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

[Michal Privoznik]

On 13.06.2014 12:25, Laine Stump wrote:
> On 06/13/2014 12:34 PM, Michal Privoznik wrote:
>> The kernel's more broken than one would think. Various drivers report
>> various (usually spurious) values if the interface is in other state
>> than 'up' . 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 not up anyway.
>>
>> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
>> ---
>>   src/util/virnetdev.c | 16 +++++++++++-----
>>   1 file changed, 11 insertions(+), 5 deletions(-)
>>
>> diff --git a/src/util/virnetdev.c b/src/util/virnetdev.c
>> index 6f3a202..a551f98 100644
>> --- a/src/util/virnetdev.c
>> +++ b/src/util/virnetdev.c
>> @@ -1875,6 +1875,16 @@ virNetDevGetLinkInfo(const char *ifname,
>>
>>       lnk->state = tmp_state;
>>
>> +    /* Shortcut to avoid some kernel issues. If link is not up several drivers
>> +     * report several misleading values. While igb reports 65535, realtek goes
>> +     * with 10. To avoid muddying XML with insane values, don't report link
>> +     * speed if that's the case. */
>> +    if (lnk->state != VIR_INTERFACE_STATE_UP) {
>> +        lnk->speed = 0;
>> +        ret = 0;
>> +        goto cleanup;
>> +    }
>> +
>>       VIR_FREE(path);
>>       VIR_FREE(buf);
>>
>> @@ -1901,11 +1911,7 @@ virNetDevGetLinkInfo(const char *ifname,
>>           goto cleanup;
>>       }
>>
>> -    /* Workaround broken kernel API. If the link is unplugged then
>> -     * depending on the NIC driver, link speed can be reported as -1.
>> -     * However, the value is printed out as unsigned integer instead of
>> -     * signed one. Terrifying but true. */
>> -    lnk->speed = (int) tmp_speed == -1 ? 0 : tmp_speed;
>> +    lnk->speed = tmp_speed;
>>
>>       ret = 0;
>>    cleanup:
>
> ACK from me. Might want to give a short time for differing opinions (or
> just push this and change as required up until the next release :-)
>

Right. I've pushed this one as it enables testing for every one of us 
running libvirt from git instead of having to manually apply the patch.

Michal