netdev - [PATCH] rndis_host: Flag RNDIS modems as WWAN devices

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Message-ID: <20250311091035.2523903-1-lkundrak@v3.sk>
Date: Tue, 11 Mar 2025 10:10:35 +0100
From: Lubomir Rintel <lkundrak@...sk>
To: linux-usb@...r.kernel.org
Cc: linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org,
	Paolo Abeni <pabeni@...hat.com>,
	Jakub Kicinski <kuba@...nel.org>,
	Eric Dumazet <edumazet@...gle.com>,
	"David S. Miller" <davem@...emloft.net>,
	Andrew Lunn <andrew+netdev@...n.ch>,
	Lubomir Rintel <lkundrak@...sk>
Subject: [PATCH] rndis_host: Flag RNDIS modems as WWAN devices

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@...sk>
---
 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