hostapd: Add Max Channel Switch Time element support

The Max Channel Switch Time element indicates the time delta between the
time the last beacon is transmitted by the AP in the current channel and
the expected time of the first Beacon frame transmitted by the AP in the
new channel.

IEEE P802.11be/D7.0, 35.3.11 (ML procedures for (extended) channel
switching and channel quieting) indicates that if an AP affiliated with
an AP MLD is switching channel, Max Channel Switch Time element shall be
included in every Beacon and Probe Response frame it transmits.

Add support to include the Max Channel Switch Time element in Beacon and
Probe Response frames during channel switch announcement for an AP
affiliated with an AP MLD.

Signed-off-by: Aditya Kumar Singh <quic_adisi@quicinc.com>

diff --git a/src/ap/beacon.c b/src/ap/beacon.c
index ddb99ca22313e2dca366425630baa6f62129cd41..40513154b63c9eef0fa0e3c0b7bccb663c8531d0 100644 (file)
--- a/src/ap/beacon.c
+++ b/src/ap/beacon.c
@@ -514,6 +514,35 @@ static u8 * hostapd_eid_ecsa(struct hostapd_data *hapd, u8 *eid)
 }
 
 
+static u8 * hostapd_eid_max_cs_time(struct hostapd_data *hapd, u8 *eid)
+{
+#ifdef CONFIG_IEEE80211BE
+       u32 switch_time;
+
+       /* Add Max Channel Switch Time element only if this AP is affiliated
+        * with an AP MLD and channel switch is in process. */
+       if (!hapd->conf->mld_ap || !hapd->cs_freq_params.channel)
+               return eid;
+
+       /* Switch time is basically time between CSA count 1 and CSA count
+        * 0 (1 beacon interval) + time for interface restart + time to
+        * send a Beacon frame in the new channel (1 beacon interval).
+        *
+        * TODO: Use dynamic interface restart time. For now, assume 1 sec.
+        */
+       switch_time = USEC_TO_TU(1000 * 1000) + 2 * hapd->iconf->beacon_int;
+
+       *eid++ = WLAN_EID_EXTENSION;
+       *eid++ = 4;
+       *eid++ = WLAN_EID_EXT_MAX_CHANNEL_SWITCH_TIME;
+       WPA_PUT_LE24(eid, switch_time);
+       eid += 3;
+#endif /* CONFIG_IEEE80211BE */
+
+       return eid;
+}
+
+
 static u8 * hostapd_eid_supported_op_classes(struct hostapd_data *hapd, u8 *eid)
 {
        u8 op_class, channel;
@@ -748,6 +777,10 @@ static size_t hostapd_probe_resp_elems_len(struct hostapd_data *hapd,
 
                        buflen += hostapd_eid_eht_ml_beacon_len(
                                ml_elem_ap, params->mld_info, !!params->mld_ap);
+
+                       /* For Max Channel Switch Time element during channel
+                        * switch */
+                       buflen += 6;
                }
        }
 #endif /* CONFIG_IEEE80211BE */
@@ -883,6 +916,14 @@ static u8 * hostapd_probe_resp_fill_elems(struct hostapd_data *hapd,
                pos = hostapd_eid_rnr(hapd, pos, WLAN_FC_STYPE_PROBE_RESP,
                                      true);
        pos = hostapd_eid_fils_indic(hapd, pos, 0);
+
+       /*
+        * Max Channel Switch Time element
+        * TODO: This should be included inside the ML STA profile.
+        */
+       if (!params->is_ml_sta_info)
+               pos = hostapd_eid_max_cs_time(hapd, pos);
+
        pos = hostapd_get_rsnxe(hapd, pos, epos - pos);
 
 #ifdef CONFIG_IEEE80211AX
@@ -2227,8 +2268,13 @@ int ieee802_11_build_ap_params(struct hostapd_data *hapd,
                 * long based on the common info and number of per
                 * station profiles. For now use 256.
                 */
-               if (hapd->conf->mld_ap)
+               if (hapd->conf->mld_ap) {
                        tail_len += 256;
+
+                       /* for Max Channel Switch Time element during channel
+                        * switch */
+                       tail_len += 6;
+               }
        }
 #endif /* CONFIG_IEEE80211BE */
 
@@ -2376,6 +2422,10 @@ int ieee802_11_build_ap_params(struct hostapd_data *hapd,
 
        tailpos = hostapd_eid_rnr(hapd, tailpos, WLAN_FC_STYPE_BEACON, true);
        tailpos = hostapd_eid_fils_indic(hapd, tailpos, 0);
+
+       /* Max Channel Switch Time element */
+       tailpos = hostapd_eid_max_cs_time(hapd, tailpos);
+
        tailpos = hostapd_get_rsnxe(hapd, tailpos, tailend - tailpos);
        tailpos = hostapd_eid_mbssid_config(hapd, tailpos,
                                            params->mbssid_elem_count);

diff --git a/src/common/ieee802_11_defs.h b/src/common/ieee802_11_defs.h
index db9e90355d3ef6465c1c446cf93e6b1e833a040c..7f88fca06e3227cea59cacc430ede1de0bd35385 100644 (file)
--- a/src/common/ieee802_11_defs.h
+++ b/src/common/ieee802_11_defs.h
@@ -504,6 +504,7 @@
 #define WLAN_EID_EXT_HE_MU_EDCA_PARAMS 38
 #define WLAN_EID_EXT_SPATIAL_REUSE 39
 #define WLAN_EID_EXT_COLOR_CHANGE_ANNOUNCEMENT 42
+#define WLAN_EID_EXT_MAX_CHANNEL_SWITCH_TIME 52
 #define WLAN_EID_EXT_OCV_OCI 54
 #define WLAN_EID_EXT_MULTIPLE_BSSID_CONFIGURATION 55
 #define WLAN_EID_EXT_NON_INHERITANCE 56