On upgrading to sys-apps/systemd-238-r3 from sys-apps/systemd-238-r2 systemd-nspawnd on tmpfs partition with --direcotry /tmp/onelevel/directory the veth interface isn't initialized. Logs show no carrier. On ext4 partition problem dissappaears. With r2 no problem.
Can you try this patch and see if it resolves the problem? Just drop it in /etc/portage/patches/sys-apps/systemd-238-r3/ . https://github.com/systemd/systemd/pull/8633.patch
The bug has been closed via the following commit(s): https://gitweb.gentoo.org/repo/gentoo.git/commit/?id=3ffe8430672993cfc0d8d0b3abdf4d777cf3fdc1 commit 3ffe8430672993cfc0d8d0b3abdf4d777cf3fdc1 Author: Mike Gilbert <floppym@gentoo.org> AuthorDate: 2018-04-05 20:11:52 +0000 Commit: Mike Gilbert <floppym@gentoo.org> CommitDate: 2018-04-05 20:11:52 +0000 sys-apps/systemd: fix regression in nspawn network setup Closes: https://bugs.gentoo.org/652396 Package-Manager: Portage-2.3.24, Repoman-2.3.6_p81 sys-apps/systemd/files/238-nspawn-wait.patch | 83 ++++++++++++++++++++++ ...systemd-238-r3.ebuild => systemd-238-r4.ebuild} | 1 + 2 files changed, 84 insertions(+)