From owner-freebsd-current@FreeBSD.ORG Tue Sep 23 09:41:47 2008 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2001:4f8:fff6::34]) by hub.freebsd.org (Postfix) with ESMTP id D8165106564A for ; Tue, 23 Sep 2008 09:41:47 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from mail.terabit.net.ua (mail.terabit.net.ua [195.137.202.147]) by mx1.freebsd.org (Postfix) with ESMTP id 71B1B8FC1A for ; Tue, 23 Sep 2008 09:41:47 +0000 (UTC) (envelope-from kostikbel@gmail.com) Received: from skuns.zoral.com.ua ([91.193.166.194] helo=mail.zoral.com.ua) by mail.terabit.net.ua with esmtp (Exim 4.63 (FreeBSD)) (envelope-from ) id 1Ki4Ou-0004JM-Hp; Tue, 23 Sep 2008 12:41:44 +0300 Received: from deviant.kiev.zoral.com.ua (root@deviant.kiev.zoral.com.ua [10.1.1.148]) by mail.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m8N9fZZv036972 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Tue, 23 Sep 2008 12:41:35 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: from deviant.kiev.zoral.com.ua (kostik@localhost [127.0.0.1]) by deviant.kiev.zoral.com.ua (8.14.2/8.14.2) with ESMTP id m8N9fYqn098618; Tue, 23 Sep 2008 12:41:34 +0300 (EEST) (envelope-from kostikbel@gmail.com) Received: (from kostik@localhost) by deviant.kiev.zoral.com.ua (8.14.3/8.14.3/Submit) id m8N9fYIP098617; Tue, 23 Sep 2008 12:41:34 +0300 (EEST) (envelope-from kostikbel@gmail.com) X-Authentication-Warning: deviant.kiev.zoral.com.ua: kostik set sender to kostikbel@gmail.com using -f Date: Tue, 23 Sep 2008 12:41:34 +0300 From: Kostik Belousov To: Maksim Yevmenkin Message-ID: <20080923094134.GM47828@deviant.kiev.zoral.com.ua> References: <48D2F942.4070801@FreeBSD.org> <20080919084201.GD44330@wep4035.physik.uni-wuerzburg.de> <48D38DFF.8000803@FreeBSD.org> <20080919203310.GA34131@localhost.my.domain> <48D8196E.7020005@FreeBSD.org> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="V3eawNQxI9TAjvgi" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.4.2.3i X-Virus-Scanned: ClamAV version 0.93.3, clamav-milter version 0.93.3 on skuns.kiev.zoral.com.ua X-Virus-Status: Clean X-Spam-Status: No, score=-4.4 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 autolearn=ham version=3.2.5 X-Spam-Checker-Version: SpamAssassin 3.2.5 (2008-06-10) on skuns.kiev.zoral.com.ua X-Virus-Scanned: mail.terabit.net.ua 1Ki4Ou-0004JM-Hp 9ac6fc9ab56feaebec872ff7368f43df X-Terabit: YES Cc: Alexey Shuvaev , freebsd-current@freebsd.org, Ed Schouten Subject: Re: Interface auto-cloning bug or feature? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 23 Sep 2008 09:41:47 -0000 --V3eawNQxI9TAjvgi Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Mon, Sep 22, 2008 at 06:49:14PM -0700, Maksim Yevmenkin wrote: > [...] >=20 > >>> ok, how about attached patch. i put it together *very* quickly and > >>> only gave it a light testing. its for tap(4), because i could compile > >>> it as a module and tun(4) is compiled into kernel by default, but the > >>> idea should identical for tun(4). should be even simpler for tun(4) > >>> because it does not have to deal with 2 kind of devices (i.e. tap and > >>> vmnet). give it a try, and see if it works. please try both cloning > >>> paths, i.e. > >>> > >>> 1) cat /dev/tap (/dev/vmnet) with and/or without unit number > >>> > >>> and > >>> > >>> 2) ifconfig tapX (vmnetX) create/destroy > >>> > >>> in the mean time i will prepare something similar for tun(4). > >> > >> attached is similar patch for tun(4). i only made sure it compiles :) > >> rebuilding kernel now... >=20 > attached is a slightly better patch for tap(4). the idea is to use > extra ALLOCATED flag that prevents the race Kostik pointed out. could > you please give it a try? any review comments are greatly appreciated. > if this is acceptable, i will prepare something similar for tun(4) The tap should use make_dev_credf(MAKEDEV_REF) instead of make_dev/dev_ref sequence in the clone handler. For similar reasons, I think it is slightly better to do a dev_ref() immediately after setting the TAP_ALLOCATED flag without dropping tapmtx. I cannot figure out how tap_clone_create/tap_clone_destroy are being called. Can it be garbage-collected ? The whole module unload sequence looks unsafe. >=20 > thanks, > max > --- if_tap.c.orig 2008-09-08 17:20:57.000000000 -0700 > +++ if_tap.c 2008-09-22 18:36:16.000000000 -0700 > @@ -94,6 +94,7 @@ > static int tapifioctl(struct ifnet *, u_long, caddr_t); > static void tapifinit(void *); > =20 > +static int tap_clone_lookup(struct cdev **, u_short); > static int tap_clone_create(struct if_clone *, int, caddr_t); > static void tap_clone_destroy(struct ifnet *); > static int vmnet_clone_create(struct if_clone *, int, caddr_t); > @@ -176,6 +177,30 @@ > DEV_MODULE(if_tap, tapmodevent, NULL); > =20 > static int > +tap_clone_lookup(struct cdev **dev, u_short extra) > +{ > + struct tap_softc *tp; > + > + mtx_lock(&tapmtx); > + SLIST_FOREACH(tp, &taphead, tap_next) { > + mtx_lock(&tp->tap_mtx); > + > + if ((tp->tap_flags & (TAP_OPEN|TAP_ALLOCATED|extra)) =3D=3D extra) { > + tp->tap_flags |=3D TAP_ALLOCATED; > + *dev =3D tp->tap_dev; > + mtx_unlock(&tp->tap_mtx); > + mtx_unlock(&tapmtx); > + > + return (1); > + } > + mtx_unlock(&tp->tap_mtx); > + } > + mtx_unlock(&tapmtx); > + > + return (0); > +} > + > +static int > tap_clone_create(struct if_clone *ifc, int unit, caddr_t params) > { > struct cdev *dev; > @@ -288,7 +313,7 @@ > mtx_lock(&tapmtx); > SLIST_FOREACH(tp, &taphead, tap_next) { > mtx_lock(&tp->tap_mtx); > - if (tp->tap_flags & TAP_OPEN) { > + if (tp->tap_flags & (TAP_OPEN|TAP_ALLOCATED)) { > mtx_unlock(&tp->tap_mtx); > mtx_unlock(&tapmtx); > return (EBUSY); > @@ -353,8 +378,18 @@ > =20 > /* We're interested in only tap/vmnet devices. */ > if (strcmp(name, TAP) =3D=3D 0) { > + if (tap_clone_lookup(dev, 0)) { > + dev_ref(*dev); > + return; > + } > + > unit =3D -1; > } else if (strcmp(name, VMNET) =3D=3D 0) { > + if (tap_clone_lookup(dev, TAP_VMNET)) { > + dev_ref(*dev); > + return; > + } > + > unit =3D -1; > extra =3D VMNET_DEV_MASK; > } else if (dev_stdclone(name, NULL, TAP, &unit) !=3D 1) { > @@ -559,12 +594,11 @@ > KNOTE_UNLOCKED(&tp->tap_rsel.si_note, 0); > =20 > mtx_lock(&tp->tap_mtx); > - tp->tap_flags &=3D ~TAP_OPEN; > + tp->tap_flags &=3D ~(TAP_OPEN|TAP_ALLOCATED); > tp->tap_pid =3D 0; > mtx_unlock(&tp->tap_mtx); > =20 > - TAPDEBUG("%s is closed. minor =3D %#x\n",=20 > - ifp->if_xname, minor(dev)); > + TAPDEBUG("%s is closed. minor =3D %#x\n", ifp->if_xname, minor(dev)); > =20 > return (0); > } /* tapclose */ > --- if_tapvar.h.orig 2005-06-10 12:04:52.000000000 -0700 > +++ if_tapvar.h 2008-09-22 17:34:00.000000000 -0700 > @@ -54,6 +54,7 @@ > #define TAP_ASYNC (1 << 3) > #define TAP_READY (TAP_OPEN|TAP_INITED) > #define TAP_VMNET (1 << 4) > +#define TAP_ALLOCATED (1 << 5) > =20 > u_int8_t ether_addr[ETHER_ADDR_LEN]; /* ether addr of the remote side = */ > =20 --V3eawNQxI9TAjvgi Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.9 (FreeBSD) iEYEARECAAYFAkjYuc4ACgkQC3+MBN1Mb4gTGwCghsr+GIis+QqqCdFgcpwE7gwc nrkAoMMNdOjzLazZZfJTaVtwJ47qTVbr =qrMV -----END PGP SIGNATURE----- --V3eawNQxI9TAjvgi--