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

[Martin Kletzander]

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?

>ACK with LOWER_LAYER_DOWN added (I won't insist on the others
>until/unless I see experimental evidence that they need it).
>
>BTW, thinking more about bridge devices - maybe they should be given
>state "up" if the device has been ifup'ed. In other words, in their case
>you could call the functional equivalent of if_is_active() in netcf
>(which does an SIOCGIFFLAGS ioctl and checks for the IFF_UP flag). (in
>any case, bridges should probably just always report a speed of 0).
>
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