Unable to properly disable IPv6 on ubuntu core 16

snapd
1

Hello All,

I would like to turn off IPv6 on my ubuntu core 16 system in a permanent way. I tried to do that via snapd by isssuing the command snap set system network.disable-ipv6=true but, after a reboot, net.ipv6.conf.eth0.disable_ipv6 is back to 0. So the system is then in the following situation

net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
net.ipv6.conf.eth0.disable_ipv6 = 0
net.ipv6.conf.lo.disable_ipv6 = 1

Why is the setting for eth0 back to 0?

Of course, to make it persistent, I can write into /etc/sysctl.d/10-snapd-network.conf but I would like to interact with the system via snapd only.

Any solution?

Thanks

2

Does the interface actually have an IPv6 address?

3

Yes it does.

2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 02:01:02:03:0b:ff brd ff:ff:ff:ff:ff:ff
    inet 192.168.5.54/24 brd 192.168.5.255 scope global dynamic eth0
       valid_lft 5182833sec preferred_lft 5182833sec
    inet6 fe80::1:2ff:fe03:bff/64 scope link
       valid_lft forever preferred_lft forever

In this case it just shows the auto assigned one since I moved the device into another network, but in case a DHCP6 server is present, it takes a global one too.

4

So in theory this option should disable IPv6, but afaiu it is possible that the interface comes up earlier than sysctls get applied in which case you could end up with ipv6 on said interface. Does lo have link local IPv6 address too?

5

My bad, I should have posted the full picture. No, loopback does not have a inet6 address:

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
    inet 127.0.0.1/8 scope host lo
       valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast state UP group default qlen 1000
    link/ether 02:01:02:03:0b:ff brd ff:ff:ff:ff:ff:ff
    inet 192.168.5.54/24 brd 192.168.5.255 scope global dynamic eth0
       valid_lft 5166918sec preferred_lft 5166918sec
    inet6 fe80::1:2ff:fe03:bff/64 scope link
       valid_lft forever preferred_lft forever