From linux-netdev Tue Dec 03 13:04:55 2024 From: Dominique Martinet Date: Tue, 03 Dec 2024 13:04:55 +0000 To: linux-netdev Subject: [PATCH] net: usb: usbnet: restore usb%d name exception for local mac addresses Message-Id: <20241203130457.904325-1-asmadeus () codewreck ! org> X-MARC-Message: https://marc.info/?l=linux-netdev&m=173323431631309 From: Dominique Martinet The previous commit 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. Fixes: 8a7d12d674ac ("net: usb: usbnet: fix name regression") Signed-off-by: Dominique Martinet --- drivers/net/usb/usbnet.c | 20 ++++++++++++++------ 1 file changed, 14 insertions(+), 6 deletions(-) --- a/drivers/net/usb/usbnet.c +++ b/drivers/net/usb/usbnet.c @@ -178,6 +178,17 @@ 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; @@ -1766,13 +1777,10 @@ 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)