Libguestfs - Nov 2021 - [PATCH libnbd 1/2] tests: Test nbd_connect_systemd_socket_activation

Test connecting using systemd socket activation, and using the handle
URI to connect additional handles.

The tests reveals a deadlock when closing the first handle owning the
nbdkit server. Closing the first handle last avoids this issue.

Signed-off-by: Nir Soffer <nsoffer at redhat.com>
---
 tests/Makefile.am                         |  5 ++
 tests/connect-systemd-socket-activation.c | 83 +++++++++++++++++++++++
 2 files changed, 88 insertions(+)
 create mode 100644 tests/connect-systemd-socket-activation.c

diff --git a/tests/Makefile.am b/tests/Makefile.am
index 7f00f6f..1451fb8 100644
--- a/tests/Makefile.am
+++ b/tests/Makefile.am
@@ -192,6 +192,7 @@ check_PROGRAMS += \
 	opt-list \
 	opt-info \
 	opt-list-meta \
+	connect-systemd-socket-activation \
 	connect-unix \
 	connect-tcp \
 	connect-tcp6 \
@@ -235,6 +236,7 @@ TESTS += \
 	opt-list \
 	opt-info \
 	opt-list-meta \
+	connect-systemd-socket-activation \
 	connect-unix \
 	connect-tcp \
 	connect-tcp6 \
@@ -424,6 +426,9 @@ opt_info_LDADD = $(top_builddir)/lib/libnbd.la
 opt_list_meta_SOURCES = opt-list-meta.c
 opt_list_meta_LDADD = $(top_builddir)/lib/libnbd.la
 
+connect_systemd_socket_activation_SOURCES = connect-systemd-socket-activation.c
+connect_systemd_socket_activation_LDADD = $(top_builddir)/lib/libnbd.la
+
 connect_unix_SOURCES = connect-unix.c
 connect_unix_LDADD = $(top_builddir)/lib/libnbd.la
 
diff --git a/tests/connect-systemd-socket-activation.c
b/tests/connect-systemd-socket-activation.c
new file mode 100644
index 0000000..d64319a
--- /dev/null
+++ b/tests/connect-systemd-socket-activation.c
@@ -0,0 +1,83 @@
+/* NBD client library in userspace
+ * Copyright (C) 2021 Red Hat Inc.
+ *
+ * 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 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/* Test connecting using systemd socket activation. */
+
+#include <config.h>
+
+#include <stdio.h>
+#include <stdlib.h>
+
+#include <libnbd.h>
+
+#define CONNECTIONS 4
+
+int
+main (int argc, char *argv[])
+{
+  char *args[] = {"nbdkit", "-f", "memory",
"size=1m", NULL};
+  struct nbd_handle *nbd[CONNECTIONS] = {0};
+  char *uri = NULL;
+  int result = EXIT_FAILURE;
+
+  printf("Connecting handle 0 with systemd socket actication\n");
+
+  nbd[0] = nbd_create ();
+  if (nbd[0] == NULL)
+    goto out;
+
+  if (nbd_connect_systemd_socket_activation (nbd[0], args) == -1)
+    goto out;
+
+  uri = nbd_get_uri (nbd[0]);
+  if (uri == NULL)
+    goto out;
+
+  printf("Using URI: %s\n", uri);
+
+  for (int i = 1; i < CONNECTIONS; i++) {
+    printf ("Connecting handle %d to URI\n", i);
+
+    nbd[i] = nbd_create ();
+    if (nbd[i] == NULL)
+      goto out;
+
+    if (nbd_connect_uri (nbd[i], uri) == -1)
+      goto out;
+  }
+
+  printf ("All handles connected\n");
+  result = EXIT_SUCCESS;
+
+out:
+  if (result == EXIT_FAILURE)
+    fprintf (stderr, "%s\n", nbd_get_error ());
+
+  free (uri);
+
+  /* Closing the first connection deadlocks, so we close the additional
+   * connections first. */
+  for (int i = CONNECTIONS - 1; i >= 0; i--) {
+    if (nbd[i]) {
+      printf ("Closing handle %d\n", i);
+      nbd_close (nbd[i]);
+    }
+  }
+
+  exit (result);
+}
-- 
2.31.1

On Sun, Nov 07, 2021 at 03:27:46PM +0200, Nir Soffer
wrote:
> Test connecting using systemd socket activation, and using the handle
> URI to connect additional handles.
> 
> The tests reveals a deadlock when closing the first handle owning the
> nbdkit server. Closing the first handle last avoids this issue.
> 
> Signed-off-by: Nir Soffer <nsoffer at redhat.com>
> ---
>  tests/Makefile.am                         |  5 ++
>  tests/connect-systemd-socket-activation.c | 83 +++++++++++++++++++++++
>  2 files changed, 88 insertions(+)
>  create mode 100644 tests/connect-systemd-socket-activation.c
> 
> diff --git a/tests/Makefile.am b/tests/Makefile.am
> index 7f00f6f..1451fb8 100644
> --- a/tests/Makefile.am
> +++ b/tests/Makefile.am
> @@ -192,6 +192,7 @@ check_PROGRAMS += \
>  	opt-list \
>  	opt-info \
>  	opt-list-meta \
> +	connect-systemd-socket-activation \
>  	connect-unix \
>  	connect-tcp \
>  	connect-tcp6 \
> @@ -235,6 +236,7 @@ TESTS += \
>  	opt-list \
>  	opt-info \
>  	opt-list-meta \
> +	connect-systemd-socket-activation \
>  	connect-unix \
>  	connect-tcp \
>  	connect-tcp6 \
> @@ -424,6 +426,9 @@ opt_info_LDADD = $(top_builddir)/lib/libnbd.la
>  opt_list_meta_SOURCES = opt-list-meta.c
>  opt_list_meta_LDADD = $(top_builddir)/lib/libnbd.la
>  
> +connect_systemd_socket_activation_SOURCES =
connect-systemd-socket-activation.c
> +connect_systemd_socket_activation_LDADD = $(top_builddir)/lib/libnbd.la
> +
>  connect_unix_SOURCES = connect-unix.c
>  connect_unix_LDADD = $(top_builddir)/lib/libnbd.la
>  
> diff --git a/tests/connect-systemd-socket-activation.c
b/tests/connect-systemd-socket-activation.c
> new file mode 100644
> index 0000000..d64319a
> --- /dev/null
> +++ b/tests/connect-systemd-socket-activation.c
> @@ -0,0 +1,83 @@
> +/* NBD client library in userspace
> + * Copyright (C) 2021 Red Hat Inc.
> + *
> + * 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 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, write to the Free Software
> + * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
02110-1301 USA
> + */
> +
> +/* Test connecting using systemd socket activation. */
> +
> +#include <config.h>
> +
> +#include <stdio.h>
> +#include <stdlib.h>
> +
> +#include <libnbd.h>
> +
> +#define CONNECTIONS 4
> +
> +int
> +main (int argc, char *argv[])
> +{
> +  char *args[] = {"nbdkit", "-f", "memory",
"size=1m", NULL};
> +  struct nbd_handle *nbd[CONNECTIONS] = {0};
> +  char *uri = NULL;
> +  int result = EXIT_FAILURE;
The test needs to skip if nbdkit and/or the memory plugin is not
available.  This can be done using:

#include "requires.h"
...
requires ("nbdkit --version");
requires ("nbdkit memory --version");
> +  printf("Connecting handle 0 with systemd socket
actication\n");
> +
> +  nbd[0] = nbd_create ();
> +  if (nbd[0] == NULL)
> +    goto out;
> +
> +  if (nbd_connect_systemd_socket_activation (nbd[0], args) == -1)
> +    goto out;
> +
> +  uri = nbd_get_uri (nbd[0]);
> +  if (uri == NULL)
> +    goto out;
> +
> +  printf("Using URI: %s\n", uri);
I'm not sure what nbd_get_uri should show here - possibly it *ought*
to return NULL (since there's no URI that should connect back to a
server launched with systemd-socket-activation).  But later ...
> +  for (int i = 1; i < CONNECTIONS; i++) {
> +    printf ("Connecting handle %d to URI\n", i);
> +
> +    nbd[i] = nbd_create ();
> +    if (nbd[i] == NULL)
> +      goto out;
> +
> +    if (nbd_connect_uri (nbd[i], uri) == -1)
> +      goto out;
> +  }
Now I'm intrigued.  I'm guessing the URI exposes the internal socket
we create (/tmp/libnbdXXXXXX/sock) for SSA.  Which sounds like an
"interesting" corner of the API.  It also prevents us from changing
this in future -- eg. to use socketpair or a socket in the anonymous
space.

Also this test needs to check for nbd_can_multi_conn >= 1 before
actually doing this (although nbdkit will always return it).
> +  printf ("All handles connected\n");
> +  result = EXIT_SUCCESS;
> +
> +out:
> +  if (result == EXIT_FAILURE)
> +    fprintf (stderr, "%s\n", nbd_get_error ());
> +
> +  free (uri);
> +
> +  /* Closing the first connection deadlocks, so we close the additional
> +   * connections first. */
And this seems like a bear-trap.

I support the idea of making this work, but I'm not sure that doing it
this way is a good API.

Rich.
> +  for (int i = CONNECTIONS - 1; i >= 0; i--) {
> +    if (nbd[i]) {
> +      printf ("Closing handle %d\n", i);
> +      nbd_close (nbd[i]);
> +    }
> +  }
> +
> +  exit (result);
> +}
> -- 
> 2.31.1
-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
Read my programming and virtualization blog: http://rwmj.wordpress.com
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