[libvirt] [PATCH 4/5] virnetdevtap: add virNetDevTapGetName

[Laine Stump]

On 03/25/2013 10:25 AM, Paolo Bonzini wrote:
> This will be used on a tap file descriptor returned by the bridge helper
> to populate the <target> element, because the helper does not provide
> the interface name.
>
> Signed-off-by: Paolo Bonzini <pbonzini at redhat.com>
> ---
>  src/libvirt_private.syms |  1 +
>  src/util/virnetdevtap.c  | 33 +++++++++++++++++++++++++++++++++
>  src/util/virnetdevtap.h  |  3 +++
>  3 files changed, 37 insertions(+)
>
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index f241ec4..06085ba 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -1515,6 +1515,7 @@ virNetDevOpenvswitchSetMigrateData;
>  virNetDevTapCreate;
>  virNetDevTapCreateInBridgePort;
>  virNetDevTapDelete;
> +virNetDevTapGetName;
>  
>  
>  # util/virnetdevveth.h
> diff --git a/src/util/virnetdevtap.c b/src/util/virnetdevtap.c
> index a884de1..e9fddf1 100644
> --- a/src/util/virnetdevtap.c
> +++ b/src/util/virnetdevtap.c
> @@ -44,6 +44,39 @@
>  #define VIR_FROM_THIS VIR_FROM_NONE
>  
>  /**
> + * virNetDevTapGetName:
> + * @tapfd: a tun/tap file descriptor
> + * @ifname: a pointer that will receive the interface name
> + *
> + * Retrieve the interface name given a file descriptor for a tun/tap
> + * interface.
> + *
> + * Returns 0 if the interface name is successfully queried, -1 otherwise
> + */
> +int
> +virNetDevTapGetName(int tapfd, char **ifname)
> +{
> +#ifdef TUNGETIFF
> +    struct ifreq ifr;
> +
> +    /* The kernel will always return -1 at this point.
> +     * If TUNGETIFF is not implemented then errno == EBADFD.
> +     */
> +    if (ioctl(tapfd, TUNGETIFF, &ifr) < 0) {
> +        virReportSystemError(errno, "%s",
> +                             _("Unable to query tap interface name"));
> +        return -1;
> +    }
> +
> +    *ifname = strdup(ifr.ifr_name);

You need to check for OOM here. (actually there are patches pending
somewhere to replace strdup() with a VIR_STRDUP() or something like that
which does the error reporting for you, but you'll still need to return
-1 if it fails).

> +    return 0;
> +#else
> +    return -1;
> +#endif
> +}
> +
> +
> +/**
>   * virNetDevProbeVnetHdr:
>   * @tapfd: a tun/tap file descriptor
>   *
> diff --git a/src/util/virnetdevtap.h b/src/util/virnetdevtap.h
> index 980db61..6bfc80c 100644
> --- a/src/util/virnetdevtap.h
> +++ b/src/util/virnetdevtap.h
> @@ -35,6 +35,9 @@ int virNetDevTapCreate(char **ifname,
>  int virNetDevTapDelete(const char *ifname)
>      ATTRIBUTE_NONNULL(1) ATTRIBUTE_RETURN_CHECK;
>  
> +int virNetDevTapGetName(int tapfd, char **ifname)
> +    ATTRIBUTE_NONNULL(2) ATTRIBUTE_RETURN_CHECK;
> +
>  typedef enum {
>     VIR_NETDEV_TAP_CREATE_NONE = 0,
>     /* Bring the interface up */