[libvirt] [PATCH 1/3] util: new function virNetDevOpenvswitchInterfaceGetMaster()

[Michal Prívozník]

On 07/02/2018 01:46 AM, Laine Stump wrote:
> This function retrieves the name of the OVS bridge that the given
> netdev is attached to. This separate function is necessary because OVS
> set the IFLA_MASTER attribute to "ovs-system" for all netdevs that are
> attached to an OVS bridge, so the standard method of retrieving the
> master can't be used.
> 
> Signed-off-by: Laine Stump <laine at laine.org>
> ---
>  src/libvirt_private.syms        |  1 +
>  src/util/virnetdevopenvswitch.c | 55 +++++++++++++++++++++++++++++++++++++++++
>  src/util/virnetdevopenvswitch.h |  6 +++++
>  3 files changed, 62 insertions(+)
> 
> diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
> index 98913a577a..386f53eeb9 100644
> --- a/src/libvirt_private.syms
> +++ b/src/libvirt_private.syms
> @@ -2364,6 +2364,7 @@ virNetDevMidonetUnbindPort;
>  virNetDevOpenvswitchAddPort;
>  virNetDevOpenvswitchGetMigrateData;
>  virNetDevOpenvswitchGetVhostuserIfname;
> +virNetDevOpenvswitchInterfaceGetMaster;
>  virNetDevOpenvswitchInterfaceStats;
>  virNetDevOpenvswitchRemovePort;
>  virNetDevOpenvswitchSetMigrateData;
> diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c
> index f86f698430..af3f2a773d 100644
> --- a/src/util/virnetdevopenvswitch.c
> +++ b/src/util/virnetdevopenvswitch.c
> @@ -404,6 +404,61 @@ virNetDevOpenvswitchInterfaceStats(const char *ifname,
>      return ret;
>  }
>  
> +
> +/**
> + * virNetDeOpenvswitchGetMaster:
> + * @ifname: name of interface we're interested in
> + * @master: used to return a string containing the name of @ifname's "master"
> + *          (this is the bridge or bond device that this device is attached to)
> + *
> + * Returns 0 on success, -1 on failure (if @ifname has no master
> + * @master will be NULL, but return value will still be 0 (success)).
> + *
> + * NB: This function is needed because the IFLA_MASTER attribute of an
> + * interface in a netlink dump (see virNetDevGetMaster()) will always
> + * return "ovs-system" for any interface that is attached to an OVS
> + * switch. When that happens, virNetDevOpenvswitchInterfaceGetMaster()
> + * must be called to get the "real" master of the interface.
> + */
> +int
> +virNetDevOpenvswitchInterfaceGetMaster(const char *ifname, char **master)
> +{
> +    virCommandPtr cmd = NULL;
> +    int ret = -1;
> +    int exitstatus;
> +
> +    *master = NULL;
> +    cmd = virCommandNew(OVSVSCTL);

I'd put an empty line in between these two ^^ because from data POV we
have two different blocks (one initializes variables, the other
constructs @cmd). But it is really a nit pick.

> +    virNetDevOpenvswitchAddTimeout(cmd);
> +    virCommandAddArgList(cmd, "iface-to-br", ifname, NULL);
> +    virCommandSetOutputBuffer(cmd, master);
> +
> +    if (virCommandRun(cmd, &exitstatus) < 0) {
> +        virReportError(VIR_ERR_INTERNAL_ERROR,
> +                       _("Unable to run command to get OVS master for "
> +                         "interface %s"), ifname);
> +        goto cleanup;
> +    }
> +
> +    /* non-0 exit code just means that the interface has no master in OVS */
> +    if (exitstatus != 0)
> +        VIR_FREE(*master);

A-ha! We indeed need to do this. I was under impression that just like
other functions of ours if they fail no allocation is done. But this is
different so we need to call VIR_FREE().


Michal