Hi,

Starting from kernel version 6.7.4 I hit the following problem: when I connect two or more USB-to-ethernet adapters to the computer they get assigned the same MAC address. Furthermore, the address is not the one specified in any of the device labels but is selected seemingly at random on boot.

This becomes a blocking issue when trying to use SYSTEMD.LINK(5) to match the interfaces.

6.7.3 is OK, 6.7.4 introduces this behavior in the following upstream commit: d2689b6a86b9 net: usb: ax88179_178a: avoid two consecutive device resets Reverting this commit in 6.7.4 fixes the issue.

The behavior is also present in LTS 6.6.23. The commit has been backported in 6.6.16.

Example system log when connecting two adapters. Both interfaces are assigned address 02:a5:ab:80:e6:94.

kernel: usb 2-5.4: new SuperSpeed USB device number 3 using xhci_hcd kernel: usb 2-5.4: New USB device found, idVendor=2001, idProduct=4a00, bcdDevice= 1.00 kernel: usb 2-5.4: New USB device strings: Mfr=1, Product=2, SerialNumber=3 kernel: usb 2-5.4: Product: D-Link DUB-1312 kernel: usb 2-5.4: Manufacturer: D-Link Elec. Corp. kernel: usb 2-5.4: SerialNumber: 00000000001D4D mtp-probe[2431]: checking bus 2, device 3: "/sys/devices/pci0000:00/0000:00:14.0/usb2/2-5/2-5.4" mtp-probe[2431]: bus: 2, device: 3 was not an MTP device kernel: ax88179_178a 2-5.4:1.0 eth0: register 'ax88179_178a' at usb-0000:00:14.0-5.4, D-Link DUB-1312 USB 3.0 to Gigabit Ethernet Adapter, 02:a5:ab:80:e6:94 kernel: usbcore: registered new interface driver ax88179_178a mtp-probe[2436]: checking bus 2, device 3: "/sys/devices/pci0000:00/0000:00:14.0/usb2/2-5/2-5.4" mtp-probe[2436]: bus: 2, device: 3 was not an MTP device kernel: ax88179_178a 2-5.4:1.0 enp0s20f0u5u4: renamed from eth0 systemd-networkd[469]: eth0: Interface name change detected, renamed to enp0s20f0u5u4.

kernel: usb 1-5.3: new high-speed USB device number 8 using xhci_hcd kernel: usb 1-5.3: New USB device found, idVendor=0b95, idProduct=1790, bcdDevice= 1.00 kernel: usb 1-5.3: New USB device strings: Mfr=1, Product=2, SerialNumber=3 kernel: usb 1-5.3: Product: AX88179 kernel: usb 1-5.3: Manufacturer: ASIX Elec. Corp. kernel: usb 1-5.3: SerialNumber: 0000249B2BAEC8 kernel: ax88179_178a 1-5.3:1.0 eth0: register 'ax88179_178a' at usb-0000:00:14.0-5.3, ASIX AX88179 USB 3.0 Gigabit Ethernet, 02:a5:ab:80:e6:94 mtp-probe[2440]: checking bus 1, device 8: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.3" mtp-probe[2440]: bus: 1, device: 8 was not an MTP device kernel: ax88179_178a 1-5.3:1.0 enp0s20f0u5u3: renamed from eth0 systemd-networkd[469]: eth0: Interface name change detected, renamed to enp0s20f0u5u3. mtp-probe[2444]: checking bus 1, device 8: "/sys/devices/pci0000:00/0000:00:14.0/usb1/1-5/1-5.3" mtp-probe[2444]: bus: 1, device: 8 was not an MTP device