About gateway from WLAN to LAN

Bonjour,

When a 802.11 frame is sent on a LAN from an AP to an other AP of the same
ESS, the flags From_DS and To_DS are set.

So, the 802.11 frame has 4 valid addresses : 2 addresses of the end-to-end
stations, plus 2 addresses of the intermediate AP.

But, the 802.11 frame is carried through a 802.3 frame for example, to join
the AP of one BSS to the AP of the second BSS. The 802.3 include the both AP
addresses certainly.

How the end-to-end stations adresses are conveyed on 802.3? So, how the
encapsulation is done, is it supported by 802.1G layer, I'm not sure.

Somebody has an idea of that mechanism?
Thanks,
Angelot