[PATCH 5.4 077/154] net: usb: usbnet: restore usb%d name exception for local mac addresses

Greg Kroah-Hartman
2025-04-08T12:07:29Z

From: Dominique Martinet <dominique.martinet@atmark-techno.com>

commit 2ea396448f26d0d7d66224cb56500a6789c7ed07 upstream.

commit 8a7d12d674ac ("net: usb: usbnet: fix name regression") assumed
that local addresses always came from the kernel, but some devices hand
out local mac addresses so we ended up with point-to-point devices with
a mac set by the driver, renaming to eth%d when they used to be named
usb%d.

Userspace should not rely on device name, but for the sake of stability
restore the local mac address check portion of the naming exception:
point to point devices which either have no mac set by the driver or
have a local mac handed out by the driver will keep the usb%d name.

(some USB LTE modems are known to hand out a stable mac from the locally
administered range; that mac appears to be random (different for
mulitple devices) and can be reset with device-specific commands, so
while such devices would benefit from getting a OUI reserved, we have
to deal with these and might as well preserve the existing behavior
to avoid breaking fragile openwrt configurations and such on upgrade.)

Link: https://lkml.kernel.org/r/20241203130457.904325-1-asmadeus@codewreck.org
Fixes: 8a7d12d674ac ("net: usb: usbnet: fix name regression")
Cc: stable@vger.kernel.org
Tested-by: Ahmed Naseef <naseefkm@gmail.com>
Signed-off-by: Dominique Martinet <dominique.martinet@atmark-techno.com>
Acked-by: Oliver Neukum <oneukum@suse.com>
Link: https://patch.msgid.link/20250326-usbnet_rename-v2-1-57eb21fcff26@atmark-techno.com
Signed-off-by: Jakub Kicinski <kuba@kernel.org>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
---
drivers/net/usb/usbnet.c | 21 +++++++++++++++------
1 file changed, 15 insertions(+), 6 deletions(-)

--- a/drivers/net/usb/usbnet.c
+++ b/drivers/net/usb/usbnet.c
@@ -167,6 +167,17 @@ int usbnet_get_ethernet_addr(struct usbn
}
EXPORT_SYMBOL_GPL(usbnet_get_ethernet_addr);

+static bool usbnet_needs_usb_name_format(struct usbnet *dev, struct net_device *net)
+{
+ /* Point to point devices which don't have a real MAC address
+ * (or report a fake local one) have historically used the usb%d
+ * naming. Preserve this..
+ */
+ return (dev->driver_info->flags & FLAG_POINTTOPOINT) != 0 &&
+ (is_zero_ether_addr(net->dev_addr) ||
+ is_local_ether_addr(net->dev_addr));
+}
+
static void intr_complete (struct urb *urb)
{
struct usbnet *dev = urb->context;
@@ -1730,13 +1741,11 @@ usbnet_probe (struct usb_interface *udev
if (status < 0)
goto out1;

- // heuristic: "usb%d" for links we know are two-host,
- // else "eth%d" when there's reasonable doubt. userspace
- // can rename the link if it knows better.
+ /* heuristic: rename to "eth%d" if we are not sure this link
+ * is two-host (these links keep "usb%d")
+ */
if ((dev->driver_info->flags & FLAG_ETHER) != 0 &&
- ((dev->driver_info->flags & FLAG_POINTTOPOINT) == 0 ||
- /* somebody touched it*/
- !is_zero_ether_addr(net->dev_addr)))
+ !usbnet_needs_usb_name_format(dev, net))
strscpy(net->name, "eth%d", sizeof(net->name));
/* WLAN devices should always be named "wlan%d" */
if ((dev->driver_info->flags & FLAG_WLAN) != 0)