wifi: iwlwifi: mvm: simplify by using SKB MAC header pointer

Instead of calculating the offset to the 802.11 header based on radiotap
bits and length, shorten the code path by always setting the MAC header
in the skb and using skb_mac_header().
Signed-off-by: Mordechay Goodstein <mordechay.goodstein@intel.com>
Link: https://lore.kernel.org/r/20230127002430.3ec5493934a4.I1d41a2af28588b5899fcd2402f8c4bd8cc29a12e@changeidSigned-off-by: Gregory Greenman <gregory.greenman@intel.com>

drivers/net/wireless/intel/iwlwifi/mvm/rxmq.c

@@ -10,37 +10,11 @@
 #include "mvm.h"
 #include "fw-api.h"
 
-static void *iwl_mvm_skb_get_hdr(struct sk_buff *skb)
-{
-	struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
-	u8 *data = skb->data;
-
-	/* Alignment concerns */
-	BUILD_BUG_ON(sizeof(struct ieee80211_radiotap_he) % 4);
-	BUILD_BUG_ON(sizeof(struct ieee80211_radiotap_he_mu) % 4);
-	BUILD_BUG_ON(sizeof(struct ieee80211_radiotap_lsig) % 4);
-	BUILD_BUG_ON(sizeof(struct ieee80211_vendor_radiotap) % 4);
-
-	if (rx_status->flag & RX_FLAG_RADIOTAP_HE)
-		data += sizeof(struct ieee80211_radiotap_he);
-	if (rx_status->flag & RX_FLAG_RADIOTAP_HE_MU)
-		data += sizeof(struct ieee80211_radiotap_he_mu);
-	if (rx_status->flag & RX_FLAG_RADIOTAP_LSIG)
-		data += sizeof(struct ieee80211_radiotap_lsig);
-	if (rx_status->flag & RX_FLAG_RADIOTAP_VENDOR_DATA) {
-		struct ieee80211_vendor_radiotap *radiotap = (void *)data;
-
-		data += sizeof(*radiotap) + radiotap->len + radiotap->pad;
-	}
-
-	return data;
-}
-
 static inline int iwl_mvm_check_pn(struct iwl_mvm *mvm, struct sk_buff *skb,
 				   int queue, struct ieee80211_sta *sta)
 {
 	struct iwl_mvm_sta *mvmsta;
-	struct ieee80211_hdr *hdr = iwl_mvm_skb_get_hdr(skb);
+	struct ieee80211_hdr *hdr = (void *)skb_mac_header(skb);
 	struct ieee80211_rx_status *stats = IEEE80211_SKB_RXCB(skb);
 	struct iwl_mvm_key_pn *ptk_pn;
 	int res;
@@ -179,6 +153,10 @@ static int iwl_mvm_create_skb(struct iwl_mvm *mvm, struct sk_buff *skb,
 	if (unlikely(headlen < hdrlen))
 		return -EINVAL;
 
+	/* Since data doesn't move data while putting data on skb and that is
+	 * the only way we use, data + len is the next place that hdr would be put
+	 */
+	skb_set_mac_header(skb, skb->len);
 	skb_put_data(skb, hdr, hdrlen);
 	skb_put_data(skb, (u8 *)hdr + hdrlen + pad_len, headlen - hdrlen);
 
@@ -936,7 +914,7 @@ static bool iwl_mvm_reorder(struct iwl_mvm *mvm,
 			    struct iwl_rx_mpdu_desc *desc)
 {
 	struct ieee80211_rx_status *rx_status = IEEE80211_SKB_RXCB(skb);
-	struct ieee80211_hdr *hdr = iwl_mvm_skb_get_hdr(skb);
+	struct ieee80211_hdr *hdr = (void *)skb_mac_header(skb);
 	struct iwl_mvm_sta *mvm_sta;
 	struct iwl_mvm_baid_data *baid_data;
 	struct iwl_mvm_reorder_buffer *buffer;
@@ -2159,6 +2137,16 @@ void iwl_mvm_rx_monitor_no_data(struct iwl_mvm *mvm, struct napi_struct *napi,
 
 	iwl_mvm_rx_fill_status(mvm, skb, &phy_data, queue);
 
+	/* no more radio tap info should be put after this point.
+	 *
+	 * We mark it as mac header, for upper layers to know where
+	 * all radio tap header ends.
+	 *
+	 * Since data doesn't move data while putting data on skb and that is
+	 * the only way we use, data + len is the next place that hdr would be put
+	 */
+	skb_set_mac_header(skb, skb->len);
+
 	/*
 	 * Override the nss from the rx_vec since the rate_n_flags has
 	 * only 2 bits for the nss which gives a max of 4 ss but there