[PATCH guest-common v8 11/22] guest id: add helper to check guest IDs against next-id enforcement

["Michael Köppl" <m.koeppl@proxmox.com>]

With 'enforce' set in the next-id datacenter option, creating a guest
with an ID outside the configured range or, with 'unique', an ID that
was used before fails when the ID is registered. That only happens once
the creation task is already running.

Add a helper that runs the same checks without recording the ID, so that
callers can reject such IDs early. The helper reads the list of used
IDs without taking the lock, so another node may record the ID in
between. register_used_id() still checks it under the lock and remains
the authoritative check.

Signed-off-by: Michael Köppl <m.koeppl@proxmox.com>
Reviewed-by: Fiona Ebner <f.ebner@proxmox.com>
Tested-by: Fiona Ebner <f.ebner@proxmox.com>
---
 src/PVE/GuestID.pm | 13 +++++++++++++
 1 file changed, 13 insertions(+)

diff --git a/src/PVE/GuestID.pm b/src/PVE/GuestID.pm
index 83876db..a7e93a5 100644
--- a/src/PVE/GuestID.pm
+++ b/src/PVE/GuestID.pm
@@ -202,6 +202,19 @@ my sub assert_id_in_next_id_range($next_id_opts, $id) {
         if defined($upper) && $id >= $upper;
 }
 
+# Dies if the next-id datacenter option enforces its range or uniqueness
+# and a new guest must not use $id.
+sub assert_id_satisfies_next_id_settings($id) {
+    my $next_id_opts = cfs_read_file('datacenter.cfg')->{'next-id'} // {};
+    return if !$next_id_opts->{enforce};
+
+    assert_id_in_next_id_range($next_id_opts, $id);
+
+    if ($next_id_opts->{unique}) {
+        die "guest ID $id was used before\n" if get_next_unused_id($id) != $id;
+    }
+}
+
 # Records $id as used. If the next-id datacenter option enforces its
 # range or uniqueness, IDs a new guest must not use are rejected.
 # IDs of currently existing guests are never rejected.
-- 
2.47.3