[PATCH storage 7/7] iscsi: add periodic-discovery flag to skip re-discovery on login

[Dietmar Maurer <dietmar@proxmox.com>]

Every login first re-runs sendtargets discovery, which auto-persists
node records and resets their node.* settings to defaults. This
clobbers tuned records (timeouts, iface binding) and re-imposes the
portal's full advertised set, fighting intentional per-node record
divergence.

With periodic-discovery=0, discovery only runs when the node db has
no record for the target, seeding it once; later logins use the
existing records as-is. Login stays poll-driven either way, so
dropped sessions are still re-established on the next poll. The
default (1) keeps the current re-discover-on-login behavior. Static
iscsi-node-map configurations already bypass discovery, so the flag
has no effect there.

Signed-off-by: Dietmar Maurer <dietmar@proxmox.com>
---
 src/PVE/Storage/ISCSIPlugin.pm | 26 +++++++++++++++++++++-----
 1 file changed, 21 insertions(+), 5 deletions(-)

diff --git a/src/PVE/Storage/ISCSIPlugin.pm b/src/PVE/Storage/ISCSIPlugin.pm
index 85f33aa..33197b9 100644
--- a/src/PVE/Storage/ISCSIPlugin.pm
+++ b/src/PVE/Storage/ISCSIPlugin.pm
@@ -276,12 +276,12 @@ sub iscsi_discovery {
 }
 
 sub iscsi_login {
-    my ($target, $portals, $cache, $static) = @_;
+    my ($target, $portals, $cache, $skip_discovery) = @_;
 
     assert_iscsi_support();
 
-    # static configurations have their node db records synced already
-    if (!$static) {
+    # skipped when the node db records for the target already exist
+    if (!$skip_discovery) {
         eval { iscsi_discovery($target, $portals, $cache); };
         warn $@ if $@;
     }
@@ -573,6 +573,15 @@ sub properties {
                 format => $iscsi_node_map_fmt,
             },
         },
+        'periodic-discovery' => {
+            description => "Re-run sendtargets discovery before every login (default)."
+                . " When disabled, discovery only runs when the node database has no"
+                . " record for the target, and logins use the existing records as-is."
+                . " Has no effect when a static iscsi-node-map configuration applies.",
+            type => 'boolean',
+            default => 1,
+            optional => 1,
+        },
     };
 }
 
@@ -581,6 +590,7 @@ sub options {
         portal => { fixed => 1 },
         target => { fixed => 1 },
         'iscsi-node-map' => { optional => 1 },
+        'periodic-discovery' => { optional => 1 },
         nodes => { optional => 1 },
         disable => { optional => 1 },
         content => { optional => 1 },
@@ -716,16 +726,22 @@ sub activate_storage {
 
     my $node_targets = get_node_targets($scfg);
     my $static = $node_targets->{static};
+    my $periodic_discovery = $scfg->{'periodic-discovery'} // 1;
 
     for my $node_target (@{ $node_targets->{targets} }) {
         my ($target, $portals) = ($node_target->{target}, $node_target->{portals});
+        my $skip_discovery = $static;
 
         if ($static) {
             iscsi_sync_node_records($target, $portals, $cache);
         } else {
             # fall back to the configured discovery address on an empty node db
             my $recorded = iscsi_portals($target);
-            $portals = $recorded if scalar(@$recorded);
+            if (scalar(@$recorded)) {
+                $portals = $recorded;
+                # seed-once mode: the node db already holds records for this target
+                $skip_discovery = 1 if !$periodic_discovery;
+            }
         }
 
         my $sessions = iscsi_session($cache, $target);
@@ -745,7 +761,7 @@ sub activate_storage {
         }
 
         if ($do_login) {
-            eval { iscsi_login($target, $portals, $cache, $static); };
+            eval { iscsi_login($target, $portals, $cache, $skip_discovery); };
             warn $@ if $@;
         } else {
             # make sure we get all devices
-- 
2.47.3