rsync via tunnel - 3 boxes separated by internet

[Jay Strauss]

Wayne Davison wrote:
> On Sun, May 15, 2005 at 02:33:15PM -0500, Jay Strauss wrote:
> 
>>BoxA --internet-- BoxB (accessable only by ssh) -- BoxC
> 
> 
> What about this?
> 
>     rsync -av --rsync-path="ssh BoxC rsync" BoxB:/source/ /dest/
> 
> This command looks like it is copying a file from BoxB, but the remote
> command run on BoxB to start rsync really contacts BoxC and runs the
> remote rsync there, so "/source/" is coming from BoxC.
> 
> ..wayne..

Also, how do I make it use a tunnel to BoxB?  I can only reach BoxB via 
ssh and port 22.  I need to make the first rsync "rsync -av" use ssh to 
get to BoxB.

Maybe I don't understand something. but it looks like the ssh in the 
above command only applies once I've connected to BoxB

Thanks
Jay