What happens internally when a service calls RequestName?

When a process calls RequestName on org.freedesktop.DBus, the bus daemon has to resolve a small state machine around ownership, not just record a simple string-to-connection mapping.

1. The bus daemon checks whether the requested name is currently unowned. If so, the calling connection immediately becomes the primary owner, and a NameOwnerChanged signal is broadcast announcing the new owner.
2. If the name is already owned, the daemon checks the flags passed with the request. With DBUS_NAME_FLAG_DO_NOT_QUEUE set, the call simply fails, returning DBUS_REQUEST_NAME_REPLY_EXISTS. Without it, the caller is added to a queue of processes waiting for that name.
3. If the current owner set DBUS_NAME_FLAG_ALLOW_REPLACEMENT and the new requester set DBUS_NAME_FLAG_REPLACE_EXISTING, ownership can be transferred immediately instead of queued, again firing a NameOwnerChanged signal.
4. If the current owner later releases the name or disconnects, the bus daemon automatically promotes the next connection in the queue, if any, to primary owner, firing another NameOwnerChanged signal.

This queueing behavior is what allows patterns like a primary service instance with standby replacements ready to take over ownership automatically if the primary exits.