Re: [Qemu-devel] [PATCH v2 04/16] ui: convert VNC startup code to use SocketAddress

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

On Tue, Oct 20, 2015 at 06:01:37PM +0100, Peter Maydell wrote:
> On 20 October 2015 at 14:39, Daniel P. Berrange <berrange@redhat.com> wrote:
> > On Mon, Oct 19, 2015 at 04:20:09PM -0600, Eric Blake wrote:
> >> On 10/12/2015 05:14 AM, Daniel P. Berrange wrote:
> >> > The VNC code is currently using QemuOpts to configure the
> >> > sockets connections / listeners it needs. Convert it to
> >> > use SocketAddress to bring it in line with modern QAPI
> >> > based code elsewhere in QEMU.
> 
> >>
> >> > +            if (to) {
> >> > +                saddr->inet->has_to = true;
> >> > +                saddr->inet->to = to;
> >> > +            }
> >> > +            saddr->inet->ipv4 = saddr->inet->has_ipv4 = has_ipv4;
> >> > +            saddr->inet->ipv6 = saddr->inet->has_ipv6 = has_ipv6;
> >>
> >> Do we want to specify has_ipvX as true even when setting inet->ipvX to
> >> false?
> >
> > This saddr instance is passed into 'socket_connect' which then
> > converts it back into a QemuOpts object using
> >
> >     bool ipv4 = addr->has_ipv4 && addr->ipv4;
> >
> > So, we don't need to set has_ipvX to true, when ipvX is false.
> 
> That is not the *only* thing that inet_addr_to_opts does with
> the has_* flags... this kind of thing can be the difference
> between "force ipv4" and "use ipv4 or ipv6".

The original code which used QemuOpts directly had this logic:

inet_listen_opts / inet_connect_opts use this logic:

    ai.ai_family = PF_UNSPEC;
    ....
    if (qemu_opt_get_bool(opts, "ipv4", 0))
        ai.ai_family = PF_INET;
    if (qemu_opt_get_bool(opts, "ipv6", 0))
        ai.ai_family = PF_INET6;

IOW, these methods treat ipv4 being omitted, as equivalent to ipv4=off.

Thus the existing VNC -> qemu-sockets code has this logic:

     VNC      | qemu-sockets
   QemuOpts   |  ai_family
 ----------------------------
  ipv4   ipv6 |
 ----------------------------
  -      -    |  PF_UNSPEC
  -      off  |  PF_UNSPEC
  -      on   |  PF_INET6
  off    -    |  PF_UNSPEC
  off    off  |  PF_UNSPEC
  off    on   |  PF_INET6
  on     -    |  PF_INET
  on     off  |  PF_INET
  on     on   |  PF_INET6


My patch, which also does not distinguish ipv4=off from ipv4 omitted
has the following logic, at various stages of conversion between
QemuOpts & QAPI SocketAddress:


     VNC      |          VNC                 | qemu-sockets | qemu-sockets
   QemuOpts   |      QAPI  SocketAddress     |  QemuOpts    |  ai_family
 -------------------------------------------------------------------------
  ipv4   ipv6 |  has_ipv4 ipv4 has_ipv6 ipv6 |   ipv4 ipv6  |
 -------------------------------------------------------------------------
  -      -    |  f        f    f        f    |  -     -     | PF_UNSPEC
  -      off  |  f        f    f        f    |  -     -     | PF_UNSPEC
  -      on   |  f        f    t        t    |  off   on    | PF_INET6
  off    -    |  f        f    f        f    |  -     -     | PF_UNSPEC
  off    off  |  f        f    f        f    |  -     -     | PF_UNSPEC
  off    on   |  f        f    t        t    |  off   on    | PF_INET6
  on     -    |  t        t    f        f    |  on    off   | PF_INET
  on     off  |  t        t    f        f    |  on    off   | PF_INET
  on     on   |  t        t    t        t    |  on    on    | PF_INET6

So, unless I've missed something, the final ai_family is set the same
way before & after my patch, for all combinations of VNC ipv4/ipv6
CLI options.

Regards,
Daniel
-- 
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