Hi, Oliver Neukum wrote on Thu, Oct 17, 2024 at 09:18:37AM +0200: > The fix for MAC addresses broke detection of the naming convention > because it gave network devices no random MAC before bind() > was called. This means that the check for the local assignment bit > was always negative as the address was zeroed from allocation, > instead of from overwriting the MAC with a unique hardware address. So we hit the exact inverse problem with this patch: our device ships an LTE modem which exposes a cdc-ethernet interface that had always been named usb0, and with this patch it started being named eth1, breaking too many hardcoded things expecting the name to be usb0 and making our devices unable to connect to the internet after updating the kernel. Long term we'll probably add an udev rule or something to make the name explicit in userspace and not risk this happening again, but perhaps there's a better way to keep the old behavior? (In particular this hit all stable kernels last month so I'm sure we won't be the only ones getting annoyed with this... Perhaps reverting both patches for stable branches might make sense if no better way forward is found -- I've added stable@ in cc for heads up/opinions) > +++ b/drivers/net/usb/usbnet.c > @@ -1767,7 +1767,8 @@ usbnet_probe (struct usb_interface *udev, const struct usb_device_id *prod) > // can rename the link if it knows better. > if ((dev->driver_info->flags & FLAG_ETHER) != 0 && > ((dev->driver_info->flags & FLAG_POINTTOPOINT) == 0 || > - (net->dev_addr [0] & 0x02) == 0)) > + /* somebody touched it*/ > + !is_zero_ether_addr(net->dev_addr))) ... or actually now I'm looking at it again, perhaps is the check just backwards, or am I getting this wrong? previous check was rename if (mac[0] & 0x2 == 0), which reads to me as "nobody set the 2nd bit" new check now renames if !is_zero, so renames if it was set, which is the opposite?... > strscpy(net->name, "eth%d", sizeof(net->name)); > /* WLAN devices should always be named "wlan%d" */ Thanks, -- Dominique Martinet
