extended monitor API by adding and removing peers

Relates to: #187

Monitor signals are only sent to the creator of the monitor. The
new Peer API enables to add and remove additional listener on the
same monitor with its subscriptions.
A user with sufficient priviledges to make methods calls to BlueChi's
API can add and remove peers. The processes for the peers can be run
by a different user with no access to BlueChi's API, but will still
be able to receive events if added by a privileged process.

Signed-off-by: Michael Engel <mengel@redhat.com>

data/org.eclipse.bluechi.Monitor.xml

@@ -58,6 +58,30 @@
       <arg name="id" type="u" direction="out" />
     </method>
 
+    <!-- 
+      AddPeer:
+      @name: The name of the peer to add as listener to all monitor events. Needs to be unique name on the bus.
+      @id: The id of the created peer
+
+      Add a new peer to the monitor. A peer will receive all events that the monitor subscribes to.
+    -->
+    <method name="AddPeer">
+      <arg name="name" type="s" direction="in" />
+      <arg name="id" type="u" direction="out" />
+    </method>
+
+    <!-- 
+      RemovePeer:
+      @id: The id of the peer to remove
+      @reason: The reason for removing the peer
+
+      Remove a previously added peer from the monitor. The reason will be part of the PeerRemoved signal, which is only sent to the respective peer.
+    -->
+    <method name="RemovePeer">
+      <arg name="id" type="u" direction="in" />
+      <arg name="reason" type="s" direction="in" />
+    </method>
+
 
     <!-- 
       UnitPropertiesChanged:
@@ -122,5 +146,15 @@
       <arg name="unit" type="s" />
       <arg name="reason" type="s" />
     </signal>
+
+    <!-- 
+      PeerRemoved:
+      @reason: The reason the peer got removed from the monitor.
+
+      Emitted when a peer is removed from the monitor, e.g. when the monitor has been closed, and only sent to the respective peer.
+    -->
+    <signal name="PeerRemoved">
+      <arg name="reason" type="s" />
+    </signal>
   </interface>
 </node>

src/bindings/python/bluechi/api.py

@@ -154,6 +154,31 @@ def subscribe_list(self, node: str, units: List[str]) -> UInt32:
             units,
         )
 
+    def add_peer(self, name: str) -> UInt32:
+        """
+          AddPeer:
+        @name: The name of the peer to add as listener to all monitor events. Needs to be unique name on the bus.
+        @id: The id of the created peer
+
+        Add a new peer to the monitor. A peer will receive all events that the monitor subscribes to.
+        """
+        return self.get_proxy().AddPeer(
+            name,
+        )
+
+    def remove_peer(self, id: UInt32, reason: str) -> None:
+        """
+          RemovePeer:
+        @id: The id of the peer to remove
+        @reason: The reason for removing the peer
+
+        Remove a previously added peer from the monitor. The reason will be part of the PeerRemoved signal, which is only sent to the respective peer.
+        """
+        self.get_proxy().RemovePeer(
+            id,
+            reason,
+        )
+
     def on_unit_properties_changed(
         self,
         callback: Callable[
@@ -246,6 +271,23 @@ def on_unit_removed(
         """
         self.get_proxy().UnitRemoved.connect(callback)
 
+    def on_peer_removed(
+        self,
+        callback: Callable[
+            [
+                str,
+            ],
+            None,
+        ],
+    ) -> None:
+        """
+          PeerRemoved:
+        @reason: The reason the peer got removed from the monitor.
+
+        Emitted when a peer is removed from the monitor, e.g. when the monitor has been closed, and only sent to the respective peer.
+        """
+        self.get_proxy().PeerRemoved.connect(callback)
+
 
 class Metrics(ApiBase):
     """

src/libbluechi/bus/utils.c

@@ -6,6 +6,8 @@
 
 #include "utils.h"
 
+#include "libbluechi/common/string-util.h"
+
 /* Number of seconds idle before sending keepalive packets */
 #define AGENT_KEEPALIVE_SOCKET_KEEPIDLE_SECS 1
 
@@ -336,3 +338,42 @@ int bus_socket_set_keepalive(sd_bus *bus) {
 
         return 0;
 }
+
+/*
+ * Copied from libsystemd/sd-bus/bus-internal.c service_name_is_valid and adjusted to
+ * exclude the well-known service names. Also does not support '_' and '-' characters.
+ */
+bool bus_id_is_valid(const char *name) {
+        if (isempty(name) || name[0] != ':') {
+                return false;
+        }
+
+        const char *i = name + 1;
+        bool dot = true;
+        bool found_dot = false;
+        for (; *i; i++) {
+                if (*i == '.') {
+                        if (dot) {
+                                return false;
+                        }
+                        found_dot = true;
+                        dot = true;
+                        continue;
+                }
+                dot = false;
+
+                if (!ascii_isalpha(*i) && !ascii_isdigit(*i)) {
+                        return false;
+                }
+        }
+
+        if (i - name > SD_BUS_MAXIMUM_NAME_LENGTH) {
+                return false;
+        }
+
+        if (dot || !found_dot) {
+                return false;
+        }
+
+        return true;
+}

src/libbluechi/bus/utils.h

@@ -43,6 +43,8 @@ int bus_parse_unit_on_node_info(sd_bus_message *message, UnitInfo *u);
 int bus_socket_set_no_delay(sd_bus *bus);
 int bus_socket_set_keepalive(sd_bus *bus);
 
+bool bus_id_is_valid(const char *name);
+
 int assemble_object_path_string(const char *prefix, const char *name, char **res);
 
 DEFINE_CLEANUP_FUNC(UnitInfo, unit_unref)

src/libbluechi/test/bus/meson.build

@@ -0,0 +1,3 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+subdir('utils')

src/libbluechi/test/bus/utils/bus_id_is_valid_test.c

@@ -0,0 +1,49 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+#include <stdbool.h>
+#include <stdio.h>
+#include <stdlib.h>
+
+#include "libbluechi/bus/utils.h"
+#include "libbluechi/common/string-util.h"
+
+bool test_bus_id_is_valid(const char *name, bool expected_is_valid) {
+        bool got_is_valid = bus_id_is_valid(name);
+        if (got_is_valid != expected_is_valid) {
+                fprintf(stderr,
+                        "FAILED: expected bus name '%s' to be %s, but got %s\n",
+                        name,
+                        bool_to_str(expected_is_valid),
+                        bool_to_str(got_is_valid));
+                return false;
+        }
+        return true;
+}
+
+int main() {
+        bool result = true;
+
+        result = result && test_bus_id_is_valid(NULL, false);
+        result = result && test_bus_id_is_valid("", false);
+        result = result && test_bus_id_is_valid(":", false);
+        result = result && test_bus_id_is_valid(":.", false);
+        result = result && test_bus_id_is_valid(":1.", false);
+        result = result && test_bus_id_is_valid(":1.3.", false);
+        result = result && test_bus_id_is_valid("1", false);
+        result = result && test_bus_id_is_valid("1.", false);
+        result = result && test_bus_id_is_valid("1.3", false);
+        result = result && test_bus_id_is_valid(":1..3", false);
+        result = result && test_bus_id_is_valid("org.eclipse.bluechi", false);
+        result = result &&
+                        test_bus_id_is_valid(
+                                        ":1.1111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111",
+                                        false);
+
+        result = result && test_bus_id_is_valid(":1.1", true);
+        result = result && test_bus_id_is_valid(":1.12345", true);
+        result = result && test_bus_id_is_valid(":1.123.45", true);
+
+        if (result) {
+                return EXIT_SUCCESS;
+        }
+        return EXIT_FAILURE;
+}

src/libbluechi/test/bus/utils/meson.build

@@ -0,0 +1,15 @@
+# SPDX-License-Identifier: LGPL-2.1-or-later
+
+bus_src = [
+  'bus_id_is_valid_test',
+]
+
+foreach src : bus_src
+  exec_test = executable(src, src + '.c',
+    link_with: [
+      bluechi_lib,
+    ],
+    include_directories: include_directories('../../../..'),
+  )
+  test(src, exec_test)
+endforeach

src/libbluechi/test/meson.build

@@ -1,4 +1,5 @@
 # SPDX-License-Identifier: LGPL-2.1-or-later
 
+subdir('bus')
 subdir('common')
 subdir('log')

src/manager/manager.c

@@ -925,7 +925,7 @@ static void manager_client_disconnected(Manager *manager, const char *client_id)
         Monitor *monitor = NULL;
         Monitor *next_monitor = NULL;
         LIST_FOREACH_SAFE(monitors, monitor, next_monitor, manager->monitors) {
-                if (streq(monitor->client, client_id)) {
+                if (streq(monitor->owner, client_id)) {
                         monitor_close(monitor);
                         manager_remove_monitor(manager, monitor);
                 }