From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,INCLUDES_PATCH, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5C41BC43331 for ; Fri, 27 Mar 2020 17:30:30 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 22CC82072F for ; Fri, 27 Mar 2020 17:30:30 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="B1vLqAA5" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 22CC82072F Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:44852 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHsoP-0004Rp-7r for qemu-devel@archiver.kernel.org; Fri, 27 Mar 2020 13:30:29 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:58742) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHsnk-0003yQ-S1 for qemu-devel@nongnu.org; Fri, 27 Mar 2020 13:29:50 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jHsnj-0004iC-8E for qemu-devel@nongnu.org; Fri, 27 Mar 2020 13:29:48 -0400 Received: from us-smtp-delivery-74.mimecast.com ([63.128.21.74]:34190) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jHsnj-0004gk-4U for qemu-devel@nongnu.org; Fri, 27 Mar 2020 13:29:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585330186; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version:content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references; bh=cRQT7/ISMJbzRGTl6BpNPgN7scFf1EMA7FiETLedPEs=; b=B1vLqAA5I9jaUFywak1tkoeHRhfps7l10XLZS2PIiwok3FoKA9xdTljrTx/UQJIh+ed7lO cT5FXNuYP15zujsGqVANJlAVnAXQxVaRzsxYVpuBRZdqgqbm+FqGHzdXneCg2d2/PQlspX LPdVa4cvtxgv/MBPTwPoeeLAKKnxAr4= Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-56-12iKew66OmKMrGcE1yLOTA-1; Fri, 27 Mar 2020 13:29:41 -0400 X-MC-Unique: 12iKew66OmKMrGcE1yLOTA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id B989D8017CC; Fri, 27 Mar 2020 17:29:40 +0000 (UTC) Received: from [10.3.113.103] (ovpn-113-103.phx2.redhat.com [10.3.113.103]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5BC8819925; Fri, 27 Mar 2020 17:29:40 +0000 (UTC) Subject: Re: [PATCH 2/3] io: Support shutdown of TLS channel To: =?UTF-8?Q?Daniel_P=2e_Berrang=c3=a9?= References: <20200327161936.2225989-1-eblake@redhat.com> <20200327161936.2225989-3-eblake@redhat.com> <20200327164040.GQ1619@redhat.com> From: Eric Blake Organization: Red Hat, Inc. Message-ID: Date: Fri, 27 Mar 2020 12:29:39 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.6.0 MIME-Version: 1.0 In-Reply-To: <20200327164040.GQ1619@redhat.com> Content-Language: en-US X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 63.128.21.74 X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: qemu-devel@nongnu.org, qemu-block@nongnu.org Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 3/27/20 11:40 AM, Daniel P. Berrang=C3=A9 wrote: > On Fri, Mar 27, 2020 at 11:19:35AM -0500, Eric Blake wrote: >> Gnutls documents that while many apps simply yank out the underlying >> transport at the end of communication in the name of efficiency, this >> is indistinguishable from a malicious actor terminating the connection >> prematurely. Since our channel I/O code already supports the notion of >> a graceful shutdown request, it is time to plumb that through to the >> TLS layer, and wait for TLS to give the all clear before then >> terminating traffic on the underlying channel. >> >> Note that channel-tls now always advertises shutdown support, >> regardless of whether the underlying channel also has that support. >> >> Signed-off-by: Eric Blake >> --- >> io/channel-tls.c | 27 ++++++++++++++++++++++++++- >> 1 file changed, 26 insertions(+), 1 deletion(-) >> >> diff --git a/io/channel-tls.c b/io/channel-tls.c >> index 7ec8ceff2f01..f90905823e1d 100644 >> --- a/io/channel-tls.c >> +++ b/io/channel-tls.c >> @@ -360,10 +360,35 @@ static int qio_channel_tls_shutdown(QIOChannel *io= c, >> Error **errp) >> { >> QIOChannelTLS *tioc =3D QIO_CHANNEL_TLS(ioc); >> + int ret =3D 0; >> >> tioc->shutdown |=3D how; >> >> - return qio_channel_shutdown(tioc->master, how, errp); >> + do { >> + switch (how) { >> + case QIO_CHANNEL_SHUTDOWN_READ: >> + /* No TLS counterpart */ >> + break; >> + case QIO_CHANNEL_SHUTDOWN_WRITE: >> + ret =3D qcrypto_tls_session_shutdown(tioc->session, QCRYPTO= _SHUT_WR); >> + break; >> + case QIO_CHANNEL_SHUTDOWN_BOTH: >> + ret =3D qcrypto_tls_session_shutdown(tioc->session, >> + QCRYPTO_SHUT_RDWR); >> + break; >> + default: >> + abort(); >> + } >> + } while (ret =3D=3D -EAGAIN); >=20 > I don't think it is acceptable to do this loop here. The gnutls_bye() > function triggers several I/O operations which could block. Looping > like this means we busy-wait, blocking this thread for as long as I/O > is blocking on the socket. Hmm, good point. Should we give qio_channel_tls_shutdown a bool=20 parameter that says whether it should wait (good for use when we are=20 being run in a coroutine and can deal with the additional I/O) or just=20 fail with -EAGAIN (which the caller can ignore if it is not worried)? >=20 > If we must call gnutls_bye(), then it needs to be done in a way that > can integrate with the main loop so it poll()'s / unblocks the current > coroutine/thread. This makes the whole thing significantly more > complex to deal with, especially if the shutdown is being done in > cleanup paths which ordinarily are expected to execute without > blocking on I/O. This is the big reason why i never made any attempt > to use gnutls_bye(). We _are_ using gnutls_bye(GNUTLS_SHUT_RDWR) on the close() path (which=20 is indeed a cleanup path where not blocking is worthwhile) even without=20 this patch, but the question is whether using gnutls_bye(GNUTLS_SHUT_WR)=20 in the normal data path, where we are already using coroutines to manage=20 callbacks, can benefit the remote endpoint, giving them a chance to see=20 clean shutdown instead of abrupt termination. --=20 Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org