[Rd] Running ./tools/rsync-recommended through a proxy

[Douglas Bates]

My computers at my office will no longer be able to connect directly
to web sites etc.  I will be going through a proxy server.  The
particular server is running squid on port 3128.

I have managed to configure web browsers, ssh, apt, svn and a whole
lot of other tools to use the proxy server but I haven't been able to
configure rsync.  My usual method of updating my copy of the R-devel
sources is via

cd my_R_devel_sources
svn up
./tools/rsync-recommended

cd my_R_build_directory
...

Can anyone offer suggestions on how to get rsync-recommended to work
through a proxy?  I have set

export RSYNC_PROXY="machine.name:3128"

which I understand from the documentation is the magic environment
variable (I don't give the name of the server explicitly because it is
an open proxy).  However, I still get

bates at bates4:/usr/src/r-devel$ ./tools/rsync-recommended
bad response from proxy - HTTP/1.0 403 Forbidden
rsync: failed to connect to machine.name: Success (0)
rsync error: error in socket IO (code 10) at clientserver.c(94)
*** rsync failed to update Recommended files ***
Creating links

Is it likely that the proxy server is not passing connections to port 873?