A miscounting of nodes having multicast optimizations enabled can lead to multicast packet loss in the following scenario:

If the first OGM a node receives from another one has no multicast optimizations support (no multicast tvlv) then we are missing to increase the counter. This potentially leads to the wrong assumption that we could safely use multicast optimizations.

Fixings this by increasing the counter if the initial OGM has the multicast TVLV unset, too.

Introduced by 77ec494490d60d89b42cd01d5dbf8dee04503623 ("batman-adv: Announce new capability via multicast TVLV")

Reported-by: Tobias Hachmer tobias@hachmer.de Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue --- multicast.c | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-)

diff --git a/multicast.c b/multicast.c index 96b66fd..02c2e0c 100644 --- a/multicast.c +++ b/multicast.c @@ -686,11 +686,13 @@ static void batadv_mcast_tvlv_ogm_handler_v1(struct batadv_priv *bat_priv, if (orig_initialized) atomic_dec(&bat_priv->mcast.num_disabled); orig->capabilities |= BATADV_ORIG_CAPA_HAS_MCAST; - /* If mcast support is being switched off increase the disabled - * mcast node counter. + /* If mcast support is being switched off or if this is an initial + * OGM without mcast support then increase the disabled mcast + * node counter. */ } else if (!orig_mcast_enabled && - orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST) { + (orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST || + !orig_initialized)) { atomic_inc(&bat_priv->mcast.num_disabled); orig->capabilities &= ~BATADV_ORIG_CAPA_HAS_MCAST; }

When purging an orig_node we should only decrease counter tracking the number of nodes without multicast optimizations support if it was increased through this orig_node before.

A not yet quite initialized orig_node (meaning it did not have its turn in the mcast-tvlv handler so far) which gets purged would not adhere to this and will lead to a counter imbalance.

Fixing this by adding a check whether the orig_node is mcast-initalized before decreasing the counter in the mcast-orig_node-purging routine.

Introduced by 77ec494490d60d89b42cd01d5dbf8dee04503623 ("batman-adv: Announce new capability via multicast TVLV")

Reported-by: Tobias Hachmer tobias@hachmer.de Signed-off-by: Linus Lüssing linus.luessing@c0d3.blue --- multicast.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/multicast.c b/multicast.c index 02c2e0c..fe57bde 100644 --- a/multicast.c +++ b/multicast.c @@ -741,7 +741,8 @@ void batadv_mcast_purge_orig(struct batadv_orig_node *orig) { struct batadv_priv *bat_priv = orig->bat_priv;

- if (!(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST)) + if (!(orig->capabilities & BATADV_ORIG_CAPA_HAS_MCAST) && + orig->capa_initialized & BATADV_ORIG_CAPA_HAS_MCAST) atomic_dec(&bat_priv->mcast.num_disabled);

batadv_mcast_want_unsnoop_update(bat_priv, orig, BATADV_NO_FLAGS);