Re: [Qemu-devel] [PATCH v2 3/3] socket: unlink unix socket on remove

["Marc-André Lureau" <mlureau@redhat.com>]

Hi

----- Original Message -----
> On Thu, Jun 23, 2016 at 07:41:55AM +0300, Michael S. Tsirkin wrote:
> > On Thu, Jun 16, 2016 at 09:28:52PM +0200, marcandre.lureau@redhat.com
> > wrote:
> > > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> > > 
> > > qemu leaves unix socket files behind when removing a listening chardev
> > > or leaving. qemu could clean that up, even if doing so isn't race-free.
> > > 
> > > Fixes:
> > > https://bugzilla.redhat.com/show_bug.cgi?id=1347077
> > > 
> > > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > 
> > We normally only unlink what we created.

What do you mean by "we", qemu currently unlink before creating the unix socket. No further cleanup.
 
> > 
> > unlinking files we didn't create
> > looks like a silent change that might easily break
> > existing users.

That shouldn't remove files we didn't create. But a bad user could recreate the unix socket after qemu did, and that would remove it. I don't think that's a valid use case though, so it should be fine.

> Maybe what you want is a need_unlink feature.
> Set it for unix sockets only, that would make some sense.

Oh perhaps what you mean is that if the fd was passed, we should cleanup the unix socket? Yes, I think we should do that then. I'll update the series.

thanks
 
> 
> > 
> > > ---
> > >  include/qemu/sockets.h         |  1 +
> > >  io/channel-socket.c            | 10 ++++++++++
> > >  tests/test-io-channel-socket.c |  2 +-
> > >  util/qemu-sockets.c            | 18 ++++++++++++++++++
> > >  4 files changed, 30 insertions(+), 1 deletion(-)
> > > 
> > > diff --git a/include/qemu/sockets.h b/include/qemu/sockets.h
> > > index 1bd9218..5dd2648 100644
> > > --- a/include/qemu/sockets.h
> > > +++ b/include/qemu/sockets.h
> > > @@ -51,6 +51,7 @@ SocketAddress *socket_parse(const char *str, Error
> > > **errp);
> > >  int socket_connect(SocketAddress *addr, Error **errp,
> > >                     NonBlockingConnectHandler *callback, void *opaque);
> > >  int socket_listen(SocketAddress *addr, Error **errp);
> > > +void socket_listen_cleanup(int fd, Error **errp);
> > >  int socket_dgram(SocketAddress *remote, SocketAddress *local, Error
> > >  **errp);
> > >  
> > >  /* Old, ipv4 only bits.  Don't use for new code. */
> > > diff --git a/io/channel-socket.c b/io/channel-socket.c
> > > index 1cd5848..6ec87f8 100644
> > > --- a/io/channel-socket.c
> > > +++ b/io/channel-socket.c
> > > @@ -400,7 +400,17 @@ static void qio_channel_socket_init(Object *obj)
> > >  static void qio_channel_socket_finalize(Object *obj)
> > >  {
> > >      QIOChannelSocket *ioc = QIO_CHANNEL_SOCKET(obj);
> > > +
> > >      if (ioc->fd != -1) {
> > > +        if (QIO_CHANNEL(ioc)->features & QIO_CHANNEL_FEATURE_LISTEN) {
> > > +            Error *err = NULL;
> > > +
> > > +            socket_listen_cleanup(ioc->fd, &err);
> > > +            if (err) {
> > > +                error_report_err(err);
> > > +                err = NULL;
> > > +            }
> > > +        }
> > >  #ifdef WIN32
> > >          WSAEventSelect(ioc->fd, NULL, 0);
> > >  #endif
> > > diff --git a/tests/test-io-channel-socket.c
> > > b/tests/test-io-channel-socket.c
> > > index 855306b..f73e063 100644
> > > --- a/tests/test-io-channel-socket.c
> > > +++ b/tests/test-io-channel-socket.c
> > > @@ -383,7 +383,7 @@ static void test_io_channel_unix(bool async)
> > >  
> > >      qapi_free_SocketAddress(listen_addr);
> > >      qapi_free_SocketAddress(connect_addr);
> > > -    unlink(TEST_SOCKET);
> > > +    g_assert(g_file_test(TEST_SOCKET, G_FILE_TEST_EXISTS) == FALSE);
> > >  }
> > >  
> > >  
> > > diff --git a/util/qemu-sockets.c b/util/qemu-sockets.c
> > > index 0d6cd1f..5d03695 100644
> > > --- a/util/qemu-sockets.c
> > > +++ b/util/qemu-sockets.c
> > > @@ -997,6 +997,24 @@ int socket_listen(SocketAddress *addr, Error **errp)
> > >      return fd;
> > >  }
> > >  
> > > +void socket_listen_cleanup(int fd, Error **errp)
> > > +{
> > > +    SocketAddress *addr;
> > > +
> > > +    addr = socket_local_address(fd, errp);
> > > +
> > > +    if (addr->type == SOCKET_ADDRESS_KIND_UNIX
> > > +        && addr->u.q_unix.data->path) {
> > > +        if (unlink(addr->u.q_unix.data->path) < 0 && errno != ENOENT) {
> > > +            error_setg_errno(errp, errno,
> > > +                             "Failed to unlink socket %s",
> > > +                             addr->u.q_unix.data->path);
> > > +        }
> > > +    }
> > > +
> > > +    g_free(addr);
> > > +}
> > > +
> > >  int socket_dgram(SocketAddress *remote, SocketAddress *local, Error
> > >  **errp)
> > >  {
> > >      int fd;
> > > --
> > > 2.7.4
> > > 
>