batman-adv: limit local translation table max size

The local translation table size is limited by what can be
transferred from one node to another via a full table request.

The number of entries fitting into a full table request depend
on whether the fragmentation is enabled or not. Therefore this
patch introduces a max table size check and refuses to add
more local clients when that size is reached. Moreover, if the
max full table packet size changes (MTU change or fragmentation
is disabled) the local table is downsized instantaneously.

Signed-off-by: Marek Lindner <lindner_marek@yahoo.de>
Acked-by: Antonio Quartulli <ordex@autistici.org>

1 files changed, 26 insertions, 15 deletions

diff --git a/net/batman-adv/hard-interface.c b/net/batman-adv/hard-interface.c
index c5f871f..c60d3ed 100644
--- a/net/batman-adv/hard-interface.c
+++ b/net/batman-adv/hard-interface.c
@@ -266,16 +266,9 @@ static void batadv_check_known_mac_addr(const struct net_device *net_dev)
 
 int batadv_hardif_min_mtu(struct net_device *soft_iface)
 {
-	const struct batadv_priv *bat_priv = netdev_priv(soft_iface);
+	struct batadv_priv *bat_priv = netdev_priv(soft_iface);
 	const struct batadv_hard_iface *hard_iface;
-	/* allow big frames if all devices are capable to do so
-	 * (have MTU > 1500 + batadv_max_header_len())
-	 */
 	int min_mtu = ETH_DATA_LEN;
-	int max_header_len = batadv_max_header_len();
-
-	if (atomic_read(&bat_priv->fragmentation))
-		goto out;
 
 	rcu_read_lock();
 	list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
@@ -286,22 +279,40 @@ int batadv_hardif_min_mtu(struct net_device *soft_iface)
 		if (hard_iface->soft_iface != soft_iface)
 			continue;
 
-		min_mtu = min_t(int, hard_iface->net_dev->mtu - max_header_len,
-				min_mtu);
+		min_mtu = min_t(int, hard_iface->net_dev->mtu, min_mtu);
 	}
 	rcu_read_unlock();
+
+	atomic_set(&bat_priv->packet_size_max, min_mtu);
+
+	if (atomic_read(&bat_priv->fragmentation) == 0)
+		goto out;
+
+	/* with fragmentation enabled the maximum size of internally generated
+	 * packets such as translation table exchanges or tvlv containers, etc
+	 * has to be calculated
+	 */
+	min_mtu = min_t(int, min_mtu, BATADV_FRAG_MAX_FRAG_SIZE);
+	min_mtu -= sizeof(struct batadv_frag_packet);
+	min_mtu *= BATADV_FRAG_MAX_FRAGMENTS;
+	atomic_set(&bat_priv->packet_size_max, min_mtu);
+
+	/* with fragmentation enabled we can fragment external packets easily */
+	min_mtu = min_t(int, min_mtu, ETH_DATA_LEN);
+
 out:
-	return min_mtu;
+	return min_mtu - batadv_max_header_len();
 }
 
 /* adjusts the MTU if a new interface with a smaller MTU appeared. */
 void batadv_update_min_mtu(struct net_device *soft_iface)
 {
-	int min_mtu;
+	soft_iface->mtu = batadv_hardif_min_mtu(soft_iface);
 
-	min_mtu = batadv_hardif_min_mtu(soft_iface);
-	if (soft_iface->mtu != min_mtu)
-		soft_iface->mtu = min_mtu;
+	/* Check if the local translate table should be cleaned up to match a
+	 * new (and smaller) MTU.
+	 */
+	batadv_tt_local_resize_to_mtu(soft_iface);
 }
 
 static void