WNM: Follow BTM procedure if the last link is dropped

If the last link is dropped, it makes sense to follow the BTM procedure.
However, in that case we need to prevent reconnection to this link
specifically, while if the AP MLD is terminating we need to forbid
connecting to the AP MLD.

As such, add a new variable to track the BSSID or AP MLD MAC address.
Which one it refers to depends on whether wnm_link_removal is set.

This also simplifies the check in wnm_is_bss_excluded() and untangles it
from wpa_s->current_bss.

Signed-off-by: Benjamin Berg <benjamin.berg@intel.com>

wpa_supplicant/wnm_sta.c

@@ -1071,7 +1071,7 @@ static int wnm_send_bss_transition_mgmt_resp(
 		wpabuf_put_data(buf, "\0\0\0\0\0\0", ETH_ALEN);
 	}
 
-	if (status == WNM_BSS_TM_ACCEPT && !wpa_s->wnm_link_removal)
+	if (status == WNM_BSS_TM_ACCEPT && target_bssid)
 		wnm_add_cand_list(wpa_s, &buf);
 
 #ifdef CONFIG_MBO
@@ -1467,15 +1467,34 @@ static void ieee802_11_rx_bss_trans_mgmt_req(struct wpa_supplicant *wpa_s,
 	 * set to 1, and the BSS Termination Included field is set to 1, only
 	 * one of the links is removed and the other links remain associated.
 	 * Ignore the Disassociation Imminent field in such a case.
+	 *
+	 * TODO: We should check if the AP has more than one link.
+	 * TODO: We should pass the RX link and use that
 	 */
-	if (disassoc_imminent &&
+	if (disassoc_imminent && wpa_s->valid_links &&
-	    (wpa_s->valid_links & (wpa_s->valid_links - 1)) != 0 &&
 	    (wpa_s->wnm_mode & WNM_BSS_TM_REQ_LINK_REMOVAL_IMMINENT) &&
 	    (wpa_s->wnm_mode & WNM_BSS_TM_REQ_BSS_TERMINATION_INCLUDED)) {
+		/* If we still have a link, then just accept the request */
+		if (wpa_s->valid_links & (wpa_s->valid_links - 1)) {
 			wpa_printf(MSG_INFO,
 				   "WNM: BTM request for a single MLO link - ignore disassociation imminent since other links remain associated");
 			disassoc_imminent = false;
+
+			wnm_send_bss_transition_mgmt_resp(
+				wpa_s, WNM_BSS_TM_ACCEPT, 0, 0, NULL);
+
+			return;
+		}
+
+		/* The last link is being removed (which must be the assoc link)
+		 */
 		wpa_s->wnm_link_removal = true;
+		os_memcpy(wpa_s->wnm_dissoc_addr,
+			  wpa_s->links[wpa_s->mlo_assoc_link_id].bssid,
+			  ETH_ALEN);
+	} else {
+		os_memcpy(wpa_s->wnm_dissoc_addr, wpa_s->valid_links ?
+			  wpa_s->ap_mld_addr : wpa_s->bssid, ETH_ALEN);
 	}
 
 	if (disassoc_imminent) {
@@ -2034,8 +2053,6 @@ void wnm_clear_coloc_intf_reporting(struct wpa_supplicant *wpa_s)
 
 bool wnm_is_bss_excluded(struct wpa_supplicant *wpa_s, struct wpa_bss *bss)
 {
-	unsigned int i;
-
 	if (!(wpa_s->wnm_mode & WNM_BSS_TM_REQ_DISASSOC_IMMINENT))
 		return false;
 
@@ -2043,24 +2060,15 @@ bool wnm_is_bss_excluded(struct wpa_supplicant *wpa_s, struct wpa_bss *bss)
 	 * In case disassociation imminent is set, do no try to use a BSS to
 	 * which we are connected.
 	 */
-
+	if (wpa_s->wnm_link_removal ||
-	if (wpa_s->current_bss &&
+	    !(wpa_s->drv_flags2 & WPA_DRIVER_FLAGS2_MLO) ||
-	    ether_addr_equal(wpa_s->current_bss->bssid, bss->bssid)) {
+	    is_zero_ether_addr(bss->mld_addr)) {
-		wpa_dbg(wpa_s, MSG_DEBUG,
+		if (ether_addr_equal(bss->bssid, wpa_s->wnm_dissoc_addr))
-			"WNM: Disassociation imminent: current BSS");
 			return true;
-	}
+	} else {
-
+		if (ether_addr_equal(bss->mld_addr, wpa_s->wnm_dissoc_addr))
-	if (!wpa_s->valid_links)
-		return false;
-
-	for_each_link(wpa_s->valid_links, i) {
-		if (ether_addr_equal(wpa_s->links[i].bssid, bss->bssid)) {
-			wpa_dbg(wpa_s, MSG_DEBUG,
-				"WNM: MLD: Disassociation imminent: current link");
 			return true;
 	}
-	}
 
 	return false;
 }

wpa_supplicant/wpa_supplicant_i.h

@@ -1305,6 +1305,7 @@ struct wpa_supplicant {
 	u8 wnm_num_neighbor_report;
 	u8 wnm_mode;
 	bool wnm_link_removal;
+	u8 wnm_dissoc_addr[ETH_ALEN];
 	u16 wnm_dissoc_timer;
 	u8 wnm_bss_termination_duration[12];
 	struct neighbor_report *wnm_neighbor_report_elements;