Implement smb.conf(5) global option "trim default domain", which trims
the leading "DOMAIN\" in usernames looked up from the local passwd database;
this may be present with when security=domain or security=ads.

Setting smb.conf(5):
        security = ADS
        trim default domain = yes
        winbind use default domain = yes
allows "passwd: files winbind" in nsswitch.conf(5) to use /etc/passwd
("files") for username->UID mapping, falling back to a dynamic UID
from winbindd(8) ("winbind") for users only in ADS and not in /etc/passwd.

(The prior behaviour without this option was that smbd(8) tried to lookup
"DOMAIN\user" from /etc/passwd, not find it, and then lookup via winbindd(8),
and the latter will fake up an entry for DOMAIN\user.)

Index: auth/auth_util.c
===================================================================
--- auth/auth_util.c	8 Jul 2004 17:06:11 -0000	1.1.1.4
+++ auth/auth_util.c	28 Oct 2004 07:08:55 -0000
@@ -990,6 +990,19 @@ struct passwd *smb_getpwnam( char *domus
 	
 	if ( p ) {
 		fstring strip_username;
+		char oldsep;
+
+		/* if 'trim default domain' and the DOMAIN\ is the same
+		as the workgroup, don't lookup DOMAIN\ */
+		oldsep = *p;
+		*p = '\0';
+		if (lp_trim_default_domain()
+		    && strequal(lp_workgroup(), username)) {
+			DEBUG(7,("My domain -- skipping %s%c%s lookup\n", username, oldsep, p+1));
+			*p = oldsep;
+			goto trim_default_domain;
+		}
+		*p = oldsep;
 
 		pw = Get_Pwnam( domuser );
 		if ( pw ) {	
@@ -1008,10 +1021,12 @@ struct passwd *smb_getpwnam( char *domus
 			else
 				fstrcpy( save_username, pw->pw_name );
 
+			DEBUG(7,("Get_Pwnam domain user [%s] result [%s]\n", domuser, save_username));
 			/* whew -- done! */		
 			return pw;
 		}
 
+ trim_default_domain:
 		/* setup for lookup of just the username */
 		/* remember that p and username are overlapping memory */
 
@@ -1031,6 +1046,7 @@ struct passwd *smb_getpwnam( char *domus
 		if (username[strlen(username)-1] == '$')
 			return NULL;
 
+		DEBUG(7,("plain user not found, attempt to create\n"));
 		auth_add_user_script(NULL, username);
 		pw = Get_Pwnam(username);
 	}
@@ -1039,6 +1055,7 @@ struct passwd *smb_getpwnam( char *domus
 	
 	if ( pw )
 		fstrcpy( save_username, pw->pw_name );
+	DEBUG(7,("Get_Pwnam plain user [%s] result [%s]\n", username, save_username));
 
 	return pw;
 }
Index: param/loadparm.c
===================================================================
--- param/loadparm.c	12 Sep 2004 03:47:16 -0000	1.1.1.6
+++ param/loadparm.c	28 Oct 2004 07:09:00 -0000
@@ -288,6 +288,7 @@ typedef struct
 	BOOL bDisableNetbios;
 	BOOL bKernelChangeNotify;
 	BOOL bUseKerberosKeytab;
+	BOOL bTrimDefaultDomain;
 	BOOL bDeferSharingViolations;
 	int restrict_anonymous;
 	int name_cache_timeout;
@@ -867,6 +868,7 @@ static struct parm_struct parm_table[] =
 	{"deny hosts", P_LIST, P_LOCAL, &sDefault.szHostsdeny, NULL, NULL, FLAG_HIDE}, 
 	{"preload modules", P_LIST, P_GLOBAL, &Globals.szPreloadModules, NULL, NULL, FLAG_ADVANCED | FLAG_GLOBAL}, 
 	{"use kerberos keytab", P_BOOL, P_GLOBAL, &Globals.bUseKerberosKeytab, NULL, NULL, FLAG_ADVANCED}, 
+	{"trim default domain", P_BOOL, P_GLOBAL, &Globals.bTrimDefaultDomain, NULL, NULL, FLAG_ADVANCED},
 
 	{N_("Logging Options"), P_SEP, P_SEPARATOR}, 
 
@@ -1763,6 +1765,7 @@ FN_GLOBAL_BOOL(lp_client_use_spnego, &Gl
 FN_GLOBAL_BOOL(lp_hostname_lookups, &Globals.bHostnameLookups)
 FN_GLOBAL_BOOL(lp_kernel_change_notify, &Globals.bKernelChangeNotify)
 FN_GLOBAL_BOOL(lp_use_kerberos_keytab, &Globals.bUseKerberosKeytab)
+FN_GLOBAL_BOOL(lp_trim_default_domain, &Globals.bTrimDefaultDomain)
 FN_GLOBAL_BOOL(lp_defer_sharing_violations, &Globals.bDeferSharingViolations)
 FN_GLOBAL_INTEGER(lp_os_level, &Globals.os_level)
 FN_GLOBAL_INTEGER(lp_max_ttl, &Globals.max_ttl)