Any chance you could take a peek at the patch I submitted for bug 19954
(HTTP tunneling through reverse proxy does not always work) as long as you
are looking at that source file?
BTW when I submitted the patch I bone-headedly swapped the params to diff so
the changes show as '-' instead of '+'
This is the same issue I was dealing with in mod_proxy
that I submitted the patch for in 'BUG 19954 [PATCH] HTTP
tunneling through reverse proxy does not always work'. In my case
I didn't care what the read size was, but I needed to forward
on whatever had been read, even if it was less than
800