Improve handling of -4/-6

If fping is used with a target that has dual stack v4/v6, then due to
the logic during command construction, ipv4 will never be checked as v6
is preferred by fping.

This explicitly flags -4/-6 when it is requested by the user.

1 files changed, 22 insertions, 11 deletions

diff --git a/plugins/check_fping.c b/plugins/check_fping.c
index ec7abb67..1c2b7689 100644
--- a/plugins/check_fping.c
+++ b/plugins/check_fping.c
@@ -79,7 +79,29 @@ int main(int argc, char **argv) {
         server = strscpy(server, config.server_name);
 
         char *option_string = "";
+        char *fping_prog = NULL;
+
         /* compose the command */
+#ifdef PATH_TO_FPING6
+        if (address_family != AF_INET && is_inet6_addr(server)) {
+                fping_prog = strdup(PATH_TO_FPING6);
+        } else {
+                xasprintf(&option_string, "%s-4 ", option_string);
+                fping_prog = strdup(PATH_TO_FPING);
+        }
+#else
+        if (address_family != AF_INET) {
+                // -4 / -6 must be set explicitly as when a host has dual stack
+                // if we don't specify -4 then fping selects ipv6 which can mess
+                // with some checks.
+                xasprintf(&option_string, "%s-6 ", option_string);
+        } else {
+                xasprintf(&option_string, "%s-4 ", option_string);
+        }
+
+        fping_prog = strdup(PATH_TO_FPING);
+#endif
+
         if (config.target_timeout) {
                 xasprintf(&option_string, "%s-t %d ", option_string, config.target_timeout);
         }
@@ -99,17 +121,6 @@ int main(int argc, char **argv) {
                 xasprintf(&option_string, "%s-R ", option_string);
         }
 
-        char *fping_prog = NULL;
-#ifdef PATH_TO_FPING6
-        if (address_family != AF_INET && is_inet6_addr(server)) {
-                fping_prog = strdup(PATH_TO_FPING6);
-        } else {
-                fping_prog = strdup(PATH_TO_FPING);
-        }
-#else
-        fping_prog = strdup(PATH_TO_FPING);
-#endif
-
         char *command_line = NULL;
         xasprintf(&command_line, "%s %s-b %d -c %d %s", fping_prog, option_string, config.packet_size, config.packet_count, server);