Sometimes udev or some other background daemon might keep the loopback
devices busy while we already want to detach them. Downgrade the warning
about it.
Given that we use autodetach downgrading these messages should be with
little risk.
With this change nspawn's -i switch now can now make sense of MBR disk
images too - however only if there's only a single, bootable partition
of type 0x83 on the image. For all other cases we cannot really make
sense from the partition table alone.
The big benefit of this change is that upstream Fedora Cloud Images can
now be booted unmodified with systemd-nspawn:
# wget http://download.fedoraproject.org/pub/fedora/linux/releases/21/Cloud/Images/x86_64/Fedora-Cloud-Base-20141203-21.x86_64.raw.xz
# unxz Fedora-Cloud-Base-20141203-21.x86_64.raw.xz
# systemd-nspawn -i Fedora-Cloud-Base-20141203-21.x86_64.raw -b
Next stop: teach the import logic to automatically download these
images, uncompress and verify them.
This is useful for nspawn managers that want to learn when nspawn is
finished with initialiuzation, as well what the PID of the init system
in the container is.
This adds three kinds of file system locks for container images:
a) a file system lock next to the actual image, in a .lck file in the
same directory the image is located. This lock has the benefit of
usually being located on the same NFS share as the image itself, and
thus allows locking container images across NFS shares.
b) a file system lock in /run, named after st_dev and st_ino of the
root of the image. This lock has the advantage that it is unique even
if the same image is bind mounted to two different places at the same
time, as the ino/dev stays constant for them.
c) a file system lock that is only taken when a new disk image is about
to be created, that ensures that checking whether the name is already
used across the search path, and actually placing the image is not
interrupted by other code taking the name.
a + b are read-write locks. When a container is booted in read-only mode
a read lock is taken, otherwise a write lock.
Lock b is always taken after a, to avoid ABBA problems.
Lock c is mostly relevant when renaming or cloning images.
We need to turn on /proc/sys/net/ipv4/ip_forward before the
per-interface forwarding setting is useful, hence let's propagate the
per-interface setting once to the system-wide setting.
Due to the unclear ownership rules of that flag, and the fact that
turning it on also has effects on other sysctl flags we try to minimize
changes to the flag, and only turn it on once. There's no logic to
turning it off again, but this should be fairly unproblematic as the
per-interface setting defaults to off anyway.
This introduces am AddressFamilyBoolean type that works more or less
like a booleaan, but can optionally turn on/off things for ipv4 and ipv6
independently. THis also ports the DHCP field over to it.
This undoes a small part of 13790add4b
which was erroneously added, given that zero length datagrams are OK,
and hence zero length reads on a SOCK_DGRAM be no means mean EOF.
Now that networkd's IP masquerading support means that running
containers with "--network-veth" will provide network access out of the
box for the container, let's add a shortcut "-n" for it, to make it
easily accessible.
This adds two new settings to networkd's .network files:
IPForwarding=yes and IPMasquerade=yes. The former controls the
"forwarding" sysctl setting of the interface, thus controlling whether
IP forwarding shall be enabled on the specific interface. The latter
controls whether a firewall rule shall be installed that exposes traffic
coming from the interface as coming from the local host to all other
interfaces.
This also enables both options by default for container network
interfaces, thus making "systemd-nspawn --network-veth" have network
connectivity out of the box.
