Re: [Qemu-devel] [PATCH FYI 12/46] io: add QIOChannelTLS class

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

On Mon, Sep 07, 2015 at 04:31:08PM +0100, Dr. David Alan Gilbert wrote:
> * Daniel P. Berrange (berrange@redhat.com) wrote:
> > Add a QIOChannel subclass that can run the TLS protocol over
> > the top of another QIOChannel instance. The object provides a
> > simplified API to perform the handshake when starting the TLS
> > session. The layering of TLS over the underlying channel does
> > not have to be setup immediately. It is possible to take an
> > existing QIOChannel that has done some handshake and then swap
> > in the QIOChannelTLS layer. This allows for use with protocols
> > which start TLS right away, and those which start plain text
> > and then negotiate TLS.
> > 
> > Signed-off-by: Daniel P. Berrange <berrange@redhat.com>
> 
> > ---
> > +#ifdef QIO_DEBUG
> > +#define DPRINTF(fmt, ...) do { fprintf(stderr, fmt, ## __VA_ARGS__); } while (0)
> > +#else
> > +#define DPRINTF(fmt, ...) do { } while (0)
> > +#endif
> 
> Can you use the trace_ stuff rather than dprintf's; I've been trying
> to remove them all from the migration code (and with trace configured in
> stderr mode it works pretty easily).

Yeah, that's a good idea.

> On a different question; if this TLS channel is backed by a socket, can I do
> a shutdown call that will bubble down to the socket?

The QIOChannel abstract base class did not define any shutdown method,
since that's not a generally applicable concept - essentially only the
sockets interface can do that. So I defined it as a method just on the
QIOChannelSocket class. Given this, the QIOChannelTLS class does not
know about the shutdown call.

This isn't a big deal though - the QIOChannelTLS struct exposes a
pointer to the underling QIOChannel transport, so code that needs
to do a shutdown, can get hold of the underlying channel and call
shutdown on that.

I forgot to do this properly when I integrated with the migration
QEMUFile interface, so I'll fix that up, so shutdown works correctly
with migration when TLS is enabled.

Regards,
Daniel
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