sd-bus: add sd_bus_message.verify_destination_id and .destination_ptr

kdbus learned to accept both a numerical destination ID as well as a
well-known-name. In that case, kdbus makes sure that the numerical ID is in
fact the owner of the provided name and fails otherwise.

This allows for race-free assertion of a bus name owner while sending a
message, which is a requirement for bus-proxyd.

Add two new fields to sd_bus_message, and set the numerical ID to
verify_destination_id if bus_message_setup_kmsg() is called for a
message with a well-known name.

Also, set the destination's name in the kdbus item to .destination_ptr
if it is non-NULL.

Normal users should not touch these fields, and they're not publicy
accessible.

1 files changed, 5 insertions, 0 deletions

diff --git a/src/libsystemd/sd-bus/bus-message.c b/src/libsystemd/sd-bus/bus-message.c
index be36d9f417..1a8c445f0b 100644
--- a/src/libsystemd/sd-bus/bus-message.c
+++ b/src/libsystemd/sd-bus/bus-message.c
@@ -148,6 +148,11 @@ static void message_free(sd_bus_message *m) {
         if (m->iovec != m->iovec_fixed)
                 free(m->iovec);
 
+        if (m->destination_ptr) {
+                free(m->destination_ptr);
+                m->destination_ptr = NULL;
+        }
+
         message_reset_containers(m);
         free(m->root_container.signature);
         free(m->root_container.offsets);