From nobody Mon Feb 9 09:34:54 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1486659250430105.99165172215476; Thu, 9 Feb 2017 08:54:10 -0800 (PST) Received: from localhost ([::1]:38935 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cbryx-0000pw-PG for importer@patchew.org; Thu, 09 Feb 2017 11:54:07 -0500 Received: from eggs.gnu.org ([2001:4830:134:3::10]:48099) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cbrsg-0003jP-VP for qemu-devel@nongnu.org; Thu, 09 Feb 2017 11:47:39 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cbrsf-0003Cr-Bz for qemu-devel@nongnu.org; Thu, 09 Feb 2017 11:47:39 -0500 Received: from mx1.redhat.com ([209.132.183.28]:54320) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cbrsf-0003CT-3d; Thu, 09 Feb 2017 11:47:37 -0500 Received: from smtp.corp.redhat.com (int-mx16.intmail.prod.int.phx2.redhat.com [10.5.11.28]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 3B76D711DE; Thu, 9 Feb 2017 16:47:37 +0000 (UTC) Received: from nilsson.home.kraxel.org (ovpn-117-196.ams2.redhat.com [10.36.117.196]) by smtp.corp.redhat.com (Postfix) with ESMTP id CB16822FA03; Thu, 9 Feb 2017 16:47:34 +0000 (UTC) Received: by nilsson.home.kraxel.org (Postfix, from userid 500) id 195AB80A03; Thu, 9 Feb 2017 17:47:24 +0100 (CET) From: Gerd Hoffmann To: qemu-devel@nongnu.org Date: Thu, 9 Feb 2017 17:47:14 +0100 Message-Id: <1486658842-7143-3-git-send-email-kraxel@redhat.com> In-Reply-To: <1486658842-7143-1-git-send-email-kraxel@redhat.com> References: <1486658842-7143-1-git-send-email-kraxel@redhat.com> X-Scanned-By: MIMEDefang 2.74 on 10.5.11.28 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.38]); Thu, 09 Feb 2017 16:47:37 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PULL v2 02/10] vnc: do not disconnect on EAGAIN X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Michael Tokarev , Gerd Hoffmann , qemu-stable@nongnu.org Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" From: Michael Tokarev When qemu vnc server is trying to send large update to clients, there might be a situation when system responds with something like EAGAIN, indicating that there's no system memory to send that much data (depending on the network speed, client and server and what is happening). In this case, something like this happens on qemu side (from strace): sendmsg(16, {msg_name(0)=3DNULL, msg_iov(1)=3D[{"\244\"..., 729186}], msg_controllen=3D0, msg_flags=3D0}, 0) =3D 103950 sendmsg(16, {msg_name(0)=3DNULL, msg_iov(1)=3D[{"lz\346"..., 1559618}], msg_controllen=3D0, msg_flags=3D0}, 0) =3D -1 EAGAIN sendmsg(-1, {msg_name(0)=3DNULL, msg_iov(1)=3D[{"lz\346"..., 1559618}], msg_controllen=3D0, msg_flags=3D0}, 0) =3D -1 EBADF qemu closes the socket before the retry, and obviously it gets EBADF when trying to send to -1. This is because there WAS a special handling for EAGAIN, but now it doesn't work anymore, after commit 04d2529da27db512dcbd5e99d0e26d333f16efcc, because now in all error-like cases we initiate vnc disconnect. This change were introduced in qemu 2.6, and caused numerous grief for many people, resulting in their vnc clients reporting sporadic random disconnects from vnc server. Fix that by doing the disconnect only when necessary, i.e. omitting this very case of EAGAIN. Hopefully the existing condition (comparing with QIO_CHANNEL_ERR_BLOCK) is sufficient, as the original code (before the above commit) were checking for other errno values too. Apparently there's another (semi?)bug exist somewhere here, since the code tries to write to fd# -1, it probably should check if the connection is open before. But this isn't important. Signed-off-by: Michael Tokarev Reviewed-by: Daniel P. Berrange Message-id: 1486115549-9398-1-git-send-email-mjt@msgid.tls.msk.ru Fixes: 04d2529da27db512dcbd5e99d0e26d333f16efcc Cc: Daniel P. Berrange Cc: Gerd Hoffmann Cc: qemu-stable@nongnu.org Signed-off-by: Gerd Hoffmann --- ui/vnc.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-) diff --git a/ui/vnc.c b/ui/vnc.c index cdeb79c..f2701e5 100644 --- a/ui/vnc.c +++ b/ui/vnc.c @@ -1256,12 +1256,13 @@ ssize_t vnc_client_io_error(VncState *vs, ssize_t r= et, Error **errp) if (ret <=3D 0) { if (ret =3D=3D 0) { VNC_DEBUG("Closing down client sock: EOF\n"); + vnc_disconnect_start(vs); } else if (ret !=3D QIO_CHANNEL_ERR_BLOCK) { VNC_DEBUG("Closing down client sock: ret %zd (%s)\n", ret, errp ? error_get_pretty(*errp) : "Unknown"); + vnc_disconnect_start(vs); } =20 - vnc_disconnect_start(vs); if (errp) { error_free(*errp); *errp =3D NULL; --=20 1.8.3.1