mac80211: introduce flush operation

We've long lacked a good confirmation that frames
have really gone out, e.g. before going off-channel
for a scan. Add a flush() operation that drivers
can implement to provide that confirmation, and use
it in a few places:
 * before scanning sends the nullfunc frames
 * after scanning sends the nullfunc frames, if any
 * when going idle, to send any pending frames

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

6 files changed, 57 insertions, 2 deletions

diff --git a/drivers/net/wireless/mac80211_hwsim.c b/drivers/net/wireless/mac80211_hwsim.c
index 718a5f198c30..4dee69a38c1d 100644
--- a/drivers/net/wireless/mac80211_hwsim.c
+++ b/drivers/net/wireless/mac80211_hwsim.c
@@ -896,6 +896,16 @@ static int mac80211_hwsim_ampdu_action(struct ieee80211_hw *hw,
         return 0;
 }
 
+static void mac80211_hwsim_flush(struct ieee80211_hw *hw, bool drop)
+{
+        /*
+         * In this special case, there's nothing we need to
+         * do because hwsim does transmission synchronously.
+         * In the future, when it does transmissions via
+         * userspace, we may need to do something.
+         */
+}
+
 
 static const struct ieee80211_ops mac80211_hwsim_ops =
 {
@@ -912,6 +922,7 @@ static const struct ieee80211_ops mac80211_hwsim_ops =
         .conf_tx = mac80211_hwsim_conf_tx,
         CFG80211_TESTMODE_CMD(mac80211_hwsim_testmode_cmd)
         .ampdu_action = mac80211_hwsim_ampdu_action,
+        .flush = mac80211_hwsim_flush,
 };
 
 
diff --git a/include/net/mac80211.h b/include/net/mac80211.h
index 494ac69ff477..77ea34b03285 100644
--- a/include/net/mac80211.h
+++ b/include/net/mac80211.h
@@ -1545,6 +1545,10 @@ enum ieee80211_ampdu_mlme_action {
  *      and need to call wiphy_rfkill_set_hw_state() in the callback.
  *
  * @testmode_cmd: Implement a cfg80211 test mode command.
+ *
+ * @flush: Flush all pending frames from the hardware queue, making sure
+ *      that the hardware queues are empty. If the parameter @drop is set
+ *      to %true, pending frames may be dropped.
  */
 struct ieee80211_ops {
         int (*tx)(struct ieee80211_hw *hw, struct sk_buff *skb);
@@ -1601,6 +1605,7 @@ struct ieee80211_ops {
 #ifdef CONFIG_NL80211_TESTMODE
         int (*testmode_cmd)(struct ieee80211_hw *hw, void *data, int len);
 #endif
+        void (*flush)(struct ieee80211_hw *hw, bool drop);
 };
 
 /**
diff --git a/net/mac80211/driver-ops.h b/net/mac80211/driver-ops.h
index 727e4cf7b8a6..cbe133bcdf34 100644
--- a/net/mac80211/driver-ops.h
+++ b/net/mac80211/driver-ops.h
@@ -259,4 +259,11 @@ static inline void drv_rfkill_poll(struct ieee80211_local *local)
         if (local->ops->rfkill_poll)
                 local->ops->rfkill_poll(&local->hw);
 }
+
+static inline void drv_flush(struct ieee80211_local *local, bool drop)
+{
+        trace_drv_flush(local, drop);
+        if (local->ops->flush)
+                local->ops->flush(&local->hw, drop);
+}
 #endif /* __MAC80211_DRIVER_OPS */
diff --git a/net/mac80211/driver-trace.h b/net/mac80211/driver-trace.h
index 7a849b920165..977cc7528bc6 100644
--- a/net/mac80211/driver-trace.h
+++ b/net/mac80211/driver-trace.h
@@ -690,6 +690,27 @@ TRACE_EVENT(drv_ampdu_action,
                 LOCAL_PR_ARG, VIF_PR_ARG, STA_PR_ARG, __entry->action, __entry->tid, __entry->ret
         )
 );
+
+TRACE_EVENT(drv_flush,
+        TP_PROTO(struct ieee80211_local *local, bool drop),
+
+        TP_ARGS(local, drop),
+
+        TP_STRUCT__entry(
+                LOCAL_ENTRY
+                __field(bool, drop)
+        ),
+
+        TP_fast_assign(
+                LOCAL_ASSIGN;
+                __entry->drop = drop;
+        ),
+
+        TP_printk(
+                LOCAL_PR_FMT " drop:%d",
+                LOCAL_PR_ARG, __entry->drop
+        )
+);
 #endif /* !__MAC80211_DRIVER_TRACE || TRACE_HEADER_MULTI_READ */
 
 #undef TRACE_INCLUDE_PATH
diff --git a/net/mac80211/iface.c b/net/mac80211/iface.c
index 1ceca14331d4..389dc8d880f3 100644
--- a/net/mac80211/iface.c
+++ b/net/mac80211/iface.c
@@ -917,6 +917,8 @@ static u32 ieee80211_idle_on(struct ieee80211_local *local)
                wiphy_name(local->hw.wiphy));
 #endif
 
+        drv_flush(local, false);
+
         local->hw.conf.flags |= IEEE80211_CONF_IDLE;
         return IEEE80211_CONF_CHANGE_IDLE;
 }
diff --git a/net/mac80211/scan.c b/net/mac80211/scan.c
index ae1830056521..d98c45e5528b 100644
--- a/net/mac80211/scan.c
+++ b/net/mac80211/scan.c
@@ -418,9 +418,10 @@ static int ieee80211_start_sw_scan(struct ieee80211_local *local)
         local->next_scan_state = SCAN_DECISION;
         local->scan_channel_idx = 0;
 
+        drv_flush(local, false);
+
         ieee80211_configure_filter(local);
 
-        /* TODO: start scan as soon as all nullfunc frames are ACKed */
         ieee80211_queue_delayed_work(&local->hw,
                                      &local->scan_work,
                                      IEEE80211_CHANNEL_TIME);
@@ -584,8 +585,16 @@ static void ieee80211_scan_state_leave_oper_channel(struct ieee80211_local *loca
 
         __set_bit(SCAN_OFF_CHANNEL, &local->scanning);
 
+        /*
+         * What if the nullfunc frames didn't arrive?
+         */
+        drv_flush(local, false);
+        if (local->ops->flush)
+                *next_delay = 0;
+        else
+                *next_delay = HZ / 10;
+
         /* advance to the next channel to be scanned */
-        *next_delay = HZ / 10;
         local->next_scan_state = SCAN_SET_CHANNEL;
 }