Wouldn't it be faster todo a check for /manual in mirror-info.php?
just an idea here...
Initially I thought that we have no requirement for mirror sites to have url fopen wrapper turned on, or sockets working. But after your suggestion I realized that we already have code to post user notes with fsockopen() and friends. Now the only problem would be that the mirror-info page may time out waiting for the mirrors own response, and the master server would never get any answer.
The best would be if we would be able to check on the mirror that /manual is a virtual dir or a real one. I am not sure if virtual() can help us in this case. Maybe only if it's output would be bufferable, but it's not. Maybe we can put some small text file into /manual/en/ and include that with virtual, letting it be part of the output of mirror-info and then check for that in the mirror-test script. This seems to be better to me, as virtual() executes quickly on the same machine.
Goba