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

[Andrey V. Elsukov]

On 22.06.2018 21:08, Viktor Dukhovni wrote:
>> Your change looks reasonable due to IPv6 DAD procedure does check for
>> presence of IFF_DRV_RUNNING flag. But actually it seems the right
>> solution should be disabling DAD for if_stf(4) interface.
>> IPv6 DAD requires that given interface should be multicast capable, but
>> for if_stf(4) it is not true.
>> Will it help if you use `ifconfig stf0 inet6 no_dad` before assigning
>> IPv6 address?
> 
> stf_up() in /etc/rc.d/stf has:
> 
>                 ifconfig stf0 create >/dev/null 2>&1
>                 ifconfig stf0 inet6 2002:${ipv4_in_hexformat}:${stf_interface_ipv6_slaid:-0}:${stf_interface_ipv6_ifid} \
>                         prefixlen ${stf_prefixlen}
> 
> Are you suggesting to add the:
> 
> 	ifconfig stf0 inet6 no_data

Yes, but "no_dad", not "no_data".

> right under "ifconfig stf0 create"?  I'd have to find a convenient time to
> reboot to the stock kernel, so this will take O(12 hours) before I can re-test.
> 
> Perhaps the fix should be belt-and-suspenders?  Both set IFF_DRV_RUNNING
> and disable DAD automatically for lack of multicast support?  Setting
> the flag bit might avoid other future issues.  Avoiding needless DAD
> polling sounds sensible.

We have already one tweak for if_stf(4) in in6_ifattach(), that disables
automatic LLA creation. I think we can also add disabling DAD there.
Something like:

Index: in6_ifattach.c
===================================================================
--- in6_ifattach.c      (revision 335361)
+++ in6_ifattach.c      (working copy)
@@ -683,6 +683,7 @@ in6_ifattach(struct ifnet *ifp, struct ifnet *alti
                 * it is rather harmful to have one.
                 */
                ND_IFINFO(ifp)->flags &= ~ND6_IFF_AUTO_LINKLOCAL;
+               ND_IFINFO(ifp)->flags |= ND6_IFF_NO_DAD;
                break;
        default:
                break;


-- 
WBR, Andrey V. Elsukov

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