cangw: Print error message on misspelled interface

If can interface is misspelled or the kernel is configured without netlink
cangw displayed only generic usage instruction. Now, an appropriate error
message is displayed.

Signed-off-by: Michal Sojka <sojkam1@fel.cvut.cz>

diff --git a/cangw.c b/cangw.c
index ff76fd71b68a9c4c068aa214c627041c2802a7ca..f408993b235fd24563cc40e31d32bd451345dc07 100644 (file)
--- a/cangw.c
+++ b/cangw.c
@@ -602,10 +602,18 @@ int main(int argc, char **argv)
 
                case 's':
                        src_ifindex = if_nametoindex(optarg);
+                       if (src_ifindex == 0) {
+                               perror(optarg);
+                               return 1;
+                       }
                        break;
 
                case 'd':
                        dst_ifindex = if_nametoindex(optarg);
+                       if (dst_ifindex == 0) {
+                               perror(optarg);
+                               return 1;
+                       }
                        break;
 
                case 't':