From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:52447) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eZIGt-0002Ov-QA for qemu-devel@nongnu.org; Wed, 10 Jan 2018 10:26:33 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eZIGq-00035D-Ll for qemu-devel@nongnu.org; Wed, 10 Jan 2018 10:26:31 -0500 Received: from mx1.redhat.com ([209.132.183.28]:33780) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eZIGq-00033f-Cw for qemu-devel@nongnu.org; Wed, 10 Jan 2018 10:26:28 -0500 Date: Wed, 10 Jan 2018 15:26:23 +0000 From: "Daniel P. Berrange" Message-ID: <20180110152623.GF3205@redhat.com> Reply-To: "Daniel P. Berrange" References: <20180110151322.16119-1-edgar.kaziakhmedov@virtuozzo.com> <20180110152200.GE3205@redhat.com> <81a70acc-60a2-ffee-f707-377ab01b450d@virtuozzo.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline In-Reply-To: <81a70acc-60a2-ffee-f707-377ab01b450d@virtuozzo.com> Subject: Re: [Qemu-devel] [PATCH v2 1/1] io/channel-websock: handle continuous reads without any data List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Edgar Kaziakhmedov Cc: qemu-devel@nongnu.org, den@openvz.org On Wed, Jan 10, 2018 at 06:24:25PM +0300, Edgar Kaziakhmedov wrote: > > > On 01/10/2018 06:22 PM, Daniel P. Berrange wrote: > > On Wed, Jan 10, 2018 at 06:13:22PM +0300, Edgar Kaziakhmedov wrote: > > > According to the current implementation of websocket protocol in QEMU, > > > qio_channel_websock_handshake_io tries to read handshake from the > > > channel to start communication over socket. But this approach > > > doesn't cover scenario when socket was closed while handshaking. > > > Therefore, if G_IO_IN is caught and qio_channel_read returns zero, > > > error has to be set and connection has to be done. > > > > > > Such behaviour causes 100% CPU load in main QEMU loop, because main loop > > > poll continues to receive and handle G_IO_IN events from websocket. > > > > > > Step to reproduce 100% CPU load: > > > 1) start qemu with the simplest configuration > > > $ qemu -vnc [::1]:1,websocket=7500 > > > 2) open any vnc listener (which doesn't follow websocket protocol) > > > $ vncviewer :7500 > > > 3) kill listener > > > 4) qemu main thread eats 100% CPU > > > > > > Signed-off-by: Edgar Kaziakhmedov > > > --- > > > io/channel-websock.c | 14 ++++++++++++-- > > > 1 file changed, 12 insertions(+), 2 deletions(-) > > > > > > diff --git a/io/channel-websock.c b/io/channel-websock.c > > > index 87ebdebfc0..384c34b390 100644 > > > --- a/io/channel-websock.c > > > +++ b/io/channel-websock.c > > > @@ -81,6 +81,11 @@ > > > QIO_CHANNEL_WEBSOCK_HANDSHAKE_RES_COMMON \ > > > "Connection: close\r\n" \ > > > "\r\n" > > > +#define QIO_CHANNEL_WEBSOCK_HANDSHAKE_RES_EOF \ > > > + "HTTP/1.1 403 Request Entity End Of File\r\n" \ > > > + QIO_CHANNEL_WEBSOCK_HANDSHAKE_RES_COMMON \ > > > + "Connection: close\r\n" \ > > > + "\r\n" > Well, don't you think that such http error code is not informative? The only way they could ever see that is if they called shutdown() on the socket to close the client->server data path, while leaving the server->client data path open. That's so unlikely in context of HTTP clients that I don't think its worth considering. > > > #define QIO_CHANNEL_WEBSOCK_HANDSHAKE_DELIM "\r\n" > > > #define QIO_CHANNEL_WEBSOCK_HANDSHAKE_END "\r\n\r\n" > > > #define QIO_CHANNEL_WEBSOCK_SUPPORTED_VERSION "13" > > > @@ -502,9 +507,14 @@ static int qio_channel_websock_handshake_read(QIOChannelWebsock *ioc, > > > error_setg(errp, > > > "End of headers not found in first 4096 bytes"); > > > return 1; > > > - } else { > > > - return 0; > > > + } else if (ret == 0) { > > > + qio_channel_websock_handshake_send_res_err( > > > + ioc, QIO_CHANNEL_WEBSOCK_HANDSHAKE_RES_EOF); > > > + error_setg(errp, > > > + "End of headers not found before connection closed"); > > > + return -1; > > Opps, my suggestion was slightly flawed - if we return -1, then we don't > > need to call qio_channel_websock_handshake_send_res_err(), since we'll > > just close the connection immediately. > Fixed > > > > > > Regards, > > Daniel > Regards, Daniel -- |: 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 :|