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sd-bus: make introspection data non-recursive

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Currently, our introspection data looks like this:

        <node>
         <interface name="org.freedesktop.DBus.Peer">
           ...
         </interface>
         <interface name="org.freedesktop.DBus.Introspectable">
           ...
         </interface>
         <interface name="org.freedesktop.DBus.Properties">
           ...
         </interface>
         <node name="org"/>
         <node name="org/freedesktop"/>
         <node name="org/freedesktop/login1"/>
         <node name="org/freedesktop/login1/user"/>
         <node name="org/freedesktop/login1/user/self"/>
         <node name="org/freedesktop/login1/user/_1000"/>
         <node name="org/freedesktop/login1/seat"/>
         <node name="org/freedesktop/login1/seat/self"/>
         <node name="org/freedesktop/login1/seat/seat0"/>
         <node name="org/freedesktop/login1/session"/>
         <node name="org/freedesktop/login1/session/self"/>
         <node name="org/freedesktop/login1/session/c1"/>
        </node>

(ordered alphabetically for better visibility)

This is grossly incorrect. The spec says that we're allowed to return
non-directed children, however, it does not allow us to return data
recursively in multiple parents. If we return "org", then we must not
return anything else that starts with "org/".

It is unclear, whether we can include child-nodes as a tree. Moreover, it
is usually not what the caller wants. Hence, this patch changes sd-bus to
never return introspection data recursively. Instead, only a single
child-layer is returned.

This patch relies on enumerators to never return hierarchies. If someone
registers an enumerator via sd_bus_add_enumerator, they better register
sub-enumerators if they support *TRUE* hierarchies. Each enumerator is
treated as a single layer and not filtered.
Enumerators are still allowed to return nested data. However, that data
is still required to be a single hierarchy. For instance, returning
"/org/foo" and "/com/bar" is fine, but including "/com" or "/org" in that
dataset is not.
This should be the default for enumerators and I see no reason to filter
in sd-bus. Moreover, filtering that data-set would require to sort the
strv by path and then do prefix-filtering. This is O(n log n), which
would be fine, but still better to avoid.

Fixes #664.
This commit is contained in:
David Herrmann 2015-09-05 19:43:29 +02:00
parent b47c788854
commit 44eb1adda9
1 changed files with 15 additions and 7 deletions
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22
src/libsystemd/sd-bus/bus-objects.c
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@ -169,11 +169,18 @@ static int add_enumerated_to_set(
return 0;
}
enum {
/* if set, add_subtree() works recursively */
CHILDREN_RECURSIVE = (1U << 1),
/* if set, add_subtree() scans object-manager hierarchies recursively */
CHILDREN_SUBHIERARCHIES = (1U << 0),
};
static int add_subtree_to_set(
sd_bus *bus,
const char *prefix,
struct node *n,
bool skip_subhierarchies,
unsigned int flags,
Set *s,
sd_bus_error *error) {
@ -205,8 +212,9 @@ static int add_subtree_to_set(
if (r < 0 && r != -EEXIST)
return r;
if (!skip_subhierarchies || !i->object_managers) {
r = add_subtree_to_set(bus, prefix, i, skip_subhierarchies, s, error);
if ((flags & CHILDREN_RECURSIVE) &&
((flags & CHILDREN_SUBHIERARCHIES) || !i->object_managers)) {
r = add_subtree_to_set(bus, prefix, i, flags, s, error);
if (r < 0)
return r;
if (bus->nodes_modified)
@ -221,7 +229,7 @@ static int get_child_nodes(
sd_bus *bus,
const char *prefix,
struct node *n,
bool skip_subhierarchies,
unsigned int flags,
Set **_s,
sd_bus_error *error) {
@ -237,7 +245,7 @@ static int get_child_nodes(
if (!s)
return -ENOMEM;
r = add_subtree_to_set(bus, prefix, n, skip_subhierarchies, s, error);
r = add_subtree_to_set(bus, prefix, n, flags, s, error);
if (r < 0) {
set_free_free(s);
return r;
@ -907,7 +915,7 @@ static int process_introspect(
assert(n);
assert(found_object);
r = get_child_nodes(bus, m->path, n, false, &s, &error);
r = get_child_nodes(bus, m->path, n, 0, &s, &error);
if (r < 0)
return bus_maybe_reply_error(m, r, &error);
if (bus->nodes_modified)
@ -1173,7 +1181,7 @@ static int process_get_managed_objects(
if (require_fallback || !n->object_managers)
return 0;
r = get_child_nodes(bus, m->path, n, true, &s, &error);
r = get_child_nodes(bus, m->path, n, CHILDREN_RECURSIVE, &s, &error);
if (r < 0)
return r;
if (bus->nodes_modified)