mac80211: Fill in skb->protocol information for injected frames

Some drivers (ath9k for example) are using skb->protocol to treat EAPOL
frames somehow special (disallow aggregation for example).

When running in AP mode hostapd injects the EAPOL frames through a
monitor interface and thus skb->protocol isn't set at all. Hence, if the
injected frame is a data frame and carries a rfc1042 headaer update the
skb->protocol field accordingly.

Signed-off-by: Helmut Schaa <helmut.schaa@googlemail.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

net/mac80211/tx.c

@@ -1608,7 +1608,9 @@ netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb,
 	struct ieee80211_radiotap_header *prthdr =
 		(struct ieee80211_radiotap_header *)skb->data;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(skb);
+	struct ieee80211_hdr *hdr;
 	u16 len_rthdr;
+	u8 *payload;
 
 	/*
 	 * Frame injection is not allowed if beaconing is not allowed
@@ -1659,6 +1661,24 @@ netdev_tx_t ieee80211_monitor_start_xmit(struct sk_buff *skb,
 	skb_set_network_header(skb, len_rthdr);
 	skb_set_transport_header(skb, len_rthdr);
 
+	/*
+	 * Initialize skb->protocol if the injected frame is a data frame
+	 * carrying a rfc1042 header
+	 */
+	if (skb->len > len_rthdr + 2) {
+		hdr = (struct ieee80211_hdr *)(skb->data + len_rthdr);
+		if (ieee80211_is_data(hdr->frame_control) &&
+		    skb->len >= len_rthdr +
+				ieee80211_hdrlen(hdr->frame_control) +
+				sizeof(rfc1042_header) + 2) {
+			payload = (u8 *)hdr +
+				  ieee80211_hdrlen(hdr->frame_control);
+			if (compare_ether_addr(payload, rfc1042_header) == 0)
+				skb->protocol = cpu_to_be16((payload[6] << 8) |
+							    payload[7]);
+		}
+	}
+
 	memset(info, 0, sizeof(*info));
 
 	info->flags |= IEEE80211_TX_CTL_REQ_TX_STATUS;