Document struct nd_ifinfo protection, remove obsolete .initialized member

All access to struct ifnet's member *if_nd is read-only, with the one
write exception being nd6_slowtimo() updating ND information.

IPv6 Neighbour Discovery information is fully protected by the net lock.
---
nd6_ifattach() allocates and unconditionally initialises struct ifnet's
*if_nd member, so early in if_attachsetup() that there is no way to query
unitialised Neighour Unreachable Detection bits.

Only SIOCGIFINFO_IN6 through ndp(8) used the .initialized member:
Added/set since 2002 sys/netinet6/nd6.c r1.42
    attach nd_ifinfo structure to if_afdata.
    split IPv6 MTU (advertised by RA) from real link MTU.
    sync with kame

Read      since 2002 usr.sbin/ndp/ndp.c r1.16
    use new SIOCGIFINFO_IN6.  random other cleanups.  sync w/kame.

Obsolete  since 2017 sys/netinet6/nd6.c r1.217
                     usr.sbin/ndp/ndp.c r1.85
    Remove knob and always do neighbor unreachable detection.

Feedback OK bluhm

1 files changed, 1 insertions, 3 deletions

diff --git a/sys/netinet6/nd6.c b/sys/netinet6/nd6.c
index 18b590aa738..8cedafd1d35 100644
--- a/sys/netinet6/nd6.c
+++ b/sys/netinet6/nd6.c
@@ -1,4 +1,4 @@
-/*	$OpenBSD: nd6.c,v 1.255 2022/11/28 13:10:58 kn Exp $	*/
+/*	$OpenBSD: nd6.c,v 1.256 2022/11/28 19:13:36 kn Exp $	*/
 /*	$KAME: nd6.c,v 1.280 2002/06/08 19:52:07 itojun Exp $	*/
 
 /*
@@ -124,8 +124,6 @@ nd6_ifattach(struct ifnet *ifp)
 
 	nd = malloc(sizeof(*nd), M_IP6NDP, M_WAITOK | M_ZERO);
 
-	nd->initialized = 1;
-
 	nd->basereachable = REACHABLE_TIME;
 	nd->reachable = ND_COMPUTE_RTIME(nd->basereachable);
 	nd->retrans = RETRANS_TIMER;