nbd: Add qemu-nbd -D for human-readable description
The NBD protocol allows servers to advertise a human-readable
description alongside an export name during NBD_OPT_LIST. Add
an option to pass through the user's string to the NBD client.
Doing this also makes it easier to test commit 200650d4, which
is the client counterpart of receiving the description.
Signed-off-by: Eric Blake <eblake@redhat.com>
Message-Id: <1476469998-28592-2-git-send-email-eblake@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
diff --git a/include/block/nbd.h b/include/block/nbd.h
index 80610ff..fd58390 100644
--- a/include/block/nbd.h
+++ b/include/block/nbd.h
@@ -115,6 +115,7 @@
NBDExport *nbd_export_find(const char *name);
void nbd_export_set_name(NBDExport *exp, const char *name);
+void nbd_export_set_description(NBDExport *exp, const char *description);
void nbd_export_close_all(void);
void nbd_client_new(NBDExport *exp,
diff --git a/nbd/nbd-internal.h b/nbd/nbd-internal.h
index 93a6ca8..7e78064 100644
--- a/nbd/nbd-internal.h
+++ b/nbd/nbd-internal.h
@@ -104,9 +104,10 @@
return nbd_wr_syncv(ioc, &iov, 1, size, true);
}
-static inline ssize_t write_sync(QIOChannel *ioc, void *buffer, size_t size)
+static inline ssize_t write_sync(QIOChannel *ioc, const void *buffer,
+ size_t size)
{
- struct iovec iov = { .iov_base = buffer, .iov_len = size };
+ struct iovec iov = { .iov_base = (void *) buffer, .iov_len = size };
return nbd_wr_syncv(ioc, &iov, 1, size, false);
}
diff --git a/nbd/server.c b/nbd/server.c
index 36bcafc..ac42391 100644
--- a/nbd/server.c
+++ b/nbd/server.c
@@ -61,6 +61,7 @@
BlockBackend *blk;
char *name;
+ char *description;
off_t dev_offset;
off_t size;
uint16_t nbdflags;
@@ -129,7 +130,8 @@
}
-static ssize_t nbd_negotiate_write(QIOChannel *ioc, void *buffer, size_t size)
+static ssize_t nbd_negotiate_write(QIOChannel *ioc, const void *buffer,
+ size_t size)
{
ssize_t ret;
guint watch;
@@ -225,11 +227,15 @@
static int nbd_negotiate_send_rep_list(QIOChannel *ioc, NBDExport *exp)
{
- uint64_t magic, name_len;
+ uint64_t magic;
+ size_t name_len, desc_len;
uint32_t opt, type, len;
+ const char *name = exp->name ? exp->name : "";
+ const char *desc = exp->description ? exp->description : "";
- TRACE("Advertising export name '%s'", exp->name ? exp->name : "");
- name_len = strlen(exp->name);
+ TRACE("Advertising export name '%s' description '%s'", name, desc);
+ name_len = strlen(name);
+ desc_len = strlen(desc);
magic = cpu_to_be64(NBD_REP_MAGIC);
if (nbd_negotiate_write(ioc, &magic, sizeof(magic)) != sizeof(magic)) {
LOG("write failed (magic)");
@@ -245,18 +251,22 @@
LOG("write failed (reply type)");
return -EINVAL;
}
- len = cpu_to_be32(name_len + sizeof(len));
+ len = cpu_to_be32(name_len + desc_len + sizeof(len));
if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
LOG("write failed (length)");
return -EINVAL;
}
len = cpu_to_be32(name_len);
if (nbd_negotiate_write(ioc, &len, sizeof(len)) != sizeof(len)) {
- LOG("write failed (length)");
+ LOG("write failed (name length)");
return -EINVAL;
}
- if (nbd_negotiate_write(ioc, exp->name, name_len) != name_len) {
- LOG("write failed (buffer)");
+ if (nbd_negotiate_write(ioc, name, name_len) != name_len) {
+ LOG("write failed (name buffer)");
+ return -EINVAL;
+ }
+ if (nbd_negotiate_write(ioc, desc, desc_len) != desc_len) {
+ LOG("write failed (description buffer)");
return -EINVAL;
}
return 0;
@@ -894,6 +904,12 @@
nbd_export_put(exp);
}
+void nbd_export_set_description(NBDExport *exp, const char *description)
+{
+ g_free(exp->description);
+ exp->description = g_strdup(description);
+}
+
void nbd_export_close(NBDExport *exp)
{
NBDClient *client, *next;
@@ -903,6 +919,7 @@
client_close(client);
}
nbd_export_set_name(exp, NULL);
+ nbd_export_set_description(exp, NULL);
nbd_export_put(exp);
}
@@ -921,6 +938,7 @@
if (--exp->refcount == 0) {
assert(exp->name == NULL);
+ assert(exp->description == NULL);
if (exp->close) {
exp->close(exp);
diff --git a/qemu-nbd.c b/qemu-nbd.c
index b757dc7..c734f62 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -83,6 +83,7 @@
" -t, --persistent don't exit on the last connection\n"
" -v, --verbose display extra debugging information\n"
" -x, --export-name=NAME expose export by name\n"
+" -D, --description=TEXT with -x, also export a human-readable description\n"
"\n"
"Exposing part of the image:\n"
" -o, --offset=OFFSET offset into the image\n"
@@ -477,7 +478,7 @@
off_t fd_size;
QemuOpts *sn_opts = NULL;
const char *sn_id_or_name = NULL;
- const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:";
+ const char *sopt = "hVb:o:p:rsnP:c:dvk:e:f:tl:x:T:D:";
struct option lopt[] = {
{ "help", no_argument, NULL, 'h' },
{ "version", no_argument, NULL, 'V' },
@@ -503,6 +504,7 @@
{ "verbose", no_argument, NULL, 'v' },
{ "object", required_argument, NULL, QEMU_NBD_OPT_OBJECT },
{ "export-name", required_argument, NULL, 'x' },
+ { "description", required_argument, NULL, 'D' },
{ "tls-creds", required_argument, NULL, QEMU_NBD_OPT_TLSCREDS },
{ "image-opts", no_argument, NULL, QEMU_NBD_OPT_IMAGE_OPTS },
{ "trace", required_argument, NULL, 'T' },
@@ -524,6 +526,7 @@
BlockdevDetectZeroesOptions detect_zeroes = BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF;
QDict *options = NULL;
const char *export_name = NULL;
+ const char *export_description = NULL;
const char *tlscredsid = NULL;
bool imageOpts = false;
bool writethrough = true;
@@ -689,6 +692,9 @@
case 'x':
export_name = optarg;
break;
+ case 'D':
+ export_description = optarg;
+ break;
case 'v':
verbose = 1;
break;
@@ -937,7 +943,11 @@
}
if (export_name) {
nbd_export_set_name(exp, export_name);
+ nbd_export_set_description(exp, export_description);
newproto = true;
+ } else if (export_description) {
+ error_report("Export description requires an export name");
+ exit(EXIT_FAILURE);
}
server_ioc = qio_channel_socket_new();
diff --git a/qemu-nbd.texi b/qemu-nbd.texi
index b7a9c6d..9a84e81 100644
--- a/qemu-nbd.texi
+++ b/qemu-nbd.texi
@@ -79,9 +79,12 @@
Allow up to @var{num} clients to share the device (default @samp{1})
@item -t, --persistent
Don't exit on the last connection
-@item -x NAME, --export-name=NAME
+@item -x, --export-name=@var{name}
Set the NBD volume export name. This switches the server to use
the new style NBD protocol negotiation
+@item -D, --description=@var{description}
+Set the NBD volume export description, as a human-readable
+string. Requires the use of @option{-x}
@item --tls-creds=ID
Enable mandatory TLS encryption for the server by setting the ID
of the TLS credentials object previously created with the --object
