[PATCH v2 net-next] rndis_host: Flag RNDIS modems as WWAN devices

Lubomir Rintel
2025-03-17T15:07:56Z

Set FLAG_WWAN instead of FLAG_ETHERNET for RNDIS interfaces on Mobile
Broadband Modems, as opposed to regular Ethernet adapters.

Otherwise NetworkManager gets confused, misjudges the device type,
and wouldn't know it should connect a modem to get the device to work.
What would be the result depends on ModemManager version -- older
ModemManager would end up disconnecting a device after an unsuccessful
probe attempt (if it connected without needing to unlock a SIM), while
a newer one might spawn a separate PPP connection over a tty interface
instead, resulting in a general confusion and no end of chaos.

The only way to get this work reliably is to fix the device type
and have good enough version ModemManager (or equivalent).

Signed-off-by: Lubomir Rintel <lkundrak@v3.sk>
Fixes: 475ddf05ce2d ("rndis_host: Flag RNDIS modems as WWAN devices")

---
Changes since v1:
* Added Fixes tag, as suggested by Paolo Abeni

drivers/net/usb/rndis_host.c | 16 ++++++++++++++--
1 file changed, 14 insertions(+), 2 deletions(-)

diff --git a/drivers/net/usb/rndis_host.c b/drivers/net/usb/rndis_host.c
index 7b3739b29c8f..bb0bf1415872 100644
--- a/drivers/net/usb/rndis_host.c
+++ b/drivers/net/usb/rndis_host.c
@@ -630,6 +630,16 @@ static const struct driver_info zte_rndis_info = {
.tx_fixup = rndis_tx_fixup,
};

+static const struct driver_info wwan_rndis_info = {
+ .description = "Mobile Broadband RNDIS device",
+ .flags = FLAG_WWAN | FLAG_POINTTOPOINT | FLAG_FRAMING_RN | FLAG_NO_SETINT,
+ .bind = rndis_bind,
+ .unbind = rndis_unbind,
+ .status = rndis_status,
+ .rx_fixup = rndis_rx_fixup,
+ .tx_fixup = rndis_tx_fixup,
+};
+
/*-------------------------------------------------------------------------*/

static const struct usb_device_id products [] = {
@@ -666,9 +676,11 @@ static const struct usb_device_id products [] = {
USB_INTERFACE_INFO(USB_CLASS_WIRELESS_CONTROLLER, 1, 3),
.driver_info = (unsigned long) &rndis_info,
}, {
- /* Novatel Verizon USB730L */
+ /* Mobile Broadband Modem, seen in Novatel Verizon USB730L and
+ * Telit FN990A (RNDIS)
+ */
USB_INTERFACE_INFO(USB_CLASS_MISC, 4, 1),
- .driver_info = (unsigned long) &rndis_info,
+ .driver_info = (unsigned long)&wwan_rndis_info,
},
{ }, // END
};
--
2.48.1