146 lines
6.0 KiB
ReStructuredText
146 lines
6.0 KiB
ReStructuredText
.. _relaying:
|
|
|
|
Relaying
|
|
========
|
|
|
|
.. versionadded:: 0.12.0
|
|
|
|
Syncthing can bounce traffic via a *relay* when it's not possible to establish
|
|
a direct connection between two devices. There are a number of public relays
|
|
available for this purpose. The advantage is that it makes a connection
|
|
possible where it would otherwise not be; the downside is that the transfer rate
|
|
is much lower than a direct connection would allow.
|
|
|
|
Relaying is enabled by default but will only be used if two devices are unable
|
|
to communicate directly with each other. When connected via a relay, Syncthing
|
|
will periodically retry a direct connection and, if one is established, stop
|
|
communicating via the relay.
|
|
|
|
Security
|
|
--------
|
|
|
|
The connection between two devices is still end to end encrypted, the relay
|
|
only retransmits the encrypted data much like a router. However, a device must
|
|
register with a relay in order to be reachable over that relay, so the relay
|
|
knows your IP and device ID. In that respect it is similar to a discovery
|
|
server. The relay operator can see the amount of traffic flowing between
|
|
devices.
|
|
|
|
Running Your Own Relay
|
|
----------------------
|
|
|
|
Syncthing relies on a network of community-contributed relay servers. Anyone can
|
|
run a relay server, and it will automatically join the relay pool and be
|
|
available to Syncthing users. The current list of relays can be found at
|
|
https://relays.syncthing.net.
|
|
|
|
To run a relay of your own, you will first need a server. Running a relay from a
|
|
home computer is not recommended: the relay ideally needs to be running 24/7,
|
|
and home internet connections often have poor upload bandwidth.
|
|
|
|
The recommended specifications for a relay are:
|
|
|
|
========= ==============
|
|
CPU At least 1GHz
|
|
RAM At least 256MB
|
|
Bandwidth At least 1MBit/s in and out, the higher the better
|
|
Traffic At least 1TiB/month, the more the better
|
|
========= ==============
|
|
|
|
VPS's with these specs are available for about $5-$10/month.
|
|
|
|
Installing and Running
|
|
~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
Download the latest release of the `relay server <https://github.com/syncthing/relaysrv/releases>`__
|
|
for your operating system and architecture. Unpack the archive and save the
|
|
binary to a convenient place such as `/usr/local/bin`.
|
|
|
|
The relay server takes a number of options, some of which are important for
|
|
smooth operation::
|
|
|
|
$ relaysrv --help
|
|
Usage of relaysrv:
|
|
-debug
|
|
Enable debug output
|
|
-ext-address string
|
|
An optional address to advertising as being available on.
|
|
Allows listening on an unprivileged port with port forwarding from e.g.
|
|
443, and be connected to on port 443.
|
|
-global-rate int
|
|
Global rate limit, in bytes/s
|
|
-keys string
|
|
Directory where cert.pem and key.pem is stored (default ".")
|
|
-listen string
|
|
Protocol listen address (default ":22067")
|
|
-message-timeout duration
|
|
Maximum amount of time we wait for relevant messages to arrive (default 1m0s)
|
|
-network-timeout duration
|
|
Timeout for network operations between the client and the relay.
|
|
If no data is received between the client and the relay in this
|
|
period of time, the connection is terminated. Furthermore, if no
|
|
data is sent between either clients being relayed within this
|
|
period of time, the session is also terminated. (default 2m0s)
|
|
-per-session-rate int
|
|
Per session rate limit, in bytes/s
|
|
-ping-interval duration
|
|
How often pings are sent (default 1m0s)
|
|
-pools string
|
|
Comma separated list of relay pool addresses to join (default "https://relays.syncthing.net/endpoint")
|
|
-provided-by string
|
|
An optional description about who provides the relay
|
|
-status-srv string
|
|
Listen address for status service (blank to disable) (default ":22070")
|
|
|
|
Primarily, you need to decide on a directory to store the TLS key and
|
|
certificate and a listen port. The default listen port of 22067 works, but for
|
|
optimal compatibility a well known port for encrypted traffic such as 443 is
|
|
recommended. This may require additional setup to work without running
|
|
as root or a privileged user, see `Running on port 443 as an unprivileged user`_
|
|
below. In principle something similar to this should work on a Linux/Unix
|
|
system::
|
|
|
|
$ sudo useradd relaysrv
|
|
$ sudo mkdir /etc/relaysrv
|
|
$ sudo chown relaysrv /etc/relaysrv
|
|
$ sudo -u relaysrv /usr/local/bin/relaysrv -keys /etc/relaysrv
|
|
|
|
This creates a user ``relaysrv`` and a directory ``/etc/relaysrv`` to store
|
|
the keys. The keys are generated on first startup. The relay will join the
|
|
global relay pool, unless a ``-pools=""`` argument is given.
|
|
|
|
To make the relay server start automatically at boot, use the recommended
|
|
procedure for your operating system.
|
|
|
|
Running on port 443 as an unprivileged user
|
|
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
|
|
|
|
It is recommended that you run the relay on port 443 (or another port which is
|
|
commonly allowed through corporate firewalls), in order to maximise the chances
|
|
that people are able to connect. However, binding to ports below 1024 requires
|
|
root privileges, and running a relay as root is not recommended. Thankfully
|
|
there are a couple of approaches available to you.
|
|
|
|
One option is to run the relay on port 22067, and use an ``iptables`` rule
|
|
to forward traffic from port 443 to port 22067, for example::
|
|
|
|
iptables -t nat -A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
|
|
|
|
Or, if you're using ``ufw``, add the following to ``/etc/ufw/before.rules``::
|
|
|
|
*nat
|
|
:PREROUTING ACCEPT [0:0]
|
|
:POSTROUTING ACCEPT [0:0]
|
|
|
|
-A PREROUTING -i eth0 -p tcp --dport 443 -j REDIRECT --to-port 22067
|
|
|
|
COMMIT
|
|
|
|
You will need to start ``relaysrv`` with ``-ext-address ":443"``. This tells
|
|
``relaysrv`` that it can be contacted on port 443, even though it is listening
|
|
on port 22067. You will also need to let both port 443 and 22067 through your
|
|
firewall.
|
|
|
|
Another option is `described here <https://wiki.apache.org/httpd/NonRootPortBinding>`__,
|
|
although your milage may vary.
|