Re: [PATCH 2/6] qemuMigrationCookieNew: Refactor allocation and cleanup

[Michal Prívozník <mprivozn@xxxxxxxxxx>]

On 9/29/20 5:10 PM, Ján Tomko wrote:
> On a Tuesday in 2020, Peter Krempa wrote:
> > Move around some code so that we can get rid of the 'cleanup:' label.
> >
> > Signed-off-by: Peter Krempa <pkrempa@xxxxxxxxxx>
> > ---
> > src/qemu/qemu_migration_cookie.c | 35 ++++++++++++++++----------------
> > 1 file changed, 17 insertions(+), 18 deletions(-)
> >
> > diff --git a/src/qemu/qemu_migration_cookie.c 
> > b/src/qemu/qemu_migration_cookie.c
> > index 124f61e3ea..a04b74f092 100644
> > --- a/src/qemu/qemu_migration_cookie.c
> > +++ b/src/qemu/qemu_migration_cookie.c
> > @@ -280,31 +280,30 @@ qemuMigrationCookieNew(const virDomainDef *def,
> > Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â Â  const char *origname)
> > {
> > Â Â Â  qemuMigrationCookiePtr mig = NULL;
> > -Â Â Â  const char *name;
> > +Â Â Â  unsigned char localHostUUID[VIR_UUID_BUFLEN];
> > +Â Â Â  g_autofree char *localHostname = NULL;
> >
> > -Â Â Â  if (VIR_ALLOC(mig) < 0)
> > -Â Â Â Â Â Â Â  goto error;
> > -
> > -Â Â Â  if (origname)
> > -Â Â Â Â Â Â Â  name = origname;
> > -Â Â Â  else
> > -Â Â Â Â Â Â Â  name = def->name;
> > -Â Â Â  mig->name = g_strdup(name);
> > -Â Â Â  memcpy(mig->uuid, def->uuid, VIR_UUID_BUFLEN);
> > +Â Â Â  if (!(localHostname = virGetHostname()))
> > +Â Â Â Â Â Â Â  return NULL;
> >
> > -Â Â Â  if (!(mig->localHostname = virGetHostname()))
> > -Â Â Â Â Â Â Â  goto error;
>
> Note that as of:
> commit 26d9748ff114a060ee751959d108d062f737f5d9
>  Â Â Â  util: replace gethostname() with g_get_hostname()
> the virGetHostname function always g_strdup's something.

Since you mentioned this, g_get_hostname() is horrible API as it caches 
the host name on the first run and returns a const char * so there is no 
way for callers to reflect on changing hostname. We had to drop it in 
qemu-ga, because if qemu-ga was started before network was configured 
then hostname change on DHCP wasn't being reflected. Hopefully, it is 
not a problem for libvirt because we start after NICs are configured. 
And nobody is really changing the hostname once a host is running, or 
are they?

# hostname; virsh hostname ; hostname asdf; virsh hostname ; hostname
bart
bart
bart
asdf

Michal