[Lucid] Networking + IPv6 (long)

[NoOp]

I've been following a few newsgroups/lists where folks are having
networking issues after upgrading from 9.10 to 10.04. A rather
interesting problem was on alt.os.linux.ubuntu:

> The networking stopped working.
> 
> So I partitioned to give me a 9.10/10.04 dual boot. Again 9,10
> works 10.04 doesn't. Its the same network ports, cable, router
> port, etc.
> 
> The router is set to give DHCP. Both distros are set with
> "Auto eth0", identical static IPs, gateway, DNS's and MAC
> addresses for the card. Both distros use the same bios
> settings for the  Realtek RTL8111/8168B rev03 express gigabyte
> controller. 
> If I switch to DCHP on both again the 9.10 works, 10.04
> doesnt.
> 
> ethtool -i eth0 gives the driver as r8169 2.3LK-NAPI firmware
> version bus 0000:02:00.0 on both systems. 
> 
> In case the kernel had been modified recently Ive just
> downloaded 10.04 server and tried that but it cant connect to
> find network time, a fresh download and install of 10.04 32bit
> desktop gives the same problem - no wired networking.  
> 
> Ive replaced network manager on 10.04 with wicd and still the
> same problem.
> 
> Any pointers anyone??

The solution (in this case) was:

> In article <hvdcvu$lda$7 at news.eternal-september.org>,
>    Hadron<hadronquark at gmail.com> wrote:
>> > "Mikey" <mminorhsd at earthlink.net> writes:
>>> > >
>>> > > I had a similar problem. It started working when I set
>>> > > IPv6 to ignore. Hope that helps....
>> > Yup. That was stopping my Debian setup download the Eclipse
>> > toolkits for Android development. Quite astonishing.
>> > Search for ipv6 here:
>> > http://workaround.org/node/326
> Success!!!
> Many many thanks Hadron.
> I went to etc/sysctl.d and changed 10-network-security.conf by
> adding the line
> net.ipv6.bindv6only=0
> 
> rebooted and up came the network.
> Ive been working on this for a couple of weeks and thank you
> all for your positive suggestions.
> 

So I got poking around google & launchpad and found these:

<https://bugs.launchpad.net/ubuntu/+source/eclipse/+bug/541482>
[eclipse unable to 'install new software']
This comment in that bug report is of interest:
<https://bugs.launchpad.net/ubuntu/+source/eclipse/+bug/541482/comments/29>

and this report:
<https://bugs.launchpad.net/ubuntu/+source/sun-java6/+bug/486215>
<https://bugs.launchpad.net/ubuntu/+source/sun-java6/+bug/486215/comments/2>
Upstream:
http://bugs.debian.org/cgi-bin/bugreport.cgi?bug=560056

Note that the OP in the first had networking working just find in 9.10,
but not on 10.04. Same hardware, same machine, boot to 9.10 and all
works, boot to 10.04 and no network. I'm wondering if perhaps others
that have reported similar networking problems on the list may have been
subject to the IPv6 issue.

For those that have, can you please provide the output of:
$ /sbin/sysctl net.ipv6.bindv6only
and see if the response is:
$ /sbin/sysctl net.ipv6.bindv6only
net.ipv6.bindv6only = 0
or
$ /sbin/sysctl net.ipv6.bindv6only
net.ipv6.bindv6only = 1

Thanks