[lxc-users] IPv4 and dynamic IPv6 (SLAAC) using a bridge

[Dr. Todor Dimitrov]

Hallo,

we have a consumer device, which runs an LXC container with IPv4 NAT bridging. We would like to enable IPv6 inside the container, such that it performs auto configuration using SLAAC and becomes part of the same IPv6 subnet as the host.

The Host has the following interfaces:
eth0 - main ethernet interface
br0 - a manually created bridge interface, which does not have any ports assigned

Is there a way to somehow forward all ICMPv6 packets (e.g. the Router Advertisements) to the br0 interface, such that auto configuration can take place? We have written an icmp-repeater, which basically transmits any received ICMPv6 packets on eth0 to br0. Using tcpdump we can validate that the packets arrive on the bridge interface, but the auto configuration still doesn’t take place. The following IPv6 settings apply to all interfaces:

/proc/sys/net/ipv6/conf/all/forwarding=1
/proc/sys/net/ipv6/conf/all/accept_ra=2

The main interface of the device successfully performs SLAAC and configures a valid IPv6 address using the prefix broadcasted by the radvd daemon on our router.

Is a dynamic IPv6 configuration without statically assigned IPs possible? I know that a simpler solution to the problem would be to use 2 bridges in the host (a NAT bridge for IPv4 and a host bridge for IPv6) and 2 interfaces inside the container, but we would like to avoid having to bridge the main interface.

Any thoughts and comments are appreciated.

Thanks in advance,
Todor
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