[B.A.T.M.A.N.] [PATCHv3 2/6] batman-adv: speed up dat by snooping received ip traffic

[Andreas Pape <apape@phoenixcontact.com>]

Speeding up dat address lookup is achieved by snooping all incoming ip
traffic. This especially increases the propability in bla setups that
a gateway into a common backbone network already has a fitting dat entry
to answer incoming ARP requests directly coming from the backbone
network thus further reducing ARP traffic in the mesh.

Signed-off-by: Andreas Pape <apape@phoenixcontact.com>
---
 net/batman-adv/distributed-arp-table.c |   50 ++++++++++++++++++++++++++++++++
 net/batman-adv/distributed-arp-table.h |    9 +++++-
 net/batman-adv/soft-interface.c        |    4 ++
 3 files changed, 62 insertions(+), 1 deletions(-)

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index c11f035..58cb488 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -27,6 +27,7 @@
 #include <linux/if_arp.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
+#include <linux/ip.h>
 #include <linux/in.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
@@ -362,6 +363,55 @@ out:
 		batadv_dat_entry_put(dat_entry);
 }

+/**
+ * batadv_dat_entry_check - check and update a dat entry
+ * @bat_priv: the bat priv with all the soft interface information
+ * @skb: socket buffer
+ * @vid: VLAN identifier
+ *
+ * snoops incoming socket buffer for dat cache updates, if dat is enabled.
+ * Can be called from other modules.
+ */
+void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			    unsigned short vid)
+{
+	struct vlan_ethhdr *vhdr = NULL, tmp_vhdr;
+	struct ethhdr *ethhdr = NULL;
+	struct iphdr *iphdr = NULL, tmp_iphdr;
+
+	if (!atomic_read(&bat_priv->distributed_arp_table))
+		return;
+
+	ethhdr = eth_hdr(skb);
+
+	switch (ntohs(ethhdr->h_proto)) {
+	case ETH_P_IP:
+		iphdr = skb_header_pointer(skb, ETH_HLEN, sizeof(tmp_iphdr),
+					   &tmp_iphdr);
+		break;
+	case ETH_P_8021Q:
+		vhdr = skb_header_pointer(skb, 0, sizeof(tmp_vhdr),
+					  &tmp_vhdr);
+		if (!vhdr)
+			break;
+		if (ntohs(vhdr->h_vlan_encapsulated_proto) == ETH_P_IP) {
+			iphdr = skb_header_pointer(skb, sizeof(tmp_vhdr),
+						   sizeof(tmp_iphdr),
+						   &tmp_iphdr);
+		}
+		break;
+	}
+
+	if (iphdr) {
+		batadv_dbg(BATADV_DBG_DAT, bat_priv,
+			   "Snooped IP address: %pI4 %pM (vid: %d)\n",
+			   &iphdr->saddr, ethhdr->h_source,
+			   BATADV_PRINT_VID(vid));
+		batadv_dat_entry_add(bat_priv, iphdr->saddr,
+				     ethhdr->h_source, vid);
+	}
+}
+
 #ifdef CONFIG_BATMAN_ADV_DEBUG

 /**
diff --git a/net/batman-adv/distributed-arp-table.h b/net/batman-adv/distributed-arp-table.h
index 813ecea..cf1b93c 100644
--- a/net/batman-adv/distributed-arp-table.h
+++ b/net/batman-adv/distributed-arp-table.h
@@ -80,7 +80,8 @@ batadv_dat_init_own_addr(struct batadv_priv *bat_priv,
 int batadv_dat_init(struct batadv_priv *bat_priv);
 void batadv_dat_free(struct batadv_priv *bat_priv);
 int batadv_dat_cache_seq_print_text(struct seq_file *seq, void *offset);
-
+void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			    unsigned short vid);
 /**
  * batadv_dat_inc_counter - increment the correct DAT packet counter
  * @bat_priv: the bat priv with all the soft interface information
@@ -173,6 +174,12 @@ static inline void batadv_dat_inc_counter(struct batadv_priv *bat_priv,
 {
 }

+static inline
+void batadv_dat_entry_check(struct batadv_priv *bat_priv, struct sk_buff *skb,
+			    unsigned short vid)
+{
+}
+
 #endif /* CONFIG_BATMAN_ADV_DAT */

 #endif /* _NET_BATMAN_ADV_DISTRIBUTED_ARP_TABLE_H_ */
diff --git a/net/batman-adv/soft-interface.c b/net/batman-adv/soft-interface.c
index 81665b1..1f1742a 100644
--- a/net/batman-adv/soft-interface.c
+++ b/net/batman-adv/soft-interface.c
@@ -28,6 +28,7 @@
 #include <linux/fs.h>
 #include <linux/if_ether.h>
 #include <linux/if_vlan.h>
+#include <linux/ip.h>
 #include <linux/jiffies.h>
 #include <linux/kernel.h>
 #include <linux/kref.h>
@@ -442,6 +443,9 @@ void batadv_interface_rx(struct net_device *soft_iface,
 		goto dropped;
 	}

+	/* Snoop incoming traffic for dat update */
+	batadv_dat_entry_check(bat_priv, skb, vid);
+
 	/* skb->dev & skb->pkt_type are set here */
 	skb->protocol = eth_type_trans(skb, soft_iface);

--
1.7.0.4



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