[Libguestfs] [nbdkit PATCH] nbd: Add vsock-cid= transport option
Eric Blake
eblake at redhat.com
Tue Jul 7 13:17:31 UTC 2020
With new enough libnbd, we already support vsock by virtue of uri=;
however, it's also nice to allow direct exposure of the
nbd_connect_vsock() api.
Signed-off-by: Eric Blake <eblake at redhat.com>
---
plugins/nbd/nbdkit-nbd-plugin.pod | 29 +++++++++++---
plugins/nbd/nbd.c | 63 ++++++++++++++++++++++++-------
2 files changed, 73 insertions(+), 19 deletions(-)
diff --git a/plugins/nbd/nbdkit-nbd-plugin.pod b/plugins/nbd/nbdkit-nbd-plugin.pod
index e4ac40d1..bd980209 100644
--- a/plugins/nbd/nbdkit-nbd-plugin.pod
+++ b/plugins/nbd/nbdkit-nbd-plugin.pod
@@ -6,6 +6,7 @@ nbdkit-nbd-plugin - proxy / forward to another NBD server
nbdkit nbd { command=COMMAND [arg=ARG [...]] |
hostname=HOST [port=PORT] |
+ vhost-cid=CID [port=PORT] |
socket=SOCKNAME |
socket-fd=FD |
[uri=]URI }
@@ -40,9 +41,9 @@ With L<qemu-nbd(8)>, read and write qcow2 files with nbdkit.
=head1 PARAMETERS
-One of B<socket>, B<hostname> (optionally with B<port>), B<uri>,
-B<socket-fd> or B<command> must be given to specify which NBD server
-to forward to:
+One of B<socket>, B<hostname> (optionally with B<port>), B<vsock-cid>
+(optionally with B<port>), B<uri>, B<socket-fd> or B<command> must be
+given to specify which NBD server to forward to:
=over 4
@@ -71,7 +72,22 @@ This option implies C<shared=true>.
=item B<port=>PORT
Connect to the NBD server at the remote C<HOST> using a TCP socket.
-The optional port parameter overrides the default port (10809).
+The optional port parameter overrides the default port (10809), and
+may be a 16-bit number or a non-numeric string to look up the
+well-known port for a service name.
+
+=item B<vhost-cid=>CID
+
+=item B<port=>PORT
+
+Connect to the NBD server at the given vsock C<CID> (for example, in a
+guest VM, using the cid 2 will connect to a server in the host). The
+optional port parameter overrides the default port (10809), and must
+be a 32-bit number. This only works for platforms with the
+C<AF_VSOCK> family of sockets and libnbd new enough to use it;
+C<nbdkit --dump-plugin nbd> will contain C<libnbd_vsock=1> if this is
+the case. For more details on AF_VSOCK, see
+L<nbdkit-service(1)/AF_VSOCK>.
=item B<socket=>SOCKNAME
@@ -87,8 +103,9 @@ option implies C<shared=true>.
When C<uri> is supplied, decode C<URI> to determine the address to
connect to. A URI can specify a TCP connection (such as
-C<nbd://localhost:10809/export>) or a Unix socket (such as
-C<nbd+unix:///export?socket=/path/to/sock>). Remember you may need to
+C<nbd://localhost:10809/export>), a Unix socket (such as
+C<nbd+unix:///export?socket=/path/to/sock>), or a vsock connection
+(such as C<nbd+vsock:///2:10809/export>). Remember you may need to
quote the parameter to protect it from the shell.
The C<uri> parameter is only available when the plugin was compiled
diff --git a/plugins/nbd/nbd.c b/plugins/nbd/nbd.c
index e446d52b..3f84375b 100644
--- a/plugins/nbd/nbd.c
+++ b/plugins/nbd/nbd.c
@@ -46,6 +46,7 @@
#include <semaphore.h>
#include <poll.h>
#include <fcntl.h>
+#include <sys/socket.h>
#include <libnbd.h>
@@ -61,6 +62,12 @@
DEFINE_VECTOR_TYPE(string_vector, const char *);
+#if !defined AF_VSOCK || !LIBNBD_HAVE_NBD_CONNECT_VSOCK
+#define USE_VSOCK 0
+#else
+#define USE_VSOCK 1
+#endif
+
/* The per-transaction details */
struct transaction {
int64_t cookie;
@@ -87,8 +94,15 @@ static char *sockname;
/* Connect to server via TCP socket */
static const char *hostname;
+
+/* Valid with TCP or VSOCK */
static const char *port;
+/* Connect to server via AF_VSOCK socket */
+static const char *raw_cid;
+static uint32_t cid;
+static uint32_t vport;
+
/* Connect to a command. */
static string_vector command = empty_vector;
@@ -126,11 +140,8 @@ nbdplug_unload (void)
free (command.ptr); /* the strings are statically allocated */
}
-/* Called for each key=value passed on the command line. This plugin
- * accepts socket=<sockname>, hostname=<hostname>/port=<port>, or
- * [uri=]<uri> (exactly one connection required), and optional
- * parameters export=<name>, retry=<n>, shared=<bool> and various
- * tls settings.
+/* Called for each key=value passed on the command line. See
+ * nbdplug_config_help for the various keys recognized.
*/
static int
nbdplug_config (const char *key, const char *value)
@@ -148,6 +159,10 @@ nbdplug_config (const char *key, const char *value)
hostname = value;
else if (strcmp (key, "port") == 0)
port = value;
+ else if (strcmp (key, "vsock_cid") == 0 ||
+ strcmp (key, "vsock-cid") == 0 ||
+ strcmp (key, "cid") == 0)
+ raw_cid = value;
else if (strcmp (key, "uri") == 0)
uri = value;
else if (strcmp (key, "command") == 0 || strcmp (key, "arg") == 0) {
@@ -220,23 +235,25 @@ static int
nbdplug_config_complete (void)
{
int c = !!sockname + !!hostname + !!uri +
- (command.size > 0) + (socket_fd >= 0);
+ (command.size > 0) + (socket_fd >= 0) + !!raw_cid;
/* Check the user passed exactly one connection parameter. */
if (c > 1) {
nbdkit_error ("cannot mix Unix ‘socket’, TCP ‘hostname’/‘port’, "
- "‘command’, ‘socket-fd’ and ‘uri’ parameters");
+ "‘vhost-cid’, ‘command’, ‘socket-fd’ and ‘uri’ parameters");
return -1;
}
if (c == 0) {
- nbdkit_error ("exactly one of ‘socket’, ‘hostname’, ‘command’, ‘socket-fd’ "
- "and ‘uri’ parameters must be specified");
+ nbdkit_error ("exactly one of ‘socket’, ‘hostname’, ‘vhost-cid’, "
+ "‘command’, ‘socket-fd’ and ‘uri’ parameters must be "
+ "specified");
return -1;
}
- /* Port, if present, should only be used with hostname. */
- if (port && !hostname) {
- nbdkit_error ("‘port’ parameter should only be used with ‘hostname’");
+ /* Port, if present, should only be used with hostname or vsock-cid. */
+ if (port && !(hostname || raw_cid)) {
+ nbdkit_error ("‘port’ parameter should only be used with ‘hostname’ or "
+ "‘vsock-cid’");
return -1;
}
@@ -266,6 +283,18 @@ nbdplug_config_complete (void)
if (!port)
port = "10809";
}
+ else if (raw_cid) {
+#if !USE_VSOCK
+ nbdkit_error ("libnbd was compiled without vsock support");
+ return -1;
+#else
+ if (!port)
+ port = "10809";
+ if (nbdkit_parse_uint32_t ("vsock_cid", raw_cid, &cid) == -1 ||
+ nbdkit_parse_uint32_t ("port", port, &vport) == -1)
+ return -1;
+#endif
+ }
else if (command.size > 0) {
/* Add NULL sentinel to the command. */
if (string_vector_append (&command, NULL) == -1) {
@@ -320,7 +349,8 @@ nbdplug_after_fork (void)
"[uri=]<URI> URI of an NBD socket to connect to (if supported).\n" \
"socket=<SOCKNAME> The Unix socket to connect to.\n" \
"hostname=<HOST> The hostname for the TCP socket to connect to.\n" \
- "port=<PORT> TCP port or service name to use (default 10809).\n" \
+ "port=<PORT> TCP/VHOST port or service name to use (default 10809).\n" \
+ "vhost_cid=<CID> The cid for the VSOCK socket to connect to.\n" \
"command=<COMMAND> Command to run.\n" \
"arg=<ARG> Parameters for command.\n" \
"socket-fd=<FD> Socket file descriptor to connect to.\n" \
@@ -346,6 +376,7 @@ nbdplug_dump_plugin (void)
printf ("libnbd_version=%s\n", nbd_get_version (nbd));
printf ("libnbd_tls=%d\n", nbd_supports_tls (nbd));
printf ("libnbd_uri=%d\n", nbd_supports_uri (nbd));
+ printf ("libnbd_vsock=%d\n", USE_VSOCK);
nbd_close (nbd);
}
@@ -545,6 +576,12 @@ nbdplug_open_handle (int readonly)
r = nbd_connect_unix (h->nbd, sockname);
else if (hostname)
r = nbd_connect_tcp (h->nbd, hostname, port);
+ else if (raw_cid)
+#if !USE_VSOCK
+ abort ();
+#else
+ r = nbd_connect_vsock (h->nbd, cid, vport);
+#endif
else if (command.size > 0)
r = nbd_connect_systemd_socket_activation (h->nbd, (char **) command.ptr);
else if (socket_fd >= 0)
--
2.27.0
More information about the Libguestfs
mailing list