BATADV_DHCP_CHADDR_LEN
chaddr = skb_header_pointer(skb, offset, BATADV_DHCP_CHADDR_LEN, buf);
memcpy(buf, chaddr, BATADV_DHCP_CHADDR_LEN);
u8 chaddr[BATADV_DHCP_CHADDR_LEN];
u8 chaddr[BATADV_DHCP_CHADDR_LEN];