Include additional TURN server example into documentation (#14293)

* Include eturnal TURN server configuration example

and moving specific configuration examples into sub folders.

* Update docs/turn-howto.md

Co-authored-by: Dirk Klimpel <5740567+dklimpel@users.noreply.github.com>

* Update docs/setup/turn/coturn.md

Co-authored-by: Dirk Klimpel <5740567+dklimpel@users.noreply.github.com>

* Update docs/setup/turn/eturnal.md

Co-authored-by: Dirk Klimpel <5740567+dklimpel@users.noreply.github.com>

* Fix TURN relaying public IP address hint

* lint eturnal installation commands

* Adjust synapse setup to link to existing documentation

..avoid redundant information.

* remove redundant text

* include alpine linux package link

* Create 14293.doc

* Update 14293.doc

add missing dot

* Update docs/setup/turn/eturnal.md

Co-authored-by: reivilibre <olivier@librepush.net>

* Update docs/setup/turn/eturnal.md

Co-authored-by: reivilibre <olivier@librepush.net>

* Update docs/setup/turn/coturn.md

Co-authored-by: Moritz Dietz <moritzdietz@users.noreply.github.com>

* Update docs/setup/turn/coturn.md

Co-authored-by: Moritz Dietz <moritzdietz@users.noreply.github.com>

* Update docs/setup/turn/coturn.md

Co-authored-by: Moritz Dietz <moritzdietz@users.noreply.github.com>

* Update docs/setup/turn/eturnal.md

Co-authored-by: reivilibre <olivier@librepush.net>

* Update docs/setup/turn/coturn.md

Co-authored-by: Moritz Dietz <moritzdietz@users.noreply.github.com>

* Update docs/setup/turn/coturn.md

Co-authored-by: Moritz Dietz <moritzdietz@users.noreply.github.com>

* Update eturnal.md to link to official documentation

... and to simplify some aspects

* Adjust coturn to link to default prefix

* Mention eturnalctl location

* Update docs/turn-howto.md

Co-authored-by: Saarko <sandomir@tutanotal.com>
Co-authored-by: Dirk Klimpel <5740567+dklimpel@users.noreply.github.com>
Co-authored-by: reivilibre <olivier@librepush.net>
Co-authored-by: Moritz Dietz <moritzdietz@users.noreply.github.com>

5 files changed, 390 insertions, 211 deletions

diff --git a/changelog.d/14293.doc b/changelog.d/14293.doc
new file mode 100644
index 0000000000..d6410421e7
--- /dev/null
+++ b/changelog.d/14293.doc
@@ -0,0 +1 @@
+Add addtional TURN server configuration example based on [eturnal](https://github.com/processone/eturnal) and adjust general TURN server doc structure.
diff --git a/docs/SUMMARY.md b/docs/SUMMARY.md
index 16720bceb5..8d68719958 100644
--- a/docs/SUMMARY.md
+++ b/docs/SUMMARY.md
@@ -9,6 +9,8 @@
   - [Configuring a Reverse Proxy](reverse_proxy.md)
   - [Configuring a Forward/Outbound Proxy](setup/forward_proxy.md)
   - [Configuring a Turn Server](turn-howto.md)
+    - [coturn TURN server](setup/turn/coturn.md)
+    - [eturnal TURN server](setup/turn/eturnal.md)
   - [Delegation](delegate.md)
 
 # Upgrading
diff --git a/docs/setup/turn/coturn.md b/docs/setup/turn/coturn.md
new file mode 100644
index 0000000000..a1bb1e934c
--- /dev/null
+++ b/docs/setup/turn/coturn.md
@@ -0,0 +1,188 @@
+# coturn TURN server
+
+The following sections describe how to install [coturn](<https://github.com/coturn/coturn>) (which implements the TURN REST API).
+
+## `coturn` setup
+
+### Initial installation
+
+The TURN daemon `coturn` is available from a variety of sources such as native package managers, or installation from source.
+
+#### Debian and Ubuntu based distributions
+
+Just install the debian package:
+
+```sh
+sudo apt install coturn
+```
+
+This will install and start a systemd service called `coturn`.
+
+#### Source installation
+
+1. Download the [latest release](https://github.com/coturn/coturn/releases/latest) from github.  Unpack it and `cd` into the directory.
+
+1.  Configure it:
+
+    ```sh
+    ./configure
+    ```
+
+    You may need to install `libevent2`: if so, you should do so in
+    the way recommended by your operating system. You can ignore
+    warnings about lack of database support: a database is unnecessary
+    for this purpose.
+
+1.  Build and install it:
+
+    ```sh
+    make
+    sudo make install
+    ```
+
+### Configuration
+
+1.  Create or edit the config file in `/etc/turnserver.conf`. The relevant
+    lines, with example values, are:
+
+    ```
+    use-auth-secret
+    static-auth-secret=[your secret key here]
+    realm=turn.myserver.org
+    ```
+
+    See `turnserver.conf` for explanations of the options. One way to generate
+    the `static-auth-secret` is with `pwgen`:
+
+    ```sh
+    pwgen -s 64 1
+    ```
+
+    A `realm` must be specified, but its value is somewhat arbitrary. (It is
+    sent to clients as part of the authentication flow.) It is conventional to
+    set it to be your server name.
+
+1.  You will most likely want to configure `coturn` to write logs somewhere. The
+    easiest way is normally to send them to the syslog:
+
+    ```sh
+    syslog
+    ```
+
+    (in which case, the logs will be available via `journalctl -u coturn` on a
+    systemd system). Alternatively, `coturn` can be configured to write to a
+    logfile - check the example config file supplied with `coturn`.
+
+1.  Consider your security settings. TURN lets users request a relay which will
+    connect to arbitrary IP addresses and ports. The following configuration is
+    suggested as a minimum starting point:
+
+    ```
+    # VoIP traffic is all UDP. There is no reason to let users connect to arbitrary TCP endpoints via the relay.
+    no-tcp-relay
+
+    # don't let the relay ever try to connect to private IP address ranges within your network (if any)
+    # given the turn server is likely behind your firewall, remember to include any privileged public IPs too.
+    denied-peer-ip=10.0.0.0-10.255.255.255
+    denied-peer-ip=192.168.0.0-192.168.255.255
+    denied-peer-ip=172.16.0.0-172.31.255.255
+
+    # recommended additional local peers to block, to mitigate external access to internal services.
+    # https://www.rtcsec.com/article/slack-webrtc-turn-compromise-and-bug-bounty/#how-to-fix-an-open-turn-relay-to-address-this-vulnerability
+    no-multicast-peers
+    denied-peer-ip=0.0.0.0-0.255.255.255
+    denied-peer-ip=100.64.0.0-100.127.255.255
+    denied-peer-ip=127.0.0.0-127.255.255.255
+    denied-peer-ip=169.254.0.0-169.254.255.255
+    denied-peer-ip=192.0.0.0-192.0.0.255
+    denied-peer-ip=192.0.2.0-192.0.2.255
+    denied-peer-ip=192.88.99.0-192.88.99.255
+    denied-peer-ip=198.18.0.0-198.19.255.255
+    denied-peer-ip=198.51.100.0-198.51.100.255
+    denied-peer-ip=203.0.113.0-203.0.113.255
+    denied-peer-ip=240.0.0.0-255.255.255.255
+
+    # special case the turn server itself so that client->TURN->TURN->client flows work
+    # this should be one of the turn server's listening IPs
+    allowed-peer-ip=10.0.0.1
+
+    # consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
+    user-quota=12 # 4 streams per video call, so 12 streams = 3 simultaneous relayed calls per user.
+    total-quota=1200
+    ```
+
+1.  Also consider supporting TLS/DTLS. To do this, add the following settings
+    to `turnserver.conf`:
+
+    ```
+    # TLS certificates, including intermediate certs.
+    # For Let's Encrypt certificates, use `fullchain.pem` here.
+    cert=/path/to/fullchain.pem
+
+    # TLS private key file
+    pkey=/path/to/privkey.pem
+
+    # Ensure the configuration lines that disable TLS/DTLS are commented-out or removed
+    #no-tls
+    #no-dtls
+    ```
+
+    In this case, replace the `turn:` schemes in the `turn_uris` settings below
+    with `turns:`.
+
+    We recommend that you only try to set up TLS/DTLS once you have set up a
+    basic installation and got it working.
+
+    NB: If your TLS certificate was provided by Let's Encrypt, TLS/DTLS will
+    not work with any Matrix client that uses Chromium's WebRTC library. This
+    currently includes Element Android & iOS; for more details, see their
+    [respective](https://github.com/vector-im/element-android/issues/1533)
+    [issues](https://github.com/vector-im/element-ios/issues/2712) as well as the underlying
+    [WebRTC issue](https://bugs.chromium.org/p/webrtc/issues/detail?id=11710).
+    Consider using a ZeroSSL certificate for your TURN server as a working alternative.
+
+1.  Ensure your firewall allows traffic into the TURN server on the ports
+    you've configured it to listen on (By default: 3478 and 5349 for TURN
+    traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
+    for the UDP relay.)
+
+1.  If your TURN server is behind NAT, the NAT gateway must have an external,
+    publicly-reachable IP address. You must configure `coturn` to advertise that
+    address to connecting clients:
+
+    ```
+    external-ip=EXTERNAL_NAT_IPv4_ADDRESS
+    ```
+
+    You may optionally limit the TURN server to listen only on the local
+    address that is mapped by NAT to the external address:
+
+    ```
+    listening-ip=INTERNAL_TURNSERVER_IPv4_ADDRESS
+    ```
+
+    If your NAT gateway is reachable over both IPv4 and IPv6, you may
+    configure `coturn` to advertise each available address:
+
+    ```
+    external-ip=EXTERNAL_NAT_IPv4_ADDRESS
+    external-ip=EXTERNAL_NAT_IPv6_ADDRESS
+    ```
+
+    When advertising an external IPv6 address, ensure that the firewall and
+    network settings of the system running your TURN server are configured to
+    accept IPv6 traffic, and that the TURN server is listening on the local
+    IPv6 address that is mapped by NAT to the external IPv6 address.
+
+1.  (Re)start the turn server:
+
+    * If you used the Debian package (or have set up a systemd unit yourself):
+      ```sh
+      sudo systemctl restart coturn
+      ```
+
+    * If you built from source:
+
+      ```sh
+      /usr/local/bin/turnserver -o
+      ```
diff --git a/docs/setup/turn/eturnal.md b/docs/setup/turn/eturnal.md
new file mode 100644
index 0000000000..2e5a45673e
--- /dev/null
+++ b/docs/setup/turn/eturnal.md
@@ -0,0 +1,170 @@
+# eturnal TURN server
+
+The following sections describe how to install [eturnal](<https://github.com/processone/eturnal>) 
+(which implements the TURN REST API).
+
+## `eturnal` setup
+
+### Initial installation
+
+The `eturnal` TURN server implementation is available from a variety of sources 
+such as native package managers, binary packages, installation from source or 
+[container image](https://eturnal.net/documentation/code/docker.html). They are 
+all described [here](https://github.com/processone/eturnal#installation).
+
+Quick-Test instructions in a [Linux Shell](https://github.com/processone/eturnal/blob/master/QUICK-TEST.md) 
+or with [Docker](https://github.com/processone/eturnal/blob/master/docker-k8s/QUICK-TEST.md) 
+are available as well.
+
+### Configuration
+
+After installation, `eturnal` usually ships a [default configuration file](https://github.com/processone/eturnal/blob/master/config/eturnal.yml) 
+here: `/etc/eturnal.yml` (and, if not found there, there is a backup file here: 
+`/opt/eturnal/etc/eturnal.yml`). It uses the (indentation-sensitive!) [YAML](https://en.wikipedia.org/wiki/YAML) 
+format. The file contains further explanations.
+
+Here are some hints how to configure eturnal on your [host machine](https://github.com/processone/eturnal#configuration) 
+or when using e.g. [Docker](https://eturnal.net/documentation/code/docker.html).
+You may also further deep dive into the [reference documentation](https://eturnal.net/documentation/).
+
+`eturnal` runs out of the box with the default configuration. To enable TURN and 
+to integrate it with your homeserver, some aspects in `eturnal`'s default configuration file 
+must be edited:
+
+1.  Homeserver's [`turn_shared_secret`](../../usage/configuration/config_documentation.md#turn_shared_secret) 
+    and eturnal's shared `secret` for authentication
+
+    Both need to have the same value. Uncomment and adjust this line in `eturnal`'s 
+    configuration file:
+
+    ```yaml
+    secret: "long-and-cryptic"     # Shared secret, CHANGE THIS.
+    ```
+
+    One way to generate a `secret` is with `pwgen`:
+
+    ```sh
+    pwgen -s 64 1
+    ```
+
+1.  Public IP address
+
+    If your TURN server is behind NAT, the NAT gateway must have an external,
+    publicly-reachable IP address. `eturnal` tries to autodetect the public IP address, 
+    however, it may also be configured by uncommenting and adjusting this line, so 
+    `eturnal` advertises that address to connecting clients:
+
+    ```yaml
+    relay_ipv4_addr: "203.0.113.4" # The server's public IPv4 address.
+    ```
+
+    If your NAT gateway is reachable over both IPv4 and IPv6, you may
+    configure `eturnal` to advertise each available address:
+
+    ```yaml
+    relay_ipv4_addr: "203.0.113.4" # The server's public IPv4 address.
+    relay_ipv6_addr: "2001:db8::4" # The server's public IPv6 address (optional).
+    ```
+
+    When advertising an external IPv6 address, ensure that the firewall and
+    network settings of the system running your TURN server are configured to
+    accept IPv6 traffic, and that the TURN server is listening on the local
+    IPv6 address that is mapped by NAT to the external IPv6 address.
+
+1.  Logging
+
+    If `eturnal` was started by systemd, log files are written into the
+    `/var/log/eturnal` directory by default. In order to log to the [journal](https://www.freedesktop.org/software/systemd/man/systemd-journald.service.html)
+    instead, the `log_dir` option can be set to `stdout` in the configuration file.
+
+1.  Security considerations
+
+    Consider your security settings. TURN lets users request a relay which will
+    connect to arbitrary IP addresses and ports. The following configuration is
+    suggested as a minimum starting point, [see also the official documentation](https://eturnal.net/documentation/#blacklist):
+
+    ```yaml
+    ## Reject TURN relaying from/to the following addresses/networks:
+    blacklist:                 # This is the default blacklist.
+        - "127.0.0.0/8"        # IPv4 loopback.
+        - "::1"                # IPv6 loopback.
+        - recommended          # Expands to a number of networks recommended to be
+                               # blocked, but includes private networks. Those
+                               # would have to be 'whitelist'ed if eturnal serves
+                               # local clients/peers within such networks.
+    ```
+
+    To whitelist IP addresses or specific (private) networks, you need to **add** a 
+    whitelist part into the configuration file, e.g.:
+
+    ```yaml
+    whitelist:
+        - "192.168.0.0/16"
+        - "203.0.113.113"
+        - "2001:db8::/64"
+    ```
+
+    The more specific, the better.
+
+1.  TURNS (TURN via TLS/DTLS)
+
+    Also consider supporting TLS/DTLS. To do this, adjust the following settings
+    in the `eturnal.yml` configuration file (TLS parts should not be commented anymore):
+
+    ```yaml
+    listen:
+        - ip: "::"
+          port: 3478
+          transport: udp
+        - ip: "::"
+          port: 3478
+          transport: tcp
+        - ip: "::"
+          port: 5349
+          transport: tls
+
+    ## TLS certificate/key files (must be readable by 'eturnal' user!):
+    tls_crt_file: /etc/eturnal/tls/crt.pem
+    tls_key_file: /etc/eturnal/tls/key.pem
+    ```
+
+    In this case, replace the `turn:` schemes in homeserver's `turn_uris` settings
+    with `turns:`. More is described [here](../../usage/configuration/config_documentation.md#turn_uris).
+
+    We recommend that you only try to set up TLS/DTLS once you have set up a
+    basic installation and got it working.
+
+    NB: If your TLS certificate was provided by Let's Encrypt, TLS/DTLS will
+    not work with any Matrix client that uses Chromium's WebRTC library. This
+    currently includes Element Android & iOS; for more details, see their
+    [respective](https://github.com/vector-im/element-android/issues/1533)
+    [issues](https://github.com/vector-im/element-ios/issues/2712) as well as the underlying
+    [WebRTC issue](https://bugs.chromium.org/p/webrtc/issues/detail?id=11710).
+    Consider using a ZeroSSL certificate for your TURN server as a working alternative.
+
+1.  Firewall
+
+    Ensure your firewall allows traffic into the TURN server on the ports
+    you've configured it to listen on (By default: 3478 and 5349 for TURN
+    traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
+    for the UDP relay.)
+
+1.  Reload/ restarting `eturnal`
+
+    Changes in the configuration file require `eturnal` to reload/ restart, this
+    can be achieved by:
+
+    ```sh
+    eturnalctl reload
+    ```
+    
+    `eturnal` performs a configuration check before actually reloading/ restarting
+    and provides hints, if something is not correctly configured.
+
+### eturnalctl opterations script
+
+`eturnal` offers a handy [operations script](https://eturnal.net/documentation/#Operation) 
+which can be called e.g. to check, whether the service is up, to restart the service, 
+to query how many active sessions exist, to change logging behaviour and so on.
+
+Hint: If `eturnalctl` is not part of your `$PATH`, consider either sym-linking it (e.g. ´ln -s /opt/eturnal/bin/eturnalctl /usr/local/bin/eturnalctl´) or call it from the default `eturnal` directory directly: e.g. `/opt/eturnal/bin/eturnalctl info`
diff --git a/docs/turn-howto.md b/docs/turn-howto.md
index 37a311ad9c..b466cab40c 100644
--- a/docs/turn-howto.md
+++ b/docs/turn-howto.md
@@ -9,222 +9,28 @@ allows the homeserver to generate credentials that are valid for use on the
 TURN server through the use of a secret shared between the homeserver and the
 TURN server.
 
-The following sections describe how to install [coturn](<https://github.com/coturn/coturn>) (which implements the TURN REST API) and integrate it with synapse.
+This documentation provides two TURN server configuration examples:
+
+* [coturn](setup/turn/coturn.md)
+* [eturnal](setup/turn/eturnal.md)
 
 ## Requirements
 
-For TURN relaying with `coturn` to work, it must be hosted on a server/endpoint with a public IP.
+For TURN relaying to work, the TURN service must be hosted on a server/endpoint with a public IP.
 
 Hosting TURN behind NAT requires port forwaring and for the NAT gateway to have a public IP.
 However, even with appropriate configuration, NAT is known to cause issues and to often not work.
 
-## `coturn` setup
-
-### Initial installation
-
-The TURN daemon `coturn` is available from a variety of sources such as native package managers, or installation from source.
-
-#### Debian installation
-
-Just install the debian package:
-
-```sh
-apt install coturn
-```
-
-This will install and start a systemd service called `coturn`.
-
-#### Source installation
-
-1. Download the [latest release](https://github.com/coturn/coturn/releases/latest) from github.  Unpack it and `cd` into the directory.
-
-1.  Configure it:
-
-    ```sh
-    ./configure
-    ```
-
-    You may need to install `libevent2`: if so, you should do so in
-    the way recommended by your operating system. You can ignore
-    warnings about lack of database support: a database is unnecessary
-    for this purpose.
-
-1.  Build and install it:
-
-    ```sh
-    make
-    make install
-    ```
-
-### Configuration
-
-1.  Create or edit the config file in `/etc/turnserver.conf`. The relevant
-    lines, with example values, are:
-
-    ```
-    use-auth-secret
-    static-auth-secret=[your secret key here]
-    realm=turn.myserver.org
-    ```
-
-    See `turnserver.conf` for explanations of the options. One way to generate
-    the `static-auth-secret` is with `pwgen`:
-
-    ```sh
-    pwgen -s 64 1
-    ```
-
-    A `realm` must be specified, but its value is somewhat arbitrary. (It is
-    sent to clients as part of the authentication flow.) It is conventional to
-    set it to be your server name.
-
-1.  You will most likely want to configure coturn to write logs somewhere. The
-    easiest way is normally to send them to the syslog:
-
-    ```sh
-    syslog
-    ```
-
-    (in which case, the logs will be available via `journalctl -u coturn` on a
-    systemd system). Alternatively, coturn can be configured to write to a
-    logfile - check the example config file supplied with coturn.
-
-1.  Consider your security settings. TURN lets users request a relay which will
-    connect to arbitrary IP addresses and ports. The following configuration is
-    suggested as a minimum starting point:
-
-    ```
-    # VoIP traffic is all UDP. There is no reason to let users connect to arbitrary TCP endpoints via the relay.
-    no-tcp-relay
-
-    # don't let the relay ever try to connect to private IP address ranges within your network (if any)
-    # given the turn server is likely behind your firewall, remember to include any privileged public IPs too.
-    denied-peer-ip=10.0.0.0-10.255.255.255
-    denied-peer-ip=192.168.0.0-192.168.255.255
-    denied-peer-ip=172.16.0.0-172.31.255.255
-
-    # recommended additional local peers to block, to mitigate external access to internal services.
-    # https://www.rtcsec.com/article/slack-webrtc-turn-compromise-and-bug-bounty/#how-to-fix-an-open-turn-relay-to-address-this-vulnerability
-    no-multicast-peers
-    denied-peer-ip=0.0.0.0-0.255.255.255
-    denied-peer-ip=100.64.0.0-100.127.255.255
-    denied-peer-ip=127.0.0.0-127.255.255.255
-    denied-peer-ip=169.254.0.0-169.254.255.255
-    denied-peer-ip=192.0.0.0-192.0.0.255
-    denied-peer-ip=192.0.2.0-192.0.2.255
-    denied-peer-ip=192.88.99.0-192.88.99.255
-    denied-peer-ip=198.18.0.0-198.19.255.255
-    denied-peer-ip=198.51.100.0-198.51.100.255
-    denied-peer-ip=203.0.113.0-203.0.113.255
-    denied-peer-ip=240.0.0.0-255.255.255.255
-
-    # special case the turn server itself so that client->TURN->TURN->client flows work
-    # this should be one of the turn server's listening IPs
-    allowed-peer-ip=10.0.0.1
-
-    # consider whether you want to limit the quota of relayed streams per user (or total) to avoid risk of DoS.
-    user-quota=12 # 4 streams per video call, so 12 streams = 3 simultaneous relayed calls per user.
-    total-quota=1200
-    ```
-
-1.  Also consider supporting TLS/DTLS. To do this, add the following settings
-    to `turnserver.conf`:
-
-    ```
-    # TLS certificates, including intermediate certs.
-    # For Let's Encrypt certificates, use `fullchain.pem` here.
-    cert=/path/to/fullchain.pem
-
-    # TLS private key file
-    pkey=/path/to/privkey.pem
-
-    # Ensure the configuration lines that disable TLS/DTLS are commented-out or removed
-    #no-tls
-    #no-dtls
-    ```
-
-    In this case, replace the `turn:` schemes in the `turn_uris` settings below
-    with `turns:`.
-
-    We recommend that you only try to set up TLS/DTLS once you have set up a
-    basic installation and got it working.
-
-    NB: If your TLS certificate was provided by Let's Encrypt, TLS/DTLS will
-    not work with any Matrix client that uses Chromium's WebRTC library. This
-    currently includes Element Android & iOS; for more details, see their
-    [respective](https://github.com/vector-im/element-android/issues/1533)
-    [issues](https://github.com/vector-im/element-ios/issues/2712) as well as the underlying
-    [WebRTC issue](https://bugs.chromium.org/p/webrtc/issues/detail?id=11710).
-    Consider using a ZeroSSL certificate for your TURN server as a working alternative.
-
-1.  Ensure your firewall allows traffic into the TURN server on the ports
-    you've configured it to listen on (By default: 3478 and 5349 for TURN
-    traffic (remember to allow both TCP and UDP traffic), and ports 49152-65535
-    for the UDP relay.)
-
-1.  If your TURN server is behind NAT, the NAT gateway must have an external,
-    publicly-reachable IP address. You must configure coturn to advertise that
-    address to connecting clients:
-
-    ```
-    external-ip=EXTERNAL_NAT_IPv4_ADDRESS
-    ```
-
-    You may optionally limit the TURN server to listen only on the local
-    address that is mapped by NAT to the external address:
-
-    ```
-    listening-ip=INTERNAL_TURNSERVER_IPv4_ADDRESS
-    ```
-
-    If your NAT gateway is reachable over both IPv4 and IPv6, you may
-    configure coturn to advertise each available address:
-
-    ```
-    external-ip=EXTERNAL_NAT_IPv4_ADDRESS
-    external-ip=EXTERNAL_NAT_IPv6_ADDRESS
-    ```
-
-    When advertising an external IPv6 address, ensure that the firewall and
-    network settings of the system running your TURN server are configured to
-    accept IPv6 traffic, and that the TURN server is listening on the local
-    IPv6 address that is mapped by NAT to the external IPv6 address.
-
-1.  (Re)start the turn server:
-
-    * If you used the Debian package (or have set up a systemd unit yourself):
-      ```sh
-      systemctl restart coturn
-      ```
-
-    * If you installed from source:
-
-      ```sh
-      bin/turnserver -o
-      ```
+Afterwards, the homeserver needs some further configuration.
 
 ## Synapse setup
 
 Your homeserver configuration file needs the following extra keys:
 
-1.  "`turn_uris`": This needs to be a yaml list of public-facing URIs
-    for your TURN server to be given out to your clients. Add separate
-    entries for each transport your TURN server supports.
-2.  "`turn_shared_secret`": This is the secret shared between your
-    homeserver and your TURN server, so you should set it to the same
-    string you used in turnserver.conf.
-3.  "`turn_user_lifetime`": This is the amount of time credentials
-    generated by your homeserver are valid for (in milliseconds).
-    Shorter times offer less potential for abuse at the expense of
-    increased traffic between web clients and your homeserver to
-    refresh credentials. The TURN REST API specification recommends
-    one day (86400000).
-4.  "`turn_allow_guests`": Whether to allow guest users to use the
-    TURN server. This is enabled by default, as otherwise VoIP will
-    not work reliably for guests. However, it does introduce a
-    security risk as it lets guests connect to arbitrary endpoints
-    without having gone through a CAPTCHA or similar to register a
-    real account.
+1.  [`turn_uris`](usage/configuration/config_documentation.md#turn_uris)
+2.  [`turn_shared_secret`](usage/configuration/config_documentation.md#turn_shared_secret)
+3.  [`turn_user_lifetime`](usage/configuration/config_documentation.md#turn_user_lifetime)
+4.  [`turn_allow_guests`](usage/configuration/config_documentation.md#turn_allow_guests)
 
 As an example, here is the relevant section of the config file for `matrix.org`. The
 `turn_uris` are appropriate for TURN servers listening on the default ports, with no TLS.
@@ -263,7 +69,7 @@ Here are a few things to try:
  * Check that you have opened your firewall to allow UDP traffic to the UDP
    relay ports (49152-65535 by default).
 
- * Try disabling `coturn`'s TLS/DTLS listeners and enable only its (unencrypted)
+ * Try disabling TLS/DTLS listeners and enable only its (unencrypted)
    TCP/UDP listeners. (This will only leave signaling traffic unencrypted;
    voice & video WebRTC traffic is always encrypted.)
 
@@ -288,12 +94,19 @@ Here are a few things to try:
 
     * ensure that your TURN server uses the NAT gateway as its default route.
 
- * Enable more verbose logging in coturn via the `verbose` setting:
+ * Enable more verbose logging, in `coturn` via the `verbose` setting:
 
    ```
    verbose
    ```
 
+    or with `eturnal` with the shell command `eturnalctl loglevel debug` or in the configuration file (the service needs to [reload](https://eturnal.net/documentation/#Operation) for it to become effective):
+
+    ```yaml
+        ## Logging configuration:
+            log_level: debug
+    ```
+
    ... and then see if there are any clues in its logs.
 
  * If you are using a browser-based client under Chrome, check
@@ -317,7 +130,7 @@ Here are a few things to try:
       matrix client to your homeserver in your browser's network inspector. In
       the response you should see `username` and `password`. Or:
 
-    * Use the following shell commands:
+    * Use the following shell commands for `coturn`:
 
       ```sh
       secret=staticAuthSecretHere
@@ -327,11 +140,16 @@ Here are a few things to try:
       echo -e "username: $u\npassword: $p"
       ```
 
-      Or:
+      or for `eturnal`
+
+      ```sh
+      eturnalctl credentials
+      ```
+      
 
-    * Temporarily configure coturn to accept a static username/password. To do
-      this, comment out `use-auth-secret` and `static-auth-secret` and add the
-      following:
+    * Or (**coturn only**): Temporarily configure `coturn` to accept a static
+      username/password. To do this, comment out `use-auth-secret` and
+      `static-auth-secret` and add the following:
 
       ```
       lt-cred-mech