I have implemented two carrier api (shipping).
Whenever seller uses my website’s shipment.
I have cron job which runs and updates the shipping status (since seller creates the shipment from either of the 2 carrier).
In case of drop shipping the seller has his own logistics (not using my website’s shipment).
What to do in this case since I don’t have any shipment data from seller.
Generally people just guess. I have never seen a system where people import shipping costs from their drop shippers.
if an indian seller is dropshipping some item from china, when he receives an order for the same item. He directly tells the dropshipping service to courier it to customer’s address .