[PATCH pve-manager v5 6/7] close #4369: api: optionally only suggest unique IDs

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

At the moment, the `/cluster/nextid` API endpoint will return the lowest
available VM/CT ID, which means that it will suggest re-using VM IDs.
This can be undesirable, so add an optional check to ensure that it
chooses an ID which is not and has never been in use.

This optional behaviour is enabled when `unique-next-id: 1` in
the datacenter config, and the previously used IDs are tracked as a
list in the file `/etc/pve/used-guest-ids`.

Originally-by: Daniel Krambrock <krambrock@hrz.uni-marburg.de>
Originally-by: Severen Redwood <severen.redwood@sitehost.co.nz>
Signed-off-by: Michael Köppl <m.koeppl@proxmox.com>
---
 PVE/API2/Cluster.pm | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/PVE/API2/Cluster.pm b/PVE/API2/Cluster.pm
index 4e5efbfd9..8178562a5 100644
--- a/PVE/API2/Cluster.pm
+++ b/PVE/API2/Cluster.pm
@@ -20,6 +20,7 @@ use PVE::RPCEnvironment;
 use PVE::SafeSyslog;
 use PVE::Storage;
 use PVE::Tools qw(extract_param);
+use PVE::UsedGuestIDs;
 
 use PVE::API2::ACMEAccount;
 use PVE::API2::ACMEPlugin;
@@ -1041,12 +1042,18 @@ __PACKAGE__->register_method({
 
         my $dc_conf = PVE::Cluster::cfs_read_file('datacenter.cfg');
         my $next_id = $dc_conf->{'next-id'} // {};
+        my $used_ids;
+        if ($dc_conf->{'unique-next-id'}) {
+            $used_ids = PVE::UsedGuestIDs::read_list();
+        } else {
+            $used_ids = {};
+        }
 
         my $lower = $next_id->{lower} // 100;
         my $upper = $next_id->{upper} // (1000 * 1000); # note, lower than the schema-maximum
 
         for (my $i = $lower; $i < $upper; $i++) {
-            return $i if !defined($idlist->{$i});
+            return $i if !defined($idlist->{$i}) and !defined($used_ids->{$i});
         }
 
         die "unable to get any free VMID in range [$lower, $upper]\n";
-- 
2.47.3