmask. The address uniquely identifies the host on the network attached to
2436 the interface. The netmask, combined with the address, forms a subnet. It is
2437 used to add a route to the routing table instructing the kernel to send all
2438 packets which fall into that subnet to that interface. Because all packets for
2439 the entire VPN should go to the virtual network interface used by tinc, the
2440 netmask should be such that it encompasses the entire VPN.
2444 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2446 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2447 @item Linux iproute2
2448 @tab @code{ip addr add} @var{address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2450 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2452 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2454 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2456 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2457 @item Darwin (MacOS/X)
2458 @tab @code{ifconfig} @var{interface} @var{address} @code{netmask} @var{netmask}
2460 @tab @code{netsh interface ip set address} @var{interface} @code{static} @var{address} @var{netmask}
2465 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2467 @tab @code{ifconfig} @var{interface} @code{add} @var{address}@code{/}@var{prefixlength}
2469 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2471 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2473 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2475 @tab @code{ifconfig} @var{interface} @code{inet6 plumb up}
2477 @tab @code{ifconfig} @var{interface} @code{inet6 addif} @var{address} @var{address}
2478 @item Darwin (MacOS/X)
2479 @tab @code{ifconfig} @var{interface} @code{inet6} @var{address} @code{prefixlen} @var{prefixlength}
2481 @tab @code{netsh interface ipv6 add address} @var{interface} @code{static} @var{address}/@var{prefixlength}
2484 On some platforms, when running tinc in switch mode, the VPN interface must be set to tap mode with an ifconfig command:
2486 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2488 @tab @code{ifconfig} @var{interface} @code{link0}
2491 On Linux, it is possible to create a persistent tun/tap interface which will
2492 continue to exist even if tinc quit, although this is normally not required.
2493 It can be useful to set up a tun/tap interface owned by a non-root user, so
2494 tinc can be started without needing any root privileges at all.
2496 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2498 @tab @code{ip tuntap add dev} @var{interface} @code{mode} @var{tun|tap} @code{user} @var{username}
2501 @c ==================================================================
2505 In some cases it might be necessary to add more routes to the virtual network
2506 interface. There are two ways to indicate which interface a packet should go
2507 to, one is to use the name of the interface itself, another way is to specify
2508 the (local) address that is assigned to that interface (@var{local_address}). The
2509 former way is unambiguous and therefore preferable, but not all platforms
2512 Adding routes to IPv4 subnets:
2514 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2516 @tab @code{route add -net} @var{network_address} @code{netmask} @var{netmask} @var{interface}
2517 @item Linux iproute2
2518 @tab @code{ip route add} @var{network_address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2520 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2522 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2524 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2526 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address} @code{-interface}
2527 @item Darwin (MacOS/X)
2528 @tab @code{route add} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2530 @tab @code{netsh routing ip add persistentroute} @var{network_address} @var{netmask} @var{interface} @var{local_address}
2533 Adding routes to IPv6 subnets:
2535 @multitable {Darwin (MacOS/X)} {ifconfig route add -bla network address netmask netmask prefixlength interface}
2537 @tab @code{route add -A inet6} @var{network_address}@code{/}@var{prefixlength} @var{interface}
2538 @item Linux iproute2
2539 @tab @code{ip route add} @var{network_address}@code{/}@var{prefixlength} @code{dev} @var{interface}
2541 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @var{local_address}
2543 @tab @code{route add -inet6} @var{network_address} @var{local_address} @code{-prefixlen} @var{prefixlength}
2545 @tab @code{route add -inet6} @var{network_address} @var{local_address} @code{-prefixlen} @var{prefixlength}
2547 @tab @code{route add -inet6} @var{network_address}@code{/}@var{prefixlength} @var{local_address} @code{-interface}
2548 @item Darwin (MacOS/X)
2551 @tab @code{netsh interface ipv6 add route} @var{network address}/@var{prefixlength} @var{interface}
2555 @c ==================================================================
2561 * Contact information::
2566 @c ==================================================================
2567 @node Contact information
2568 @section Contact information
2571 Tinc's website is at @url{http://www.tinc-vpn.org/},
2572 this server is located in the Netherlands.
2575 We have an IRC channel on the FreeNode and OFTC IRC networks. Connect to
2576 @uref{http://www.freenode.net/, irc.freenode.net}
2578 @uref{http://www.oftc.net/, irc.oftc.net}
2579 and join channel #tinc.
2582 @c ==================================================================
2587 @item Ivo Timmermans (zarq)
2588 @item Guus Sliepen (guus) (@email{guus@@tinc-vpn.org})
2591 We have received a lot of valuable input from users. With their help,
2592 tinc has become the flexible and robust tool that it is today. We have
2593 composed a list of contributions, in the file called @file{THANKS} in
2594 the source distribution.
2597 @c ==================================================================
2599 @unnumbered Concept Index
2601 @c ==================================================================
2605 @c ==================================================================