mac80211: implement off-channel mgmt TX

This implements the new off-channel TX API
in mac80211 with a new work item type. The
operation doesn't add a new work item when
we're on the right channel and there's no
wait time so that for example p2p probe
responses will be transmitted without delay.

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

4 files changed, 129 insertions, 6 deletions

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index aac2d7de828e..db134b500caa 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1551,6 +1551,28 @@ static int ieee80211_cancel_remain_on_channel(struct wiphy *wiphy,
         return ieee80211_wk_cancel_remain_on_channel(sdata, cookie);
 }
 
+static enum work_done_result
+ieee80211_offchan_tx_done(struct ieee80211_work *wk, struct sk_buff *skb)
+{
+        /*
+         * Use the data embedded in the work struct for reporting
+         * here so if the driver mangled the SKB before dropping
+         * it (which is the only way we really should get here)
+         * then we don't report mangled data.
+         *
+         * If there was no wait time, then by the time we get here
+         * the driver will likely not have reported the status yet,
+         * so in that case userspace will have to deal with it.
+         */
+
+        if (wk->offchan_tx.wait && wk->offchan_tx.frame)
+                cfg80211_mgmt_tx_status(wk->sdata->dev,
+                                        (unsigned long) wk->offchan_tx.frame,
+                                        wk->ie, wk->ie_len, false, GFP_KERNEL);
+
+        return WORK_DONE_DESTROY;
+}
+
 static int ieee80211_mgmt_tx(struct wiphy *wiphy, struct net_device *dev,
                              struct ieee80211_channel *chan, bool offchan,
                              enum nl80211_channel_type channel_type,
@@ -1561,20 +1583,22 @@ static int ieee80211_mgmt_tx(struct wiphy *wiphy, struct net_device *dev,
         struct ieee80211_local *local = sdata->local;
         struct sk_buff *skb;
         struct sta_info *sta;
+        struct ieee80211_work *wk;
         const struct ieee80211_mgmt *mgmt = (void *)buf;
         u32 flags = IEEE80211_TX_INTFL_NL80211_FRAME_TX |
                     IEEE80211_TX_CTL_REQ_TX_STATUS;
-
-        if (offchan)
-                return -EOPNOTSUPP;
+        bool is_offchan = false;
 
         /* Check that we are on the requested channel for transmission */
         if (chan != local->tmp_channel &&
             chan != local->oper_channel)
-                return -EBUSY;
+                is_offchan = true;
         if (channel_type_valid &&
             (channel_type != local->tmp_channel_type &&
              channel_type != local->_oper_channel_type))
+                is_offchan = true;
+
+        if (is_offchan && !offchan)
                 return -EBUSY;
 
         switch (sdata->vif.type) {
@@ -1608,12 +1632,70 @@ static int ieee80211_mgmt_tx(struct wiphy *wiphy, struct net_device *dev,
         IEEE80211_SKB_CB(skb)->flags = flags;
 
         skb->dev = sdata->dev;
-        ieee80211_tx_skb(sdata, skb);
 
         *cookie = (unsigned long) skb;
+
+        /*
+         * Can transmit right away if the channel was the
+         * right one and there's no wait involved... If a
+         * wait is involved, we might otherwise not be on
+         * the right channel for long enough!
+         */
+        if (!is_offchan && !wait && !sdata->vif.bss_conf.idle) {
+                ieee80211_tx_skb(sdata, skb);
+                return 0;
+        }
+
+        wk = kzalloc(sizeof(*wk) + len, GFP_KERNEL);
+        if (!wk) {
+                kfree_skb(skb);
+                return -ENOMEM;
+        }
+
+        wk->type = IEEE80211_WORK_OFFCHANNEL_TX;
+        wk->chan = chan;
+        wk->sdata = sdata;
+        wk->done = ieee80211_offchan_tx_done;
+        wk->offchan_tx.frame = skb;
+        wk->offchan_tx.wait = wait;
+        wk->ie_len = len;
+        memcpy(wk->ie, buf, len);
+
+        ieee80211_add_work(wk);
         return 0;
 }
 
+static int ieee80211_mgmt_tx_cancel_wait(struct wiphy *wiphy,
+                                         struct net_device *dev,
+                                         u64 cookie)
+{
+        struct ieee80211_sub_if_data *sdata = IEEE80211_DEV_TO_SUB_IF(dev);
+        struct ieee80211_local *local = sdata->local;
+        struct ieee80211_work *wk;
+        int ret = -ENOENT;
+
+        mutex_lock(&local->mtx);
+        list_for_each_entry(wk, &local->work_list, list) {
+                if (wk->sdata != sdata)
+                        continue;
+
+                if (wk->type != IEEE80211_WORK_OFFCHANNEL_TX)
+                        continue;
+
+                if (cookie != (unsigned long) wk->offchan_tx.frame)
+                        continue;
+
+                wk->timeout = jiffies;
+
+                ieee80211_queue_work(&local->hw, &local->work_work);
+                ret = 0;
+                break;
+        }
+        mutex_unlock(&local->mtx);
+
+        return ret;
+}
+
 static void ieee80211_mgmt_frame_register(struct wiphy *wiphy,
                                           struct net_device *dev,
                                           u16 frame_type, bool reg)
@@ -1698,6 +1780,7 @@ struct cfg80211_ops mac80211_config_ops = {
         .remain_on_channel = ieee80211_remain_on_channel,
         .cancel_remain_on_channel = ieee80211_cancel_remain_on_channel,
         .mgmt_tx = ieee80211_mgmt_tx,
+        .mgmt_tx_cancel_wait = ieee80211_mgmt_tx_cancel_wait,
         .set_cqm_rssi_config = ieee80211_set_cqm_rssi_config,
         .mgmt_frame_register = ieee80211_mgmt_frame_register,
         .set_antenna = ieee80211_set_antenna,
diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 5bc0745368fe..66b0b52b828d 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -260,6 +260,7 @@ enum ieee80211_work_type {
         IEEE80211_WORK_ASSOC_BEACON_WAIT,
         IEEE80211_WORK_ASSOC,
         IEEE80211_WORK_REMAIN_ON_CHANNEL,
+        IEEE80211_WORK_OFFCHANNEL_TX,
 };
 
 /**
@@ -320,6 +321,10 @@ struct ieee80211_work {
                 struct {
                         u32 duration;
                 } remain;
+                struct {
+                        struct sk_buff *frame;
+                        u32 wait;
+                } offchan_tx;
         };
 
         int ie_len;
diff --git a/net/mac80211/status.c b/net/mac80211/status.c
index bed7e32ed908..4958710a7d92 100644
--- a/net/mac80211/status.c
+++ b/net/mac80211/status.c
@@ -321,10 +321,23 @@ void ieee80211_tx_status(struct ieee80211_hw *hw, struct sk_buff *skb)
                                         msecs_to_jiffies(10));
         }
 
-        if (info->flags & IEEE80211_TX_INTFL_NL80211_FRAME_TX)
+        if (info->flags & IEEE80211_TX_INTFL_NL80211_FRAME_TX) {
+                struct ieee80211_work *wk;
+
+                rcu_read_lock();
+                list_for_each_entry_rcu(wk, &local->work_list, list) {
+                        if (wk->type != IEEE80211_WORK_OFFCHANNEL_TX)
+                                continue;
+                        if (wk->offchan_tx.frame != skb)
+                                continue;
+                        wk->offchan_tx.frame = NULL;
+                        break;
+                }
+                rcu_read_unlock();
                 cfg80211_mgmt_tx_status(
                         skb->dev, (unsigned long) skb, skb->data, skb->len,
                         !!(info->flags & IEEE80211_TX_STAT_ACK), GFP_ATOMIC);
+        }
 
         /* this was a transmitted frame, but now we want to reuse it */
         skb_orphan(skb);
diff --git a/net/mac80211/work.c b/net/mac80211/work.c
index ae344d1ba056..2b5c3f267198 100644
--- a/net/mac80211/work.c
+++ b/net/mac80211/work.c
@@ -561,6 +561,25 @@ ieee80211_remain_on_channel_timeout(struct ieee80211_work *wk)
 }
 
 static enum work_action __must_check
+ieee80211_offchannel_tx(struct ieee80211_work *wk)
+{
+        if (!wk->started) {
+                wk->timeout = jiffies + msecs_to_jiffies(wk->offchan_tx.wait);
+
+                /*
+                 * After this, offchan_tx.frame remains but now is no
+                 * longer a valid pointer -- we still need it as the
+                 * cookie for canceling this work.
+                 */
+                ieee80211_tx_skb(wk->sdata, wk->offchan_tx.frame);
+
+                return WORK_ACT_NONE;
+        }
+
+        return WORK_ACT_TIMEOUT;
+}
+
+static enum work_action __must_check
 ieee80211_assoc_beacon_wait(struct ieee80211_work *wk)
 {
         if (wk->started)
@@ -955,6 +974,9 @@ static void ieee80211_work_work(struct work_struct *work)
                 case IEEE80211_WORK_REMAIN_ON_CHANNEL:
                         rma = ieee80211_remain_on_channel_timeout(wk);
                         break;
+                case IEEE80211_WORK_OFFCHANNEL_TX:
+                        rma = ieee80211_offchannel_tx(wk);
+                        break;
                 case IEEE80211_WORK_ASSOC_BEACON_WAIT:
                         rma = ieee80211_assoc_beacon_wait(wk);
                         break;