mac80211: reply only once to each PS-poll

If a PS-poll frame is retried (but was received)
there is no way to detect that since it has no
sequence number. As a consequence, the standard
asks us to not react to PS-poll frames until the
response to one made it out (was ACKed or lost).

Implement this by using the WLAN_STA_SP flags to
also indicate a PS-Poll "service period" and the
IEEE80211_TX_STATUS_EOSP flag for the response
packet to indicate the end of the "SP" as usual.

We could use separate flags, but that will most
likely completely confuse drivers, and while the
standard doesn't exclude simultaneously polling
using uAPSD and PS-Poll, doing that seems quite
problematic.

Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>

1 files changed, 8 insertions, 1 deletions

diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index dd07964ef154..ee6449eff7dc 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -370,7 +370,8 @@ struct ieee80211_bss_conf {
  * @IEEE80211_TX_STATUS_EOSP: This packet marks the end of service period,
  *      when its status is reported the service period ends. For frames in
  *      an SP that mac80211 transmits, it is already set; for driver frames
- *      the driver may set this flag.
+ *      the driver may set this flag. It is also used to do the same for
+ *      PS-Poll responses.
  *
  * Note: If you have to add new flags to the enumeration, then don't
  *       forget to update %IEEE80211_TX_TEMPORARY_FLAGS when necessary.
@@ -1959,6 +1960,12 @@ enum ieee80211_frame_release_type {
  *      more-data bit must always be set.
  *      The @tids parameter tells the driver which TIDs to release frames
  *      from, for PS-poll it will always have only a single bit set.
+ *      In the case this is used for a PS-poll initiated release, the
+ *      @num_frames parameter will always be 1 so code can be shared. In
+ *      this case the driver must also set %IEEE80211_TX_STATUS_EOSP flag
+ *      on the TX status (and must report TX status) so that the PS-poll
+ *      period is properly ended. This is used to avoid sending multiple
+ *      responses for a retried PS-poll frame.
  *      In the case this is used for uAPSD, the @num_frames parameter may be
  *      bigger than one, but the driver may send fewer frames (it must send
  *      at least one, however). In this case it is also responsible for