rx_radiotap_hdr
struct rx_radiotap_hdr radiotap_hdr;
struct rx_radiotap_hdr *pradiotap_hdr;
radiotap_hdr.hdr.it_len = cpu_to_le16 (sizeof(struct rx_radiotap_hdr));
if ((skb_headroom(skb) < sizeof(struct rx_radiotap_hdr)) &&
pskb_expand_head(skb, sizeof(struct rx_radiotap_hdr), 0, GFP_ATOMIC)) {
pradiotap_hdr = skb_push(skb, sizeof(struct rx_radiotap_hdr));
memcpy(pradiotap_hdr, &radiotap_hdr, sizeof(struct rx_radiotap_hdr));