Launching a container with a private network requires creating a
dedicated networking interface for it; name of that interface is derived
from the container name itself - e.g. a container named `foo` gets
attached to an interface named `ve-foo`.
An interface name can span up to IFNAMSIZ characters, which means that a
container name must contain at most IFNAMSIZ - 3 - 1 = 11 characters;
it's a limit that we validate using a build-time assertion.
This limit has been upgraded with Linux 5.8, as it allows for an
interface to contain a so-called altname, which can be much longer,
while remaining treated as a first-class citizen.
Since altnames have been supported natively by systemd for a while now,
due diligence on our side ends with dropping the name-assertion on newer
kernels.
This commit closes #38509.
systemd/systemd#14467systemd/systemd#17220https://lwn.net/Articles/794289/
