This patch is not a fix for the issue itself, but a fix for the other nodes, which are also influenced by the issue.

- Some (affected) nodes send TT announcements for an empty vlan (for now only seen with vlan_id = 0). - This behaviour is a bug! Batman-adv nodes must not send TT announcements for empty vlans. - The receiving batman-adv can not handle incoming TT announcements with empty vlans. (The crc check routine batadv_tt_global_check_crc() fails.) - As the receiving node thinks, the crc is broken, it does a full table request then. - The announcing node sends a TT full table to the receiving node then, which also contains the empty vlan, so *batadv_tt_global_check_crc()* fails again on the receiver side. - This causes a lot of unneeded TT traffic. In Freifunk Hannover we decreased the amount of from ~20kpp/s to ~4kpp/s on our supernodes. We have ~800 nodes, which are connected via vpn to one of six supernodes. Those supernodes are connected with each other in a fully connected mesh.

Signed-off-by: Leonardo Mörlein me@irrelefant.net --- net/batman-adv/translation-table.c | 17 +++++++++++++++-- 1 file changed, 15 insertions(+), 2 deletions(-)

diff --git a/net/batman-adv/translation-table.c b/net/batman-adv/translation-table.c index 0225616d..d2a843fd 100644 --- a/net/batman-adv/translation-table.c +++ b/net/batman-adv/translation-table.c @@ -2996,8 +2996,21 @@ static bool batadv_tt_global_check_crc(struct batadv_orig_node *orig_node,

vlan = batadv_orig_node_vlan_get(orig_node, ntohs(tt_vlan_tmp->vid)); - if (!vlan) - return false; + if (!vlan) { + /* Due to a bug, some originators send TT + * announcements for empty vlans. As the receiving + * nodes will ignore those empty vlans (they do not + * add a batadv_orig_node_vlan into the transglobal + * for the originating node), crc check will fail + * here. To circumvent this issue, we skip the + * verification for the vlan if the crc is + * equal to 0x00000000. + */ + if (tt_vlan_tmp->crc == 0x00000000) + continue; + else + return false; + }

crc = vlan->tt.crc; batadv_orig_node_vlan_put(vlan);