Improve flexibility of receiving Router Advertisement and

automatic link-local address configuration:

- Convert a sysctl net.inet6.ip6.accept_rtadv to one for the
  default value of a per-IF flag ND6_IFF_ACCEPT_RTADV, not a
  global knob.  The default value of the sysctl is 0.

- Add a new per-IF flag ND6_IFF_AUTO_LINKLOCAL and convert a
  sysctl net.inet6.ip6.auto_linklocal to one for its default
  value.  The default value of the sysctl is 1.

- Make ND6_IFF_IFDISABLED more robust.  It can be used to disable
  IPv6 functionality of an interface now.

- Receiving RA is allowed if ip6_forwarding==0 *and*
  ND6_IFF_ACCEPT_RTADV is set on that interface.  The former
  condition will be revisited later to support a "host + router" box
  like IPv6 CPE router.  The current behavior is compatible with
  the older releases of FreeBSD.

- The ifconfig(8) now supports these ND6 flags as well as "nud",
  "prefer_source", and "disabled" in ndp(8).  The ndp(8) now
  supports "auto_linklocal".

Discussed with:	bz and jinmei
Reviewed by:	bz
MFC after:	3 days

2 files changed, 24 insertions, 9 deletions

diff --git a/usr.sbin/ndp/ndp.8 b/usr.sbin/ndp/ndp.8
index 70f51560a6a6..76f558ca2439 100644
--- a/usr.sbin/ndp/ndp.8
+++ b/usr.sbin/ndp/ndp.8
@@ -29,7 +29,7 @@
 .\"
 .\" $FreeBSD$
 .\"
-.Dd May 17, 1998
+.Dd September 2, 2009
 .Dt NDP 8
 .Os
 .\"
@@ -182,11 +182,16 @@ NUD is usually turned on by default.
 Specify whether or not to accept Router Advertisement messages
 received on the
 .Ar interface .
-Note that the kernel does not accept Router Advertisement messages
-unless the
-.Li net.inet6.ip6.accept_rtadv
-variable is non-0, even if the flag is on.
-This flag is set to 1 by default.
+This flag is set by
+.Va net.inet6.ip6.accept_rtadv
+sysctl variable.
+.It Ic auto_linklocal
+Specify whether or not to perform automatic link-local address configuration
+on
+.Ar interface .
+This flag is set by
+.Va net.inet6.ip6.auto_linklocal
+sysctl variable.
 .It Ic prefer_source
 Prefer addresses on the
 .Ar interface
@@ -204,9 +209,8 @@ In the sending case, an error of ENETDOWN will be returned to the
 application.
 This flag is typically set automatically in the kernel as a result of
 a certain failure of Duplicate Address Detection.
-While the flag can be set or cleared by hand with the
-.Nm
-command, it is not generally advisable to modify this flag manually.
+If the auto_linklocal per-interface flag is set, automatic link-local
+address configuration is performed again when this flag is cleared.
 .It Ic basereachable Ns Li = Ns Pq Ar number
 Specify the BaseReachbleTimer on the interface in millisecond.
 .It Ic retrans Ns Li = Ns Pq Ar number
@@ -253,6 +257,10 @@ Most useful when used with
 The
 .Nm
 utility first appeared in the WIDE Hydrangea IPv6 protocol stack kit.
+The
+.Fl I Ar auto_linklocal
+flag first appeared in
+.Fx 8.0 .
 .\"
 .\" .Sh BUGS
 .\" (to be written)
diff --git a/usr.sbin/ndp/ndp.c b/usr.sbin/ndp/ndp.c
index 17e439ce5844..b701ead622f8 100644
--- a/usr.sbin/ndp/ndp.c
+++ b/usr.sbin/ndp/ndp.c
@@ -1004,6 +1004,9 @@ ifinfo(ifname, argc, argv)
 #ifdef ND6_IFF_ACCEPT_RTADV
 		SETFLAG("accept_rtadv", ND6_IFF_ACCEPT_RTADV);
 #endif
+#ifdef ND6_IFF_AUTO_LINKLOCAL
+		SETFLAG("auto_linklocal", ND6_IFF_AUTO_LINKLOCAL);
+#endif
 #ifdef ND6_IFF_PREFER_SOURCE
 		SETFLAG("prefer_source", ND6_IFF_PREFER_SOURCE);
 #endif
@@ -1076,6 +1079,10 @@ ifinfo(ifname, argc, argv)
 		if ((ND.flags & ND6_IFF_ACCEPT_RTADV))
 			printf("accept_rtadv ");
 #endif
+#ifdef ND6_IFF_AUTO_LINKLOCAL
+		if ((ND.flags & ND6_IFF_AUTO_LINKLOCAL))
+			printf("auto_linklocal ");
+#endif
 #ifdef ND6_IFF_PREFER_SOURCE
 		if ((ND.flags & ND6_IFF_PREFER_SOURCE))
 			printf("prefer_source ");