replace the hooks used with if_detachhooks with a task list.

the main semantic change is that things registering detach hooks
have to allocate and set a task structure that then gets added to
the list. this means if the task is allocated up front (eg, as part
of carps softc or bridges port structure), it avoids the possibility
that adding a hook can fail. a lot of drivers weren't checking for
failure, and unwinding state in the event of failure in other parts
was error prone.

while doing this i discovered that the list operations have to be
in a particular order, but drivers weren't doing that consistently
either. this diff wraps the list ops up so you have to seriously
go out of your way to screw them up.

ive also sprinkled some NET_ASSERT_LOCKED around the list operations
so we can make sure there's no potential for the list to be corrupted,
especially while it's being run.

hrvoje popovski has tested this a bit, and some issues he discovered
have been fixed.

ok sashan@

1 files changed, 2 insertions, 2 deletions

diff --git a/sys/net/if_trunk.h b/sys/net/if_trunk.h
index 21c575f4933..28f93d7a196 100644
--- a/sys/net/if_trunk.h
+++ b/sys/net/if_trunk.h
@@ -1,4 +1,4 @@
-/*	$OpenBSD: if_trunk.h,v 1.27 2019/04/29 04:26:47 dlg Exp $	*/
+/*	$OpenBSD: if_trunk.h,v 1.28 2019/11/06 03:51:26 dlg Exp $	*/
 
 /*
  * Copyright (c) 2005, 2006, 2007 Reyk Floeter <reyk@openbsd.org>
@@ -166,7 +166,7 @@ struct trunk_port {
 	u_int32_t			tp_prio;	/* port priority */
 	u_int32_t			tp_flags;	/* port flags */
 	void				*lh_cookie;	/* if state hook */
-	void				*dh_cookie;	/* if detach hook */
+	struct task			tp_dtask;	/* if detach hook */
 
 	/* Redirected callbacks */
 	int	(*tp_ioctl)(struct ifnet *, u_long, caddr_t);