[libnbd PATCH] RFC: api: Add nbd_supports_vsock()
by Eric Blake
Similar to nbd_supports_tls(), it is nice to know from a feature probe
whether we are likely to have VSOCK support before even trying more
expensive APIs like nbd_connect_uri("nbd+vsock://...").
---
https://bugzilla.redhat.com/show_bug.cgi?id=2069558 documents a case
where AF_VSOCK is compiled, but vsock still doesn't work because
vsock_loopback is not loaded. Should we make nbd_supports_vsock()
return true only when ALL aspects of vsock are known to be working?
---
generator/API.ml | 25 ++++++++++++++++++++++---
lib/handle.c | 17 +++++++++++++++++
2 files changed, 39 insertions(+), 3 deletions(-)
diff --git a/generator/API.ml b/generator/API.ml
index b377b9f..7ec85ca 100644
--- a/generator/API.ml
+++ b/generator/API.ml
@@ -1393,7 +1393,8 @@ "connect_uri", {
=item C<nbds+vsock:>
Connect over the C<AF_VSOCK> transport, without or with
-TLS respectively.
+TLS respectively. You can use L<nbd_supports_vsock(3)> to
+see if this build of libnbd supports C<AF_VSOCK>.
=back
@@ -1494,7 +1495,8 @@ "connect_uri", {
see_also = [URLLink "https://github.com/NetworkBlockDevice/nbd/blob/master/doc/uri.md";
Link "aio_connect_uri";
Link "set_export_name"; Link "set_tls";
- Link "set_opt_mode"; Link "get_uri"];
+ Link "set_opt_mode"; Link "get_uri";
+ Link "supports_vsock"; Link "supports_uri"];
};
"connect_unix", {
@@ -1522,8 +1524,12 @@ "connect_vsock", {
C<cid> should be C<2> (to connect to the host), and C<port> might be
C<10809> or another port number assigned to you by the host
administrator.
+
+Not all systems support C<AF_VSOCK>; to determine if libnbd was
+built on a system with vsock support, see L<nbd_supports_vsock(3)>.
" ^ blocking_connect_call_description;
- see_also = [Link "aio_connect_vsock"; Link "set_opt_mode"];
+ see_also = [Link "aio_connect_vsock"; Link "set_opt_mode";
+ Link "supports_vsock"];
};
"connect_tcp", {
@@ -3061,6 +3067,16 @@ "supports_tls", {
see_also = [Link "set_tls"];
};
+ "supports_vsock", {
+ default_call with
+ args = []; ret = RBool; is_locked = false; may_set_error = false;
+ shortdesc = "true if libnbd was compiled with support for AF_VSOCK";
+ longdesc = "\
+Returns true if libnbd was compiled with support for the AF_VSOCK family
+of sockets, or false if not.";
+ see_also = [Link "connect_vsock"; Link "connect_uri"];
+ };
+
"supports_uri", {
default_call with
args = []; ret = RBool; is_locked = false; may_set_error = false;
@@ -3233,6 +3249,9 @@ let first_version =
"set_request_block_size", (1, 12);
"get_request_block_size", (1, 12);
+ (* Added in 1.13.x development cycle, will be stable and supported in 1.14. *)
+ "supports_vsock", (1, 14);
+
(* These calls are proposed for a future version of libnbd, but
* have not been added to any released version so far.
"get_tls_certificates", (1, ??);
diff --git a/lib/handle.c b/lib/handle.c
index 8713e18..ac64fe9 100644
--- a/lib/handle.c
+++ b/lib/handle.c
@@ -28,6 +28,12 @@
#include <sys/types.h>
#include <sys/wait.h>
+#ifdef HAVE_LINUX_VM_SOCKETS_H
+#include <linux/vm_sockets.h>
+#elif HAVE_SYS_VSOCK_H
+#include <sys/vsock.h>
+#endif
+
#include "internal.h"
static void
@@ -483,6 +489,17 @@ nbd_unlocked_supports_tls (struct nbd_handle *h)
#endif
}
+/* NB: is_locked = false, may_set_error = false. */
+int
+nbd_unlocked_supports_vsock (struct nbd_handle *h)
+{
+#ifdef AF_VSOCK
+ return 1;
+#else
+ return 0;
+#endif
+}
+
/* NB: is_locked = false, may_set_error = false. */
int
nbd_unlocked_supports_uri (struct nbd_handle *h)
--
2.37.2
2 years, 3 months
