Rate-limit outgoing read-receipts as per #4730.

Make it so that most options in the config are optional, and commented out in
the generated config.

The reasons this is a good thing are as follows:

* If we decide that we should change the default for an option, we can do so,
  and only those admins that have deliberately chosen to override that option
  will be stuck on the old setting.

* It moves us towards a point where we can get rid of the super-surprising
  feature of synapse where the default settings for the config come from the
  generated yaml.

* It makes setting up a test config for unit testing an order of magnitude
  easier (see forthcoming PR).

* It makes the generated config more consistent, and hopefully easier for users
  to understand.

Add two ratelimiters on login (per-IP address and per-userID).

Improved federation configuration docs.  Specifically detailing  .well-known and SRV based delegation methods. 

Inspiration Valentin Lab <valentin.lab@kalysto.org> for https://github.com/matrix-org/synapse/pull/4781

* Clarify what registration_shared_secret allows for (#2885)

Signed-off-by: Aaron Raimist <aaron@raim.ist>

* Add changelog

Signed-off-by: Aaron Raimist <aaron@raim.ist>

* Rate-limiting for registration

* Add unit test for registration rate limiting

* Add config parameters for rate limiting on auth endpoints

* Doc

* Fix doc of rate limiting function

Co-Authored-By: babolivier <contact@brendanabolivier.com>

* Incorporate review

* Fix config parsing

* Fix linting errors

* Set default config for auth rate limiting

* Fix tests

* Add changelog

* Advance reactor instead of mocked clock

* Move parameters to registration specific config and give them more sensible default values

* Remove unused config options

* Don't mock the rate limiter un MAU tests

* Rename _register_with_store into register_with_store

* Make CI happy

* Remove unused import

* Update sample config

* Fix ratelimiting test for py2

* Add non-guest test

The v4v6 option only has a usage one ipv6 socket: https://serverfault.com/q/747895



Signed-off-by: Flakebi <flakebi@t-online.de>

Signed-off-by: Joseph Weston <joseph@weston.cloud>

So that it actually works. See https://httpd.apache.org/docs/2.4/mod/mod_proxy.html#proxypass



Signed-off-by: Paul Tötterman <paul.totterman@iki.fi>

If the client failed to process incoming commands during the initial set
up of the replication connection it would immediately disconnect and
reconnect, resulting in a tightloop.

This can happen, for example, when subscribing to a stream that has a
row that is too long in the backlog.

The fix here is to not consider the connection successfully set up until
the client has succesfully subscribed and caught up with the streams.
This ensures that the retry logic timers aren't reset until then,
meaning that if an error does happen during start up the client will
continue backing off before retrying again.

* Added HAProxy example

Proposal of an example with HAProxy. Asked by #4541.

Signed-off-by: Benoît S. (“Benpro”) <gitlab@benpro.fr>

* Following suggestions of @richvdh

Factor out the reverse proxy info to a separate file, add some more info on
reverse-proxying the federation port.

Fix incorrect heading level

A surprising number of people are using the well-known method, and are
simply copying the example configuration. This is problematic as the
example includes an explicit port, which causes inbound federation
requests to have the HTTP Host header include the port, upsetting some
reverse proxies.

Given that, we update the well-known example to be more explicit about
the various ways you can set it up, and the consequence of using an
explict port.

A surprising number of people are using the well-known method, and are
simply copying the example configuration. This is problematic as the
example includes an explicit port, which causes inbound federation
requests to have the HTTP Host header include the port, upsetting some
reverse proxies.

Given that, we update the well-known example to be more explicit about
the various ways you can set it up, and the consequence of using an
explict port.

MSC1711 certificates FAQ