The driver for AX88179 USB 3.0 to Gigabit Ethernet adapter appends a two-byte "VSS Ethernet Monitoring trailer" to every received IP packet. Issue observed on 4.15.0-76, 4.19.93, all the way up to 5.5.0-050500-generic #202001262030. The manufacturer-supplied driver from https://www.asix.com.tw/download.php?sub=driverdetail&PItemID=131 does not have this issue. This is the same issue as reported earlier here: https://bugzilla.kernel.org/show_bug.cgi?id=121141 Please let me know if I can help with more information or anything else. Kind regards, Farhad