activation: handle BUS_RESULT_LATER

This initial shot at handling a message which caused a service to be
activated and then cannot be delivered immediately because the policy
check takes time is good enough if the sender sends only one message.
It does not yet handle the situation correctly where the sender sends
multiple messages.

It is worth pointing out that the service gets auto-activated by
dbus-daemon without first checking whether the sender is allowed to
talk to the service. This is a weakness that also applies to the
traditional <allow/deny> rules.

Perhaps we should add a _can_send check before initiating the
auto-activation.

diff --git a/bus/activation.c b/bus/activation.c
index 1c7f143..9cc3336 100644 (file)
--- a/bus/activation.c
+++ b/bus/activation.c
@@ -31,6 +31,7 @@
 #include "services.h"
 #include "test.h"
 #include "utils.h"
+#include <dbus/dbus-connection-internal.h>
 #include <dbus/dbus-internals.h>
 #include <dbus/dbus-hash.h>
 #include <dbus/dbus-list.h>
@@ -1201,8 +1202,25 @@ bus_activation_send_pending_auto_activation_messages (BusActivation  *activation
               goto error;
               break;
             case BUS_RESULT_LATER:
-              /* TODO: deal with pending check while auto-activating */
-              goto error;
+              /*
+               * This must be a method call. Nothing else triggers auto-activation (?!).
+               * Therefore we can put the message back into the queue of the sender
+               * and let it go through bus_dispatch() once more without accidentally
+               * sending to other recipients twice.
+               *
+               * TODO: once we hit a BUS_RESULT_LATER, we also need to put back all
+               * further messages of the same sender. Otherwise message order
+               * is not preserved. We could track this for each sender, or we could put
+               * back *all* messages for this services. Those which could have been
+               * sent because they are from other senders then will get dispatched
+               * immediately. This is probably easier.
+               *
+               * TODO: when we put back multiple messages of the same
+               * sender, we need to preserve ordering. Probably best
+               * done in _dbus_connection_putback_message().
+               */
+              if (!_dbus_connection_putback_message (entry->connection, entry->activation_message, error))
+                goto error;
               break;
             }
         }