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mac80211: Fix race in checking AP status by sending null frame

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mac80211 tries to verify the existence of the current AP by
probing or sending a NULL frame in function
ieee80211_mgd_probe_ap_send. It 1st sends a null frame to the AP,
increments probe_send_count and waits for the ACK to the NULL
frame for a finite duration of time. At times, it happens that by
the time mac80211 gets to increment probe_send_count, the ACK for
the NULL frame transmitted has already been processed. This leads
to a race condition where mac80211 times out waiting for the ACK
for the NULL frame causing unnecessary disconnection with the AP.

Signed-off-by: Soumik Das <soumik.das@stericsson.com>
Signed-off-by: John W. Linville <linville@tuxdriver.com>
This commit is contained in:
Soumik Das 2012-05-20 15:31:13 +05:30 committed by John W. Linville
parent edb9bc9a1e
commit 992e68bf2e
1 changed files with 2 additions and 1 deletions
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3
net/mac80211/mlme.c
View file

@ -1522,6 +1522,8 @@ static void ieee80211_mgd_probe_ap_send(struct ieee80211_sub_if_data *sdata)
* anymore. The timeout will be reset if the frame is ACKed by
* the AP.
*/
ifmgd->probe_send_count++;
if (sdata->local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS) {
ifmgd->nullfunc_failed = false;
ieee80211_send_nullfunc(sdata->local, sdata, 0);
@ -1538,7 +1540,6 @@ static void ieee80211_mgd_probe_ap_send(struct ieee80211_sub_if_data *sdata)
0, (u32) -1, true, false);
}
ifmgd->probe_send_count++;
ifmgd->probe_timeout = jiffies + msecs_to_jiffies(probe_wait_ms);
run_again(ifmgd, ifmgd->probe_timeout);
if (sdata->local->hw.flags & IEEE80211_HW_REPORTS_TX_ACK_STATUS)