From owner-freebsd-net@FreeBSD.ORG Thu Nov 2 14:25:52 2006 Return-Path: X-Original-To: freebsd-net@freebsd.org Delivered-To: freebsd-net@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id DBA1B16A494 for ; Thu, 2 Nov 2006 14:25:52 +0000 (UTC) (envelope-from brooks@lor.one-eyed-alien.net) Received: from sccmmhc91.asp.att.net (sccmmhc91.asp.att.net [204.127.203.211]) by mx1.FreeBSD.org (Postfix) with ESMTP id 05F2243D53 for ; Thu, 2 Nov 2006 14:25:51 +0000 (GMT) (envelope-from brooks@lor.one-eyed-alien.net) Received: from lor.one-eyed-alien.net ([12.207.12.9]) by sccmmhc91.asp.att.net (sccmmhc91) with ESMTP id <20061102142550m9100ekn5ge>; Thu, 2 Nov 2006 14:25:50 +0000 Received: from lor.one-eyed-alien.net (localhost [127.0.0.1]) by lor.one-eyed-alien.net (8.13.8/8.13.8) with ESMTP id kA2EPm1W071399; Thu, 2 Nov 2006 08:25:48 -0600 (CST) (envelope-from brooks@lor.one-eyed-alien.net) Received: (from brooks@localhost) by lor.one-eyed-alien.net (8.13.8/8.13.8/Submit) id kA2EPhBX071398; Thu, 2 Nov 2006 08:25:43 -0600 (CST) (envelope-from brooks) Date: Thu, 2 Nov 2006 08:25:43 -0600 From: Brooks Davis To: "." Message-ID: <20061102142543.GC70915@lor.one-eyed-alien.net> References: Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="kfjH4zxOES6UT95V" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.11 Cc: freebsd-net@freebsd.org Subject: Re: Reentrant problem with inet_ntoa in the kernel X-BeenThere: freebsd-net@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Networking and TCP/IP with FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 02 Nov 2006 14:25:52 -0000 --kfjH4zxOES6UT95V Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Thu, Nov 02, 2006 at 08:26:27AM +0000, . wrote: > Hi, >=20 > I am confused by the use of inet_ntoa function in the kernel. >=20 > The function inet_ntoa in the /sys/libkern/inet_ntoa.c uses a static array > static char buf[4 * sizeof "123"]; > to store the result. And it returns the address of the array to the calle= r. >=20 > I think this inet_ntoa is not reentrant, though there are several functio= ns > calling it. If two functions call it simultaneously, the result will be > corrupted. Though I haven't really encountered this situation, it may occ= ur > someday, especially when using multi-processors. >=20 > There is another reentrant version of inet_ntoa called inet_ntoa_r in the > same file. It has been there for several years, but just used by ipfw2 for > about four times in 7-CURRENT. In my patch, I replaced all the calls to > inet_ntoa with calls to inet_ntoa_r. >=20 > By the way, some of the original calls is written in this style: > strcpy(buf, inet_ntoa(ip)) > The modified code is written in this style > inet_ntoa_r(ip, buf) > This change avoids a call to strcpy, and can save a little time. >=20 > Here is the patch. > http://people.freebsd.org/~delphij/misc/patch-itoa-by-nodummy-at-yeah-net >=20 > I've already sent to PR(kern/104738), but got no reply, maybe it should be > discussed here first? I've got to agree with other posters that the stack variable allocations are ugly. What about extending log and printf to understand ip4v addresses? That's 90% of the uses and the others appears to have buffers already. -- Brooks --kfjH4zxOES6UT95V Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.5 (FreeBSD) iD8DBQFFSf/mXY6L6fI4GtQRAq3/AKCzT92xeif23vFSDc2k1b3ZpFdolACgx8n6 da2TOJtPJpXc2Q3N9Ih7Ju0= =GyRC -----END PGP SIGNATURE----- --kfjH4zxOES6UT95V--