Ipsec tunnel between 2 sites with same network addressing

[openbsd]

Hi,

It is very simple to do a tunnel ipsec with 2 sites when they have
different network addressing.
But if site A use this : 192.168.0.0/24 and Site B use the same address,
how can we do ipsec tunnel ?
I suppose, we need to use binat rules in pf.conf... I don't understand how
to build that. If someone can explain me ...
Thank's