CentOS - Jan 2017 - selinux & rsyncd: Allowing global read for backup

I want to set up rsyncd to expose the whole drive read-only to BackupPC 
running on another machine. So I need to set selinux to allow this. 
According to the Fedora wiki I can do so like this:

setsebool -P rsync_disable_trans 1

<https://fedoraproject.org/wiki/SELinux/rsync>

But when I run the command on CentOS 7.3 it tells me that this bool is not 
defined. So what do I do now?

(Everything works fine if I set SELinux to permissive.)

More digging and "getsebool -a | grep rsync" revealed the 
rsync_export_all_ro bool. I set that and now it looks like I can rsync from 
my BackupPC system.

setsebool -P rsync_export_all_ro 1

<https://linux.die.net/man/8/rsync_selinux>