batadv_max_header_len
needed_headroom += batadv_max_header_len();
return min_t(int, min_mtu - batadv_max_header_len(), BATADV_MAX_MTU);
int max_header_len = batadv_max_header_len();
int batadv_max_header_len(void);
#define BATADV_MAX_MTU (ETH_MAX_MTU - batadv_max_header_len())