Re: [Qemu-devel] [PATCH] io: fix handling of EOF / error conditions in websock GSource

["Daniel P. Berrangé" <berrange@redhat.com>]

On Wed, Feb 20, 2019 at 08:52:34PM +0100, Philippe Mathieu-Daudé wrote:
> Hi Daniel,
> 
> On 2/20/19 7:25 PM, Daniel P. Berrangé wrote:
> > We were never reporting the G_IO_HUP event when an end of file was hit
> > on the websocket channel.
> > 
> > We also ddn't report G_IO_ERR when we hit a fatal error processing the
> 
> "didn't report"
> 
> > websocket protocol.
> > 
> > The latter in particular meant that the chardev code would not notice
> > when an eof/error was encountered on the websocket channel, unless the
> > guest OS happened to trigger a write operation.
> > 
> > This meant that once the first client had quit, the chardev would never
> > listen to accept a new client.
> > 
> > Fixes launchpad bug 1816819
> > Signed-off-by: Daniel P. Berrangé <berrange@redhat.com>
> > ---
> >  io/channel-websock.c | 8 +++++++-
> >  1 file changed, 7 insertions(+), 1 deletion(-)
> > 
> > diff --git a/io/channel-websock.c b/io/channel-websock.c
> > index dc43dc6bb9..fc4c3dcaa5 100644
> > --- a/io/channel-websock.c
> > +++ b/io/channel-websock.c
> > @@ -1225,12 +1225,18 @@ qio_channel_websock_source_check(GSource *source)
> >      QIOChannelWebsockSource *wsource = (QIOChannelWebsockSource *)source;
> >      GIOCondition cond = 0;
> >  
> > -    if (wsource->wioc->rawinput.offset || wsource->wioc->io_eof) {
> > +    if (wsource->wioc->rawinput.offset) {
> >          cond |= G_IO_IN;
> >      }
> >      if (wsource->wioc->encoutput.offset < QIO_CHANNEL_WEBSOCK_MAX_BUFFER) {
> >          cond |= G_IO_OUT;
> >      }
> > +    if (wsource->wioc->io_eof) {
> > +        cond |= G_IO_IN | G_IO_HUP;
> 
> Shouldn't this be:
> 
>            cond |= G_IO_HUP;

With regular poll() on FD I believe you typically get POLLIN | POLLHUP as
a pair.

> 
> > +    }
> > +    if (wsource->wioc->io_err) {
> > +        cond |= G_IO_IN | G_IO_ERR;
> 
> Ditto:
> 
>            cond |= G_IO_ERR;

And I just followed the same practice here.

> > +    }
> >  
> >      return cond & wsource->condition;

Regards,
Daniel
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