From: Yuvarani V <quic_yuvarani@quicinc.com>
Date: Mon, 23 Sep 2024 14:27:27 +0000 (+0530)
Subject: AP MLD: Fix max number of simultaneous links in MLE during CAC
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=c0e8b16a3841007d720944b4461f878aef5c3ca8;p=thirdparty%2Fhostap.git

AP MLD: Fix max number of simultaneous links in MLE during CAC

The Maximum Number Of Simultaneous Links field in MLD Capabilities And
Operations subfield in MLE is currently advertised as `num_links - 1`,
where `num_links` is the number of links added to the AP MLD. However,
when the 5 GHz band link is waiting for CAC timeout, this results in an
incorrect value being advertised for the maximum number of simultaneous
links in MLE, as the 5 GHz link is not active.

For example, an AP MLD with 3 links (2.4 GHz, 5 GHz (waiting for CAC
timeout), and 6 GHz) during bringup has `num_links` set to 3.
Consequently, the maximum number of simultaneous links in MLE is
advertised as 2 according to the current code, despite the 5 GHz link
being in CAC timeout. The field should have been set to 1 to indicate
maximum of 2 links.

Fix this issue by determining the number of currently active links of
the AP MLD (instead of hapd->num_links which may include currently
inactive links) and use it to set the value for the maximum number of
simultaneous links in MLE.

Signed-off-by: Yuvarani V <quic_yuvarani@quicinc.com>
---

diff --git a/src/ap/hostapd.c b/src/ap/hostapd.c
index 1ce80d066..c6d3c315a 100644
--- a/src/ap/hostapd.c
+++ b/src/ap/hostapd.c
@@ -5061,6 +5061,28 @@ void hostapd_mld_interface_freed(struct hostapd_data *hapd)
 		link_bss->drv_priv = NULL;
 }
 
+
+/* Return the number of currently active links, not counting the calling link
+ * (i.e., a value that is suitable to be used as-is in fields that use encoding
+ * of the value minus 1). */
+u8 hostapd_get_active_links(struct hostapd_data *hapd)
+{
+	struct hostapd_data *link_bss;
+	u8 active_links = 0;
+
+	if (!hapd || !hapd->conf->mld_ap)
+		return 0;
+
+	for_each_mld_link(link_bss, hapd) {
+		if (link_bss == hapd || !link_bss->started)
+			continue;
+
+		active_links++;
+	}
+
+	return active_links;
+}
+
 #endif /* CONFIG_IEEE80211BE */
 
 
diff --git a/src/ap/hostapd.h b/src/ap/hostapd.h
index 7e72863af..0862d5dfd 100644
--- a/src/ap/hostapd.h
+++ b/src/ap/hostapd.h
@@ -857,6 +857,7 @@ bool hostapd_is_ml_partner(struct hostapd_data *hapd1,
 u8 hostapd_get_mld_id(struct hostapd_data *hapd);
 int hostapd_mld_add_link(struct hostapd_data *hapd);
 int hostapd_mld_remove_link(struct hostapd_data *hapd);
+u8 hostapd_get_active_links(struct hostapd_data *hapd);
 struct hostapd_data * hostapd_mld_get_first_bss(struct hostapd_data *hapd);
 
 void free_beacon_data(struct beacon_data *beacon);
diff --git a/src/ap/ieee802_11_eht.c b/src/ap/ieee802_11_eht.c
index 89f8ffde9..47526a836 100644
--- a/src/ap/ieee802_11_eht.c
+++ b/src/ap/ieee802_11_eht.c
@@ -503,7 +503,7 @@ static u8 * hostapd_eid_eht_basic_ml_common(struct hostapd_data *hapd,
 
 	mld_cap = hapd->iface->mld_mld_capa;
 	max_simul_links = mld_cap & EHT_ML_MLD_CAPA_MAX_NUM_SIM_LINKS_MASK;
-	active_links = hapd->mld->num_links - 1;
+	active_links = hostapd_get_active_links(hapd);
 
 	if (active_links > max_simul_links) {
 		wpa_printf(MSG_ERROR,