On Mon, Oct 03, 2022 at 09:04:47PM +0000, Charles Lohr wrote: > Thank you for the prompt and clear reply. > > Will BSSID locking interfere with explicit (controller-based) handoff for > mesh networks? (Not regular roaming where the station would be responsible > for selecting a new ap)
BSSID locking is relevant only when the interface is connected to a network through NetworkManager. If the connection profile sets AP or ad-hoc mode, BSSID locking is not necessary because background scanning is already disabled. For other modes (infrastructure and mesh), it's necessary to set the BSSID to avoid scanning: https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/1.40.0/src/core/supplicant/nm-supplicant-config.c#L585-614 When the interface is not connected to a network via NM, the only way to disable periodic scanning is to set the interface as unmanaged by NetworkManager. See also: https://mail.gnome.org/archives/networkmanager-list/2022-June/msg00005.html https://mail.gnome.org/archives/networkmanager-list/2022-July/msg00001.html > The lockout during our application running won't work for us because there > are some processes running as root. But this isn't crucial. Polkit rules are quite flexible and probably there is a way to achieve what you want. https://www.freedesktop.org/software/polkit/docs/latest/polkit.8.html Beniamino > -----Original Message----- > From: Beniamino Galvani <bgalv...@redhat.com> > Sent: Monday, October 3, 2022 1:13 AM > To: Charles Lohr <charl...@valvesoftware.com> > Cc: 'networkmanager-list@gnome.org' <networkmanager-list@gnome.org> > Subject: Re: Preventing network scans once connected via libnm > > On Sat, Oct 01, 2022 at 12:46:24AM +0000, Charles Lohr via > networkmanager-list wrote: > > In our application, we need to maintain connection to an AP and it needs to > > stay low latency for a variety of reasons. Whenever networks are scanned, > > for us they create an unacceptable level of latency (>50ms in many cases) > > on the connection. > > > > Sometimes we stop NetworkManager from running with `pkill -STOP > > NetworkManager` and `pkill -CONT NetworkManager` but, for a variety of > > reasons this is disadvantageous. > > > > I've seen references to people online saying you can prevent scanning once > > connected by specifying a BSSID, but I don't see how that can be done with > > libnm. > > > > Currently we use the following, where path can be gotten from either a > > scan or `nm_connection_get_path` > > > > ``` > > nm_client_activate_connection_async ( m_pClient, conn, > > (NMDevice*)m_pDevice, sAccessPointPath.c_str(), nullptr, []( GObject* > > pObj, GAsyncResult* res, gpointer pContext ) {...} ); ``` > > > > What mechanism can we use to specify that a given path should lock it's > > BSSID when using NetworkManager via libnm? > > Hi, > > to disable scanning, you can set the property NM_SETTING_WIRELESS_BSSID of > the setting NMSettingWireless to the AP's BSSID when the connection profile > is created. To get the AP's BSSID use nm_access_point_get_bssid(). > > References: > https://gitlab.freedesktop.org/NetworkManager/NetworkManager/-/blob/1.40.0/examples/C/glib/add-connection-libnm.c#L44 > https://networkmanager.dev/docs/api/latest/nm-settings-dbus.html#id-1.2.9.4.48 > ("bssid property") > https://networkmanager.dev/docs/libnm/latest/NMAccessPoint.html#nm-access-point-get-bssid > https://fedoramagazine.org/using-python-and-networkmanager-to-control-the-network/ > > > Second question: Are there any mechanisms we can use to lock out other > > apps from requesting scans from NetworkManager? This solution would be > > preferred for our application because scans have such a significant impact > > on the system. Or is there a way to just outright disable all scanning via > > NetworkManger for a period of time? > > If the feature is enabled at build time, NM can use polkit to authorize D-Bus > requests. In particular, there is a "Wi-Fi scan" > permission that grants access to scans. I think you can use polkit rules to > restrict the access to a certain user or process; however, note that any > process running as root bypasses polkit checks and is always authorized. > > References: > https://networkmanager.dev/docs/libnm/latest/libnm-nm-dbus-interface.html#NMClientPermission > https://networkmanager.dev/docs/api/latest/nmcli.html (nmcli general > permissions) > > Beniamino >
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