bus: add the ability for backends to queue to input messages at the same time

We need this so that one incoming kernel message can result in two
high-level bus messages, for the case where we synthesize NameAcquired
and NameOwnerChanged in the same instance.

6 files changed, 122 insertions, 88 deletions

diff --git a/src/libsystemd-bus/bus-internal.h b/src/libsystemd-bus/bus-internal.h
index 7a7d8f5ffb..f21cf87ea2 100644
--- a/src/libsystemd-bus/bus-internal.h
+++ b/src/libsystemd-bus/bus-internal.h
@@ -166,7 +166,7 @@ struct sd_bus {
         size_t rbuffer_size;
 
         sd_bus_message **rqueue;
-        unsigned rqueue_size;
+        unsigned rqueue_size, rqueue_allocated;
 
         sd_bus_message **wqueue;
         unsigned wqueue_size;
@@ -296,6 +296,9 @@ int bus_next_address(sd_bus *bus);
 
 int bus_seal_message(sd_bus *b, sd_bus_message *m);
 
+int bus_rqueue_make_room(sd_bus *bus, unsigned n);
+int bus_rqueue_push(sd_bus *bus, sd_bus_message *m);
+
 bool bus_pid_changed(sd_bus *bus);
 
 char *bus_address_escape(const char *v);
diff --git a/src/libsystemd-bus/bus-kernel.c b/src/libsystemd-bus/bus-kernel.c
index cffdf09953..54e85c9443 100644
--- a/src/libsystemd-bus/bus-kernel.c
+++ b/src/libsystemd-bus/bus-kernel.c
@@ -425,12 +425,11 @@ static void close_kdbus_msg(sd_bus *bus, struct kdbus_msg *k) {
         }
 }
 
-static int return_name_owner_changed(sd_bus *bus, const char *name, const char *old_owner, const char *new_owner, sd_bus_message **ret) {
+static int push_name_owner_changed(sd_bus *bus, const char *name, const char *old_owner, const char *new_owner) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         int r;
 
         assert(bus);
-        assert(ret);
 
         r = sd_bus_message_new_signal(
                         bus,
@@ -451,19 +450,20 @@ static int return_name_owner_changed(sd_bus *bus, const char *name, const char *
         if (r < 0)
                 return r;
 
-        *ret = m;
-        m = NULL;
+        r = bus_rqueue_push(bus, m);
+        if (r < 0)
+                return r;
 
+        m = NULL;
         return 1;
 }
 
-static int translate_name_change(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d, sd_bus_message **ret) {
+static int translate_name_change(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d) {
         char new_owner[UNIQUE_NAME_MAX], old_owner[UNIQUE_NAME_MAX];
 
         assert(bus);
         assert(k);
         assert(d);
-        assert(ret);
 
         if (d->name_change.flags != 0)
                 return 0;
@@ -478,34 +478,31 @@ static int translate_name_change(sd_bus *bus, struct kdbus_msg *k, struct kdbus_
         else
                 sprintf(new_owner, ":1.%llu", (unsigned long long) d->name_change.new_id);
 
-        return return_name_owner_changed(bus, d->name_change.name, old_owner, new_owner, ret);
+        return push_name_owner_changed(bus, d->name_change.name, old_owner, new_owner);
 }
 
-static int translate_id_change(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d, sd_bus_message **ret) {
+static int translate_id_change(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d) {
         char owner[UNIQUE_NAME_MAX];
 
         assert(bus);
         assert(k);
         assert(d);
-        assert(ret);
 
         sprintf(owner, ":1.%llu", d->id_change.id);
 
-        return return_name_owner_changed(
+        return push_name_owner_changed(
                         bus, owner,
                         d->type == KDBUS_ITEM_ID_ADD ? NULL : owner,
-                        d->type == KDBUS_ITEM_ID_ADD ? owner : NULL,
-                        ret);
+                        d->type == KDBUS_ITEM_ID_ADD ? owner : NULL);
 }
 
-static int translate_reply(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d, sd_bus_message **ret) {
+static int translate_reply(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d) {
         _cleanup_bus_message_unref_ sd_bus_message *m = NULL;
         int r;
 
         assert(bus);
         assert(k);
         assert(d);
-        assert(ret);
 
         r = bus_message_new_synthetic_error(
                         bus,
@@ -523,16 +520,18 @@ static int translate_reply(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *
         if (r < 0)
                 return r;
 
-        *ret = m;
-        m = NULL;
+        r = bus_rqueue_push(bus, m);
+        if (r < 0)
+                return r;
 
+        m = NULL;
         return 1;
 }
 
-static int bus_kernel_translate_message(sd_bus *bus, struct kdbus_msg *k, sd_bus_message **ret) {
+static int bus_kernel_translate_message(sd_bus *bus, struct kdbus_msg *k) {
         struct kdbus_item *d, *found = NULL;
 
-        static int (* const translate[])(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d, sd_bus_message **ret) = {
+        static int (* const translate[])(sd_bus *bus, struct kdbus_msg *k, struct kdbus_item *d) = {
                 [KDBUS_ITEM_NAME_ADD - _KDBUS_ITEM_KERNEL_BASE] = translate_name_change,
                 [KDBUS_ITEM_NAME_REMOVE - _KDBUS_ITEM_KERNEL_BASE] = translate_name_change,
                 [KDBUS_ITEM_NAME_CHANGE - _KDBUS_ITEM_KERNEL_BASE] = translate_name_change,
@@ -546,7 +545,6 @@ static int bus_kernel_translate_message(sd_bus *bus, struct kdbus_msg *k, sd_bus
 
         assert(bus);
         assert(k);
-        assert(ret);
         assert(k->payload_type == KDBUS_PAYLOAD_KERNEL);
 
         KDBUS_PART_FOREACH(d, k, items) {
@@ -563,7 +561,7 @@ static int bus_kernel_translate_message(sd_bus *bus, struct kdbus_msg *k, sd_bus
                 return 0;
         }
 
-        return translate[found->type](bus, k, d, ret);
+        return translate[found->type](bus, k, d);
 }
 
 int kdbus_translate_attach_flags(uint64_t mask, uint64_t *kdbus_mask) {
@@ -599,7 +597,7 @@ int kdbus_translate_attach_flags(uint64_t mask, uint64_t *kdbus_mask) {
         return 0;
 }
 
-static int bus_kernel_make_message(sd_bus *bus, struct kdbus_msg *k, sd_bus_message **ret) {
+static int bus_kernel_make_message(sd_bus *bus, struct kdbus_msg *k) {
         sd_bus_message *m = NULL;
         struct kdbus_item *d;
         unsigned n_fds = 0;
@@ -611,7 +609,6 @@ static int bus_kernel_make_message(sd_bus *bus, struct kdbus_msg *k, sd_bus_mess
 
         assert(bus);
         assert(k);
-        assert(ret);
         assert(k->payload_type == KDBUS_PAYLOAD_DBUS1);
 
         KDBUS_PART_FOREACH(d, k, items) {
@@ -833,7 +830,10 @@ static int bus_kernel_make_message(sd_bus *bus, struct kdbus_msg *k, sd_bus_mess
 
         fds = NULL;
 
-        *ret = m;
+        r = bus_rqueue_push(bus, m);
+        if (r < 0)
+                goto fail;
+
         return 1;
 
 fail:
@@ -852,13 +852,21 @@ fail:
         return r;
 }
 
-int bus_kernel_read_message(sd_bus *bus, sd_bus_message **m) {
-        uint64_t off;
+int bus_kernel_read_message(sd_bus *bus) {
         struct kdbus_msg *k;
+        uint64_t off;
         int r;
 
         assert(bus);
-        assert(m);
+
+        /* Kernel messages might result in 2 new queued messages in
+         * the worst case (NameOwnerChange and LostName for the same
+         * well-known name, for example). Let's make room in
+         * advance. */
+
+        r = bus_rqueue_make_room(bus, 2);
+        if (r < 0)
+                return r;
 
         r = ioctl(bus->input_fd, KDBUS_CMD_MSG_RECV, &off);
         if (r < 0) {
@@ -870,9 +878,9 @@ int bus_kernel_read_message(sd_bus *bus, sd_bus_message **m) {
         k = (struct kdbus_msg *)((uint8_t *)bus->kdbus_buffer + off);
 
         if (k->payload_type == KDBUS_PAYLOAD_DBUS1)
-                r = bus_kernel_make_message(bus, k, m);
+                r = bus_kernel_make_message(bus, k);
         else if (k->payload_type == KDBUS_PAYLOAD_KERNEL)
-                r = bus_kernel_translate_message(bus, k, m);
+                r = bus_kernel_translate_message(bus, k);
         else
                 r = 0;
 
diff --git a/src/libsystemd-bus/bus-kernel.h b/src/libsystemd-bus/bus-kernel.h
index 4b63108e8a..746ab227a4 100644
--- a/src/libsystemd-bus/bus-kernel.h
+++ b/src/libsystemd-bus/bus-kernel.h
@@ -58,7 +58,7 @@ int bus_kernel_connect(sd_bus *b);
 int bus_kernel_take_fd(sd_bus *b);
 
 int bus_kernel_write_message(sd_bus *bus, sd_bus_message *m);
-int bus_kernel_read_message(sd_bus *bus, sd_bus_message **m);
+int bus_kernel_read_message(sd_bus *bus);
 
 int bus_kernel_create(const char *name, char **s);
 
diff --git a/src/libsystemd-bus/bus-socket.c b/src/libsystemd-bus/bus-socket.c
index 6845f9d1bb..355f31c562 100644
--- a/src/libsystemd-bus/bus-socket.c
+++ b/src/libsystemd-bus/bus-socket.c
@@ -891,13 +891,12 @@ static int bus_socket_read_message_need(sd_bus *bus, size_t *need) {
         return 0;
 }
 
-static int bus_socket_make_message(sd_bus *bus, size_t size, sd_bus_message **m) {
+static int bus_socket_make_message(sd_bus *bus, size_t size) {
         sd_bus_message *t;
         void *b;
         int r;
 
         assert(bus);
-        assert(m);
         assert(bus->rbuffer_size >= size);
         assert(bus->state == BUS_RUNNING || bus->state == BUS_HELLO);
 
@@ -926,11 +925,16 @@ static int bus_socket_make_message(sd_bus *bus, size_t size, sd_bus_message **m)
         bus->fds = NULL;
         bus->n_fds = 0;
 
-        *m = t;
+        r = bus_rqueue_push(bus, t);
+        if (r < 0) {
+                sd_bus_message_unref(t);
+                return r;
+        }
+
         return 1;
 }
 
-int bus_socket_read_message(sd_bus *bus, sd_bus_message **m) {
+int bus_socket_read_message(sd_bus *bus) {
         struct msghdr mh;
         struct iovec iov;
         ssize_t k;
@@ -947,15 +951,18 @@ int bus_socket_read_message(sd_bus *bus, sd_bus_message **m) {
         bool handle_cmsg = false;
 
         assert(bus);
-        assert(m);
         assert(bus->state == BUS_RUNNING || bus->state == BUS_HELLO);
 
+        r = bus_rqueue_make_room(bus, 1);
+        if (r < 0)
+                return r;
+
         r = bus_socket_read_message_need(bus, &need);
         if (r < 0)
                 return r;
 
         if (bus->rbuffer_size >= need)
-                return bus_socket_make_message(bus, need, m);
+                return bus_socket_make_message(bus, need);
 
         b = realloc(bus->rbuffer, need);
         if (!b)
@@ -1045,7 +1052,7 @@ int bus_socket_read_message(sd_bus *bus, sd_bus_message **m) {
                 return r;
 
         if (bus->rbuffer_size >= need)
-                return bus_socket_make_message(bus, need, m);
+                return bus_socket_make_message(bus, need);
 
         return 1;
 }
diff --git a/src/libsystemd-bus/bus-socket.h b/src/libsystemd-bus/bus-socket.h
index c61b90f473..f959787e7d 100644
--- a/src/libsystemd-bus/bus-socket.h
+++ b/src/libsystemd-bus/bus-socket.h
@@ -30,7 +30,7 @@ int bus_socket_take_fd(sd_bus *b);
 int bus_socket_start_auth(sd_bus *b);
 
 int bus_socket_write_message(sd_bus *bus, sd_bus_message *m, size_t *idx);
-int bus_socket_read_message(sd_bus *bus, sd_bus_message **m);
+int bus_socket_read_message(sd_bus *bus);
 
 int bus_socket_process_opening(sd_bus *b);
 int bus_socket_process_authenticating(sd_bus *b);
diff --git a/src/libsystemd-bus/sd-bus.c b/src/libsystemd-bus/sd-bus.c
index a894af0851..86265955bb 100644
--- a/src/libsystemd-bus/sd-bus.c
+++ b/src/libsystemd-bus/sd-bus.c
@@ -1299,50 +1299,78 @@ static int dispatch_wqueue(sd_bus *bus) {
         return ret;
 }
 
-static int bus_read_message(sd_bus *bus, sd_bus_message **m) {
+static int bus_read_message(sd_bus *bus) {
+        assert(bus);
+
+        if (bus->is_kernel)
+                return bus_kernel_read_message(bus);
+        else
+                return bus_socket_read_message(bus);
+}
+
+int bus_rqueue_make_room(sd_bus *bus, unsigned n) {
+        sd_bus_message **q;
+        unsigned x;
+
+        x = bus->rqueue_size + n;
+
+        if (bus->rqueue_allocated >= x)
+                return 0;
+
+        if (x > BUS_RQUEUE_MAX)
+                return -ENOBUFS;
+
+        q = realloc(bus->rqueue, x * sizeof(sd_bus_message*));
+        if (!q)
+                return -ENOMEM;
+
+        bus->rqueue = q;
+        bus->rqueue_allocated = x;
+
+        return 0;
+}
+
+int bus_rqueue_push(sd_bus *bus, sd_bus_message *m) {
         int r;
 
         assert(bus);
         assert(m);
 
-        if (bus->is_kernel)
-                r = bus_kernel_read_message(bus, m);
-        else
-                r = bus_socket_read_message(bus, m);
+        r = bus_rqueue_make_room(bus, 1);
+        if (r < 0)
+                return r;
 
-        return r;
+        bus->rqueue[bus->rqueue_size++] = m;
+
+        return 0;
 }
 
 static int dispatch_rqueue(sd_bus *bus, sd_bus_message **m) {
-        sd_bus_message *z = NULL;
         int r, ret = 0;
 
         assert(bus);
         assert(m);
         assert(bus->state == BUS_RUNNING || bus->state == BUS_HELLO);
 
-        if (bus->rqueue_size > 0) {
-                /* Dispatch a queued message */
+        for (;;) {
+                if (bus->rqueue_size > 0) {
+                        /* Dispatch a queued message */
 
-                *m = bus->rqueue[0];
-                bus->rqueue_size --;
-                memmove(bus->rqueue, bus->rqueue + 1, sizeof(sd_bus_message*) * bus->rqueue_size);
-                return 1;
-        }
+                        *m = bus->rqueue[0];
+                        bus->rqueue_size --;
+                        memmove(bus->rqueue, bus->rqueue + 1, sizeof(sd_bus_message*) * bus->rqueue_size);
+                        return 1;
+                }
 
-        /* Try to read a new message */
-        do {
-                r = bus_read_message(bus, &z);
+                /* Try to read a new message */
+                r = bus_read_message(bus);
                 if (r < 0)
                         return r;
                 if (r == 0)
                         return ret;
 
                 ret = 1;
-        } while (!z);
-
-        *m = z;
-        return ret;
+        }
 }
 
 _public_ int sd_bus_send(sd_bus *bus, sd_bus_message *m, uint64_t *serial) {
@@ -1578,10 +1606,10 @@ _public_ int sd_bus_call(
                 sd_bus_error *error,
                 sd_bus_message **reply) {
 
-        int r;
         usec_t timeout;
         uint64_t serial;
-        bool room = false;
+        unsigned i;
+        int r;
 
         assert_return(bus, -EINVAL);
         assert_return(BUS_IS_OPEN(bus->state), -ENOTCONN);
@@ -1600,37 +1628,26 @@ _public_ int sd_bus_call(
                 return r;
 
         timeout = calc_elapse(usec);
+        i = bus->rqueue_size;
 
         for (;;) {
                 usec_t left;
-                sd_bus_message *incoming = NULL;
-
-                if (!room) {
-                        sd_bus_message **q;
-
-                        if (bus->rqueue_size >= BUS_RQUEUE_MAX)
-                                return -ENOBUFS;
 
-                        /* Make sure there's room for queuing this
-                         * locally, before we read the message */
-
-                        q = realloc(bus->rqueue, (bus->rqueue_size + 1) * sizeof(sd_bus_message*));
-                        if (!q)
-                                return -ENOMEM;
-
-                        bus->rqueue = q;
-                        room = true;
-                }
-
-                r = bus_read_message(bus, &incoming);
+                r = bus_read_message(bus);
                 if (r < 0)
                         return r;
 
-                if (incoming) {
+                while (i < bus->rqueue_size) {
+                        sd_bus_message *incoming = NULL;
+
+                        incoming = bus->rqueue[i];
 
                         if (incoming->reply_serial == serial) {
                                 /* Found a match! */
 
+                                memmove(bus->rqueue + i, bus->rqueue + i + 1, sizeof(sd_bus_message*) * (bus->rqueue_size - i - 1));
+                                bus->rqueue_size--;
+
                                 if (incoming->header->type == SD_BUS_MESSAGE_METHOD_RETURN) {
 
                                         if (reply)
@@ -1663,6 +1680,9 @@ _public_ int sd_bus_call(
                                    incoming->sender &&
                                    streq(bus->unique_name, incoming->sender)) {
 
+                                memmove(bus->rqueue + i, bus->rqueue + i + 1, sizeof(sd_bus_message*) * (bus->rqueue_size - i - 1));
+                                bus->rqueue_size--;
+
                                 /* Our own message? Somebody is trying
                                  * to send its own client a message,
                                  * let's not dead-lock, let's fail
@@ -1672,15 +1692,11 @@ _public_ int sd_bus_call(
                                 return -ELOOP;
                         }
 
-                        /* There's already guaranteed to be room for
-                         * this, so need to resize things here */
-                        bus->rqueue[bus->rqueue_size ++] = incoming;
-                        room = false;
-
                         /* Try to read more, right-away */
-                        continue;
+                        i++;
                 }
-                if (r != 0)
+
+                if (r > 0)
                         continue;
 
                 if (timeout > 0) {