Re: [Qemu-devel] [PATCH v2 9/9] chardev: tcp: postpone TLS work until machine done

[Peter Xu]

On Thu, Mar 08, 2018 at 01:31:43PM +0000, Daniel P. Berrangé wrote:
> On Thu, Mar 08, 2018 at 07:42:13PM +0800, Peter Xu wrote:
> > On Thu, Mar 08, 2018 at 10:13:59AM +0000, Daniel P. Berrangé wrote:
> > > On Thu, Mar 08, 2018 at 11:44:09AM +0800, Peter Xu wrote:
> > > > On Wed, Mar 07, 2018 at 12:36:50PM +0000, Daniel P. Berrangé wrote:
> > > > 
> > > > [...]
> > > > 
> > > > > > diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> > > > > > index bd40864f87..997c70dd7d 100644
> > > > > > --- a/chardev/char-socket.c
> > > > > > +++ b/chardev/char-socket.c
> > > > > > @@ -31,6 +31,7 @@
> > > > > >  #include "qemu/option.h"
> > > > > >  #include "qapi/error.h"
> > > > > >  #include "qapi/clone-visitor.h"
> > > > > > +#include "sysemu/sysemu.h"
> > > > > >  
> > > > > >  #include "chardev/char-io.h"
> > > > > >  
> > > > > > @@ -722,6 +723,11 @@ static void tcp_chr_tls_init(Chardev *chr)
> > > > > >      Error *err = NULL;
> > > > > >      gchar *name;
> > > > > >  
> > > > > > +    if (!machine_init_done) {
> > > > > > +        /* This will be postponed to machine_done notifier */
> > > > > > +        return;
> > > > > > +    }
> > > > > > +
> > > > > >      if (s->is_listen) {
> > > > > >          tioc = qio_channel_tls_new_server(
> > > > > >              s->ioc, s->tls_creds,
> > > > > > @@ -1145,6 +1151,10 @@ static int tcp_chr_machine_done_hook(Chardev 
> > > > > > *chr)
> > > > > >          tcp_chr_connect_async(chr);
> > > > > >      }
> > > > > >  
> > > > > > +    if (s->tls_creds) {
> > > > > > +        tcp_chr_tls_init(chr);
> > > > > > +    }
> > > > > 
> > > > > This looks questionable - AFAICT, there's no guarantee we have any
> > > > > client connection active when the machine dnoe hook runs. Only if
> > > > > the chardev is set in client mode, and reconnect_time is *not* set,
> > > > > but this seems to be run unconditionally.
> > > > 
> > > > You are right.  Thanks for spotting that.
> > > > 
> > > > Then how about this?  It's a bit ugly, but I think it should be safe:
> > > 
> > > Is it perhaps not possible to just check if  's->ioc' is non-NULL
> > > in the tcp_chr_machine_done_hook for your original patch ?
> > 
> > In tcp_chr_new_client() I see that s->ioc will be set no matter what,
> > and that function can even be called without TLS enabled I think.
> > Does that mean only check against s->ioc would not be enough?
> 
> I mean like this:
> 
> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> index a1966aae51..19e3193817 100644
> --- a/chardev/char-socket.c
> +++ b/chardev/char-socket.c
> @@ -723,6 +723,11 @@ static void tcp_chr_tls_init(Chardev *chr)
>      Error *err = NULL;
>      gchar *name;
>  
> +    if (!machine_init_done) {
> +        /* This will be postponed to machine_done notifier */
> +        return;
> +    }
> +
>      if (s->is_listen) {
>          tioc = qio_channel_tls_new_server(
>              s->ioc, s->tls_creds,
> @@ -1146,6 +1151,10 @@ static int tcp_chr_machine_done_hook(Chardev *chr)
>          tcp_chr_connect_async(chr);
>      }
>  
> +    if (s->ioc && s->tls_creds) {
> +        tcp_chr_tls_init(chr);
> +    }
> +
>      return 0;
>  }
>  
> 
> 
> s->ioc will only be != NULL, if some codepath in qemu_chr_parse_socket

I guess here you mean qmp_chardev_open_socket().

> ended up calling tcp_chr_new_client(). If that happened we will have
> skipped setup of TLS, so calling tcp_chr_tls_init() based on
> s->ioc && s->tls_creds feels right to me.

Yes, it looks right to me too. :)

I'll post a complete patch soon with your authorship.

Thanks!

-- 
Peter Xu