[B.A.T.M.A.N.] [PATCHv4 4/7] batman-adv: Distributed ARP Table - add ARP parsing functions

Antonio Quartulli
2011-11-24T22:21:16Z

ARP messages are now parsed to make it possible to trigger special actions
depending on their types (snooping).

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
---
distributed-arp-table.c | 59 +++++++++++++++++++++++++++++++++++++++++++++++
distributed-arp-table.h | 12 +++++++++
2 files changed, 71 insertions(+), 0 deletions(-)

diff --git a/distributed-arp-table.c b/distributed-arp-table.c
index 4c4e064..6cb60b0 100644
--- a/distributed-arp-table.c
+++ b/distributed-arp-table.c
@@ -30,6 +30,22 @@
#include "types.h"
#include "unicast.h"

+static inline void bat_dbg_arp(struct bat_priv *bat_priv,
+ struct sk_buff *skb, uint16_t type) {
+ char buf[30];
+ const char *type_str[] = { "REQUEST", "REPLY", "RREQUEST", "RREPLY",
+ "InREQUEST", "InREPLY", "NAK" };
+
+ if (type >= 1 && type <= ARRAY_SIZE(type_str))
+ scnprintf(buf, sizeof(buf), "%s", type_str[type - 1]);
+ else
+ scnprintf(buf, sizeof(buf), "UNKNOWN (%hu)", type);
+
+ bat_dbg(DBG_ARP, bat_priv, "ARP message of type %s recognised "
+ "[%pM-%pI4 %pM-%pI4]\n", buf, ARP_HW_SRC(skb), &ARP_IP_SRC(skb),
+ ARP_HW_DST(skb), &ARP_IP_DST(skb));
+}
+
/* Given a key, selects the candidates which the DHT message has to be sent to.
* An originator O is selected if and only if its DHT_ID value is one of three
* closest values (but not greater) then the hash value of the key.
@@ -180,3 +196,46 @@ out:
kfree(cand);
return ret;
}
+
+/* Returns arphdr->ar_op if the skb contains a valid ARP packet, otherwise
+ * returns 0 */
+static uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb)
+{
+ struct arphdr *arphdr;
+ struct ethhdr *ethhdr;
+ uint16_t type = 0;
+
+ if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
+ goto out;
+
+ ethhdr = (struct ethhdr *)skb_mac_header(skb);
+
+ if (ethhdr->h_proto != htons(ETH_P_ARP))
+ goto out;
+
+ if (unlikely(!pskb_may_pull(skb, ETH_HLEN + arp_hdr_len(skb->dev))))
+ goto out;
+
+ arphdr = (struct arphdr *)(skb->data + sizeof(struct ethhdr));
+
+ /* Check whether the ARP packet carries a valid
+ * IP information */
+ if (arphdr->ar_hrd != htons(ARPHRD_ETHER))
+ goto out;
+
+ if (arphdr->ar_pro != htons(ETH_P_IP))
+ goto out;
+
+ if (arphdr->ar_hln != ETH_ALEN)
+ goto out;
+
+ if (arphdr->ar_pln != 4)
+ goto out;
+
+ type = ntohs(arphdr->ar_op);
+
+ bat_dbg_arp(bat_priv, skb, type);
+
+out:
+ return type;
+}
diff --git a/distributed-arp-table.h b/distributed-arp-table.h
index cca5c6a..3e0f5c6 100644
--- a/distributed-arp-table.h
+++ b/distributed-arp-table.h
@@ -22,6 +22,12 @@
#ifndef _NET_BATMAN_ADV_ARP_H_
#define _NET_BATMAN_ADV_ARP_H_

+#include "main.h"
+
+#include <linux/if_arp.h>
+
+struct bat_priv;
+
/*
* dat_addr_t is the type used for all DHT indexes. If it is changed,
* DAT_ADDR_MAX is changed as well.
@@ -31,6 +37,12 @@
#define dat_addr_t uint16_t
#define DAT_ADDR_MAX biggest_unsigned_int(dat_addr_t)

+#define ARP_HW_SRC(skb) ((uint8_t *)(skb->data) + sizeof(struct ethhdr) + \
+ sizeof(struct arphdr))
+#define ARP_IP_SRC(skb) (*(uint32_t *)(ARP_HW_SRC(skb) + ETH_ALEN))
+#define ARP_HW_DST(skb) (ARP_HW_SRC(skb) + ETH_ALEN + 4)
+#define ARP_IP_DST(skb) (*(uint32_t *)(ARP_HW_SRC(skb) + ETH_ALEN * 2 + 4))
+
/* hash function to choose an entry in a hash table of given size */
/* hash algorithm from http://en.wikipedia.org/wiki/Hash_table */
static inline uint32_t hash_ipv4(const void *data, uint32_t size)
--
1.7.3.4