Merge branch 'version3' of github.com:schweikert/fping into version3

ChangeLog

@@ -1,3 +1,6 @@
+Unreleased (version 3 branch)
+  * Fix compatibility issue with GNU Hurd
+
 2017-02-09  David Schweikert  <david@schweikert.ch>
   * Version 3.16
   * (feature) Support kernel-timestamping of received packets (#46)

src/fping.c

@@ -562,11 +562,17 @@ int main(int argc, char** argv)
             if (sscanf(optarg, "%i", &tos)) {
 #ifndef IPV6
                 if (setsockopt(s, IPPROTO_IP, IP_TOS, &tos, sizeof(tos))) {
+                    perror("setting type of service octet IP_TOS");
+                }
 #else
+#ifdef IPV6_TCLASS
                 if (setsockopt(s, IPPROTO_IPV6, IPV6_TCLASS, &tos, sizeof(tos))) {
-#endif
+                    perror("setting type of service octet IPV6_TCLASS");
-                    perror("setting type of service octet IP_TOS");
                 }
+#else
+                fprintf(stderr, "%s: -O (set TOS) for IPv6 not supported on this platform\n", prog);
+#endif
+#endif
             } else {
                 usage(1);
             }