1 files changed, 13 insertions, 2 deletions

diff --git a/plugins/check_ntp.c b/plugins/check_ntp.c
index 30e58900..18571184 100644
--- a/plugins/check_ntp.c
+++ b/plugins/check_ntp.c
@@ -507,6 +507,7 @@ double jitter_request(const char *host, int *status){
         int peers_size=0, peer_offset=0;
         ntp_assoc_status_pair *peers=NULL;
         ntp_control_message req;
+        const char *getvar = "jitter";
         double rval = 0.0, jitter = -1.0;
         char *startofvalue=NULL, *nptr=NULL;
         void *tmp;
@@ -584,8 +585,10 @@ double jitter_request(const char *host, int *status){
                                  * thus reducing net traffic, guaranteeing us only a single
                                  * datagram in reply, and making intepretation much simpler
                                  */
-                                strncpy(req.data, "jitter", 6);
-                                req.count = htons(6);
+                                /* Older servers doesn't know what jitter is, so if we get an
+                                 * error on the first pass we redo it with "dispersion" */
+                                strncpy(req.data, getvar, MAX_CM_SIZE-1);
+                                req.count = htons(strlen(getvar));
                                 DBG(printf("sending READVAR request...\n"));
                                 write(conn, &req, SIZEOF_NTPCM(req));
                                 DBG(print_ntp_control_message(&req));
@@ -595,6 +598,14 @@ double jitter_request(const char *host, int *status){
                                 read(conn, &req, SIZEOF_NTPCM(req));
                                 DBG(print_ntp_control_message(&req));
 
+                                if(req.op&REM_ERROR && strstr(getvar, "jitter")) {
+                                        if(verbose) printf("The 'jitter' command failed (old ntp server?)\nRestarting with 'dispersion'...\n");
+                                        getvar = "dispersion";
+                                        num_selected--;
+                                        i--;
+                                        continue;
+                                }
+
                                 /* get to the float value */
                                 if(verbose) {
                                         printf("parsing jitter from peer %.2x: ", ntohs(peers[i].assoc));