Re: [libvirt] [PATCH] virNetDevGetLinkInfo: Don't report link speed if NIC's down
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(a)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(a)lists.fedorahosted.org
Note that netcf will now report link state for interfaces that are a
subordinate of another interface (e.g. the ethernets attached to a
bridge or a bond, or a bond attached to a bridge). libvirt tosses those
out, so I should probably do a patch to remedy that.
> 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.
I've decided against this in netcf, and instead simply omit the <link>
element entirely if the interface type is bridge.
> 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).
>