Re: [libvirt] [PATCH 1/2] esx: Add libcurl based stream driver

This allows to implement libvirt functions that use streams, such as virDoaminScreenshot, without the need to store the downloaded data in a temporary file first. The stream driver directly interacts with libcurl to send and receive data. The driver uses the libcurl multi interface that allows to do a transfer in multiple curl_multi_perform() calls. The easy interface would do the whole transfer in a single curl_easy_perform() call. This doesn't work with the libvirt stream API that is driven by multiple calls to the virStreamSend() and virStreamRecv() functions. The curl_multi_wait() function is used to do blocking operations. But it was added in libcurl 7.28.0. For older versions it is emulated using the socket callback of the multi interface. The current driver only supports blocking operations. There is already some code in place for non-blocking mode but it's incomplete. As you can tell from the copyright date I implemeted this in 2012, but never came around to publish it then. I did some work in 2013 and now it's 2014 and I don't want to hold it back any longer. --- po/POTFILES.in | 1 + src/Makefile.am | 1 + src/esx/esx_stream.c | 478 +++++++++++++++++++++++++++++++++++++++++++++++++++ src/esx/esx_stream.h | 32 ++++ src/esx/esx_vi.c | 222 +++++++++++++++++++++++- src/esx/esx_vi.h | 19 +- 6 files changed, 749 insertions(+), 4 deletions(-) create mode 100644 src/esx/esx_stream.c create mode 100644 src/esx/esx_stream.h

diff --git a/src/esx/esx_stream.c b/src/esx/esx_stream.c new file mode 100644 index 0000000..fb9abbc --- /dev/null +++ b/src/esx/esx_stream.c @@ -0,0 +1,478 @@ +/* + * esx_stream.c: libcurl based stream driver + * + * Copyright (C) 2012-2014 Matthias Bolte <matthias.bolte(a)googlemail.com&gt; + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library. If not, see + * <http://www.gnu.org/licenses/>;. + * + */ + +#include <config.h> + +#include "internal.h" +#include "datatypes.h" +#include "viralloc.h" +#include "virstring.h" +#include "esx_stream.h" + +#define VIR_FROM_THIS VIR_FROM_ESX

+ +/* + * This libcurl based stream driver cannot use a libcurl easy handle alone + * because curl_easy_perform would do the whole transfer before it returns. + * But there is no place in the stream handling concept that would allow for + * such a call to be made. The stream is driven by esxStream(Send|Recv) which + * is probably called multiple times to send/receive the stream in chunks. + * Therefore, a libcurl multi handle is used that allows to perform the data + * transfer in chunks and also allows to support non-blocking operations. + * + * In the upload direction esxStreamSend is called to push data into the + * stream and libcurl will call esxVI_CURL_ReadStream to pull data out of + * the stream to upload it via HTTP(S). To realize this esxStreamSend calls + * esxStreamTransfer that uses esxVI_MultiCURL_(Wait|Perform) to drive the + * transfer and makes libcurl read up the data passed to esxStreamSend. + * + * In the download direction esxStreamRecv is called to pull data out of the + * stream and libcurl will call esxVI_CURL_WriteStream to push data into the + * stream that it has downloaded via HTTP(S). To realize this esxStreamRecv + * calls esxStreamTransfer that uses esxVI_MultiCURL_(Wait|Perform) to drive + * the transfer and makes libcurl write to the buffer passed to esxStreamRecv. + * + * The download direction requires some extra logic because libcurl might + * call esxVI_CURL_WriteStream with more data than there is space left in the + * buffer passed to esxStreamRecv. But esxVI_CURL_WriteStream is not allowed + * to handle only a part of the incoming data, it needs to handle it all at + * once. Therefore the stream driver manages a backlog buffer that holds the + * extra data that didn't fit into the esxStreamRecv buffer anymore. The next + * time esxStreamRecv is called it'll read the data from the backlog buffer + * first before asking libcurl for more data. + * + * Typically libcurl will call esxVI_CURL_WriteStream with up to 16kb data + * this means that the typically maximum backlog size should be 16kb as well. + */

+static int +esxStreamClose(virStreamPtr stream, bool finish) +{ + int result = 0; + esxStreamPrivate *priv = stream->privateData; + + if (!priv) + return 0; + + virMutexLock(&priv->curl->lock); + + if (finish && priv->backlog_used > 0) {

+ virReportError(VIR_ERR_INTERNAL_ERROR, "%s", + _("Stream has untransferred data left")); + result = -1; + } + + stream->privateData = NULL; + + virMutexUnlock(&priv->curl->lock); + + esxFreeStreamPrivate(&priv); + + return result; +} +

diff --git a/src/esx/esx_vi.c b/src/esx/esx_vi.c index 6188139..ba34bfd 100644 --- a/src/esx/esx_vi.c +++ b/src/esx/esx_vi.c @@ -2,7 +2,7 @@ * esx_vi.c: client for the VMware VI API 2.5 to manage ESX hosts * * Copyright (C) 2010-2012 Red Hat, Inc. - * Copyright (C) 2009-2012 Matthias Bolte <matthias.bolte(a)googlemail.com&gt; + * Copyright (C) 2009-2012, 2014 Matthias Bolte <matthias.bolte(a)googlemail.com&gt; * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Lesser General Public @@ -22,6 +22,7 @@ #include <config.h> +#include <poll.h> #include <libxml/parser.h> #include <libxml/xpathInternals.h> @@ -662,6 +663,68 @@ esxVI_SharedCURL_Remove(esxVI_SharedCURL *shared, esxVI_CURL *curl) * MultiCURL */ +#if ESX_EMULATE_CURL_MULTI_WAIT + +static int +esxVI_MultiCURL_SocketCallback(CURL *handle ATTRIBUTE_UNUSED, + curl_socket_t fd, int action, + void *callback_opaque, + void *socket_opaque ATTRIBUTE_UNUSED) +{ + esxVI_MultiCURL *multi = callback_opaque; + size_t i; + struct pollfd *pollfd = NULL; + struct pollfd dummy; + + if (action & CURL_POLL_REMOVE) { + for (i = 0; i < multi->npollfds; ++i) { + if (multi->pollfds[i].fd == fd) { + VIR_DELETE_ELEMENT(multi->pollfds, i, multi->npollfds); + break; + } + } + } else { + for (i = 0; i < multi->npollfds; ++i) { + if (multi->pollfds[i].fd == fd) { + pollfd = &multi->pollfds[i]; + break; + } + } + + if (pollfd == NULL) { + if (VIR_APPEND_ELEMENT(multi->pollfds, multi->npollfds, dummy) < 0) { + return 0;

+ } + + pollfd = &multi->pollfds[multi->npollfds - 1]; + } + + pollfd->fd = fd; + pollfd->events = 0; + + if (action & CURL_POLL_IN) + pollfd->events |= POLLIN; + + if (action & CURL_POLL_OUT) + pollfd->events |= POLLOUT; + } + + return 0; +} +