[CentOS] IPv6 broken on Linode

Thu Feb 16 10:42:47 UTC 2017

On 02/16/2017 02:32 AM, James Hogarth wrote:
> On 16 February 2017 at 10:17, Alice Wonder <alice at domblogger.net> wrote:
>> On 02/16/2017 02:03 AM, James Hogarth wrote:
>>>
>>> On 16 February 2017 at 09:09, Alice Wonder <alice at domblogger.net> wrote:
>>>>
>>>> On 02/16/2017 12:54 AM, Tony Mountifield wrote:
>>>>>
>>>>>
>>>>> In article <4cbb9dc4-f063-3434-b7a1-d4d0e6581b5e at domblogger.net>,
>>>>> Alice Wonder <alice at domblogger.net> wrote:
>>>>>>
>>>>>>
>>>>>> https://forum.linode.com/viewtopic.php?f=19&t=14570&p=72785
>>>>>>
>>>>>> I can not figure out what I need to do.
>>>>>>
>>>>>> Apparently according to linode support, the VM is trying to grab an
>>>>>> IPv6
>>>>>> address with some privacy stuff enabled by default causing it to not
>>>>>> grab the IPv6 address that is assigned to me.
>>>>>
>>>>>
>>>>>
>>>>> Does the accepted answer at the following link give you any useful
>>>>> hints?
>>>>>
>>>>>
>>>>>
>>>>> http://superuser.com/questions/243669/how-to-avoid-exposing-my-mac-address-when-using-ipv6
>>>>>
>>>>> Cheers
>>>>> Tony
>>>>>
>>>>
>>>> Not really - I tried
>>>>
>>>> net.ipv6.conf.all.use_tempaddr = 0
>>>>
>>>> and it still fails to grab the proper IPv6
>>>>
>>>> -=-
>>>>
>>>> Just in case, I did ask Linode support to verify that my hardware address
>>>> is
>>>> what it is suppose to be. Still waiting to hear on that.
>>>>
>>>> _______________________________________________
>>>
>>>
>>>
>>> it still is key=value  ... it uses the ifcfg- files (via the rh
>>> plugin) and they are all key=value
>>>
>>> It would be helpful if you could paste the journal output (journalctl
>>> -u NetworkManager) from the time period of attempting to get an
>>> address ...
>>>
>>> also the nmcli conn sh <connection_name> information for the interface
>>> along with your ifcfg- files
>>
>>
>> ifcfg-lo is the only one that exists on any of the servers - including the
>> VMs that grab the correct IPv6 address.
>>
>> from /sbin/ifconfig -a :
>>
>
> For a start stop using ifconfig ... it's broken at this point on
> linux, especially on multi ip and ipv6 scenarios
>
> Use `ip -6 addr sh` for ipv6 specfic stuff, or just ip addr sh to see
> all IP address stuff regardless of family
>
>> eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
>>         inet 178.79.185.217  netmask 255.255.255.0  broadcast 178.79.185.255
>>         inet6 fe80::a8ad:d312:4ef4:7272  prefixlen 64  scopeid 0x20<link>
>>         inet6 2a01:7e00::825f:e564:ad53:72fc  prefixlen 64  scopeid
>> 0x0<global>
>>         ether f2:3c:91:18:8a:7e  txqueuelen 1000  (Ethernet)
>>         RX packets 9903  bytes 1088621 (1.0 MiB)
>>         RX errors 0  dropped 0  overruns 0  frame 0
>>         TX packets 7786  bytes 1087223 (1.0 MiB)
>>         TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
>>
>> That hardware address - the 18:8a:7e corresponds with what the IPv6 address
>> is suppose to be. But that's not the address it is grabbing, despite the
>> fact that net.ipv6.conf.all.use_tempaddr = 0 is set.
>>
>> I'm seriously wondering if the real issue is a mis-configured dhcp server in
>> their London facility because nothing makes sense.
>>
>> journalctl -u NetworkManager
>>
>> reports no journal entries found.
>>
>
> So are you not using NetworkManager then? there should be some logs ...
>
>
>> I think the problem must be on their end.
>>
>> It all was working fine until they migrated the VM because of a hardware
>> issue, and I suspect now all the hardware address privacy stuff being the
>> issue is barking up the wrong tree because all the reading I have done seems
>> to indicate that with
>>
>> net.ipv6.conf.all.use_tempaddr = 0
>>
>> that a fake temporary hardware address would not be sent to their dhcp
>> server when obtaining the address, but the real one, that should be fetching
>> my assigned address.
>
> Only if the kernel is doing SLAAC ... if other things (eg NM) are
> handling it directly they may act differently ... but then from the
> lack of logs is NM actually handling this?
>
> Does systemctl status NetworkManager show it running and does nmcli
> show anything?
>

systemctl status NetworkManager
● NetworkManager.service - Network Manager
    Loaded: loaded (/usr/lib/systemd/system/NetworkManager.service; 
enabled; vendor preset: enabled)
    Active: active (running) since Thu 2017-02-16 08:19:34 UTC; 2h 19min ago

* more stuff *

nmcli
eth0: connected to Wired connection 1
	"Red Hat Virtio network device"
	ethernet (virtio_net), F2:3C:91:18:8A:7E, hw, mtu 1500
	ip4 default, ip6 default
	inet4 178.79.185.217/24
	route4 178.79.187.246/32
	inet6 2a01:7e00::825f:e564:ad53:72fc/64
	inet6 fe80::a8ad:d312:4ef4:7272/64
	route6 2a01:7e00::/64

* more stuff for other interfaces *

-=-

The output of

sysctl -a | grep net.ipv6 :

https://librelamp.com/sysctl.txt

It looks from that like it should not be hiding the real MAC address.

>
>>
>> It's all very frustrating but I suspect now the problem isn't the CentOS
>> network configuration.
>>
>
> Sounds likely ... depending on what there RA's say and how dhcpv6 is
> being handled there (if at all) it could drastically affect things -
> particularly if MAC changed on migration.
>
>> Five other servers all configured the same (started from same CentOS 7 image
>> and network stuff left alone) work properly - so I don't know.
>>
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