an item may be queued and processed later. While this is OK for mbufs,
this is a problem for control messages.
In the framework:
- Add optional callback function pointer to an item. When item gets
applied the callback is executed from ng_apply_item().
- Add new flag NG_PROGRESS. If this flag is supplied, then return
EINPROGRESS instead of 0 in case if item failed to deliver
synchronously and was queued.
- Honor NG_PROGRESS in ng_snd_item().
In ng_socket:
- When userland sends control message add callback to the item.
- If ng_snd_item() returns EINPROGRESS, then sleep.
This change fixes possible races in ngctl(8) scripts.
Reviewed by: julian
Approved by: re (scottl)
8afe16d57b