dual multi-master/not-multi-master setup

[Roland Bauerschmidt <rb@debian.org>]

For a setup with about 300 slave servers, connected through an
unreliable network connection, I am thinking of implementing the
following setup:

master server:
 - not running in multi-master mode
 - replicating to slaves

slave servers:
 - running in multi-master mode
 - replicating to master
 - only entries from one sub-dc= are modified

this would have the following consequences:
 - update from master: replicated to slaves, not replicated back since
   slaves are in multi-master mode
 - update from slave: replicated to master, replicated back to all
   slaves, not replicated back since they are in multi-master mode

The problem I am having is that the master server (which is not running
in multi-master mode) doesn't accept any update requests except from the
updatedn. I assume, it "thinks" to be a slave and hence doesn't accept
any modifications, except from the master ("no such object"). In there
anything I can do about it? Or any other suggestions how to set this up?
True multi-master mode is no option as the slave servers are not able to
communicate with each other directly. True master/slave mode neither for
the same reason.

-- 
Roland Bauerschmidt