03.10.2018 20:19, Eric Blake wrote:
Oldstyle NBD negotiation cannot perform any of the extensions that
we have recently been relying on. While you can always pass -x ""
to get newstyle negotiation, these days, it is better to just default
to newstyle (with an empty export name) and fall back to oldstyle
only on an explicit request.
For comparison:
nbdkit 1.3 switched its default to newstyle (Jan 2018):
https://github.com/libguestfs/nbdkit/commit/b2a8aecc
https://github.com/libguestfs/nbdkit/commit/8158e773
nbd 3.10 dropped oldstyle long ago (Mar 2015):
https://github.com/NetworkBlockDevice/nbd/commit/36940193
Signed-off-by: Eric Blake <ebl...@redhat.com>
---
qemu-nbd.c | 27 +++++++++++++++++++--------
1 file changed, 19 insertions(+), 8 deletions(-)
diff --git a/qemu-nbd.c b/qemu-nbd.c
index 51b9d38c727..8571a4f93d8 100644
--- a/qemu-nbd.c
+++ b/qemu-nbd.c
@@ -86,6 +86,7 @@ static void usage(const char *name)
" -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"
If we prefer this way, -x and -D descriptions should be updated a bit,
like in my patch
+" -O, --oldstyle force oldstyle negotiation\n"
"\n"
"Exposing part of the image:\n"
" -o, --offset=OFFSET offset into the image\n"
@@ -529,6 +530,7 @@ int main(int argc, char **argv)
{ "object", required_argument, NULL, QEMU_NBD_OPT_OBJECT },
{ "export-name", required_argument, NULL, 'x' },
{ "description", required_argument, NULL, 'D' },
+ { "oldstyle", no_argument, NULL, 'O' },
{ "tls-creds", required_argument, NULL, QEMU_NBD_OPT_TLSCREDS },
{ "image-opts", no_argument, NULL, QEMU_NBD_OPT_IMAGE_OPTS },
{ "trace", required_argument, NULL, 'T' },
@@ -551,6 +553,7 @@ int main(int argc, char **argv)
QDict *options = NULL;
const char *export_name = NULL;
const char *export_description = NULL;
+ bool oldstyle = false;
const char *tlscredsid = NULL;
bool imageOpts = false;
bool writethrough = true;
@@ -723,6 +726,9 @@ int main(int argc, char **argv)
case 'D':
export_description = optarg;
break;
+ case 'O':
+ oldstyle = true;
+ break;
case 'v':
verbose = 1;
break;
@@ -799,7 +805,16 @@ int main(int argc, char **argv)
}
}
+ if (!oldstyle && !export_name) {
+ /* Set the default NBD protocol export name, to favor new style. */
+ export_name = "";
+ }
+
if (tlscredsid) {
+ if (oldstyle) {
+ error_report("TLS is incompatible with oldstyle");
+ exit(EXIT_FAILURE);
+ }
if (sockpath) {
error_report("TLS is only supported with IPv4/IPv6");
exit(EXIT_FAILURE);
@@ -808,11 +823,6 @@ int main(int argc, char **argv)
error_report("TLS is not supported with a host device");
exit(EXIT_FAILURE);
}
- if (!export_name) {
- /* Set the default NBD protocol export name, since
- * we *must* use new style protocol for TLS */
- export_name = "";
- }
tlscreds = nbd_get_tls_creds(tlscredsid, &local_err);
if (local_err) {
error_report("Failed to get TLS creds %s",
@@ -1013,13 +1023,14 @@ int main(int argc, char **argv)
error_report_err(local_err);
exit(EXIT_FAILURE);
}
+ if (oldstyle && (export_name || export_description)) {
+ error_report("oldstyle negotiation cannot set export details");
+ exit(EXIT_FAILURE);
+ }
if (export_name) {
nbd_export_set_name(exp, export_name);
nbd_export_set_description(exp, export_description);
newproto = true;
a bit strange, to have both newproto and oldstyle variables which are
opposite by value.
- } else if (export_description) {
- error_report("Export description requires an export name");
- exit(EXIT_FAILURE);
}
if (device) {
--
Best regards,
Vladimir