From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:34378) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fagLQ-0007mA-Dd for qemu-devel@nongnu.org; Wed, 04 Jul 2018 07:53:13 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fagLM-0005QD-E9 for qemu-devel@nongnu.org; Wed, 04 Jul 2018 07:53:12 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:39058 helo=mx1.redhat.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1fagLM-0005PW-89 for qemu-devel@nongnu.org; Wed, 04 Jul 2018 07:53:08 -0400 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.rdu2.redhat.com [10.11.54.4]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id ADA3D407574B for ; Wed, 4 Jul 2018 11:53:07 +0000 (UTC) References: <20180704111118.7241-1-berrange@redhat.com> From: Paolo Bonzini Message-ID: Date: Wed, 4 Jul 2018 13:53:03 +0200 MIME-Version: 1.0 In-Reply-To: <20180704111118.7241-1-berrange@redhat.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Subject: Re: [Qemu-devel] [PATCH] chardev: unconditionally set FD_PASS feature for socket type=fd List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "=?UTF-8?Q?Daniel_P._Berrang=c3=a9?=" , qemu-devel@nongnu.org Cc: =?UTF-8?Q?Marc-Andr=c3=a9_Lureau?= On 04/07/2018 13:11, Daniel P. Berrang=C3=A9 wrote: > The vhostuser network backend requires the chardev it is using to have > the FD passing feature. It checks this upfront when initializing the > network backend and reports an error if not set. >=20 > The socket chardev has to set the FD_PASS feature during early > initialization to satisfy the vhostuser backend, and at this point > the socket has not been initialized. It is thus unable to do a live > check on the socket to see if it supports FD passing (aka is a UNIX > socket). As a result it has to blindly set FD_PASS feature based > solely on info in the SocketAddress struct, such as address type. >=20 > Unfortunately libvirt wishes to use FD passing to provide the UNIX > domain socket listener, and as a result the FD_PASS feature is no > longer set, which breaks vhostuser's checks, despite the fact that > FD passing will in fact work later. >=20 > This unconditionally sets FD_PASS feature for any socket address > which has type=3D=3Dfd. Thus will be wrong if the passed in FD was not > a UNIX socket, but if an attempt is later made to use FD passing > we'll still get an error reported by the QIOChannelSocket class. > So the effective of setting the chardev FD_PASS feature early > is merely to delay error reporting. Could you query with getsockopt or getsockname in tcp_chr_connect? Paolo > Signed-off-by: Daniel P. Berrang=C3=A9 > --- > chardev/char-socket.c | 14 ++++++++++++-- > 1 file changed, 12 insertions(+), 2 deletions(-) >=20 > diff --git a/chardev/char-socket.c b/chardev/char-socket.c > index 17519ec589..b495d6a851 100644 > --- a/chardev/char-socket.c > +++ b/chardev/char-socket.c > @@ -990,8 +990,18 @@ static void qmp_chardev_open_socket(Chardev *chr, > s->addr =3D addr =3D socket_address_flatten(sock->addr); > =20 > qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_RECONNECTABLE); > - /* TODO SOCKET_ADDRESS_FD where fd has AF_UNIX */ > - if (addr->type =3D=3D SOCKET_ADDRESS_TYPE_UNIX) { > + /* > + * We can't tell at this point if the "fd" we're passed is > + * a UNIX socket or not, so can't reliably set the > + * FD_PASS feature. vhost-user, however, checks for this > + * feature early before we've even created the I/O channel, > + * so we can't wait until later to set the feature. Thus > + * we optimistically set the FD_PASS feature. If the passed > + * in "fd" is not a UNIX socket, there will be an error > + * reported later anyway. > + */ > + if (addr->type =3D=3D SOCKET_ADDRESS_TYPE_UNIX || > + addr->type =3D=3D SOCKET_ADDRESS_TYPE_FD) { > qemu_chr_set_feature(chr, QEMU_CHAR_FEATURE_FD_PASS); > } > =20 >=20