Re: [Qemu-devel] [PATCH] Add guest-get-hostname to retrieve the guests current hostname

[Michael Roth <mdroth@linux.vnet.ibm.com>]

On Thu, Aug 23, 2012 at 09:48:54AM -0300, Luiz Capitulino wrote:
> On Tue, 21 Aug 2012 13:57:54 +0200
> Guido Günther <agx@sigxcpu.org> wrote:
> 
> > This allows to retrieve the guest's hostname via gethostname(2).
> > 
> > This can be useful to identify a VM e.g. one without network.
> > 
> > Signed-off-by: Guido Günther <agx@sigxcpu.org>
> > ---
> > We have an API in libvirt for that (virDomainGetHostname).
> > Cheers
> >  -- Guido
> > 
> >  qapi-schema-guest.json |   12 ++++++++++++
> >  qga/commands-posix.c   |   12 ++++++++++++
> >  qga/commands-win32.c   |    6 ++++++
> >  3 files changed, 30 insertions(+)
> > 
> > diff --git a/qapi-schema-guest.json b/qapi-schema-guest.json
> > index d955cf1..8c7a4a5 100644
> > --- a/qapi-schema-guest.json
> > +++ b/qapi-schema-guest.json
> > @@ -515,3 +515,15 @@
> >  ##
> >  { 'command': 'guest-network-get-interfaces',
> >    'returns': ['GuestNetworkInterface'] }
> > +
> > +##
> > +# @guest-get-hostname:
> > +#
> > +# Get the guest's hostname
> > +#
> > +# Returns: The guest's hostname
> > +#
> > +# Since: 1.2
> 
> Won't make it for 1.2 because we're in hard-freeze.
> 
> > +##
> > +{ 'command': 'guest-get-hostname',
> > +  'returns': 'str' }
> > diff --git a/qga/commands-posix.c b/qga/commands-posix.c
> > index ce90421..9223f18 100644
> > --- a/qga/commands-posix.c
> > +++ b/qga/commands-posix.c
> > @@ -15,6 +15,7 @@
> >  #include <sys/types.h>
> >  #include <sys/ioctl.h>
> >  #include <sys/wait.h>
> > +#include <unistd.h>
> >  #include "qga/guest-agent-core.h"
> >  #include "qga-qmp-commands.h"
> >  #include "qerror.h"
> > @@ -993,6 +994,17 @@ void qmp_guest_fstrim(bool has_minimum, int64_t minimum, Error **err)
> >  }
> >  #endif
> >  
> > +char *qmp_guest_get_hostname(Error **err)
> > +{
> > +    char hostname[HOST_NAME_MAX];
> > +
> > +    if (gethostname(hostname, HOST_NAME_MAX)) {
> > +        error_set(err, QERR_QGA_COMMAND_FAILED, strerror(errno));
> 
> You shouldn't use that macro, you can do something like this instead:
> 
>  error_set(err, "can't get hostname: %s", strerror(errno));
> 
> Michael, do you think that's fine for new error messages or do you think it's
> worth it to add a "guest-agent: " prefix to all guest agent error messages?
> 

I think that's fine. libvirt or QMP (if we integrate the qemu-ga
commands with QMP) can tack on a prefix for cases where we need to distinguish
where in the stack the error occurred, but for direct communication with
qemu-ga it's unambiguous, so might as well save the keystrokes.

> > +        return NULL;
> > +    }
> > +    return g_strdup(hostname);
> > +}
> > +
> >  /* register init/cleanup routines for stateful command groups */
> >  void ga_command_state_init(GAState *s, GACommandState *cs)
> >  {
> > diff --git a/qga/commands-win32.c b/qga/commands-win32.c
> > index 54bc546..55e8162 100644
> > --- a/qga/commands-win32.c
> > +++ b/qga/commands-win32.c
> > @@ -280,6 +280,12 @@ GuestNetworkInterfaceList *qmp_guest_network_get_interfaces(Error **err)
> >      return NULL;
> >  }
> >  
> > +char *qmp_guest_get_hostname(Error **err)
> > +{
> > +    error_set(err, QERR_UNSUPPORTED);
> > +    return NULL;
> > +}
> > +
> >  /* register init/cleanup routines for stateful command groups */
> >  void ga_command_state_init(GAState *s, GACommandState *cs)
> >  {
> 
>