Using the tinc command, an administrator of an existing VPN can generate
invitations for new nodes. The invitation is a small URL that can easily
be copy&pasted into email or live chat. Another person can have tinc
automatically setup the necessary configuration files and exchange keys
with the server, by only using the invitation URL.
The invitation protocol uses temporary ECDSA keys. The invitation URL
consists of the hostname and port of the server, a hash of the server's
temporary ECDSA key and a cookie. When the client wants to accept an
invitation, it also creates a temporary ECDSA key, connects to the server
and says it wants to accept an invitation. Both sides exchange their
temporary keys. The client verifies that the server's key matches the hash
in the invitation URL. After setting up an SPTPS connection using the
temporary keys, the client gives the cookie to the server. If the cookie
is valid, the server sends the client an invitation file containing the
client's new name and a copy of the server's host config file. If everything
is ok, the client will generate a long-term ECDSA key and send it to the
server, which will add it to a new host config file for the client.
The invitation protocol currently allows multiple host config files to be
send from the server to the client. However, the client filters out
most configuration variables for its own host configuration file. In
particular, it only accepts Name, Mode, Broadcast, ConnectTo, Subnet and
AutoConnect. Also, at the moment no tinc-up script is generated.
When an invitation has succesfully been accepted, the client needs to start
the tinc daemon manually.
There are several reasons for this:
- MacOS/X doesn't support polling the tap device using kqueue, requiring a
workaround to fall back to select().
- On Windows only sockets are properly handled, therefore tinc uses a second
thread that does a blocking ReadFile() on the TAP-Win32/64 device. However,
this does not mix well with libevent.
- Libevent, event just the core, is quite large, and although it is easy to get
and install on many platforms, it can be a burden.
- Libev is more lightweight and seems technically superior, but it doesn't
abstract away all the platform differences (for example, async events are not
supported on Windows).
When set to a non-zero value, tinc will try to maintain exactly that number of
meta connections to other nodes. If there are not enough connections, it will
periodically try to set up an outgoing connection to a random node. If there
are too many connections, it will periodically try to remove an outgoing
connection.
When the Proxy option is used, outgoing connections will be made via the
specified proxy. There is no support for authentication methods or for having
the proxy forward incoming connections, and there is no attempt to proxy UDP.
When the "Broadcast = direct" option is used, broadcast packets are not sent
and forwarded via the Minimum Spanning Tree to all nodes, but are sent directly
to all nodes that can be reached in one hop.
One use for this is to allow running ad-hoc routing protocols, such as OLSR, on
top of tinc.
When the Name starts with a $, the rest will be interpreted as the name of an
environment variable containing the real Name. When Name is $HOST, but this
environment variable does not exist, gethostname() will be used to set the
Name. In both cases, illegal characters will be converted to underscores.
DeviceType = multicast allows one to specify a multicast address and port with
a Device statement. Tinc will then read/send packets to that multicast group
instead of to a tun/tap device. This allows interaction with UML, QEMU and KVM
instances that are listening on the same group.
This allows tincctl to receive log messages from a running tincd,
independent of what is logged to syslog or to file. Tincctl can receive
debug messages with an arbitrary level.
This allows administrators who frequently want to work with one tinc
network to omit the -n option. Since the NETNAME variable is set by
tincd when executing scripts, this makes it slightly easier to use
tincctl from within scripts.
The Broadcast option can be used to cause tinc to drop all broadcast and
multicast packets. This option might be expanded in the future to selectively
allow only some broadcast packet types.
Tinc will now, by default, decrement the TTL field of incoming IPv4 and IPv6
packets, before forwarding them to the virtual network device or to another
node. Packets with a TTL value of zero will be dropped, and an ICMP Time
Exceeded message will be sent back.
This behaviour can be disabled using the DecrementTTL option.
Apart from the platform specific tun/tap driver, link with the dummy and
raw_socket devices, and optionally with support for UML and VDE devices.
At runtime, the DeviceType option can be used to select which driver to
use.
Instead of UNIX time, the log messages now start with the time in RFC3339
format, which human-readable and still easy for the computer to parse and sort.
The HUP signal will also cause the log file to be closed and reopened, which is
useful when log rotation is used. If there is an error while opening the log
file, this is logged to stderr.
With some exceptions, tinc only accepted host configuration options for the
local node from the corresponding host configuration file. Although this is
documented, many people expect that they can also put those options in
tinc.conf. Tinc now internally merges the contents of both tinc.conf and the
local host configuration file.
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.
This determines if and how incoming packets that are not meant for the local
node are forwarded. It can either be off, internal (tinc forwards them itself,
as in previous versions), or kernel (packets are always sent to the TUN/TAP
device, letting the kernel sort them out).
