6 files changed, 325 insertions, 2 deletions

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 49a213ce2aac..f43bf8e4a2b7 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 @@ static uint16_t batadv_arp_get_type(struct batadv_priv *bat_priv,
 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;
+}
diff --git a/net/batman-adv/distributed-arp-table.h b/net/batman-adv/distributed-arp-table.h
index f4e282a6e634..01308cea5b4e 100644
--- a/net/batman-adv/distributed-arp-table.h
+++ b/net/batman-adv/distributed-arp-table.h
@@ -27,6 +27,17 @@
 
 #define BATADV_DAT_ADDR_MAX ((batadv_dat_addr_t)~(batadv_dat_addr_t)0)
 
+bool batadv_dat_snoop_outgoing_arp_request(struct batadv_priv *bat_priv,
+                                           struct sk_buff *skb);
+bool batadv_dat_snoop_incoming_arp_request(struct batadv_priv *bat_priv,
+                                           struct sk_buff *skb, int hdr_size);
+void batadv_dat_snoop_outgoing_arp_reply(struct batadv_priv *bat_priv,
+                                         struct sk_buff *skb);
+bool batadv_dat_snoop_incoming_arp_reply(struct batadv_priv *bat_priv,
+                                         struct sk_buff *skb, int hdr_size);
+bool batadv_dat_drop_broadcast_packet(struct batadv_priv *bat_priv,
+                                      struct batadv_forw_packet *forw_packet);
+
 /**
  * batadv_dat_init_orig_node_addr - assign a DAT address to the orig_node
  * @orig_node: the node to assign the DAT address to
diff --git a/net/batman-adv/main.h b/net/batman-adv/main.h
index 25adfd29cc92..240c74ffeb93 100644
--- a/net/batman-adv/main.h
+++ b/net/batman-adv/main.h
@@ -74,6 +74,8 @@
 
 #define BATADV_LOG_BUF_LEN 8192   /* has to be a power of 2 */
 
+/* msecs after which an ARP_REQUEST is sent in broadcast as fallback */
+#define ARP_REQ_DELAY 250
 /* numbers of originator to contact for any PUT/GET DHT operation */
 #define BATADV_DAT_CANDIDATES_NUM 3
 
diff --git a/net/batman-adv/routing.c b/net/batman-adv/routing.c
index 859679b08286..1826699314b7 100644
--- a/net/batman-adv/routing.c
+++ b/net/batman-adv/routing.c
@@ -28,6 +28,7 @@
 #include "vis.h"
 #include "unicast.h"
 #include "bridge_loop_avoidance.h"
+#include "distributed-arp-table.h"
 
 static int batadv_route_unicast_packet(struct sk_buff *skb,
                                        struct batadv_hard_iface *recv_if);
@@ -985,11 +986,13 @@ int batadv_recv_unicast_packet(struct sk_buff *skb,
         struct batadv_priv *bat_priv = netdev_priv(recv_if->soft_iface);
         struct batadv_unicast_packet *unicast_packet;
         int hdr_size = sizeof(*unicast_packet);
+        bool is4addr;
 
         unicast_packet = (struct batadv_unicast_packet *)skb->data;
 
+        is4addr = unicast_packet->header.packet_type == BATADV_UNICAST_4ADDR;
         /* the caller function should have already pulled 2 bytes */
-        if (unicast_packet->header.packet_type == BATADV_UNICAST_4ADDR)
+        if (is4addr)
                 hdr_size = sizeof(struct batadv_unicast_4addr_packet);
 
         if (batadv_check_unicast_packet(skb, hdr_size) < 0)
@@ -1000,9 +1003,17 @@ int batadv_recv_unicast_packet(struct sk_buff *skb,
 
         /* packet for me */
         if (batadv_is_my_mac(unicast_packet->dest)) {
+                if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb,
+                                                          hdr_size))
+                        goto rx_success;
+                if (batadv_dat_snoop_incoming_arp_reply(bat_priv, skb,
+                                                        hdr_size))
+                        goto rx_success;
+
                 batadv_interface_rx(recv_if->soft_iface, skb, recv_if, hdr_size,
                                     NULL);
 
+rx_success:
                 return NET_RX_SUCCESS;
         }
 
@@ -1038,8 +1049,17 @@ int batadv_recv_ucast_frag_packet(struct sk_buff *skb,
                 if (!new_skb)
                         return NET_RX_SUCCESS;
 
+                if (batadv_dat_snoop_incoming_arp_request(bat_priv, new_skb,
+                                                          hdr_size))
+                        goto rx_success;
+                if (batadv_dat_snoop_incoming_arp_reply(bat_priv, new_skb,
+                                                        hdr_size))
+                        goto rx_success;
+
                 batadv_interface_rx(recv_if->soft_iface, new_skb, recv_if,
                                     sizeof(struct batadv_unicast_packet), NULL);
+
+rx_success:
                 return NET_RX_SUCCESS;
         }
 
@@ -1131,9 +1151,16 @@ int batadv_recv_bcast_packet(struct sk_buff *skb,
         if (batadv_bla_is_backbone_gw(skb, orig_node, hdr_size))
                 goto out;
 
+        if (batadv_dat_snoop_incoming_arp_request(bat_priv, skb, hdr_size))
+                goto rx_success;
+        if (batadv_dat_snoop_incoming_arp_reply(bat_priv, skb, hdr_size))
+                goto rx_success;
+
         /* broadcast for me */
         batadv_interface_rx(recv_if->soft_iface, skb, recv_if, hdr_size,
                             orig_node);
+
+rx_success:
         ret = NET_RX_SUCCESS;
         goto out;
 
diff --git a/net/batman-adv/send.c b/net/batman-adv/send.c
index 570a8bce0364..660d9bf7d219 100644
--- a/net/batman-adv/send.c
+++ b/net/batman-adv/send.c
@@ -18,6 +18,7 @@
  */
 
 #include "main.h"
+#include "distributed-arp-table.h"
 #include "send.h"
 #include "routing.h"
 #include "translation-table.h"
@@ -209,6 +210,9 @@ static void batadv_send_outstanding_bcast_packet(struct work_struct *work)
         if (atomic_read(&bat_priv->mesh_state) == BATADV_MESH_DEACTIVATING)
                 goto out;
 
+        if (batadv_dat_drop_broadcast_packet(bat_priv, forw_packet))
+                goto out;
+
         /* rebroadcast packet */
         rcu_read_lock();
         list_for_each_entry_rcu(hard_iface, &batadv_hardif_list, list) {
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 2f123a1b174b..9dc0ae1d4da3 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -20,6 +20,7 @@
 #include "main.h"
 #include "soft-interface.h"
 #include "hard-interface.h"
+#include "distributed-arp-table.h"
 #include "routing.h"
 #include "send.h"
 #include "debugfs.h"
@@ -155,6 +156,7 @@ static int batadv_interface_tx(struct sk_buff *skb,
         short vid __maybe_unused = -1;
         bool do_bcast = false;
         uint32_t seqno;
+        unsigned long brd_delay = 1;
 
         if (atomic_read(&bat_priv->mesh_state) != BATADV_MESH_ACTIVE)
                 goto dropped;
@@ -224,6 +226,13 @@ static int batadv_interface_tx(struct sk_buff *skb,
                 if (!primary_if)
                         goto dropped;
 
+                /* in case of ARP request, we do not immediately broadcasti the
+                 * packet, instead we first wait for DAT to try to retrieve the
+                 * correct ARP entry
+                 */
+                if (batadv_dat_snoop_outgoing_arp_request(bat_priv, skb))
+                        brd_delay = msecs_to_jiffies(ARP_REQ_DELAY);
+
                 if (batadv_skb_head_push(skb, sizeof(*bcast_packet)) < 0)
                         goto dropped;
 
@@ -245,7 +254,7 @@ static int batadv_interface_tx(struct sk_buff *skb,
                 seqno = atomic_inc_return(&bat_priv->bcast_seqno);
                 bcast_packet->seqno = htonl(seqno);
 
-                batadv_add_bcast_packet_to_list(bat_priv, skb, 1);
+                batadv_add_bcast_packet_to_list(bat_priv, skb, brd_delay);
 
                 /* a copy is stored in the bcast list, therefore removing
                  * the original skb.
@@ -260,6 +269,11 @@ static int batadv_interface_tx(struct sk_buff *skb,
                                 goto dropped;
                 }
 
+                if (batadv_dat_snoop_outgoing_arp_request(bat_priv, skb))
+                        goto dropped;
+
+                batadv_dat_snoop_outgoing_arp_reply(bat_priv, skb);
+
                 ret = batadv_unicast_send_skb(bat_priv, skb);
                 if (ret != 0)
                         goto dropped_freed;