ejabberd receivers were meant to serve connections from frontends
to backends. However, this approach was not popular and frontend
related code was removed in previous releases. Now, ejabberd receiver's
code was also removed, making the code shorter and cleaner. Also, in
stress tests ejabberd now handles load more robustly, without
c2s processes overload (even with disabled shapers).
ejabberd_socket.erl is renamed to xmpp_socket.erl: it's supposed to
be finally moved into stand-alone xmpp library.
XEP-0368 describes this procedure as following:
> Both 'xmpp-' and 'xmpps-' records SHOULD be treated as
> the same record with regard to connection order as specified
> by RFC 2782 [3], in that all priorities and weights are mixed.
> This enables the server operator to decide if they would
> rather clients connect with STARTTLS or direct TLS.
Currently this is only supported for outgoing s2s connections.
For such connections ejabberd is now able to resolve SRV records
of type "_xmpps-server._tcp". Also, SNI and ALPN fields are set
during TLS handshake. No additional configuration is required.