Commit 796a060b authored Jul 08, 2015 by Richard W.M. Jones Committed by Jeff Cody Jul 14, 2015

block/curl: Don't lose original error when a connection fails.

Currently if qemu is connected to a curl source (eg. web server), and
the web server fails / times out / dies, you always see a bogus EIO
"Input/output error".

For example, choose a large file located on any local webserver which
you control:

  $ qemu-img convert -p http://example.com/large.iso /tmp/test

Once it starts copying the file, stop the webserver and you will see
qemu-img fail with:

  qemu-img: error while reading sector 61440: Input/output error

This patch does two things: Firstly print the actual error from curl
so it doesn't get lost.  Secondly, change EIO to EPROTO.  EPROTO is a
POSIX.1 compatible errno which more accurately reflects that there was
a protocol error, rather than some kind of hardware failure.

After this patch is applied, the error changes to:

  $ qemu-img convert -p http://example.com/large.iso

 /tmp/test
  qemu-img: curl: transfer closed with 469989 bytes remaining to read
  qemu-img: error while reading sector 16384: Protocol error

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Signed-off-by: Jeff Cody <jcody@redhat.com>

parent 48ac0a4d

block/curl.c

+14 −1

Original line number	Diff line number	Diff line
		@@ -22,6 +22,7 @@
		* THE SOFTWARE.
		*/
		#include "qemu-common.h"
		#include "qemu/error-report.h"
		#include "block/block_int.h"
		#include "qapi/qmp/qbool.h"
		#include "qapi/qmp/qstring.h"
		@@ -298,6 +299,18 @@ static void curl_multi_check_completion(BDRVCURLState *s)
		/* ACBs for successful messages get completed in curl_read_cb */
		if (msg->data.result != CURLE_OK) {
		int i;
		static int errcount = 100;

		/* Don't lose the original error message from curl, since
		* it contains extra data.
		*/
		if (errcount > 0) {
		error_report("curl: %s", state->errmsg);
		if (--errcount == 0) {
		error_report("curl: further errors suppressed");
		}
		}

		for (i = 0; i < CURL_NUM_ACB; i++) {
		CURLAIOCB *acb = state->acb[i];

		@@ -305,7 +318,7 @@ static void curl_multi_check_completion(BDRVCURLState *s)
		continue;
		}

		acb->common.cb(acb->common.opaque, -EIO);
		acb->common.cb(acb->common.opaque, -EPROTO);
		qemu_aio_unref(acb);
		state->acb[i] = NULL;
		}