[B.A.T.M.A.N.] how to make IP layer handle the change of network topology

Hello, eveyone, I am learning the batman.adv recently.

We know that batman.adv works on layer 2. When the network topology change, batman.adv can know this change and handle it. But the IP layer doesn't know that. How to make IP layer handle the change of network topology?

For example, I have 3 mesh nodes, client node A, gateway node B and geteway node C. A connects to internet via B. Then I shutdown B. I guess A will switch to C as it's gateway node automatically. But it's not so. A continuously send the ARP request packet to search the MAC address of B. The default gateway is still B, not C.

So, how should I do to make the IP layer be aware of that the gateway has swithed to another one?

Thanks! Best regards.

liu