merge from APP_HEAD. Push negative connection cache

into rpc_find_dc().  Should probably be extended some more
in 3.0 but this is what we have for the moment.
(This used to be commit 0e23abf95cf7ba2d0a314a34bddb4d46de2a3cd1)

1 files changed, 148 insertions, 7 deletions

diff --git a/source3/libsmb/namequery_dc.c b/source3/libsmb/namequery_dc.c
index ffc64139e9..e98b728963 100644
--- a/source3/libsmb/namequery_dc.c
+++ b/source3/libsmb/namequery_dc.c
@@ -25,15 +25,149 @@
 #include "includes.h"
 
 
-/*
-  find the DC for a domain using methods appropriate for a RPC domain
-*/
+#define FAILED_CONNECTION_CACHE_TIMEOUT 30 /* Seconds between attempts */
+
+struct failed_connection_cache {
+	fstring domain_name;
+	fstring controller;
+	time_t lookup_time;
+	NTSTATUS nt_status;
+	struct failed_connection_cache *prev, *next;
+};
+
+static struct failed_connection_cache *failed_connection_cache;
+
+/**********************************************************************
+ Check for a previously failed connection
+**********************************************************************/
+
+static NTSTATUS check_negative_conn_cache( const char *domain, const char *server )
+{
+	struct failed_connection_cache *fcc;
+	NTSTATUS result = NT_STATUS_UNSUCCESSFUL;
+	
+	/* can't check if we don't have strings */
+	
+	if ( !domain || !server )
+		return NT_STATUS_OK;
+
+	for (fcc = failed_connection_cache; fcc; fcc = fcc->next) {
+		
+		/* 
+		 * we have a match IFF the domain and server name matches
+		 *   (a) the domain matches, 
+		 *   (b) the IP address matches (if we have one)
+		 *   (c) the server name (if specified) matches
+		 */
+		 
+		if ( !strequal(domain, fcc->domain_name) || !strequal(server, fcc->controller) )
+			continue; /* no match; check the next entry */
+		
+		/* we have a match so see if it is still current */
+
+		if ((time(NULL) - fcc->lookup_time) > FAILED_CONNECTION_CACHE_TIMEOUT) 
+		{
+			/* Cache entry has expired, delete it */
+
+			DEBUG(10, ("check_negative_conn_cache: cache entry expired for %s, %s\n", 
+				domain, server ));
+
+			DLIST_REMOVE(failed_connection_cache, fcc);
+			SAFE_FREE(fcc);
+
+			return NT_STATUS_OK;
+		}
+
+		/* The timeout hasn't expired yet so return false */
+
+		DEBUG(10, ("check_negative_conn_cache: returning negative entry for %s, %s\n", 
+			domain, server ));
+
+		result = fcc->nt_status;
+		return result;
+	}
+
+	/* end of function means no cache entry */	
+	return NT_STATUS_OK;
+}
+
+/**********************************************************************
+ Add an entry to the failed conneciton cache
+**********************************************************************/
+
+void add_failed_connection_entry(const char *domain, const char *server, NTSTATUS result) 
+{
+	struct failed_connection_cache *fcc;
+
+	SMB_ASSERT(!NT_STATUS_IS_OK(result));
+
+	/* Check we already aren't in the cache.  We always have to have 
+	   a domain, but maybe not a specific DC name. */
+
+	for (fcc = failed_connection_cache; fcc; fcc = fcc->next) {
+		if ( strequal(fcc->domain_name, domain) && strequal(fcc->controller, server) ) 
+		{
+			DEBUG(10, ("add_failed_connection_entry: domain %s (%s) already tried and failed\n",
+				   domain, server ));
+			return;
+		}
+	}
+
+	/* Create negative lookup cache entry for this domain and controller */
+
+	if ( !(fcc = (struct failed_connection_cache *)malloc(sizeof(struct failed_connection_cache))) ) 
+	{
+		DEBUG(0, ("malloc failed in add_failed_connection_entry!\n"));
+		return;
+	}
+	
+	ZERO_STRUCTP(fcc);
+	
+	fstrcpy( fcc->domain_name, domain );
+	fstrcpy( fcc->controller, server );
+	fcc->lookup_time = time(NULL);
+	fcc->nt_status = result;
+	
+	DEBUG(10,("add_failed_connection_entry: added domain %s (%s) to failed conn cache\n",
+		domain, server ));
+	
+	DLIST_ADD(failed_connection_cache, fcc);
+}
+
+/****************************************************************************
+****************************************************************************/
+ 
+void flush_negative_conn_cache( void )
+{
+	struct failed_connection_cache *fcc;
+	
+	fcc = failed_connection_cache;
+
+	while (fcc) {
+		struct failed_connection_cache *fcc_next;
+
+		fcc_next = fcc->next;
+		DLIST_REMOVE(failed_connection_cache, fcc);
+		free(fcc);
+
+		fcc = fcc_next;
+	}
+
+}
+
+/****************************************************************************
+ Utility function to return the name of a DC using RPC. The name is 
+ guaranteed to be valid since we have already done a name_status_find on it 
+ and we have checked our negative connection cache
+ ***************************************************************************/
+ 
 BOOL rpc_find_dc(const char *domain, fstring srv_name, struct in_addr *ip_out)
 {
 	struct in_addr *ip_list = NULL, dc_ip, exclude_ip;
 	int count, i;
 	BOOL list_ordered;
 	BOOL use_pdc_only;
+	NTSTATUS result;
 	
 	zero_ip(&exclude_ip);
 
@@ -41,11 +175,15 @@ BOOL rpc_find_dc(const char *domain, fstring srv_name, struct in_addr *ip_out)
 	
 	/* Lookup domain controller name */
 	   
-	if ( use_pdc_only && get_pdc_ip(domain, &dc_ip) ) {
+	if ( use_pdc_only && get_pdc_ip(domain, &dc_ip) ) 
+	{
 		DEBUG(10,("rpc_find_dc: Atempting to lookup PDC to avoid sam sync delays\n"));
 		
 		if (name_status_find(domain, 0x1c, 0x20, dc_ip, srv_name)) {
-			goto done;
+			/* makre we we haven't tried this on previously and failed */
+			result = check_negative_conn_cache( domain, srv_name );
+			if ( NT_STATUS_IS_OK(result) )
+				goto done;
 		}
 		/* Didn't get name, remember not to talk to this DC. */
 		exclude_ip = dc_ip;
@@ -77,8 +215,11 @@ BOOL rpc_find_dc(const char *domain, fstring srv_name, struct in_addr *ip_out)
 			continue;
 
 		if (name_status_find(domain, 0x1c, 0x20, ip_list[i], srv_name)) {
-			dc_ip = ip_list[i];
-			goto done;
+			result = check_negative_conn_cache( domain, srv_name );
+			if ( NT_STATUS_IS_OK(result) ) {
+				dc_ip = ip_list[i];
+				goto done;
+			}
 		}
 	}