wifi: mac80211: don't set ESS capab bit in assoc request

The ESS capability bit is reserved in frames transmitted by
the client, so we shouldn't set it. Since we've set it for
decades, keep that old behaviour unless we're connection to
a new EHT AP.
Signed-off-by: Johannes Berg <johannes.berg@intel.com>
Reviewed-by: Gregory Greenman <gregory.greenman@intel.com>
Signed-off-by: Miri Korenblit <miriam.rachel.korenblit@intel.com>
Link: https://msgid.link/20231211085121.65005aba900b.I3d00c8741400572a89a7508b5ae612c968874ad7@changeidSigned-off-by: Johannes Berg <johannes.berg@intel.com>

net/mac80211/mlme.c

@@ -1385,7 +1385,7 @@ static int ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
 	struct ieee80211_mgmt *mgmt;
 	u8 *pos, qos_info, *ie_start;
 	size_t offset, noffset;
-	u16 capab = WLAN_CAPABILITY_ESS, link_capab;
+	u16 capab = 0, link_capab;
 	__le16 listen_int;
 	struct element *ext_capa = NULL;
 	enum nl80211_iftype iftype = ieee80211_vif_type_p2p(&sdata->vif);
@@ -1532,6 +1532,17 @@ static int ieee80211_send_assoc(struct ieee80211_sub_if_data *sdata)
 	*pos++ = assoc_data->ssid_len;
 	memcpy(pos, assoc_data->ssid, assoc_data->ssid_len);
 
+	/*
+	 * This bit is technically reserved, so it shouldn't matter for either
+	 * the AP or us, but it also means we shouldn't set it. However, we've
+	 * always set it in the past, and apparently some EHT APs check that
+	 * we don't set it. To avoid interoperability issues with old APs that
+	 * for some reason check it and want it to be set, set the bit for all
+	 * pre-EHT connections as we used to do.
+	 */
+	if (link->u.mgd.conn_flags & IEEE80211_CONN_DISABLE_EHT)
+		capab |= WLAN_CAPABILITY_ESS;
+
 	/* add the elements for the assoc (main) link */
 	link_capab = capab;
 	offset = ieee80211_assoc_link_elems(sdata, skb, &link_capab,