Introduce virnetdevtest

This is yet another test for check of basic functionality of our
NIC state handling code.

Signed-off-by: Michal Privoznik <mprivozn@redhat.com>

tests/virnetdevmock.c

@@ -0,0 +1,48 @@
+/*
+ * Copyright (C) 2015 Red Hat, Inc.
+ *
+ * This library is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU Lesser General Public
+ * License as published by the Free Software Foundation; either
+ * version 2.1 of the License, or (at your option) any later version.
+ *
+ * This library is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+ * Lesser General Public License for more details.
+ *
+ * You should have received a copy of the GNU Lesser General Public
+ * License along with this library.  If not, see
+ * <http://www.gnu.org/licenses/>.
+ *
+ * Author: Michal Privoznik <mprivozn@redhat.com>
+ */
+
+#include <config.h>
+
+#ifdef __linux__
+# include "internal.h"
+# include <stdlib.h>
+# include <stdio.h>
+# include "virstring.h"
+# include "virnetdev.h"
+
+# define NET_DEV_TEST_DATA_PREFIX abs_srcdir "/virnetdevtestdata/sys/class/net"
+
+int
+virNetDevSysfsFile(char **pf_sysfs_device_link,
+                   const char *ifname,
+                   const char *file)
+{
+
+    if (virAsprintfQuiet(pf_sysfs_device_link, "%s/%s/%s",
+                         NET_DEV_TEST_DATA_PREFIX, ifname, file) < 0) {
+        fprintf(stderr, "Out of memory\n");
+        abort();
+    }
+
+    return 0;
+}
+#else
+/* Nothing to override on non-__linux__ platforms */
+#endif