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 Reviewed-by: Simon Wunderlich siwu@hrz.tu-chemnitz.de --- distributed-arp-table.c | 51 +++++++++++++++++++++++++++++++++++++++++++++++ distributed-arp-table.h | 8 +++++++ 2 files changed, 59 insertions(+), 0 deletions(-)
diff --git a/distributed-arp-table.c b/distributed-arp-table.c index 5bc3004..5fad513 100644 --- a/distributed-arp-table.c +++ b/distributed-arp-table.c @@ -179,3 +179,54 @@ 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; + char buf[30], *type_str[] = { "REQUEST", "REPLY", "RREQUEST", "RREPLY", + "InREQUEST", "InREPLY", "NAK" }; + + 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); + + if (type >= 1 && type <= 10) + scnprintf(buf, 30, "%s", type_str[type - 1]); + else + scnprintf(buf, 30, "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)); +out: + return type; +} diff --git a/distributed-arp-table.h b/distributed-arp-table.h index ee1a8b3..439af22 100644 --- a/distributed-arp-table.h +++ b/distributed-arp-table.h @@ -22,6 +22,14 @@ #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)