Fix race condition with ultra low latency links

dpinger.c

@@ -354,12 +354,12 @@ send_thread(
         sched_yield();
         clock_gettime(CLOCK_MONOTONIC, &array[next_slot].time_sent);
 
+        array[next_slot].status = PACKET_STATUS_SENT;
         len = sendto(send_sock, echo_request, echo_request_len, 0, (struct sockaddr *) &dest_addr, dest_addr_len);
         if (len == -1)
         {
             logger("%s%s: sendto error: %d\n", identifier, dest_str, errno);
         }
-        array[next_slot].status = PACKET_STATUS_SENT;
 
         next_slot = (next_slot + 1) % array_size;
         next_sequence = (next_sequence + 1) % sequence_limit;

rrd/dpinger_rrd_create

@@ -10,10 +10,21 @@ name="$1"
 rrdfile="${name}.rrd"
 echo "Creating rrd file ${rrdfile}"
 
-rrdtool create "${rrdfile}" --step 1m \
-    DS:latency:GAUGE:5m:0:U \
-    DS:stddev:GAUGE:5m:0:U \
-    DS:loss:GAUGE:5m:0:100 \
-    RRA:AVERAGE:0.5:1m:15d \
-    RRA:AVERAGE:0.5:5m:90d \
-    RRA:AVERAGE:0.5:1h:3y
+
+# Time duration method doesn't work in all versions of rrdtool
+#rrdtool create "${rrdfile}" --step 1m \
+#    DS:latency:GAUGE:5m:0:U \
+#    DS:stddev:GAUGE:5m:0:U \
+#    DS:loss:GAUGE:5m:0:100 \
+#    RRA:AVERAGE:0.5:1m:15d \
+#    RRA:AVERAGE:0.5:5m:90d \
+#    RRA:AVERAGE:0.5:1h:3y
+
+# This method works in all versions
+rrdtool create "${rrdfile}" --step 60 \
+    DS:latency:GAUGE:300:0:U \
+    DS:stddev:GAUGE:300:0:U \
+    DS:loss:GAUGE:300:0:100 \
+    RRA:AVERAGE:0.5:1:21600 \
+    RRA:AVERAGE:0.5:5:25920 \
+    RRA:AVERAGE:0.5:60:26352