syncthing/cmd/strelaysrv/README.md

strelaysrv

This is the relay server for the syncthing project.

❗Warnings❗ - Read or regret

By default, all relay servers will join to the default public relay pool, which means that the relay server will be available for public use, and will consume your bandwidth helping others to connect.

If you wish to disable this behaviour, please specify the -pools="" argument.

Please note that strelaysrv is only usable by syncthing version v0.12 and onwards.

To run strelaysrv you need to have port 22067 available to the internet, which means you might need to port forward it and/or allow it through your firewall.

Furthermore, by default strelaysrv will also expose a /status HTTP endpoint on port 22070, which is used by the pool servers to read metrics of the strelaysrv, such as the current transfer rates, how many clients are connected, etc. If you wish this information to be available you may need to port forward and allow it through your firewall. This is not mandatory for the strelaysrv to function, and is used only to gather metrics and present them in the overview page of the pool server.

At the point of writing the endpoint output looks as follows:

{
    "bytesProxied": 0,
    "goArch": "amd64",
    "goMaxProcs": 1,
    "goNumRoutine": 13,
    "goOS": "linux",
    "goVersion": "go1.6",
    "kbps10s1m5m15m30m60m": [
        0,
        0,
        0,
        0,
        0,
        0
    ],
    "numActiveSessions": 0,
    "numConnections": 0,
    "numPendingSessionKeys": 2,
    "numProxies": 0,
    "options": {
        "global-rate": 0,
        "message-timeout": 60,
        "network-timeout": 120,
        "per-session-rate": 0,
        "ping-interval": 60,
        "pools": [
            "https://relays.syncthing.net/endpoint"
        ],
        "provided-by": ""
    },
    "startTime": "2016-03-06T12:53:07.090847749-05:00",
    "uptimeSeconds": 17
}

If you wish to disable the /status endpoint, provide -status-srv="" as one of the arguments when starting the strelaysrv.

Running for public use

Make sure you have a public IP with port 22067 open, or have forwarded port 22067 if you are behind a NAT.

Run the strelaysrv with no arguments (or -debug if you want more output), and that should be enough for the server to join the public relay pool. You should see a message saying:

2015/09/21 22:45:46 pool.go:60: Joined https://relays.syncthing.net/endpoint rejoining in 48m0s

See strelaysrv -help for other options, such as rate limits, timeout intervals, etc.

Running for private use

Once you've started the strelaysrv, it will generate a key pair and print a URI:

relay://:22067/?id=EZQOIDM-6DDD4ZI-DJ65NSM-4OQWRAT-EIKSMJO-OZ552BO-WQZEGYY-STS5RQM&pingInterval=1m0s&networkTimeout=2m0s&sessionLimitBps=0&globalLimitBps=0&statusAddr=:22070

This URI contains a partial address of the relay server, as well as its options which in the future may be taken into account when choosing the most suitable relay.

Because the -listen option was not used strelaysrv does not know its external IP, therefore you should replace the host part of the URI with your public IP address on which the strelaysrv will be available:

relay://192.0.2.1:22067/?id=EZQOIDM-6DDD4ZI-DJ65NSM-4OQWRAT-EIKSMJO-OZ552BO-WQZEGYY-STS5RQM&pingInterval=1m0s&networkTimeout=2m0s&sessionLimitBps=0&globalLimitBps=0&statusAddr=:22070

If you do not care about certificate pinning (improved security) or do not care about passing verbose settings to the clients, you can shorten the URL to just the host part:

relay://192.0.2.1:22067

This URI can then be used in syncthing clients as one of the relay servers by adding the URI to the "Sync Protocol Listen Address" field, under Actions and Settings.

See strelaysrv -help for other options, such as rate limits, timeout intervals, etc.

Other items available in this repo

testutil

A test utility which can be used to test the connectivity of a relay server. You need to generate two x509 key pairs (key.pem and cert.pem), one for the client and one for the server, in separate directories. Afterwards, start the client:

./testutil -relay="relay://192.0.2.1:22067" -keys=certs/client/ -join

This prints out the client ID:

2015/09/21 23:00:52 main.go:42: ID: BG2C5ZA-W7XPFDO-LH222Z6-65F3HJX-ADFTGRT-3SBFIGM-KV26O2Q-E5RMRQ2

In the other terminal run the following:

 ./testutil -relay="relay://192.0.2.1:22067" -keys=certs/server/ -connect=BG2C5ZA-W7XPFDO-LH222Z6-65F3HJX-ADFTGRT-3SBFIGM-KV26O2Q-E5RMRQ2

Which should then give you an interactive prompt, where you can type things in one terminal, and they get relayed to the other terminal.

Relay related libraries used by this repo

Relay protocol definition.

Available here

Relay client

Only used by the testutil.

Available here