Implemented asynchronous DNS lookups in nmbd.

I realised this afternoon just how easy it is to add this, so I
thought I'd implement it while the idea was fresh.

nmbd forks at startup and uses a pipe to talk to its child. The child
does the DNS lookups and the file descriptor of the child is added to
the main select loop.

While I was doing this I discovered a bug in nmbd that explains why
the dns proxy option has been so expensive. The DNS cache entries in
the WINS list were never being checked, which means we always did a
DNS lookup even if we have done it before and it is in cache. I'm sure
this used to work (I tested the DNS cache when I added it) so someone
broke it :-(

Anyway, the async DNS gets rid of the problem completely. I'll commit
just the fix to the DNS cache bug to the 1.9.17 tree.

You can disable async DNS by adding -DSYNC_DNS to the compile flags.
(This used to be commit 178e27de0791c1ff3268cb456ed5c5efc9ac2a01)

1 files changed, 5 insertions, 8 deletions

diff --git a/source3/nmbd/nmbd.c b/source3/nmbd/nmbd.c
index 047284832f..5feeb07c90 100644
--- a/source3/nmbd/nmbd.c
+++ b/source3/nmbd/nmbd.c
@@ -332,14 +332,6 @@ static void process(void)
 ****************************************************************************/
 static BOOL open_sockets(BOOL isdaemon, int port)
 {
-  struct hostent *hp;
- 
-  /* get host info */
-  if ((hp = Get_Hostbyname(myhostname)) == 0) {
-    DEBUG(0,( "Get_Hostbyname: Unknown host. %s\n",myhostname));
-    return False;
-  }   
-
   /* The sockets opened here will be used to receive broadcast
      packets *only*. Interface specific sockets are opened in
      make_subnet() in namedbsubnet.c. Thus we bind to the
@@ -598,6 +590,10 @@ static void usage(char *pname)
     become_daemon();
   }
 
+#ifndef SYNC_DNS
+  start_async_dns();
+#endif
+
   if (*pidFile)
     {
       int     fd;
@@ -653,6 +649,7 @@ static void usage(char *pname)
 
   /* We can only take sigterm signals in the select. */
   BlockSignals(True,SIGTERM);
+
   process();
   close_sockets();