No IPv6 address, dmesg: "IPv6 duplicate address"

[sanderj]

My ISP provides native IPv6. That used to work. But not anymore: dmesg says:


[51849.455380] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[52038.685221] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[52208.691846] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[52393.831468] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[52546.966404] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[52713.804952] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!

(Note: I obfuscated my public IPv6 address by inserting the 'blalba' into the log above and below)

Googling that error message, I found http://timesinker.blogspot.nl/2009/11/karmic-ipv6-global-address-problems.html with this workaround:


sander@R540:~$ sudo sysctl net.ipv6.conf.eth0.accept_dad
net.ipv6.conf.eth0.accept_dad = 1

sander@R540:~$ sudo sysctl net.ipv6.conf.eth0.accept_dad=0
net.ipv6.conf.eth0.accept_dad = 0

That seemed to work a week ago (not 100% sure), but not anymore: dmesg now says:


[58037.095963] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[58037.519619] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:cdb:467c:e1e6:7532 detected!
[58038.424991] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:58eb:c65e:25e:b3c7 detected!
[58039.141499] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:a413:1a:2614:e16a detected!
[58039.141507] IPv6: ipv6_create_tempaddr: regeneration time exceeded - disabled temporary address support

and still no public IPv6 address on my wlan0 interface.

The command rdisc6 just shows a correct response from my modem:


sander@R540:~$ rdisc6 wlan0
Soliciting ff02::2 (ff02::2) on wlan0...

Hop limit : 64 ( 0x40)
Stateful address conf. : No
Stateful other conf. : Yes
Router preference : medium
Router lifetime : 1800 (0x00000708) seconds
Reachable time : 30000 (0x00007530) milliseconds
Retransmit time : unspecified (0x00000000)
Prefix : 2a00:cd8:blabla::/64
Valid time : 86400 (0x00015180) seconds
Pref. time : 86400 (0x00015180) seconds
MTU : 1480 bytes (valid)
Source link-layer address: 50:67:F0:D7:61:FB
from fe80::5267:f0ff:fed7:61fb
sander@R540:~$

Ubuntu 12.10, fully updated.

Tips?

[sanderj]

I booted into Ubuntu 12.04.1 with Linux 3.2.0-25-generic, and the same problem is there.

So it is not a Linux version related problem.

[sanderj]

The 12.10 system now has an IPv6 address, but dmesg says:


[14790.090074] ICMPv6: NA: someone advertises our address 2a00:0cd8:blabla:1182:7070:8ebf:4fe1 on wlan0!
[14790.090228] ICMPv6: NA: someone advertises our address 2a00:0cd8:blabla:1af4:6aff:fe9c:ced4 on wlan0!


Tips welcome

[prodigy_]

You should contact your ISP. Quite possibly there's indeed another host with the same IPv6.

[sanderj]

You should contact your ISP. Quite possibly there's indeed another host with the same IPv6.

Another Ubuntu system (Ubuntu 11.10, Linux kernel 3.0.0-29-generic) is giving the same error message in dmesg. :-(

However, I tested with an Android phone and a Windows system, and they both have perfect IPv6 connectivity.

So, it is something between Ubuntu (Linux?) and the modem providing IPv6. I don't think there is a really a device with the same IPv6 address; it's Ubuntu / Linux that's thinking that ...

[sanderj]

Interesting, this seems to happen:

First I disable Wifi.
Then I enable Wifi.
I keep on 'refreshing' "ifconfig", and it shows there appears a (or two?) public IPv6 address for a second or so, and then it disappears. In my dmesg there is a line:


[24745.180130] IPv6: ipv6_create_tempaddr: regeneration time exceeded - disabled temporary address support

[lemming465]

I agree it smells like an ubuntu and/or kernel bug. If you don't care deeply about using RFC 4941 "privacy" addresses (62 random bits in the host part) instead of EUI-64 mapped addresses (46 bits of ethernet MAC in the host part), do you get better results with a workaround of turning off privacy addresses?

sudo sysctl -w net.ipv6.conf.eth0.use_tempaddr=0
sudo sysctl -w net.ipv6.conf.wlan0.use_tempaddr=0
sudo service networking restart

[sanderj]

I tried that, but reloading the network ('sudo service networking restart') resulted in a broken GUI. So I did this:

With a


sudo nano /etc/sysctl.conf

I put this into that file:


net.ipv6.conf.all.use_tempaddr=-1

then rebooted, and ... I have a public IPv6 address! :p

In the beginning of dmesg there is still some trouble:


[ 94.863267] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:1af4:6aff:fe9c:ced4 detected!
[ 95.486847] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:4047:1864:8b82:465 detected!
[ 95.966238] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:315f:857:760b:4d6d detected!
[ 97.149406] IPv6: wlan0: IPv6 duplicate address 2a00:cd8:blabla:e88d:4267:9fb6:e8b4 detected!
[ 97.149412] IPv6: ipv6_create_tempaddr: regeneration time exceeded - disabled temporary address support

... but that doesn't seem to matter.

Oh ... and a pity I must disable privacy extensions to IPv6 working. But I'm glas I have IPv6 again.

Thank you for your help!

[sanderj]

PS: Is this is bug in Ubuntu / Linux? Or is it in the interaction with my modem doing IPv6?

[sanderj]

Update:


net.ipv6.conf.all.use_tempaddr=0

also works, although it takes about 5 minutes before a public IPv6 address appears on my wlan0

[sanderj]

Update:

I created a bug report: https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1120617