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

[Luiz Capitulino <lcapitulino@redhat.com>]

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?

> +        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)
>  {