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tinyau
PostPosted: Wed Jan 28, 2015 3:29 am 
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Joined: Wed Jan 28, 2015 12:05 am
Posts: 6
I'm using Gentoo and failed to ping IPv6 address by the following command

ping6 ipv6.google.com -c 3

The result is 100% packet loss.

I have contacted Linode support and checked several areas. Linode support said it's quite tough to diagnose the problem and suggested me to seek support in the forum.

I have checked IPv6 privacy extension is disabled.
- content of /proc/sys/net/ipv6/conf/eth0/use_tempaddr is '0'.

Please refer to the output of the several related commands for reference. Thanks a lot.

ifconfig
--------
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 106.187.97.149 netmask 255.255.255.0 broadcast 106.187.97.255
inet6 2400:8900::2858:6484:e8ea:e61 prefixlen 64 scopeid 0x0<global>
inet6 fe80::f03c:91ff:fe96:2d21 prefixlen 64 scopeid 0x20<link>
ether f2:3c:91:96:2d:21 txqueuelen 1000 (Ethernet)
RX packets 275726 bytes 46460135 (44.3 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 317620 bytes 101092501 (96.4 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0

ip -6 route
------------
2400:8900::/64 dev eth0 proto kernel metric 3 mtu 1500
fe80::/64 dev eth0 proto kernel metric 256
default via fe80::1 dev eth0 metric 3 mtu 1500

ip -6 addr
-----------
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
3: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qlen 1000
inet6 2400:8900::2858:6484:e8ea:e61/64 scope global dynamic
valid_lft 2591985sec preferred_lft 604785sec
inet6 fe80::f03c:91ff:fe96:2d21/64 scope link
valid_lft forever preferred_lft forever

ip -6 neigh
------------
fe80::8678:acff:fe5a:15c1 dev eth0 lladdr 84:78:ac:5a:15:c1 router STALE
fe80::1 dev eth0 lladdr 00:05:73:a0:0f:ff router STALE
fe80::8678:acff:fe0d:95c1 dev eth0 lladdr 84:78:ac:0d:95:c1 router STALE

sysctl -a | egrep 6.*eth0.*forwarding
-----------------------------------------
net.ipv6.conf.eth0.forwarding = 1

sysctl -a | grep conf.eth0.accept_ra
---------------------------------------
net.ipv6.conf.eth0.accept_ra = 1
net.ipv6.conf.eth0.accept_ra_defrtr = 1
net.ipv6.conf.eth0.accept_ra_from_local = 0
net.ipv6.conf.eth0.accept_ra_pinfo = 1
net.ipv6.conf.eth0.accept_ra_rtr_pref = 1
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retrograde inversion
PostPosted: Wed Jan 28, 2015 3:47 am 
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Posts: 51
Can you show the output of "ip6tables-save"?
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XReaper
PostPosted: Wed Jan 28, 2015 3:55 am 
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Posts: 56
Website: http://for-no-reason.net
Location: Australia
I wonder if `ping6 fe80::1 -I 2400:8900::2858:6484:e8ea:e61` would work.
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tinyau
PostPosted: Wed Jan 28, 2015 3:57 am 
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Joined: Wed Jan 28, 2015 12:05 am
Posts: 6
retrograde inversion wrote:
Can you show the output of "ip6tables-save"?


Code:
# Generated by ip6tables-save v1.4.21 on Wed Jan 28 15:56:40 2015
*nat
:PREROUTING ACCEPT [0:0]
:INPUT ACCEPT [0:0]
:OUTPUT ACCEPT [151:13512]
:POSTROUTING ACCEPT [151:13512]
COMMIT
# Completed on Wed Jan 28 15:56:40 2015
# Generated by ip6tables-save v1.4.21 on Wed Jan 28 15:56:40 2015
*security
:INPUT ACCEPT [2953:296040]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [582:46372]
COMMIT
# Completed on Wed Jan 28 15:56:40 2015
# Generated by ip6tables-save v1.4.21 on Wed Jan 28 15:56:40 2015
*raw
:PREROUTING ACCEPT [2933:294184]
:OUTPUT ACCEPT [506:38976]
COMMIT
# Completed on Wed Jan 28 15:56:40 2015
# Generated by ip6tables-save v1.4.21 on Wed Jan 28 15:56:40 2015
*mangle
:PREROUTING ACCEPT [2933:294184]
:INPUT ACCEPT [2933:294184]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [506:38976]
:POSTROUTING ACCEPT [506:38976]
COMMIT
# Completed on Wed Jan 28 15:56:40 2015
# Generated by ip6tables-save v1.4.21 on Wed Jan 28 15:56:40 2015
*filter
:INPUT ACCEPT [2933:294184]
:FORWARD ACCEPT [0:0]
:OUTPUT ACCEPT [506:38976]
COMMIT
# Completed on Wed Jan 28 15:56:40 2015
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dwfreed
PostPosted: Wed Jan 28, 2015 4:30 am 
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Joined: Mon Aug 29, 2011 2:34 am
Posts: 77
Are you using dhcpcd?

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tinyau
PostPosted: Wed Jan 28, 2015 5:18 am 
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Posts: 6
XReaper wrote:
I wonder if `ping6 fe80::1 -I 2400:8900::2858:6484:e8ea:e61` would work.


Same result - 100% packet loss.
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tinyau
PostPosted: Wed Jan 28, 2015 5:19 am 
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Posts: 6
dwfreed wrote:
Are you using dhcpcd?


Yes, and already used 'ipv6' USE flag in make.conf to make all software IPv6 compatible.
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tinyau
PostPosted: Wed Jan 28, 2015 5:25 am 
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Joined: Wed Jan 28, 2015 12:05 am
Posts: 6
Linode support has mentioned that it my Linode has the following IPv6 addresses set:

2400:8900::2858:6484:e8ea:e61/64 (Global)
fe80::f03c:91ff:fe96:2d21/64 (Link Local)

But it should be the followings for IPv6 privacy extensions is disabled.

2400:8900::f03c:91ff:fe96:2d21/128 (Global)
fe80::f03c:91ff:fe96:2d21/128 (Link Local)

He suspected IPv6 privacy extensions is enabled that caused SLAAC to have issues and give you Linode the wrong IPv6 address. However, IPv6 privacy extensions is actually DISABLED in my Gentoo Linode.
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dwfreed
PostPosted: Wed Jan 28, 2015 12:41 pm 
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dhcpcd defaults to doing a new method for privacy extensions, which generates stable addresses based on a secret key stored on the machine combined with the prefix from the router advertisement. However, this still doesn't work on Linode, because you must use the EUI-64-based SLAAC address. To disable this behavior in dhcpcd, remove 'slaac private' from your /etc/dhcpcd.conf.

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tinyau
PostPosted: Thu Jan 29, 2015 3:06 am 
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Joined: Wed Jan 28, 2015 12:05 am
Posts: 6
dwfreed wrote:
dhcpcd defaults to doing a new method for privacy extensions, which generates stable addresses based on a secret key stored on the machine combined with the prefix from the router advertisement. However, this still doesn't work on Linode, because you must use the EUI-64-based SLAAC address. To disable this behavior in dhcpcd, remove 'slaac private' from your /etc/dhcpcd.conf.


The problem is solved, thank you so much. :D
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