[syslog-ng] Bug in 2.0.7's use_dns(persist_only) and large host files

[Balazs Scheidler]

On Sun, 2008-01-27 at 14:25 -0500, Steve Bernacki wrote:
> Environment:  CentOS 5 and Syslog-ng 2.0.7 (current snapshot)
> Relevant syslog-ng.conf snippet:
> ===
> options {
>          use_dns(persist_only);
>          dns_cache_hosts("/etc/hosts");
> };
> ===
> 
> If you point syslog-ng to an /etc/hosts file that has more than 1007 
> entries, upon receiving its first message, syslog-ng will throw the 
> following assertion:
> 
> # ./syslog-ng -Fed
> syslog-ng starting up; version='2.0.7'
> Incoming log entry; line='<38>well hello'
> file dnscache.c: line 99 (dns_cache_key_hash): should not be reached
> Aborted
> 
> Workaround:   In syslog-ng.conf, set dns_cache_size() to a value greater 
> than the number of entries in your /etc/hosts file.

Thanks for the bug report and the fix.

What do you think about this patch instead?


diff --git a/src/dnscache.c b/src/dnscache.c
index 097af48..f64ec53 100644
--- a/src/dnscache.c
+++ b/src/dnscache.c
@@ -62,6 +62,7 @@ static DNSCacheEntry cache_first, cache_last, persist_first, persist_last;
 static gint dns_cache_size = 1007;
 static gint dns_cache_expire = 3600;
 static gint dns_cache_expire_failed = 60;
+static gint dns_cache_persistent_count = 0;
 static gchar *dns_cache_hosts = NULL;
 static time_t dns_cache_hosts_mtime = -1;
 
@@ -146,6 +147,7 @@ dns_cache_cleanup_persistent_hosts(void)
   while (persist_first.next != &persist_last)
     {
       g_hash_table_remove(cache, &persist_first.next->key);
+      dns_cache_persistent_count--;
     }
 }
 
@@ -266,12 +268,14 @@ dns_cache_store(gboolean persistent, gint family, void *addr, const gchar *hostn
     }
   else
     {
+      dns_cache_persistent_count++;
       entry->resolved = 0;
       dns_cache_entry_insert_before(&persist_last, entry);
     }
   g_hash_table_replace(cache, &entry->key, entry);
   
-  if (g_hash_table_size(cache) > dns_cache_size)
+  /* persistent elements are not counted */
+  if (g_hash_table_size(cache) - dns_cache_persistent_count > dns_cache_size)
     {
       /* remove oldest element */
       g_hash_table_remove(cache, &cache_first.next->key);



-- 
Bazsi