mac80211: provide sequence numbers

I've come to think that not providing sequence numbers for
the normal STA mode case was a mistake, at least two drivers
now had to implement code they wouldn't otherwise need, and
I believe at76_usb and adm8211 might be broken.

This patch makes mac80211 assign a sequence number to all
those frames that need one except beacons. That means that
if a driver only implements modes that do not do beaconing
it need not worry about the sequence number.

Signed-off-by: Johannes Berg <johannes@sipsolutions.net>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 22494bc..8bcabef 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -600,8 +600,18 @@
 	if (ieee80211_hdrlen(hdr->frame_control) < 24)
 		return TX_CONTINUE;
 
+	/*
+	 * Anything but QoS data that has a sequence number field
+	 * (is long enough) gets a sequence number from the global
+	 * counter.
+	 */
 	if (!ieee80211_is_data_qos(hdr->frame_control)) {
+		/* driver should assign sequence number */
 		info->flags |= IEEE80211_TX_CTL_ASSIGN_SEQ;
+		/* for pure STA mode without beacons, we can do it */
+		hdr->seq_ctrl = cpu_to_le16(tx->sdata->sequence_number);
+		tx->sdata->sequence_number += 0x10;
+		tx->sdata->sequence_number &= IEEE80211_SCTL_SEQ;
 		return TX_CONTINUE;
 	}