mac80211: add radiotap flag to prevent sequence number overwrite

The radiotap specification contains a flag to indicate that the sequence
number of an injected frame should not be overwritten. Parse this flag
and define and set a corresponding Tx control flag.
Signed-off-by: Mathy Vanhoef <Mathy.Vanhoef@kuleuven.be>
Link: https://lore.kernel.org/r/20200723100153.31631-2-Mathy.Vanhoef@kuleuven.beSigned-off-by: Johannes Berg <johannes.berg@intel.com>

include/net/ieee80211_radiotap.h

@@ -117,6 +117,7 @@ enum ieee80211_radiotap_tx_flags {
 	IEEE80211_RADIOTAP_F_TX_CTS = 0x0002,
 	IEEE80211_RADIOTAP_F_TX_RTS = 0x0004,
 	IEEE80211_RADIOTAP_F_TX_NOACK = 0x0008,
+	IEEE80211_RADIOTAP_F_TX_NOSEQNO = 0x0010,
 };
 
 /* for IEEE80211_RADIOTAP_MCS "have" flags */

include/net/mac80211.h

@@ -825,6 +825,8 @@ enum mac80211_tx_info_flags {
  * @IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP: This frame skips mesh path lookup
  * @IEEE80211_TX_CTRL_HW_80211_ENCAP: This frame uses hardware encapsulation
  *	(header conversion)
+ * @IEEE80211_TX_CTRL_NO_SEQNO: Do not overwrite the sequence number that
+ *	has already been assigned to this frame.
  *
  * These flags are used in tx_info->control.flags.
  */
@@ -836,6 +838,7 @@ enum mac80211_tx_control_flags {
 	IEEE80211_TX_CTRL_FAST_XMIT		= BIT(4),
 	IEEE80211_TX_CTRL_SKIP_MPATH_LOOKUP	= BIT(5),
 	IEEE80211_TX_CTRL_HW_80211_ENCAP	= BIT(6),
+	IEEE80211_TX_CTRL_NO_SEQNO		= BIT(7),
 };
 
 /*

net/mac80211/tx.c

@@ -2085,6 +2085,8 @@ static bool ieee80211_parse_tx_radiotap(struct ieee80211_local *local,
 			txflags = get_unaligned_le16(iterator.this_arg);
 			if (txflags & IEEE80211_RADIOTAP_F_TX_NOACK)
 				info->flags |= IEEE80211_TX_CTL_NO_ACK;
+			if (txflags & IEEE80211_RADIOTAP_F_TX_NOSEQNO)
+				info->control.flags |= IEEE80211_TX_CTRL_NO_SEQNO;
 			break;
 
 		case IEEE80211_RADIOTAP_RATE: