The following commit has been merged in the master branch: commit f202a666e933f3c7557126d63833a6a3b577ac15 Author: Antonio Quartulli antonio@meshcoding.com Date: Tue Jun 16 21:06:24 2015 +0200

batman-adv: avoid DAT to mess up LAN state

When a node running DAT receives an ARP request from the LAN for the first time, it is likely that this node will request the ARP entry through the distributed ARP table (DAT) in the mesh.

Once a DAT reply is received the asking node must check if the MAC address for which the IP address has been asked is local. If it is, the node must drop the ARP reply bceause the client should have replied on its own locally.

Forwarding this reply means fooling any L2 bridge (e.g. Ethernet switches) lying between the batman-adv node and the LAN. This happens because the L2 bridge will think that the client sending the ARP reply lies somewhere in the mesh, while this node is sitting in the same LAN.

Reported-by: Simon Wunderlich sw@simonwunderlich.de Signed-off-by: Marek Lindner mareklindner@neomailbox.ch Signed-off-by: Antonio Quartulli antonio@meshcoding.com

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c index fb54e6a..6d0b471 100644 --- a/net/batman-adv/distributed-arp-table.c +++ b/net/batman-adv/distributed-arp-table.c @@ -1138,6 +1138,9 @@ void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv, * @bat_priv: the bat priv with all the soft interface information * @skb: packet to check * @hdr_size: size of the encapsulation header + * + * Returns true if the packet was snooped and consumed by DAT. False if the + * packet has to be delivered to the interface */ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv, struct sk_buff *skb, int hdr_size) @@ -1145,7 +1148,7 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv, uint16_t type; __be32 ip_src, ip_dst; uint8_t *hw_src, *hw_dst; - bool ret = false; + bool dropped = false; unsigned short vid;

if (!atomic_read(&bat_priv->distributed_arp_table)) @@ -1174,12 +1177,17 @@ bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv, /* if this REPLY is directed to a client of mine, let's deliver the * packet to the interface */ - ret = !batadv_is_my_client(bat_priv, hw_dst, vid); + dropped = !batadv_is_my_client(bat_priv, hw_dst, vid); + + /* if this REPLY is sent on behalf of a client of mine, let's drop the + * packet because the client will reply by itself + */ + dropped |= batadv_is_my_client(bat_priv, hw_src, vid); out: - if (ret) + if (dropped) kfree_skb(skb); - /* if ret == false -> packet has to be delivered to the interface */ - return ret; + /* if dropped == false -> deliver to the interface */ + return dropped; }

/**