[libvirt] [PATCH] virNetDevGetLinkInfo: Don't report link speed if NIC's down

[Michal Privoznik]

On 13.06.2014 11:23, Laine Stump wrote:
> On 06/13/2014 10:50 AM, Martin Kletzander wrote:
>> On Fri, Jun 13, 2014 at 10:31:53AM +0300, Laine Stump wrote:
>>> On 06/13/2014 10:10 AM, Martin Kletzander wrote:
>>>> On Fri, Jun 13, 2014 at 08:46:59AM +0200, Michal Privoznik wrote:
>>>>> The kernel's more broken than one would think. Various drivers report
>>>>> various (usually spurious) values if the interface is down. While on
>>>>> some we experience -EINVAL when read()-ing the speed sysfs file, with
>>>>> other drivers we might get anything from 0 to UINT_MAX. If that's the
>>>>> case it's better to not report link speed. Well, the interface is down
>>>>> anyway.
>>>>>
>>>>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>>>>> ---
>>>>> src/util/virnetdev.c | 13 ++++++++++++-
>>>>> 1 file changed, 12 insertions(+), 1 deletion(-)
>>>>>
>>>>> diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
>>>>> index 6f3a202..80ef572 100644
>>>>> --- a/src/util/virnetdev.c
>>>>> +++ b/src/util/virnetdev.c
>>>>> @@ -1843,7 +1843,7 @@ virNetDevGetLinkInfo(const char *ifname,
>>>>>      char *buf = NULL;
>>>>>      char *tmp;
>>>>>      int tmp_state;
>>>>> -    unsigned int tmp_speed;
>>>>> +    unsigned int tmp_speed; /* virInterfaceState */
>>>>>
>>>>
>>>> You probably wanted to put this comment next to the line with
>>>> tmp_state and not tmp_speed.
>>>>
>>>>>      if (virNetDevSysfsFile(&path, ifname, "operstate") < 0)
>>>>>          goto cleanup;
>>>>> @@ -1875,6 +1875,16 @@ virNetDevGetLinkInfo(const char *ifname,
>>>>>
>>>>>      lnk->state = tmp_state;
>>>>>
>>>>> +    /* Shortcut to avoid some kernel issues. If link is down (and
>>>>> possibly in
>>>>> +     * other states too) several drivers report several values.
>>>>> While igb
>>>>> +     * reports 65535, realtek goes with 10. To avoid muddying XML
>>>>> with insane
>>>>> +     * values, don't report link speed */
>>>>> +    if (lnk->state == VIR_INTERFACE_STATE_DOWN) {
>>>
>>> Also for VIR_INTERFACE_LOWER_LAYER_DOWN (verified by looking at the
>>> speed reported by a macvtap device when its physdev is down). And I'm
>>> not sure how to get an interface into "NOT_PRESENT" or "DORMANT" state,
>>> but I would imagine that the speed should be 0 in those cases too.
>>>
>>
>> I've seen many other states I have no idea how to achieve.  Wouldn't
>> it make more sense to report the speed only if the state is UP?
>
> That makes enough sense to me that I changed my netcf patch to do just
> that - it sets speed to 0 unless operstate is "up". Still open for
> debate though :-) I just sent the patch to
> netcf-devel at lists.fedorahosted.org

So I'm not applying this patch then and proposing a different one:

https://www.redhat.com/archives/libvir-list/2014-June/msg00647.html

Michal