This reverts commit 456ff9f8d5.
That patch just disabled the smartcard channel completely because
the check was done *before* the initialization of the qemu smartcard
devices, not after.
According to spice.proto the smartcard channel can receive acks and any
other message defined in BaseChannel. While the spicec implementation didn't
send an ACK spice-gtk does, so handle it.
These messages allow the guest to send the audio device volume to the
client. It uses an arbitrary scale of 16bits, which works good enough
for now.
Save VolumeState in {Playback,Record}State, so that we can send the
current volume on channel connection.
Note about future improvements:
- add exact dB support
- add client to guest volume change
Updated since v2:
- bumped record and playback interface minor version to allow
conditional compilation
Updated since v1:
- sync record volume on connection too
spice_common.h provides an ASSERT macro, no need to duplicate it
in many places. For now client/debug.h keeps its own copy since
debug.h and spice_common.h have clashes on other macros which are
trickier to unify.
With -Wpointer-arith, gcc complains about void pointer arithmetic.
This is not a big deal with gcc, but could be with other compilers,
so it's better to cast to char */uint8_t * before doing the
arithmetic on such pointers.
When using config.h, it must be the very first include in all source
files since it contains #define that may change the compilation process
(eg libc structure layout changes when it's used to enable large file
support on 32 bit x86 archs). This commit adds it at the beginning
of all .c and .cpp files
spice client and spice server shares code from
common/{gdi,gl,sw}_canvas.[ch]. However, while most of the code is
shared, the server code wants a canvas compiled with
SW_CANVAS_IMAGE_CACHE defined while the client code wants a canvas
compiled with SW_CANVAS_CACHE.
The initial autotools refactoring didn't take that into account,
this is now fixed by this commit. After this commit, the canvas
files from common/ are no longer compiled as part of the
libspice-common.la convenience library. Instead, there are "proxy"
canvas source files in client/ and server/ which #include the
appropriate C files after defining the relevant #define for the
binary that is being built.
To prevent misuse of the canvas c files and headers in common/,
SPICE_CANVAS_INTERNAL must be set when including the canvas headers
from common/ or when building the c files from common/ otherwise
the build will error out.
spice Makefile.am setup is a bit confusing, with source file
names being listed several times in different Makefile.am
(generally, once in EXTRA_DIST and another time in another
Makefile.am in _SOURCES). The client binaries are built
by client/x11/Makefile.am, which means recursing into client,
then into x11 to finally build spicec. This Makefile.am is
also referencing files from common/ and client/, which is
a bit unusual with autotools.
This patch attempts to simplify the build process to get
something more usual from an autotools point of view.
The source from common/ are compiled into a libtool convenience
library, which the server and the client links against which avoids
referencing source files from common/ when building the server and
the client. The client is built in client/Makefile.am and directly
builds files from x11/ windows/ and gui/ if needed (without
recursing in these subdirectories).
This makes the build simpler to understand, and also makes it
possible to list source files once, which avoids potential
make distcheck breakage when adding new files.
There is a regression in this patch with respect to
sw_canvas/gl_canvas/gdi_canvas. They should be built with
different preprocessor #defines resulting in different behaviour
of the canvas for the client and the server. However, this is not
currently the case, both the client and the server will use the same
code for now (which probably means one of them is broken). This will
be fixed in a subsequent commit.
make distcheck passes, but compilation on windows using the
autotools build system hasn't been tested, which means it's likely
to be broken. It shouldn't be too hard ot fix it though, just let
me know of any issues with this.
When compiling spice with make CFLAGS="-g3 -ggdb3 -O0 -Wall -Werror",
the build broken because of a few unused variables/missing returns.
This patch fixes these warnings.
The check this patch removes causes us to not set vdagent to NULL, nor
update the mouse mode when the guest agent disconnects when no client is
attached. Which leads to a non working mouse, and on agent reconnect a
"spice_server_char_device_add_interface: vdagent already attached" message
instead of a successful re-add of the agent interface .
This ensures that if the client or agent connects to the client-agent
"tunnel" while the other side is halfway through sending a multi part
message, the rest of the message gets discarded, and the connecting
party starts getting data at the beginning of the next message.
The agent message filter keeps track of messages as they are being send
reset the relevant filter to its initial state when one of the 2 ends
of the agent<->client "tunnel" disconnects.
read_from_vdi_port calls dispatch_vdi_port data, which will disconnect
the guest agent if it sends invalid data. It would then try to read more
data from the disconnected guest agent resulting in a NULL ptr dereference,
this patch fixes this.
write_to_vdi_port() was checking for reds->agent_state.connected to determine
wether it could write queued data. But agent_state.connected reflects if
*both* ends are connected. If the client has disconnected, but the guest agent
is still connected and some data is still pending (like a final clipboard
release from the client), then this data should be written to the guest agent.
We were calling reds_reset_vdp on client disconnect, which is not a good
idea. reds_reset_vdp does 3 things:
1) It resets the state related to reading chunks from the spicevmc virtio
port. If the client disconnects while the guest agent is in the middle
of sending a chunk, this will lead to an inconsistent state, and lots
of printing of "dispatch_vdi_port_data: invalid port" messages caused
by this inconsistent state sometimes followed by a segfault.
This can be triggered by copy and pasting something large (say
a screenshot) from the guest to the spice-gtk client, as the spice-gtk
client currently has a bug causing it to crash when receiving a multi
chunk vdagent messages. Without this patch (and with the spice-gtk bug
present) I can consistently reproduce this.
2) It clears any buffered writes from the client to the guest still pending
because the virtio port cannot consume data fast enough. Since the agent
itself is still running fine, throwing away writes for it because the
client has disconnected makes no sense. Esp, since on clean exit the
client may very well send a clipboard release message directly
before closing the connection, and this may get lost this way.
3) It sets client_agent_started to false, this is the only thing which
actually makes sense to do on client disconnect.
Note that since we no longer reset the vdp state on client disconnect, we
must now reset it on agent disconnect even if we don't have a client. So
the reds_reset_vdp call in reds_agent_remove() gets moved to the top,
above both the agent_state.connected and reds->peer checks which will
both fail in the no client case.
dispatch_vdi_port_data, was calling vdi_read_buf_release when no client
is connected to free the passed in buf. The only difference between
vdi_read_buf_release and directly adding the buffer back to the ring
with ring_add, is that vdi_read_buf_release calls read_from_vdi_port
after adding the buffer back. But dispatch_vdi_port_data only gets called
from read_from_vdi_port itself, thus this would lead to recursing into
read_from_vdi_port. read_from_vdi_port is protected against recursion and
will immediately return if called recursively. Thus calling
vdi_read_buf_release from dispatch_vdi_port_data is pointless, instead
simply putting the buffer back in the ring suffices.
Also bump SPICE_SERVER_VERSION to 0x000801 as 0.8.1 will be the
first version with the new API for this, and we need to be able to
detect the presence of this API in qemu.
The current assert(reds->agent_state.connected) tiggers if when
the agent disconnected there was still data waiting to be sent (for
instance if there is a bug in the client handling clipboard and it
is killed while a large clipboard transfer is in progress). So first
call to reds_agent_remove happens from spice_server_char_device_remove_interface,
and then it is called again (triggering the assert) from free_item_data
from read_from_vdi_port because of the channel destruction.
Other option would be to not call it from one of the paths - but that
is suboptimal:
* if there is no data in the pipe, the second call never happens.
* the second call has to be there anyway, because it may fail during
parsing data from the agent.
This patch fixes a segfault on this assert when a client starts passing
from guest agent to client a large clipboard and dies in the middle. There
is still another assert happening occasionally at marshaller which I don't
have a fix for (but it doesn't seem to be related).
Current master is calling red_channel_destroy() on incoming error, but
reds Channels still references it, which causes a double free() later
on (see valgrind report below).
Instead, on error condition, do like the rest of the channels and call
reds_disconnect(), which remove the references and call shutdown(),
which then call red_channel_destroy() and finally free the channel
with red_channel_destroy().
Note: the previous code intention was certainly to be able to keep the
rest of the channels connected when input channel has errors. This is
not addressed by this patch.
red_channel_shutdown:
==29792== Invalid read of size 8
==29792== at 0x4C6F063: red_channel_shutdown (red_channel.c:460)
==29792== by 0x4C51EFA: inputs_shutdown (inputs_channel.c:463)
==29792== by 0x4C48445: reds_shatdown_channels (reds.c:539)
==29792== by 0x4C4868A: reds_disconnect (reds.c:603)
==29792== by 0x4C519E9: main_channel_on_error (main_channel.c:765)
==29792== by 0x4C6E80A: red_channel_peer_on_incoming_error (red_channel.c:215)
==29792== by 0x4C6E22D: red_peer_handle_incoming (red_channel.c:87)
==29792== by 0x4C6E551: red_channel_receive (red_channel.c:154)
==29792== by 0x4C6F329: red_channel_event (red_channel.c:531)
==29792== by 0x41CB8C: main_loop_wait (vl.c:1365)
==29792== by 0x437CDE: kvm_main_loop (qemu-kvm.c:1589)
==29792== by 0x41FE9A: main (vl.c:1411)
==29792== Address 0x30b0f6d0 is 0 bytes inside a block of size 28,648 free'd
==29792== at 0x4A05372: free (vg_replace_malloc.c:366)
==29792== by 0x4C6F032: red_channel_destroy (red_channel.c:454)
==29792== by 0x4C6E80A: red_channel_peer_on_incoming_error (red_channel.c:215)
==29792== by 0x4C6E22D: red_peer_handle_incoming (red_channel.c:87)
==29792== by 0x4C6E551: red_channel_receive (red_channel.c:154)
==29792== by 0x4C6F329: red_channel_event (red_channel.c:531)
==29792== by 0x41CB8C: main_loop_wait (vl.c:1365)
==29792== by 0x437CDE: kvm_main_loop (qemu-kvm.c:1589)
==29792== by 0x41FE9A: main (vl.c:1411)
https://bugs.freedesktop.org/show_bug.cgi?id=34971
This reverts commit 5062433d8a.
red_channel_receive() can call red_channel_destroy() which frees
channel.
The condition bellow is then checked, which can access a freed
channel:
if (event & SPICE_WATCH_EVENT_WRITE || channel->send_data.blocked)
Reverting this commit solves the issue without any apparent
bugs/drawbacks, which kind of clears out the weird TODO.
handle_dev_input: cursor connect
==11826== Invalid read of size 4
==11826== at 0x4C6F83C: red_channel_event (red_channel.c:535)
==11826== by 0x41CB8C: main_loop_wait (vl.c:1365)
==11826== by 0x437CDE: kvm_main_loop (qemu-kvm.c:1589)
==11826== by 0x41FE9A: main (vl.c:1411)
==11826== Address 0x31fb00f0 is 96 bytes inside a block of size 28,648 free'd
==11826== at 0x4A05372: free (vg_replace_malloc.c:366)
==11826== by 0x4C6F536: red_channel_destroy (red_channel.c:453)
==11826== by 0x4C52B5D: inputs_channel_on_incoming_error (inputs_channel.c:449)
==11826== by 0x4C6ED0E: red_channel_peer_on_incoming_error (red_channel.c:215)
==11826== by 0x4C6E731: red_peer_handle_incoming (red_channel.c:87)
==11826== by 0x4C6EA55: red_channel_receive (red_channel.c:154)
==11826== by 0x4C6F82D: red_channel_event (red_channel.c:530)
==11826== by 0x41CB8C: main_loop_wait (vl.c:1365)
==11826== by 0x437CDE: kvm_main_loop (qemu-kvm.c:1589)
==11826== by 0x41FE9A: main (vl.c:1411)
==11826==
https://bugs.freedesktop.org/show_bug.cgi?id=34971
This allows later to have the callback table under RedChannel when
the callbacks actually get used by RedChannelClient. Since the cb's
are identical for different clients of the same channel it makes sense
to store the callback pointers in one place per channel. The rest of
the incoming and outgoing struct just gets moved to RedChannelClient.
Changes in display channel for a code size win.
A note about this and the previous cursor change: it will appear that we are
now (with these changes) releasing resources too early. This is not so - send
always has the option of blocking, which means after send you can not release
resources anyway, that's what the release_item callback is for. So both the
code before and now are doing the same accounting.
Use in main_channel. This is just for backward portability later
when multiple clients are introduced - needs to be considered (which
sockets do we want to export from libspiceserver?)
Introduce SpiceMarshaller param to all send's that do add_buf
Next patch will use marshaller in all functions that currently don't by
replacing red_channel_add_buf with marshaller add_ref. Note - currently
tunnel is broken due to wrong size in messages.
move all the ASSERT/PANIC/PANIC_ON/red_error/red_printf* macros
to a common file to be used with ring.h that is going to be used externally
(by spice-gtk).
Handling done in red_channel instead of per channel, using call backs
for the channel specific part.
Intended to reduce furthur reliance of channels on RedChannel struct.
The commit makes the code harder to understand because of the artificial
get_serial stuff, should later be fixed by having a joint migration
header with the serial (since all channels pass it).
For ussage in the send_item callback. It's only valid during this
time anyway (should make it return NULL in other occasions?)
No more direct usage of RedChannel.send_data.marshaller by channels.
The renames are part of refactoring red_worker's RedChannel to reuse
red_channel.h's RedChannel at the end.
s/red_send_data/red_channel_send/
s/red_pipe_get/red_channel_pipe_get/
s/recive_data/incoming/
s/red_receive/red_channel_receive/
s/channel_handle_message/red_channel_handle_message/
s/channel_is_connected/red_channel_is_connected/
s/red_pipe_add_type/red_channel_pipe_add_type/
We introduce 2 public functions to integrate with the library user.
spice_server_set_sasl() - turn on SASL
spice_server_set_sasl_appname() - specify the name of the app (It is
used for where to find the default configuration file)
The patch for QEMU is on its way.
https://bugs.freedesktop.org/show_bug.cgi?id=34795
Try to have a common base dispose() method for channels. For now, it
just free the caps.
Make use of it in snd_worker, and in sync_write() - sync_write() is
going to have default caps later on.
https://bugs.freedesktop.org/show_bug.cgi?id=34795
This is stylish change again. We are talking about a RedStream object,
so let's just name the variable "stream" everywhere, to avoid
confusion with a non existent RedPeer object.
https://bugs.freedesktop.org/show_bug.cgi?id=34795
This patch make it easier to spot warnings in compilation. It should
work with older versions of automake that don't support silent rules.
If you want verbose build, make V=1.
Signed-off-by: Uri Lublin <uril@redhat.com>
https://bugs.freedesktop.org/show_bug.cgi?id=34795
s/disconnect_channel_proc/channel_disconnect_proc/
s/release_item_proc/channel_release_pipe_item_proc/
s/handle_message_proc/channel_handle_parsed_proc/
Adds RedChannel* channel as first parameter to hold_pipe_item_proc
with everything (almost) not in red_channel's RedChannel
As a result of CommonChannel a free cb is added to EventHandler,
to take care of non zero offset for embedded EventHandler.
The device already sends one. There are actually two connections going
on:
server to client - this is the smartcard channel, it reuses the VSC protocol.
server to device - this is an internal connection using VSC too.
We generally just passthrough all messages from the client to the device,
and from the device to the client. We only rewrite the reader_id because
the device knows about a single id (it is actually a card id), and we
may manage more then one in the future.
Bottom line is that there was an extra VSC_Error message reaching the client.
try to push either on signal (write available) or when blocked
and read signaled. From red_worker, copied for compatibility when
switching later to RedChannel in red_worker. Doesn't make a lot of
sense (but works), see comment in patch.
MAX_SEND_VEC was 100 for DisplayChannel's RedChannel implementation which is being replaced
with RedChannel in red_channel. So changing from 50 to 100 in red_channel
(make this configurble?) - effectively increased memory usage by:
(100-50)*sizeof(iovec)*(num_of_channels-2) ==(arch 64bit) 50*16*6 ~ 5k
Not terrible.
hold_item called on init_send_data, matching release.
This is not the behavior of red_worker - we ref++ (==hold_item) when
sending the item, and --refs when releasing it, instead of only holding
if the send is blocked.
Note 1: Naming: hold_pipe_item is the proc name, the variable is called
hold_item, this is similar to release_item/release_pipe_item naming.
Note 2: All channels have empty implementation, we later use this when
red_worker get's RedChannelized.
While we are at it: There is no reason for chardev
support to stay in the experimental area, so move it out.
qemu should not need the "spice-experimental.h" file.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
Implement server-side support for switch-host client migration. Client
side support is present already in the tree.
Setting the migration information is done using the existing
spice_server_migrate_info() function. A new
spice_server_migrate_switch() function has been added which triggers
sending out the switch-host message.
Seamless migration functions are left there for now.
spice_server_migrate_start() has been chamnged to just fail
unconditionally though as seamless migration is broken anyway.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
drawable_count was becoming negative. It tracks the number of
items in the worker->current_list ring. It was decremented correctly,
but incremented only in several cases. The cases it wasn't incremented
where:
red_current_add_equal found an equivalent drawable
by moving the increment to where the item is added to current_list, in
__current_add_drawable, the accounting remains correct.
This has no affect other then correct accounting, as drawable_count isn't
used for anything.
We should pass up errors instead of aborting. Do that at least
for bind() failures which actually happen in real live due to the
tcp port being busy.
Signed-off-by: Gerd Hoffmann <kraxel@redhat.com>
We erronously ignored data from guest on the serial channel if no client is
connected. This leads to an assert when the guest writes a second time, since
there is still data unconsumed by us (the host).
Fix by reading data anyway, and discarding it after parsing (and reading) whole
messages from the guest.
Net affect is that any messages the agent sends while no client is connected
get discarded, but only full messages are discarded.
This fixes an abort if booting a winxp guest with vdagent without a connected
client.
updates taken from spice vga mode updates, i.e. non cacheable, glz compressed
(depends on whatever settings you apply to the server) opaque draw operations.
+ completed the SpiceCoreInterface implementation (timers)
v1->v2:
removed test_util.c (Hans)
replaced mallocz with calloc (Hans)
We are keeping track of tokens for sending agent data to the client, but
the client send an initial value of ~0, and never gives us new send tokens
so this is all rather useless -> remove it.
Note that it is kept in the migration data struct for compatibility reasons.
read_from_vdi_port(), called from vdagent_char_device_wakeup() may
fail to consume all data because no buffers are available in the
read_bufs ring. When this happens we would fail to ever read more data
from the agent on the guest as the port is throttled and stays throttled
until we've consumed all data from the current buffer.
This patch re-enables the call to read_from_vdi_port() from
vdi_read_buf_release(), so that we will try the read again when space
becomes available in the read_bufs ring.
Together with another nasty hack in the linux guest virtio_console
driver, where it waits for a write to be acked by the host before
continuing with the next one, this can lead to a linux guest
getting stuck / hang (until the write is read by the spice-server
which never happens becaus of the above issues).
Note that even with this patch, the guest will still gets stuck due to
a bug in watch_update_mask in spice-core in qemu, which causes writing
to the client to never resume once it blocked. A patch for this has been
submitted to qemu.
read_from_vdi_port() MUST always be called in a while loop until it returns 0.
This is needed because it can cause new data available events and its
recursion protection causes those to get lost. Calling it until it returns 0
ensures that all data has been consumed.
Example scenario where we can fail to read the available data otherwise:
- server/reds.c: vdagent_char_device_wakeup get called
by hw/spice-vmc.c because data has arrived from the guest,
- hw/spice-vmc.c: vmc_read get calls
- If the vmc_read call depletes the current buffer it calls
virtio_serial_throttle_port(&svc->port, false)
- This causes vmc_have_data to get called, which if in the
mean time another buffer has arrived causes
vdagent_char_device_wakeup to gets called again
(so recursively)
- vdagent_char_device_wakeup is protected against recursive
calling and ignores the second call (a nasty hack)
- if no other data arrives, the arrived data will not get read
This patch adds a channel event callback to the spice core interface.
This new callback will be called for three events:
(1) A new connection has been established.
(2) The channel is ready (i.e. authentication is done,
link message verification passed all tests, channel
is ready to use).
(3) Channel was disconnected.
Qemu will use this to send notifications to the management app.
When drawing a drawable with a NULL src bitmap that means we should
be using the previously generated self_bitmap. Not doing this causes
a segfault due to accessing the NULL.
The self_bitmap is the size of self_bitmap_area, not the bbox.
This is especially important since we later copy the self_bitmap_area
into the new bitmap, and if that is larger than bbox then we will
overwrite random memory.
We really need to flush the ring to ensure that we push something on the
release ring. If we don't do this and the ring is not pushed for other
reasons we will timeout in the guest driver waiting for the ring.
We've changed how resources are released so they are now being
freed continuosly, rather than on OOM, since we want to free as early
possible to avoid fragmentation. So, OOM situations should be a bit
less common now and signify a real memory shortage, so we should try
to free up more resources.
When upgrading a cluster of machines you typically do this by
upgrading a set of machines at a time, making the new machines run
the new software version, but in a fashion compatible with the old
versions (in terms of e.g. migration). Then when all machines are
upgrades, any new features in the new version can be enabled.
This API allows qemu to limit the set of features that spice uses to
those compatible with an older version, in order to do an upgrade like
this. Right now it doesn't really do much, since we don't keep compat
with 0.4.0 atm (although that may be added later).
There is no guarantee that any future version of spice support
being compatible with any previous version. However, we will always
support compatibility with the previous major version so that clusters
can be upgraded step by step.
This will prevent: 1) rendering problems (commands sent to the client in the wrong order)
2) sending commands for surfaces that haven't been created yet on the client side.
This used to be a callback for the vdi_port "data ready" interrupt,
which did indicate either data ready to read or data ready to write, but
this is no longer the case now that virtio-serial is used.
This seemingly simple fix prevents a race that needs to be fixed with
another patch, see freedesktop bz #29903
The vdi_port_write_timer_started flag was not being reset, which prevented
another vdi_port_write_timer_start from actually starting the timer. Fix
is to change order of lines. This happens in the callback of the timer, so
no chance of double timer set.
A side effect of the previous red_current_flush, which flushed all the surfaces, and was called on a new display channel connection, was
that red_handle_drawable_surfaces_client_synced sent the most updated surfaces images when needed. However, now, it should
explicitly call red_current_flush.
Moreover, since red_current_flush was called on a new display channel connection only if there was a primary surface,
if the connection of the display channel occurred at the moment of no primary surface, red_handle_drawable_surfaces_client_synced was buggy.
Update #define in server/spice.h in preparation for the 0.6.0 release.
We also got some new functions, thus we have to increate the shared
lib minor number for spice-server.
The actual bitmap data was added to the main marshaller rather than
the submarshaller that pointed to the SpiceImage part. This made us
send too short messages failing demarshalling in the client.
When the we reset qxl, we destroy all srufaces. Since surfaces and glz
drawables are no longer dependent, we need to call red_display_clear_glz_drawables explicitly
in order to clear all our drawables references in the server.
Remove all uses of @end in the marshaller, instead just using
the C struct array-at-end-of-struct. To make this work we also remove
all use of @end for switches (making them C unions).
We drop the zero member of the notify message so that we can avoid this
use of @end for a primitive in the marshaller (plus its useless to send
over the wire).
We change the offsets and stuff in the migration messages to real pointers.
There is no need to check the pci ids or revisions. Thats a contract
between qemu and the driver, and spice need not care, as long as
we get the right data from qemu.
I still don't have commit access (can't ssh to anarchy) so if someone could commit this (alex) thanks,
Alon
Fix for no opengl patch - required to compile the server (fixes missing symbol gl_canvas_init).
Internally and in the network protocol (for the new version) we
now store the actual number of segments rather than the size of the
full segments array in bytes. This change consists of multiple changes
to handle this:
* Make the qxl parser calculate num_segments
* Make the canvas stroke code handle the new SpicePath layout.
* Fix up is_equal_path in red_worker.c for the new layout
* replace multiple calls to spice_marshall_PathSegment with a single
spice_marshall_Path call
* Make the byte_size() array size handling do the conversion from
network size to number of elements when marshalling/demarshalling.
* Update the current spice protocol to send the segment count rather than
the size
* Update the old spice protocol to use the new byte_size functionallity
to calculate the size sent and the number of elements recieved
red_parse_qxl.c starts to follow QXLPHYSICAL references and build up
data structures. Can zap a bunch of get_virt calls in red_worker.c,
followed by cleanups.
(de-) marshaller needs updates to deal with that. Also I suspect with
the get_virt() calls being gone we can offload more work to generated
marshaller code.
client doesn't build.
when SPICE_MSG_DISPLAY_RESET was sent, SPICE_MSG_DISPLAY_SURFACE_DESTROY had already
been sent for all surfaces.
It also caused a client crash since DisplayChannel::handle_reset assumes that screen
exists.
This is required because we don't want to free messages that just
refer to the unparsed message (like SpiceMsgData).
Also, in the future we might need it for more complex demarshalling.
We move all message structs from spice-protocol to spice as
we want to be able to change these as needed internally. The
on-network format is no longer defined by these structures anyway,
but rather by the spice protocol description.
