In the splnet times, netgraph was functional and synchronous. Nowadays,

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)

1 files changed, 8 insertions, 0 deletions

diff --git a/sys/netgraph/netgraph.h b/sys/netgraph/netgraph.h
index a963fc8..4304ced 100644
--- a/sys/netgraph/netgraph.h
+++ b/sys/netgraph/netgraph.h
@@ -580,6 +580,7 @@ _ng_node_foreach_hook(node_p node, ng_fn_eachhook *fn, void *arg,
  *
  */
 typedef	void	ng_item_fn(node_p node, hook_p hook, void *arg1, int arg2);
+typedef	void	ng_apply_t(void *context, int error);
 struct ng_item {
 	u_long	el_flags;
 	item_p	el_next;
@@ -597,6 +598,12 @@ struct ng_item {
 			int		fn_arg2;
 		} fn;
 	} body;
+	/*
+	 * Optional callback called when item is being applied,
+	 * and its context.
+	 */
+	ng_apply_t	*apply;
+	void		*context;
 #ifdef	NETGRAPH_DEBUG /*----------------------------------------------*/
 	char *lastfile;
 	int  lastline;
@@ -1084,6 +1091,7 @@ int	ng_callout(struct callout *c, node_p node, hook_p hook, int ticks,
 #define	NG_NOFLAGS	0x00000000	/* no special options */
 #define	NG_QUEUE	0x00000001	/* enqueue item, don't dispatch */
 #define	NG_WAITOK	0x00000002	/* use M_WAITOK, etc. */
+#define	NG_PROGRESS	0x00000004	/* return EINPROGRESS if queued */
 
 /*
  * prototypes the user should DEFINITELY not use directly