1 files changed, 22 insertions, 0 deletions

diff --git a/net/mac80211/mlme.c b/net/mac80211/mlme.c
index 57d5482b10fa..c415f00cd6b6 100644
--- a/net/mac80211/mlme.c
+++ b/net/mac80211/mlme.c
@@ -271,6 +271,28 @@ ieee80211_determine_chantype(struct ieee80211_sub_if_data *sdata,
         ret = 0;
 
 out:
+        /*
+         * When tracking the current AP, don't do any further checks if the
+         * new chandef is identical to the one we're currently using for the
+         * connection. This keeps us from playing ping-pong with regulatory,
+         * without it the following can happen (for example):
+         *  - connect to an AP with 80 MHz, world regdom allows 80 MHz
+         *  - AP advertises regdom US
+         *  - CRDA loads regdom US with 80 MHz prohibited (old database)
+         *  - the code below detects an unsupported channel, downgrades, and
+         *    we disconnect from the AP in the caller
+         *  - disconnect causes CRDA to reload world regdomain and the game
+         *    starts anew.
+         * (see https://bugzilla.kernel.org/show_bug.cgi?id=70881)
+         *
+         * It seems possible that there are still scenarios with CSA or real
+         * bandwidth changes where a this could happen, but those cases are
+         * less common and wouldn't completely prevent using the AP.
+         */
+        if (tracking &&
+            cfg80211_chandef_identical(chandef, &sdata->vif.bss_conf.chandef))
+                return ret;
+
         /* don't print the message below for VHT mismatch if VHT is disabled */
         if (ret & IEEE80211_STA_DISABLE_VHT)
                 vht_chandef = *chandef;