spice/server/spicevmc.cpp

/* spice-server spicevmc passthrough channel code

   Copyright (C) 2011 Red Hat, Inc.

   Red Hat Authors:
   Hans de Goede <hdegoede@redhat.com>

   This library is free software; you can redistribute it and/or
   modify it under the terms of the GNU Lesser General Public
   License as published by the Free Software Foundation; either
   version 2.1 of the License, or (at your option) any later version.

   This library is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
   Lesser General Public License for more details.

   You should have received a copy of the GNU Lesser General Public
   License along with this library; if not, see <http://www.gnu.org/licenses/>.
*/
#include <config.h>

#include <assert.h>
#include <string.h>
#ifdef USE_LZ4
#include <lz4.h>
#endif

#include <common/generated_server_marshallers.h>

#include "char-device.h"
#include "red-channel.h"
#include "red-channel-client.h"
#include "reds.h"
#include "migration-protocol.h"

/* 64K should be enough for all but the largest writes + 32 bytes hdr */
#define BUF_SIZE (64 * 1024 + 32)
#define COMPRESS_THRESHOLD 1000

// limit of the queued data, at this limit we stop reading from device to
// avoid DoS
#define QUEUED_DATA_LIMIT (1024*1024)

SPICE_DECLARE_TYPE(RedCharDeviceSpiceVmc, red_char_device_spicevmc, CHAR_DEVICE_SPICEVMC);
#define RED_TYPE_CHAR_DEVICE_SPICEVMC red_char_device_spicevmc_get_type()

SPICE_DECLARE_TYPE(RedVmcChannel, red_vmc_channel, VMC_CHANNEL);
#define RED_TYPE_VMC_CHANNEL red_vmc_channel_get_type()

SPICE_DECLARE_TYPE(RedVmcChannelPort, red_vmc_channel_port, VMC_CHANNEL_PORT);
#define RED_TYPE_VMC_CHANNEL_PORT red_vmc_channel_port_get_type()

SPICE_DECLARE_TYPE(RedVmcChannelUsbredir, red_vmc_channel_usbredir, VMC_CHANNEL_USBREDIR);
#define RED_TYPE_VMC_CHANNEL_USBREDIR red_vmc_channel_usbredir_get_type()

SPICE_DECLARE_TYPE(RedVmcChannelWebdav, red_vmc_channel_webdav, VMC_CHANNEL_WEBDAV);
#define RED_TYPE_VMC_CHANNEL_WEBDAV red_vmc_channel_webdav_get_type()

typedef struct RedVmcPipeItem {
    RedPipeItem base;

    SpiceDataCompressionType type;
    uint32_t uncompressed_data_size;
    /* writes which don't fit this will get split, this is not a problem */
    uint8_t buf[BUF_SIZE];
    uint32_t buf_used;
} RedVmcPipeItem;

struct RedCharDeviceSpiceVmc {
    RedCharDevice parent;
    RedVmcChannel *channel;
};

struct RedCharDeviceSpiceVmcClass
{
    RedCharDeviceClass parent_class;
};

static RedCharDevice *red_char_device_spicevmc_new(SpiceCharDeviceInstance *sin,
                                                   RedsState *reds,
                                                   RedVmcChannel *channel);
static void spicevmc_red_channel_queue_data(RedVmcChannel *channel, RedVmcPipeItem *item);

G_DEFINE_TYPE(RedCharDeviceSpiceVmc, red_char_device_spicevmc, RED_TYPE_CHAR_DEVICE)

struct RedVmcChannel: public RedChannel
{
    RedChannelClient *rcc;
    RedCharDevice *chardev; /* weak */
    SpiceCharDeviceInstance *chardev_sin;
    RedVmcPipeItem *pipe_item;
    RedCharDeviceWriteBuffer *recv_from_client_buf;
    uint8_t port_opened;
    uint32_t queued_data;
    RedStatCounter in_data;
    RedStatCounter in_compressed;
    RedStatCounter in_decompressed;
    RedStatCounter out_data;
    RedStatCounter out_compressed;
    RedStatCounter out_uncompressed;
};

struct RedVmcChannelClass
{
    RedChannelClass parent_class;
};

G_DEFINE_TYPE(RedVmcChannel, red_vmc_channel, RED_TYPE_CHANNEL)

struct RedVmcChannelUsbredir final: public RedVmcChannel
{
};

struct RedVmcChannelUsbredirClass
{
    RedVmcChannelClass parent_class;
};

static void red_vmc_channel_usbredir_init(RedVmcChannelUsbredir *self)
{
}
G_DEFINE_TYPE(RedVmcChannelUsbredir, red_vmc_channel_usbredir, RED_TYPE_VMC_CHANNEL)


struct RedVmcChannelWebdav final: public RedVmcChannel
{
};

struct RedVmcChannelWebdavClass
{
    RedVmcChannelClass parent_class;
};

static void red_vmc_channel_webdav_init(RedVmcChannelWebdav *self)
{
}
G_DEFINE_TYPE(RedVmcChannelWebdav, red_vmc_channel_webdav, RED_TYPE_VMC_CHANNEL)


struct RedVmcChannelPort final: public RedVmcChannel
{
};

struct RedVmcChannelPortClass
{
    RedVmcChannelClass parent_class;
};

static void red_vmc_channel_port_init(RedVmcChannelPort *self)
{
}
G_DEFINE_TYPE(RedVmcChannelPort, red_vmc_channel_port, RED_TYPE_VMC_CHANNEL)


class VmcChannelClient final: public RedChannelClient
{
    using RedChannelClient::RedChannelClient;

    virtual uint8_t *alloc_recv_buf(uint16_t type, uint32_t size) override;
    virtual void release_recv_buf(uint16_t type, uint32_t size, uint8_t *msg) override;
    virtual void on_disconnect() override;
};

static RedChannelClient *
vmc_channel_client_create(RedChannel *channel, RedClient *client,
                          RedStream *stream,
                          RedChannelCapabilities *caps);


static void spicevmc_connect(RedChannel *channel, RedClient *client,
                             RedStream *stream, int migration,
                             RedChannelCapabilities *caps);

static void
red_vmc_channel_constructed(GObject *object)
{
    RedVmcChannel *self = RED_VMC_CHANNEL(object);
    RedsState *reds = self->get_server();

    G_OBJECT_CLASS(red_vmc_channel_parent_class)->constructed(object);

    self->init_stat_node(NULL, "spicevmc");
    const RedStatNode *stat = self->get_stat_node();
    stat_init_counter(&self->in_data, reds, stat, "in_data", TRUE);
    stat_init_counter(&self->in_compressed, reds, stat, "in_compressed", TRUE);
    stat_init_counter(&self->in_decompressed, reds, stat, "in_decompressed", TRUE);
    stat_init_counter(&self->out_data, reds, stat, "out_data", TRUE);
    stat_init_counter(&self->out_compressed, reds, stat, "out_compressed", TRUE);
    stat_init_counter(&self->out_uncompressed, reds, stat, "out_uncompressed", TRUE);

#ifdef USE_LZ4
    self->set_cap(SPICE_SPICEVMC_CAP_DATA_COMPRESS_LZ4);
#endif

    reds_register_channel(reds, self);
}

static void
red_vmc_channel_init(RedVmcChannel *self)
{
}

static void
red_vmc_channel_finalize(GObject *object)
{
    RedVmcChannel *self = RED_VMC_CHANNEL(object);

    red_char_device_write_buffer_release(self->chardev, &self->recv_from_client_buf);
    if (self->pipe_item) {
        red_pipe_item_unref(&self->pipe_item->base);
    }

    G_OBJECT_CLASS(red_vmc_channel_parent_class)->finalize(object);
}

static RedVmcChannel *red_vmc_channel_new(RedsState *reds, uint8_t channel_type)
{
    GType gtype = G_TYPE_NONE;

    switch (channel_type) {
        case SPICE_CHANNEL_USBREDIR:
            gtype = RED_TYPE_VMC_CHANNEL_USBREDIR;
            break;
        case SPICE_CHANNEL_WEBDAV:
            gtype = RED_TYPE_VMC_CHANNEL_WEBDAV;
            break;
        case SPICE_CHANNEL_PORT:
            gtype = RED_TYPE_VMC_CHANNEL_PORT;
            break;
        default:
            g_error("Unsupported channel_type for red_vmc_channel_new(): %u", channel_type);
            return NULL;
    }

    int id = reds_get_free_channel_id(reds, channel_type);
    if (id < 0) {
        g_warning("Free ID not found creating new VMC channel");
        return NULL;
    }

    return (RedVmcChannel*) g_object_new(gtype,
                        "spice-server", reds,
                        "core-interface", reds_get_core_interface(reds),
                        "channel-type", channel_type,
                        "id", id,
                        "migration-flags",
                        (SPICE_MIGRATE_NEED_FLUSH | SPICE_MIGRATE_NEED_DATA_TRANSFER),
                        NULL);
}

typedef struct RedPortInitPipeItem {
    RedPipeItem base;
    char* name;
    uint8_t opened;
} RedPortInitPipeItem;

typedef struct RedPortEventPipeItem {
    RedPipeItem base;
    uint8_t event;
} RedPortEventPipeItem;

enum {
    RED_PIPE_ITEM_TYPE_SPICEVMC_DATA = RED_PIPE_ITEM_TYPE_CHANNEL_BASE,
    RED_PIPE_ITEM_TYPE_SPICEVMC_MIGRATE_DATA,
    RED_PIPE_ITEM_TYPE_PORT_INIT,
    RED_PIPE_ITEM_TYPE_PORT_EVENT,
};

/* n is the data size (uncompressed)
 * msg_item -- the current pipe item with the uncompressed data
 * This function returns:
 *  - NULL upon failure.
 *  - a new pipe item with the compressed data in it upon success
 */
#ifdef USE_LZ4
static RedVmcPipeItem* try_compress_lz4(RedVmcChannel *channel, int n, RedVmcPipeItem *msg_item)
{
    RedVmcPipeItem *msg_item_compressed;
    int compressed_data_count;

    if (red_stream_get_family(channel->rcc->get_stream()) == AF_UNIX) {
        /* AF_LOCAL - data will not be compressed */
        return NULL;
    }
    if (n <= COMPRESS_THRESHOLD) {
        /* n <= threshold - data will not be compressed */
        return NULL;
    }
    if (!channel->rcc->test_remote_cap(SPICE_SPICEVMC_CAP_DATA_COMPRESS_LZ4)) {
        /* Client doesn't have compression cap - data will not be compressed */
        return NULL;
    }
    msg_item_compressed = g_new0(RedVmcPipeItem, 1);
    red_pipe_item_init(&msg_item_compressed->base, RED_PIPE_ITEM_TYPE_SPICEVMC_DATA);
    compressed_data_count = LZ4_compress_default((char*)&msg_item->buf,
                                                 (char*)&msg_item_compressed->buf,
                                                 n,
                                                 BUF_SIZE);

    if (compressed_data_count > 0 && compressed_data_count < n) {
        stat_inc_counter(channel->out_uncompressed, n);
        stat_inc_counter(channel->out_compressed, compressed_data_count);
        msg_item_compressed->type = SPICE_DATA_COMPRESSION_TYPE_LZ4;
        msg_item_compressed->uncompressed_data_size = n;
        msg_item_compressed->buf_used = compressed_data_count;
        g_free(msg_item);
        return msg_item_compressed;
    }

    /* LZ4 compression failed or did non compress, fallback a non-compressed data is to be sent */
    g_free(msg_item_compressed);
    return NULL;
}
#endif

static RedPipeItem *spicevmc_chardev_read_msg_from_dev(RedCharDevice *self,
                                                       SpiceCharDeviceInstance *sin)
{
    RedCharDeviceSpiceVmc *vmc = RED_CHAR_DEVICE_SPICEVMC(self);
    RedVmcChannel *channel = RED_VMC_CHANNEL(vmc->channel);
    SpiceCharDeviceInterface *sif;
    RedVmcPipeItem *msg_item;
    int n;

    sif = spice_char_device_get_interface(sin);

    if (!channel->rcc || channel->queued_data >= QUEUED_DATA_LIMIT) {
        return NULL;
    }

    if (!channel->pipe_item) {
        msg_item = g_new0(RedVmcPipeItem, 1);
        msg_item->type = SPICE_DATA_COMPRESSION_TYPE_NONE;
        red_pipe_item_init(&msg_item->base, RED_PIPE_ITEM_TYPE_SPICEVMC_DATA);
    } else {
        spice_assert(channel->pipe_item->buf_used == 0);
        msg_item = channel->pipe_item;
        channel->pipe_item = NULL;
    }

    n = sif->read(sin, msg_item->buf,
                  sizeof(msg_item->buf));
    if (n > 0) {
        spice_debug("read from dev %d", n);
#ifdef USE_LZ4
        RedVmcPipeItem *msg_item_compressed;

        msg_item_compressed = try_compress_lz4(channel, n, msg_item);
        if (msg_item_compressed != NULL) {
            spicevmc_red_channel_queue_data(channel, msg_item_compressed);
            return NULL;
        }
#endif
        stat_inc_counter(channel->out_data, n);
        msg_item->uncompressed_data_size = n;
        msg_item->buf_used = n;
        spicevmc_red_channel_queue_data(channel, msg_item);
        return NULL;
    }
    channel->pipe_item = msg_item;
    return NULL;
}

static void red_port_init_item_free(struct RedPipeItem *base)
{
    RedPortInitPipeItem *item = SPICE_UPCAST(RedPortInitPipeItem, base);

    g_free(item->name);
    g_free(item);
}

static void spicevmc_port_send_init(RedChannelClient *rcc)
{
    RedVmcChannel *channel = RED_VMC_CHANNEL(rcc->get_channel());
    SpiceCharDeviceInstance *sin = channel->chardev_sin;
    RedPortInitPipeItem *item = g_new(RedPortInitPipeItem, 1);

    red_pipe_item_init_full(&item->base, RED_PIPE_ITEM_TYPE_PORT_INIT, red_port_init_item_free);
    item->name = g_strdup(sin->portname);
    item->opened = channel->port_opened;
    rcc->pipe_add_push(&item->base);
}

static void spicevmc_port_send_event(RedChannelClient *rcc, uint8_t event)
{
    RedPortEventPipeItem *item = g_new(RedPortEventPipeItem, 1);

    red_pipe_item_init(&item->base, RED_PIPE_ITEM_TYPE_PORT_EVENT);
    item->event = event;
    rcc->pipe_add_push(&item->base);
}

static void spicevmc_char_dev_remove_client(RedCharDevice *self,
                                            RedClient *client)
{
    RedCharDeviceSpiceVmc *vmc = RED_CHAR_DEVICE_SPICEVMC(self);
    RedVmcChannel *channel = RED_VMC_CHANNEL(vmc->channel);

    spice_assert(channel->rcc &&
                 channel->rcc->get_client() == client);

    channel->rcc->shutdown();
}

void VmcChannelClient::on_disconnect()
{
    RedVmcChannel *channel;
    SpiceCharDeviceInterface *sif;
    RedClient *client = get_client();

    channel = RED_VMC_CHANNEL(get_channel());

    /* partial message which wasn't pushed to device */
    red_char_device_write_buffer_release(channel->chardev, &channel->recv_from_client_buf);

    if (channel->chardev) {
        if (red_char_device_client_exists(channel->chardev, client)) {
            red_char_device_client_remove(channel->chardev, client);
        } else {
            red_channel_warning(channel,
                                "client %p have already been removed from char dev %p",
                                client, channel->chardev);
        }
    }

    channel->rcc = NULL;
    sif = spice_char_device_get_interface(channel->chardev_sin);
    if (sif->state) {
        sif->state(channel->chardev_sin, 0);
    }
}

static bool spicevmc_channel_client_handle_migrate_flush_mark(RedChannelClient *rcc)
{
    rcc->pipe_add_type(RED_PIPE_ITEM_TYPE_SPICEVMC_MIGRATE_DATA);
    return TRUE;
}

static bool spicevmc_channel_client_handle_migrate_data(RedChannelClient *rcc,
                                                        uint32_t size, void *message)
{
    SpiceMigrateDataHeader *header;
    SpiceMigrateDataSpiceVmc *mig_data;
    RedVmcChannel *channel;

    channel = RED_VMC_CHANNEL(rcc->get_channel());

    header = (SpiceMigrateDataHeader *)message;
    mig_data = (SpiceMigrateDataSpiceVmc *)(header + 1);
    spice_assert(size >= sizeof(SpiceMigrateDataHeader) + sizeof(SpiceMigrateDataSpiceVmc));

    if (!migration_protocol_validate_header(header,
                                            SPICE_MIGRATE_DATA_SPICEVMC_MAGIC,
                                            SPICE_MIGRATE_DATA_SPICEVMC_VERSION)) {
        spice_error("bad header");
        return FALSE;
    }
    return red_char_device_restore(channel->chardev, &mig_data->base);
}

static bool handle_compressed_msg(RedVmcChannel *channel, RedChannelClient *rcc,
                                  SpiceMsgCompressedData *compressed_data_msg)
{
    /* NOTE: *decompressed is free by the char-device */
    int decompressed_size;
    RedCharDeviceWriteBuffer *write_buf;

    write_buf = red_char_device_write_buffer_get_server(channel->chardev,
                                                        compressed_data_msg->uncompressed_size,
                                                        false);
    if (!write_buf) {
        return FALSE;
    }

    switch (compressed_data_msg->type) {
#ifdef USE_LZ4
    case SPICE_DATA_COMPRESSION_TYPE_LZ4: {
        uint8_t *decompressed = write_buf->buf;
        decompressed_size = LZ4_decompress_safe ((char *)compressed_data_msg->compressed_data,
                                                 (char *)decompressed,
                                                 compressed_data_msg->compressed_size,
                                                 compressed_data_msg->uncompressed_size);
        stat_inc_counter(channel->in_compressed, compressed_data_msg->compressed_size);
        stat_inc_counter(channel->in_decompressed, decompressed_size);
        break;
    }
#endif
    default:
        spice_warning("Invalid Compression Type");
        red_char_device_write_buffer_release(channel->chardev, &write_buf);
        return FALSE;
    }
    if (decompressed_size != compressed_data_msg->uncompressed_size) {
        spice_warning("Decompression Error");
        red_char_device_write_buffer_release(channel->chardev, &write_buf);
        return FALSE;
    }
    write_buf->buf_used = decompressed_size;
    red_char_device_write_buffer_add(channel->chardev, write_buf);
    return TRUE;
}

static bool spicevmc_red_channel_client_handle_message(RedChannelClient *rcc,
                                                       uint16_t type,
                                                       uint32_t size,
                                                       void *msg)
{
    /* NOTE: *msg free by g_free() (when cb to VmcChannelClient::release_recv_buf
     * with the compressed msg type) */
    RedVmcChannel *channel;
    SpiceCharDeviceInterface *sif;

    channel = RED_VMC_CHANNEL(rcc->get_channel());
    sif = spice_char_device_get_interface(channel->chardev_sin);

    switch (type) {
    case SPICE_MSGC_SPICEVMC_DATA:
        spice_assert(channel->recv_from_client_buf->buf == msg);
        stat_inc_counter(channel->in_data, size);
        channel->recv_from_client_buf->buf_used = size;
        red_char_device_write_buffer_add(channel->chardev, channel->recv_from_client_buf);
        channel->recv_from_client_buf = NULL;
        break;
    case SPICE_MSGC_SPICEVMC_COMPRESSED_DATA:
        return handle_compressed_msg(channel, rcc, (SpiceMsgCompressedData*)msg);
        break;
    case SPICE_MSGC_PORT_EVENT:
        if (size != sizeof(uint8_t)) {
            spice_warning("bad port event message size");
            return FALSE;
        }
        if (sif->base.minor_version >= 2 && sif->event != NULL)
            sif->event(channel->chardev_sin, *(uint8_t*)msg);
        break;
    default:
        return RedChannelClient::handle_message(rcc, type, size, msg);
    }

    return TRUE;
}

/* if device manage to send some data attempt to unblock the channel */
static void spicevmc_on_free_self_token(RedCharDevice *self)
{
    RedCharDeviceSpiceVmc *vmc = RED_CHAR_DEVICE_SPICEVMC(self);
    RedVmcChannel *channel = RED_VMC_CHANNEL(vmc->channel);

    channel->rcc->unblock_read();
}

uint8_t *VmcChannelClient::alloc_recv_buf(uint16_t type, uint32_t size)
{

    switch (type) {
    case SPICE_MSGC_SPICEVMC_DATA: {
        RedVmcChannel *channel = RED_VMC_CHANNEL(get_channel());

        assert(!channel->recv_from_client_buf);

        channel->recv_from_client_buf = red_char_device_write_buffer_get_server(channel->chardev,
                                                                                size, true);
        if (!channel->recv_from_client_buf) {
            block_read();
            return NULL;
        }
        return channel->recv_from_client_buf->buf;
    }

    default:
        return (uint8_t*) g_malloc(size);
    }

}

void VmcChannelClient::release_recv_buf(uint16_t type, uint32_t size, uint8_t *msg)
{

    switch (type) {
    case SPICE_MSGC_SPICEVMC_DATA: {
        RedVmcChannel *channel = RED_VMC_CHANNEL(get_channel());
        /* buffer wasn't pushed to device */
        red_char_device_write_buffer_release(channel->chardev, &channel->recv_from_client_buf);
        break;
    }
    default:
        g_free(msg);
    }
}

static void
spicevmc_red_channel_queue_data(RedVmcChannel *channel, RedVmcPipeItem *item)
{
    channel->queued_data += item->buf_used;
    channel->rcc->pipe_add_push(&item->base);
}

static void spicevmc_red_channel_send_data(RedChannelClient *rcc,
                                           SpiceMarshaller *m,
                                           RedPipeItem *item)
{
    RedVmcPipeItem *i = SPICE_UPCAST(RedVmcPipeItem, item);
    RedVmcChannel *channel = RED_VMC_CHANNEL(rcc->get_channel());

    /* for compatibility send using not compressed data message */
    if (i->type == SPICE_DATA_COMPRESSION_TYPE_NONE) {
        rcc->init_send_data(SPICE_MSG_SPICEVMC_DATA);
    } else {
        /* send as compressed */
        rcc->init_send_data(SPICE_MSG_SPICEVMC_COMPRESSED_DATA);
        SpiceMsgCompressedData compressed_msg = {
            .type = i->type,
            .uncompressed_size = i->uncompressed_data_size
        };
        spice_marshall_SpiceMsgCompressedData(m, &compressed_msg);
    }
    red_pipe_item_ref(item);
    spice_marshaller_add_by_ref_full(m, i->buf, i->buf_used,
                                     marshaller_unref_pipe_item, item);

    // account for sent data and wake up device if was blocked
    uint32_t old_queued_data = channel->queued_data;
    channel->queued_data -= i->buf_used;
    if (channel->chardev &&
        old_queued_data >= QUEUED_DATA_LIMIT && channel->queued_data < QUEUED_DATA_LIMIT) {
        red_char_device_wakeup(channel->chardev);
    }
}

static void spicevmc_red_channel_send_migrate_data(RedChannelClient *rcc,
                                                   SpiceMarshaller *m,
                                                   RedPipeItem *item)
{
    RedVmcChannel *channel;

    channel = RED_VMC_CHANNEL(rcc->get_channel());
    rcc->init_send_data(SPICE_MSG_MIGRATE_DATA);
    spice_marshaller_add_uint32(m, SPICE_MIGRATE_DATA_SPICEVMC_MAGIC);
    spice_marshaller_add_uint32(m, SPICE_MIGRATE_DATA_SPICEVMC_VERSION);

    red_char_device_migrate_data_marshall(channel->chardev, m);
}

static void spicevmc_red_channel_send_port_init(RedChannelClient *rcc,
                                                SpiceMarshaller *m,
                                                RedPipeItem *item)
{
    RedPortInitPipeItem *i = SPICE_UPCAST(RedPortInitPipeItem, item);
    SpiceMsgPortInit init;

    rcc->init_send_data(SPICE_MSG_PORT_INIT);
    init.name = (uint8_t *)i->name;
    init.name_size = strlen(i->name) + 1;
    init.opened = i->opened;
    spice_marshall_msg_port_init(m, &init);
}

static void spicevmc_red_channel_send_port_event(RedChannelClient *rcc,
                                                 SpiceMarshaller *m,
                                                 RedPipeItem *item)
{
    RedPortEventPipeItem *i = SPICE_UPCAST(RedPortEventPipeItem, item);
    SpiceMsgPortEvent event;

    rcc->init_send_data(SPICE_MSG_PORT_EVENT);
    event.event = i->event;
    spice_marshall_msg_port_event(m, &event);
}

static void spicevmc_red_channel_send_item(RedChannelClient *rcc,
                                           RedPipeItem *item)
{
    SpiceMarshaller *m = rcc->get_marshaller();

    switch (item->type) {
    case RED_PIPE_ITEM_TYPE_SPICEVMC_DATA:
        spicevmc_red_channel_send_data(rcc, m, item);
        break;
    case RED_PIPE_ITEM_TYPE_SPICEVMC_MIGRATE_DATA:
        spicevmc_red_channel_send_migrate_data(rcc, m, item);
        break;
    case RED_PIPE_ITEM_TYPE_PORT_INIT:
        spicevmc_red_channel_send_port_init(rcc, m, item);
        break;
    case RED_PIPE_ITEM_TYPE_PORT_EVENT:
        spicevmc_red_channel_send_port_event(rcc, m, item);
        break;
    default:
        spice_error("bad pipe item %d", item->type);
        return;
    }
    rcc->begin_send_message();
}


static void
red_vmc_channel_class_init(RedVmcChannelClass *klass)
{
    GObjectClass *object_class = G_OBJECT_CLASS(klass);
    RedChannelClass *channel_class = RED_CHANNEL_CLASS(klass);

    object_class->constructed = red_vmc_channel_constructed;
    object_class->finalize = red_vmc_channel_finalize;

    channel_class->handle_message = spicevmc_red_channel_client_handle_message;

    channel_class->send_item = spicevmc_red_channel_send_item;
    channel_class->handle_migrate_flush_mark = spicevmc_channel_client_handle_migrate_flush_mark;
    channel_class->handle_migrate_data = spicevmc_channel_client_handle_migrate_data;

    // client callbacks
    channel_class->connect = spicevmc_connect;
}

static void
red_vmc_channel_usbredir_class_init(RedVmcChannelUsbredirClass *klass)
{
    RedChannelClass *channel_class = RED_CHANNEL_CLASS(klass);

    channel_class->parser = spice_get_client_channel_parser(SPICE_CHANNEL_USBREDIR, NULL);
}

static void
red_vmc_channel_webdav_class_init(RedVmcChannelWebdavClass *klass)
{
    RedChannelClass *channel_class = RED_CHANNEL_CLASS(klass);

    channel_class->parser = spice_get_client_channel_parser(SPICE_CHANNEL_WEBDAV, NULL);
}

static void
red_vmc_channel_port_class_init(RedVmcChannelPortClass *klass)
{
    RedChannelClass *channel_class = RED_CHANNEL_CLASS(klass);

    channel_class->parser = spice_get_client_channel_parser(SPICE_CHANNEL_PORT, NULL);
}

static void spicevmc_connect(RedChannel *channel, RedClient *client,
    RedStream *stream, int migration,
    RedChannelCapabilities *caps)
{
    RedChannelClient *rcc;
    RedVmcChannel *vmc_channel;
    SpiceCharDeviceInstance *sin;
    SpiceCharDeviceInterface *sif;

    vmc_channel = RED_VMC_CHANNEL(channel);
    sin = vmc_channel->chardev_sin;

    if (vmc_channel->rcc) {
        red_channel_warning(channel,
                            "channel client (%p) already connected, refusing second connection",
                            vmc_channel->rcc);
        // TODO: notify client in advance about the in use channel using
        // SPICE_MSG_MAIN_CHANNEL_IN_USE (for example)
        red_stream_free(stream);
        return;
    }

    rcc = vmc_channel_client_create(channel, client, stream, caps);
    if (!rcc) {
        return;
    }
    vmc_channel->rcc = rcc;
    vmc_channel->queued_data = 0;
    rcc->ack_zero_messages_window();

    if (strcmp(sin->subtype, "port") == 0) {
        spicevmc_port_send_init(rcc);
    }

    if (!red_char_device_client_add(vmc_channel->chardev, client, FALSE, 0, ~0, ~0,
                                    rcc->is_waiting_for_migrate_data())) {
        spice_warning("failed to add client to spicevmc");
        rcc->disconnect();
        return;
    }

    sif = spice_char_device_get_interface(sin);
    if (sif->state) {
        sif->state(sin, 1);
    }
}

RedCharDevice *spicevmc_device_connect(RedsState *reds,
                                       SpiceCharDeviceInstance *sin,
                                       uint8_t channel_type)
{
    RedCharDevice *dev;
    RedVmcChannel *channel = red_vmc_channel_new(reds, channel_type);
    if (!channel) {
        return NULL;
    }

    /* char device takes ownership of channel */
    dev = red_char_device_spicevmc_new(sin, reds, channel);

    channel->chardev_sin = sin;
    g_object_unref(channel);

    return dev;
}

/* Must be called from RedClient handling thread. */
void spicevmc_device_disconnect(SpiceCharDeviceInstance *sin)
{
    g_object_unref(RED_CHAR_DEVICE(sin->st));
    sin->st = NULL;
}

static void spicevmc_port_event(RedCharDevice *char_dev, uint8_t event)
{
    RedVmcChannel *channel;
    RedCharDeviceSpiceVmc *device = RED_CHAR_DEVICE_SPICEVMC(char_dev);

    channel = RED_VMC_CHANNEL(device->channel);

    if (event == SPICE_PORT_EVENT_OPENED) {
        channel->port_opened = TRUE;
    } else if (event == SPICE_PORT_EVENT_CLOSED) {
        channel->port_opened = FALSE;
    }

    if (channel->rcc == NULL) {
        return;
    }

    spicevmc_port_send_event(channel->rcc, event);
}

static void
red_char_device_spicevmc_dispose(GObject *object)
{
    RedCharDeviceSpiceVmc *self = RED_CHAR_DEVICE_SPICEVMC(object);

    if (self->channel) {
        // prevent possible recursive calls
        self->channel->chardev = NULL;

        // close all current connections and drop the reference
        self->channel->destroy();
        self->channel = NULL;
    }
    G_OBJECT_CLASS(red_char_device_spicevmc_parent_class)->dispose(object);
}

enum {
    PROP0,
    PROP_CHANNEL
};

static void
red_char_device_spicevmc_set_property(GObject *object,
                                      guint property_id,
                                      const GValue *value,
                                      GParamSpec *pspec)
{
    RedCharDeviceSpiceVmc *self = RED_CHAR_DEVICE_SPICEVMC(object);

    switch (property_id)
    {
        case PROP_CHANNEL:
            spice_assert(self->channel == NULL);
            self->channel = (RedVmcChannel*) g_value_dup_object(value);
            spice_assert(self->channel != NULL);
            self->channel->chardev = RED_CHAR_DEVICE(self);

            break;
        default:
            G_OBJECT_WARN_INVALID_PROPERTY_ID(object, property_id, pspec);
    }
}

static void
red_char_device_spicevmc_class_init(RedCharDeviceSpiceVmcClass *klass)
{
    GObjectClass *object_class = G_OBJECT_CLASS(klass);
    RedCharDeviceClass *char_dev_class = RED_CHAR_DEVICE_CLASS(klass);

    object_class->set_property = red_char_device_spicevmc_set_property;
    object_class->dispose = red_char_device_spicevmc_dispose;

    char_dev_class->read_one_msg_from_device = spicevmc_chardev_read_msg_from_dev;
    char_dev_class->remove_client = spicevmc_char_dev_remove_client;
    char_dev_class->port_event = spicevmc_port_event;
    char_dev_class->on_free_self_token = spicevmc_on_free_self_token;

    g_object_class_install_property(object_class,
                                    PROP_CHANNEL,
                                    g_param_spec_object("channel",
                                                        "Channel",
                                                        "Channel associated with this device",
                                                        RED_TYPE_VMC_CHANNEL,
                                                        G_PARAM_STATIC_STRINGS |
                                                        G_PARAM_WRITABLE |
                                                        G_PARAM_CONSTRUCT));
}

static void
red_char_device_spicevmc_init(RedCharDeviceSpiceVmc *self)
{
}

static RedCharDevice *
red_char_device_spicevmc_new(SpiceCharDeviceInstance *sin,
                             RedsState *reds,
                             RedVmcChannel *channel)
{
    return (RedCharDevice*) g_object_new(RED_TYPE_CHAR_DEVICE_SPICEVMC,
                        "sin", sin,
                        "spice-server", reds,
                        "client-tokens-interval", 0ULL,
                        "self-tokens", UINT64_C(128), // limit number of messages sent to device
                        "channel", channel,
                        NULL);
}

static RedChannelClient *
vmc_channel_client_create(RedChannel *channel, RedClient *client,
                          RedStream *stream,
                          RedChannelCapabilities *caps)
{
    auto rcc = new VmcChannelClient(channel, client, stream, caps);
    if (!rcc->init()) {
        delete rcc;
        rcc = nullptr;
    }
    return rcc;
}