19 files changed, 569 insertions, 423 deletions

diff --git a/Makefile.am b/Makefile.am
index 15500adaae..38445fb33c 100644
--- a/Makefile.am
+++ b/Makefile.am
@@ -975,8 +975,6 @@ libsystemd_core_la_SOURCES = \
 	src/core/dbus-kill.h \
 	src/core/dbus-cgroup.c \
 	src/core/dbus-cgroup.h \
-	src/core/dbus-client-track.c \
-	src/core/dbus-client-track.h \
 	src/core/cgroup.c \
 	src/core/cgroup.h \
 	src/core/selinux-access.c \
@@ -2056,6 +2054,8 @@ libsystemd_internal_la_SOURCES = \
 	src/libsystemd/sd-bus/bus-gvariant.c \
 	src/libsystemd/sd-bus/bus-gvariant.h \
 	src/libsystemd/sd-bus/bus-convenience.c \
+	src/libsystemd/sd-bus/bus-track.c \
+	src/libsystemd/sd-bus/bus-track.h \
 	src/libsystemd/sd-bus/bus-util.c \
 	src/libsystemd/sd-bus/bus-util.h \
 	src/libsystemd/sd-bus/bus-protocol.h \
diff --git a/src/core/dbus-client-track.c b/src/core/dbus-client-track.c
deleted file mode 100644
index 07dfea49e6..0000000000
--- a/src/core/dbus-client-track.c
+++ /dev/null
@@ -1,251 +0,0 @@
-/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
-
-/***
-  This file is part of systemd.
-
-  Copyright 2013 Lennart Poettering
-
-  systemd is free software; you can redistribute it and/or modify it
-  under the terms of the GNU Lesser General Public License as published by
-  the Free Software Foundation; either version 2.1 of the License, or
-  (at your option) any later version.
-
-  systemd is distributed in the hope that it will be useful, but
-  WITHOUT ANY WARRANTY; without even the implied warranty of
-  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
-  Lesser General Public License for more details.
-
-  You should have received a copy of the GNU Lesser General Public License
-  along with systemd; If not, see <http://www.gnu.org/licenses/>.
-***/
-
-#include "bus-util.h"
-#include "dbus-client-track.h"
-
-static unsigned long tracked_client_hash(const void *a, const uint8_t hash_key[HASH_KEY_SIZE]) {
-        const BusTrackedClient *x = a;
-
-        return string_hash_func(x->name, hash_key) ^ trivial_hash_func(x->bus, hash_key);
-}
-
-static int tracked_client_compare(const void *a, const void *b) {
-        const BusTrackedClient *x = a, *y = b;
-        int r;
-
-        r = strcmp(x->name, y->name);
-        if (r != 0)
-                return r;
-
-        if (x->bus < y->bus)
-                return -1;
-        if (x->bus > y->bus)
-                return 1;
-
-        return 0;
-}
-
-static int on_name_owner_changed(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
-        BusTrackedClient *c = userdata;
-        const char *name, *old, *new;
-        int r;
-
-        assert(bus);
-        assert(message);
-
-        r = sd_bus_message_read(message, "sss", &name, &old, &new);
-        if (r < 0) {
-                bus_log_parse_error(r);
-                return r;
-        }
-
-        bus_client_untrack(c->set, bus, name);
-        return 0;
-}
-
-static char *build_match(const char *name) {
-
-        return strjoin("type='signal',"
-                       "sender='org.freedesktop.DBus',"
-                       "path='/org/freedesktop/DBus',"
-                       "interface='org.freedesktop.DBus',"
-                       "member='NameOwnerChanged',"
-                       "arg0='", name, "'", NULL);
-}
-
-int bus_client_track(Set **s, sd_bus *bus, const char *name) {
-        BusTrackedClient *c, *found;
-        size_t l;
-        int r;
-
-        assert(s);
-        assert(bus);
-
-        r = set_ensure_allocated(s, tracked_client_hash, tracked_client_compare);
-        if (r < 0)
-                return r;
-
-        name = strempty(name);
-
-        l = strlen(name);
-
-        c = alloca(offsetof(BusTrackedClient, name) + l + 1);
-        c->set = *s;
-        c->bus = bus;
-        strcpy(c->name, name);
-
-        found = set_get(*s, c);
-        if (found)
-                return 0;
-
-        c = memdup(c, offsetof(BusTrackedClient, name) + l + 1);
-        if (!c)
-                return -ENOMEM;
-
-        r = set_put(*s, c);
-        if (r < 0) {
-                free(c);
-                return r;
-        }
-
-        if (!isempty(name)) {
-                _cleanup_free_ char *match = NULL;
-
-                match = build_match(name);
-                if (!match) {
-                        set_remove(*s, c);
-                        free(c);
-                        return -ENOMEM;
-                }
-
-                r = sd_bus_add_match(bus, match, on_name_owner_changed, c);
-                if (r < 0) {
-                        set_remove(*s, c);
-                        free(c);
-                        return r;
-                }
-        }
-
-        sd_bus_ref(c->bus);
-        return 1;
-}
-
-static void bus_client_free_one(Set *s, BusTrackedClient *c) {
-        assert(s);
-        assert(c);
-
-        if (!isempty(c->name)) {
-                _cleanup_free_ char *match = NULL;
-
-                match = build_match(c->name);
-                if (match)
-                        sd_bus_remove_match(c->bus, match, on_name_owner_changed, c);
-        }
-
-        sd_bus_unref(c->bus);
-        set_remove(s, c);
-        free(c);
-}
-
-int bus_client_untrack(Set *s, sd_bus *bus, const char *name) {
-        BusTrackedClient *c, *found;
-        size_t l;
-
-        assert(bus);
-        assert(s);
-        assert(name);
-
-        name = strempty(name);
-
-        l = strlen(name);
-
-        c = alloca(offsetof(BusTrackedClient, name) + l + 1);
-        c->bus = bus;
-        strcpy(c->name, name);
-
-        found = set_get(s, c);
-        if (!found)
-                return 0;
-
-        bus_client_free_one(s, found);
-        return 1;
-}
-
-void bus_client_track_free(Set *s) {
-        BusTrackedClient *c;
-
-        while ((c = set_first(s)))
-                bus_client_free_one(s, c);
-
-        set_free(s);
-}
-
-int bus_client_untrack_bus(Set *s, sd_bus *bus) {
-        BusTrackedClient *c;
-        Iterator i;
-        int r = 0;
-
-        SET_FOREACH(c, s, i)
-                if (c->bus == bus) {
-                        bus_client_free_one(s, c);
-                        r++;
-                }
-
-        return r;
-}
-
-void bus_client_track_serialize(Manager *m, FILE *f, Set *s) {
-        BusTrackedClient *c;
-        Iterator i;
-
-        assert(m);
-        assert(f);
-
-        SET_FOREACH(c, s, i) {
-                if (c->bus == m->api_bus)
-                        fprintf(f, "subscribed=%s\n", isempty(c->name) ? "*" : c->name);
-                else
-                        fprintf(f, "subscribed=%p %s\n", c->bus, isempty(c->name) ? "*" : c->name);
-        }
-}
-
-int bus_client_track_deserialize_item(Manager *m, Set **s, const char *line) {
-        const char *e, *q, *name;
-        sd_bus *bus;
-        void *p;
-        int r;
-
-        e = startswith(line, "subscribed=");
-        if (!e)
-                return 0;
-
-        q = strpbrk(e, WHITESPACE);
-        if (!q) {
-                if (m->api_bus) {
-                        bus = m->api_bus;
-                        name = e;
-                        goto finish;
-                }
-
-                return 1;
-        }
-
-        if (sscanf(e, "%p", &p) != 1) {
-                log_debug("Failed to parse subscription pointer.");
-                return -EINVAL;
-        }
-
-        bus = set_get(m->private_buses, p);
-        if (!bus)
-                return 1;
-
-        name = q + strspn(q, WHITESPACE);
-
-finish:
-        r = bus_client_track(s, bus, streq(name, "*") ? NULL : name);
-        if (r < 0) {
-                log_debug("Failed to deserialize client subscription: %s", strerror(-r));
-                return r;
-        }
-
-        return 1;
-}
diff --git a/src/core/dbus-job.c b/src/core/dbus-job.c
index a8eae4734e..5c364a4264 100644
--- a/src/core/dbus-job.c
+++ b/src/core/dbus-job.c
@@ -24,7 +24,7 @@
 #include "selinux-access.h"
 #include "job.h"
 #include "dbus-job.h"
-#include "dbus-client-track.h"
+#include "dbus.h"
 
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_type, job_type, JobType);
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_state, job_state, JobState);
@@ -79,53 +79,10 @@ const sd_bus_vtable bus_job_vtable[] = {
         SD_BUS_VTABLE_END
 };
 
-static int foreach_client(Job *j, int (*send_message)(sd_bus *bus, const char *name, Job *j)) {
-        BusTrackedClient *one_destination = NULL;
-        Iterator i;
-        sd_bus *b;
-        unsigned n, m;
-        int r, ret;
-
-        assert(j);
-        assert(send_message);
-
-        n = set_size(j->manager->subscribed);
-        m = set_size(j->subscribed);
-
-        if (n <= 0 && m <= 0)
-                return 0;
-
-        if (n == 1 && m == 0)
-                one_destination = set_first(j->manager->subscribed);
-        else if (n == 0 && m == 1)
-                one_destination = set_first(j->subscribed);
-        else
-                one_destination = NULL;
-
-        if (one_destination)
-                return send_message(one_destination->bus, isempty(one_destination->name) ? NULL : one_destination->name, j);
-
-        ret = 0;
-
-        /* Send to everybody */
-        SET_FOREACH(b, j->manager->private_buses, i) {
-                r = send_message(b, NULL, j);
-                if (r < 0)
-                        ret = r;
-        }
-
-        if (j->manager->api_bus) {
-                r = send_message(j->manager->api_bus, NULL, j);
-                if (r < 0)
-                        ret = r;
-        }
-
-        return ret;
-}
-
-static int send_new_signal(sd_bus *bus, const char *destination, Job *j) {
+static int send_new_signal(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         _cleanup_free_ char *p = NULL;
+        Job *j = userdata;
         int r;
 
         assert(bus);
@@ -148,11 +105,12 @@ static int send_new_signal(sd_bus *bus, const char *destination, Job *j) {
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, m, destination, NULL);
+        return sd_bus_send(bus, m, NULL);
 }
 
-static int send_changed_signal(sd_bus *bus, const char *destination, Job *j) {
+static int send_changed_signal(sd_bus *bus, void *userdata) {
         _cleanup_free_ char *p = NULL;
+        Job *j = userdata;
 
         assert(bus);
         assert(j);
@@ -174,16 +132,17 @@ void bus_job_send_change_signal(Job *j) {
                 j->in_dbus_queue = false;
         }
 
-        r = foreach_client(j, j->sent_dbus_new_signal ? send_changed_signal : send_new_signal);
+        r = bus_foreach_bus(j->manager, j->subscribed, j->sent_dbus_new_signal ? send_changed_signal : send_new_signal, j);
         if (r < 0)
                 log_debug("Failed to send job change signal for %u: %s", j->id, strerror(-r));
 
         j->sent_dbus_new_signal = true;
 }
 
-static int send_removed_signal(sd_bus *bus, const char *destination, Job *j) {
+static int send_removed_signal(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         _cleanup_free_ char *p = NULL;
+        Job *j = userdata;
         int r;
 
         assert(bus);
@@ -193,7 +152,6 @@ static int send_removed_signal(sd_bus *bus, const char *destination, Job *j) {
         if (!p)
                 return -ENOMEM;
 
-
         r = sd_bus_message_new_signal(
                         bus,
                         &m,
@@ -207,7 +165,7 @@ static int send_removed_signal(sd_bus *bus, const char *destination, Job *j) {
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, m, destination, NULL);
+        return sd_bus_send(bus, m, NULL);
 }
 
 void bus_job_send_removed_signal(Job *j) {
@@ -218,7 +176,7 @@ void bus_job_send_removed_signal(Job *j) {
         if (!j->sent_dbus_new_signal)
                 bus_job_send_change_signal(j);
 
-        r = foreach_client(j, send_removed_signal);
+        r = bus_foreach_bus(j->manager, j->subscribed, send_removed_signal, j);
         if (r < 0)
                 log_debug("Failed to send job remove signal for %u: %s", j->id, strerror(-r));
 }
diff --git a/src/core/dbus-manager.c b/src/core/dbus-manager.c
index f1e344c180..34ef1f5d29 100644
--- a/src/core/dbus-manager.c
+++ b/src/core/dbus-manager.c
@@ -37,7 +37,6 @@
 #include "dbus-manager.h"
 #include "dbus-unit.h"
 #include "dbus-snapshot.h"
-#include "dbus-client-track.h"
 #include "dbus-execute.h"
 #include "bus-errors.h"
 
@@ -824,11 +823,23 @@ static int method_subscribe(sd_bus *bus, sd_bus_message *message, void *userdata
         if (r < 0)
                 return r;
 
-        r = bus_client_track(&m->subscribed, bus, sd_bus_message_get_sender(message));
-        if (r < 0)
-                return r;
-        if (r == 0)
-                return sd_bus_error_setf(error, BUS_ERROR_ALREADY_SUBSCRIBED, "Client is already subscribed.");
+        if (bus == m->api_bus) {
+
+                /* Note that direct bus connection subscribe by
+                 * default, we only track peers on the API bus here */
+
+                if (!m->subscribed) {
+                        r = sd_bus_track_new(bus, &m->subscribed, NULL, NULL);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = sd_bus_track_add_sender(m->subscribed, message);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return sd_bus_error_setf(error, BUS_ERROR_ALREADY_SUBSCRIBED, "Client is already subscribed.");
+        }
 
         return sd_bus_reply_method_return(message, NULL);
 }
@@ -845,11 +856,13 @@ static int method_unsubscribe(sd_bus *bus, sd_bus_message *message, void *userda
         if (r < 0)
                 return r;
 
-        r = bus_client_untrack(m->subscribed, bus, sd_bus_message_get_sender(message));
-        if (r < 0)
-                return r;
-        if (r == 0)
-                return sd_bus_error_setf(error, BUS_ERROR_NOT_SUBSCRIBED, "Client is not subscribed.");
+        if (bus == m->api_bus) {
+                r = sd_bus_track_remove_sender(m->subscribed, message);
+                if (r < 0)
+                        return r;
+                if (r == 0)
+                        return sd_bus_error_setf(error, BUS_ERROR_NOT_SUBSCRIBED, "Client is not subscribed.");
+        }
 
         return sd_bus_reply_method_return(message, NULL);
 }
@@ -1348,7 +1361,7 @@ static int method_get_default_target(sd_bus *bus, sd_bus_message *message, void
         return sd_bus_reply_method_return(message, "s", default_target);
 }
 
-static int send_unit_files_changed(sd_bus *bus, const char *destination, void *userdata) {
+static int send_unit_files_changed(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *message = NULL;
         int r;
 
@@ -1358,7 +1371,7 @@ static int send_unit_files_changed(sd_bus *bus, const char *destination, void *u
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, message, destination, NULL);
+        return sd_bus_send(bus, message, NULL);
 }
 
 static int reply_unit_file_changes_and_free(
@@ -1374,7 +1387,7 @@ static int reply_unit_file_changes_and_free(
         int r;
 
         if (n_changes > 0)
-                bus_manager_foreach_client(m, send_unit_files_changed, NULL);
+                bus_foreach_bus(m, NULL, send_unit_files_changed, NULL);
 
         r = sd_bus_message_new_method_return(message, &reply);
         if (r < 0)
@@ -1656,41 +1669,7 @@ const sd_bus_vtable bus_manager_vtable[] = {
         SD_BUS_VTABLE_END
 };
 
-int bus_manager_foreach_client(Manager *m, int (*send_message)(sd_bus *bus, const char *destination, void *userdata), void *userdata) {
-        Iterator i;
-        sd_bus *b;
-        unsigned n;
-        int r, ret;
-
-        n = set_size(m->subscribed);
-        if (n <= 0)
-                return 0;
-        if (n == 1) {
-                BusTrackedClient *d;
-
-                assert_se(d = set_first(m->subscribed));
-                return send_message(d->bus, isempty(d->name) ? NULL : d->name, userdata);
-        }
-
-        ret = 0;
-
-        /* Send to everybody */
-        SET_FOREACH(b, m->private_buses, i) {
-                r = send_message(b, NULL, userdata);
-                if (r < 0)
-                        ret = r;
-        }
-
-        if (m->api_bus) {
-                r = send_message(m->api_bus, NULL, userdata);
-                if (r < 0)
-                        ret = r;
-        }
-
-        return ret;
-}
-
-static int send_finished(sd_bus *bus, const char *destination, void *userdata) {
+static int send_finished(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *message = NULL;
         usec_t *times = userdata;
         int r;
@@ -1706,7 +1685,7 @@ static int send_finished(sd_bus *bus, const char *destination, void *userdata) {
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, message, destination, NULL);
+        return sd_bus_send(bus, message, NULL);
 }
 
 void bus_manager_send_finished(
@@ -1722,13 +1701,23 @@ void bus_manager_send_finished(
 
         assert(m);
 
-        r = bus_manager_foreach_client(m, send_finished,
-                                   (usec_t[6]) { firmware_usec, loader_usec, kernel_usec, initrd_usec, userspace_usec, total_usec });
+        r = bus_foreach_bus(
+                        m,
+                        NULL,
+                        send_finished,
+                        (usec_t[6]) {
+                                firmware_usec,
+                                loader_usec,
+                                kernel_usec,
+                                initrd_usec,
+                                userspace_usec,
+                                total_usec
+                        });
         if (r < 0)
                 log_debug("Failed to send finished signal: %s", strerror(-r));
 }
 
-static int send_reloading(sd_bus *bus, const char *destination, void *userdata) {
+static int send_reloading(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *message = NULL;
         int r;
 
@@ -1742,7 +1731,7 @@ static int send_reloading(sd_bus *bus, const char *destination, void *userdata)
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, message, destination, NULL);
+        return sd_bus_send(bus, message, NULL);
 }
 
 void bus_manager_send_reloading(Manager *m, bool active) {
@@ -1750,7 +1739,7 @@ void bus_manager_send_reloading(Manager *m, bool active) {
 
         assert(m);
 
-        r = bus_manager_foreach_client(m, send_reloading, INT_TO_PTR(active));
+        r = bus_foreach_bus(m, NULL, send_reloading, INT_TO_PTR(active));
         if (r < 0)
                 log_debug("Failed to send reloading signal: %s", strerror(-r));
 
diff --git a/src/core/dbus-manager.h b/src/core/dbus-manager.h
index 0ef99fad41..e1903fa16a 100644
--- a/src/core/dbus-manager.h
+++ b/src/core/dbus-manager.h
@@ -26,7 +26,5 @@
 
 extern const sd_bus_vtable bus_manager_vtable[];
 
-int bus_manager_foreach_client(Manager *m, int (*send_message)(sd_bus *bus, const char *destination, void *userdata), void *userdata);
-
 void bus_manager_send_finished(Manager *m, usec_t firmware_usec, usec_t loader_usec, usec_t kernel_usec, usec_t initrd_usec, usec_t userspace_usec, usec_t total_usec);
 void bus_manager_send_reloading(Manager *m, bool active);
diff --git a/src/core/dbus-unit.c b/src/core/dbus-unit.c
index 24d8a598e7..515ac8b78c 100644
--- a/src/core/dbus-unit.c
+++ b/src/core/dbus-unit.c
@@ -26,10 +26,10 @@
 #include "strv.h"
 #include "path-util.h"
 #include "fileio.h"
-#include "dbus-unit.h"
-#include "dbus-manager.h"
 #include "bus-errors.h"
-#include "dbus-client-track.h"
+#include "dbus.h"
+#include "dbus-manager.h"
+#include "dbus-unit.h"
 
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_load_state, unit_load_state, UnitLoadState);
 static BUS_DEFINE_PROPERTY_GET_ENUM(property_get_job_mode, job_mode, JobMode);
@@ -589,7 +589,7 @@ const sd_bus_vtable bus_unit_cgroup_vtable[] = {
         SD_BUS_VTABLE_END
 };
 
-static int send_new_signal(sd_bus *bus, const char *destination, void *userdata) {
+static int send_new_signal(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         _cleanup_free_ char *p = NULL;
         Unit *u = userdata;
@@ -615,10 +615,10 @@ static int send_new_signal(sd_bus *bus, const char *destination, void *userdata)
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, m, destination, NULL);
+        return sd_bus_send(bus, m, NULL);
 }
 
-static int send_changed_signal(sd_bus *bus, const char *destination, void *userdata) {
+static int send_changed_signal(sd_bus *bus, void *userdata) {
         _cleanup_free_ char *p = NULL;
         Unit *u = userdata;
         int r;
@@ -667,14 +667,14 @@ void bus_unit_send_change_signal(Unit *u) {
         if (!u->id)
                 return;
 
-        r = bus_manager_foreach_client(u->manager, u->sent_dbus_new_signal ? send_changed_signal : send_new_signal, u);
+        r = bus_foreach_bus(u->manager, NULL, u->sent_dbus_new_signal ? send_changed_signal : send_new_signal, u);
         if (r < 0)
                 log_debug("Failed to send unit change signal for %s: %s", u->id, strerror(-r));
 
         u->sent_dbus_new_signal = true;
 }
 
-static int send_removed_signal(sd_bus *bus, const char *destination, void *userdata) {
+static int send_removed_signal(sd_bus *bus, void *userdata) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         _cleanup_free_ char *p = NULL;
         Unit *u = userdata;
@@ -700,7 +700,7 @@ static int send_removed_signal(sd_bus *bus, const char *destination, void *userd
         if (r < 0)
                 return r;
 
-        return sd_bus_send_to(bus, m, destination, NULL);
+        return sd_bus_send(bus, m, NULL);
 }
 
 void bus_unit_send_removed_signal(Unit *u) {
@@ -713,7 +713,7 @@ void bus_unit_send_removed_signal(Unit *u) {
         if (!u->id)
                 return;
 
-        r = bus_manager_foreach_client(u->manager, send_removed_signal, u);
+        r = bus_foreach_bus(u->manager, NULL, send_removed_signal, u);
         if (r < 0)
                 log_debug("Failed to send unit remove signal for %s: %s", u->id, strerror(-r));
 }
@@ -765,9 +765,17 @@ int bus_unit_queue_job(
         if (r < 0)
                 return r;
 
-        r = bus_client_track(&j->subscribed, bus, sd_bus_message_get_sender(message));
-        if (r < 0)
-                return r;
+        if (bus == u->manager->api_bus) {
+                if (!j->subscribed) {
+                        r = sd_bus_track_new(bus, &j->subscribed, NULL, NULL);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = sd_bus_track_add_sender(j->subscribed, message);
+                if (r < 0)
+                        return r;
+        }
 
         path = job_dbus_path(j);
         if (!path)
diff --git a/src/core/dbus.c b/src/core/dbus.c
index 1059415711..be8dfc90f8 100644
--- a/src/core/dbus.c
+++ b/src/core/dbus.c
@@ -41,7 +41,6 @@
 #include "bus-error.h"
 #include "bus-errors.h"
 #include "strxcpyx.h"
-#include "dbus-client-track.h"
 #include "bus-internal.h"
 #include "selinux-access.h"
 
@@ -1040,9 +1039,12 @@ static void destroy_bus(Manager *m, sd_bus **bus) {
                 return;
 
         /* Get rid of tracked clients on this bus */
-        bus_client_untrack_bus(m->subscribed, *bus);
+        if (m->subscribed && sd_bus_track_get_bus(m->subscribed) == *bus)
+                m->subscribed = sd_bus_track_unref(m->subscribed);
+
         HASHMAP_FOREACH(j, m->jobs, i)
-                bus_client_untrack_bus(j->subscribed, *bus);
+                if (j->subscribed && sd_bus_track_get_bus(j->subscribed) == *bus)
+                        j->subscribed = sd_bus_track_unref(j->subscribed);
 
         /* Get rid of queued message on this bus */
         if (m->queued_message_bus == *bus) {
@@ -1075,7 +1077,11 @@ void bus_done(Manager *m) {
                 destroy_bus(m, &b);
 
         set_free(m->private_buses);
-        set_free(m->subscribed);
+        m->private_buses = NULL;
+
+        m->subscribed = sd_bus_track_unref(m->subscribed);
+        strv_free(m->deserialized_subscribed);
+        m->deserialized_subscribed = NULL;
 
         if (m->private_listen_event_source)
                 m->private_listen_event_source = sd_event_source_unref(m->private_listen_event_source);
@@ -1126,16 +1132,85 @@ int bus_fdset_add_all(Manager *m, FDSet *fds) {
         return 0;
 }
 
-void bus_serialize(Manager *m, FILE *f) {
-        assert(m);
+int bus_foreach_bus(
+                Manager *m,
+                sd_bus_track *subscribed2,
+                int (*send_message)(sd_bus *bus, void *userdata),
+                void *userdata) {
+
+        Iterator i;
+        sd_bus *b;
+        int r, ret = 0;
+
+        /* Send to all direct busses, unconditionally */
+        SET_FOREACH(b, m->private_buses, i) {
+                r = send_message(b, userdata);
+                if (r < 0)
+                        ret = r;
+        }
+
+        /* Send to API bus, but only if somebody is subscribed */
+        if (sd_bus_track_count(m->subscribed) > 0 ||
+            sd_bus_track_count(subscribed2) > 0) {
+                r = send_message(m->api_bus, userdata);
+                if (r < 0)
+                        ret = r;
+        }
+
+        return ret;
+}
+
+void bus_track_serialize(sd_bus_track *t, FILE *f) {
+        const char *n;
+
+        assert(t);
         assert(f);
 
-        bus_client_track_serialize(m, f, m->subscribed);
+        for (n = sd_bus_track_first(t); n; n = sd_bus_track_next(t))
+                fprintf(f, "subscribed=%s\n", n);
 }
 
-int bus_deserialize_item(Manager *m, const char *line) {
-        assert(m);
+int bus_track_deserialize_item(char ***l, const char *line) {
+        const char *e;
+
+        assert(l);
         assert(line);
 
-        return bus_client_track_deserialize_item(m, &m->subscribed, line);
+        e = startswith(line, "subscribed=");
+        if (!e)
+                return 0;
+
+        return strv_extend(l, e);
+}
+
+int bus_track_coldplug(Manager *m, sd_bus_track **t, char ***l) {
+        int r = 0;
+
+        assert(m);
+        assert(t);
+        assert(l);
+
+        if (!strv_isempty(*l) && m->api_bus) {
+                char **i;
+
+                if (!*t) {
+                        r = sd_bus_track_new(m->api_bus, t, NULL, NULL);
+                        if (r < 0)
+                                return r;
+                }
+
+                r = 0;
+                STRV_FOREACH(i, *l) {
+                        int k;
+
+                        k = sd_bus_track_add_name(*t, *i);
+                        if (k < 0)
+                                r = k;
+                }
+        }
+
+        strv_free(*l);
+        *l = NULL;
+
+        return r;
 }
diff --git a/src/core/dbus.h b/src/core/dbus.h
index a3bef47d5d..bfb236ec8e 100644
--- a/src/core/dbus.h
+++ b/src/core/dbus.h
@@ -30,5 +30,8 @@ void bus_done(Manager *m);
 
 int bus_fdset_add_all(Manager *m, FDSet *fds);
 
-void bus_serialize(Manager *m, FILE *f);
-int bus_deserialize_item(Manager *m, const char *line);
+void bus_track_serialize(sd_bus_track *t, FILE *f);
+int bus_track_deserialize_item(char ***l, const char *line);
+int bus_track_coldplug(Manager *m, sd_bus_track **t, char ***l);
+
+int bus_foreach_bus(Manager *m, sd_bus_track *subscribed2, int (*send_message)(sd_bus *bus, void *userdata), void *userdata);
diff --git a/src/core/job.c b/src/core/job.c
index 0cd4397bf2..9c099c686f 100644
--- a/src/core/job.c
+++ b/src/core/job.c
@@ -37,7 +37,7 @@
 #include "special.h"
 #include "async.h"
 #include "virt.h"
-#include "dbus-client-track.h"
+#include "dbus.h"
 
 Job* job_new_raw(Unit *unit) {
         Job *j;
@@ -90,7 +90,8 @@ void job_free(Job *j) {
 
         sd_event_source_unref(j->timer_event_source);
 
-        bus_client_track_free(j->subscribed);
+        sd_bus_track_unref(j->subscribed);
+        strv_free(j->deserialized_subscribed);
 
         free(j);
 }
@@ -931,7 +932,7 @@ int job_serialize(Job *j, FILE *f, FDSet *fds) {
         if (j->begin_usec > 0)
                 fprintf(f, "job-begin="USEC_FMT"\n", j->begin_usec);
 
-        bus_client_track_serialize(j->manager, f, j->subscribed);
+        bus_track_serialize(j->subscribed, f);
 
         /* End marker */
         fputc('\n', f);
@@ -1035,13 +1036,10 @@ int job_deserialize(Job *j, FILE *f, FDSet *fds) {
                         else
                                 j->begin_usec = ull;
 
-                } else {
-                        char t[strlen(l) + 1 + strlen(v) + 1];
+                } else if (streq(l, "subscribed")) {
 
-                        strcpy(stpcpy(stpcpy(t, l), "="), v);
-
-                        if (bus_client_track_deserialize_item(j->manager, &j->subscribed, t) == 0)
-                                log_debug("Unknown deserialization key '%s'", l);
+                        if (strv_extend(&j->deserialized_subscribed, v) < 0)
+                                return log_oom();
                 }
         }
 }
@@ -1051,6 +1049,12 @@ int job_coldplug(Job *j) {
 
         assert(j);
 
+        /* After deserialization is complete and the bus connection
+         * set up again, let's start watching our subscribers again */
+        r = bus_track_coldplug(j->manager, &j->subscribed, &j->deserialized_subscribed);
+        if (r < 0)
+                return r;
+
         if (j->begin_usec == 0 || j->unit->job_timeout == 0)
                 return 0;
 
diff --git a/src/core/job.h b/src/core/job.h
index 8cc3a02192..30d41d9edd 100644
--- a/src/core/job.h
+++ b/src/core/job.h
@@ -146,7 +146,8 @@ struct Job {
         usec_t begin_usec;
 
         /* There can be more than one client, because of job merging. */
-        Set *subscribed;
+        sd_bus_track *subscribed;
+        char **deserialized_subscribed;
 
         JobResult result;
 
diff --git a/src/core/manager.c b/src/core/manager.c
index f5801b4749..9172a244ae 100644
--- a/src/core/manager.c
+++ b/src/core/manager.c
@@ -839,7 +839,7 @@ int manager_enumerate(Manager *m) {
 }
 
 static int manager_coldplug(Manager *m) {
-        int r = 0, q;
+        int r = 0;
         Iterator i;
         Unit *u;
         char *k;
@@ -848,12 +848,14 @@ static int manager_coldplug(Manager *m) {
 
         /* Then, let's set up their initial state. */
         HASHMAP_FOREACH_KEY(u, k, m->units, i) {
+                int q;
 
                 /* ignore aliases */
                 if (u->id != k)
                         continue;
 
-                if ((q = unit_coldplug(u)) < 0)
+                q = unit_coldplug(u);
+                if (q < 0)
                         r = q;
         }
 
@@ -996,6 +998,7 @@ int manager_startup(Manager *m, FILE *serialization, FDSet *fds) {
          * didn't, then let's create the bus now. */
         manager_setup_kdbus(m);
         manager_connect_bus(m, !!serialization);
+        bus_track_coldplug(m, &m->subscribed, &m->deserialized_subscribed);
 
         /* Third, fire things up! */
         q = manager_coldplug(m);
@@ -2102,7 +2105,7 @@ int manager_serialize(Manager *m, FILE *f, FDSet *fds, bool switching_root) {
                 fprintf(f, "kdbus-fd=%i\n", copy);
         }
 
-        bus_serialize(m, f);
+        bus_track_serialize(m->subscribed, f);
 
         fputc('\n', f);
 
@@ -2279,7 +2282,7 @@ int manager_deserialize(Manager *m, FILE *f, FDSet *fds) {
                                 m->kdbus_fd = fdset_remove(fds, fd);
                         }
 
-                } else if (bus_deserialize_item(m, l) == 0)
+                } else if (bus_track_deserialize_item(&m->deserialized_subscribed, l) == 0)
                         log_debug("Unknown serialization item '%s'", l);
         }
 
diff --git a/src/core/manager.h b/src/core/manager.h
index 9dee48ddde..398c8e642e 100644
--- a/src/core/manager.h
+++ b/src/core/manager.h
@@ -167,7 +167,13 @@ struct Manager {
         Set *private_buses;
         int private_listen_fd;
         sd_event_source *private_listen_event_source;
-        Set *subscribed;
+
+        /* Contains all the clients that are subscribed to signals via
+        the API bus. Note that private bus connections are always
+        considered subscribes, since they last for very short only,
+        and it is much simpler that way. */
+        sd_bus_track *subscribed;
+        char **deserialized_subscribed;
 
         sd_bus_message *queued_message; /* This is used during reloading:
                                       * before the reload we queue the
diff --git a/src/core/unit.c b/src/core/unit.c
index 05470739d2..1c0b0c72ac 100644
--- a/src/core/unit.c
+++ b/src/core/unit.c
@@ -328,7 +328,8 @@ void unit_add_to_dbus_queue(Unit *u) {
                 return;
 
         /* Shortcut things if nobody cares */
-        if (set_isempty(u->manager->subscribed)) {
+        if (sd_bus_track_count(u->manager->subscribed) <= 0 &&
+            set_isempty(u->manager->private_buses)) {
                 u->sent_dbus_new_signal = true;
                 return;
         }
diff --git a/src/libsystemd/libsystemd.sym.m4 b/src/libsystemd/libsystemd.sym.m4
index 8d34615bc7..c708c7f38f 100644
--- a/src/libsystemd/libsystemd.sym.m4
+++ b/src/libsystemd/libsystemd.sym.m4
@@ -313,6 +313,18 @@ m4_ifdef(`ENABLE_KDBUS',
         sd_bus_error_has_name;
         sd_bus_label_escape;
         sd_bus_label_unescape;
+        sd_bus_track_new;
+        sd_bus_track_ref;
+        sd_bus_track_unref;
+        sd_bus_track_get_bus;
+        sd_bus_track_add_sender;
+        sd_bus_track_remove_sender;
+        sd_bus_track_add_name;
+        sd_bus_track_remove_name;
+        sd_bus_track_count;
+        sd_bus_track_contains;
+        sd_bus_track_first;
+        sd_bus_track_next;
 
         /* sd-memfd */
         sd_memfd_new;
diff --git a/src/libsystemd/sd-bus/bus-internal.h b/src/libsystemd/sd-bus/bus-internal.h
index a4160ef4a1..ae5f66288f 100644
--- a/src/libsystemd/sd-bus/bus-internal.h
+++ b/src/libsystemd/sd-bus/bus-internal.h
@@ -274,6 +274,8 @@ struct sd_bus {
 
         size_t bloom_size;
         unsigned bloom_n_hash;
+
+        sd_bus_track *track_queue;
 };
 
 #define BUS_DEFAULT_TIMEOUT ((usec_t) (25 * USEC_PER_SEC))
diff --git a/src/libsystemd/sd-bus/bus-track.c b/src/libsystemd/sd-bus/bus-track.c
new file mode 100644
index 0000000000..4a5056e434
--- /dev/null
+++ b/src/libsystemd/sd-bus/bus-track.c
@@ -0,0 +1,314 @@
+/*-*- Mode: C; c-basic-offset: 8; indent-tabs-mode: nil -*-*/
+
+/***
+  This file is part of systemd.
+
+  Copyright 2013 Lennart Poettering
+
+  systemd is free software; you can redistribute it and/or modify it
+  under the terms of the GNU Lesser General Public License as published by
+  the Free Software Foundation; either version 2.1 of the License, or
+  (at your option) any later version.
+
+  systemd is distributed in the hope that it will be useful, but
+  WITHOUT ANY WARRANTY; without even the implied warranty of
+  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
+  Lesser General Public License for more details.
+
+  You should have received a copy of the GNU Lesser General Public License
+  along with systemd; If not, see <http://www.gnu.org/licenses/>.
+***/
+
+#include "sd-bus.h"
+#include "set.h"
+#include "bus-internal.h"
+#include "bus-track.h"
+
+struct sd_bus_track {
+        unsigned n_ref;
+        sd_bus *bus;
+        sd_bus_track_handler_t handler;
+        void *userdata;
+        Set *names;
+        LIST_FIELDS(sd_bus_track, queue);
+        Iterator iterator;
+        bool in_queue;
+        bool modified;
+};
+
+#define MATCH_PREFIX                                        \
+        "type='signal',"                                    \
+        "sender='org.freedesktop.DBus',"                    \
+        "path='/org/freedesktop/DBus',"                     \
+        "interface='org.freedesktop.DBus',"                 \
+        "member='NameOwnerChanged',"                        \
+        "arg0='"
+
+#define MATCH_SUFFIX \
+        "'"
+
+#define MATCH_FOR_NAME(name)                                            \
+        ({                                                              \
+                char *_x;                                               \
+                size_t _l = strlen(name);                               \
+                _x = alloca(sizeof(MATCH_PREFIX)-1+_l+sizeof(MATCH_SUFFIX)); \
+                strcpy(stpcpy(stpcpy(_x, MATCH_PREFIX), name), MATCH_SUFFIX); \
+                _x;                                                     \
+        })
+
+static void bus_track_add_to_queue(sd_bus_track *track) {
+        assert(track);
+
+        if (track->in_queue)
+                return;
+
+        if (!track->handler)
+                return;
+
+        LIST_PREPEND(queue, track->bus->track_queue, track);
+        track->in_queue = true;
+}
+
+static void bus_track_remove_from_queue(sd_bus_track *track) {
+        assert(track);
+
+        if (!track->in_queue)
+                return;
+
+        LIST_REMOVE(queue, track->bus->track_queue, track);
+        track->in_queue = false;
+}
+
+_public_ int sd_bus_track_new(
+                sd_bus *bus,
+                sd_bus_track **track,
+                sd_bus_track_handler_t handler,
+                void *userdata) {
+
+        sd_bus_track *t;
+
+        assert_return(bus, -EINVAL);
+        assert_return(track, -EINVAL);
+
+        t = new0(sd_bus_track, 1);
+        if (!t)
+                return -ENOMEM;
+
+        t->n_ref = 1;
+        t->handler = handler;
+        t->userdata = userdata;
+        t->bus = sd_bus_ref(bus);
+
+        bus_track_add_to_queue(t);
+
+        *track = t;
+        return 0;
+}
+
+_public_ sd_bus_track* sd_bus_track_ref(sd_bus_track *track) {
+        assert_return(track, NULL);
+
+        assert(track->n_ref > 0);
+
+        track->n_ref++;
+
+        return track;
+}
+
+_public_ sd_bus_track* sd_bus_track_unref(sd_bus_track *track) {
+        const char *n;
+
+        if (!track)
+                return NULL;
+
+        assert(track->n_ref > 0);
+
+        if (track->n_ref > 1) {
+                track->n_ref --;
+                return NULL;
+        }
+
+        while ((n = set_first(track->names)))
+                sd_bus_track_remove_name(track, n);
+
+        bus_track_remove_from_queue(track);
+        set_free(track->names);
+        sd_bus_unref(track->bus);
+        free(track);
+
+        return NULL;
+}
+
+static int on_name_owner_changed(sd_bus *bus, sd_bus_message *message, void *userdata, sd_bus_error *error) {
+        sd_bus_track *track = userdata;
+        const char *name, *old, *new;
+        int r;
+
+        assert(bus);
+        assert(message);
+        assert(track);
+
+        r = sd_bus_message_read(message, "sss", &name, &old, &new);
+        if (r < 0)
+                return 0;
+
+        sd_bus_track_remove_name(track, name);
+        return 0;
+}
+
+_public_ int sd_bus_track_add_name(sd_bus_track *track, const char *name) {
+        _cleanup_free_ char *n = NULL;
+        const char *match;
+        int r;
+
+        assert_return(track, -EINVAL);
+        assert_return(service_name_is_valid(name), -EINVAL);
+
+        r = set_ensure_allocated(&track->names, string_hash_func, string_compare_func);
+        if (r < 0)
+                return r;
+
+        n = strdup(name);
+        if (!n)
+                return -ENOMEM;
+
+        r = set_put(track->names, n);
+        if (r == -EEXIST)
+                return 0;
+        if (r < 0)
+                return r;
+
+        /* First, subscribe to this name */
+        match = MATCH_FOR_NAME(name);
+        r = sd_bus_add_match(track->bus, match, on_name_owner_changed, track);
+        if (r < 0) {
+                set_remove(track->names, n);
+                return r;
+        }
+
+        /* Second, check if it is currently existing, or maybe
+         * doesn't, or maybe disappeared already. */
+        r = sd_bus_get_owner(track->bus, name, 0, NULL);
+        if (r < 0) {
+                set_remove(track->names, n);
+                sd_bus_remove_match(track->bus, match, on_name_owner_changed, track);
+                return r;
+        }
+
+        n = NULL;
+
+        bus_track_remove_from_queue(track);
+        track->modified = true;
+
+        return 1;
+}
+
+_public_ int sd_bus_track_remove_name(sd_bus_track *track, const char *name) {
+        const char *match;
+        _cleanup_free_ char *n;
+
+        assert_return(name, -EINVAL);
+
+        if (!track)
+                return 0;
+
+        n = set_remove(track->names, (char*) name);
+        if (!n)
+                return 0;
+
+        match = MATCH_FOR_NAME(n);
+        sd_bus_remove_match(track->bus, match, on_name_owner_changed, track);
+
+        if (set_isempty(track->names))
+                bus_track_add_to_queue(track);
+
+        track->modified = true;
+
+        return 1;
+}
+
+_public_ unsigned sd_bus_track_count(sd_bus_track *track) {
+        if (!track)
+                return 0;
+
+        return set_size(track->names);
+}
+
+_public_ const char* sd_bus_track_contains(sd_bus_track *track, const char *name) {
+        assert_return(track, NULL);
+        assert_return(name, NULL);
+
+        return set_get(track->names, (void*) name);
+}
+
+_public_ const char* sd_bus_track_first(sd_bus_track *track) {
+        if (!track)
+                return NULL;
+
+        track->modified = false;
+        track->iterator = NULL;
+
+        return set_iterate(track->names, &track->iterator);
+}
+
+_public_ const char* sd_bus_track_next(sd_bus_track *track) {
+        if (!track)
+                return NULL;
+
+        if (track->modified)
+                return NULL;
+
+        return set_iterate(track->names, &track->iterator);
+}
+
+_public_ int sd_bus_track_add_sender(sd_bus_track *track, sd_bus_message *m) {
+        const char *sender;
+
+        assert_return(track, -EINVAL);
+        assert_return(m, -EINVAL);
+
+        sender = sd_bus_message_get_sender(m);
+        if (!sender)
+                return -EINVAL;
+
+        return sd_bus_track_add_name(track, sender);
+}
+
+_public_ int sd_bus_track_remove_sender(sd_bus_track *track, sd_bus_message *m) {
+        const char *sender;
+
+        assert_return(track, -EINVAL);
+        assert_return(m, -EINVAL);
+
+        sender = sd_bus_message_get_sender(m);
+        if (!sender)
+                return -EINVAL;
+
+        return sd_bus_track_remove_name(track, sender);
+}
+
+_public_ sd_bus* sd_bus_track_get_bus(sd_bus_track *track) {
+        assert_return(track, NULL);
+
+        return track->bus;
+}
+
+void bus_track_dispatch(sd_bus_track *track) {
+        int r;
+
+        assert(track);
+        assert(track->in_queue);
+        assert(track->handler);
+
+        bus_track_remove_from_queue(track);
+
+        sd_bus_track_ref(track);
+
+        r = track->handler(track, track->userdata);
+        if (r < 0)
+                log_debug("Failed to process track handler: %s", strerror(-r));
+        else if (r == 0)
+                bus_track_add_to_queue(track);
+
+        sd_bus_track_unref(track);
+}
diff --git a/src/core/dbus-client-track.h b/src/libsystemd/sd-bus/bus-track.h
index 01676479b0..f8690a5239 100644
--- a/src/core/dbus-client-track.h
+++ b/src/libsystemd/sd-bus/bus-track.h
@@ -21,22 +21,4 @@
   along with systemd; If not, see <http://www.gnu.org/licenses/>.
 ***/
 
-#include "sd-bus.h"
-#include "set.h"
-#include "manager.h"
-
-typedef struct BusTrackedClient {
-        Set *set;
-        sd_bus *bus;
-        char name[0];
-} BusTrackedClient;
-
-int bus_client_track(Set **s, sd_bus *bus, const char *name);
-
-int bus_client_untrack(Set *s, sd_bus *bus, const char *name);
-int bus_client_untrack_bus(Set *s, sd_bus *bus);
-
-void bus_client_track_free(Set *s);
-
-void bus_client_track_serialize(Manager *m, FILE *f, Set *s);
-int bus_client_track_deserialize_item(Manager *m, Set **s, const char *line);
+void bus_track_dispatch(sd_bus_track *track);
diff --git a/src/libsystemd/sd-bus/sd-bus.c b/src/libsystemd/sd-bus/sd-bus.c
index 636715f759..fbf1a5919f 100644
--- a/src/libsystemd/sd-bus/sd-bus.c
+++ b/src/libsystemd/sd-bus/sd-bus.c
@@ -51,6 +51,7 @@
 #include "bus-util.h"
 #include "bus-container.h"
 #include "bus-protocol.h"
+#include "bus-track.h"
 
 static int bus_poll(sd_bus *bus, bool need_more, uint64_t timeout_usec);
 static int attach_io_events(sd_bus *b);
@@ -131,6 +132,8 @@ static void bus_free(sd_bus *b) {
 
         assert(b);
 
+        assert(!b->track_queue);
+
         sd_bus_detach_event(b);
 
         if (b->default_bus_ptr)
@@ -2000,6 +2003,11 @@ _public_ int sd_bus_get_timeout(sd_bus *bus, uint64_t *timeout_usec) {
         assert_return(BUS_IS_OPEN(bus->state) || bus->state == BUS_CLOSING, -ENOTCONN);
         assert_return(!bus_pid_changed(bus), -ECHILD);
 
+        if (bus->track_queue) {
+                *timeout_usec = 0;
+                return 1;
+        }
+
         if (bus->state == BUS_CLOSING) {
                 *timeout_usec = 0;
                 return 1;
@@ -2282,6 +2290,16 @@ finish:
         return r;
 }
 
+static int dispatch_track(sd_bus *bus) {
+        assert(bus);
+
+        if (!bus->track_queue)
+                return 0;
+
+        bus_track_dispatch(bus->track_queue);
+        return 1;
+}
+
 static int process_running(sd_bus *bus, bool hint_priority, int64_t priority, sd_bus_message **ret) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         int r;
@@ -2297,6 +2315,10 @@ static int process_running(sd_bus *bus, bool hint_priority, int64_t priority, sd
         if (r != 0)
                 goto null_message;
 
+        r = dispatch_track(bus);
+        if (r != 0)
+                goto null_message;
+
         r = dispatch_rqueue(bus, hint_priority, priority, &m);
         if (r < 0)
                 return r;
diff --git a/src/systemd/sd-bus.h b/src/systemd/sd-bus.h
index 0629e47dea..e26ca6b704 100644
--- a/src/systemd/sd-bus.h
+++ b/src/systemd/sd-bus.h
@@ -38,6 +38,7 @@ _SD_BEGIN_DECLARATIONS;
 typedef struct sd_bus sd_bus;
 typedef struct sd_bus_message sd_bus_message;
 typedef struct sd_bus_creds sd_bus_creds;
+typedef struct sd_bus_track sd_bus_track;
 
 typedef struct {
         const char *name;
@@ -89,6 +90,7 @@ typedef int (*sd_bus_property_get_t) (sd_bus *bus, const char *path, const char
 typedef int (*sd_bus_property_set_t) (sd_bus *bus, const char *path, const char *interface, const char *property, sd_bus_message *value, void *userdata, sd_bus_error *ret_error);
 typedef int (*sd_bus_object_find_t) (sd_bus *bus, const char *path, const char *interface, void *userdata, void **ret_found, sd_bus_error *ret_error);
 typedef int (*sd_bus_node_enumerator_t) (sd_bus *bus, const char *path, void *userdata, char ***ret_nodes, sd_bus_error *ret_error);
+typedef int (*sd_bus_track_handler_t) (sd_bus_track *track, void *userdata);
 
 #include "sd-bus-protocol.h"
 #include "sd-bus-vtable.h"
@@ -350,6 +352,23 @@ int sd_bus_error_has_name(const sd_bus_error *e, const char *name);
 char *sd_bus_label_escape(const char *s);
 char *sd_bus_label_unescape(const char *f);
 
+/* Tracking peers */
+
+int sd_bus_track_new(sd_bus *bus, sd_bus_track **track, sd_bus_track_handler_t handler, void *userdata);
+sd_bus_track* sd_bus_track_ref(sd_bus_track *track);
+sd_bus_track* sd_bus_track_unref(sd_bus_track *track);
+sd_bus* sd_bus_track_get_bus(sd_bus_track *track);
+
+int sd_bus_track_add_sender(sd_bus_track *track, sd_bus_message *m);
+int sd_bus_track_remove_sender(sd_bus_track *track, sd_bus_message *m);
+int sd_bus_track_add_name(sd_bus_track *track, const char *name);
+int sd_bus_track_remove_name(sd_bus_track *track, const char *name);
+
+unsigned sd_bus_track_count(sd_bus_track *track);
+const char* sd_bus_track_contains(sd_bus_track *track, const char *names);
+const char* sd_bus_track_first(sd_bus_track *track);
+const char* sd_bus_track_next(sd_bus_track *track);
+
 _SD_END_DECLARATIONS;
 
 #endif