unregister_netdevice: waiting for batadv_slave_0 to become free. Usage count = 2
ref_tracker: batadv_slave_0@ffff88807aea65b8 has 1/1 users at
     __netdev_tracker_alloc include/linux/netdevice.h:4110 [inline]
     netdev_tracker_alloc include/linux/netdevice.h:4122 [inline]
     netdev_get_by_index+0x79/0xa0 net/core/dev.c:898
     fib6_nh_init+0x1ce/0x1fe0 net/ipv6/route.c:3574
     nh_create_ipv6 net/ipv4/nexthop.c:2590 [inline]
     nexthop_create net/ipv4/nexthop.c:2641 [inline]
     nexthop_add net/ipv4/nexthop.c:2683 [inline]
     rtm_new_nexthop+0x28d7/0x64b0 net/ipv4/nexthop.c:2962
     rtnetlink_rcv_msg+0x7c7/0xf10 net/core/rtnetlink.c:6475
     netlink_rcv_skb+0x216/0x480 net/netlink/af_netlink.c:2537
     netlink_unicast_kernel net/netlink/af_netlink.c:1323 [inline]
     netlink_unicast+0x750/0x8c0 net/netlink/af_netlink.c:1349
     netlink_sendmsg+0x8c1/0xbe0 net/netlink/af_netlink.c:1891
     sock_sendmsg_nosec net/socket.c:730 [inline]
     __sock_sendmsg net/socket.c:745 [inline]
     ____sys_sendmsg+0x5bf/0x950 net/socket.c:2595
     ___sys_sendmsg+0x220/0x290 net/socket.c:2649
     __sys_sendmsg net/socket.c:2678 [inline]
     __do_sys_sendmsg net/socket.c:2687 [inline]
     __se_sys_sendmsg+0x1a5/0x270 net/socket.c:2685
     do_syscall_x64 arch/x86/entry/common.c:51 [inline]
     do_syscall_64+0x55/0xb0 arch/x86/entry/common.c:81
     entry_SYSCALL_64_after_hwframe+0x68/0xd2