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 6ADFEC43331 for ; Fri, 27 Mar 2020 16:41:49 +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 35E6E20737 for ; Fri, 27 Mar 2020 16:41:49 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (1024-bit key) header.d=redhat.com header.i=@redhat.com header.b="aOPGHAvq" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 35E6E20737 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]:44330 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHs3I-0004b6-F6 for qemu-devel@archiver.kernel.org; Fri, 27 Mar 2020 12:41:48 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:46509) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jHs2M-0003x5-Ld for qemu-devel@nongnu.org; Fri, 27 Mar 2020 12:40:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1jHs2L-0004UT-2e for qemu-devel@nongnu.org; Fri, 27 Mar 2020 12:40:50 -0400 Received: from us-smtp-delivery-74.mimecast.com ([216.205.24.74]:23304) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1jHs2K-0004Td-U6 for qemu-devel@nongnu.org; Fri, 27 Mar 2020 12:40:49 -0400 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=redhat.com; s=mimecast20190719; t=1585327248; h=from:from:reply-to: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=WhCa1SDyhe82hPNjIlMd9xi1pGnnJkWeenSQ2gCKGeQ=; b=aOPGHAvqHqqQJ34iXeqpihDRxSA3Vrjrv/7qTBIhwUuARSWNssJTbr4FOsBSZKlI4rNSDW GO/vjuPBPNyA7tUktFRpjTR6p6S4pwJBbZL836ajmvOj0aEPgP5N+O9TytTyQBMRrQQYVj jTbTknkLHlTWSHIQ3Nxe2yvd8VoHObs= 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-101-rA1Lu5ElNQCzMBRgoi8LiA-1; Fri, 27 Mar 2020 12:40:46 -0400 X-MC-Unique: rA1Lu5ElNQCzMBRgoi8LiA-1 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 1A3E1800D4E; Fri, 27 Mar 2020 16:40:45 +0000 (UTC) Received: from redhat.com (unknown [10.36.110.20]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5A9FD5C1C3; Fri, 27 Mar 2020 16:40:43 +0000 (UTC) Date: Fri, 27 Mar 2020 16:40:40 +0000 From: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= To: Eric Blake Subject: Re: [PATCH 2/3] io: Support shutdown of TLS channel Message-ID: <20200327164040.GQ1619@redhat.com> References: <20200327161936.2225989-1-eblake@redhat.com> <20200327161936.2225989-3-eblake@redhat.com> MIME-Version: 1.0 In-Reply-To: <20200327161936.2225989-3-eblake@redhat.com> User-Agent: Mutt/1.13.3 (2020-01-12) X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Content-Disposition: inline X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 216.205.24.74 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: , Reply-To: Daniel =?utf-8?B?UC4gQmVycmFuZ8Op?= 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 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. >=20 > Note that channel-tls now always advertises shutdown support, > regardless of whether the underlying channel also has that support. >=20 > Signed-off-by: Eric Blake > --- > io/channel-tls.c | 27 ++++++++++++++++++++++++++- > 1 file changed, 26 insertions(+), 1 deletion(-) >=20 > 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 *ioc= , > Error **errp) > { > QIOChannelTLS *tioc =3D QIO_CHANNEL_TLS(ioc); > + int ret =3D 0; >=20 > tioc->shutdown |=3D how; >=20 > - 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); 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. 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(). Regards, Daniel --=20 |: https://berrange.com -o- https://www.flickr.com/photos/dberrange= :| |: https://libvirt.org -o- https://fstop138.berrange.com= :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange= :|