So, after more digging, it appears DHCPv6 traffic coming from the test VM's
is being dropped at the Security Group (Linux Bridge) enforcement point ...
I can restart a VM's while doing a tcpdump on the respective tap interface
for that VM and see DHCPv6 request packets being sent out as expected, but
they never make it through the IPTables rules associated with the Linux
Bridge that represents the Security Group assigned to the VM. Hopefully
that makes sense.

The DHCPv6 packets seem to be getting dropped by the last IPTables Drop
rule:

Chain neutron-openvswi-sd36b2151-0 (1 references)
 pkts bytes target     prot opt in     out     source
destination
    0     0 RETURN     all      *      *       2604:ba00:ffff:fff2::b
::/0                 MAC FA:16:3E:05:C1:A3 /* Allow traffic from defined
IP/MAC pairs. */
    0     0 RETURN     all      *      *       fe80::f816:3eff:fe05:c1a3
::/0                 MAC FA:16:3E:05:C1:A3 /* Allow traffic from defined
IP/MAC pairs. */
* 6475  895K DROP       all      *      *       ::/0
::/0                 /* Drop traffic without an IP/MAC allow rule. */*

We've tried creating new Security Groups that explicitly allow ports, but
still no luck:

Ingress        IPv6     UDP     1 - 65535
Egress         IPv6     UDP     1 - 65535

Any ideas?

Thanks!

Steve



On Tue, Sep 26, 2017 at 5:58 PM, Sterdnot Shaken <sterdnotsha...@gmail.com>
wrote:

> Openstack version: Ocata
> Mech driver: OVS
> Security: Linuxbridge
>
> Hello!
>
> Anyone have any idea why DHCP for IPv4 works fine but DHCP for IPv6
> doesn't? With Stateless or just SLAAC, the VM's calculate a correct IPv6
> address from the IPv6 prefix I've assigned, but (for stateless) the
> instances doesn't get any of the options, like DNS, etc...  Stateful
> doesn't work at all. I configure a stateful network using a command like
> this:
>
> openstack subnet create --allocation-pool start=2604:ffff:ffff:ffff::2,
> end=2604:ffff:ffff:ffff:ffff:ffff:ffff:ffff --ip-version 6
> --ipv6-address-mode dhcpv6-stateful --ipv6-ra-mode dhcpv6-stateful
> --dns-nameserver 2620:0:ccc::2 --network cust01-v6_net0 --subnet-range
> 2604:ffff:ffff:ffff::/64 cust01-v6_sub0
>
> But none of the instances added to that network acquire a v6 address ever.
> I can statically assign the selected IPv6 address to the respective
> instance and it can then ping out using v6 just fine. I can also add IPv6
> DNS addresses to resolv.conf and the instance can correctly resolve as
> well. This issue happens on both Linux and Windows instances...
>
> Any ideas?
>
> Thanks in advance!
>
> Steve
>
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