Merge branch 'docs-docker-coturn' into 'next'

Docs: coturn instructions for docker

See merge request famedly/conduit!498

docker/README.md

@@ -76,7 +76,7 @@ to pass `-e CONDUIT_CONFIG=""` into your container. For an overview of possible
 
 If you just want to test Conduit for a short time, you can use the `--rm` flag, which will clean up everything related to your container after you stop it.
 
-## Docker-compose
+### Docker-compose
 
 If the `docker run` command is not for you or your setup, you can also use one of the provided `docker-compose` files.
 
@@ -161,3 +161,58 @@ So...step by step:
 
 6. Run `docker-compose up -d`
 7. Connect to your homeserver with your preferred client and create a user. You should do this immediately after starting Conduit, because the first created user is the admin.
+
+
+
+
+## Voice communication
+
+In order to make or receive calls, a TURN server is required. Conduit suggests using [Coturn](https://github.com/coturn/coturn) for this purpose, which is also available as a Docker image. Before proceeding with the software installation, it is essential to have the necessary configurations in place.
+
+### Configuration
+
+Create a configuration file called `coturn.conf` containing:
+
+```conf
+use-auth-secret
+static-auth-secret=<a secret key>
+realm=<your server domain>
+```
+A common way to generate a suitable alphanumeric secret key is by using `pwgen -s 64 1`.
+
+These same values need to be set in conduit. You can either modify conduit.toml to include these lines:
+```
+turn_uris = ["turn:<your server domain>?transport=udp", "turn:<your server domain>?transport=tcp"]
+turn_secret = "<secret key from coturn configuration>"
+```
+or append the following to the docker environment variables dependig on which configuration method you used earlier:
+```yml
+- CONDUIT_TURN_URIS=["turn:<your server domain>?transport=udp", "turn:<your server domain>?transport=tcp"]
+- CONDUIT_TURN_SECRET="<secret key from coturn configuration>
+```
+Restart Conduit to apply these changes.
+
+### Run
+Run the [Coturn](https://hub.docker.com/r/coturn/coturn) image using 
+```bash
+docker run -d --network=host -v $(pwd)/coturn.conf:/etc/coturn/turnserver.conf coturn/coturn
+```
+
+or docker-compose. For the latter, paste the following section into a file called `docker-compose.yml`
+and run `docker-compose up -d` in the same directory.
+
+```yml
+version: 3
+services:
+    turn:
+      container_name: coturn-server
+      image: docker.io/coturn/coturn
+      restart: unless-stopped
+      network_mode: "host"
+      volumes:
+        - ./coturn.conf:/etc/coturn/turnserver.conf
+```
+
+To understand why the host networking mode is used and explore alternative configuration options, please visit the following link: https://github.com/coturn/coturn/blob/master/docker/coturn/README.md.
+For security recommendations see Synapse's [Coturn documentation](https://github.com/matrix-org/synapse/blob/develop/docs/setup/turn/coturn.md#configuration).
+