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

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

[Lubomir Rintel]

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

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

[Jakub Kicinski]

On Mon, 17 Mar 2025 16:07:37 +0100 Lubomir Rintel wrote:
> 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")

This should point to the commit you're fixing. Judging purely by the
touched lines perhaps 63ba395cd7a5 ("rndis_host: support Novatel Verizon
USB730L") ?
-- 
pw-bot: cr