Hi all, The patch "xen-netfront: Fix race between device setup and open" seems to have introduced a regression preventing setting MTU's larger than 1500. We experienced this downstream with Container Linux and confirmed with Fedora 28 as well.
It's commit f599c64fdf7d9c108e8717fb04bc41c680120da4 in the linux-stable tree. https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux-stable.git/commit/?id=f599c64fdf7d9c108e8717fb04bc41c680120da4 Downstream bugs: https://github.com/coreos/bugs/issues/2443 https://bugzilla.redhat.com/show_bug.cgi?id=1584216 We've confirmed that reverting that commit fixes the bug. It be reliably can be reproduced on AWS with t2.micro instances (and presumably other systems using the same driver). Both using systemd-networkd to set the mtu and manual ip link commands cause the link to repsond with "Invalid argument" when trying to set the MTU > 1500. I'm not sure why that commit introduced the regression. Please let me know if there's any more information that would be helpful. - Andrew
