From 64fcd67471ead7a0205f853a32eece6de4d7436b Mon Sep 17 00:00:00 2001
From: Laine Stump <laine@laine.org>
Date: Tue, 27 Jan 2015 11:46:10 -0500
Subject: [PATCH 2/2] Don't return error if /sys/class/net/$dev/operstate isn't
 found

This can happen for alias "interfaces", e.g: "eth0:1" (which aren't
really an interface, but are a deprecated method of adding multiple IP
addresses to a single interface). Since only the base interface
("eth0") is really a device, only it has an entry in /sys/class/net.

It's not important that such interfaces have truly meaningful
information in their <link> element (as we don't really have any truly
meaningful state, and haven't historically provided other status for
alias interfaces (e.g. IP address). What *is* important is that we
don't return an error, as this breaks applications that rely on being
able to get back a successful (if empty) status for any interface
listed.

This resolves the regression with virt-manager described here:

  https://bugzilla.redhat.com/show_bug.cgi?id=1185850

(cherry picked from commit 4d5d84bdec17dbb267b5e038fa649af9d730bda9)
---
 src/dutil_linux.c | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/src/dutil_linux.c b/src/dutil_linux.c
index 52a7299..a8788b6 100644
--- a/src/dutil_linux.c
+++ b/src/dutil_linux.c
@@ -1040,8 +1040,15 @@ static void add_link_info(struct netcf *ncf,
     xasprintf(&path, "/sys/class/net/%s/operstate", ifname);
     ERR_NOMEM(!path, ncf);
     state = read_file(path, &length);
-    ERR_THROW_STRERROR(!state, ncf, EFILE, "Failed to read %s : %s",
-                       path, errbuf);
+    if (!state) {
+        /* missing operstate is *not* an error. It could be due to an
+         * alias interface, which has no entry in /sys/class/net at
+         * all, for example. This is similar to the situation where we
+         * can't find an ifindex in add_ethernet_info().
+         */
+        state = strdup("");
+        ERR_NOMEM(!state, ncf);
+    }
     if ((nl = strchr(state, '\n')))
         *nl = 0;
     prop = xmlSetProp(link_node, BAD_CAST "state", BAD_CAST state);
-- 
1.8.3.1