Explicitly mention that LibreSSL can be used as well.

[tinc] / doc / tinc.conf.5.in

.Dd 2016-04-11
.Dt TINC.CONF 5
.\" Manual page created by:
.\" Ivo Timmermans
.\" Guus Sliepen <guus@tinc-vpn.org>
.Sh NAME
.Nm tinc.conf
.Nd tinc daemon configuration
.Sh DESCRIPTION
The files in the
.Pa @sysconfdir@/tinc/
directory contain runtime and security information for the tinc daemon.
.Sh NETWORKS
To distinguish multiple instances of tinc running on one computer,
you can use the
.Fl n
option to assign a network name to each tinc daemon.
.Pp
The effect of this option is that the daemon will set its configuration root to
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa / ,
where 
.Ar NETNAME
is your argument to the
.Fl n
option.
You'll notice that messages appear in syslog as coming from
.Nm tincd. Ns Ar NETNAME ,
and on Linux, unless specified otherwise, the name of the virtual network interface will be the same as the network name.
.Pp
It is recommended that you use network names even if you run only one instance of tinc.
However, you can choose not to use the
.Fl n
option.
In this case, the network name would just be empty, and
.Nm tinc
now looks for files in
.Pa @sysconfdir@/tinc/ ,
instead of 
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa / ;
the configuration file should be
.Pa @sysconfdir@/tinc/tinc.conf ,
and the host configuration files are now expected to be in
.Pa @sysconfdir@/tinc/hosts/ .
.Sh NAMES
Each tinc daemon must have a name that is unique in the network which it will be part of.
The name will be used by other tinc daemons for identification.
The name has to be declared in the
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc.conf
file.
.Pp
To make things easy,
choose something that will give unique and easy to remember names to your tinc daemon(s).
You could try things like hostnames, owner surnames or location names.
However, you are only allowed to use alphanumerical characters (a-z, A-Z, and 0-9) and underscores (_) in the name.
.Sh INITIAL CONFIGURATION
If you have not configured tinc yet, you can easily create a basic configuration using the following command:
.Bd -literal -offset indent
.Nm tinc Fl n Ar NETNAME Li init Ar NAME
.Ed
.Pp
You can further change the configuration as needed either by manually editing the configuration files,
or by using
.Xr tinc 8 .
.Sh PUBLIC/PRIVATE KEYS
The
.Nm tinc Li init
command will have generated both RSA and Ed25519 public/private keypairs.
The private keys should be stored in files named
.Pa rsa_key.priv
and
.Pa ed25519_key.priv
in the directory
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /
The public keys should be stored in the host configuration file
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/ Ns Va NAME .
The RSA keys are used for backwards compatibility with tinc version 1.0.
If you are upgrading from version 1.0 to 1.1, you can keep the old configuration files,
but you will need to create Ed25519 keys using the following command:
.Bd -literal -offset indent
.Nm tinc Fl n Ar NETNAME Li generate-ed25519-keys
.Ed
.Sh SERVER CONFIGURATION
The server configuration of the daemon is done in the file
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc.conf .
This file consists of comments (lines started with a
.Li # )
or assignments in the form of:
.Pp
.Va Variable Li = Ar Value .
.Pp
The variable names are case insensitive, and any spaces, tabs,
newlines and carriage returns are ignored.
Note: it is not required that you put in the 
.Li =
sign, but doing so improves readability.
If you leave it out, remember to replace it with at least one space character.
.Pp
The server configuration is complemented with host specific configuration (see the next section).
Although all configuration options for the local host listed in this document can also be put in
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc.conf ,
it is recommended to put host specific configuration options in the host configuration file,
as this makes it easy to exchange with other nodes.
.Pp
You can edit the config file manually, but it is recommended that you use
.Xr tinc 8
to change configuration variables for you.
.Pp
Here are all valid variables, listed in alphabetical order.
The default value is given between parentheses.
.Bl -tag -width indent
.It Va AddressFamily Li = ipv4 | ipv6 | any Pq any
This option affects the address family of listening and outgoing sockets.
If
.Qq any
is selected, then depending on the operating system both IPv4 and IPv6 or just
IPv6 listening sockets will be created.
.It Va AutoConnect Li = yes | no Po no Pc Bq experimental
If set to yes,
.Nm tinc
will automatically set up meta connections to other nodes,
without requiring
.Va ConnectTo
variables.
.Pp
Note: it is not possible to connect to nodes using zero (system-assigned) ports in this way.
.It Va BindToAddress Li = Ar address Op Ar port
This is the same as
.Va ListenAddress ,
however the address given with the
.Va BindToAddress
option will also be used for outgoing connections. This is useful if your
computer has more than one IPv4 or IPv6 address, and you want 
.Nm tinc
to only use a specific one for outgoing packets.
.It Va BindToInterface Li = Ar interface Bq experimental
If your computer has more than one network interface,
.Nm tinc
will by default listen on all of them for incoming connections.
It is possible to bind only to a single interface with this variable.
.Pp
This option may not work on all platforms.
Also, on some platforms it will not actually bind to an interface,
but rather to the address that the interface has at the moment a socket is created.
.It Va Broadcast Li = no | mst | direct Po mst Pc Bq experimental
This option selects the way broadcast packets are sent to other daemons.
NOTE: all nodes in a VPN must use the same
.Va Broadcast
mode, otherwise routing loops can form.
.Bl -tag -width indent
.It no
Broadcast packets are never sent to other nodes.
.It mst
Broadcast packets are sent and forwarded via the VPN's Minimum Spanning Tree.
This ensures broadcast packets reach all nodes.
.It direct
Broadcast packets are sent directly to all nodes that can be reached directly.
Broadcast packets received from other nodes are never forwarded.
If the IndirectData option is also set, broadcast packets will only be sent to nodes which we have a meta connection to.
.El
.It Va BroadcastSubnet Li = Ar address Ns Op Li / Ns Ar prefixlength
Declares a broadcast subnet. Any packet with a destination address falling into such a subnet will be routed as a broadcast (provided all nodes have it declared).
This is most useful to declare subnet broadcast addresses (e.g. 10.42.255.255), otherwise
.Nm tinc
won't know what to do with them.
.Pp
Note that global broadcast addresses (MAC ff:ff:ff:ff:ff:ff, IPv4 255.255.255.255), as well as multicast space (IPv4 224.0.0.0/4, IPv6 ff00::/8) are always considered broadcast addresses and don't need to be declared.
.It Va ConnectTo Li = Ar name
Specifies which other tinc daemon to connect to on startup.
Multiple
.Va ConnectTo
variables may be specified,
in which case outgoing connections to each specified tinc daemon are made.
The names should be known to this tinc daemon
(i.e., there should be a host configuration file for the name on the
.Va ConnectTo
line).
.Pp
If you don't specify a host with
.Va ConnectTo
and don't enable
.Va AutoConnect ,
.Nm tinc
won't try to connect to other daemons at all,
and will instead just listen for incoming connections.
.It Va DecrementTTL Li = yes | no Po no Pc Bq experimental
When enabled,
.Nm tinc
will decrement the Time To Live field in IPv4 packets, or the Hop Limit field in IPv6 packets,
before forwarding a received packet to the virtual network device or to another node,
and will drop packets that have a TTL value of zero,
in which case it will send an ICMP Time Exceeded packet back.
.Pp
Do not use this option if you use switch mode and want to use IPv6.
.It Va Device Li = Ar device Po Pa /dev/tap0 , Pa /dev/net/tun No or other depending on platform Pc
The virtual network device to use.
.Nm tinc
will automatically detect what kind of device it is.
Note that you can only use one device per daemon.
Under Windows, use
.Va Interface
instead of
.Va Device .
The info pages of the tinc package contain more information
about configuring the virtual network device.
.It Va DeviceStandby Li = yes | no Po no Pc
When disabled,
.Nm tinc
calls tinc-up on startup, and tinc-down on shutdown. When enabled,
.Nm tinc
will only call tinc-up when at least one node is reachable, and will call tinc-down as soon as no nodes are reachable.
On Windows, this also determines when the virtual network interface "cable" is "plugged".
.It Va DeviceType Li = Ar type Pq platform dependent
The type of the virtual network device.
Tinc will normally automatically select the right type of tun/tap interface, and this option should not be used.
However, this option can be used to select one of the special interface types, if support for them is compiled in.
.Bl -tag -width indent
.It dummy
Use a dummy interface.
No packets are ever read or written to a virtual network device.
Useful for testing, or when setting up a node that only forwards packets for other nodes.
.It raw_socket
Open a raw socket, and bind it to a pre-existing
.Va Interface
(eth0 by default).
All packets are read from this interface.
Packets received for the local node are written to the raw socket.
However, at least on Linux, the operating system does not process IP packets destined for the local host.
.It multicast
Open a multicast UDP socket and bind it to the address and port (separated by spaces) and optionally a TTL value specified using
.Va Device .
Packets are read from and written to this multicast socket.
This can be used to connect to UML, QEMU or KVM instances listening on the same multicast address.
Do NOT connect multiple
.Nm tinc 
daemons to the same multicast address, this will very likely cause routing loops.
Also note that this can cause decrypted VPN packets to be sent out on a real network if misconfigured.
.It uml Pq not compiled in by default
Create a UNIX socket with the filename specified by
.Va Device ,
or
.Pa @localstatedir@/run/ Ns Ar NETNAME Ns Pa .umlsocket
if not specified.
.Nm tinc
will wait for a User Mode Linux instance to connect to this socket.
.It vde Pq not compiled in by default
Uses the libvdeplug library to connect to a Virtual Distributed Ethernet switch,
using the UNIX socket specified by
.Va Device ,
or
.Pa @localstatedir@/run/vde.ctl
if not specified.
.El
Also, in case tinc does not seem to correctly interpret packets received from the virtual network device,
it can be used to change the way packets are interpreted:
.Bl -tag -width indent
.It tun Pq BSD and Linux
Set type to tun.
Depending on the platform, this can either be with or without an address family header (see below).
.It tunnohead Pq BSD
Set type to tun without an address family header.
Tinc will expect packets read from the virtual network device to start with an IP header.
On some platforms IPv6 packets cannot be read from or written to the device in this mode.
.It tunifhead Pq BSD
Set type to tun with an address family header.
Tinc will expect packets read from the virtual network device
to start with a four byte header containing the address family,
followed by an IP header.
This mode should support both IPv4 and IPv6 packets.
.It utun Pq OS X
Set type to utun.
This is only supported on OS X version 10.6.8 and higher, but doesn't require the tuntaposx module.
This mode should support both IPv4 and IPv6 packets.
.It tap Pq BSD and Linux
Set type to tap.
Tinc will expect packets read from the virtual network device
to start with an Ethernet header.
.El
.It Va DirectOnly Li = yes | no Po no Pc Bq experimental
When this option is enabled, packets that cannot be sent directly to the destination node,
but which would have to be forwarded by an intermediate node, are dropped instead.
When combined with the IndirectData option,
packets for nodes for which we do not have a meta connection with are also dropped.
.It Va Ed25519PrivateKeyFile Li = Ar filename Po Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /ed25519_key.priv Pc
The file in which the private Ed25519 key of this tinc daemon resides.
This is only used if
.Va ExperimentalProtocol
is enabled.
.It Va ExperimentalProtocol Li = yes | no Pq yes
When this option is enabled, the SPTPS protocol will be used when connecting to nodes that also support it.
Ephemeral ECDH will be used for key exchanges,
and Ed25519 will be used instead of RSA for authentication.
When enabled, an Ed25519 key must have been generated before with
.Nm tinc generate-ed25519-keys .
.It Va Forwarding Li = off | internal | kernel Po internal Pc Bq experimental
This option selects the way indirect packets are forwarded.
.Bl -tag -width indent
.It off
Incoming packets that are not meant for the local node,
but which should be forwarded to another node, are dropped.
.It internal
Incoming packets that are meant for another node are forwarded by tinc internally.
.Pp
This is the default mode, and unless you really know you need another forwarding mode, don't change it.
.It kernel
Incoming packets are always sent to the TUN/TAP device, even if the packets are not for the local node.
This is less efficient, but allows the kernel to apply its routing and firewall rules on them,
and can also help debugging.
.El
.It Va Hostnames Li = yes | no Pq no
This option selects whether IP addresses (both real and on the VPN) should
be resolved. Since DNS lookups are blocking, it might affect tinc's
efficiency, even stopping the daemon for a few seconds every time it does
a lookup if your DNS server is not responding.
.Pp
This does not affect resolving hostnames to IP addresses from the
host configuration files, but whether hostnames should be resolved while logging.
.It Va IffOneQueue Li = yes | no Po no Pc Bq experimental
(Linux only) Set IFF_ONE_QUEUE flag on TUN/TAP devices.
.It Va Interface Li = Ar interface
Defines the name of the interface corresponding to the virtual network device.
Depending on the operating system and the type of device this may or may not actually set the name of the interface.
Under Windows, this variable is used to select which network interface will be used.
If you specified a
.Va Device ,
this variable is almost always already correctly set.
.It Va KeyExpire Li = Ar seconds Pq 3600
This option controls the period the encryption keys used to encrypt the data are valid.
It is common practice to change keys at regular intervals to make it even harder for crackers,
even though it is thought to be nearly impossible to crack a single key.
.It Va ListenAddress Li = Ar address Op Ar port
If your computer has more than one IPv4 or IPv6 address,
.Nm tinc
will by default listen on all of them for incoming connections.
This option can be used to restrict which addresses tinc listens on.
Multiple
.Va ListenAddress
variables may be specified,
in which case listening sockets for each specified address are made.
.Pp
If no
.Ar port
is specified, the socket will listen on the port specified by the
.Va Port
option, or to port 655 if neither is given.
To only listen on a specific port but not on a specific address, use
.Li *
for the
.Ar address .
.Pp
If
.Ar port
is set to zero, it will be randomly assigned by the system. This is useful to randomize source ports of UDP packets, which can improve UDP hole punching reliability. In this case it is recommended to set
.Va AddressFamily
as well, otherwise
.Nm tinc
will assign different ports to different address families but other nodes can only know of one.
.It Va LocalDiscovery Li = yes | no Pq yes
When enabled,
.Nm tinc
will try to detect peers that are on the same local network.
This will allow direct communication using LAN addresses, even if both peers are behind a NAT
and they only ConnectTo a third node outside the NAT,
which normally would prevent the peers from learning each other's LAN address.
.Pp
Currently, local discovery is implemented by sending some packets to the local address of the node during UDP discovery. This will not work with old nodes that don't transmit their local address.
.It Va MACExpire Li = Ar seconds Pq 600
This option controls the amount of time MAC addresses are kept before they are removed.
This only has effect when
.Va Mode
is set to
.Qq switch .
.It Va MaxConnectionBurst Li = Ar count Pq 100
This option controls how many connections tinc accepts in quick succession.
If there are more connections than the given number in a short time interval,
tinc will reduce the number of accepted connections to only one per second,
until the burst has passed.
.It Va MaxTimeout Li = Ar seconds Pq 900
This is the maximum delay before trying to reconnect to other tinc daemons.
.It Va Mode Li = router | switch | hub Pq router
This option selects the way packets are routed to other daemons.
.Bl -tag -width indent
.It router
In this mode
.Va Subnet
variables in the host configuration files will be used to form a routing table.
Only packets of routable protocols (IPv4 and IPv6) are supported in this mode.
.Pp
This is the default mode, and unless you really know you need another mode, don't change it.
.It switch
In this mode the MAC addresses of the packets on the VPN will be used to
dynamically create a routing table just like an Ethernet switch does.
Unicast, multicast and broadcast packets of every protocol that runs over Ethernet are supported in this mode
at the cost of frequent broadcast ARP requests and routing table updates.
.Pp
This mode is primarily useful if you want to bridge Ethernet segments.
.It hub
This mode is almost the same as the switch mode, but instead
every packet will be broadcast to the other daemons
while no routing table is managed.
.El
.It Va Name Li = Ar name Bq required
This is the name which identifies this tinc daemon.
It must be unique for the virtual private network this daemon will connect to.
.Va Name
may only consist of alphanumeric and underscore characters (a-z, A-Z, 0-9 and _), and is case sensitive.
If 
.Va Name
starts with a
.Li $ ,
then the contents of the environment variable that follows will be used.
In that case, invalid characters will be converted to underscores.
If
.Va Name
is
.Li $HOST ,
but no such environment variable exist, the hostname will be read using the gethostname() system call.
.It Va PingInterval Li = Ar seconds Pq 60
The number of seconds of inactivity that
.Nm tinc
will wait before sending a probe to the other end.
.It Va PingTimeout Li = Ar seconds Pq 5
The number of seconds to wait for a response to pings or to allow meta
connections to block. If the other end doesn't respond within this time,
the connection is terminated,
and the others will be notified of this.
.It Va PriorityInheritance Li = yes | no Po no Pc Bq experimental
When this option is enabled the value of the TOS field of tunneled IPv4 packets
will be inherited by the UDP packets that are sent out.
.It Va PrivateKey Li = Ar key Bq obsolete
The private RSA key of this tinc daemon.
It will allow this tinc daemon to authenticate itself to other daemons.
.It Va PrivateKeyFile Li = Ar filename Po Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /rsa_key.priv Pc
The file in which the private RSA key of this tinc daemon resides.
.It Va ProcessPriority Li = low | normal | high
When this option is used the priority of the 
.Nm tincd
process will be adjusted.
Increasing the priority may help to reduce latency and packet loss on the VPN.
.It Va Proxy Li = socks4 | socks5 | http | exec Ar ... Bq experimental
Use a proxy when making outgoing connections.
The following proxy types are currently supported:
.Bl -tag -width indent
.It socks4 Ar address Ar port Op Ar username
Connects to the proxy using the SOCKS version 4 protocol.
Optionally, a
.Ar username
can be supplied which will be passed on to the proxy server.
Only IPv4 connections can be proxied using SOCKS 4.
.It socks5 Ar address Ar port Op Ar username Ar password
Connect to the proxy using the SOCKS version 5 protocol.
If a
.Ar username
and
.Ar password
are given, basic username/password authentication will be used,
otherwise no authentication will be used.
.It http Ar address Ar port
Connects to the proxy and sends a HTTP CONNECT request.
.It exec Ar command
Executes the given
.Ar command
which should set up the outgoing connection.
The environment variables
.Ev NAME ,
.Ev NODE ,
.Ev REMOTEADDRES
and
.Ev REMOTEPORT
are available.
.El
.It Va ReplayWindow Li = Ar bytes Pq 32
This is the size of the replay tracking window for each remote node, in bytes.
The window is a bitfield which tracks 1 packet per bit, so for example
the default setting of 32 will track up to 256 packets in the window. In high
bandwidth scenarios, setting this to a higher value can reduce packet loss from
the interaction of replay tracking with underlying real packet loss and/or
reordering. Setting this to zero will disable replay tracking completely and
pass all traffic, but leaves tinc vulnerable to replay-based attacks on your
traffic.
.It Va StrictSubnets Li = yes | no Po no Pc Bq experimental
When this option is enabled tinc will only use Subnet statements which are
present in the host config files in the local
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/
directory. Subnets learned via connections to other nodes and which are not
present in the local host config files are ignored.
.It Va TunnelServer Li = yes | no Po no Pc Bq experimental
When this option is enabled tinc will no longer forward information between other tinc daemons,
and will only allow connections with nodes for which host config files are present in the local
.Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/
directory.
Setting this options also implicitly sets StrictSubnets.
.It Va UDPDiscovery Li = yes | no Po yes Pc
When this option is enabled tinc will try to establish UDP connectivity to nodes,
using TCP while it determines if a node is reachable over UDP. If it is disabled,
tinc always assumes a node is reachable over UDP.
Note that tinc will never use UDP with nodes that have
.Va TCPOnly
enabled.
.It Va UDPDiscoveryKeepaliveInterval Li = Ar seconds Pq 9
The minimum amount of time between sending UDP ping datagrams to check UDP connectivity once it has been established.
Note that these pings are large, since they are used to verify link MTU as well.
.It Va UDPDiscoveryInterval Li = Ar seconds Pq 2
The minimum amount of time between sending UDP ping datagrams to try to establish UDP connectivity.
.It Va UDPDiscoveryTimeout Li = Ar seconds Pq 30
If tinc doesn't receive any UDP ping replies over the specified interval,
it will assume UDP communication is broken and will fall back to TCP.
.It Va UDPInfoInterval Li = Ar seconds Pq 5
The minimum amount of time between sending periodic updates about UDP addresses, which are mostly useful for UDP hole punching.
.It Va UDPRcvBuf Li = Ar bytes Pq 1048576
Sets the socket receive buffer size for the UDP socket, in bytes.
If set to zero, the default buffer size will be used by the operating system.
Note: this setting can have a significant impact on performance, especially raw throughput.
.It Va UDPSndBuf Li = Ar bytes Pq 1048576
Sets the socket send buffer size for the UDP socket, in bytes.
If set to zero, the default buffer size will be used by the operating system.
Note: this setting can have a significant impact on performance, especially raw throughput.
.It Va UPnP Li = yes | udponly | no Po no Pc
If this option is enabled then tinc will search for UPnP-IGD devices on the local network.
It will then create and maintain port mappings for tinc's listening TCP and UDP ports.
If set to "udponly", tinc will only create a mapping for its UDP (data) port, not for its TCP (metaconnection) port.
Note that tinc must have been built with miniupnpc support for this feature to be available.
Furthermore, be advised that enabling this can have security implications, because the miniupnpc library that
tinc uses might not be well-hardened with regard to malicious UPnP replies.
.It Va UPnPDiscoverWait Li = Ar seconds Pq 5
The amount of time to wait for replies when probing the local network for UPnP devices.
.It Va UPnPRefreshPeriod Li = Ar seconds Pq 60
How often tinc will re-add the port mapping, in case it gets reset on the UPnP device. This also controls the duration of the port mapping itself, which will be set to twice that duration.
.El
.Sh HOST CONFIGURATION FILES
The host configuration files contain all information needed
to establish a connection to those hosts.
A host configuration file is also required for the local tinc daemon,
it will use it to read in it's listen port, public key and subnets.
.Pp
The idea is that these files are portable.
You can safely mail your own host configuration file to someone else.
That other person can then copy it to his own hosts directory,
and now his tinc daemon will be able to connect to your tinc daemon.
Since host configuration files only contain public keys,
no secrets are revealed by sending out this information.
.Bl -tag -width indent
.It Va Address Li = Ar address Oo Ar port Oc Bq recommended
The IP address or hostname of this tinc daemon on the real network.
This will only be used when trying to make an outgoing connection to this tinc daemon.
Optionally, a port can be specified to use for this address.
Multiple
.Va Address
variables can be specified, in which case each address will be tried until a working
connection has been established.
.It Va Cipher Li = Ar cipher Pq blowfish
The symmetric cipher algorithm used to encrypt UDP packets.
Any cipher supported by LibreSSL or OpenSSL is recognised.
Furthermore, specifying
.Qq none
will turn off packet encryption.
It is best to use only those ciphers which support CBC mode.
This option has no effect for connections between nodes using
.Va ExperimentalProtocol .
.It Va ClampMSS Li = yes | no Pq yes
This option specifies whether tinc should clamp the maximum segment size (MSS)
of TCP packets to the path MTU. This helps in situations where ICMP
Fragmentation Needed or Packet too Big messages are dropped by firewalls.
.It Va Compression Li = Ar level Pq 0
This option sets the level of compression used for UDP packets.
Possible values are 0 (off), 1 (fast zlib) and any integer up to 9 (best zlib),
10 (fast lzo) and 11 (best lzo).
.It Va Digest Li = Ar digest Pq sha1
The digest algorithm used to authenticate UDP packets.
Any digest supported by LibreSSL or OpenSSL is recognised.
Furthermore, specifying
.Qq none
will turn off packet authentication.
This option has no effect for connections between nodes using
.Va ExperimentalProtocol .
.It Va IndirectData Li = yes | no Pq no
When set to yes, only nodes which already have a meta connection to you
will try to establish direct communication with you.
It is best to leave this option out or set it to no.
.It Va MACLength Li = Ar length Pq 4
The length of the message authentication code used to authenticate UDP packets.
Can be anything from
.Qq 0
up to the length of the digest produced by the digest algorithm.
This option has no effect for connections between nodes using
.Va ExperimentalProtocol .
.It Va PMTU Li = Ar mtu Po 1514 Pc
This option controls the initial path MTU to this node.
.It Va PMTUDiscovery Li = yes | no Po yes Pc
When this option is enabled, tinc will try to discover the path MTU to this node.
After the path MTU has been discovered, it will be enforced on the VPN.
.It Va MTUInfoInterval Li = Ar seconds Pq 5
The minimum amount of time between sending periodic updates about relay path MTU. Useful for quickly determining MTU to indirect nodes.
.It Va Port Li = Ar port Pq 655
The port number on which this tinc daemon is listening for incoming connections,
which is used if no port number is specified in an
.Va Address
statement.
.Pp
If this is set to zero, the port will be randomly assigned by the system. This is useful to randomize source ports of UDP packets, which can improve UDP hole punching reliability. When setting
.Va Port
to zero it is recommended to set
.Va AddressFamily
as well, otherwise
.Nm tinc
will assign different ports to different address families but other nodes can only know of one.
.It Va PublicKey Li = Ar key Bq obsolete
The public RSA key of this tinc daemon.
It will be used to cryptographically verify it's identity and to set up a secure connection.
.It Va PublicKeyFile Li = Ar filename Bq obsolete
The file in which the public RSA key of this tinc daemon resides.
.Pp
From version 1.0pre4 on
.Nm tinc
will store the public key directly into the host configuration file in PEM format,
the above two options then are not necessary.
Either the PEM format is used, or exactly one of the above two options must be specified
in each host configuration file,
if you want to be able to establish a connection with that host.
.It Va Subnet Li = Ar address Ns Op Li / Ns Ar prefixlength Ns Op Li # Ns Ar weight
The subnet which this tinc daemon will serve.
.Nm tinc
tries to look up which other daemon it should send a packet to by searching the appropriate subnet.
If the packet matches a subnet,
it will be sent to the daemon who has this subnet in his host configuration file.
Multiple
.Va Subnet
variables can be specified.
.Pp
Subnets can either be single MAC, IPv4 or IPv6 addresses,
in which case a subnet consisting of only that single address is assumed,
or they can be a IPv4 or IPv6 network address with a prefixlength.
For example, IPv4 subnets must be in a form like 192.168.1.0/24,
where 192.168.1.0 is the network address and 24 is the number of bits set in the netmask.
Note that subnets like 192.168.1.1/24 are invalid!
Read a networking HOWTO/FAQ/guide if you don't understand this.
IPv6 subnets are notated like fec0:0:0:1::/64.
MAC addresses are notated like 0:1a:2b:3c:4d:5e.
.Pp
A Subnet can be given a weight to indicate its priority over identical Subnets
owned by different nodes. The default weight is 10. Lower values indicate
higher priority. Packets will be sent to the node with the highest priority,
unless that node is not reachable, in which case the node with the next highest
priority will be tried, and so on.
.It Va TCPOnly Li = yes | no Pq no Bq obsolete
If this variable is set to yes,
then the packets are tunnelled over the TCP connection instead of a UDP connection.
This is especially useful for those who want to run a tinc daemon
from behind a masquerading firewall,
or if UDP packet routing is disabled somehow.
Setting this options also implicitly sets IndirectData.
.Pp
Since version 1.0.10, tinc will automatically detect whether communication via
UDP is possible or not.
.It Va Weight Li = Ar weight
If this variable is set, it overrides the weight given to connections made with
another host. A higher
.Ar weight
means a lower priority is given to this connection when broadcasting or
forwarding packets.
.El
.Sh SCRIPTS
Apart from reading the server and host configuration files,
tinc can also run scripts at certain moments.
Below is a list of filenames of scripts and a description of when they are run.
A script is only run if it exists and if it is executable.
.Pp
Scripts are run synchronously;
this means that tinc will temporarily stop processing packets until the called script finishes executing.
This guarantees that scripts will execute in the exact same order as the events that trigger them.
If you need to run commands asynchronously, you have to ensure yourself that they are being run in the background.
.Pp
Under Windows (not Cygwin), the scripts must have the extension
.Pa .bat
or
.Pa .cmd .
.Bl -tag -width indent
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc-up
This is the most important script.
If it is present it will be executed right after the tinc daemon has been started and has connected to the virtual network device (or when the first node becomes reachable if
.Va DeviceStandby
is used).
It should be used to set up the corresponding network interface,
but can also be used to start other things.
.Pp
Under Windows you can use the Network Connections control panel instead of creating this script.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc-down
This script is started right before the tinc daemon quits (or when the last node becomes unreachable if
.Va DeviceStandby
is used).
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/ Ns Ar HOST Ns Pa -up
This script is started when the tinc daemon with name
.Ar HOST
becomes reachable.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/ Ns Ar HOST Ns Pa -down
This script is started when the tinc daemon with name
.Ar HOST
becomes unreachable.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /host-up
This script is started when any host becomes reachable.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /host-down
This script is started when any host becomes unreachable.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /subnet-up
This script is started when a Subnet becomes reachable.
The Subnet and the node it belongs to are passed in environment variables.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /subnet-down
This script is started when a Subnet becomes unreachable.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /invitation-created
This script is started when a new invitation has been created.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /invitation-accepted
This script is started when an invitation has been used.
.El
.Pp
The scripts are started without command line arguments, but can make use of certain environment variables.
Under UNIX like operating systems the names of environment variables must be preceded by a
.Li $ 
in scripts.
Under Windows, in
.Pa .bat
or
.Pa .cmd
files, they have to be put between
.Li %
signs.
.Bl -tag -width indent
.It Ev NETNAME
If a netname was specified, this environment variable contains it.
.It Ev NAME
Contains the name of this tinc daemon.
.It Ev DEVICE
Contains the name of the virtual network device that tinc uses.
.It Ev INTERFACE
Contains the name of the virtual network interface that tinc uses.
This should be used for commands like
.Pa ifconfig .
.It Ev NODE
When a host becomes (un)reachable, this is set to its name.
If a subnet becomes (un)reachable, this is set to the owner of that subnet.
.It Ev REMOTEADDRESS
When a host becomes (un)reachable, this is set to its real address.
.It Ev REMOTEPORT
When a host becomes (un)reachable, this is set to the port number it uses for communication with other tinc daemons.
.It Ev SUBNET
When a subnet becomes (un)reachable, this is set to the subnet.
.It Ev WEIGHT
When a subnet becomes (un)reachable, this is set to the subnet weight.
.It Ev INVITATION_FILE
When the
.Pa invitation-created
script is called, this is set to the file where the invitation details will be stored.
.It Ev INVITATION_URL
When the
.Pa invitation-created
script is called, this is set to the invitation URL that has been created.
.El
.Pp
Do not forget that under UNIX operating systems, you have to make the scripts executable, using the command
.Nm chmod Li a+x Pa script .
.Sh FILES
The most important files are:
.Bl -tag -width indent
.It Pa @sysconfdir@/tinc/
The top directory for configuration files.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc.conf
The default name of the server configuration file for net
.Ar NETNAME .
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /conf.d/
Optional directory from which any .conf file will be loaded
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /hosts/
Host configuration files are kept in this directory.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc-up
If an executable file with this name exists,
it will be executed right after the tinc daemon has connected to the virtual network device.
It can be used to set up the corresponding network interface.
.It Pa @sysconfdir@/tinc/ Ns Ar NETNAME Ns Pa /tinc-down
If an executable file with this name exists,
it will be executed right before the tinc daemon is going to close
its connection to the virtual network device.
.El
.Sh SEE ALSO
.Xr tincd 8 ,
.Xr tinc 8 ,
.Pa http://www.tinc-vpn.org/ ,
.Pa http://www.tldp.org/LDP/nag2/ .
.Pp
The full documentation for
.Nm tinc
is maintained as a Texinfo manual.
If the info and tinc programs are properly installed at your site, the command
.Ic info tinc
should give you access to the complete manual.
.Pp
.Nm tinc
comes with ABSOLUTELY NO WARRANTY.
This is free software, and you are welcome to redistribute it under certain conditions;
see the file COPYING for details.