30 Oct
2011
30 Oct
'11
8:56 a.m.
ARP messages are now parsed to make it possible to trigger special actions
depending on their types (snooping).
Signed-off-by: Antonio Quartulli <ordex(a)autistici.org>
---
arp.c | 43 +++++++++++++++++++++++++++++++++++++++++++
arp.h | 7 +++++++
2 files changed, 50 insertions(+), 0 deletions(-)
diff --git a/arp.c b/arp.c
index 39043b8..ea7cc1e 100644
--- a/arp.c
+++ b/arp.c
@@ -183,3 +183,46 @@ out:
kfree(cand);
return ret;
}
+
+/* Returns arphdr->ar_op if the skb contains a valid ARP packet, otherwise
+ * returns 0 */
+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) + 8 + 12)))
+ 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(DBG_ARP, bat_priv, "ARP message of type %d recognised "
+ "[%pM-%pI4 %pM-%pI4]\n", type, ARP_HW_SRC(skb),
+ &ARP_IP_SRC(skb), ARP_HW_DST(skb), &ARP_IP_DST(skb));
+out:
+ return type;
+}
diff --git a/arp.h b/arp.h
index ee1a8b3..56b0a0a 100644
--- a/arp.h
+++ b/arp.h
@@ -22,6 +22,13 @@
#ifndef _NET_BATMAN_ADV_ARP_H_
#define _NET_BATMAN_ADV_ARP_H_
+#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))
+
+uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb);
+
/* 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