[libvirt PATCH v2 33/56] src: introduce helper API for creating GSource for socket

[Pavel Hrdina]

On Tue, Jan 28, 2020 at 01:11:14PM +0000, Daniel P. Berrangé wrote:
> We need to be able to create event loop watches using the
> GSource API for sockets. GIOChannel is able todo this, but
> we don't want to use the GIOChannel APIs for reading/writing,
> and testing shows just using its GSource APIs is unreliable
> on Windows.
> 
> This patch thus creates a standalone helper API for creating
> a GSource for a socket file descriptor. This impl is derived
> from code in QEMU's io/channel-watch.c file that was written
> by myself & Paolo Bonzini & thus under Red Hat copyright.
> 
> Signed-off-by: Daniel P. Berrangé <berrange at redhat.com>
> ---
>  build-aux/syntax-check.mk    |   3 +
>  src/util/Makefile.inc.am     |   2 +
>  src/util/vireventglibwatch.c | 248 +++++++++++++++++++++++++++++++++++
>  src/util/vireventglibwatch.h |  48 +++++++
>  4 files changed, 301 insertions(+)
>  create mode 100644 src/util/vireventglibwatch.c
>  create mode 100644 src/util/vireventglibwatch.h
> 
> diff --git a/src/util/vireventglibwatch.c b/src/util/vireventglibwatch.c
> new file mode 100644
> index 0000000000..f7b087e2ec
> --- /dev/null
> +++ b/src/util/vireventglibwatch.c
> @@ -0,0 +1,248 @@
> +/*
> + * vireventglibwatch.c: GSource impl for sockets
> + *
> + * Copyright (C) 2015-2020 Red Hat, Inc.
> + *
> + * 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 "vireventglibwatch.h"
> +
> +#ifndef WIN32
> +typedef struct virEventGLibFDSource virEventGLibFDSource;
> +struct virEventGLibFDSource {
> +    GSource parent;
> +    GPollFD pollfd;
> +    int fd;
> +    GIOCondition condition;
> +};
> +
> +
> +static gboolean
> +virEventGLibFDSourcePrepare(GSource *source G_GNUC_UNUSED,
> +                            gint *timeout)
> +{
> +    *timeout = -1;
> +
> +    return FALSE;
> +}
> +
> +
> +static gboolean
> +virEventGLibFDSourceCheck(GSource *source)
> +{
> +    virEventGLibFDSource *ssource = (virEventGLibFDSource *)source;
> +
> +    return ssource->pollfd.revents & ssource->condition;
> +}
> +
> +
> +static gboolean
> +virEventGLibFDSourceDispatch(GSource *source,
> +                             GSourceFunc callback,
> +                             gpointer user_data)
> +{
> +    virEventGLibSocketFunc func = (virEventGLibSocketFunc)callback;
> +    virEventGLibFDSource *ssource = (virEventGLibFDSource *)source;
> +
> +    return (*func)(ssource->fd,
> +                   ssource->pollfd.revents & ssource->condition,
> +                   user_data);
> +}
> +
> +
> +static void
> +virEventGLibFDSourceFinalize(GSource *source G_GNUC_UNUSED)
> +{
> +}
> +
> +
> +GSourceFuncs virEventGLibFDSourceFuncs = {
> +    .prepare = virEventGLibFDSourcePrepare,
> +    .check = virEventGLibFDSourceCheck,
> +    .dispatch = virEventGLibFDSourceDispatch,
> +    .finalize = virEventGLibFDSourceFinalize
> +};
> +
> +
> +GSource *virEventGLibCreateSocketWatch(int fd,
> +                                       GIOCondition condition)
> +{
> +    GSource *source;
> +    virEventGLibFDSource *ssource;
> +
> +    source = g_source_new(&virEventGLibFDSourceFuncs,
> +                          sizeof(virEventGLibFDSource));
> +    ssource = (virEventGLibFDSource *)source;
> +
> +    ssource->condition = condition;
> +    ssource->fd = fd;
> +
> +    ssource->pollfd.fd = fd;
> +    ssource->pollfd.events = condition;
> +
> +    g_source_add_poll(source, &ssource->pollfd);
> +
> +    return source;
> +}
> +
> +#else /* WIN32 */
> +
> +# define WIN32_LEAN_AND_MEAN
> +# include <winsock2.h>
> +
> +typedef struct virEventGLibSocketSource virEventGLibSocketSource;
> +struct virEventGLibSocketSource {
> +    GSource parent;
> +    GPollFD pollfd;
> +    int fd;
> +    SOCKET socket;
> +    HANDLE event;
> +    int revents;
> +    GIOCondition condition;
> +};
> +
> +
> +static gboolean
> +virEventGLibSocketSourcePrepare(GSource *source G_GNUC_UNUSED,
> +                                gint *timeout)
> +{
> +    *timeout = -1;
> +
> +    return FALSE;
> +}
> +
> +
> +/*
> + * NB, this impl only works when the socket is in non-blocking
> + * mode on Win32
> + */
> +static gboolean
> +virEventGLibSocketSourceCheck(GSource *source)
> +{
> +    static struct timeval tv0;
> +
> +    virEventGLibSocketSource *ssource = (virEventGLibSocketSource *)source;
> +    WSANETWORKEVENTS ev;
> +    fd_set rfds, wfds, xfds;
> +
> +    if (!ssource->condition)
> +        return 0;
> +
> +    WSAEnumNetworkEvents(ssource->socket, ssource->event, &ev);
> +
> +    FD_ZERO(&rfds);
> +    FD_ZERO(&wfds);
> +    FD_ZERO(&xfds);
> +    if (ssource->condition & G_IO_IN)
> +        FD_SET(ssource->socket, &rfds);
> +    if (ssource->condition & G_IO_OUT)
> +        FD_SET(ssource->socket, &wfds);
> +    if (ssource->condition & G_IO_PRI)
> +        FD_SET(ssource->socket, &xfds);
> +
> +    ssource->revents = 0;
> +    if (select(0, &rfds, &wfds, &xfds, &tv0) == 0)
> +        return 0;
> +
> +    if (FD_ISSET(ssource->socket, &rfds))
> +        ssource->revents |= G_IO_IN;
> +
> +    if (FD_ISSET(ssource->socket, &wfds))
> +        ssource->revents |= G_IO_OUT;
> +
> +    if (FD_ISSET(ssource->socket, &xfds))
> +        ssource->revents |= G_IO_PRI;
> +
> +    return ssource->revents;
> +}
> +
> +
> +static gboolean
> +virEventGLibSocketSourceDispatch(GSource *source,
> +                                 GSourceFunc callback,
> +                                 gpointer user_data)
> +{
> +    virEventGLibSocketFunc func = (virEventGLibSocketFunc)callback;
> +    virEventGLibSocketSource *ssource = (virEventGLibSocketSource *)source;
> +
> +    return (*func)(ssource->fd, ssource->revents, user_data);
> +}
> +
> +
> +static void
> +virEventGLibSocketSourceFinalize(GSource *source)
> +{
> +    virEventGLibSocketSource *ssource = (virEventGLibSocketSource *)source;
> +
> +    WSAEventSelect(ssource->socket, NULL, 0);
> +}
> +
> +
> +GSourceFuncs virEventGLibSocketSourceFuncs = {
> +    .prepare = virEventGLibSocketSourcePrepare,
> +    .check = virEventGLibSocketSourceCheck,
> +    .dispatch = virEventGLibSocketSourceDispatch,
> +    .finalize = virEventGLibSocketSourceFinalize
> +};
> +
> +
> +GSource *virEventGLibCreateSocketWatch(int fd,
> +                                       GIOCondition condition)
> +{
> +    GSource *source;
> +    virEventGLibSocketSource *ssource;
> +
> +    source = g_source_new(&virEventGLibSocketSourceFuncs,
> +                          sizeof(virEventGLibSocketSource));
> +    ssource = (virEventGLibSocketSource *)source;
> +
> +    ssource->condition = condition;
> +    ssource->fd = fd;
> +    ssource->socket = _get_osfhandle(fd);
> +    ssource->event = CreateEvent(NULL, FALSE, FALSE, NULL);

Based on going through QEMU code and windows documentation it looks
like we have to free the event using CloseHandle().

QEMU is doing it in io/channel.c in qio_channel_finalize() which is
probably called by unrefing ssource->ioc in
qio_channel_fd_pair_source_finalize().

That would mean we have to call CloseHandle() in
virEventGLibSocketSourceFinalize() to make sure we will not leak any
resources.

Otherwise looks good.

Pavel
-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 833 bytes
Desc: not available
URL: <http://listman.redhat.com/archives/libvir-list/attachments/20200129/30c99743/attachment-0001.sig>