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Hosts hold on to handles provided by guest-file-open for periods that can
span beyond the life of the qemu-ga process that issued them. Since these
are issued starting from 0 on every restart, we run the risk of issuing
duplicate handles after restarts/reboots.
As a result, users with a stale copy of these handles may end up
reading/writing corrupted data due to their existing handles effectively
being re-assigned to an unexpected file or offset.
We unfortunately do not issue handles as strings, but as integers, so a
solution such as using UUIDs can't be implemented without introducing a
new interface.
As a workaround, we fix this by implementing a persistent key-value store
that will be used to track the value of the last handle that was issued
across restarts/reboots to avoid issuing duplicates.
The store is automatically written to the same directory we currently
set via --statedir to track fsfreeze state, and so should be applicable
for stable releases where this flag is supported.
A follow-up can use this same store for handling fsfreeze state, but
that change is cosmetic and left out for now.
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Cc: qemu-stable@nongnu.org
* fixed guest_file_handle_add() return value from uint64_t to int64_t
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To use the online disk snapshot for online-backup, application-level
consistency of the snapshot image is required. However, currently the
guest agent can provide only filesystem-level consistency, and the
snapshot may contain dirty data, for example, incomplete transactions.
This patch provides the opportunity to quiesce applications before
snapshot is taken.
If --fsfreeze-hook option is specified, the hook is executed with
"freeze" argument before the filesystem is frozen by fsfreeze-freeze
command. As for fsfreeze-thaw command, the hook is executed with "thaw"
argument after the filesystem is thawed.
This patch depends on patchset to improve error reporting by Luiz Capitulino:
http://lists.gnu.org/archive/html/qemu-devel/2012-11/msg03016.html
Signed-off-by: Tomoki Sekiyama <tomoki.sekiyama.qu@hitachi.com>
Reviewed-by: Luiz Capitulino <lcapitulino@redhat.com>
*clarified usage in help output
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
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Previously qemu-ga version was defined seperately. Since it is aligned
with QEMU releases, use QEMU_VERSION instead. This also implies the
version bump for 1.1[-rcN] release of qemu-ga.
Reviewed-by: Michal Privoznik <mprivozn@redhat.com>
Acked-by: Luiz Capitulino <lcapitulino@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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The next commit wants to use it.
Signed-off-by: Luiz Capitulino <lcapitulino@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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Currently we rely on fsfreeze/thaw commands disabling/enabling logging
then having other commands check whether logging is disabled to avoid
executing if they aren't safe for running while a filesystem is frozen.
Instead, have an explicit whitelist of fsfreeze-safe commands, and
consolidate logging and command enablement/disablement into a pair
of helper functions: ga_set_frozen()/ga_unset_frozen()
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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guest-sync leaves it as an exercise to the user as to how to reliably
obtain the response to guest-sync if the client had previously read in a
partial response (due qemu-ga previously being restarted mid-"sentence"
due to reboot, forced restart, etc).
qemu-ga handles this situation on its end by having a client precede
their guest-sync request with a 0xFF byte (invalid UTF-8), which
qemu-ga/QEMU JSON parsers will treat as a flush event. Thus we can
reliably flush the qemu-ga parser state in preparation for receiving
the guest-sync request.
guest-sync-delimited provides the same functionality for a client: when
a guest-sync-delimited is issued, qemu-ga will precede it's response
with a 0xFF byte that the client can use as an indicator to flush its
buffer/parser state in preparation for reliably receiving the
guest-sync-delimited response.
It is also useful as an optimization for clients, since, after issuing a
guest-sync-delimited, clients can safely discard all stale data read
from the channel until the 0xFF is found.
More information available on the wiki:
http://wiki.qemu.org/Features/QAPI/GuestAgent#QEMU_Guest_Agent_Protocol
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
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Many of the current RPC implementations are very much POSIX-specific
and require complete re-writes for Windows. There are however a small
set of core guest agent commands that are common to both, and other
commands such as guest-file-* which *may* be portable. So we introduce
commands.c for the latter, and will rename guest-agent-commands.c to
commands-posix.c in a future commit. Windows implementations will go in
commands-win32.c, eventually.
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This is mostly in preparation for the win32 port, which won't use
GIO channels for reasons that will be made clearer later. Here the
GAChannel class is just a loose wrapper around GIOChannel
calls/callbacks, but we also roll in the logic/configuration for
various channel types and managing unix socket connections, which makes
the abstraction much more complete and further aids in the win32 port
since isa-serial/unix-listen will not be supported initially.
There's also a bit of refactoring in the main logic to consolidate the
exit paths so we can do common cleanup for things like pid files, which
weren't always cleaned up previously.
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This adds the initial set of QMP/QAPI commands provided by the guest
agent:
guest-sync
guest-ping
guest-info
guest-shutdown
guest-file-open
guest-file-read
guest-file-write
guest-file-seek
guest-file-flush
guest-file-close
guest-fsfreeze-freeze
guest-fsfreeze-thaw
guest-fsfreeze-status
The input/output specification for these commands are documented in the
schema.
Example usage:
host:
qemu -device virtio-serial \
-chardev socket,path=/tmp/vs0.sock,server,nowait,id=qga0 \
-device virtserialport,chardev=qga0,name=org.qemu.quest_agent.0
...
echo "{'execute':'guest-info'}" | socat stdio unix-connect:/tmp/qga0.sock
guest:
qemu-ga -m virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent.0 \
-p /var/run/qemu-guest-agent.pid -d
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@gmail.com>
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This is the actual guest daemon, it listens for requests over a
virtio-serial/isa-serial/unix socket channel and routes them through
to dispatch routines, and writes the results back to the channel in
a manner similar to QMP.
A shorthand invocation:
qemu-ga -d
Is equivalent to:
qemu-ga -m virtio-serial -p /dev/virtio-ports/org.qemu.guest_agent.0 \
-f /var/run/qemu-ga.pid -d
Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@gmail.com>
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Signed-off-by: Michael Roth <mdroth@linux.vnet.ibm.com>
Signed-off-by: Luiz Capitulino <lcapitulino@gmail.com>
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