From 80daed0e7316fa466e5440a547e62e16ce993336 Mon Sep 17 00:00:00 2001
From: Luca <deri@ntop.org>
Date: Fri, 30 Dec 2016 01:48:27 +0100
Subject: [PATCH] Slow down DNS possling in case of no address to resolve

---
 src/AddressResolution.cpp | 10 ++++++++--
 1 file changed, 8 insertions(+), 2 deletions(-)

diff --git a/src/AddressResolution.cpp b/src/AddressResolution.cpp
index 8cb3d7b41e..123c797217 100644
--- a/src/AddressResolution.cpp
+++ b/src/AddressResolution.cpp
@@ -130,6 +130,8 @@ void AddressResolution::resolveHostName(char *_numeric_ip, char *symbolic, u_int
 static void* resolveLoop(void* ptr) {
   AddressResolution *a = (AddressResolution*)ptr;
   Redis *r = ntop->getRedis();
+  u_int no_resolution_loops = 0;
+  const u_int max_num_idle_loops = 3;
 
   while(!ntop->getGlobals()->isShutdown()) {
     char numeric_ip[64];
@@ -138,8 +140,12 @@ static void* resolveLoop(void* ptr) {
     if(rc == 0) {
       if(numeric_ip[0] != '\0')
 	a->resolveHostName(numeric_ip);
-    } else
-      sleep(1);    
+
+      no_resolution_loops = 0;
+    } else {
+      if(no_resolution_loops < max_num_idle_loops) no_resolution_loops++;
+      sleep(no_resolution_loops);
+    }
   }
 
   return(NULL);