it would be great is rsyncin server mode would support the proxy protocol of haproxy, so that originating IP address of clients can be preserved for rsync daemon even if it is behind a tcp proxy server like haproxy. For details and also examples of other services implmenting the proxy protocol, see https://www.haproxy.com/blog/haproxy/proxy-protocol/
The latest git version now has the "haproxy header" parameter (a BOOL) that will make the proxy header required when it is enabled (default: "no").