utils: iftest: pass the device name you want to obtain information for

Instead of brute-force information extraction based on the device index.

 ./iftest eth0
 index (2) is eth0 (NOT RUNNING) (UP)

Signed-off-by: Pablo Neira Ayuso <pablo@netfilter.org>

1 files changed, 24 insertions, 13 deletions

diff --git a/utils/iftest.c b/utils/iftest.c
index 40825a3..63cf163 100644
--- a/utils/iftest.c
+++ b/utils/iftest.c
@@ -7,10 +7,17 @@
 
 #include <libnfnetlink/libnfnetlink.h>
 
-int main(void)
+int main(int argc, char *argv[])
 {
-	int i;
+	int idx;
 	struct nlif_handle *h;
+	char name[IFNAMSIZ];
+	unsigned int flags;
+
+	if (argc != 2) {
+		fprintf(stderr, "Usage: %s <interface>\n", argv[0]);
+		exit(EXIT_FAILURE);
+	}
 
 	h = nlif_open();
 	if (h == NULL) {
@@ -20,19 +27,23 @@ int main(void)
 
 	nlif_query(h);
 
-	for (i=0; i<64; i++) {
-		char name[IFNAMSIZ];
-		unsigned int flags;
-
-		if (nlif_index2name(h, i, name) == -1)
-			continue;
-		if (nlif_get_ifflags(h, i, &flags) == -1)
-			continue;
-		printf("index (%d) is %s (%s) (%s)\n", i, name,
-			flags & IFF_RUNNING ? "RUNNING" : "NOT RUNNING",
-			flags & IFF_UP ? "UP" : "DOWN");
+	idx = if_nametoindex(argv[1]);
+
+	/* Superfluous: just to make sure nlif_index2name is working fine */
+	if (nlif_index2name(h, idx, name) == -1) {
+		fprintf(stderr, "Cannot translate device idx=%u\n", idx);
+		exit(EXIT_FAILURE);
 	}
 
+	if (nlif_get_ifflags(h, idx, &flags) == -1) {
+		fprintf(stderr, "Cannot get flags for device `%s'\n", argv[1]);
+		exit(EXIT_FAILURE);
+	}
+
+	printf("index (%d) is %s (%s) (%s)\n", idx, argv[1],
+		flags & IFF_RUNNING ? "RUNNING" : "NOT RUNNING",
+		flags & IFF_UP ? "UP" : "DOWN");
+
 	nlif_close(h);
 	return EXIT_SUCCESS;
 }