Merge pull request #6940 from matrix-org/babolivier/federate.md

Clean up and update federation docs

changelog.d/6940.doc

+Clean up and update docs on setting up federation.

docs/delegate.md

+# Delegation
+
+By default, other homeservers will expect to be able to reach yours via
+your `server_name`, on port 8448. For example, if you set your `server_name`
+to `example.com` (so that your user names look like `@user:example.com`),
+other servers will try to connect to yours at `https://example.com:8448/`.
+
+Delegation is a Matrix feature allowing a homeserver admin to retain a
+`server_name` of `example.com` so that user IDs, room aliases, etc continue
+to look like `*:example.com`, whilst having federation traffic routed
+to a different server and/or port (e.g. `synapse.example.com:443`).
+
+## .well-known delegation
+
+To use this method, you need to be able to alter the
+`server_name` 's https server to serve the `/.well-known/matrix/server`
+URL. Having an active server (with a valid TLS certificate) serving your
+`server_name` domain is out of the scope of this documentation.
+
+The URL `https://<server_name>/.well-known/matrix/server` should
+return a JSON structure containing the key `m.server` like so:
+
+```json
+{
+    "m.server": "<synapse.server.name>[:<yourport>]"
+}
+```
+
+In our example, this would mean that URL `https://example.com/.well-known/matrix/server`
+should return:
+
+```json
+{
+    "m.server": "synapse.example.com:443"
+}
+```
+
+Note, specifying a port is optional. If no port is specified, then it defaults
+to 8448.
+
+With .well-known delegation, federating servers will check for a valid TLS
+certificate for the delegated hostname (in our example: `synapse.example.com`).
+
+## SRV DNS record delegation
+
+It is also possible to do delegation using a SRV DNS record. However, that is
+considered an advanced topic since it's a bit complex to set up, and `.well-known`
+delegation is already enough in most cases.
+
+However, if you really need it, you can find some documentation on how such a
+record should look like and how Synapse will use it in [the Matrix
+specification](https://matrix.org/docs/spec/server_server/latest#resolving-server-names).
+
+## Delegation FAQ
+
+### When do I need delegation?
+
+If your homeserver's APIs are accessible on the default federation port (8448)
+and the domain your `server_name` points to, you do not need any delegation.
+
+For instance, if you registered `example.com` and pointed its DNS A record at a
+fresh server, you could install Synapse on that host, giving it a `server_name`
+of `example.com`, and once a reverse proxy has been set up to proxy all requests
+sent to the port `8448` and serve TLS certificates for `example.com`, you
+wouldn't need any delegation set up.
+
+**However**, if your homeserver's APIs aren't accessible on port 8448 and on the
+domain `server_name` points to, you will need to let other servers know how to
+find it using delegation.
+
+### Do you still recommend against using a reverse proxy on the federation port?
+
+We no longer actively recommend against using a reverse proxy. Many admins will
+find it easier to direct federation traffic to a reverse proxy and manage their
+own TLS certificates, and this is a supported configuration.
+
+See [reverse_proxy.md](reverse_proxy.md) for information on setting up a
+reverse proxy.
+
+### Do I still need to give my TLS certificates to Synapse if I am using a reverse proxy?
+
+This is no longer necessary. If you are using a reverse proxy for all of your
+TLS traffic, then you can set `no_tls: True` in the Synapse config.
+
+In that case, the only reason Synapse needs the certificate is to populate a legacy
+`tls_fingerprints` field in the federation API. This is ignored by Synapse 0.99.0
+and later, and the only time pre-0.99 Synapses will check it is when attempting to
+fetch the server keys - and generally this is delegated via `matrix.org`, which
+is running a modern version of Synapse.
+
+### Do I need the same certificate for the client and federation port?
+
+No. There is nothing stopping you from using different certificates,
+particularly if you are using a reverse proxy.
\ No newline at end of file

docs/federate.md

-Setting up Federation
+Setting up federation
 =====================
 
 Federation is the process by which users on different servers can participate
 in the same room. For this to work, those other servers must be able to contact
 yours to send messages.
 
-The ``server_name`` configured in the Synapse configuration file (often
-``homeserver.yaml``) defines how resources (users, rooms, etc.) will be
-identified (eg: ``@user:example.com``, ``#room:example.com``). By
-default, it is also the domain that other servers will use to
-try to reach your server (via port 8448). This is easy to set
-up and will work provided you set the ``server_name`` to match your
-machine's public DNS hostname, and provide Synapse with a TLS certificate
-which is valid for your ``server_name``.
+The `server_name` configured in the Synapse configuration file (often
+`homeserver.yaml`) defines how resources (users, rooms, etc.) will be
+identified (eg: `@user:example.com`, `#room:example.com`). By default,
+it is also the domain that other servers will use to try to reach your
+server (via port 8448). This is easy to set up and will work provided
+you set the `server_name` to match your machine's public DNS hostname.
+
+For this default configuration to work, you will need to listen for TLS
+connections on port 8448. The preferred way to do that is by using a
+reverse proxy: see [reverse_proxy.md](<reverse_proxy.md>) for instructions
+on how to correctly set one up.
+
+In some cases you might not want to run Synapse on the machine that has
+the `server_name` as its public DNS hostname, or you might want federation
+traffic to use a different port than 8448. For example, you might want to
+have your user names look like `@user:example.com`, but you want to run
+Synapse on `synapse.example.com` on port 443. This can be done using
+delegation, which allows an admin to control where federation traffic should
+be sent. See [delegate.md](delegate.md) for instructions on how to set this up.
 
 Once federation has been configured, you should be able to join a room over
-federation. A good place to start is ``#synapse:matrix.org`` - a room for
+federation. A good place to start is `#synapse:matrix.org` - a room for
 Synapse admins.
 
-
-## Delegation
-
-For a more flexible configuration, you can have ``server_name``
-resources (eg: ``@user:example.com``) served by a different host and
-port (eg: ``synapse.example.com:443``). There are two ways to do this:
-
-- adding a ``/.well-known/matrix/server`` URL served on ``https://example.com``.
-- adding a DNS ``SRV`` record in the DNS zone of domain
-  ``example.com``.
-
-Without configuring delegation, the matrix federation will
-expect to find your server via ``example.com:8448``. The following methods
-allow you retain a `server_name` of `example.com` so that your user IDs, room
-aliases, etc continue to look like `*:example.com`, whilst having your
-federation traffic routed to a different server.
-
-### .well-known delegation
-
-To use this method, you need to be able to alter the
-``server_name`` 's https server to serve the ``/.well-known/matrix/server``
-URL. Having an active server (with a valid TLS certificate) serving your
-``server_name`` domain is out of the scope of this documentation.
-
-The URL ``https://<server_name>/.well-known/matrix/server`` should
-return a JSON structure containing the key ``m.server`` like so:
-
-    {
-	    "m.server": "<synapse.server.name>[:<yourport>]"
-    }
-
-In our example, this would mean that URL ``https://example.com/.well-known/matrix/server``
-should return:
-
-    {
-	    "m.server": "synapse.example.com:443"
-    }
-
-Note, specifying a port is optional. If a port is not specified an SRV lookup
-is performed, as described below. If the target of the
-delegation does not have an SRV record, then the port defaults to 8448.
-
-Most installations will not need to configure .well-known. However, it can be
-useful in cases where the admin is hosting on behalf of someone else and
-therefore cannot gain access to the necessary certificate. With .well-known,
-federation servers will check for a valid TLS certificate for the delegated
-hostname (in our example: ``synapse.example.com``).
-
-### DNS SRV delegation
-
-To use this delegation method, you need to have write access to your
-``server_name`` 's domain zone DNS records (in our example it would be
-``example.com`` DNS zone).
-
-This method requires the target server to provide a
-valid TLS certificate for the original ``server_name``.
-
-You need to add a SRV record in your ``server_name`` 's DNS zone with
-this format:
-
-     _matrix._tcp.<yourdomain.com> <ttl> IN SRV <priority> <weight> <port> <synapse.server.name>
-
-In our example, we would need to add this SRV record in the
-``example.com`` DNS zone:
-
-     _matrix._tcp.example.com. 3600 IN SRV 10 5 443 synapse.example.com.
-
-Once done and set up, you can check the DNS record with ``dig -t srv
-_matrix._tcp.<server_name>``. In our example, we would expect this:
-
-    $ dig -t srv _matrix._tcp.example.com
-    _matrix._tcp.example.com. 3600    IN      SRV     10 0 443 synapse.example.com.
-
-Note that the target of a SRV record cannot be an alias (CNAME record): it has to point
-directly to the server hosting the synapse instance.
-
-### Delegation FAQ
-#### When do I need a SRV record or .well-known URI?
-
-If your homeserver listens on the default federation port (8448), and your
-`server_name` points to the host that your homeserver runs on, you do not need an SRV
-record or `.well-known/matrix/server` URI.
-
-For instance, if you registered `example.com` and pointed its DNS A record at a
-fresh server, you could install Synapse on that host,
-giving it a `server_name` of `example.com`, and once [ACME](acme.md) support is enabled,
-it would automatically generate a valid TLS certificate for you via Let's Encrypt
-and no SRV record or .well-known URI would be needed.
-
-**However**, if your server does not listen on port 8448, or if your `server_name`
-does not point to the host that your homeserver runs on, you will need to let
-other servers know how to find it. The way to do this is via .well-known or an
-SRV record.
-
-#### I have created a .well-known URI. Do I also need an SRV record?
-
-No. You can use either `.well-known` delegation or use an SRV record for delegation. You
-do not need to use both to delegate to the same location.
-
-#### Can I manage my own certificates rather than having Synapse renew certificates itself?
-
-Yes, you are welcome to manage your certificates yourself. Synapse will only
-attempt to obtain certificates from Let's Encrypt if you configure it to do
-so.The only requirement is that there is a valid TLS cert present for
-federation end points.
-
-#### Do you still recommend against using a reverse proxy on the federation port?
-
-We no longer actively recommend against using a reverse proxy. Many admins will
-find it easier to direct federation traffic to a reverse proxy and manage their
-own TLS certificates, and this is a supported configuration.
-
-See [reverse_proxy.md](reverse_proxy.md) for information on setting up a
-reverse proxy.
-
-#### Do I still need to give my TLS certificates to Synapse if I am using a reverse proxy?
-
-Practically speaking, this is no longer necessary.
-
-If you are using a reverse proxy for all of your TLS traffic, then you can set
-`no_tls: True` in the Synapse config. In that case, the only reason Synapse
-needs the certificate is to populate a legacy `tls_fingerprints` field in the
-federation API. This is ignored by Synapse 0.99.0 and later, and the only time
-pre-0.99 Synapses will check it is when attempting to fetch the server keys -
-and generally this is delegated via `matrix.org`, which will be running a modern
-version of Synapse.
-
-#### Do I need the same certificate for the client and federation port?
-
-No. There is nothing stopping you from using different certificates,
-particularly if you are using a reverse proxy. However, Synapse will use the
-same certificate on any ports where TLS is configured.
-
 ## Troubleshooting
 
-You can use the [federation tester](
-<https://matrix.org/federationtester>) to check if your homeserver is
-configured correctly. Alternatively try the [JSON API used by the federation tester](https://matrix.org/federationtester/api/report?server_name=DOMAIN).
-Note that you'll have to modify this URL to replace ``DOMAIN`` with your
-``server_name``. Hitting the API directly provides extra detail.
+You can use the [federation tester](https://matrix.org/federationtester)
+to check if your homeserver is configured correctly. Alternatively try the
+[JSON API used by the federation tester](https://matrix.org/federationtester/api/report?server_name=DOMAIN).
+Note that you'll have to modify this URL to replace `DOMAIN` with your
+`server_name`. Hitting the API directly provides extra detail.
 
 The typical failure mode for federation is that when the server tries to join
 a room, it is rejected with "401: Unauthorized". Generally this means that other
@@ -169,8 +47,8 @@ you invite them to. This can be caused by an incorrectly-configured reverse
 proxy: see [reverse_proxy.md](<reverse_proxy.md>) for instructions on how to correctly
 configure a reverse proxy.
 
-## Running a Demo Federation of Synapses
+## Running a demo federation of Synapses
 
 If you want to get up and running quickly with a trio of homeservers in a
-private federation, there is a script in the ``demo`` directory. This is mainly
+private federation, there is a script in the `demo` directory. This is mainly
 useful just for development purposes. See [demo/README](<../demo/README>).

docs/reverse_proxy.md

@@ -18,9 +18,10 @@ When setting up a reverse proxy, remember that Matrix clients and other
 Matrix servers do not necessarily need to connect to your server via the
 same server name or port. Indeed, clients will use port 443 by default,
 whereas servers default to port 8448. Where these are different, we
-refer to the 'client port' and the \'federation port\'. See [Setting
-up federation](federate.md) for more details of the algorithm used for
-federation connections.
+refer to the 'client port' and the \'federation port\'. See [the Matrix
+specification](https://matrix.org/docs/spec/server_server/latest#resolving-server-names)
+for more details of the algorithm used for federation connections, and
+[delegate.md](<delegate.md>) for instructions on setting up delegation.
 
 Let's assume that we expect clients to connect to our server at
 `https://matrix.example.com`, and other servers to connect at