Re: [PATCH] qga: Use gethostname() instead of g_get_host_name()

[Michal Privoznik]

On 6/22/20 12:14 PM, Philippe Mathieu-Daudé wrote:
> Hi Michal,
>
> On 6/16/20 10:34 AM, Michal Privoznik wrote:
> > Problem with g_get_host_name() is that on the first call it saves
> > the hostname into a global variable and from then on, every
> > subsequent call returns the saved hostname. Even if the hostname
> > changes. This doesn't play nicely with guest agent, because if
> > the hostname is acquired before the guest is set up (e.g. on the
> > first boot, or before DHCP) we will report old, invalid hostname.
> >
> > Fixes: https://bugzilla.redhat.com/show_bug.cgi?id=1845127
> >
> > Signed-off-by: Michal Privoznik <mprivozn@redhat.com>
> > ---
> >   qga/commands.c | 56 ++++++++++++++++++++++++++++++++++++++++++++++----
> >   1 file changed, 52 insertions(+), 4 deletions(-)
> >
> > diff --git a/qga/commands.c b/qga/commands.c
> > index efc8b90281..ce3c2041a6 100644
> > --- a/qga/commands.c
> > +++ b/qga/commands.c
> > @@ -512,14 +512,62 @@ int ga_parse_whence(GuestFileWhence *whence, Error **errp)
> >       return -1;
> >   }
> >   
> > +#ifndef HOST_NAME_MAX
> > +# ifdef _POSIX_HOST_NAME_MAX
> > +#  define HOST_NAME_MAX _POSIX_HOST_NAME_MAX
> > +# else
> > +#  define HOST_NAME_MAX 255
> > +# endif
> > +#endif
> > +
> >   GuestHostName *qmp_guest_get_host_name(Error **errp)
> >   {
> >       GuestHostName *result = NULL;
> > -    gchar const *hostname = g_get_host_name();
> > -    if (hostname != NULL) {
> > -        result = g_new0(GuestHostName, 1);
> > -        result->host_name = g_strdup(hostname);
> > +    g_autofree char *hostname = NULL;
> > +
> > +    /*
> > +     * We want to avoid using g_get_host_name() because that
> > +     * caches the result and we wouldn't reflect changes in the
> > +     * host name.
> > +     */
>
> I see there is only one g_get_host_name() call in the
> codebase, but can we have a generic qemu_get_host_name()
> helper implemented in util/oslib-*c instead?

Sure. Let me post a v2 so that I can include Richard's suggestion too.

Michal