[PATCH container 2/2] fix #8093: console: bind console sessions to container lifetime via systemd scopes

[Elias Huhsovitz <e.huhsovitz@proxmox.com>]

Console processes can outlive their useful session when a container
stops or disappears while a console is attached. The previous cleanup
ran in pvestatd, which polled every 10s: forked lxc-info for every
running container, and killed orphaned processes by their PID.

Manage console lifetime in the container lifecycle instead. Add
wrap_in_console_scope() to start console commands in a systemd scope.
Bind each scope with PartOf= to the respective pve-container service.
Use the wrapper for pct console/enter/exec, and the API console
endpoints.

When the container service stops, systemd stops the related console
scopes.

Signed-off-by: Elias Huhsovitz <e.huhsovitz@proxmox.com>
---
 src/PVE/API2/LXC.pm |  6 +++---
 src/PVE/CLI/pct.pm  | 10 +++++++---
 src/PVE/LXC.pm      | 41 +++++++++++++++++++++++++++++++++++++++++
 3 files changed, 51 insertions(+), 6 deletions(-)

diff --git a/src/PVE/API2/LXC.pm b/src/PVE/API2/LXC.pm
index 5f94d5a..3fd2bf8 100644
--- a/src/PVE/API2/LXC.pm
+++ b/src/PVE/API2/LXC.pm
@@ -1015,7 +1015,7 @@ __PACKAGE__->register_method({
         my $ticket = PVE::AccessControl::assemble_vnc_ticket($authuser, $authpath, $port);
 
         my $conf = PVE::LXC::Config->load_config($vmid, $node);
-        my $concmd = PVE::LXC::get_console_command($vmid, $conf, -1);
+        my $concmd = PVE::LXC::get_console_command_scoped($vmid, $conf, -1);
 
         my $shcmd = [
             '/usr/bin/dtach',
@@ -1146,7 +1146,7 @@ __PACKAGE__->register_method({
         my $ticket = PVE::AccessControl::assemble_vnc_ticket($authuser, $authpath, $port);
 
         my $conf = PVE::LXC::Config->load_config($vmid, $node);
-        my $concmd = PVE::LXC::get_console_command($vmid, $conf, -1);
+        my $concmd = PVE::LXC::get_console_command_scoped($vmid, $conf, -1);
 
         my $shcmd = [
             '/usr/bin/dtach',
@@ -1288,7 +1288,7 @@ __PACKAGE__->register_method({
 
         die "CT $vmid not running\n" if !PVE::LXC::check_running($vmid);
 
-        my $concmd = PVE::LXC::get_console_command($vmid, $conf);
+        my $concmd = PVE::LXC::get_console_command_scoped($vmid, $conf);
 
         my $shcmd = [
             '/usr/bin/dtach',
diff --git a/src/PVE/CLI/pct.pm b/src/PVE/CLI/pct.pm
index ceb0bea..11e85bc 100755
--- a/src/PVE/CLI/pct.pm
+++ b/src/PVE/CLI/pct.pm
@@ -153,7 +153,7 @@ __PACKAGE__->register_method({
         # test if container exists on this node
         my $conf = PVE::LXC::Config->load_config($param->{vmid});
 
-        my $cmd = PVE::LXC::get_console_command($param->{vmid}, $conf, $param->{escape});
+        my $cmd = PVE::LXC::get_console_command_scoped($param->{vmid}, $conf, $param->{escape});
         exec(@$cmd);
     },
 });
@@ -207,7 +207,9 @@ __PACKAGE__->register_method({
 
         my @lxc_attach_cmd = ('lxc-attach', '-n', $vmid);
         push @lxc_attach_cmd, $keep_env ? '--keep-env' : '--clear-env';
-        exec(@lxc_attach_cmd);
+
+        my $scoped_cmd = PVE::LXC::wrap_in_console_scope($vmid, \@lxc_attach_cmd);
+        exec(@$scoped_cmd);
     },
 });
 
@@ -250,7 +252,9 @@ __PACKAGE__->register_method({
         my @lxc_attach_cmd = ('lxc-attach', '-n', $vmid);
         push @lxc_attach_cmd, $keep_env ? '--keep-env' : '--clear-env';
         push @lxc_attach_cmd, '--', @{ $param->{'extra-args'} };
-        exec(@lxc_attach_cmd);
+
+        my $scoped_cmd = PVE::LXC::wrap_in_console_scope($vmid, \@lxc_attach_cmd);
+        exec(@$scoped_cmd);
     },
 });
 
diff --git a/src/PVE/LXC.pm b/src/PVE/LXC.pm
index dee073d..14bc6e4 100644
--- a/src/PVE/LXC.pm
+++ b/src/PVE/LXC.pm
@@ -954,6 +954,39 @@ sub verify_searchdomain_list {
     return join(' ', @list);
 }
 
+=head2 wrap_in_console_scope
+
+Wraps a command array in a transient systemd scope and binds it to the
+container's main systemd service. This ensures the console process is
+automatically terminated by systemd when the container stops, preventing
+orphaned processes without requiring manual cleanup scripts.
+
+=cut
+
+sub wrap_in_console_scope {
+    my ($vmid, $cmd) = @_;
+
+    my $session_id = "$$-" . time();
+    my $unit_name = "pve-lxc-console-$vmid-$session_id";
+
+    my $service = "pve-container\@$vmid.service";
+    # service name appends "-debug" when container is started in debug mode
+    my $debug_service = "pve-container-debug\@$vmid.service";
+
+    my @scope_cmd = (
+        'systemd-run',
+        '--scope',
+        '--unit', $unit_name,
+        '--description', "PVE LXC Console for $vmid",
+        '--property', "PartOf=$service $debug_service",
+        '--quiet',
+    );
+
+    push @scope_cmd, @$cmd;
+
+    return \@scope_cmd;
+}
+
 sub get_console_command {
     my ($vmid, $conf, $escapechar) = @_;
 
@@ -978,6 +1011,14 @@ sub get_console_command {
     return $cmd;
 }
 
+sub get_console_command_scoped {
+    my ($vmid, $conf, $escapechar) = @_;
+
+    my $cmd = get_console_command($vmid, $conf, $escapechar);
+
+    return wrap_in_console_scope($vmid, $cmd)
+}
+
 sub get_primary_ips {
     my ($conf) = @_;
 
-- 
2.47.3