[PATCH] mac80211: assign seqnums for group QoS frames

[PATCH] mac80211: assign seqnums for group QoS frames

[Bob Copeland]

According to 802.11-2012 9.3.2.10, paragraph 4, QoS
data frames with a group address in the Address 1 field
have sequence numbers allocated from the same counter
as non-QoS data and management frames.  Without this
flag, some drivers may not assign sequence numbers, and
in rare cases frames might get dropped.  Set the control
flag accordingly.

Signed-off-by: Bob Copeland <bob@cozybit.com>

---
I noticed seq=0 on DHCP/mDNS frames with mesh on certain
hardware (since mesh sends all data frames as QoS).
Johannes pointed out this only causes issues if a unicast
frame with seq=0 has retries, and if the receiver caches
seqnums from multicast frames (mac80211 does not).

 net/mac80211/tx.c |    6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 098ae85..3456c04 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -781,9 +781,11 @@ ieee80211_tx_h_sequence(struct ieee80211_tx_data *tx)
 	/*
 	 * Anything but QoS data that has a sequence number field
 	 * (is long enough) gets a sequence number from the global
-	 * counter.
+	 * counter.  QoS data frames with a multicast destination
+	 * also use the global counter (802.11-2012 9.3.2.10).
 	 */
-	if (!ieee80211_is_data_qos(hdr->frame_control)) {
+	if (!ieee80211_is_data_qos(hdr->frame_control) ||
+	    is_multicast_ether_addr(hdr->addr1)) {
 		/* driver should assign sequence number */
 		info->flags |= IEEE80211_TX_CTL_ASSIGN_SEQ;
 		/* for pure STA mode without beacons, we can do it */
-- 
1.7.10.4

Re: [PATCH] mac80211: assign seqnums for group QoS frames

[Johannes Berg]

On Fri, 2013-08-23 at 09:35 -0400, Bob Copeland wrote:
> According to 802.11-2012 9.3.2.10, paragraph 4, QoS
> data frames with a group address in the Address 1 field
> have sequence numbers allocated from the same counter
> as non-QoS data and management frames.  Without this
> flag, some drivers may not assign sequence numbers, and
> in rare cases frames might get dropped.  Set the control
> flag accordingly.

Applied (to -next), thanks.

johannes