This is intended to be used with VSOCK, to notify the hypervisor/VMM, eg on the host:
qemu <...> -smbios type=11,value=io.systemd.credential:vmm.notify_socket=vsock:2:1234 -device vhost-vsock-pci,id=vhost-vsock-pci0,guest-cid=42
(vsock:2:1234 -> send to host on vsock port 1234, default is to send to 0 which is
the hypervisor itself)
Also on the host:
$ socat - VSOCK-LISTEN:1234,socktype=5
READY=1
STATUS=Ready.
-1 was used everywhere, but -EBADF or -EBADFD started being used in various
places. Let's make things consistent in the new style.
Note that there are two candidates:
EBADF 9 Bad file descriptor
EBADFD 77 File descriptor in bad state
Since we're initializating the fd, we're just assigning a value that means
"no fd yet", so it's just a bad file descriptor, and the first errno fits
better. If instead we had a valid file descriptor that became invalid because
of some operation or state change, the other errno would fit better.
In some places, initialization is dropped if unnecessary.
I changed imports of util.h to initrd-util.h, or added an import of
initrd-util.h, to keep compilation working. It turns out that many files didn't
import util.h directly.
When viewing the patch, don't be confused by git rename detection logic:
a new .c file is added and two functions moved into it.
This imports credentials also via SMBIOS' "OEM vendor string" section,
similar to the existing import logic from fw_cfg.
Functionality-wise this is very similar to the existing fw_cfg logic,
both of which are easily settable on the qemu command line.
Pros and cons of each:
SMBIOS OEM vendor strings:
- pro: fast, because memory mapped
- pro: somewhat VMM independent, at least in theory
- pro: qemu upstream sees this as the future
- pro: no additional kernel module needed
- con: strings only, thus binary data is base64 encoded
fw_cfg:
- pro: has been supported for longer in qemu
- pro: supports binary data
- con: slow, because IO port based
- con: only qemu
- con: requires qemu_fw_cfg.ko kernel module
- con: qemu upstream sees this as legacy
Let's beef up our system credential game a bit, and explicitly import
creds from sd-stub, from qemu fw_cfg and the kernel cmdline and expose
them in the same way as those passed in from nspawn.
Specifically, this will imprt such credentials to
/run/credentials/@system (if the source can be trusted, as in the
qemu/kernel cmdline case) and /run/credentials/@encrypted (otherwise,
such as sd-stub provided ones).
Once imported we'll set the $CREDENTIALS_PATH env var for PID 1, like it
would be done by a container manager for the payload. (Conversely, we'll
also creat a symlink from /run/credentials/@system to whatever is set in
$CREDENTIALS_PATH in case we are invoked by a container manager, thus
providing a fixed path where system credentials are found).
Luca Boccassi
Lennart Poettering
Zbigniew Jędrzejewski-Szmek