File glibc-resolv-reload.diff of Package glibc.8004

Overview Repositories Revisions Requests Users Attributes Meta

File glibc-resolv-reload.diff of Package glibc.8004

From libc-alpha-return-22754-pasky=ucw.cz@sourceware.org  Tue Mar 16 00:47:00 2010
Return-Path: <libc-alpha-return-22754-pasky=ucw.cz@sourceware.org>
X-Original-To: pasky@pasky.or.cz
Delivered-To: pasky@pasky.or.cz
Received: from nikam.ms.mff.cuni.cz (nikam-dmz.ms.mff.cuni.cz [195.113.20.16])
	by machine.or.cz (Postfix) with ESMTPS id C1B8586202A
	for <pasky@pasky.or.cz>; Tue, 16 Mar 2010 00:47:00 +0100 (CET)
Received: by nikam.ms.mff.cuni.cz (Postfix)
	id 9CDEC9AC7A4; Tue, 16 Mar 2010 00:47:00 +0100 (CET)
Delivered-To: pasky@kam.mff.cuni.cz
Received: from jabberwock.ucw.cz (jabberwock.ucw.cz [89.250.246.4])
	by nikam.ms.mff.cuni.cz (Postfix) with ESMTP id 99F0E9AC77B
	for <pasky@kam.mff.cuni.cz>; Tue, 16 Mar 2010 00:47:00 +0100 (CET)
Received: from sourceware.org (server1.sourceware.org [209.132.180.131])
	by jabberwock.ucw.cz (Postfix) with SMTP id 14E1ACF040
	for <pasky@ucw.cz>; Tue, 16 Mar 2010 00:46:59 +0100 (CET)
Received: (qmail 18956 invoked by alias); 15 Mar 2010 23:46:58 -0000
Delivered-To: moderator for libc-alpha@sourceware.org
Received: (qmail 15843 invoked by uid 22791); 15 Mar 2010 17:23:15 -0000
X-SWARE-Spam-Status: No, hits=-2.6 required=5.0
	tests=BAYES_00
X-Spam-Check-By: sourceware.org
Message-ID: <4B9E6CFA.7020002@riot.org>
Date: Mon, 15 Mar 2010 18:23:06 +0100
From: Sebastian Kienzl <seb@riot.org>
User-Agent: Thunderbird 2.0.0.23 (Windows/20090812)
MIME-Version: 1.0
To: libc-alpha@sourceware.org
Subject: Reloading of /etc/resolv.conf
Content-Type: multipart/mixed;
 boundary="------------060407080409020101000002"
Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm
Precedence: bulk
List-Id: <libc-alpha.sourceware.org>
List-Unsubscribe: <mailto:libc-alpha-unsubscribe-pasky=ucw.cz@sourceware.org>
List-Subscribe: <mailto:libc-alpha-subscribe@sourceware.org>
List-Archive: <http://sourceware.org/ml/libc-alpha/>
List-Post: <mailto:libc-alpha@sourceware.org>
List-Help: <mailto:libc-alpha-help@sourceware.org>, <http://sourceware.org/ml/#faqs>
Sender: libc-alpha-owner@sourceware.org
Delivered-To: mailing list libc-alpha@sourceware.org

This is a multi-part message in MIME format.
--------------060407080409020101000002
Content-Type: text/plain; charset=ISO-8859-15; format=flowed
Content-Transfer-Encoding: 7bit

Hello!

There's a patch in the wild against the resolver which makes it reload
/etc/resolv.conf on change, see
http://sources.redhat.com/ml/libc-alpha/2004-09/msg00130.html

However, this patch actually doesn't work properly for multi-threaded
programs, as only one thread will notice the change and refresh its
resolver state. I've attached a proper patch. It's for 2.5 but it should
work with current versions, too.

Even though the patch may not be interesting for upstream, I decided to
let you know about this problem, since the mentioned patch seems to be
used by at least Debian and Ubuntu.

Regards,
Seb.

--------------060407080409020101000002
Content-Type: text/plain;
 name="glibc-2.5-resolvconf.patch"
Content-Transfer-Encoding: 7bit
Content-Disposition: inline;
 filename="glibc-2.5-resolvconf.patch"

Index: glibc-2.17.90/resolv/res_libc.c
===================================================================
--- glibc-2.17.90.orig/resolv/res_libc.c
+++ glibc-2.17.90/resolv/res_libc.c
@@ -22,7 +22,7 @@
 #include <arpa/nameser.h>
 #include <resolv.h>
 #include <bits/libc-lock.h>
-
+#include <sys/stat.h>
 
 /* The following bit is copied from res_data.c (where it is #ifdef'ed
    out) since res_init() should go into libc.so but the rest of that
@@ -89,12 +89,34 @@ res_init(void) {
 	return (__res_vinit(&_res, 1));
 }
 
+static time_t resconf_mtime;
+__libc_lock_define_initialized (static, resconf_mtime_lock);
+
+/* Check if the modification time of resolv.conf has changed.
+   If so, have all threads re-initialize their resolver states */
+static void
+__res_check_resconf (void)
+{
+	struct stat statbuf;
+	if (stat (_PATH_RESCONF, &statbuf) == 0) {
+		__libc_lock_lock (resconf_mtime_lock);
+		if (statbuf.st_mtime != resconf_mtime) {
+			resconf_mtime = statbuf.st_mtime;
+			atomicinclock (lock);
+			atomicinc (__res_initstamp);
+			atomicincunlock (lock);
+		}
+		__libc_lock_unlock (resconf_mtime_lock);
+	}
+}
+
 /* Initialize resp if RES_INIT is not yet set or if res_init in some other
    thread requested re-initializing.  */
 int
 __res_maybe_init (res_state resp, int preinit)
 {
 	if (resp->options & RES_INIT) {
+		__res_check_resconf ();
 		if (__res_initstamp != resp->_u._ext.initstamp) {
 			if (resp->nscount > 0)
 				__res_iclose (resp, true);

Places

File glibc-resolv-reload.diff of Package glibc.8004

Places