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Currently when the main channel disconnects while a spicevmc channel
(such as a usbredir channel) is still connected, qemu will abort with the
following message:
ring_remove: ASSERT item->next != NULL && item->prev != NULL failed
This is caused by red_client_destroy() first calling:
rcc->channel->client_cbs.disconnect(rcc);
And then calling:
red_channel_client_destroy(rcc);
For each channel. This is fine, but the spicevmc disconnect code does a
red_channel_client_destroy(rcc) itself since as usb devices are added
/ removed, the channels carrying their traffic get connected / disconnected
and they get re-used for new devices, which won't work if the old channel is
still there when the new connection comes in.
This patch fixes the double destroy when there are still spicevmc channels
connected by not doing the red_channel_client_destroy from the spicevmc
disconnect code when not just the channel, but the entire client is
disconnecting.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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While discussing various things with Alon in Vancouver, it came up that
having a channel which simply passes through data coming out of a qemu
chardev frontend unmodified, like the usbredir channel does, can be used
for a lot of other cases too. To facilitate this the usbredir channel code
will be turned into a generic spicevmc channel, which is just a passthrough
to the client, from the spicevmc chardev.
This patch renames usbredir.c to spicevmc.c and changes the prefix of all
functions / structs to match. This should make clear that the code is not
usbredir specific.
Some examples of why having a generic spicevmc pass through is good:
1) We could add a monitor channel, allowing access to the qemu monitor from
the spice client, since the monitor is a chardev frontend we could re-use
the generic spicevmc channel server code, so all that is needed to add this
(server side) would be reserving a new channel id for this.
2) We could allow users to come up with new channels of their own, without
requiring qemu or server modification. The idea is to allow doing something
like this on the qemu startup cmdline:
-chardev spicevmc,name=generic,channelid=128
To ensure these new "generic" channels cannot conflict with newly added
official types, they must start at the SPICE_CHANNEL_USER_DEFINED_START value
(128).
These new user defined channels could then either be used with a special
modified client, with client plugins (if we add support for those), or
by exporting them on the client side for use by an external ap, see below.
3) We could also add support to the client to make user-defined channels
end in a unix socket / pipe, allowing handling of the data by an external app,
we could for example have a new spice client cmdline argument like this:
--custom-channel unixsocket=/tmp/mysocket,channelid=128
This would allow for something like:
$random app on guest -> virtio-serial -> spicevmc chardev ->
-> spicevmc channel -> unix socket -> $random app on client
4) On hind sight this could also have been used for the smartcard stuff,
with a 1 channel / reader model, rather then the current multiplexing code
where we've our own multiplexing protocol wrapper over the libcacard
smartcard protocol.
Signed-off-by: Hans de Goede <hdegoede@redhat.com>
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