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>

1 files changed, 29 insertions, 211 deletions

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