net: usb: usbnet: restore usb%d name exception for local mac addresses

PATCH In review Jianlin Lv 2 participants 2 messages May 23, 2025 – May 27, 2025 1 message not in the archive

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Network drivers Stable branch USB networking drivers USB "usbnet" driver framework

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Jianlin Lv

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2025-05-23 09:37 UTC #1 lore raw

PATCH 1/1 net: usb: usbnet: restore usb%d name exception for local mac addresses

In reply to a message not in the archive

From: Dominique Martinet <[email protected]>

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/[email protected] open here

Fixes 8a7d12d674ac ("net: usb: usbnet: fix name regression")

Cc [email protected]

Tested-by Ahmed Naseef <[email protected]>

Signed-off-by Dominique Martinet <[email protected]>

Acked-by Oliver Neukum <[email protected]>

Link https://patch.msgid.link/[email protected] open here

Signed-off-by Jakub Kicinski <[email protected]>

(cherry picked from commit 2ea396448f26d0d7d66224cb56500a6789c7ed07)

Signed-off-by Jianlin Lv <[email protected]>

---
 drivers/net/usb/usbnet.c | 21 +++++++++++++++------
 1 file changed, 15 insertions(+), 6 deletions(-)

drivers/net/usb/usbnet.c +15 -6

index 9f66c47dc58b..08cbc8e4b361 100644
@@ -178,6 +178,17 @@ int usbnet_get_ethernet_addr(struct usbnet *dev, int iMACAddress)
 }
 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 +1777,11 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod)
 		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)

Signature · 1 line

2.34.1

Greg KH

maintainer

2025-05-27 14:55 UTC #2 lore raw

Quoted 29 lines · Jianlin Lv

From: Dominique Martinet <[email protected]>
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/[email protected] open here
Fixes 8a7d12d674ac ("net: usb: usbnet: fix name regression")
Cc [email protected]
Tested-by Ahmed Naseef <[email protected]>
Signed-off-by Dominique Martinet <[email protected]>
Acked-by Oliver Neukum <[email protected]>
Link https://patch.msgid.link/[email protected] open here
Signed-off-by Jakub Kicinski <[email protected]>

Quoted 3 lines

(cherry picked from commit 2ea396448f26d0d7d66224cb56500a6789c7ed07)
Signed-off-by Jianlin Lv <[email protected]>
---

What stable branch is this backport for?

confused,

greg k-h