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 <[email protected]>
> ---
> 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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