batman-adv: Distributed ARP Table - add snooping functions for ARP messages
In case of an ARP message going in or out the soft_iface, it is intercepted and
a special action is performed. In particular the DHT helper functions previously
implemented are used to store all the ARP entries belonging to the network in
order to provide a fast and unicast lookup instead of the classic broadcast
flooding mechanism.
Each node stores the entries it is responsible for (following the DHT rules) in
its soft_iface ARP table. This makes it possible to reuse the kernel data
structures and functions for ARP management.
Signed-off-by: Antonio Quartulli <ordex@autistici.org>
diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 49a213c..f43bf8e 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -19,6 +19,7 @@
#include <linux/if_ether.h>
#include <linux/if_arp.h>
+#include <net/arp.h>
#include "main.h"
#include "hash.h"
@@ -27,6 +28,7 @@
#include "originator.h"
#include "send.h"
#include "types.h"
+#include "translation-table.h"
#include "unicast.h"
static void batadv_dat_purge(struct work_struct *work);
@@ -766,3 +768,266 @@
out:
return type;
}
+
+/**
+ * batadv_dat_snoop_outgoing_arp_request - snoop the ARP request and try to
+ * answer using DAT
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: packet to check
+ *
+ * Returns true if the message has been sent to the dht candidates, false
+ * otherwise. In case of true the message has to be enqueued to permit the
+ * fallback
+ */
+bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
+ struct sk_buff *skb)
+{
+ uint16_t type = 0;
+ __be32 ip_dst, ip_src;
+ uint8_t *hw_src;
+ bool ret = false;
+ struct batadv_dat_entry *dat_entry = NULL;
+ struct sk_buff *skb_new;
+ struct batadv_hard_iface *primary_if = NULL;
+
+ type = batadv_arp_get_type(bat_priv, skb, 0);
+ /* If the node gets an ARP_REQUEST it has to send a DHT_GET unicast
+ * message to the selected DHT candidates
+ */
+ if (type != ARPOP_REQUEST)
+ goto out;
+
+ batadv_dbg_arp(bat_priv, skb, type, 0, "Parsing outgoing ARP REQUEST");
+
+ ip_src = batadv_arp_ip_src(skb, 0);
+ hw_src = batadv_arp_hw_src(skb, 0);
+ ip_dst = batadv_arp_ip_dst(skb, 0);
+
+ batadv_dat_entry_add(bat_priv, ip_src, hw_src);
+
+ dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst);
+ if (dat_entry) {
+ primary_if = batadv_primary_if_get_selected(bat_priv);
+ if (!primary_if)
+ goto out;
+
+ skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src,
+ primary_if->soft_iface, ip_dst, hw_src,
+ dat_entry->mac_addr, hw_src);
+ if (!skb_new)
+ goto out;
+
+ skb_reset_mac_header(skb_new);
+ skb_new->protocol = eth_type_trans(skb_new,
+ primary_if->soft_iface);
+ bat_priv->stats.rx_packets++;
+ bat_priv->stats.rx_bytes += skb->len + ETH_HLEN;
+ primary_if->soft_iface->last_rx = jiffies;
+
+ netif_rx(skb_new);
+ batadv_dbg(BATADV_DBG_DAT, bat_priv, "ARP request replied locally\n");
+ ret = true;
+ } else {
+ /* Send the request on the DHT */
+ ret = batadv_dat_send_data(bat_priv, skb, ip_dst,
+ BATADV_P_DAT_DHT_GET);
+ }
+out:
+ if (dat_entry)
+ batadv_dat_entry_free_ref(dat_entry);
+ if (primary_if)
+ batadv_hardif_free_ref(primary_if);
+ return ret;
+}
+
+/**
+ * batadv_dat_snoop_incoming_arp_request - snoop the ARP request and try to
+ * answer using the local DAT storage
+ * @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 request has been answered, false otherwise
+ */
+bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
+ struct sk_buff *skb, int hdr_size)
+{
+ uint16_t type;
+ __be32 ip_src, ip_dst;
+ uint8_t *hw_src;
+ struct sk_buff *skb_new;
+ struct batadv_hard_iface *primary_if = NULL;
+ struct batadv_dat_entry *dat_entry = NULL;
+ bool ret = false;
+ int err;
+
+ type = batadv_arp_get_type(bat_priv, skb, hdr_size);
+ if (type != ARPOP_REQUEST)
+ goto out;
+
+ hw_src = batadv_arp_hw_src(skb, hdr_size);
+ ip_src = batadv_arp_ip_src(skb, hdr_size);
+ ip_dst = batadv_arp_ip_dst(skb, hdr_size);
+
+ batadv_dbg_arp(bat_priv, skb, type, hdr_size,
+ "Parsing incoming ARP REQUEST");
+
+ batadv_dat_entry_add(bat_priv, ip_src, hw_src);
+
+ dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst);
+ if (!dat_entry)
+ goto out;
+
+ primary_if = batadv_primary_if_get_selected(bat_priv);
+ if (!primary_if)
+ goto out;
+
+ skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src,
+ primary_if->soft_iface, ip_dst, hw_src,
+ dat_entry->mac_addr, hw_src);
+
+ if (!skb_new)
+ goto out;
+
+ /* to preserve backwards compatibility, here the node has to answer
+ * using the same packet type it received for the request. This is due
+ * to that if a node is not using the 4addr packet format it may not
+ * support it.
+ */
+ if (hdr_size == sizeof(struct batadv_unicast_4addr_packet))
+ err = batadv_unicast_4addr_send_skb(bat_priv, skb_new,
+ BATADV_P_DAT_CACHE_REPLY);
+ else
+ err = batadv_unicast_send_skb(bat_priv, skb_new);
+
+ if (!err)
+ ret = true;
+out:
+ if (dat_entry)
+ batadv_dat_entry_free_ref(dat_entry);
+ if (primary_if)
+ batadv_hardif_free_ref(primary_if);
+ if (ret)
+ kfree_skb(skb);
+ return ret;
+}
+
+/**
+ * batadv_dat_snoop_outgoing_arp_reply - snoop the ARP reply and fill the DHT
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: packet to check
+ */
+void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
+ struct sk_buff *skb)
+{
+ uint16_t type;
+ __be32 ip_src, ip_dst;
+ uint8_t *hw_src, *hw_dst;
+
+ type = batadv_arp_get_type(bat_priv, skb, 0);
+ if (type != ARPOP_REPLY)
+ return;
+
+ batadv_dbg_arp(bat_priv, skb, type, 0, "Parsing outgoing ARP REPLY");
+
+ hw_src = batadv_arp_hw_src(skb, 0);
+ ip_src = batadv_arp_ip_src(skb, 0);
+ hw_dst = batadv_arp_hw_dst(skb, 0);
+ ip_dst = batadv_arp_ip_dst(skb, 0);
+
+ batadv_dat_entry_add(bat_priv, ip_src, hw_src);
+ batadv_dat_entry_add(bat_priv, ip_dst, hw_dst);
+
+ /* Send the ARP reply to the candidates for both the IP addresses that
+ * the node got within the ARP reply
+ */
+ batadv_dat_send_data(bat_priv, skb, ip_src, BATADV_P_DAT_DHT_PUT);
+ batadv_dat_send_data(bat_priv, skb, ip_dst, BATADV_P_DAT_DHT_PUT);
+}
+/**
+ * batadv_dat_snoop_incoming_arp_reply - snoop the ARP reply and fill the local
+ * DAT storage only
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: packet to check
+ * @hdr_size: siaze of the encapsulation header
+ */
+bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
+ struct sk_buff *skb, int hdr_size)
+{
+ uint16_t type;
+ __be32 ip_src, ip_dst;
+ uint8_t *hw_src, *hw_dst;
+ bool ret = false;
+
+ type = batadv_arp_get_type(bat_priv, skb, hdr_size);
+ if (type != ARPOP_REPLY)
+ goto out;
+
+ batadv_dbg_arp(bat_priv, skb, type, hdr_size,
+ "Parsing incoming ARP REPLY");
+
+ hw_src = batadv_arp_hw_src(skb, hdr_size);
+ ip_src = batadv_arp_ip_src(skb, hdr_size);
+ hw_dst = batadv_arp_hw_dst(skb, hdr_size);
+ ip_dst = batadv_arp_ip_dst(skb, hdr_size);
+
+ /* Update our internal cache with both the IP addresses the node got
+ * within the ARP reply
+ */
+ batadv_dat_entry_add(bat_priv, ip_src, hw_src);
+ batadv_dat_entry_add(bat_priv, ip_dst, hw_dst);
+
+ /* 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);
+out:
+ /* if ret == false -> packet has to be delivered to the interface */
+ return ret;
+}
+
+/**
+ * batadv_dat_drop_broadcast_packet - check if an ARP request has to be dropped
+ * (because the node has already got the reply via DAT) or not
+ * @bat_priv: the bat priv with all the soft interface information
+ * @forw_packet: the broadcast packet
+ *
+ * Returns true if the node can drop the packet, false otherwise
+ */
+bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
+ struct batadv_forw_packet *forw_packet)
+{
+ uint16_t type;
+ __be32 ip_dst;
+ struct batadv_dat_entry *dat_entry = NULL;
+ bool ret = false;
+ const size_t bcast_len = sizeof(struct batadv_bcast_packet);
+
+ /* If this packet is an ARP_REQUEST and the node already has the
+ * information that it is going to ask, then the packet can be dropped
+ */
+ if (forw_packet->num_packets)
+ goto out;
+
+ type = batadv_arp_get_type(bat_priv, forw_packet->skb, bcast_len);
+ if (type != ARPOP_REQUEST)
+ goto out;
+
+ ip_dst = batadv_arp_ip_dst(forw_packet->skb, bcast_len);
+ dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst);
+ /* check if the node already got this entry */
+ if (!dat_entry) {
+ batadv_dbg(BATADV_DBG_DAT, bat_priv,
+ "ARP Request for %pI4: fallback\n", &ip_dst);
+ goto out;
+ }
+
+ batadv_dbg(BATADV_DBG_DAT, bat_priv,
+ "ARP Request for %pI4: fallback prevented\n", &ip_dst);
+ ret = true;
+
+out:
+ if (dat_entry)
+ batadv_dat_entry_free_ref(dat_entry);
+ return ret;
+}