make fping fail if it cannot bind the interface (-I)

CHANGELOG.md

@@ -5,6 +5,7 @@ UNRELEASED
 
 - Corrected long option name of -s to --stats (#148, thanks @wopfel)
 - Do not fail if using fping6 with -6 flag (#149, thanks @stromnet)
+- Fail if interface binding (-I) does not work (by @kbucheli)
 
 fping 4.2 (2019-02-19)
 ======================

src/fping.c

@@ -658,12 +658,14 @@ int main(int argc, char** argv)
             if (socket4 >= 0) {
                 if (setsockopt(socket4, SOL_SOCKET, SO_BINDTODEVICE, optparse_state.optarg, strlen(optparse_state.optarg))) {
                     perror("binding to specific interface (SO_BINTODEVICE)");
+                    exit(1);
                 }
             }
 #ifdef IPV6
             if (socket6 >= 0) {
                 if (setsockopt(socket6, SOL_SOCKET, SO_BINDTODEVICE, optparse_state.optarg, strlen(optparse_state.optarg))) {
                     perror("binding to specific interface (SO_BINTODEVICE), IPV6");
+                    exit(1);
                 }
             }
 #endif