[PATCH RESEND v2] wifi: mac80211: queue frames while off-channel

[Stanislaw Gruszka <stf_xl@wp.pl>]

Drivers without FAST_XMIT and hardware scan support currently drop TX
frames during software scanning while being off-channel. This happens
in ieee80211_tx_h_check_assoc() before frames reach internal TX queue.

Move the off-channel check to invoke_tx_handlers_late(), after
ieee80211_queue_skb(). Frames can then remain queued and be transmitted
when the interface returns on-channel. This how TX works currently when
code goes via ieee80211_xmit_fast() path.

Below is rt2x00 driver ping output example while scanning, before and
after the fix. After the fix, packets are no longer lost. Some have
increased latency, what is expected behavior.

BEFORE:
64 bytes from 192.168.0.1: icmp_seq=29 ttl=64 time=3.61 ms
64 bytes from 192.168.0.1: icmp_seq=31 ttl=64 time=3.33 ms # Missed 30
64 bytes from 192.168.0.1: icmp_seq=32 ttl=64 time=4.03 ms
64 bytes from 192.168.0.1: icmp_seq=34 ttl=64 time=3.10 ms # Missed 33
64 bytes from 192.168.0.1: icmp_seq=36 ttl=64 time=3.04 ms # Missed 35
64 bytes from 192.168.0.1: icmp_seq=38 ttl=64 time=3.05 ms # Missed 37
64 bytes from 192.168.0.1: icmp_seq=40 ttl=64 time=4.14 ms # Missed 39
64 bytes from 192.168.0.1: icmp_seq=41 ttl=64 time=4.50 ms

AFTER:
64 bytes from 192.168.0.1: icmp_seq=29 ttl=64 time=3.40 ms
64 bytes from 192.168.0.1: icmp_seq=30 ttl=64 time=6.10 ms
64 bytes from 192.168.0.1: icmp_seq=31 ttl=64 time=4.69 ms
64 bytes from 192.168.0.1: icmp_seq=32 ttl=64 time=4.49 ms
64 bytes from 192.168.0.1: icmp_seq=33 ttl=64 time=148 ms
64 bytes from 192.168.0.1: icmp_seq=34 ttl=64 time=6.83 ms
64 bytes from 192.168.0.1: icmp_seq=35 ttl=64 time=8.66 ms
64 bytes from 192.168.0.1: icmp_seq=36 ttl=64 time=13.0 ms
64 bytes from 192.168.0.1: icmp_seq=37 ttl=64 time=4.78 ms
64 bytes from 192.168.0.1: icmp_seq=38 ttl=64 time=3.85 ms

Cc: <stable@vger.kernel.org>
Signed-off-by: Stanislaw Gruszka <stf_xl@wp.pl>
---
v1 -> v2: 
 - drop wrong Fixes tags 
 - move handler function to keep order in the code  
 - do not remove info->flags & IEEE80211_TX_CTL_INJECTED check
 
 net/mac80211/tx.c | 52 +++++++++++++++++++++++++----------------------
 1 file changed, 28 insertions(+), 24 deletions(-)

diff --git a/net/mac80211/tx.c b/net/mac80211/tx.c
index 91b14112e24f..08a39272f26a 100644
--- a/net/mac80211/tx.c
+++ b/net/mac80211/tx.c
@@ -269,7 +269,6 @@ ieee80211_tx_h_dynamic_ps(struct ieee80211_tx_data *tx)
 static ieee80211_tx_result debug_noinline
 ieee80211_tx_h_check_assoc(struct ieee80211_tx_data *tx)
 {
-
 	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
 	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
 	bool assoc = false;
@@ -277,20 +276,6 @@ ieee80211_tx_h_check_assoc(struct ieee80211_tx_data *tx)
 	if (unlikely(info->flags & IEEE80211_TX_CTL_INJECTED))
 		return TX_CONTINUE;
 
-	if (unlikely(test_bit(SCAN_SW_SCANNING, &tx->local->scanning)) &&
-	    test_bit(SDATA_STATE_OFFCHANNEL, &tx->sdata->state) &&
-	    !ieee80211_is_probe_req(hdr->frame_control) &&
-	    !ieee80211_is_any_nullfunc(hdr->frame_control))
-		/*
-		 * When software scanning only nullfunc frames (to notify
-		 * the sleep state to the AP) and probe requests (for the
-		 * active scan) are allowed, all other frames should not be
-		 * sent and we should not get here, but if we do
-		 * nonetheless, drop them to avoid sending them
-		 * off-channel. See __ieee80211_start_scan() for more.
-		 */
-		return TX_DROP;
-
 	if (tx->sdata->vif.type == NL80211_IFTYPE_OCB)
 		return TX_CONTINUE;
 
@@ -805,6 +790,33 @@ ieee80211_tx_h_rate_ctrl(struct ieee80211_tx_data *tx)
 	return TX_CONTINUE;
 }
 
+static ieee80211_tx_result debug_noinline
+ieee80211_tx_h_check_offchannel(struct ieee80211_tx_data *tx)
+{
+	struct ieee80211_hdr *hdr = (struct ieee80211_hdr *)tx->skb->data;
+	struct ieee80211_tx_info *info = IEEE80211_SKB_CB(tx->skb);
+
+	if (unlikely(info->flags & IEEE80211_TX_CTL_INJECTED))
+		return TX_CONTINUE;
+
+	if (unlikely(test_bit(SCAN_SW_SCANNING, &tx->local->scanning)) &&
+	    test_bit(SDATA_STATE_OFFCHANNEL, &tx->sdata->state) &&
+	    !ieee80211_is_probe_req(hdr->frame_control) &&
+	    !ieee80211_is_any_nullfunc(hdr->frame_control)) {
+		/*
+		 * When software scanning only nullfunc frames (to notify
+		 * the sleep state to the AP) and probe requests (for the
+		 * active scan) are allowed, all other frames should not be
+		 * sent and we should not get here, but if we do
+		 * nonetheless, drop them to avoid sending them
+		 * off-channel. See __ieee80211_start_scan() for more.
+		 */
+		return TX_DROP;
+	}
+
+	return TX_CONTINUE;
+}
+
 static __le16 ieee80211_tx_next_seq(struct sta_info *sta, int tid)
 {
 	u16 *seq = &sta->tid_seq[tid];
@@ -1864,6 +1876,7 @@ static int invoke_tx_handlers_late(struct ieee80211_tx_data *tx)
 		goto txh_done;
 	}
 
+	CALL_TXH(ieee80211_tx_h_check_offchannel);
 	CALL_TXH(ieee80211_tx_h_michael_mic_add);
 	CALL_TXH(ieee80211_tx_h_sequence);
 	CALL_TXH(ieee80211_tx_h_fragment);
@@ -4686,10 +4699,6 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
 	queue = ieee80211_select_queue(sdata, sta, skb);
 	skb_set_queue_mapping(skb, queue);
 
-	if (unlikely(test_bit(SCAN_SW_SCANNING, &local->scanning)) &&
-	    test_bit(SDATA_STATE_OFFCHANNEL, &sdata->state))
-		goto out_free;
-
 	skb = skb_share_check(skb, GFP_ATOMIC);
 	if (unlikely(!skb))
 		return;
@@ -4756,11 +4765,6 @@ static void ieee80211_8023_xmit(struct ieee80211_sub_if_data *sdata,
 	ieee80211_tpt_led_trig_tx(local, len);
 
 	ieee80211_tx_8023(sdata, skb, sta, false);
-
-	return;
-
-out_free:
-	kfree_skb(skb);
 }
 
 static bool ieee80211_check_mcast_offload(struct ieee80211_sub_if_data *sdata,
-- 
2.50.1