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

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&gt; >> --- >> 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).