[openstack-dev] [neutron] neutron ipv6 radvd sends out link-local or nothing as def gw (L3 HA issue?)

Tobias Urdin tobias.urdin at binero.se
Mon Aug 20 10:06:26 UTC 2018


When I removed those ips and set accept_ra to 0 on the backup router:

ip netns exec qrouter-0775785e-a93a-4501-917b-be92ff03f36a sysctl -w 
net.ipv6.conf.qr-7fad6b1b-c9.accept_ra=0
ip netns exec qrouter-0775785e-a93a-4501-917b-be92ff03f36a sysctl -w 
net.ipv6.conf.qr-5be04815-68.accept_ra=0
ip netns exec qrouter-0775785e-a93a-4501-917b-be92ff03f36a ip a l
ip netns exec qrouter-0775785e-a93a-4501-917b-be92ff03f36a ip addr del 
1111:4444:0:1:f816:3eff:fe66:dea8/64 dev qr-7fad6b1b-c9
ip netns exec qrouter-0775785e-a93a-4501-917b-be92ff03f36a ip addr del 
1111:4444:0:1:f816:3eff:fec3:85bd/64 dev qr-5be04815-68

And enabled ipv6 forwarding on the active router:
ip netns exec qrouter-0775785e-a93a-4501-917b-be92ff03f36a sysctl -w 
net.ipv6.conf.all.forwarding=1

It started working again, I think this is an issue when disabling a 
router, change it to L3 HA and enable it again, so a bug?

Best regards
Tobias

On 08/20/2018 11:58 AM, Tobias Urdin wrote:
> Continuing forward, these patches should've fixed that 
> https://review.openstack.org/#/q/topic:bug/1667756+(status:open+OR+status:merged)
> I'm on Queens.
>
> The two inside interfaces on the backup router:
> [root at controller2 ~]# ip netns exec 
> qrouter-0775785e-a93a-4501-917b-be92ff03f36a cat 
> /proc/sys/net/ipv6/conf/qr-7fad6b1b-c9/accept_ra
> 1
> [root at controller2 ~]# ip netns exec 
> qrouter-0775785e-a93a-4501-917b-be92ff03f36a cat 
> /proc/sys/net/ipv6/conf/qr-5be04815-68/accept_ra
> 1
>
> Perhaps the accept_ra patches does not apply for enable/disable or 
> routers changing from a normal router to a L3 HA router?
> Best regards
>
> On 08/20/2018 11:50 AM, Tobias Urdin wrote:
>> Ok, so the issue here seems to be that I have a L3 HA router with 
>> SLAAC, both the active and standby router will
>> configure the SLAAC obtained address causing a conflict since both 
>> side share the same MAC address.
>>
>> Is there any workaround for this? Should SLAAC even be enabled for 
>> interfaces on the standby router?
>>
>> Best regards
>> Tobias
>>
>> On 08/20/2018 11:37 AM, Tobias Urdin wrote:
>>> Forgot [neutron] tag.
>>>
>>> On 08/20/2018 11:36 AM, Tobias Urdin wrote:
>>>> Hello,
>>>>
>>>> Note: before reading, this router was a regular router but was then 
>>>> disable, changed ha=true so it's now a L3 HA router, then it was 
>>>> enabled again.
>>>> CC openstack-dev for help or feedback if it's a possible bug.
>>>>
>>>> I've been testing around with IPv6 and overall the experience has 
>>>> been positive but I've met some weird issue that I cannot put my 
>>>> head around.
>>>> So this is a neutron L3 router with an outside interface with a 
>>>> ipv4 and ipv6 from the provider network and one inside interface 
>>>> for ipv4 and one inside interface for ipv6.
>>>>
>>>> The instances for some reason get's there default gateway as the 
>>>> ipv6 link-local (in fe80::/10) from the router with SLAAC and radvd.
>>>>
>>>> (1111.2222 is provider network, 1111.4444 is inside network, they 
>>>> are masked so don't pay attention to the number per se)
>>>>
>>>> *interfaces inside router:*
>>>> 15: ha-9bde1bb1-bd: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 
>>>> qdisc noqueue state UNKNOWN group default qlen 1000
>>>>     link/ether fa:16:3e:05:80:32 brd ff:ff:ff:ff:ff:ff
>>>>     inet 169.254.192.7/18 brd 169.254.255.255 scope global 
>>>> ha-9bde1bb1-bd
>>>>        valid_lft forever preferred_lft forever
>>>>     inet 169.254.0.1/24 scope global ha-9bde1bb1-bd
>>>>        valid_lft forever preferred_lft forever
>>>>     inet6 fe80::f816:3eff:fe05:8032/64 scope link
>>>>        valid_lft forever preferred_lft forever
>>>> 19: qg-86e465f6-33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 
>>>> qdisc noqueue state UNKNOWN group default qlen 1000
>>>>     link/ether fa:16:3e:3b:8b:a5 brd ff:ff:ff:ff:ff:ff
>>>>     inet 1.2.3.4/22 scope global qg-86e465f6-33
>>>>        valid_lft forever preferred_lft forever
>>>>     inet6 1111:2222::f/64 scope global nodad
>>>>        valid_lft forever preferred_lft forever
>>>>     inet6 fe80::f816:3eff:fe3b:8ba5/64 scope link nodad
>>>>        valid_lft forever preferred_lft forever
>>>> 1168: qr-5be04815-68: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 
>>>> qdisc noqueue state UNKNOWN group default qlen 1000
>>>>     link/ether fa:16:3e:c3:85:bd brd ff:ff:ff:ff:ff:ff
>>>>     inet 192.168.99.1/24 scope global qr-5be04815-68
>>>>        valid_lft forever preferred_lft forever
>>>>     inet6 fe80::f816:3eff:fec3:85bd/64 scope link
>>>>        valid_lft forever preferred_lft forever
>>>> 1169: qr-7fad6b1b-c9: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1450 
>>>> qdisc noqueue state UNKNOWN group default qlen 1000
>>>>     link/ether fa:16:3e:66:de:a8 brd ff:ff:ff:ff:ff:ff
>>>>     inet6 1111:4444:0:1::1/64 scope global nodad
>>>>        valid_lft forever preferred_lft forever
>>>>     inet6 fe80::f816:3eff:fe66:dea8/64 scope link
>>>>        valid_lft forever preferred_lft forever
>>>>
>>>> I get this error messages in dmesg on the network node:
>>>> [581085.858869] IPv6: qr-5be04815-68: IPv6 duplicate address 
>>>> 1111:4444:0:1:f816:3eff:fec3:85bd detected!
>>>> [581085.997497] IPv6: qr-7fad6b1b-c9: IPv6 duplicate address 
>>>> 1111:4444:0:1:f816:3eff:fe66:dea8 detected!
>>>> [581142.869939] IPv6: qr-5be04815-68: IPv6 duplicate address 
>>>> 1111:4444:0:1:f816:3eff:fec3:85bd detected!
>>>> [581143.182371] IPv6: qr-7fad6b1b-c9: IPv6 duplicate address 
>>>> 1111:4444:0:1:f816:3eff:fe66:dea8 detected!
>>>>
>>>> *radvd:*
>>>> interface qr-7fad6b1b-c9
>>>> {
>>>>    AdvSendAdvert on;
>>>>    MinRtrAdvInterval 30;
>>>>    MaxRtrAdvInterval 100;
>>>>
>>>>    AdvLinkMTU 1450;
>>>>
>>>>    RDNSS  2001:4860:4860::8888  {};
>>>>
>>>>    prefix 1111:4444:0:1::/64
>>>>    {
>>>>         AdvOnLink on;
>>>>         AdvAutonomous on;
>>>>    };
>>>> };
>>>>
>>>> *inside instance:*
>>>> ipv4 = 192.168.199.7
>>>> ipv6 = 1111:4444:0:1:f816:3eff:fe29:723d/64 (from radvd SLAAC)
>>>>
>>>> I can ping ipv4 gateway 192.168.199.1 and internet over ipv4.
>>>> I can ping ipv6 gateway 1111:4444:0:1::1 but I can't ping the internet
>>>>
>>>> checking the ipv6 routing table on my instance I either get no 
>>>> default gateway at all or I get a default gateway to a fe80::/10 
>>>> link-local address.
>>>> IIRC this worked before I changed the router to a L3 HA router.
>>>>
>>>> Appreciate any feedback!
>>>>
>>>> Best regards
>>>> Tobias
>>>
>>
>

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