• Linus Lüssing's avatar
    batman-adv: Send multicast packets to nodes with a WANT_ALL flag · 4c8755d6
    Linus Lüssing authored
    With this patch a node sends IPv4 multicast packets to nodes which
    have a BATADV_MCAST_WANT_ALL_IPV4 flag set and IPv6 multicast packets
    to nodes which have a BATADV_MCAST_WANT_ALL_IPV6 flag set, too.
    
    Why is this needed? There are scenarios involving bridges where
    multicast report snooping and multicast TT announcements are not
    sufficient, which would lead to packet loss for some nodes otherwise:
    
    MLDv1 and IGMPv1/IGMPv2 have a suppression mechanism
    for multicast listener reports. When we have an MLDv1/IGMPv1/IGMPv2
    querier behind a bridge then our snooping bridge is potentially not
    going to see any reports even though listeners exist because according
    to RFC4541 such reports are only forwarded to multicast routers:
    
    -----------------------------------------------------------
                ---------------
    {Querier}---|Snoop. Switch|----{Listener}
                ---------------
                           \           ^
                          -------
                          | br0 |  <  ???
                          -------
                              \
                         _-~---~_
                     _-~/        ~-_
                    ~   batman-adv  \-----{Sender}
                    \~_   cloud    ~/
                       -~~__-__-~_/
    
    I)  MLDv1 Query:  {Querier}  -> flooded
    II) MLDv1 Report: {Listener} -> {Querier}
    
    -> br0 cannot detect the {Listener}
    => Packets from {Sender} need to be forwarded to all
       detected listeners and MLDv1/IGMPv1/IGMPv2 queriers.
    
    -----------------------------------------------------------
    
    Note that we do not need to explicitly forward to MLDv2/IGMPv3 queriers,
    because these protocols have no report suppression: A bridge has no
    trouble detecting MLDv2/IGMPv3 listeners.
    
    Even though we do not support bridges yet we need to provide the
    according infrastructure already to not break compatibility later.
    Signed-off-by: default avatarLinus Lüssing <linus.luessing@web.de>
    Signed-off-by: default avatarMarek Lindner <mareklindner@neomailbox.ch>
    Signed-off-by: default avatarAntonio Quartulli <antonio@meshcoding.com>
    4c8755d6
types.h 45.8 KB