Comment # 9 on bug 1145529 from Michal Filka

(In reply to Richard Bos from comment #6)
> When I execute your "sysctl -a | grep disable_ipv6" command:
> 
> My output is:
> # sysctl -a | grep disable_ipv6
> net.ipv6.conf.all.disable_ipv6 = 1
> net.ipv6.conf.default.disable_ipv6 = 1
> net.ipv6.conf.eth0.disable_ipv6 = 0  <<<<<<

this should be a problem. It overwrites global setup (.all.disable_ipv6) by per
interface setup (eth0 in this case). Question is where it comes from because
yast do not touch this per interface variables.

Could you try a "hotfix": 
/usr/sbin/sysctl -w net.ipv6.conf.eth0.disable_ipv6=1

and check whether it survives reboot to see if it is configured by some other
part of your system?

> net.ipv6.conf.lo.disable_ipv6 = 1
> 
> 
> I checked my settings again and "enable ipv6" is unchecked.
> (and IPv6 is thus present)
> 
> In the log        I find:
> 
> 2019-08-14 06:23:35 <3> <system> (6198) [ag_udev_persistent] OPEN_FAILED
> opening /etc/udev/rules.d/79-yast2-drivers.rules failed: No such file or
> directory
> 
> 2019-08-14 06:23:35 <1> <system>(6159) [Ruby] modules/LanItems.rb:1134
> Ops.get called on nil.
> 2019-08-14 06:23:35 <1> <system>(6159) [Ruby] modules/LanItems.rb:1133 Index
> 1 is out of array size
> 2019-08-14 06:23:35 <1> <system>(6159) [Ruby] modules/LanItems.rb:1131 Index
> 1 is out of array size
> 
> The code does not seems to be happy...

Usually not a problem. Just info - a bit useless bcs it can be caused by valid
check like "if index is not in limit go away"

> 
> 
> It continues with:
> 2019-08-14 06:23:35 <1> <system>(6159) [Ruby] modules/Lan.rb:227 readIPv6:
> IPv6 is disabled
> 
> 2019-08-14 06:23:35 <3> <system>(6159) [Interpreter] modules/Routing.rb:273
> File not found /etc/sysconfig/network/ifroute-eth0
> 2019-08-14 06:23:35 <3> s<system>(6159) [Interpreter] modules/Routing.rb:273
> File not found /etc/sysconfig/network/ifroute-lo
> 
> (replace my hostname with <system>)
> 
> Looks like an issue....
> # ls -l /etc/sysconfig/network/ifroute-*
> 
> ls: cannot access '/etc/sysconfig/network/ifroute-*': No such file or
> directory
> # ls -l /etc/sysconfig/network/if*
> -rw------- 1 root root   195 Jul 30 12:17 /etc/sysconfig/network/ifcfg-eth0
> -rw------- 1 root root   147 Apr 11 05:42 /etc/sysconfig/network/ifcfg-lo
> -rw-r--r-- 1 root root 21738 Feb 24  2019
> /etc/sysconfig/network/ifcfg.template
> 
> 
> Is this the issue?

No. It just means that you don't use per interface route files. Again just
info.