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

[Michal Privoznik]

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 */
 
     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) {
+        lnk->speed = 0;
+        ret = 0;
+        goto cleanup;
+    }
+
     VIR_FREE(path);
     VIR_FREE(buf);
 
@@ -1884,6 +1894,7 @@ virNetDevGetLinkInfo(const char *ifname,
     if (virFileReadAll(path, 1024, &buf) < 0) {
         /* Some devices doesn't report speed, in which case we get EINVAL */
         if (errno == EINVAL) {
+            lnk->speed = 0;
             ret = 0;
             goto cleanup;
         }
-- 
1.8.5.5