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

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

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 ?

> 
> diff --git a/chardev/char-socket.c b/chardev/char-socket.c
> index bd40864f87..b4686fd23f 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"
> 
> @@ -51,6 +52,11 @@ typedef struct {
>      QIONetListener *listener;
>      GSource *hup_source;
>      QCryptoTLSCreds *tls_creds;
> +    /*
> +     * This should only be used once - when we want to setup TLS for
> +     * the session but we need to wait until machine init done.
> +     */
> +    bool tls_need_postponed_init;
>      int connected;
>      int max_size;
>      int do_telnetopt;
> @@ -791,7 +797,15 @@ static int tcp_chr_new_client(Chardev *chr, QIOChannelSocket *sioc)
>      }
> 
>      if (s->tls_creds) {
> -        tcp_chr_tls_init(chr);
> +        if (machine_init_done) {
> +            tcp_chr_tls_init(chr);
> +        } else {
> +            /*
> +             * Postpone to machine init done since we need the correct
> +             * context to setup the TLS handshake.
> +             */
> +            s->tls_need_postponed_init = true;
> +        }
>      } else {
>          if (s->do_telnetopt) {
>              tcp_chr_telnet_init(chr);
> @@ -1145,6 +1159,11 @@ static int tcp_chr_machine_done_hook(Chardev *chr)
>          tcp_chr_connect_async(chr);
>      }
> 
> +    if (s->tls_need_postponed_init) {
> +        assert(s->tls_creds);
> +        tcp_chr_tls_init(chr);
> +    }
> +
>      return 0;
>  }
> 
> Thanks,
> 
> -- 
> Peter Xu

Regards,
Daniel
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