[Spice-devel] [PATCH vdagent-linux 3/4] introduce VDAgentConnection

Victor Toso victortoso at redhat.com
Thu Dec 6 15:19:59 UTC 2018


Hi,

First of all, tested. Seems to work fine!

This one I think it can be improved to have a clear design around
VDAgentConnection. The other three patches could be merged faster
I think, if you want.

On Sun, Sep 30, 2018 at 08:05:22PM +0200, Jakub Janků wrote:
> 1) VDAgentConnection
> 
> Add vdagent-connection.{c,h} files.
> 
> Define a new GObject: VDAgentConnection which can be used to
> easily write messages to and read from the given FD.

What is the plan to virtio-port and udscs files/functions? They
all seen similar. I really like the idea that we use one
interface for both vdagent <-> vdagentd and vdagentd <-> client
and it would be nice to move towards that direction.

I'm not sure myself exactly which API would be enough. I think
that is not difficult to remove more code with the current
version so I think is a good thing.

At some point I looked at vdagent-gtk from elmarco and something
along that could be used as inspiration,

    https://github.com/elmarco/vdagent-gtk/commit/ed83e0e12118c1d46cda85c8902a3a4ce0157d76

> VDAgentConnection uses GIO and therefore integrates well with GMainLoop.
> 
> Read messages must begin with a header of a fixed size.
> Message body size can vary.
> 
> User of VDAgentConnection is notified
> through callbacks about the following events:
>  * message header read
>  * whole message read
>  * I/O error

I think it is easier to extend using signals and attach a handler
to them instead of increasing callback to APIs like
vdagent_connection_new(). My suggestion don't necessary fit with
previous design.

> A new VDAgentConnection can be constructed using
> vdagent_connection_new() based on a GIOStream that can be
> obtained using vdagent_file_open() or vdagent_socket_connect().
>
> vdagent_connection_destroy() destroyes the connection.
> However, due to the asynchronous nature of used GIO functions,
> this does NOT close the underlying FD immediately.

It should by the time GMainLoop exits, AFAIK.

> If vdagent_connection_destroy() is called outside of GMainLoop
> (or the loop quits right after the function ivocation),
> g_main_context_iteration() should be called to ensure that the
> VDAgentConnection finalizes properly.

I'm missing why this is necessary. Is it related to the
discussion from September?

    https://lists.freedesktop.org/archives/spice-devel/2018-September/045516.html

What kind of issue are you seeing without calling
g_main_context_iteration() ?

> 2) udscs
> 
> Rewrite udscs.c to use the new VDAgentConnection.
> Use GSocketService in udscs_server.
> 
> Drop support for select(), remove:
>  * udscs_server_fill_fds()
>  * udscs_server_handle_fds()
> 
> 3) virtio_port
> 
> Rewrite virtio-port.c to use the new VDAgentConnection.
> 
> Drop support for select(), remove:
>  * vdagent_virtio_port_fill_fds()
>  * vdagent_virtio_port_handle_fds()
> 
> 2) vdagentd

4) :)

> 
> Replace the main_loop() with a GMainLoop.

o/

> Use g_unix_signal_add() to handle SIGINT, SIGHUP, SIGTERM.
> SIGQUIT handling is not supported by GLib.

That's fine

> Integrate the session_info into the loop using
> GIOChannel and g_io_add_watch().
> 
> Signed-off-by: Jakub Janků <jjanku at redhat.com>
> ---
>  Makefile.am                |   2 +
>  src/udscs.c                | 483 +++++++++++--------------------------
>  src/udscs.h                |  15 --
>  src/vdagent-connection.c   | 300 +++++++++++++++++++++++
>  src/vdagent-connection.h   | 124 ++++++++++
>  src/vdagent/vdagent.c      |   3 +
>  src/vdagentd/vdagentd.c    | 169 ++++++-------
>  src/vdagentd/virtio-port.c | 389 ++++++++++-------------------
>  src/vdagentd/virtio-port.h |  18 --
>  9 files changed, 772 insertions(+), 731 deletions(-)
>  create mode 100644 src/vdagent-connection.c
>  create mode 100644 src/vdagent-connection.h

Not that big considering the implications.

> diff --git a/Makefile.am b/Makefile.am
> index fa54bbc..b291b19 100644
> --- a/Makefile.am
> +++ b/Makefile.am
> @@ -7,6 +7,8 @@ sbin_PROGRAMS = src/spice-vdagentd
>  common_sources =				\
>  	src/udscs.c				\
>  	src/udscs.h				\
> +	src/vdagent-connection.c		\
> +	src/vdagent-connection.h		\
>  	src/vdagentd-proto-strings.h		\
>  	src/vdagentd-proto.h			\
>  	$(NULL)
> diff --git a/src/udscs.c b/src/udscs.c
> index 62abc97..3bf0089 100644
> --- a/src/udscs.c
> +++ b/src/udscs.c
> @@ -24,42 +24,22 @@
>  #include <config.h>
>  #endif
>  
> -#include <stdio.h>
>  #include <stdlib.h>
>  #include <syslog.h>
> -#include <unistd.h>
> -#include <errno.h>
> -#include <sys/socket.h>
> -#include <sys/un.h>
> -#include <glib.h>
>  #include <glib-unix.h>
> +#include <gio/gunixsocketaddress.h>
>  #include "udscs.h"
>  #include "vdagentd-proto-strings.h"
> -
> -struct udscs_buf {
> -    uint8_t *buf;
> -    size_t pos;
> -    size_t size;
> -
> -    struct udscs_buf *next;
> -};
> +#include "vdagent-connection.h"
>  
>  struct udscs_connection {
> -    int fd;
>      int debug;
>      void *user_data;
>  #ifndef UDSCS_NO_SERVER
> -    struct ucred peer_cred;
> +    gint peer_pid;
>  #endif
>  
> -    /* Read stuff, single buffer, separate header and data buffer */
> -    int header_read;
> -    struct udscs_message_header header;
> -    struct udscs_buf data;
> -
> -    /* Writes are stored in a linked list of buffers, with both the header
> -       + data for a single message in 1 buffer. */
> -    struct udscs_buf *write_buf;
> +    VDAgentConnection *conn;

Naming... Several places uses conn for the parent struct
udscs_connection, so...

    conn->conn = vdagent_connection_new()

... happens later, on plus the callbacks such as conn_read_cb().
I'd say that 'agent' fits well, conn->agent would be read as
'udscs connection to agent'.

Not a big issue... I don't trust myself while naming things.

>      /* Callbacks */
>      udscs_read_callback read_callback;
> @@ -67,16 +47,8 @@ struct udscs_connection {
>  
>      struct udscs_connection *next;
>      struct udscs_connection *prev;
> -
> -    GIOChannel                     *io_channel;
> -    guint                           write_watch_id;
> -    guint                           read_watch_id;
>  };
>  
> -static gboolean udscs_io_channel_cb(GIOChannel *source,
> -                                    GIOCondition condition,
> -                                    gpointer data);
> -
>  static void debug_print_message_header(struct udscs_connection     *conn,
>                                         struct udscs_message_header *header,
>                                         const gchar                 *direction)
> @@ -93,47 +65,61 @@ static void debug_print_message_header(struct udscs_connection     *conn,
>          conn, direction, type, header->arg1, header->arg2, header->size);
>  }
>  
> +static gboolean conn_header_read_cb(gpointer header_buff,
> +                                    gsize   *body_size,
> +                                    gpointer user_data)
> +{
> +    struct udscs_message_header *header = header_buff;
> +    *body_size = header->size;
> +    return TRUE;
> +}

<snip>
    static gsize conn_header_read_cb(gpointer header_buff,
                                     gpointer user_data)
    {
        struct udscs_message_header *header = header_buff;
        return header->size;
    }
</snip>

The GIO-way of doing this is having fn_your_callback() being
called and there you call the calling_fn_done() or _finished() to
get errors, etc.

> +static gboolean conn_read_cb(gpointer header_buff,
> +                             gpointer data,
> +                             gpointer user_data)
> +{
> +    struct udscs_connection *conn = user_data;
> +    struct udscs_message_header *header = header_buff;
> +
> +    debug_print_message_header(conn, header, "received");
> +
> +    conn->read_callback(&conn, header, data);
> +    return conn != NULL;
> +}

It is very weird to me that you have to check if conn is not NULL
here. The callback clearing the caller is quite odd design.

I know that wasn't introduced by you [0] (below), but I think it
is possible to have the design improved with this changes
(GMainLoop one)

> +static void conn_error_cb(GError *err, gpointer user_data)
> +{
> +    struct udscs_connection *conn = user_data;
> +    if (err)
> +        syslog(LOG_ERR, "%p error: %s", conn, err->message);
> +    udscs_destroy_connection(&conn);
> +}

An error callback is better than quit=1 for sure :)

Still, It would be great if we can associate the error with the
functions that triggered them.

For instance, this error_cb can be called at message_write_cb()
from vdagent_connection_write(). We could either have:
  - vdagent_connection_write_now() which blocks and return
    failure/success or;
  - vdagent_connection_write_async() which has a callback to when
    async is done. As mentioned earlier, if we follow GIO, the
    callback would call vdagent_connection_write_finish() to get
    if there were any errors or perhaps, the number of bytes
    written, etc.

Also, any error called here should destroy connection?

> +
>  struct udscs_connection *udscs_connect(const char *socketname,
>      udscs_read_callback read_callback,
>      udscs_disconnect_callback disconnect_callback,
>      int debug)
>  {
> -    int c;
> -    struct sockaddr_un address;
> +    GIOStream *io_stream;
>      struct udscs_connection *conn;
> +    GError *err = NULL;
>  
> -    conn = g_new0(struct udscs_connection, 1);
> -    conn->debug = debug;
> -
> -    conn->fd = socket(PF_UNIX, SOCK_STREAM, 0);
> -    if (conn->fd == -1) {
> -        syslog(LOG_ERR, "creating unix domain socket: %m");
> -        g_free(conn);
> -        return NULL;
> -    }
> -
> -    address.sun_family = AF_UNIX;
> -    snprintf(address.sun_path, sizeof(address.sun_path), "%s", socketname);
> -    c = connect(conn->fd, (struct sockaddr *)&address, sizeof(address));
> -    if (c != 0) {
> -        if (conn->debug) {
> -            syslog(LOG_DEBUG, "connect %s: %m", socketname);
> -        }
> -        g_free(conn);
> -        return NULL;
> -    }
> -
> -    conn->io_channel = g_io_channel_unix_new(conn->fd);
> -    if (!conn->io_channel) {
> -        udscs_destroy_connection(&conn);
> +    io_stream = vdagent_socket_connect(socketname, &err);
> +    if (err) {
> +        syslog(LOG_ERR, "%s: %s", __func__, err->message);
> +        g_error_free(err);
>          return NULL;
>      }
> -    conn->read_watch_id =
> -        g_io_add_watch(conn->io_channel,
> -                       G_IO_IN | G_IO_ERR | G_IO_NVAL,
> -                       udscs_io_channel_cb,
> -                       conn);
>  
> +    conn = g_new0(struct udscs_connection, 1);
> +    conn->debug = debug;
> +    conn->conn = vdagent_connection_new(io_stream,
> +                                        FALSE,
> +                                        sizeof(struct udscs_message_header),
> +                                        conn_header_read_cb,
> +                                        conn_read_cb,
> +                                        conn_error_cb,
> +                                        conn);
>      conn->read_callback = read_callback;
>      conn->disconnect_callback = disconnect_callback;
>  
> @@ -145,7 +131,6 @@ struct udscs_connection *udscs_connect(const char *socketname,
>  
>  void udscs_destroy_connection(struct udscs_connection **connp)
>  {
> -    struct udscs_buf *wbuf, *next_wbuf;
>      struct udscs_connection *conn = *connp;
>  
>      if (!conn)
> @@ -154,28 +139,12 @@ void udscs_destroy_connection(struct udscs_connection **connp)
>      if (conn->disconnect_callback)
>          conn->disconnect_callback(conn);
>  
> -    wbuf = conn->write_buf;
> -    while (wbuf) {
> -        next_wbuf = wbuf->next;
> -        g_free(wbuf->buf);
> -        g_free(wbuf);
> -        wbuf = next_wbuf;
> -    }
> -
> -    g_clear_pointer(&conn->data.buf, g_free);
> -
>      if (conn->next)
>          conn->next->prev = conn->prev;
>      if (conn->prev)
>          conn->prev->next = conn->next;
>  
> -    close(conn->fd);
> -
> -    if (conn->write_watch_id != 0)
> -        g_source_remove(conn->write_watch_id);
> -    if (conn->read_watch_id != 0)
> -        g_source_remove(conn->read_watch_id);
> -    g_clear_pointer(&conn->io_channel, g_io_channel_unref);
> +    vdagent_connection_destroy(conn->conn);
>  
>      if (conn->debug)
>          syslog(LOG_DEBUG, "%p disconnected", conn);
> @@ -199,174 +168,33 @@ void *udscs_get_user_data(struct udscs_connection *conn)
>  void udscs_write(struct udscs_connection *conn, uint32_t type, uint32_t arg1,
>      uint32_t arg2, const uint8_t *data, uint32_t size)
>  {
> -    struct udscs_buf *wbuf, *new_wbuf;
> +    gpointer buff;
> +    guint buff_size;
>      struct udscs_message_header header;
>  
> -    new_wbuf = g_new(struct udscs_buf, 1);
> -    new_wbuf->pos = 0;
> -    new_wbuf->size = sizeof(header) + size;
> -    new_wbuf->next = NULL;
> -    new_wbuf->buf = g_malloc(new_wbuf->size);
> +    buff_size = sizeof(header) + size;
> +    buff = g_malloc(buff_size);
>  
>      header.type = type;
>      header.arg1 = arg1;
>      header.arg2 = arg2;
>      header.size = size;
>  
> -    memcpy(new_wbuf->buf, &header, sizeof(header));
> -    memcpy(new_wbuf->buf + sizeof(header), data, size);
> +    memcpy(buff, &header, sizeof(header));
> +    memcpy(buff + sizeof(header), data, size);
>  
>      debug_print_message_header(conn, &header, "sent");
>  
> -    if (conn->io_channel && conn->write_watch_id == 0)
> -        conn->write_watch_id =
> -            g_io_add_watch(conn->io_channel,
> -                           G_IO_OUT | G_IO_ERR | G_IO_NVAL,
> -                           udscs_io_channel_cb,
> -                           conn);
> -
> -    if (!conn->write_buf) {
> -        conn->write_buf = new_wbuf;
> -        return;
> -    }
> -
> -    /* maybe we should limit the write_buf stack depth ? */
> -    wbuf = conn->write_buf;
> -    while (wbuf->next)
> -        wbuf = wbuf->next;
> -
> -    wbuf->next = new_wbuf;
> -}
> -
> -/* A helper for udscs_do_read() */
> -static void udscs_read_complete(struct udscs_connection **connp)
> -{
> -    struct udscs_connection *conn = *connp;
> -
> -    debug_print_message_header(conn, &conn->header, "received");
> -
> -    if (conn->read_callback) {
> -        conn->read_callback(connp, &conn->header, conn->data.buf);
> -        if (!*connp) /* Was the connection disconnected by the callback ? */
> -            return;
> -    }

[0] here

> -
> -    g_free(conn->data.buf);
> -    memset(&conn->data, 0, sizeof(conn->data)); /* data.buf = NULL */
> -    conn->header_read = 0;
> +    vdagent_connection_write(conn->conn, buff, buff_size);
>  }
>  
> -static void udscs_do_read(struct udscs_connection **connp)
> -{
> -    ssize_t n;
> -    size_t to_read;
> -    uint8_t *dest;
> -    struct udscs_connection *conn = *connp;
> -
> -    if (conn->header_read < sizeof(conn->header)) {
> -        to_read = sizeof(conn->header) - conn->header_read;
> -        dest = (uint8_t *)&conn->header + conn->header_read;
> -    } else {
> -        to_read = conn->data.size - conn->data.pos;
> -        dest = conn->data.buf + conn->data.pos;
> -    }
> -
> -    n = read(conn->fd, dest, to_read);
> -    if (n < 0) {
> -        if (errno == EINTR)
> -            return;
> -        syslog(LOG_ERR, "reading unix domain socket: %m, disconnecting %p",
> -               conn);
> -    }
> -    if (n <= 0) {
> -        udscs_destroy_connection(connp);
> -        return;
> -    }
> -
> -    if (conn->header_read < sizeof(conn->header)) {
> -        conn->header_read += n;
> -        if (conn->header_read == sizeof(conn->header)) {
> -            if (conn->header.size == 0) {
> -                udscs_read_complete(connp);
> -                return;
> -            }
> -            conn->data.pos = 0;
> -            conn->data.size = conn->header.size;
> -            conn->data.buf = g_malloc(conn->data.size);
> -        }
> -    } else {
> -        conn->data.pos += n;
> -        if (conn->data.pos == conn->data.size)
> -            udscs_read_complete(connp);
> -    }
> -}
> -
> -static void udscs_do_write(struct udscs_connection **connp)
> -{
> -    ssize_t n;
> -    size_t to_write;
> -    struct udscs_connection *conn = *connp;
> -
> -    struct udscs_buf* wbuf = conn->write_buf;
> -    if (!wbuf) {
> -        syslog(LOG_ERR,
> -               "%p do_write called on a connection without a write buf ?!",
> -               conn);
> -        return;
> -    }
> -
> -    to_write = wbuf->size - wbuf->pos;
> -    n = write(conn->fd, wbuf->buf + wbuf->pos, to_write);
> -    if (n < 0) {
> -        if (errno == EINTR)
> -            return;
> -        syslog(LOG_ERR, "writing to unix domain socket: %m, disconnecting %p",
> -               conn);
> -        udscs_destroy_connection(connp);
> -        return;
> -    }
> -
> -    wbuf->pos += n;
> -    if (wbuf->pos == wbuf->size) {
> -        conn->write_buf = wbuf->next;
> -        g_free(wbuf->buf);
> -        g_free(wbuf);
> -    }
> -}
> -
> -static gboolean udscs_io_channel_cb(GIOChannel *source,
> -                                    GIOCondition condition,
> -                                    gpointer data)
> -{
> -    struct udscs_connection *conn = data;
> -
> -    if (condition & G_IO_IN) {
> -        udscs_do_read(&conn);
> -        if (conn == NULL)
> -            return G_SOURCE_REMOVE;
> -        return G_SOURCE_CONTINUE;
> -    }
> -    if (condition & G_IO_OUT) {
> -        udscs_do_write(&conn);
> -        if (conn == NULL)
> -            return G_SOURCE_REMOVE;
> -        if (conn->write_buf)
> -            return G_SOURCE_CONTINUE;
> -        conn->write_watch_id = 0;
> -        return G_SOURCE_REMOVE;
> -    }
> -
> -    udscs_destroy_connection(&conn);
> -    return G_SOURCE_REMOVE;
> -}
> -
> -
>  #ifndef UDSCS_NO_SERVER
>  
>  /* ---------- Server-side implementation ---------- */
>  
>  struct udscs_server {
> -    int fd;
> +    GSocketService *service;
> +
>      int debug;
>      struct udscs_connection connections_head;
>      udscs_connect_callback connect_callback;
> @@ -374,7 +202,12 @@ struct udscs_server {
>      udscs_disconnect_callback disconnect_callback;
>  };
>  
> -struct udscs_server *udscs_create_server_for_fd(int fd,
> +static gboolean udscs_server_accept_cb(GSocketService    *service,
> +                                       GSocketConnection *socket_conn,
> +                                       GObject           *source_object,
> +                                       gpointer           user_data);
> +
> +static struct udscs_server *udscs_server_new(
>      udscs_connect_callback connect_callback,
>      udscs_read_callback read_callback,
>      udscs_disconnect_callback disconnect_callback,
> @@ -382,59 +215,74 @@ struct udscs_server *udscs_create_server_for_fd(int fd,
>  {
>      struct udscs_server *server;
>  
> -    if (fd <= 0) {
> -        syslog(LOG_ERR, "Invalid file descriptor: %i", fd);
> -        return NULL;
> -    }
> -
>      server = g_new0(struct udscs_server, 1);
>      server->debug = debug;
> -    server->fd = fd;
>      server->connect_callback = connect_callback;
>      server->read_callback = read_callback;
>      server->disconnect_callback = disconnect_callback;
> +    server->service = g_socket_service_new();
> +
> +    g_signal_connect(server->service, "incoming",
> +        G_CALLBACK(udscs_server_accept_cb), server);
>  
>      return server;
>  }
>  
> -struct udscs_server *udscs_create_server(const char *socketname,
> +struct udscs_server *udscs_create_server_for_fd(int fd,
>      udscs_connect_callback connect_callback,
>      udscs_read_callback read_callback,
>      udscs_disconnect_callback disconnect_callback,
>      int debug)
>  {
> -    int c;
> -    int fd;
> -    struct sockaddr_un address;
>      struct udscs_server *server;
> +    GSocket *socket;
> +    GError *err = NULL;
>  
> -    fd = socket(PF_UNIX, SOCK_STREAM, 0);
> -    if (fd == -1) {
> -        syslog(LOG_ERR, "creating unix domain socket: %m");
> -        return NULL;
> -    }
> +    server = udscs_server_new(connect_callback, read_callback,
> +                              disconnect_callback, debug);
>  
> -    address.sun_family = AF_UNIX;
> -    snprintf(address.sun_path, sizeof(address.sun_path), "%s", socketname);
> -    c = bind(fd, (struct sockaddr *)&address, sizeof(address));
> -    if (c != 0) {
> -        syslog(LOG_ERR, "bind %s: %m", socketname);
> -        close(fd);
> -        return NULL;
> -    }
> +    socket = g_socket_new_from_fd(fd, &err);
> +    if (err)
> +        goto error;
> +    g_socket_listener_add_socket(G_SOCKET_LISTENER(server->service),
> +                                 socket, NULL, &err);
> +    g_object_unref(socket);
> +    if (err)
> +        goto error;
>  
> -    c = listen(fd, 5);
> -    if (c != 0) {
> -        syslog(LOG_ERR, "listen: %m");
> -        close(fd);
> -        return NULL;
> -    }
> -
> -    server = udscs_create_server_for_fd(fd, connect_callback, read_callback,
> -                                        disconnect_callback, debug);
> +    return server;
> +error:
> +    syslog(LOG_ERR, "%s: %s", __func__, err->message);
> +    g_error_free(err);
> +    udscs_destroy_server(server);
> +    return NULL;
> +}
>  
> -    if (!server) {
> -        close(fd);
> +struct udscs_server *udscs_create_server(const char *socketname,
> +    udscs_connect_callback connect_callback,
> +    udscs_read_callback read_callback,
> +    udscs_disconnect_callback disconnect_callback,
> +    int debug)
> +{
> +    struct udscs_server *server;
> +    GSocketAddress *socket_addr;
> +    GError *err = NULL;
> +
> +    server = udscs_server_new(connect_callback, read_callback,
> +                              disconnect_callback, debug);
> +
> +    socket_addr = g_unix_socket_address_new(socketname);
> +    g_socket_listener_add_address(G_SOCKET_LISTENER(server->service),
> +                                  socket_addr,
> +                                  G_SOCKET_TYPE_STREAM,
> +                                  G_SOCKET_PROTOCOL_DEFAULT,
> +                                  NULL, NULL, &err);
> +    g_object_unref(socket_addr);
> +    if (err) {
> +        syslog(LOG_ERR, "%s: %s", __func__, err->message);
> +        g_error_free(err);
> +        udscs_destroy_server(server);
> +        return NULL;
>      }
>  
>      return server;
> @@ -453,43 +301,51 @@ void udscs_destroy_server(struct udscs_server *server)
>          udscs_destroy_connection(&conn);
>          conn = next_conn;
>      }
> -    close(server->fd);
> +    g_object_unref(server->service);
>      g_free(server);
>  }
>  
>  int udscs_get_peer_pid(struct udscs_connection *conn)
>  {
> -    return (int)conn->peer_cred.pid;
> +    return conn->peer_pid;
>  }
>  
> -static void udscs_server_accept(struct udscs_server *server) {
> +static gboolean udscs_server_accept_cb(GSocketService    *service,
> +                                       GSocketConnection *socket_conn,
> +                                       GObject           *source_object,
> +                                       gpointer           user_data)
> +{
> +    struct udscs_server *server = user_data;
>      struct udscs_connection *new_conn, *conn;
> -    struct sockaddr_un address;
> -    socklen_t length = sizeof(address);
> -    int r, fd;
> -
> -    fd = accept(server->fd, (struct sockaddr *)&address, &length);
> -    if (fd == -1) {
> -        if (errno == EINTR)
> -            return;
> -        syslog(LOG_ERR, "accept: %m");
> -        return;
> -    }
> +    GCredentials *cred;
> +    GError *err = NULL;
>  
>      new_conn = g_new0(struct udscs_connection, 1);
> -    new_conn->fd = fd;
>      new_conn->debug = server->debug;
>      new_conn->read_callback = server->read_callback;
>      new_conn->disconnect_callback = server->disconnect_callback;
>  
> -    length = sizeof(new_conn->peer_cred);
> -    r = getsockopt(fd, SOL_SOCKET, SO_PEERCRED, &new_conn->peer_cred, &length);
> -    if (r != 0) {
> -        syslog(LOG_ERR, "Could not get peercred, disconnecting new client");
> -        close(fd);
> +    g_object_ref(socket_conn);
> +    new_conn->conn = vdagent_connection_new(G_IO_STREAM(socket_conn),
> +                                            FALSE,
> +                                            sizeof(struct udscs_message_header),
> +                                            conn_header_read_cb,
> +                                            conn_read_cb,
> +                                            conn_error_cb,
> +                                            new_conn);
> +
> +
> +    cred = vdagent_connection_get_peer_credentials(new_conn->conn, &err);
> +    if (err) {
> +        syslog(LOG_ERR, "Could not get peer PID, disconnecting new client: %s",
> +                        err->message);
> +        g_error_free(err);
> +        vdagent_connection_destroy(new_conn->conn);
>          g_free(new_conn);
> -        return;
> +        return TRUE;
>      }
> +    new_conn->peer_pid = g_credentials_get_unix_pid(cred, NULL);
> +    g_object_unref(cred);
>  
>      conn = &server->connections_head;
>      while (conn->next)
> @@ -504,59 +360,8 @@ static void udscs_server_accept(struct udscs_server *server) {
>  
>      if (server->connect_callback)
>          server->connect_callback(new_conn);
> -}
> -
> -int udscs_server_fill_fds(struct udscs_server *server, fd_set *readfds,
> -        fd_set *writefds)
> -{
> -    struct udscs_connection *conn;
> -    int nfds;
>  
> -    if (!server)
> -        return -1;
> -
> -    nfds = server->fd + 1;
> -    FD_SET(server->fd, readfds);
> -
> -    conn = server->connections_head.next;
> -    while (conn) {
> -        FD_SET(conn->fd, readfds);
> -        if (conn->write_buf)
> -            FD_SET(conn->fd, writefds);
> -
> -        if (conn->fd >= nfds)
> -            nfds = conn->fd + 1;
> -
> -        conn = conn->next;
> -    }
> -
> -    return nfds;
> -}
> -
> -void udscs_server_handle_fds(struct udscs_server *server, fd_set *readfds,
> -        fd_set *writefds)
> -{
> -    struct udscs_connection *conn, *next_conn;
> -
> -    if (!server)
> -        return;
> -
> -    if (FD_ISSET(server->fd, readfds))
> -        udscs_server_accept(server);
> -
> -    conn = server->connections_head.next;
> -    while (conn) {
> -        /* conn may be destroyed by udscs_do_read() or udscs_do_write()
> -         * (when disconnected), so get the next connection first. */
> -        next_conn = conn->next;
> -
> -        if (FD_ISSET(conn->fd, readfds))
> -            udscs_do_read(&conn);
> -        if (conn && FD_ISSET(conn->fd, writefds))
> -            udscs_do_write(&conn);
> -
> -        conn = next_conn;
> -    }
> +    return TRUE;
>  }
>  
>  void udscs_server_write_all(struct udscs_server *server,
> diff --git a/src/udscs.h b/src/udscs.h
> index 363ca18..1c7fa2b 100644
> --- a/src/udscs.h
> +++ b/src/udscs.h
> @@ -22,9 +22,7 @@
>  #ifndef __UDSCS_H
>  #define __UDSCS_H
>  
> -#include <stdio.h>
>  #include <stdint.h>
> -#include <sys/select.h>
>  #include <sys/socket.h>
>  
>  
> @@ -151,19 +149,6 @@ typedef int (*udscs_for_all_clients_callback)(struct udscs_connection **connp,
>  int udscs_server_for_all_clients(struct udscs_server *server,
>      udscs_for_all_clients_callback func, void *priv);
>  
> -/* Given a udscs server, fill the fd_sets pointed to by readfds and
> - * writefds for select() usage.
> - * Return value: value of the highest fd + 1 or -1 if server is NULL
> - */
> -int udscs_server_fill_fds(struct udscs_server *server, fd_set *readfds,
> -    fd_set *writefds);
> -
> -/* Handle any events flagged by select for the given udscs server.
> - * Does nothing if server is NULL.
> - */
> -void udscs_server_handle_fds(struct udscs_server *server, fd_set *readfds,
> -    fd_set *writefds);
> -
>  /* Returns the peer's PID. */
>  int udscs_get_peer_pid(struct udscs_connection *conn);
>  
> diff --git a/src/vdagent-connection.c b/src/vdagent-connection.c
> new file mode 100644
> index 0000000..e492770
> --- /dev/null
> +++ b/src/vdagent-connection.c
> @@ -0,0 +1,300 @@
> +/*  vdagent-connection.c
> +
> +    Copyright 2018 Red Hat, Inc.
> +
> +    This program is free software: you can redistribute it and/or modify
> +    it under the terms of the GNU General Public License as published by
> +    the Free Software Foundation, either version 3 of the License, or
> +    (at your option) any later version.
> +
> +    This program 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 General Public License for more details.
> +
> +    You should have received a copy of the GNU General Public License
> +    along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +*/
> +
> +#include <syslog.h>
> +#include <fcntl.h>
> +#include <errno.h>
> +#include <glib/gstdio.h>
> +#include <gio/gunixinputstream.h>
> +#include <gio/gunixoutputstream.h>
> +#include <gio/gunixsocketaddress.h>
> +
> +#include "vdagent-connection.h"
> +
> +struct VDAgentConnection {
> +    GObject                 parent_instance;
> +
> +    GIOStream              *io_stream;
> +    gboolean                opening;
> +    GCancellable           *cancellable;
> +
> +    GQueue                 *write_queue;
> +    GMainLoop              *flush_loop;
> +
> +    gsize                   header_size;
> +    gpointer                header_buff;
> +    gpointer                read_buff;

Should be fine to create an array of VD_AGENT_MAX_DATA_SIZE
instead of alloc/free every message.. or alloc together with
header_buff

> +
> +    VDAgentConnHeaderReadCb header_read_cb;
> +    VDAgentConnReadCb       read_cb;
> +    VDAgentConnErrorCb      error_cb;
> +
> +    gpointer                user_data;
> +};
> +
> +G_DEFINE_TYPE(VDAgentConnection, vdagent_connection, G_TYPE_OBJECT);
> +
> +static void write_next_message(VDAgentConnection *conn);
> +static void read_next_message(VDAgentConnection *conn);
> +
> +GIOStream *vdagent_file_open(const gchar *path, GError **err)
> +{
> +    gint fd, errsv;
> +
> +    fd = g_open(path, O_RDWR);
> +    if (fd == -1) {
> +        errsv = errno;
> +        g_set_error_literal(err, G_FILE_ERROR,
> +                            g_file_error_from_errno(errsv),
> +                            g_strerror(errsv));
> +        return NULL;
> +    }
> +
> +    return g_simple_io_stream_new(g_unix_input_stream_new(fd, TRUE),
> +                                  g_unix_output_stream_new(fd, TRUE));
> +}
> +
> +GIOStream *vdagent_socket_connect(const gchar *address, GError **err)
> +{
> +    GSocketConnection *socket_conn;
> +    GSocketClient *client;
> +    GSocketConnectable *connectable;
> +
> +    connectable = G_SOCKET_CONNECTABLE(g_unix_socket_address_new(address));
> +    client = g_object_new(G_TYPE_SOCKET_CLIENT,
> +                          "family", G_SOCKET_FAMILY_UNIX,
> +                          "type", G_SOCKET_TYPE_STREAM,
> +                          NULL);
> +
> +    socket_conn = g_socket_client_connect(client, connectable, NULL, err);
> +    g_object_unref(client);
> +    g_object_unref(connectable);
> +    return G_IO_STREAM(socket_conn);
> +}
> +
> +static void vdagent_connection_init(VDAgentConnection *conn)
> +{
> +    conn->cancellable = g_cancellable_new();
> +    conn->write_queue = g_queue_new();
> +    conn->flush_loop = NULL;
> +    conn->read_buff = NULL;
> +}
> +
> +static void vdagent_connection_dispose(GObject *obj)
> +{
> +    VDAgentConnection *conn = VDAGENT_CONNECTION(obj);
> +    g_clear_object(&conn->cancellable);
> +    g_clear_pointer(&conn->flush_loop, g_main_loop_quit);
> +    g_clear_object(&conn->io_stream);
> +
> +    G_OBJECT_CLASS(vdagent_connection_parent_class)->dispose(obj);
> +}
> +
> +static void vdagent_connection_finalize(GObject *obj)
> +{
> +    VDAgentConnection *conn = VDAGENT_CONNECTION(obj);
> +    g_queue_free_full(conn->write_queue, (GDestroyNotify)g_bytes_unref);
> +    g_free(conn->header_buff);
> +    g_free(conn->read_buff);
> +
> +    G_OBJECT_CLASS(vdagent_connection_parent_class)->finalize(obj);
> +}
> +
> +static void vdagent_connection_class_init(VDAgentConnectionClass *klass)
> +{
> +    GObjectClass *gobject_class = G_OBJECT_CLASS(klass);
> +    gobject_class->dispose  = vdagent_connection_dispose;
> +    gobject_class->finalize = vdagent_connection_finalize;
> +}
> +
> +VDAgentConnection *vdagent_connection_new(
> +    GIOStream              *io_stream,
> +    gboolean                wait_on_opening,
> +    gsize                   header_size,
> +    VDAgentConnHeaderReadCb header_read_cb,
> +    VDAgentConnReadCb       read_cb,
> +    VDAgentConnErrorCb      error_cb,
> +    gpointer                user_data)

Need to change indentation by
https://www.spice-space.org/spice-project-coding-style-and-coding-conventions.html

to
    VDAgentConnection *vdagent_connection_new(GIOStream *io_stream,
                                              gboolean wait_on_opening,
                                              gsize header_size,
                                              VDAgentConnHeaderReadCb header_read_cb,
                                              VDAgentConnReadCb read_cb,
                                              VDAgentConnErrorCb error_cb,
                                              gpointer user_data)


> +{
> +    VDAgentConnection *conn;
> +    conn = g_object_new(VDAGENT_TYPE_CONNECTION, NULL);
> +    conn->io_stream = io_stream;
> +    conn->opening = wait_on_opening;
> +    conn->header_size = header_size;
> +    conn->header_buff = g_malloc(header_size);
> +    conn->header_read_cb = header_read_cb;
> +    conn->read_cb = read_cb;
> +    conn->error_cb = error_cb;
> +    conn->user_data = user_data;
> +
> +    read_next_message(conn);
> +
> +    return conn;
> +}
> +
> +void vdagent_connection_destroy(VDAgentConnection *conn)
> +{
> +    g_cancellable_cancel(conn->cancellable);
> +    g_object_unref(conn);
> +}
> +
> +GCredentials *vdagent_connection_get_peer_credentials(VDAgentConnection *conn,
> +                                                      GError           **err)
> +{
> +    g_return_val_if_fail(G_IS_SOCKET_CONNECTION(conn->io_stream), NULL);
> +
> +    GSocketConnection *socket_conn = G_SOCKET_CONNECTION(conn->io_stream);
> +    return g_socket_get_credentials(
> +               g_socket_connection_get_socket(socket_conn), err);
> +}
> +
> +static void message_write_cb(GObject      *source_object,
> +                             GAsyncResult *res,
> +                             gpointer      user_data)
> +{
> +    VDAgentConnection *conn = user_data;
> +    GOutputStream *out = G_OUTPUT_STREAM(source_object);
> +    GError *err = NULL;
> +
> +    g_output_stream_write_all_finish(out, res, NULL, &err);
> +    g_bytes_unref(g_queue_pop_head(conn->write_queue));
> +
> +    if (err) {
> +        if (!g_error_matches(err, G_IO_ERROR, G_IO_ERROR_CANCELLED))
> +            conn->error_cb(err, conn->user_data);
> +        g_error_free(err);
> +        g_object_unref(conn);
> +        return;
> +    }
> +    g_object_unref(conn);

This should be moved to after write_next_message() otherwise, if
you are holding the last reference you could have a dangling
pointer from here onwards.

Not sure how that could happen here as you already checked for
cancelled operation above... but better be safe than sorry.

> +
> +    conn->opening = FALSE;

I'm surprised to see this on the write() too, but it was in the
previous code as well so it might be needed indeed.

> +
> +    if (g_queue_is_empty(conn->write_queue))
> +        g_clear_pointer(&conn->flush_loop, g_main_loop_quit);
> +    else
> +        write_next_message(conn);

I would say, move the if() check to write_next_message(conn);

> +}
> +
> +static void write_next_message(VDAgentConnection *conn)
> +{
> +    GBytes *msg;
> +    GOutputStream *out;

Might be worth to check if GCancellabe isn't set and, as
mentioned above, moving the check to empty queue + finish flush
loop here.

> +
> +    msg = g_queue_peek_head(conn->write_queue);
> +    out = g_io_stream_get_output_stream(conn->io_stream);
> +
> +    g_output_stream_write_all_async(out,
> +        g_bytes_get_data(msg, NULL), g_bytes_get_size(msg),
> +        G_PRIORITY_DEFAULT, conn->cancellable,
> +        message_write_cb, g_object_ref(conn));
> +}
> +
> +void vdagent_connection_write(VDAgentConnection *conn,
> +                              gpointer           data,
> +                              gsize              size)
> +{
> +    g_queue_push_tail(conn->write_queue, g_bytes_new_take(data, size));
> +
> +    if (g_queue_get_length(conn->write_queue) == 1)
> +        write_next_message(conn);
> +}
> +
> +void vdagent_connection_flush(VDAgentConnection *conn)
> +{
> +    GMainLoop *loop;
> +    /* TODO: allow multiple flush calls at once? */
> +    g_return_if_fail(conn->flush_loop == NULL);

I would just return without critical... not sure if this can
really be a problem?

> +    if (g_queue_is_empty(conn->write_queue))
> +        return;
> +
> +    loop = conn->flush_loop = g_main_loop_new(NULL, FALSE);
> +    /* When using GTK+, this should be wrapped with
> +     * gdk_threads_leave() and gdk_threads_enter(),
> +     * but since flush is used in virtio-port.c only
> +     * let's leave it as it is for now. */
> +    g_main_loop_run(loop);
> +    g_main_loop_unref(loop);
> +}
> +
> +static void message_read_cb(GObject      *source_object,
> +                            GAsyncResult *res,
> +                            gpointer      user_data)
> +{
> +    VDAgentConnection *conn = user_data;
> +    GInputStream *in = G_INPUT_STREAM(source_object);
> +    GError *err = NULL;
> +    gsize bytes_read, data_size;
> +
> +    g_input_stream_read_all_finish(in, res, &bytes_read, &err);
> +    if (err) {
> +        if (!g_error_matches(err, G_IO_ERROR, G_IO_ERROR_CANCELLED))
> +            conn->error_cb(err, conn->user_data);
> +        g_error_free(err);
> +        g_object_unref(conn);
> +        return;
> +    }
> +    g_object_unref(conn);

Same as mentioned on write above, better to move this to the end

> +    if (bytes_read == 0) {
> +        /* see virtio-port.c for the rationale behind this */
> +        if (conn->opening) {
> +            g_usleep(10000);
> +            read_next_message(conn);
> +        } else {
> +            conn->error_cb(NULL, conn->user_data);
> +        }
> +        return;
> +    }
> +    conn->opening = FALSE;
> +
> +    if (conn->read_buff == NULL) {
> +        /* we've read the message header, now let's read its body */
> +        if (conn->header_read_cb(conn->header_buff,
> +                                 &data_size,
> +                                 conn->user_data) == FALSE)

No need to compare with gboolean, just use
!conn->header_read_cb(...);

> +            return;
> +
> +        if (data_size > 0) {
> +            conn->read_buff = g_malloc(data_size);
> +            g_input_stream_read_all_async(in,
> +                conn->read_buff, data_size,
> +                G_PRIORITY_DEFAULT, conn->cancellable,
> +                message_read_cb, g_object_ref(conn));

I would separate this in a second callback...

read_next_message() callback is message_header_cb() and when you
call g_input_stream_read_all_async() here is for the payload so
for message_payload_cb() or message_data_cb().

> +            return;
> +        }
> +    }
> +
> +    if (conn->read_cb(conn->header_buff,
> +                      conn->read_buff,
> +                      conn->user_data) == FALSE)

ditto

> +        return;
> +    g_clear_pointer(&conn->read_buff, g_free);
> +    read_next_message(conn);
> +}
> +
> +static void read_next_message(VDAgentConnection *conn)
> +{
> +    GInputStream *in;
> +    in = g_io_stream_get_input_stream(conn->io_stream);
> +
> +    g_input_stream_read_all_async(in,
> +        conn->header_buff, conn->header_size,
> +        G_PRIORITY_DEFAULT, conn->cancellable,
> +        message_read_cb, g_object_ref(conn));
> +}
> diff --git a/src/vdagent-connection.h b/src/vdagent-connection.h
> new file mode 100644
> index 0000000..fbfc2fb
> --- /dev/null
> +++ b/src/vdagent-connection.h
> @@ -0,0 +1,124 @@
> +/*  vdagent-connection.h
> +
> +    Copyright 2018 Red Hat, Inc.
> +
> +    This program is free software: you can redistribute it and/or modify
> +    it under the terms of the GNU General Public License as published by
> +    the Free Software Foundation, either version 3 of the License, or
> +    (at your option) any later version.
> +
> +    This program 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 General Public License for more details.
> +
> +    You should have received a copy of the GNU General Public License
> +    along with this program.  If not, see <http://www.gnu.org/licenses/>.
> +*/
> +
> +#ifndef __VDAGENT_CONNECTION_H
> +#define __VDAGENT_CONNECTION_H
> +
> +#include <glib.h>
> +#include <gio/gio.h>
> +#include <glib-object.h>
> +
> +G_BEGIN_DECLS
> +
> +#define VDAGENT_TYPE_CONNECTION            (vdagent_connection_get_type())
> +#define VDAGENT_CONNECTION(obj)            (G_TYPE_CHECK_INSTANCE_CAST((obj), VDAGENT_TYPE_CONNECTION, VDAgentConnection))
> +#define VDAGENT_IS_CONNECTION(obj)         (G_TYPE_CHECK_INSTANCE_TYPE((obj), VDAGENT_TYPE_CONNECTION))
> +#define VDAGENT_CONNECTION_CLASS(klass)    (G_TYPE_CHECK_CLASS_CAST((klass), VDAGENT_TYPE_CONNECTION, VDAgentConnectionClass))
> +#define VDAGENT_IS_CONNECTION_CLASS(klass) (G_TYPE_CHECK_CLASS_TYPE((klass), VDAGENT_TYPE_CONNECTION))
> +#define VDAGENT_CONNECTION_GET_CLASS(obj)  (G_TYPE_INSTANCE_GET_CLASS((obj), VDAGENT_TYPE_CONNECTION, VDAgentConnectionClass))
> +
> +typedef struct VDAgentConnection      VDAgentConnection;
> +typedef struct VDAgentConnectionClass VDAgentConnectionClass;
> +
> +struct VDAgentConnectionClass {
> +    GObjectClass parent_class;
> +};
> +
> +GType vdagent_connection_get_type(void);
> +
> +/* Called when a message header has been read.
> + *
> + * If the handler wishes to continue reading,
> + * it must set @body_size to the size of message's body and return TRUE.
> + * Once @body_size bytes are read, VDAgentConnReadCb() is invoked.
> + *
> + * Otherwise the handler should return FALSE
> + * and call vdagent_connection_destroy().
> + *
> + * @header_buff is owned by VDAgentConnection and must not be freed. */
> +typedef gboolean (*VDAgentConnHeaderReadCb)(gpointer header_buff,
> +                                            gsize   *body_size,
> +                                            gpointer user_data);
> +
> +/* Called when a full message has been read.
> + *
> + * If the handler wished to continue reading, it must return TRUE,
> + * otherwise FALSE and call vdagent_connection_destroy().
> + *
> + * @header, @data are owned by VDAgentConnection and must not be freed. */
> +typedef gboolean (*VDAgentConnReadCb)(gpointer header,
> +                                      gpointer data,
> +                                      gpointer user_data);
> +
> +/* Called when an error occured during read or write.
> + * If @err is NULL, the connection was closed by the remote side.
> + * The handler is expected to call vdagent_connection_destroy(). */
> +typedef void (*VDAgentConnErrorCb)(GError *err, gpointer user_data);
> +
> +/* Open a file in @path for read and write.
> + * Returns a new GIOStream to the given file or NULL when @err is set. */
> +GIOStream *vdagent_file_open(const gchar *path, GError **err);
> +
> +/* Create a socket and initiate a new connection to the socket on @address.
> + * Returns a new GIOStream or NULL when @err is set. */
> +GIOStream *vdagent_socket_connect(const gchar *address, GError **err);
> +
> +/* Create new VDAgentConnection and start reading incoming messages.
> + *
> + * If @wait_on_opening is set to TRUE, EOF won't be treated as an error
> + * until the first message is successfully read or written to the @io_stream.
> + *
> + * @user_data will be passed to the supplied callbacks. */
> +VDAgentConnection *vdagent_connection_new(
> +    GIOStream              *io_stream,
> +    gboolean                wait_on_opening,
> +    gsize                   header_size,
> +    VDAgentConnHeaderReadCb header_read_cb,
> +    VDAgentConnReadCb       read_cb,
> +    VDAgentConnErrorCb      error_cb,
> +    gpointer                user_data);
> +
> +/* Free up all resources associated with the VDAgentConnection.
> + *
> + * This operation can be asynchronous. */
> +void vdagent_connection_destroy(VDAgentConnection *conn);
> +
> +/* Append a message to the write queue.
> + *
> + * VDAgentConnection takes ownership of the @data
> + * and frees it once the message is flushed. */
> +void vdagent_connection_write(VDAgentConnection *conn,
> +                              gpointer           data,
> +                              gsize              size);
> +
> +/* Waits until all queued messages get written to the output stream.
> + *
> + * Note: other GSources can be triggered during this call */
> +void vdagent_connection_flush(VDAgentConnection *conn);
> +
> +/* Returns the credentials of the foreign process connected to the socket.
> + * The returned object must be freed using g_object_unref().
> + *
> + * It is an error to call this function with a VDAgentConnection
> + * that isn't based on a GIOStream of G_TYPE_SOCKET_CONNECTION. */
> +GCredentials *vdagent_connection_get_peer_credentials(VDAgentConnection *conn,
> +                                                      GError           **err);
> +
> +G_END_DECLS
> +
> +#endif
> diff --git a/src/vdagent/vdagent.c b/src/vdagent/vdagent.c
> index f7c8b72..d7e2aca 100644
> --- a/src/vdagent/vdagent.c
> +++ b/src/vdagent/vdagent.c
> @@ -471,6 +471,9 @@ reconnect:
>      vdagent_destroy(agent);
>      agent = NULL;
>  
> +    /* allow the VDAgentConnection to close and finalize properly */
> +    g_main_context_iteration(NULL, FALSE);
> +
>      if (!quit && do_daemonize)
>          goto reconnect;
>  
> diff --git a/src/vdagentd/vdagentd.c b/src/vdagentd/vdagentd.c
> index 99683da..f52f039 100644
> --- a/src/vdagentd/vdagentd.c
> +++ b/src/vdagentd/vdagentd.c
> @@ -31,10 +31,9 @@
>  #include <errno.h>
>  #include <signal.h>
>  #include <syslog.h>
> -#include <sys/select.h>
>  #include <sys/stat.h>
>  #include <spice/vd_agent.h>
> -#include <glib.h>
> +#include <glib-unix.h>
>  
>  #ifdef WITH_SYSTEMD_SOCKET_ACTIVATION
>  #include <systemd/sd-daemon.h>
> @@ -81,11 +80,18 @@ static const char *active_session = NULL;
>  static unsigned int session_count = 0;
>  static struct udscs_connection *active_session_conn = NULL;
>  static int agent_owns_clipboard[256] = { 0, };
> -static int quit = 0;
>  static int retval = 0;
>  static int client_connected = 0;
>  static int max_clipboard = -1;
>  
> +static GMainLoop *loop;
> +
> +static void vdagentd_quit(gint exit_code)
> +{
> +    retval = exit_code;
> +    g_main_loop_quit(loop);
> +}
> +
>  /* utility functions */
>  static void virtio_msg_uint32_to_le(uint8_t *_msg, uint32_t size, uint32_t offset)
>  {
> @@ -168,8 +174,7 @@ void do_client_mouse(struct vdagentd_uinput **uinputp, VDAgentMouseState *mouse)
>                                                uinput_fake);
>          if (!*uinputp) {
>              syslog(LOG_CRIT, "Fatal uinput error");
> -            retval = 1;
> -            quit = 1;
> +            vdagentd_quit(1);
>          }
>      }
>  }
> @@ -510,6 +515,11 @@ static int virtio_port_read_complete(
>          VDAgentMessage *message_header,
>          uint8_t *data)
>  {
> +    /* This callback could be invoked during vdagent_virtio_port_flush(),
> +     * don't process any incoming messages when quitting. */
> +    if (!g_main_loop_is_running(loop))
> +        return 0;

I missed on how this can happen (the callback being called)

>
>      if (!vdagent_message_check_size(message_header))
>          return 0;
>  
> @@ -565,6 +575,27 @@ static int virtio_port_read_complete(
>      return 0;
>  }
>  
> +static void virtio_port_disconnect_cb(struct vdagent_virtio_port *vport,
> +                                      GError *err)
> +{
> +    if (err == NULL)
> +        return;
> +
> +    gboolean old_client_connected = client_connected;
> +    syslog(LOG_CRIT, "AIIEEE lost spice client connection, reconnecting: %s",
> +                     err->message);
> +    virtio_port = vdagent_virtio_port_create(portdev,
> +                                             virtio_port_read_complete,
> +                                             virtio_port_disconnect_cb);
> +    if (virtio_port == NULL) {
> +        syslog(LOG_CRIT, "Fatal error opening vdagent virtio channel");
> +        vdagentd_quit(1);
> +        return;
> +    }
> +    do_client_disconnect();
> +    client_connected = old_client_connected;
> +}
> +
>  static void virtio_write_clipboard(uint8_t selection, uint32_t msg_type,
>      uint32_t data_type, uint8_t *data, uint32_t data_size)
>  {
> @@ -703,8 +734,7 @@ static void check_xorg_resolution(void)
>                                          agent_data->screen_count);
>          if (!uinput) {
>              syslog(LOG_CRIT, "Fatal uinput error");
> -            retval = 1;
> -            quit = 1;
> +            vdagentd_quit(1);
>              return;
>          }
>  
> @@ -712,11 +742,10 @@ static void check_xorg_resolution(void)
>              syslog(LOG_INFO, "opening vdagent virtio channel");
>              virtio_port = vdagent_virtio_port_create(portdev,
>                                                       virtio_port_read_complete,
> -                                                     NULL);
> +                                                     virtio_port_disconnect_cb);
>              if (!virtio_port) {
>                  syslog(LOG_CRIT, "Fatal error opening vdagent virtio channel");
> -                retval = 1;
> -                quit = 1;
> +                vdagentd_quit(1);
>                  return;
>              }
>              send_capabilities(virtio_port, 1);
> @@ -726,6 +755,11 @@ static void check_xorg_resolution(void)
>          vdagentd_uinput_destroy(&uinput);
>  #endif
>          if (virtio_port) {
> +            if (only_once) {
> +                syslog(LOG_INFO, "Exiting after one client session.");
> +                vdagentd_quit(0);
> +                return;
> +            }
>              vdagent_virtio_port_flush(&virtio_port);
>              vdagent_virtio_port_destroy(&virtio_port);
>              syslog(LOG_INFO, "closed vdagent virtio channel");
> @@ -939,6 +973,15 @@ static void agent_read_complete(struct udscs_connection **connp,
>      }
>  }
>  
> +static gboolean si_io_channel_cb(GIOChannel  *source,
> +                                 GIOCondition condition,
> +                                 gpointer     data)
> +{
> +    active_session = session_info_get_active_session(session_info);
> +    update_active_session_connection(NULL);
> +    return G_SOURCE_CONTINUE;
> +}
> +
>  /* main */
>  
>  static void daemonize(void)
> @@ -967,76 +1010,10 @@ static void daemonize(void)
>      }
>  }
>  
> -static void main_loop(void)
> -{
> -    fd_set readfds, writefds;
> -    int n, nfds;
> -    int ck_fd = 0;
> -    int once = 0;
> -
> -    while (!quit) {
> -        FD_ZERO(&readfds);
> -        FD_ZERO(&writefds);
> -
> -        nfds = udscs_server_fill_fds(server, &readfds, &writefds);
> -        n = vdagent_virtio_port_fill_fds(virtio_port, &readfds, &writefds);
> -        if (n >= nfds)
> -            nfds = n + 1;
> -
> -        if (session_info) {
> -            ck_fd = session_info_get_fd(session_info);
> -            FD_SET(ck_fd, &readfds);
> -            if (ck_fd >= nfds)
> -                nfds = ck_fd + 1;
> -        }
> -
> -        n = select(nfds, &readfds, &writefds, NULL, NULL);
> -        if (n == -1) {
> -            if (errno == EINTR)
> -                continue;
> -            syslog(LOG_CRIT, "Fatal error select: %m");
> -            retval = 1;
> -            break;
> -        }
> -
> -        udscs_server_handle_fds(server, &readfds, &writefds);
> -
> -        if (virtio_port) {
> -            once = 1;
> -            vdagent_virtio_port_handle_fds(&virtio_port, &readfds, &writefds);
> -            if (!virtio_port) {
> -                int old_client_connected = client_connected;
> -                syslog(LOG_CRIT,
> -                       "AIIEEE lost spice client connection, reconnecting");
> -                virtio_port = vdagent_virtio_port_create(portdev,
> -                                                     virtio_port_read_complete,
> -                                                     NULL);
> -                if (!virtio_port) {
> -                    syslog(LOG_CRIT,
> -                           "Fatal error opening vdagent virtio channel");
> -                    retval = 1;
> -                    break;
> -                }
> -                do_client_disconnect();
> -                client_connected = old_client_connected;
> -            }
> -        }
> -        else if (only_once && once)
> -        {
> -            syslog(LOG_INFO, "Exiting after one client session.");
> -            break;
> -        }
> -
> -        if (session_info && FD_ISSET(ck_fd, &readfds)) {
> -            active_session = session_info_get_active_session(session_info);
> -            update_active_session_connection(NULL);
> -        }
> -    }
> -}
> -
> -static void quit_handler(int sig)
> +static gboolean signal_handler(gpointer user_data)
>  {
> -    quit = 1;
> +    vdagentd_quit(0);
> +    return G_SOURCE_REMOVE;
>  }
>  
>  static gboolean parse_debug_level_cb(const gchar *option_name,
> @@ -1090,8 +1067,8 @@ int main(int argc, char *argv[])
>  {
>      GOptionContext *context;
>      GError *err = NULL;
> -    struct sigaction act;
>      gboolean own_socket = TRUE;
> +    GIOChannel *si_io_channel = NULL;
>  
>      context = g_option_context_new(NULL);
>      g_option_context_add_main_entries(context, cmd_entries, NULL);
> @@ -1116,13 +1093,9 @@ int main(int argc, char *argv[])
>          uinput_device = g_strdup(DEFAULT_UINPUT_DEVICE);
>      }
>  
> -    memset(&act, 0, sizeof(act));
> -    act.sa_flags = SA_RESTART;
> -    act.sa_handler = quit_handler;
> -    sigaction(SIGINT, &act, NULL);
> -    sigaction(SIGHUP, &act, NULL);
> -    sigaction(SIGTERM, &act, NULL);
> -    sigaction(SIGQUIT, &act, NULL);
> +    g_unix_signal_add(SIGINT, signal_handler, NULL);
> +    g_unix_signal_add(SIGHUP, signal_handler, NULL);
> +    g_unix_signal_add(SIGTERM, signal_handler, NULL);
>  
>      openlog("spice-vdagentd", do_daemonize ? 0 : LOG_PERROR, LOG_USER);
>  
> @@ -1154,7 +1127,7 @@ int main(int argc, char *argv[])
>              syslog(LOG_CRIT, "Fatal the server socket %s exists already. Delete it?",
>                     vdagentd_socket);
>          } else {
> -            syslog(LOG_CRIT, "Fatal could not create the server socket %s: %m",
> +            syslog(LOG_CRIT, "Fatal could not create the server socket %s",
>                     vdagentd_socket);
>          }
>          return 1;
> @@ -1184,19 +1157,31 @@ int main(int argc, char *argv[])
>  
>      if (want_session_info)
>          session_info = session_info_create(debug);
> -    if (!session_info)
> +    if (session_info) {
> +        si_io_channel = g_io_channel_unix_new(
> +                            session_info_get_fd(session_info));
> +        g_io_add_watch(si_io_channel, G_IO_IN, si_io_channel_cb, NULL);
> +    } else
>          syslog(LOG_WARNING, "no session info, max 1 session agent allowed");
>  
>      active_xfers = g_hash_table_new(g_direct_hash, g_direct_equal);
> -    main_loop();
> +
> +    loop = g_main_loop_new(NULL, FALSE);
> +    g_main_loop_run(loop);
>  
>      release_clipboards();
>  
>      vdagentd_uinput_destroy(&uinput);
> +    g_clear_pointer(&si_io_channel, g_io_channel_unref);
> +    g_clear_pointer(&session_info, session_info_destroy);
> +    g_clear_pointer(&server, udscs_destroy_server);
>      vdagent_virtio_port_flush(&virtio_port);
>      vdagent_virtio_port_destroy(&virtio_port);
> -    session_info_destroy(session_info);
> -    udscs_destroy_server(server);
> +
> +    /* allow the VDAgentConnection(s) to close and finalize properly */
> +    g_main_context_iteration(NULL, FALSE);
> +
> +    g_main_loop_unref(loop);
>  
>      /* leave the socket around if it was provided by systemd */
>      if (own_socket) {
> diff --git a/src/vdagentd/virtio-port.c b/src/vdagentd/virtio-port.c
> index 497811e..5e65a7f 100644
> --- a/src/vdagentd/virtio-port.c
> +++ b/src/vdagentd/virtio-port.c
> @@ -19,28 +19,20 @@
>      along with this program.  If not, see <http://www.gnu.org/licenses/>.
>  */
>  
> -#include <errno.h>
>  #include <stdlib.h>
>  #include <string.h>
>  #include <syslog.h>
> -#include <unistd.h>
> -#include <fcntl.h>
> -#include <sys/select.h>
> -#include <sys/socket.h>
> -#include <sys/un.h>
> -#include <glib.h>
>  #include <gio/gio.h>
> +#include <glib-unix.h>
>  
> +#include "vdagent-connection.h"
>  #include "virtio-port.h"
>  
>  
>  struct vdagent_virtio_port_buf {
>      uint8_t *buf;
> -    size_t pos;
>      size_t size;
>      size_t write_pos;
> -
> -    struct vdagent_virtio_port_buf *next;
>  };
>  
>  /* Data to keep track of the assembling of vdagent messages per chunk port,
> @@ -53,78 +45,126 @@ struct vdagent_virtio_port_chunk_port_data {
>  };
>  
>  struct vdagent_virtio_port {
> -    int fd;
> -    int opening;
> -    int is_uds;
> -
> -    /* Chunk read stuff, single buffer, separate header and data buffer */
> -    int chunk_header_read;
> -    int chunk_data_pos;
> -    VDIChunkHeader chunk_header;
> -    uint8_t chunk_data[VD_AGENT_MAX_DATA_SIZE];
> +    VDAgentConnection *conn;
>  
>      /* Per chunk port data */
>      struct vdagent_virtio_port_chunk_port_data port_data[VDP_END_PORT];
>  
> -    /* Writes are stored in a linked list of buffers, with both the header
> -       + data for a single message in 1 buffer. */
> -    struct vdagent_virtio_port_buf *write_buf;
> +    struct vdagent_virtio_port_buf write_buf;
>  
>      /* Callbacks */
>      vdagent_virtio_port_read_callback read_callback;
>      vdagent_virtio_port_disconnect_callback disconnect_callback;
>  };
>  
> -static void vdagent_virtio_port_do_write(struct vdagent_virtio_port **vportp);
> -static void vdagent_virtio_port_do_read(struct vdagent_virtio_port **vportp);
> +static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp,
> +                                         VDIChunkHeader *chunk_header,
> +                                         gconstpointer chunk_data);
> +
> +static void virtio_port_destroy(struct vdagent_virtio_port **vportp,
> +                                GError *err);
> +
> +static gboolean conn_header_read_cb(gpointer header_buff,
> +                                    gsize   *body_size,
> +                                    gpointer user_data)
> +{

> +    struct vdagent_virtio_port *vport = user_data;
> +    VDIChunkHeader *header = header_buff;
> +    GError *err;
> +
> +    header->size = GUINT32_FROM_LE(header->size);
> +    header->port = GUINT32_FROM_LE(header->port);
> +
> +    if (header->size > VD_AGENT_MAX_DATA_SIZE) {
> +        err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> +                          "chunk size %u too large", header->size);
> +        virtio_port_destroy(&vport, err);
> +        return FALSE;
> +    }
> +    if (header->port >= VDP_END_PORT) {
> +        err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> +                          "chunk port %u out of range", header->port);
> +        virtio_port_destroy(&vport, err);
> +        return FALSE;
> +    }
> +
> +    *body_size = header->size;
> +    return TRUE;

I would say it is better to return gsize instead of using
pointer?

> +}
> +
> +static gboolean conn_read_cb(gpointer header,
> +                             gpointer data,
> +                             gpointer user_data)
> +{
> +    struct vdagent_virtio_port *vport = user_data;
> +    vdagent_virtio_port_do_chunk(&vport, header, data);
> +    return vport != NULL;
> +}
> +
> +static void conn_error_cb(GError *err, gpointer user_data)
> +{
> +    struct vdagent_virtio_port *vport = user_data;
> +    virtio_port_destroy(&vport, err ? g_error_copy(err) : NULL);
> +}
>  
>  struct vdagent_virtio_port *vdagent_virtio_port_create(const char *portname,
>      vdagent_virtio_port_read_callback read_callback,
>      vdagent_virtio_port_disconnect_callback disconnect_callback)
>  {
>      struct vdagent_virtio_port *vport;
> -    struct sockaddr_un address;
> -    int c;
> -
> -    vport = g_new0(struct vdagent_virtio_port, 1);
> -
> -    vport->fd = open(portname, O_RDWR);
> -    if (vport->fd == -1) {
> -        vport->fd = socket(PF_UNIX, SOCK_STREAM, 0);
> -        if (vport->fd == -1) {
> -            goto error;
> -        }
> -        address.sun_family = AF_UNIX;
> -        snprintf(address.sun_path, sizeof(address.sun_path), "%s", portname);
> -        c = connect(vport->fd, (struct sockaddr *)&address, sizeof(address));
> -        if (c == 0) {
> -            vport->is_uds = 1;
> -        } else {
> -            goto error;
> +    GIOStream *io_stream;
> +    GError *err = NULL;
> +
> +    io_stream = vdagent_file_open(portname, &err);
> +    if (err) {
> +        syslog(LOG_ERR, "%s: %s", __func__, err->message);
> +        g_clear_error(&err);
> +        io_stream = vdagent_socket_connect(portname, &err);
> +        if (err) {
> +            syslog(LOG_ERR, "%s: %s", __func__, err->message);
> +            g_error_free(err);
> +            return NULL;
>          }
> -    } else {
> -        vport->is_uds = 0;
>      }
> -    vport->opening = 1;
>  
> +    vport = g_new0(struct vdagent_virtio_port, 1);
> +
> +    /* When calling vdagent_connection_new(),
> +     * @wait_on_opening MUST be set to TRUE:
> +     *
> +     * When we open the virtio serial port, the following happens:
> +     * 1) The linux kernel virtio_console driver sends a
> +     *    VIRTIO_CONSOLE_PORT_OPEN message to qemu
> +     * 2) qemu's spicevmc chardev driver calls qemu_spice_add_interface to
> +     *    register the agent chardev with the spice-server
> +     * 3) spice-server then calls the spicevmc chardev driver's state
> +     *    callback to let it know it is ready to receive data
> +     * 4) The state callback sends a CHR_EVENT_OPENED to the virtio-console
> +     *    chardev backend
> +     * 5) The virtio-console chardev backend sends VIRTIO_CONSOLE_PORT_OPEN
> +     *    to the linux kernel virtio_console driver
> +     *
> +     * Until steps 1 - 5 have completed the linux kernel virtio_console
> +     * driver sees the virtio serial port as being in a disconnected state
> +     * and read will return 0 ! So if we blindly assume that a read 0 means
> +     * that the channel is closed we will hit a race here.
> +     */
> +    vport->conn = vdagent_connection_new(io_stream,
> +                                         TRUE,
> +                                         sizeof(VDIChunkHeader),
> +                                         conn_header_read_cb,
> +                                         conn_read_cb,
> +                                         conn_error_cb,
> +                                         vport);
>      vport->read_callback = read_callback;
>      vport->disconnect_callback = disconnect_callback;
>  
>      return vport;
> -
> -error:
> -    syslog(LOG_ERR, "open %s: %m", portname);
> -    if (vport->fd != -1) {
> -        close(vport->fd);
> -    }
> -    g_free(vport);
> -    return NULL;
>  }
>  
>  static void virtio_port_destroy(struct vdagent_virtio_port **vportp,
>                                  GError *err)
>  {
> -    struct vdagent_virtio_port_buf *wbuf, *next_wbuf;
>      struct vdagent_virtio_port *vport = *vportp;
>      int i;
>  
> @@ -136,19 +176,13 @@ static void virtio_port_destroy(struct vdagent_virtio_port **vportp,
>  
>      g_clear_error(&err);
>  
> -    wbuf = vport->write_buf;
> -    while (wbuf) {
> -        next_wbuf = wbuf->next;
> -        g_free(wbuf->buf);
> -        g_free(wbuf);
> -        wbuf = next_wbuf;
> -    }
> +    g_free(vport->write_buf.buf);
>  
>      for (i = 0; i < VDP_END_PORT; i++) {
>          g_free(vport->port_data[i].message_data);
>      }
>  
> -    close(vport->fd);
> +    vdagent_connection_destroy(vport->conn);
>      g_clear_pointer(vportp, g_free);
>  }
>  
> @@ -157,47 +191,6 @@ void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp)
>      virtio_port_destroy(vportp, NULL);
>  }
>  
> -int vdagent_virtio_port_fill_fds(struct vdagent_virtio_port *vport,
> -        fd_set *readfds, fd_set *writefds)
> -{
> -    if (!vport)
> -        return -1;
> -
> -    FD_SET(vport->fd, readfds);
> -    if (vport->write_buf)
> -        FD_SET(vport->fd, writefds);
> -
> -    return vport->fd + 1;
> -}
> -
> -void vdagent_virtio_port_handle_fds(struct vdagent_virtio_port **vportp,
> -        fd_set *readfds, fd_set *writefds)
> -{
> -    if (!*vportp)
> -        return;
> -
> -    if (FD_ISSET((*vportp)->fd, readfds))
> -        vdagent_virtio_port_do_read(vportp);
> -
> -    if (*vportp && FD_ISSET((*vportp)->fd, writefds))
> -        vdagent_virtio_port_do_write(vportp);
> -}
> -
> -static struct vdagent_virtio_port_buf* vdagent_virtio_port_get_last_wbuf(
> -    struct vdagent_virtio_port *vport)
> -{
> -    struct vdagent_virtio_port_buf *wbuf;
> -
> -    wbuf = vport->write_buf;
> -    if (!wbuf)
> -        return NULL;
> -
> -    while (wbuf->next)
> -        wbuf = wbuf->next;
> -
> -    return wbuf;
> -}
> -
>  void vdagent_virtio_port_write_start(
>          struct vdagent_virtio_port *vport,
>          uint32_t port_nr,
> @@ -205,15 +198,15 @@ void vdagent_virtio_port_write_start(
>          uint32_t message_opaque,
>          uint32_t data_size)
>  {
> -    struct vdagent_virtio_port_buf *wbuf, *new_wbuf;
> +    struct vdagent_virtio_port_buf *new_wbuf;
>      VDIChunkHeader chunk_header;
>      VDAgentMessage message_header;
>  
> -    new_wbuf = g_new(struct vdagent_virtio_port_buf, 1);
> -    new_wbuf->pos = 0;
> +    g_return_if_fail(vport->write_buf.buf == NULL);
> +
> +    new_wbuf = &vport->write_buf;
>      new_wbuf->write_pos = 0;
>      new_wbuf->size = sizeof(chunk_header) + sizeof(message_header) + data_size;
> -    new_wbuf->next = NULL;
>      new_wbuf->buf = g_malloc(new_wbuf->size);
>  
>      chunk_header.port = GUINT32_TO_LE(port_nr);
> @@ -229,14 +222,6 @@ void vdagent_virtio_port_write_start(
>      memcpy(new_wbuf->buf + new_wbuf->write_pos, &message_header,
>             sizeof(message_header));
>      new_wbuf->write_pos += sizeof(message_header);
> -
> -    if (!vport->write_buf) {
> -        vport->write_buf = new_wbuf;
> -        return;
> -    }
> -
> -    wbuf = vdagent_virtio_port_get_last_wbuf(vport);
> -    wbuf->next = new_wbuf;
>  }
>  
>  int vdagent_virtio_port_write_append(struct vdagent_virtio_port *vport,
> @@ -244,8 +229,11 @@ int vdagent_virtio_port_write_append(struct vdagent_virtio_port *vport,
>  {
>      struct vdagent_virtio_port_buf *wbuf;
>  
> -    wbuf = vdagent_virtio_port_get_last_wbuf(vport);
> -    if (!wbuf) {
> +    if (size == 0)
> +        return 0;
> +
> +    wbuf = &vport->write_buf;
> +    if (!wbuf->buf) {
>          syslog(LOG_ERR, "can't append without a buffer");
>          return -1;
>      }
> @@ -257,6 +245,11 @@ int vdagent_virtio_port_write_append(struct vdagent_virtio_port *vport,
>  
>      memcpy(wbuf->buf + wbuf->write_pos, data, size);
>      wbuf->write_pos += size;
> +
> +    if (wbuf->write_pos == wbuf->size) {
> +        vdagent_connection_write(vport->conn, wbuf->buf, wbuf->size);
> +        wbuf->buf = NULL;
> +    }

There is a single user of vdagent_virtio_port_write_append,
related to clipboard... We can likely remove this soonish
afterwards.

>      return 0;
>  }
>  
> @@ -275,8 +268,8 @@ void vdagent_virtio_port_write(
>  
>  void vdagent_virtio_port_flush(struct vdagent_virtio_port **vportp)
>  {
> -    while (*vportp && (*vportp)->write_buf)
> -        vdagent_virtio_port_do_write(vportp);
> +    if (*vportp)
> +        vdagent_connection_flush((*vportp)->conn);
>  }
>  
>  void vdagent_virtio_port_reset(struct vdagent_virtio_port *vport, int port)
> @@ -289,20 +282,22 @@ void vdagent_virtio_port_reset(struct vdagent_virtio_port *vport, int port)
>      memset(&vport->port_data[port], 0, sizeof(vport->port_data[0]));
>  }
>  
> -static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp)
> +static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp,
> +                                         VDIChunkHeader *chunk_header,
> +                                         gconstpointer chunk_data)
>  {
>      int avail, read, pos = 0;
>      struct vdagent_virtio_port *vport = *vportp;
>      struct vdagent_virtio_port_chunk_port_data *port =
> -        &vport->port_data[vport->chunk_header.port];
> +        &vport->port_data[chunk_header->port];
>  
>      if (port->message_header_read < sizeof(port->message_header)) {
>          read = sizeof(port->message_header) - port->message_header_read;
> -        if (read > vport->chunk_header.size) {
> -            read = vport->chunk_header.size;
> +        if (read > chunk_header->size) {
> +            read = chunk_header->size;
>          }
>          memcpy((uint8_t *)&port->message_header + port->message_header_read,
> -               vport->chunk_data, read);
> +               chunk_data, read);
>          port->message_header_read += read;
>          if (port->message_header_read == sizeof(port->message_header)) {
>  
> @@ -320,7 +315,7 @@ static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp)
>  
>      if (port->message_header_read == sizeof(port->message_header)) {
>          read  = port->message_header.size - port->message_data_pos;
> -        avail = vport->chunk_header.size - pos;
> +        avail = chunk_header->size - pos;
>  
>          if (avail > read) {
>              GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> @@ -334,13 +329,13 @@ static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp)
>  
>          if (read) {
>              memcpy(port->message_data + port->message_data_pos,
> -                   vport->chunk_data + pos, read);
> +                   chunk_data + pos, read);
>              port->message_data_pos += read;
>          }
>  
>          if (port->message_data_pos == port->message_header.size) {
>              if (vport->read_callback) {
> -                int r = vport->read_callback(vport, vport->chunk_header.port,
> +                int r = vport->read_callback(vport, chunk_header->port,
>                                   &port->message_header, port->message_data);
>                  if (r == -1) {
>                      virtio_port_destroy(vportp, NULL);
> @@ -353,143 +348,3 @@ static void vdagent_virtio_port_do_chunk(struct vdagent_virtio_port **vportp)
>          }
>      }
>  }
> -
> -static int vport_read(struct vdagent_virtio_port *vport, uint8_t *buf, int len)
> -{
> -    if (vport->is_uds) {
> -        return recv(vport->fd, buf, len, 0);
> -    } else {
> -        return read(vport->fd, buf, len);
> -    }
> -}
> -
> -static void vdagent_virtio_port_do_read(struct vdagent_virtio_port **vportp)
> -{
> -    ssize_t n;
> -    size_t to_read;
> -    uint8_t *dest;
> -    struct vdagent_virtio_port *vport = *vportp;
> -
> -    if (vport->chunk_header_read < sizeof(vport->chunk_header)) {
> -        to_read = sizeof(vport->chunk_header) - vport->chunk_header_read;
> -        dest = (uint8_t *)&vport->chunk_header + vport->chunk_header_read;
> -    } else {
> -        to_read = vport->chunk_header.size - vport->chunk_data_pos;
> -        dest = vport->chunk_data + vport->chunk_data_pos;
> -    }
> -
> -    n = vport_read(vport, dest, to_read);
> -    if (n < 0) {
> -        if (errno == EINTR)
> -            return;
> -    }
> -    if (n == 0 && vport->opening) {
> -        /* When we open the virtio serial port, the following happens:
> -           1) The linux kernel virtio_console driver sends a
> -              VIRTIO_CONSOLE_PORT_OPEN message to qemu
> -           2) qemu's spicevmc chardev driver calls qemu_spice_add_interface to
> -              register the agent chardev with the spice-server
> -           3) spice-server then calls the spicevmc chardev driver's state
> -              callback to let it know it is ready to receive data
> -           4) The state callback sends a CHR_EVENT_OPENED to the virtio-console
> -              chardev backend
> -           5) The virtio-console chardev backend sends VIRTIO_CONSOLE_PORT_OPEN
> -              to the linux kernel virtio_console driver
> -
> -           Until steps 1 - 5 have completed the linux kernel virtio_console
> -           driver sees the virtio serial port as being in a disconnected state
> -           and read will return 0 ! So if we blindly assume that a read 0 means
> -           that the channel is closed we will hit a race here.
> -
> -           Therefore we ignore read returning 0 until we've successfully read
> -           or written some data. If we hit this race we also sleep a bit here
> -           to avoid busy waiting until the above steps complete */
> -        usleep(10000);
> -        return;
> -    }
> -    if (n <= 0) {
> -        GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> -                                  "reading from vdagent virtio port: %m");
> -        virtio_port_destroy(vportp, err);
> -        return;
> -    }
> -    vport->opening = 0;
> -
> -    if (vport->chunk_header_read < sizeof(vport->chunk_header)) {
> -        vport->chunk_header_read += n;
> -        if (vport->chunk_header_read == sizeof(vport->chunk_header)) {
> -            vport->chunk_header.size = GUINT32_FROM_LE(vport->chunk_header.size);
> -            vport->chunk_header.port = GUINT32_FROM_LE(vport->chunk_header.port);
> -            if (vport->chunk_header.size > VD_AGENT_MAX_DATA_SIZE) {
> -                GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> -                                          "chunk size %u too large",
> -                                          vport->chunk_header.size);
> -                virtio_port_destroy(vportp, err);
> -                return;
> -            }
> -            if (vport->chunk_header.port >= VDP_END_PORT) {
> -                GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> -                                          "chunk port %u out of range",
> -                                          vport->chunk_header.port);
> -                virtio_port_destroy(vportp, err);
> -                return;
> -            }
> -        }
> -    } else {
> -        vport->chunk_data_pos += n;
> -        if (vport->chunk_data_pos == vport->chunk_header.size) {
> -            vdagent_virtio_port_do_chunk(vportp);
> -            if (!*vportp)
> -                return;
> -            vport->chunk_header_read = 0;
> -            vport->chunk_data_pos = 0;
> -        }
> -    }
> -}
> -
> -static int vport_write(struct vdagent_virtio_port *vport, uint8_t *buf, int len)
> -{
> -    if (vport->is_uds) {
> -        return send(vport->fd, buf, len, 0);
> -    } else {
> -        return write(vport->fd, buf, len);
> -    }
> -}
> -
> -static void vdagent_virtio_port_do_write(struct vdagent_virtio_port **vportp)
> -{
> -    ssize_t n;
> -    size_t to_write;
> -    struct vdagent_virtio_port *vport = *vportp;
> -
> -    struct vdagent_virtio_port_buf* wbuf = vport->write_buf;
> -    if (!wbuf) {
> -        syslog(LOG_ERR, "do_write called on a port without a write buf ?!");
> -        return;
> -    }
> -
> -    if (wbuf->write_pos != wbuf->size) {
> -        syslog(LOG_ERR, "do_write: buffer is incomplete!!");
> -        return;
> -    }
> -
> -    to_write = wbuf->size - wbuf->pos;
> -    n = vport_write(vport, wbuf->buf + wbuf->pos, to_write);
> -    if (n < 0) {
> -        if (errno == EINTR)
> -            return;
> -        GError *err = g_error_new(G_IO_ERROR, G_IO_ERROR_FAILED,
> -                                  "writing to vdagent virtio port: %m");
> -        virtio_port_destroy(vportp, err);
> -        return;
> -    }
> -    if (n > 0)
> -        vport->opening = 0;
> -
> -    wbuf->pos += n;
> -    if (wbuf->pos == wbuf->size) {
> -        vport->write_buf = wbuf->next;
> -        g_free(wbuf->buf);
> -        g_free(wbuf);
> -    }
> -}
> diff --git a/src/vdagentd/virtio-port.h b/src/vdagentd/virtio-port.h
> index dfbe27b..7d14deb 100644
> --- a/src/vdagentd/virtio-port.h
> +++ b/src/vdagentd/virtio-port.h
> @@ -22,9 +22,7 @@
>  #ifndef __VIRTIO_PORT_H
>  #define __VIRTIO_PORT_H
>  
> -#include <stdio.h>
>  #include <stdint.h>
> -#include <sys/select.h>
>  #include <spice/vd_agent.h>
>  
>  struct vdagent_virtio_port;
> @@ -57,22 +55,6 @@ struct vdagent_virtio_port *vdagent_virtio_port_create(const char *portname,
>  /* The contents of portp will be made NULL */
>  void vdagent_virtio_port_destroy(struct vdagent_virtio_port **vportp);
>  
> -
> -/* Given a vdagent_virtio_port fill the fd_sets pointed to by readfds and
> -   writefds for select() usage.
> -
> -   Return value: value of the highest fd + 1 */
> -int vdagent_virtio_port_fill_fds(struct vdagent_virtio_port *vport,
> -        fd_set *readfds, fd_set *writefds);
> -
> -/* Handle any events flagged by select for the given vdagent_virtio_port.
> -   Note the port may be destroyed (when disconnected) by this call
> -   in this case the disconnect calllback will get called before the
> -   destruction and the contents of connp will be made NULL */
> -void vdagent_virtio_port_handle_fds(struct vdagent_virtio_port **vportp,
> -        fd_set *readfds, fd_set *writefds);
> -
> -
>  /* Queue a message for delivery, either bit by bit, or all at once */
>  void vdagent_virtio_port_write_start(
>          struct vdagent_virtio_port *vport,
> -- 
> 2.17.1
> 
> _______________________________________________
> Spice-devel mailing list
> Spice-devel at lists.freedesktop.org
> https://lists.freedesktop.org/mailman/listinfo/spice-devel

I still did some comments in the code above. Change seems to work
well and it is an improvement of current code. Even if we can't
get a clear way of removing/reducing virtio-port/usdcs code it
should be mergeable.

Let me know your thoughts.

Cheers,
Victor
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