batman-adv: drop STP over batman

Signed-off-by: Simon Wunderlich <siwu@hrz.tu-chemnitz.de>
Signed-off-by: Antonio Quartulli <ordex@autistici.org>

net/batman-adv/soft-interface.c

@@ -130,6 +130,8 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
 	struct hard_iface *primary_if = NULL;
 	struct bcast_packet *bcast_packet;
 	struct vlan_ethhdr *vhdr;
+	static const uint8_t stp_addr[ETH_ALEN] = {0x01, 0x80, 0xC2, 0x00, 0x00,
+						   0x00};
 	unsigned int header_len = 0;
 	int data_len = skb->len, ret;
 	short vid = -1;
@@ -159,6 +161,12 @@ static int interface_tx(struct sk_buff *skb, struct net_device *soft_iface)
 	/* Register the client MAC in the transtable */
 	tt_local_add(soft_iface, ethhdr->h_source, skb->skb_iif);
 
+	/* don't accept stp packets. STP does not help in meshes.
+	 * better use the bridge loop avoidance ...
+	 */
+	if (compare_eth(ethhdr->h_dest, stp_addr))
+		goto dropped;
+
 	if (is_multicast_ether_addr(ethhdr->h_dest)) {
 		do_bcast = true;