--- iputils-s20121011/arping.c.orig	2012-10-16 11:46:12.000000000 +0200
+++ iputils-s20121011/arping.c	2012-10-16 11:49:09.746673028 +0200
@@ -40,7 +40,7 @@
 static void usage(void) __attribute__((noreturn));
 
 int quit_on_reply=0;
-char *device="eth0";
+char *device=NULL;
 int ifindex;
 char *source;
 struct in_addr src, dst;
@@ -69,6 +69,11 @@ int received, brd_recv, req_recv;
 #define SYSFS_PATH_LEN          256
 #define SOCKADDR_LEN            (2 * sizeof(struct sockaddr_ll))
 
+#define PREF_ETH                "eth"
+#define PREF_EM                 "em"
+
+static char *dev_file = "/proc/self/net/dev";
+
 #define MS_TDIFF(tv1,tv2) ( ((tv1).tv_sec-(tv2).tv_sec)*1000 + \
 			   ((tv1).tv_usec-(tv2).tv_usec)/1000 )
 
@@ -380,6 +385,46 @@ char * read_sysfs_broadcast(char *brdcas
 	return brdcast;
 }
 
+/*
+ * get_first_ethernet - return the name of the first ethernet-style
+ * interface on this system.
+ */
+char * get_first_ethernet(void)
+{
+	FILE *f;
+	char buf[255], *dv, *smc;
+	char pci[16];
+
+	memset(pci, 0, sizeof(pci));
+	if ((f = fopen(dev_file, "r")) != NULL)
+	{
+		// go through network dev file
+		while (fgets (buf, sizeof(buf), f) != NULL)
+		{
+			// the line describes interface
+			if ((smc = strchr(buf, ':')) != NULL)
+			{
+				// trim white characters
+				for (dv=buf, *smc=0; *dv <= ' '; dv++) ;
+				// is "eth" (originial ethernet name) or "em" (ethernet on board)
+				if (!strncmp(dv, PREF_ETH, strlen(PREF_ETH)) ||
+					!strncmp(dv, PREF_EM, strlen(PREF_EM)))
+				{
+					return strdup(dv);
+				}
+				// remember the first pci NIC-card
+				if (strlen(pci) == 0 && dv[0] == 'p' && isdigit(dv[1]))
+				{
+					strcpy(pci, dv);
+				}
+			}
+		}
+		fclose(f);
+	}
+	// return pci NIC-card or nil if no if name
+	return strlen(pci) > 0 ? strdup(pci) : 0L;
+}
+
 int
 main(int argc, char **argv)
 {
@@ -417,6 +462,8 @@ main(int argc, char **argv)
 		exit(1);
 	}
 
+	device = get_first_ethernet();
+
 	while ((ch = getopt(argc, argv, "h?bfDUAqc:w:s:I:V")) != EOF) {
 		switch(ch) {
 		case 'b':
@@ -443,6 +490,10 @@ main(int argc, char **argv)
 			timeout = atoi(optarg);
 			break;
 		case 'I':
+			if (device) {
+				free(device);
+				device = NULL;
+			}
 			device = strdup(optarg);
 			break;
 		case 'f':