[PATCH pve-firewall v4 06/27] firewall: ipset: add option to handle dangling references on rename

[Arthur Bied-Charreton <a.bied-charreton@proxmox.com>]

Renaming an ipset still referenced by rules leaves dangling references.
The firewall then fails to parse those rules during compilation and
drops them. A rename can therefore effectively disable a whole set of
rules.

Add a 'dangling-references' option to the rename path offering to
'keep' the references around, 'disable' the referencing rules, 'drop'
them, or to 'rename' the references to the new name. For cluster
ipsets, this also covers references in downstream configs (host, guest
and vnet).

A rename that fails partway leaves both the old and the new ipset in
the cluster config. Retrying it chokes on the check against
overwriting an existing ipset. 'force-rename' bypasses that check, so
an interrupted rename can be finished. Avoiding the half-updated state
altogether would need either a transaction across every config in the
cluster or a rollback mechanism, neither of which is really an option
here.

Signed-off-by: Arthur Bied-Charreton <a.bied-charreton@proxmox.com>
---
 src/PVE/API2/Firewall/IPSet.pm | 83 +++++++++++++++++++++++++++++-----
 1 file changed, 71 insertions(+), 12 deletions(-)

diff --git a/src/PVE/API2/Firewall/IPSet.pm b/src/PVE/API2/Firewall/IPSet.pm
index 82b9aaf..a6a44be 100644
--- a/src/PVE/API2/Firewall/IPSet.pm
+++ b/src/PVE/API2/Firewall/IPSet.pm
@@ -534,6 +534,7 @@ package PVE::API2::Firewall::BaseIPSetList;
 
 use strict;
 use warnings;
+use PVE::Firewall::References qw(update_refs);
 use PVE::JSONSchema qw(get_standard_option);
 use PVE::Exception qw(raise_param_exc);
 use PVE::Firewall;
@@ -661,6 +662,19 @@ sub register_create {
         },
     );
 
+    $properties->{'dangling-references'} = {
+        type => 'string',
+        enum => ['keep', 'disable', 'drop', 'rename', 'force-rename'],
+        optional => 1,
+        description =>
+            "Handle references that renaming the IPSet would leave dangling. Use 'rename' to "
+            . "point them at the new name, 'disable' to disable the referencing rules, or "
+            . "'drop' to remove them entirely. 'force-rename' also renames, but skips the "
+            . "check for an existing IPSet with the target name, to finish a rename "
+            . "interrupted partway.",
+        default => 'keep',
+    };
+
     $class->register_method({
         name => 'create_ipset',
         path => '',
@@ -681,6 +695,17 @@ sub register_create {
                 sub {
                     my ($param) = @_;
 
+                    my $dangling_refs = $param->{'dangling-references'} // 'keep';
+
+                    # 'force-rename' only differs in skipping the check below, the references are
+                    # renamed either way
+                    my $ref_action;
+                    if ($dangling_refs eq 'force-rename') {
+                        $ref_action = 'rename';
+                    } elsif ($dangling_refs ne 'keep') {
+                        $ref_action = $dangling_refs;
+                    }
+
                     my ($cluster_conf, $fw_conf) = $class->load_config($param);
 
                     if ($param->{rename}) {
@@ -690,19 +715,53 @@ sub register_create {
                         raise_param_exc({ name => "IPSet '$param->{rename}' does not exist" })
                             if !$fw_conf->{ipset}->{ $param->{rename} };
 
-                        # prevent overwriting existing ipset
-                        raise_param_exc({ name => "IPSet '$param->{name}' does already exist" })
-                            if $fw_conf->{ipset}->{ $param->{name} }
-                            && $param->{name} ne $param->{rename};
-
-                        my $data = delete $fw_conf->{ipset}->{ $param->{rename} };
-                        $fw_conf->{ipset}->{ $param->{name} } = $data;
-                        if (
-                            my $comment =
-                            delete $fw_conf->{ipset_comments}->{ $param->{rename} }
-                        ) {
-                            $fw_conf->{ipset_comments}->{ $param->{name} } = $comment;
+                        if ($param->{name} ne $param->{rename}) {
+                            # prevent overwriting existing ipset
+                            raise_param_exc({
+                                name => "IPSet '$param->{name}' does already exist" })
+                                if $fw_conf->{ipset}->{ $param->{name} }
+                                && $dangling_refs ne 'force-rename';
+
+                            $fw_conf->{ipset}->{ $param->{name} } =
+                                $fw_conf->{ipset}->{ $param->{rename} };
+
+                            my $saved = 0;
+                            my $save = sub {
+                                $class->save_config($param, $fw_conf);
+                                $saved = 1;
+                            };
+
+                            eval {
+                                update_refs({
+                                    conf => $fw_conf,
+                                    kind => 'ipset',
+                                    old => $param->{rename},
+                                    new => $param->{name},
+                                    env => $class->rule_env(),
+                                    action => $ref_action,
+                                    subject =>
+                                        "ipset '$param->{rename}' renamed to '$param->{name}'",
+                                    save => $save,
+                                });
+                            };
+                            if (my $err = $@) {
+                                die "rename interrupted, the IPSet exists under both names; "
+                                    . "retry with 'force-rename' to finish: $err"
+                                    if $saved;
+                                die "could not update references to IPSet "
+                                    . "'$param->{rename}': $err";
+                            }
+
+                            delete $fw_conf->{ipset}->{ $param->{rename} };
+
+                            if (
+                                my $comment =
+                                delete $fw_conf->{ipset_comments}->{ $param->{rename} }
+                            ) {
+                                $fw_conf->{ipset_comments}->{ $param->{name} } = $comment;
+                            }
                         }
+
                         $fw_conf->{ipset_comments}->{ $param->{name} } = $param->{comment}
                             if defined($param->{comment});
                     } else {
-- 
2.47.3