How to use AUTO-IP in lwip

I am trying to setup link-local addressing of my nucleo F767ZI board. I understand there is support for it in the lwip stack, but It doesn’t seem to startup. I have added “LWIP_AUTOIP=1” in custom_targets.json

   #include "autoip.h"
   #include "LWIPStack.h"


    EthernetInterface eth;
    extern struct netif *netif_default;  
    nsapi_error_t res = eth.connect();

    SocketAddress addr;
    printf(" ip: %s \r\n", addr.get_ip_address());

Output is
ip: (null)

Is there any way to reach the default netif directly from Ethernet interface? In the EthernetInterface class netif_default is protected. Have anyone managed to run AUTOIP

Thank you