[PATCH wireless-next 1/2] Revert "wifi: mac80211: do not use old MBSSID elements"

[Aloka Dixit]

Commit a519be2f5d95 ("wifi: mac80211: do not use old MBSSID
elements") fixed the incorrect inclusion of stopped/removed
non-transmitted profiles from the Beacon frames, but it caused
a regression for channel switch (CSA) and BSS color change (CCA)
operations initiated from hostapd.

Hostapd passes two Beacon templates to kernel for CSA and CCA -
(1) beacon_csa/beacon_color_change used during the countdown.
(2) beacon_after/beacon_next used after the countdown completes.
Hostapd relies on the kernel to include the old MBSSID elements
while sending beacon_csa/beacon_color_change templates to the
driver.

This path is now broken and results in CSA/CCA failure.

Including existing MBSSID elements explicitly makes the netlink
buffer larger than default 4 KB depending on the number of APs
which would need unnecessary complication to pre-calculate the
buffer length.

Revert the commit to fix the regression.

Regarding the original issue fixed by the reverted commit -
Hostapd now has a new commit which always includes at least one
MBSSID element when the feature is enabled, hence when all
non-transmitted profiles are removed, this empty element ensures
that stopped profiles are not advertised.

Fixes: a519be2f5d95 ("wifi: mac80211: do not use old MBSSID elements")
Signed-off-by: Aloka Dixit <aloka.dixit@xxxxxxxxxxxxxxxx>
---
 net/mac80211/cfg.c | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/net/mac80211/cfg.c b/net/mac80211/cfg.c
index bd1a857c812d..b38941e6784f 100644
--- a/net/mac80211/cfg.c
+++ b/net/mac80211/cfg.c
@@ -1518,6 +1518,7 @@ ieee80211_assign_beacon(struct ieee80211_sub_if_data *sdata,
 
 	size = sizeof(*new) + new_head_len + new_tail_len;
 
+	/* new or old multiple BSSID elements? */
 	if (params->mbssid_ies) {
 		mbssid = params->mbssid_ies;
 		size += struct_size(new->mbssid_ies, elem, mbssid->cnt);
@@ -1527,6 +1528,15 @@ ieee80211_assign_beacon(struct ieee80211_sub_if_data *sdata,
 		}
 		size += ieee80211_get_mbssid_beacon_len(mbssid, rnr,
 							mbssid->cnt);
+	} else if (old && old->mbssid_ies) {
+		mbssid = old->mbssid_ies;
+		size += struct_size(new->mbssid_ies, elem, mbssid->cnt);
+		if (old && old->rnr_ies) {
+			rnr = old->rnr_ies;
+			size += struct_size(new->rnr_ies, elem, rnr->cnt);
+		}
+		size += ieee80211_get_mbssid_beacon_len(mbssid, rnr,
+							mbssid->cnt);
 	}
 
 	new = kzalloc(size, GFP_KERNEL);

-- 
2.34.1