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>
This commit is contained in:
Antonio Quartulli
@@ -19,6 +19,7 @@
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#include <linux/if_ether.h>
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#include <linux/if_arp.h>
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#include <net/arp.h>
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#include "main.h"
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#include "hash.h"
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@@ -27,6 +28,7 @@
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#include "originator.h"
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#include "send.h"
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#include "types.h"
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#include "translation-table.h"
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#include "unicast.h"
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static void batadv_dat_purge(struct work_struct *work);
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@@ -766,3 +768,266 @@ static uint16_t batadv_arp_get_type(struct batadv_priv *bat_priv,
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out:
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return type;
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}
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/**
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* batadv_dat_snoop_outgoing_arp_request - snoop the ARP request and try to
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* answer using DAT
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* @bat_priv: the bat priv with all the soft interface information
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* @skb: packet to check
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*
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* Returns true if the message has been sent to the dht candidates, false
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* otherwise. In case of true the message has to be enqueued to permit the
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* fallback
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*/
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bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
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struct sk_buff *skb)
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{
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uint16_t type = 0;
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__be32 ip_dst, ip_src;
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uint8_t *hw_src;
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bool ret = false;
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struct batadv_dat_entry *dat_entry = NULL;
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struct sk_buff *skb_new;
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struct batadv_hard_iface *primary_if = NULL;
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type = batadv_arp_get_type(bat_priv, skb, 0);
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/* If the node gets an ARP_REQUEST it has to send a DHT_GET unicast
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* message to the selected DHT candidates
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*/
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if (type != ARPOP_REQUEST)
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goto out;
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batadv_dbg_arp(bat_priv, skb, type, 0, "Parsing outgoing ARP REQUEST");
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ip_src = batadv_arp_ip_src(skb, 0);
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hw_src = batadv_arp_hw_src(skb, 0);
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ip_dst = batadv_arp_ip_dst(skb, 0);
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batadv_dat_entry_add(bat_priv, ip_src, hw_src);
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dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst);
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if (dat_entry) {
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primary_if = batadv_primary_if_get_selected(bat_priv);
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if (!primary_if)
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goto out;
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skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src,
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primary_if->soft_iface, ip_dst, hw_src,
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dat_entry->mac_addr, hw_src);
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if (!skb_new)
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goto out;
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skb_reset_mac_header(skb_new);
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skb_new->protocol = eth_type_trans(skb_new,
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primary_if->soft_iface);
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bat_priv->stats.rx_packets++;
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bat_priv->stats.rx_bytes += skb->len + ETH_HLEN;
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primary_if->soft_iface->last_rx = jiffies;
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netif_rx(skb_new);
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batadv_dbg(BATADV_DBG_DAT, bat_priv, "ARP request replied locally\n");
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ret = true;
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} else {
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/* Send the request on the DHT */
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ret = batadv_dat_send_data(bat_priv, skb, ip_dst,
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BATADV_P_DAT_DHT_GET);
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}
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out:
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if (dat_entry)
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batadv_dat_entry_free_ref(dat_entry);
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if (primary_if)
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batadv_hardif_free_ref(primary_if);
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return ret;
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}
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/**
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* batadv_dat_snoop_incoming_arp_request - snoop the ARP request and try to
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* answer using the local DAT storage
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* @bat_priv: the bat priv with all the soft interface information
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* @skb: packet to check
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* @hdr_size: size of the encapsulation header
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*
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* Returns true if the request has been answered, false otherwise
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*/
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bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
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struct sk_buff *skb, int hdr_size)
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{
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uint16_t type;
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__be32 ip_src, ip_dst;
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uint8_t *hw_src;
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struct sk_buff *skb_new;
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struct batadv_hard_iface *primary_if = NULL;
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struct batadv_dat_entry *dat_entry = NULL;
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bool ret = false;
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int err;
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type = batadv_arp_get_type(bat_priv, skb, hdr_size);
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if (type != ARPOP_REQUEST)
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goto out;
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hw_src = batadv_arp_hw_src(skb, hdr_size);
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ip_src = batadv_arp_ip_src(skb, hdr_size);
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ip_dst = batadv_arp_ip_dst(skb, hdr_size);
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batadv_dbg_arp(bat_priv, skb, type, hdr_size,
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"Parsing incoming ARP REQUEST");
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batadv_dat_entry_add(bat_priv, ip_src, hw_src);
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dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst);
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if (!dat_entry)
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goto out;
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primary_if = batadv_primary_if_get_selected(bat_priv);
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if (!primary_if)
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goto out;
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skb_new = arp_create(ARPOP_REPLY, ETH_P_ARP, ip_src,
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primary_if->soft_iface, ip_dst, hw_src,
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dat_entry->mac_addr, hw_src);
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if (!skb_new)
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goto out;
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/* to preserve backwards compatibility, here the node has to answer
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* using the same packet type it received for the request. This is due
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* to that if a node is not using the 4addr packet format it may not
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* support it.
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*/
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if (hdr_size == sizeof(struct batadv_unicast_4addr_packet))
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err = batadv_unicast_4addr_send_skb(bat_priv, skb_new,
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BATADV_P_DAT_CACHE_REPLY);
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else
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err = batadv_unicast_send_skb(bat_priv, skb_new);
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if (!err)
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ret = true;
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out:
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if (dat_entry)
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batadv_dat_entry_free_ref(dat_entry);
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if (primary_if)
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batadv_hardif_free_ref(primary_if);
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if (ret)
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kfree_skb(skb);
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return ret;
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}
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/**
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* batadv_dat_snoop_outgoing_arp_reply - snoop the ARP reply and fill the DHT
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* @bat_priv: the bat priv with all the soft interface information
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* @skb: packet to check
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*/
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void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
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struct sk_buff *skb)
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{
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uint16_t type;
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__be32 ip_src, ip_dst;
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uint8_t *hw_src, *hw_dst;
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type = batadv_arp_get_type(bat_priv, skb, 0);
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if (type != ARPOP_REPLY)
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return;
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batadv_dbg_arp(bat_priv, skb, type, 0, "Parsing outgoing ARP REPLY");
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hw_src = batadv_arp_hw_src(skb, 0);
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ip_src = batadv_arp_ip_src(skb, 0);
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hw_dst = batadv_arp_hw_dst(skb, 0);
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ip_dst = batadv_arp_ip_dst(skb, 0);
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batadv_dat_entry_add(bat_priv, ip_src, hw_src);
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batadv_dat_entry_add(bat_priv, ip_dst, hw_dst);
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/* Send the ARP reply to the candidates for both the IP addresses that
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* the node got within the ARP reply
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*/
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batadv_dat_send_data(bat_priv, skb, ip_src, BATADV_P_DAT_DHT_PUT);
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batadv_dat_send_data(bat_priv, skb, ip_dst, BATADV_P_DAT_DHT_PUT);
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}
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/**
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* batadv_dat_snoop_incoming_arp_reply - snoop the ARP reply and fill the local
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* DAT storage only
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* @bat_priv: the bat priv with all the soft interface information
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* @skb: packet to check
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* @hdr_size: siaze of the encapsulation header
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*/
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bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
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struct sk_buff *skb, int hdr_size)
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{
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uint16_t type;
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__be32 ip_src, ip_dst;
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uint8_t *hw_src, *hw_dst;
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bool ret = false;
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type = batadv_arp_get_type(bat_priv, skb, hdr_size);
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if (type != ARPOP_REPLY)
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goto out;
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batadv_dbg_arp(bat_priv, skb, type, hdr_size,
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"Parsing incoming ARP REPLY");
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hw_src = batadv_arp_hw_src(skb, hdr_size);
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ip_src = batadv_arp_ip_src(skb, hdr_size);
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hw_dst = batadv_arp_hw_dst(skb, hdr_size);
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ip_dst = batadv_arp_ip_dst(skb, hdr_size);
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/* Update our internal cache with both the IP addresses the node got
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* within the ARP reply
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*/
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batadv_dat_entry_add(bat_priv, ip_src, hw_src);
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batadv_dat_entry_add(bat_priv, ip_dst, hw_dst);
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/* if this REPLY is directed to a client of mine, let's deliver the
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* packet to the interface
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*/
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ret = !batadv_is_my_client(bat_priv, hw_dst);
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out:
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/* if ret == false -> packet has to be delivered to the interface */
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return ret;
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}
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/**
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* batadv_dat_drop_broadcast_packet - check if an ARP request has to be dropped
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* (because the node has already got the reply via DAT) or not
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* @bat_priv: the bat priv with all the soft interface information
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* @forw_packet: the broadcast packet
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*
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* Returns true if the node can drop the packet, false otherwise
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*/
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bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
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struct batadv_forw_packet *forw_packet)
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{
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uint16_t type;
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__be32 ip_dst;
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struct batadv_dat_entry *dat_entry = NULL;
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bool ret = false;
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const size_t bcast_len = sizeof(struct batadv_bcast_packet);
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/* If this packet is an ARP_REQUEST and the node already has the
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* information that it is going to ask, then the packet can be dropped
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*/
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if (forw_packet->num_packets)
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goto out;
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type = batadv_arp_get_type(bat_priv, forw_packet->skb, bcast_len);
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if (type != ARPOP_REQUEST)
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goto out;
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ip_dst = batadv_arp_ip_dst(forw_packet->skb, bcast_len);
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dat_entry = batadv_dat_entry_hash_find(bat_priv, ip_dst);
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/* check if the node already got this entry */
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if (!dat_entry) {
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batadv_dbg(BATADV_DBG_DAT, bat_priv,
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"ARP Request for %pI4: fallback\n", &ip_dst);
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goto out;
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}
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batadv_dbg(BATADV_DBG_DAT, bat_priv,
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"ARP Request for %pI4: fallback prevented\n", &ip_dst);
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ret = true;
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out:
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if (dat_entry)
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batadv_dat_entry_free_ref(dat_entry);
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return ret;
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}
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