wifi: fix aggressively roaming (background Wi-Fi scanning) based on seen-bssids

"wifi.seen-bssids" looks like a regular property, but it is not. Unlike
almost all other properties, it does not contain user configuration,
rather it gets filled by the daemon.

The values are thus stored in "/var/lib/NetworkManager/seen-bssids"
file, and the daemon maintains the values separately from the profile.
Only before exporting the profile on D-Bus, the value gets merged (see
NM_SETTINGS_CONNECTION_GET_PRIVATE(self)->>getsettings_cached and
nm_connection_to_dbus_full().

Hence, looking at nm_setting_wireless_get_num_seen_bssids() is not
working. Fix that.

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/issues/1253

Fixes: 0f3203338c85 ('wifi: roam aggressively if we on a multi-AP network')

https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/merge_requests/1577
(cherry picked from commit 07c6f933d1b4ba20be43bb5f5d6f977572411750)

6 files changed, 34 insertions, 11 deletions

diff --git a/src/core/devices/wifi/nm-device-wifi.c b/src/core/devices/wifi/nm-device-wifi.c
index 7b632f2792..03625f8d6d 100644
--- a/src/core/devices/wifi/nm-device-wifi.c
+++ b/src/core/devices/wifi/nm-device-wifi.c
@@ -2912,10 +2912,11 @@ supplicant_connection_timeout_cb(gpointer user_data)
 }
 
 static NMSupplicantConfig *
-build_supplicant_config(NMDeviceWifi *self,
-                        NMConnection *connection,
-                        guint32       fixed_freq,
-                        GError      **error)
+build_supplicant_config(NMDeviceWifi         *self,
+                        NMSettingsConnection *sett_conn,
+                        NMConnection         *connection,
+                        guint32               fixed_freq,
+                        GError              **error)
 {
     NMDeviceWifiPrivate          *priv   = NM_DEVICE_WIFI_GET_PRIVATE(self);
     NMSupplicantConfig           *config = NULL;
@@ -2944,7 +2945,10 @@ build_supplicant_config(NMDeviceWifi *self,
         goto error;
     }
 
-    if (!nm_supplicant_config_add_bgscan(config, connection, error)) {
+    if (!nm_supplicant_config_add_bgscan(config,
+                                         connection,
+                                         nm_settings_connection_get_num_seen_bssids(sett_conn),
+                                         error)) {
         g_prefix_error(error, "bgscan: ");
         goto error;
     }
@@ -3279,6 +3283,7 @@ act_stage2_config(NMDevice *device, NMDeviceStateReason *out_failure_reason)
     NMActRequest                       *req;
     NMWifiAP                           *ap;
     NMConnection                       *connection;
+    NMSettingsConnection               *sett_conn;
     const char                         *setting_name;
     NMSettingWireless                  *s_wireless;
     GError                             *error = NULL;
@@ -3302,6 +3307,9 @@ act_stage2_config(NMDevice *device, NMDeviceStateReason *out_failure_reason)
 
     ap_mode = nm_wifi_ap_get_mode(ap);
 
+    sett_conn = nm_act_request_get_settings_connection(req);
+    nm_assert(sett_conn);
+
     connection = nm_act_request_get_applied_connection(req);
     s_wireless = nm_connection_get_setting_wireless(connection);
     nm_assert(s_wireless);
@@ -3350,7 +3358,7 @@ act_stage2_config(NMDevice *device, NMDeviceStateReason *out_failure_reason)
         set_powersave(device);
 
     /* Build up the supplicant configuration */
-    config = build_supplicant_config(self, connection, nm_wifi_ap_get_freq(ap), &error);
+    config = build_supplicant_config(self, sett_conn, connection, nm_wifi_ap_get_freq(ap), &error);
     if (!config) {
         _LOGE(LOGD_DEVICE | LOGD_WIFI,
               "Activation: (wifi) couldn't build wireless configuration: %s",
diff --git a/src/core/settings/nm-settings-connection.c b/src/core/settings/nm-settings-connection.c
index 1638efcd7e..024c000996 100644
--- a/src/core/settings/nm-settings-connection.c
+++ b/src/core/settings/nm-settings-connection.c
@@ -2532,6 +2532,14 @@ nm_settings_connection_add_seen_bssid(NMSettingsConnection *self, const char *se
     nm_key_file_db_set_string_list(priv->kf_db_seen_bssids, connection_uuid, seen_bssids_strv, i);
 }
 
+guint
+nm_settings_connection_get_num_seen_bssids(NMSettingsConnection *self)
+{
+    g_return_val_if_fail(NM_IS_SETTINGS_CONNECTION(self), 0);
+
+    return nm_g_hash_table_size(NM_SETTINGS_CONNECTION_GET_PRIVATE(self)->seen_bssids_hash);
+}
+
 /*****************************************************************************/
 
 /**
diff --git a/src/core/settings/nm-settings-connection.h b/src/core/settings/nm-settings-connection.h
index 47599c3d6e..fce7497c4c 100644
--- a/src/core/settings/nm-settings-connection.h
+++ b/src/core/settings/nm-settings-connection.h
@@ -345,6 +345,8 @@ gboolean nm_settings_connection_has_seen_bssid(NMSettingsConnection *self, const
 
 void nm_settings_connection_add_seen_bssid(NMSettingsConnection *self, const char *seen_bssid);
 
+guint nm_settings_connection_get_num_seen_bssids(NMSettingsConnection *self);
+
 int  nm_settings_connection_autoconnect_retries_get(NMSettingsConnection *self);
 void nm_settings_connection_autoconnect_retries_set(NMSettingsConnection *self, int retries);
 void nm_settings_connection_autoconnect_retries_reset(NMSettingsConnection *self);
diff --git a/src/core/supplicant/nm-supplicant-config.c b/src/core/supplicant/nm-supplicant-config.c
index c63a00585a..1d9372e09f 100644
--- a/src/core/supplicant/nm-supplicant-config.c
+++ b/src/core/supplicant/nm-supplicant-config.c
@@ -592,7 +592,10 @@ nm_supplicant_config_add_setting_wireless(NMSupplicantConfig *self,
 }
 
 gboolean
-nm_supplicant_config_add_bgscan(NMSupplicantConfig *self, NMConnection *connection, GError **error)
+nm_supplicant_config_add_bgscan(NMSupplicantConfig *self,
+                                NMConnection       *connection,
+                                guint               num_seen_bssids,
+                                GError            **error)
 {
     NMSettingWireless         *s_wifi;
     NMSettingWirelessSecurity *s_wsec;
@@ -629,7 +632,7 @@ nm_supplicant_config_add_bgscan(NMSupplicantConfig *self, NMConnection *connecti
      * when the signal is still somewhat OK so we have an up-to-date roam
      * candidate list when the signal gets bad.
      */
-    if (nm_setting_wireless_get_num_seen_bssids(s_wifi) > 1
+    if (num_seen_bssids > 1u
         || ((s_wsec = nm_connection_get_setting_wireless_security(connection))
             && NM_IN_STRSET(nm_setting_wireless_security_get_key_mgmt(s_wsec),
                             "ieee8021x",
diff --git a/src/core/supplicant/nm-supplicant-config.h b/src/core/supplicant/nm-supplicant-config.h
index 063f7f5580..585cf9588d 100644
--- a/src/core/supplicant/nm-supplicant-config.h
+++ b/src/core/supplicant/nm-supplicant-config.h
@@ -44,8 +44,10 @@ gboolean nm_supplicant_config_add_setting_wireless(NMSupplicantConfig *self,
                                                    guint32             fixed_freq,
                                                    GError            **error);
 
-gboolean
-nm_supplicant_config_add_bgscan(NMSupplicantConfig *self, NMConnection *connection, GError **error);
+gboolean nm_supplicant_config_add_bgscan(NMSupplicantConfig *self,
+                                         NMConnection       *connection,
+                                         guint               num_seen_bssids,
+                                         GError            **error);
 
 gboolean nm_supplicant_config_add_setting_wireless_security(NMSupplicantConfig        *self,
                                                             NMSettingWirelessSecurity *setting,
diff --git a/src/core/supplicant/tests/test-supplicant-config.c b/src/core/supplicant/tests/test-supplicant-config.c
index 237b1a9671..1ca5b26e56 100644
--- a/src/core/supplicant/tests/test-supplicant-config.c
+++ b/src/core/supplicant/tests/test-supplicant-config.c
@@ -127,7 +127,7 @@ build_supplicant_config(NMConnection  *connection,
     g_assert_no_error(error);
     g_assert(success);
 
-    success = nm_supplicant_config_add_bgscan(config, connection, &error);
+    success = nm_supplicant_config_add_bgscan(config, connection, 0, &error);
     g_assert_no_error(error);
     g_assert(success);