Add new netgraph control message NGM_ETHER_DETACH, which actually

removes netgraph node and unwraps Ethernet interface.

This gives us ability to unload ng_ether.ko, when all interfaces
are detached, making ng_ether(4) developers happy.

Reviewed by:	ru

sys/netgraph/ng_ether.c

@@ -186,6 +186,13 @@ static const struct ng_cmdlist ng_ether_cmdlist[] = {
 	  &ng_parse_enaddr_type,
 	  NULL
 	},
+	{
+	  NGM_ETHER_COOKIE,
+	  NGM_ETHER_DETACH,
+	  "detach",
+	  NULL,
+	  NULL
+	},
 	{ 0 }
 };
 
@@ -544,6 +551,9 @@ ng_ether_rcvmsg(node_p node, item_p item, hook_p lasthook)
 			    (struct sockaddr *)&sa_dl);
 			break;
 		    }
+		case NGM_ETHER_DETACH:
+			ng_ether_detach(priv->ifp);
+			break;
 		default:
 			error = EINVAL;
 			break;

sys/netgraph/ng_ether.h

@@ -67,6 +67,7 @@ enum {
 	NGM_ETHER_SET_AUTOSRC,		/* enable/disable src addr override */
 	NGM_ETHER_ADD_MULTI,		/* add multicast membership */
 	NGM_ETHER_DEL_MULTI,		/* delete multicast membership */
+	NGM_ETHER_DETACH,		/* our way to be shut down */
 };
 
 #endif /* _NETGRAPH_NG_ETHER_H_ */