Fix DNS failure of cachesize set to zero.

CHANGELOG

@@ -11,6 +11,10 @@ version 2.71
 	    Fix DNSSEC validation of ANY queries. Thanks to Marco Davids
 	    for spotting that too.
 
+	    Fix total DNS failure and 100% CPU use if cachesize set to zero,
+	    regression introduced in 2.69. Thanks to James Hunt and
+	    the Ubuntu crowd for assistance in fixing this.
+
 
 version 2.70
             Fix crash, introduced in 2.69, on TCP request when dnsmasq

src/blockdata.c

@@ -25,7 +25,7 @@ static void blockdata_expand(int n)
 {
   struct blockdata *new = whine_malloc(n * sizeof(struct blockdata));
   
-  if (new)
+  if (n > 0 && new)
     {
       int i;
       
@@ -47,13 +47,18 @@ void blockdata_init(void)
   blockdata_count = 0;
   blockdata_hwm = 0;
 
+  /* Note that daemon->cachesize is enforced to have non-zero size if OPT_DNSSEC_VALID is set */  
+  if (option_bool(OPT_DNSSEC_VALID))
     blockdata_expand((daemon->cachesize * 100) / sizeof(struct blockdata));
 }
 
 void blockdata_report(void)
 {
+  if (option_bool(OPT_DNSSEC_VALID))
     my_syslog(LOG_INFO, _("DNSSEC memory in use %u, max %u, allocated %u"), 
-	    blockdata_count * sizeof(struct blockdata),  blockdata_hwm * sizeof(struct blockdata),  blockdata_alloced * sizeof(struct blockdata));
+	      blockdata_count * sizeof(struct blockdata),  
+	      blockdata_hwm * sizeof(struct blockdata),  
+	      blockdata_alloced * sizeof(struct blockdata));
 } 
 
 struct blockdata *blockdata_alloc(char *data, size_t len)