backupsrv$ ssh -A -M -f -N -T -R 0:127.0.0.1:22 -O forward dmzmachine
Allocated port 20545 for remote forward to 127.0.0.1:22
backupsrv$ ssh dmzmachine "tar -cvzf - /path | ssh -p 20545 127.0.0.1 'tar -xzpf - -C /dest'"
backupsrv$ ssh -O exit dmzmachine

backupsrv$ mkfifo fromssh tossh
backupsrv$ ssh <fromssh >tossh -T -y dmzserver "ssh -y -N -T -MS/tmp/ctl
-oProxyCommand=- backupsrv" &
backupsrv$ /usr/sbin/sshd -i -f < $fromssh > $tossh
backupsrv$ ssh dmzserver "tar -cvzf - /path | ssh -S /tmp/ctl backupsrv 'tar -xzpf - -C /dest'"