[libvirt] [PATCH] util: suppress unimportant ovs-vsctl errors when getting interface stats

[Michal Privoznik]

On 3/27/19 8:04 PM, Laine Stump wrote:
> commit edaf13565 modified the stats retrieval for OVS interfaces to
> not fail when one of the fields was unrecognized by the ovs-vsctl
> command, but ovs-vsctl was still returning an error, and libvirt was
> cluttering the logs with these inconsequential error messages.
> 
> This patch modifies the GET_STAT macro to add "--if-exists" to the
> ovs-vsctl command, which causes it to return an empty string (and exit
> with success) if the requested statistic isn't in its database, thus
> eliminating the ugly error messages from the log.
> 
> Resolves: https://bugzilla.redhat.com/1683175
> 
> Signed-off-by: Laine Stump <laine at laine.org>
> ---
>   src/util/virnetdevopenvswitch.c | 6 +++---
>   1 file changed, 3 insertions(+), 3 deletions(-)
> 
> diff --git a/src/util/virnetdevopenvswitch.c b/src/util/virnetdevopenvswitch.c
> index 4fa3a5742a..e5a45f59ec 100644
> --- a/src/util/virnetdevopenvswitch.c
> +++ b/src/util/virnetdevopenvswitch.c
> @@ -335,10 +335,10 @@ virNetDevOpenvswitchInterfaceStats(const char *ifname,
>           virCommandFree(cmd); \
>           cmd = virCommandNew(OVSVSCTL); \
>           virNetDevOpenvswitchAddTimeout(cmd); \
> -        virCommandAddArgList(cmd, "get", "Interface", ifname, \
> -                             "statistics:" name, NULL); \
> +        virCommandAddArgList(cmd, "--if-exists", "get", "Interface", \
> +                             ifname, "statistics:" name, NULL); \
>           virCommandSetOutputBuffer(cmd, &output); \
> -        if (virCommandRun(cmd, NULL) < 0) { \
> +        if (virCommandRun(cmd, NULL) < 0 || !*output || *output == '\n') { \

I think we need '|| !output' before any of these @output checks. If 
virCommandRun() fails before it had a chance to allocate @output this 
would case NULL dereference.

>               stats->member = -1; \
>           } else { \
>               if (virStrToLong_ll(output, &tmp, 10, &stats->member) < 0 || \
> 

ACK

Michal