[PATCH]: The 6to4 stf0 interface flapping in/out of tentative in FreeBSD 11

[Viktor Dukhovni]

Some time ago I wrote:

> On Mar 4, 2017, at 9:05 PM, Viktor Dukhovni <freebsd at dukhovni.org> wrote:
> 
> In trying to set up a 6to4 node under 11.0-RELEASE-p8, and the stf0
> interface is constantly flipping in and out of "tentative" state, at
> seemingly 1 second intervals.  Is that to be expected?  Am I missing
> some non-obvious configuration setting?

Today, I looked closely at the kernel sources and found the issue.
Patch below.  Interfaces found to not have IFF_DRV_RUNNING in
if_drv_flags by the periodic interface scan are marked tentative.
Since the "stf" driver did not set that flag, the "stf" interface
flaps.

Index: sys/net/if_stf.c
===================================================================
--- sys/net/if_stf.c	(revision 325169)
+++ sys/net/if_stf.c	(working copy)
@@ -722,6 +722,7 @@
 		}
 
 		ifp->if_flags |= IFF_UP;
+		ifp->if_drv_flags |= IFF_DRV_RUNNING;
 		break;
 
 	case SIOCADDMULTI:

While I was at it, I also changed the below because for "stf"
the only effect of "break" was the misleading logging:

    stf0 is not multicast caple, IPv6 not enabled

Perhaps there is some configuration I am not taking into account
in which something more useful happens...  Feeback appreciated.

Index: sys/netinet6/in6_ifattach.c
===================================================================
--- sys/netinet6/in6_ifattach.c	(revision 325169)
+++ sys/netinet6/in6_ifattach.c	(working copy)
@@ -696,25 +696,25 @@
 	/*
 	 * quirks based on interface type
 	 */
 	switch (ifp->if_type) {
 	case IFT_STF:
 		/*
 		 * 6to4 interface is a very special kind of beast.
 		 * no multicast, no linklocal.  RFC2529 specifies how to make
 		 * linklocals for 6to4 interface, but there's no use and
 		 * it is rather harmful to have one.
 		 */
 		ND_IFINFO(ifp)->flags &= ~ND6_IFF_AUTO_LINKLOCAL;
-		break;
+		return;
 	default:
 		break;
 	}
 
 	/*
 	 * usually, we require multicast capability to the interface
 	 */
 	if ((ifp->if_flags & IFF_MULTICAST) == 0) {
 		nd6log((LOG_INFO, "in6_ifattach: "
 		    "%s is not multicast capable, IPv6 not enabled\n",
 		    if_name(ifp)));
 		return;

-- 
	Viktor.