ll_header
struct ll_header header;
struct ll_header *header = (struct ll_header *)pskb->data;
#define LL_HEADER_LENGTH (sizeof(struct ll_header))
bool (*validate)(const char *ll_header, unsigned int len);
char *ll_header, int len)
memset(ll_header + len, 0, dev->hard_header_len - len);
return dev->header_ops->validate(ll_header, len);