Commit 55b09667 in v1.15.3 made it possible for nbd_can_meta_context() to return an error if it is called too early during handshaking, which is useful when doing manual control via nbd_set_opt_mode for integration testing. But it had the unfortunate side effect of treating ALL server errors as unknown state for meta contexts. This didn't matter for clients that never attempt meta context negotiation, or for servers that don't support structured replies (nbd-server 3.24); but for servers with structured replies but not meta contexts (nbd-server 3.25), it means we are now reporting an error about failure to negotiate rather than silently treating the query as false. And with this patch in place, the one-off hack to nbdkit mentioned in that commit (when a server fails after partial success, rather than immediately) still has the desired effect of an error in nbd_can_meta_context. The test for this fix is in a separate commit, to make it easier to rearrange the patch series to demonstrate that the issue at hand can also be worked around in client code. Fiexs: 55b09667 ("api: Fix nbd_can_meta_context if NBD_OPT_SET_META_CONTEXT fails", v1.15.3) Signed-off-by: Eric Blake <eblake(a)redhat.com&gt; --- generator/states-newstyle-opt-meta-context.c | 2 ++ 1 file changed, 2 insertions(+) diff --git a/generator/states-newstyle-opt-meta-context.c b/generator/states-newstyle-opt-meta-context.c index 47e0fcd5..b62a7df0 100644 --- a/generator/states-newstyle-opt-meta-context.c +++ b/generator/states-newstyle-opt-meta-context.c @@ -281,6 +281,8 @@ NEWSTYLE.OPT_META_CONTEXT.CHECK_REPLY: SET_NEXT_STATE (%.NEGOTIATING); } else { + if (opt == NBD_OPT_SET_META_CONTEXT && h->meta_contexts.len == 0) + h->meta_valid = true; debug (h, "handshake: ignoring unexpected error from " "NBD_OPT_SET_META_CONTEXT (%" PRIu32 ")", reply); SET_NEXT_STATE (%^OPT_GO.START); -- 2.43.2