s3: Cache results of finding printer names

With hundreds of printers or on a slow machine, this can become expensive.

Problem reported and patch sponsored by DESY, Hamburg (www.desy.de)

1 files changed, 39 insertions, 0 deletions

diff --git a/source3/rpc_server/srv_spoolss_nt.c b/source3/rpc_server/srv_spoolss_nt.c
index 5df20d4f08..4e97122736 100644
--- a/source3/rpc_server/srv_spoolss_nt.c
+++ b/source3/rpc_server/srv_spoolss_nt.c
@@ -470,6 +470,14 @@ static bool set_printer_hnd_name(TALLOC_CTX *mem_ctx,
 	struct spoolss_PrinterInfo2 *info2 = NULL;
 	WERROR result;
 
+	/*
+	 * Hopefully nobody names his printers like this. Maybe \ or ,
+	 * are illegal in printer names even?
+	 */
+	const char printer_not_found[] = "Printer \\, !@#$%^&*( not found";
+	char *cache_key;
+	char *tmp;
+
 	DEBUG(4,("Setting printer name=%s (len=%lu)\n", handlename,
 		(unsigned long)strlen(handlename)));
 
@@ -509,6 +517,27 @@ static bool set_printer_hnd_name(TALLOC_CTX *mem_ctx,
 		found = true;
 	}
 
+	/*
+	 * With hundreds of printers, the "for" loop iterating all
+	 * shares can be quite expensive, as it is done on every
+	 * OpenPrinter. The loop maps "aprinter" to "sname", the
+	 * result of which we cache in gencache.
+	 */
+
+	cache_key = talloc_asprintf(talloc_tos(), "PRINTERNAME/%s",
+				    aprinter);
+	if ((cache_key != NULL) && gencache_get(cache_key, &tmp, NULL)) {
+
+		found = (strcmp(tmp, printer_not_found) != 0);
+		if (!found) {
+			DEBUG(4, ("Printer %s not found\n", aprinter));
+			SAFE_FREE(tmp);
+			return false;
+		}
+		fstrcpy(sname, tmp);
+		SAFE_FREE(tmp);
+	}
+
 	/* Search all sharenames first as this is easier than pulling
 	   the printer_info_2 off of disk. Don't use find_service() since
 	   that calls out to map_username() */
@@ -569,10 +598,20 @@ static bool set_printer_hnd_name(TALLOC_CTX *mem_ctx,
 	}
 
 	if ( !found ) {
+		if (cache_key != NULL) {
+			gencache_set(cache_key, printer_not_found,
+				     time(NULL)+300);
+			TALLOC_FREE(cache_key);
+		}
 		DEBUGADD(4,("Printer not found\n"));
 		return false;
 	}
 
+	if (cache_key != NULL) {
+		gencache_set(cache_key, sname, time(NULL)+300);
+		TALLOC_FREE(cache_key);
+	}
+
 	DEBUGADD(4,("set_printer_hnd_name: Printer found: %s -> %s\n", aprinter, sname));
 
 	fstrcpy(Printer->sharename, sname);