Trigger a 6 GHz scan if RNR contains matching short SSID

If a scan triggers a regdom update into a 6 GHz-allowed regdom, and an
RNR element in one of the legacy band scan results points to a 6 GHz
scan result with a short SSID matching the current_ssid, delay
connection in favor of a 6 GHz-only scan. This will optimize the case in
which we first connect to a 5 GHz AP, then later roam to a 6 GHz one by
directly connecting to the 6 GHz one.

Signed-off-by: Matthew Wang <matthewmwang@chromium.org>

diff --git a/wpa_supplicant/events.c b/wpa_supplicant/events.c
index 530a13edd7c52b8c6cf0cae7695a71280bb3c7ce..2858cbdd2407c34ead0b40cf654ee96e113af5ad 100644 (file)
--- a/wpa_supplicant/events.c
+++ b/wpa_supplicant/events.c
@@ -9,6 +9,7 @@
 #include "includes.h"
 
 #include "common.h"
+#include "utils/crc32.h"
 #include "eapol_supp/eapol_supp_sm.h"
 #include "rsn_supp/wpa.h"
 #include "eloop.h"
@@ -63,6 +64,8 @@ static int wpas_select_network_from_last_scan(struct wpa_supplicant *wpa_s,
                                              bool trigger_6ghz_scan,
                                              union wpa_event_data *data);
 #endif /* CONFIG_NO_SCAN_PROCESSING */
+static int wpas_trigger_6ghz_scan(struct wpa_supplicant *wpa_s,
+                                 union wpa_event_data *data);
 
 
 int wpas_temp_disabled(struct wpa_supplicant *wpa_s, struct wpa_ssid *ssid)
@@ -2397,6 +2400,52 @@ static int wpa_supplicant_need_to_roam(struct wpa_supplicant *wpa_s,
 }
 
 
+static bool wpas_short_ssid_match(struct wpa_supplicant *wpa_s,
+                                 struct wpa_scan_results *scan_res)
+{
+       size_t i;
+       struct wpa_ssid *ssid = wpa_s->current_ssid;
+       u32 current_ssid_short = ieee80211_crc32(ssid->ssid, ssid->ssid_len);
+
+       for (i = 0; i < scan_res->num; i++) {
+               struct wpa_scan_res *res = scan_res->res[i];
+               const u8 *rnr_ie, *ie_end;
+               const struct ieee80211_neighbor_ap_info *info;
+               size_t left;
+
+               rnr_ie = wpa_scan_get_ie(res, WLAN_EID_REDUCED_NEIGHBOR_REPORT);
+               if (!rnr_ie)
+                       continue;
+
+               ie_end = rnr_ie + 2 + rnr_ie[1];
+               rnr_ie += 2;
+
+               left = ie_end - rnr_ie;
+               if (left < sizeof(struct ieee80211_neighbor_ap_info))
+                       continue;
+
+               info = (const struct ieee80211_neighbor_ap_info *) rnr_ie;
+               if (info->tbtt_info_len < 11)
+                       continue; /* short SSID not included */
+               left -= sizeof(struct ieee80211_neighbor_ap_info);
+               rnr_ie += sizeof(struct ieee80211_neighbor_ap_info);
+
+               while (left >= info->tbtt_info_len && rnr_ie + 11 <= ie_end) {
+                       /* Skip TBTT offset and BSSID */
+                       u32 short_ssid = WPA_GET_LE32(rnr_ie + 1 + ETH_ALEN);
+
+                       if (short_ssid == current_ssid_short)
+                               return true;
+
+                       left -= info->tbtt_info_len;
+                       rnr_ie += info->tbtt_info_len;
+               }
+       }
+
+       return false;
+}
+
+
 /*
  * Return a negative value if no scan results could be fetched or if scan
  * results should not be shared with other virtual interfaces.
@@ -2414,6 +2463,7 @@ static int _wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
        int ret = 0;
        int ap = 0;
        bool trigger_6ghz_scan;
+       bool short_ssid_match_found = false;
 #ifndef CONFIG_NO_RANDOM_POOL
        size_t i, num;
 #endif /* CONFIG_NO_RANDOM_POOL */
@@ -2565,6 +2615,12 @@ static int _wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
            wpa_s->wpa_state < WPA_COMPLETED)
                goto scan_work_done;
 
+       if (wpa_s->current_ssid && trigger_6ghz_scan && own_request && data &&
+           wpas_short_ssid_match(wpa_s, scan_res)) {
+               wpa_dbg(wpa_s, MSG_INFO, "Short SSID match in scan results");
+               short_ssid_match_found = true;
+       }
+
        wpa_scan_results_free(scan_res);
 
        if (own_request && wpa_s->scan_work) {
@@ -2591,6 +2647,9 @@ static int _wpa_supplicant_event_scan_results(struct wpa_supplicant *wpa_s,
        if (wpa_s->supp_pbc_active && !wpas_wps_partner_link_scan_done(wpa_s))
                return ret;
 
+       if (short_ssid_match_found && wpas_trigger_6ghz_scan(wpa_s, data) > 0)
+               return 1;
+
        return wpas_select_network_from_last_scan(wpa_s, 1, own_request,
                                                  trigger_6ghz_scan, data);