Merge "Reduce advertised ipv6 mtu by 16 to fit ethernet header" am: b1ad41b6

        if (v6only != null) {

            params = new RaParams();

            params.mtu = v6only.getMtu();

            // We advertise an mtu lower by 16, which is the closest multiple of 8 >= 14,

            // the ethernet header size.  This makes kernel ebpf tethering offload happy.

            // This hack should be reverted once we have the kernel fixed up.

            // Note: this will automatically clamp to at least 1280 (ipv6 minimum mtu)

            // see RouterAdvertisementDaemon.java putMtu()

            params.mtu = v6only.getMtu() - 16;

            params.hasDefaultRoute = v6only.hasIpv6DefaultRoute();

            if (params.hasDefaultRoute) params.hopLimit = getHopLimit(v6only.getInterfaceName());