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

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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@xxxxxxxxxx>
---
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@xxxxxxxxxxxxxxxxxxxxxx

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

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