[Libguestfs] [nbdkit PATCH] nbd: Add vsock-cid= transport option
Richard W.M. Jones
rjones at redhat.com
Tue Jul 7 16:26:18 UTC 2020
On Tue, Jul 07, 2020 at 08:17:31AM -0500, Eric Blake wrote:
> 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)
I wonder if we should just call the flag "vsock=..."?
However patch looks good, ACK.
It may be possible to add a test. See this example, especially the
line requires_linux_kernel_version.
https://github.com/libguestfs/nbdkit/blob/master/tests/test-vsock.sh
Rich.
--
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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