monitoring-plugins/0001-Backport-fping-MTU-and-ipv4-6-handling-improvements.patch

From 4b56fd1bb0c145cee5289ba8f76d8f5f1dfa9460 Mon Sep 17 00:00:00 2001
From: William <william@blackhats.net.au>
Date: Fri, 28 Mar 2025 11:08:03 +1000
Subject: [PATCH] Backport fping MTU and ipv4/6 handling improvements

---
 plugins/check_fping.c | 55 +++++++++++++++++++++++++++++++++----------
 1 file changed, 43 insertions(+), 12 deletions(-)

diff --git a/plugins/check_fping.c b/plugins/check_fping.c
index 70d6f9fc..0ff48b14 100644
--- a/plugins/check_fping.c
+++ b/plugins/check_fping.c
@@ -55,6 +55,9 @@ void print_usage (void);
 char *server_name = NULL;
 char *sourceip = NULL;
 char *sourceif = NULL;
+bool randomize_packet_data = false;
+bool dontfrag = false;
+
 int packet_size = PACKET_SIZE;
 int packet_count = PACKET_COUNT;
 int target_timeout = 0;
@@ -96,6 +99,25 @@ main (int argc, char **argv)
 
   server = strscpy (server, server_name);
 
+#ifdef PATH_TO_FPING6
+  if (address_family == AF_INET6 || (address_family == AF_UNSPEC && 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_INET6 || (address_family == AF_UNSPEC && is_inet6_addr(server))) {
+    // -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
+
   /* compose the command */
   if (target_timeout)
     xasprintf(&option_string, "%s-t %d ", option_string, target_timeout);
@@ -105,15 +127,12 @@ main (int argc, char **argv)
     xasprintf(&option_string, "%s-S %s ", option_string, sourceip);
   if (sourceif)
     xasprintf(&option_string, "%s-I %s ", option_string, sourceif);
-
-#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
+  if (dontfrag) {
+    xasprintf(&option_string, "%s-M ", option_string);
+  }
+  if (randomize_packet_data) {
+    xasprintf(&option_string, "%s-R ", option_string);
+  }
 
   xasprintf (&command_line, "%s %s-b %d -c %d %s", fping_prog,
             option_string, packet_size, packet_count, server);
@@ -293,7 +312,7 @@ process_arguments (int argc, char **argv)
     {"sourceif", required_argument, 0, 'I'},
     {"critical", required_argument, 0, 'c'},
     {"warning", required_argument, 0, 'w'},
-	{"alive", no_argument, 0, 'a'},
+    {"alive", no_argument, 0, 'a'},
     {"bytes", required_argument, 0, 'b'},
     {"number", required_argument, 0, 'n'},
     {"target-timeout", required_argument, 0, 'T'},
@@ -303,6 +322,8 @@ process_arguments (int argc, char **argv)
     {"help", no_argument, 0, 'h'},
     {"use-ipv4", no_argument, 0, '4'},
     {"use-ipv6", no_argument, 0, '6'},
+    {"dontfrag", no_argument, 0, 'M'},
+    {"random", no_argument, 0, 'R'},
     {0, 0, 0, 0}
   };
 
@@ -320,7 +341,7 @@ process_arguments (int argc, char **argv)
   }
 
   while (1) {
-    c = getopt_long (argc, argv, "+hVvaH:S:c:w:b:n:T:i:I:46", longopts, &option);
+    c = getopt_long (argc, argv, "+hVvaH:S:c:w:b:n:T:i:I:M:R:46", longopts, &option);
 
     if (c == -1 || c == EOF || c == 1)
       break;
@@ -354,7 +375,7 @@ process_arguments (int argc, char **argv)
       break;
     case 'I':                 /* sourceip */
       sourceif = strscpy (sourceif, optarg);
-			break;
+      break;
     case '4':                 /* IPv4 only */
       address_family = AF_INET;
       break;
@@ -415,6 +436,12 @@ process_arguments (int argc, char **argv)
       else
         usage (_("Interval must be a positive integer"));
       break;
+    case 'R':
+      randomize_packet_data = true;
+      break;
+    case 'M':
+      dontfrag = true;
+      break;
     }
   }
 
@@ -506,6 +533,10 @@ void print_help (void) {
   printf ("    %s\n", _("name or IP Address of sourceip"));
   printf (" %s\n", "-I, --sourceif=IF");
   printf ("    %s\n", _("source interface name"));
+  printf(" %s\n", "-M, --dontfrag");
+  printf("    %s\n", _("set the Don't Fragment flag"));
+  printf(" %s\n", "-R, --random");
+  printf("    %s\n", _("random packet data (to foil link data compression)"));
   printf (UT_VERBOSE);
   printf ("\n");
   printf (" %s\n", _("THRESHOLD is <rta>,<pl>%% where <rta> is the round trip average travel time (ms)"));
-- 
2.48.1