On Fri, Jun 24, 2016 at 12:35:18PM +0200, Daniel Danzberger wrote:
> The bridge is falsly dropping ipv6 mulitcast packets if there is:
> 1. No ipv6 address assigned on the brigde.
> 2. No external mld querier present.
> 3. The internal querier enabled.
>
> When the bridge fails to build mld queries, because it has no
> ipv6 address, it slilently returns, but keeps the local querier enabled.
> This specific case causes confusing packet loss.
>
> Ipv6 multicast snooping can only work if:
> a) An external querier is present
> OR
> b) The bridge has an ipv6 address an is capable of sending own queries
>
> Otherwise it has to forward/flood the ipv6 multicast traffic,
> because snooping cannot work.
>
> This patch fixes the issue by adding a flag to the bridge struct that
> indicates that there is currently no ipv6 address assinged to the bridge
> and returns a false state for the local querier in
> __br_multicast_querier_exists().
Fixes: 1d81d4c3dd88 ("bridge: check return value of ipv6_dev_get_saddr()")
