static bool ieee80211_amsdu_prepare_head(struct ieee80211_sub_if_data *sdata,
					 struct ieee80211_fast_tx *fast_tx,
					 struct sk_buff *skb)
{
	struct ieee80211_local *local = sdata->local;
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
	struct ieee80211_hdr *hdr;
	struct ethhdr *amsdu_hdr;
	int hdr_len = fast_tx->hdr_len - sizeof(rfc1042_header);
	int subframe_len = skb->len - hdr_len;
	void *data;
	u8 *qc, *h_80211_src, *h_80211_dst;
	const u8 *bssid;

	if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
		return false;

	if (info->control.flags & IEEE80211_TX_CTRL_AMSDU)
		return true;

	if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(*amsdu_hdr)))
		return false;

	data = skb_push(skb, sizeof(*amsdu_hdr));
	memmove(data, data + sizeof(*amsdu_hdr), hdr_len);
	hdr = data;
	amsdu_hdr = data + hdr_len;
	/* h_80211_src/dst is addr* field within hdr */
	h_80211_src = data + fast_tx->sa_offs;
	h_80211_dst = data + fast_tx->da_offs;

	amsdu_hdr->h_proto = cpu_to_be16(subframe_len);
	ether_addr_copy(amsdu_hdr->h_source, h_80211_src);
	ether_addr_copy(amsdu_hdr->h_dest, h_80211_dst);

	/* according to IEEE 802.11-2012 8.3.2 table 8-19, the outer SA/DA
	 * fields needs to be changed to BSSID for A-MSDU frames depending
	 * on FromDS/ToDS values.
	 */
	switch (sdata->vif.type) {
	case NL80211_IFTYPE_STATION:
		bssid = sdata->u.mgd.bssid;
		break;
	case NL80211_IFTYPE_AP:
	case NL80211_IFTYPE_AP_VLAN:
		bssid = sdata->vif.addr;
		break;
	default:
		bssid = NULL;
	}

	if (bssid && ieee80211_has_fromds(hdr->frame_control))
		ether_addr_copy(h_80211_src, bssid);

	if (bssid && ieee80211_has_tods(hdr->frame_control))
		ether_addr_copy(h_80211_dst, bssid);

	qc = ieee80211_get_qos_ctl(hdr);
	*qc |= IEEE80211_QOS_CTL_A_MSDU_PRESENT;

	info->control.flags |= IEEE80211_TX_CTRL_AMSDU;

	return true;
}
static bool ieee80211_amsdu_prepare_head(struct ieee80211_sub_if_data *sdata,
					 struct ieee80211_fast_tx *fast_tx,
					 struct sk_buff *skb)
{
	struct ieee80211_local *local = sdata->local;
	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
	struct ieee80211_hdr *hdr;
	struct ethhdr *amsdu_hdr;
	int hdr_len = fast_tx->hdr_len - sizeof(rfc1042_header);
	int subframe_len = skb->len - hdr_len;
	void *data;
	u8 *qc, *h_80211_src, *h_80211_dst;
	const u8 *bssid;

	if (info->flags & IEEE80211_TX_CTL_RATE_CTRL_PROBE)
		return false;

	if (info->control.flags & IEEE80211_TX_CTRL_AMSDU)
		return true;

	if (!ieee80211_amsdu_realloc_pad(local, skb, sizeof(*amsdu_hdr)))
		return false;

	data = skb_push(skb, sizeof(*amsdu_hdr));
	memmove(data, data + sizeof(*amsdu_hdr), hdr_len);
	hdr = data;
	amsdu_hdr = data + hdr_len;
	 
	h_80211_src = data + fast_tx->sa_offs;
	h_80211_dst = data + fast_tx->da_offs;

	amsdu_hdr->h_proto = cpu_to_be16(subframe_len);
	ether_addr_copy(amsdu_hdr->h_source, h_80211_src);
	ether_addr_copy(amsdu_hdr->h_dest, h_80211_dst);

	 
	switch (sdata->vif.type) {
	case NL80211_IFTYPE_STATION:
		bssid = sdata->u.mgd.bssid;
		break;
	case NL80211_IFTYPE_AP:
	case NL80211_IFTYPE_AP_VLAN:
		bssid = sdata->vif.addr;
		break;
	default:
		bssid = NULL;
	}

	if (bssid && ieee80211_has_fromds(hdr->frame_control))
		ether_addr_copy(h_80211_src, bssid);

	if (bssid && ieee80211_has_tods(hdr->frame_control))
		ether_addr_copy(h_80211_dst, bssid);

	qc = ieee80211_get_qos_ctl(hdr);
	*qc |= IEEE80211_QOS_CTL_A_MSDU_PRESENT;

	info->control.flags |= IEEE80211_TX_CTRL_AMSDU;

	return true;
}