2013-01-11 19:33:25

by Christian Lamparter

[permalink] [raw]
Subject: [RFC] ath9k: report A-MPDU status

The ath9k hardware reports whenever an frame was part
of an A-MPDU. MAC80211 already provides the necessary
API to pass this additional information along to
whomever needs it.

Knowing whenever a received frame was part of an A-MPDU
allows mac80211 to react to A-MPDUs which have no valid
BA agreement in place.

This patch (together with the mac80211 part in:
helps to improve network stability. The new code implements
parts of the recommendations from 802.11-2012 10.5.4
"Error recovery upon a peer failure".

While this patch works OK, I think it still needs be
improved further:
- ath9k_apply_ampdu_details is a separate subroutine
and it is called a bit 'late'. However, I'm not
sure if moving it to a different place like
would be any better. it's because we need to have
access to ampdu_ref, which is currently stored in

- What about the MPDU delimiter crc?
Is it possible to retrieve it from the rx header,
or is it lost?

- (How to handle zero length subframes?
This would be a nice to have feature [i.e.: if
someone wants to check if a HT peer really
cares about the ampdu density]. However it
should be disabled unless we have a running
monitor interface.)

BTW: Support for the AMPDU_DETAILS radiotap
extension has already been added to wireshark.
Just make sure you get the latest svn/git
source (1.9.0).

drivers/net/wireless/ath/ath9k/ath9k.h | 2 ++
drivers/net/wireless/ath/ath9k/recv.c | 21 +++++++++++++++++++++
2 files changed, 23 insertions(+)

diff --git a/drivers/net/wireless/ath/ath9k/ath9k.h b/drivers/net/wireless/ath/ath9k/ath9k.h
index 094a932..262fb71 100644
--- a/drivers/net/wireless/ath/ath9k/ath9k.h
+++ b/drivers/net/wireless/ath/ath9k/ath9k.h
@@ -320,6 +320,8 @@ struct ath_rx {
struct ath_rx_edma rx_edma[ATH9K_RX_QUEUE_MAX];

struct sk_buff *frag;
+ u32 ampdu_ref;

int ath_startrecv(struct ath_softc *sc);
diff --git a/drivers/net/wireless/ath/ath9k/recv.c b/drivers/net/wireless/ath/ath9k/recv.c
index 45f2d47..775cafd 100644
--- a/drivers/net/wireless/ath/ath9k/recv.c
+++ b/drivers/net/wireless/ath/ath9k/recv.c
@@ -1128,6 +1128,24 @@ static void ath_process_fft(struct ath_softc *sc, struct ieee80211_hdr *hdr,

+static void ath9k_apply_ampdu_details(struct ath_softc *sc,
+ struct ath_rx_status *rs, struct ieee80211_rx_status *rxs)
+ if (rs->rs_isaggr) {
+ rxs->ampdu_reference = sc->rx.ampdu_ref;
+ if (!rs->rs_moreaggr) {
+ rxs->flag |= RX_FLAG_AMPDU_IS_LAST;
+ sc->rx.ampdu_ref++;
+ }
+ if (rs->rs_flags & ATH9K_RX_DELIM_CRC_PRE)
+ }
int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
struct ath_buf *bf;
@@ -1343,6 +1362,8 @@ int ath_rx_tasklet(struct ath_softc *sc, int flush, bool hp)
if ((ah->caps.hw_caps & ATH9K_HW_CAP_ANT_DIV_COMB) && sc->ant_rx == 3)
ath_ant_comb_scan(sc, &rs);

+ ath9k_apply_ampdu_details(sc, &rs, rxs);
ieee80211_rx(hw, skb);