5:29 a.m.
VDDK plugin + --run was broken because of the following sequence of
events:
(1) After .config_complete, server redirects stdin/stdout to /dev/null.
(2) Server then calls vddk_get_ready which reexecs.
(3) We restart the server from the top, but with stdin/stdout
redirected to /dev/null. So saved_stdin/saved_stdout save
/dev/null.
(4) run_command is called which "restores" /dev/null as stdin/stdout.
(5) The output of the --run option is sent to /dev/null.
In addition to fixing this problem with VDDK, it also makes general
sense not to redirect stdin/stdout before calling .get_ready since
this callback is supposed to be the last chance before the server
daemonizes, and redirecting stdin/stdout is part of daemonization.
Before this commit:
$ ./nbdkit vddk libdir=tests/.libs /dev/null --run 'qemu-img info $nbd'
[no output]
After this commit:
$ ./nbdkit vddk libdir=tests/.libs /dev/null --run 'qemu-img info $nbd'
image: nbd://localhost:10809
file format: raw
virtual size: 512 KiB (524288 bytes)
disk size: unavailable
One test (test-stdio.sh) made the assumption that stdin/stdout had
already been redirected to /dev/null in .get_ready. I adjusted this
test so it checks for redirection in .after_fork instead.
---
server/main.c | 10 +++++-----
tests/test-stdio-plugin.c | 9 +++++++++
2 files changed, 14 insertions(+), 5 deletions(-)
diff --git a/server/main.c b/server/main.c
index 2f0aaf07..11c1614b 100644
--- a/server/main.c
+++ b/server/main.c
@@ -693,6 +693,11 @@ main (int argc, char *argv[])
/* Select the correct thread model based on config. */
lock_init_thread_model ();
+ /* Tell the plugin that we are about to start serving. This must be
+ * called before we change user, fork, or open any sockets.
+ */
+ top->get_ready (top);
+
/* Sanitize stdin/stdout to /dev/null, after saving the originals
* when needed. We are still single-threaded at this point, and
* already checked that stdin/out were open, so we don't have to
@@ -726,12 +731,7 @@ main (int argc, char *argv[])
perror ("open");
exit (EXIT_FAILURE);
}
-
- /* Tell the plugin that we are about to start serving. This must be
- * called before we change user, fork, or open any sockets.
- */
configured = true;
- top->get_ready (top);
start_serving ();
diff --git a/tests/test-stdio-plugin.c b/tests/test-stdio-plugin.c
index 618eae83..86447278 100644
--- a/tests/test-stdio-plugin.c
+++ b/tests/test-stdio-plugin.c
@@ -122,6 +122,14 @@ stdio_config_complete (void)
static int
stdio_get_ready (void)
+{
+ bool check = stdio_check ();
+ assert (check == false);
+ return 0;
+}
+
+static int
+stdio_after_fork (void)
{
bool check = stdio_check ();
assert (check == true);
@@ -163,6 +171,7 @@ static struct nbdkit_plugin plugin = {
.config = stdio_config,
.config_complete = stdio_config_complete,
.get_ready = stdio_get_ready,
+ .after_fork = stdio_after_fork,
.open = stdio_open,
.get_size = stdio_get_size,
.pread = stdio_pread,
--
2.27.0
5:29 a.m.
New subject: [PATCH nbdkit 2/2] tests: Add a test of VDDK + --run.
---
tests/Makefile.am | 8 +++---
tests/test-vddk-run.sh | 56 ++++++++++++++++++++++++++++++++++++++++++
2 files changed, 61 insertions(+), 3 deletions(-)
diff --git a/tests/Makefile.am b/tests/Makefile.am
index 676e7e68..79be5639 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -913,12 +913,13 @@ if HAVE_VDDK
noinst_LTLIBRARIES += libvixDiskLib.la
LIBGUESTFS_TESTS += test-vddk
TESTS += \
- test-vddk-reexec.sh \
test-vddk-dump-plugin.sh \
test-vddk-password-fd.sh \
test-vddk-password-interactive.sh \
- test-vddk-real.sh \
test-vddk-real-dump-plugin.sh \
+ test-vddk-real.sh \
+ test-vddk-reexec.sh \
+ test-vddk-run.sh \
$(NULL)
test_vddk_SOURCES = test-vddk.c test.h
@@ -944,9 +945,10 @@ EXTRA_DIST += \
test-vddk-dump-plugin.sh \
test-vddk-password-fd.sh \
test-vddk-password-interactive.sh \
- test-vddk-real.sh \
test-vddk-real-dump-plugin.sh \
+ test-vddk-real.sh \
test-vddk-reexec.sh \
+ test-vddk-run.sh \
$(NULL)
# zero plugin test.
diff --git a/tests/test-vddk-run.sh b/tests/test-vddk-run.sh
new file mode 100755
index 00000000..19055245
--- /dev/null
+++ b/tests/test-vddk-run.sh
@@ -0,0 +1,56 @@
+#!/usr/bin/env bash
+# nbdkit
+# Copyright (C) 2018-2020 Red Hat Inc.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are
+# met:
+#
+# * Redistributions of source code must retain the above copyright
+# notice, this list of conditions and the following disclaimer.
+#
+# * Redistributions in binary form must reproduce the above copyright
+# notice, this list of conditions and the following disclaimer in the
+# documentation and/or other materials provided with the distribution.
+#
+# * Neither the name of Red Hat nor the names of its contributors may be
+# used to endorse or promote products derived from this software without
+# specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY RED HAT AND CONTRIBUTORS ''AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
+# THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
+# PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL RED HAT OR
+# CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
+# SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
+# LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
+# USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
+# ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+# OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+# OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+
+# Test VDDK + --run parameter.
+
+source ./functions.sh
+set -e
+set -x
+
+# Testing $LD_LIBRARY_PATH stuff breaks valgrind, so skip the rest of
+# this test if valgrinding.
+if [ "x$NBDKIT_VALGRIND" = "x1" ]; then
+ echo "$0: skipped LD_LIBRARY_PATH test when doing valgrind"
+ exit 77
+fi
+
+requires qemu-img --version
+
+out=test-vddk-run.out
+rm -f $out
+cleanup_fn rm -f $out
+
+nbdkit -U - vddk libdir=.libs /dev/null --run 'qemu-img info $nbd' > $out
+cat $out
+
+grep 'file format: raw' $out
+grep 'virtual size:.*524288 bytes' $out
--
2.27.0
8:08 a.m.
On 8/5/20 5:29 AM, Richard W.M. Jones wrote:
VDDK plugin + --run was broken because of the following sequence of
events:
(1) After .config_complete, server redirects stdin/stdout to /dev/null.
(2) Server then calls vddk_get_ready which reexecs.
(3) We restart the server from the top, but with stdin/stdout
redirected to /dev/null. So saved_stdin/saved_stdout save
/dev/null.
(4) run_command is called which "restores" /dev/null as stdin/stdout.
(5) The output of the --run option is sent to /dev/null.
In addition to fixing this problem with VDDK, it also makes general
sense not to redirect stdin/stdout before calling .get_ready since
this callback is supposed to be the last chance before the server
daemonizes, and redirecting stdin/stdout is part of daemonization.
It's been an interesting game of sequencing, but as we add more tests,
we're certainly going to be more robust against future breakage ;)
Series looks good.
--
Eric Blake, Principal Software Engineer
Red Hat, Inc. +1-919-301-3226
Virtualization: qemu.org | libvirt.org
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Richard W.M. Jones