[3.13.y.z extended stable] Patch "mac80211: fix on-channel remain-on-channel" has been added to staging queue

[Kamal Mostafa]

This is a note to let you know that I have just added a patch titled

    mac80211: fix on-channel remain-on-channel

to the linux-3.13.y-queue branch of the 3.13.y.z extended stable tree 
which can be found at:

 http://kernel.ubuntu.com/git?p=ubuntu/linux.git;a=shortlog;h=refs/heads/linux-3.13.y-queue

This patch is scheduled to be released in version 3.13.11.4.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.13.y.z tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Kamal

------

>From aebe709acfb3faef20e6813eca8ec02effc48a8b Mon Sep 17 00:00:00 2001
From: Johannes Berg <johannes.berg at intel.com>
Date: Wed, 14 May 2014 15:34:41 +0200
Subject: mac80211: fix on-channel remain-on-channel

commit b4b177a5556a686909e643f1e9b6434c10de079f upstream.

Jouni reported that if a remain-on-channel was active on the
same channel as the current operating channel, then the ROC
would start, but any frames transmitted using mgmt-tx on the
same channel would get delayed until after the ROC.

The reason for this is that the ROC starts, but doesn't have
any handling for "remain on the same channel", so it stops
the interface queues. The later mgmt-tx then puts the frame
on the interface queues (since it's on the current operating
channel) and thus they get delayed until after the ROC.

To fix this, add some logic to handle remaining on the same
channel specially and not stop the queues etc. in this case.
This not only fixes the bug but also improves behaviour in
this case as data frames etc. can continue to flow.

Reported-by: Jouni Malinen <j at w1.fi>
Tested-by: Jouni Malinen <j at w1.fi>
Signed-off-by: Johannes Berg <johannes.berg at intel.com>
Signed-off-by: Kamal Mostafa <kamal at canonical.com>
---
 net/mac80211/ieee80211_i.h |  1 +
 net/mac80211/offchannel.c  | 27 ++++++++++++++++++++-------
 2 files changed, 21 insertions(+), 7 deletions(-)

diff --git a/net/mac80211/ieee80211_i.h b/net/mac80211/ieee80211_i.h
index 1fc9190..980d863 100644
--- a/net/mac80211/ieee80211_i.h
+++ b/net/mac80211/ieee80211_i.h
@@ -315,6 +315,7 @@ struct ieee80211_roc_work {

 	bool started, abort, hw_begun, notified;
 	bool to_be_freed;
+	bool on_channel;

 	unsigned long hw_start_time;

diff --git a/net/mac80211/offchannel.c b/net/mac80211/offchannel.c
index 6fb3855..7a17dec 100644
--- a/net/mac80211/offchannel.c
+++ b/net/mac80211/offchannel.c
@@ -333,7 +333,7 @@ void ieee80211_sw_roc_work(struct work_struct *work)
 		container_of(work, struct ieee80211_roc_work, work.work);
 	struct ieee80211_sub_if_data *sdata = roc->sdata;
 	struct ieee80211_local *local = sdata->local;
-	bool started;
+	bool started, on_channel;

 	mutex_lock(&local->mtx);

@@ -354,14 +354,26 @@ void ieee80211_sw_roc_work(struct work_struct *work)
 	if (!roc->started) {
 		struct ieee80211_roc_work *dep;

-		/* start this ROC */
-		ieee80211_offchannel_stop_vifs(local);
+		WARN_ON(local->use_chanctx);
+
+		/* If actually operating on the desired channel (with at least
+		 * 20 MHz channel width) don't stop all the operations but still
+		 * treat it as though the ROC operation started properly, so
+		 * other ROC operations won't interfere with this one.
+		 */
+		roc->on_channel = roc->chan == local->_oper_chandef.chan &&
+				  local->_oper_chandef.width != NL80211_CHAN_WIDTH_5 &&
+				  local->_oper_chandef.width != NL80211_CHAN_WIDTH_10;

-		/* switch channel etc */
+		/* start this ROC */
 		ieee80211_recalc_idle(local);

-		local->tmp_channel = roc->chan;
-		ieee80211_hw_config(local, 0);
+		if (!roc->on_channel) {
+			ieee80211_offchannel_stop_vifs(local);
+
+			local->tmp_channel = roc->chan;
+			ieee80211_hw_config(local, 0);
+		}

 		/* tell userspace or send frame */
 		ieee80211_handle_roc_started(roc);
@@ -380,9 +392,10 @@ void ieee80211_sw_roc_work(struct work_struct *work)
  finish:
 		list_del(&roc->list);
 		started = roc->started;
+		on_channel = roc->on_channel;
 		ieee80211_roc_notify_destroy(roc, !roc->abort);

-		if (started) {
+		if (started && !on_channel) {
 			ieee80211_flush_queues(local, NULL);

 			local->tmp_channel = NULL;
--
1.9.1