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 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
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.

Regards,
Daniel
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