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

[Laine Stump]

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.

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).