[B.A.T.M.A.N.] [PATCH 05/15] batman-adv: Distributed ARP Table - add ARP parsing functions

Antonio Quartulli
2012-04-25T13:27:01Z

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>
---
net/batman-adv/distributed-arp-table.c | 123 ++++++++++++++++++++++++++++++++
net/batman-adv/distributed-arp-table.h | 10 +++
net/batman-adv/packet.h | 5 +-
3 files changed, 137 insertions(+), 1 deletion(-)

diff --git a/net/batman-adv/distributed-arp-table.c b/net/batman-adv/distributed-arp-table.c
index 0078478..682fb1e 100644
--- a/net/batman-adv/distributed-arp-table.c
+++ b/net/batman-adv/distributed-arp-table.c
@@ -30,6 +30,75 @@
#include "types.h"
#include "unicast.h"

+#ifdef CONFIG_BATMAN_ADV_DEBUG
+
+static void bat_dbg_arp(struct bat_priv *bat_priv, struct sk_buff *skb,
+ uint16_t type, int hdr_size, char *msg)
+{
+ struct unicast_4addr_packet *unicast_4addr_packet;
+
+ if (msg)
+ bat_dbg(DBG_DAT, bat_priv, "%s\n", msg);
+
+ bat_dbg(DBG_DAT, bat_priv, "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
+ ARP_HW_SRC(skb, hdr_size), &ARP_IP_SRC(skb, hdr_size),
+ ARP_HW_DST(skb, hdr_size), &ARP_IP_DST(skb, hdr_size));
+
+ if (hdr_size == 0)
+ return;
+
+ /* if the AP packet is encapsulated in a batman packet, let's print some
+ * debug messages
+ */
+ unicast_4addr_packet = (struct unicast_4addr_packet *)skb->data;
+
+ switch (unicast_4addr_packet->u.header.packet_type) {
+ case BAT_UNICAST:
+ bat_dbg(DBG_DAT, bat_priv,
+ "* encapsulated within a UNICAST packet\n");
+ break;
+ case BAT_UNICAST_4ADDR:
+ bat_dbg(DBG_DAT, bat_priv,
+ "* encapsulated within a UNICAST_4ADDR packet (src: %pM)\n",
+ unicast_4addr_packet->src);
+ switch (unicast_4addr_packet->subtype) {
+ case BAT_P_DAT_DHT_PUT:
+ bat_dbg(DBG_DAT, bat_priv, "* type: DAT_DHT_PUT\n");
+ break;
+ case BAT_P_DAT_DHT_GET:
+ bat_dbg(DBG_DAT, bat_priv, "* type: DAT_DHT_GET\n");
+ break;
+ case BAT_P_DAT_CACHE_REPLY:
+ bat_dbg(DBG_DAT, bat_priv, "* type: DAT_CACHE_REPLY\n");
+ break;
+ case BAT_P_DATA:
+ bat_dbg(DBG_DAT, bat_priv, "* type: DATA\n");
+ break;
+ default:
+ bat_dbg(DBG_DAT, bat_priv, "* type: Unknown!\n");
+ }
+ break;
+ case BAT_BCAST:
+ bat_dbg(DBG_DAT, bat_priv,
+ "* encapsulated within a BCAST packet (src: %pM)\n",
+ ((struct bcast_packet *)unicast_4addr_packet)->orig);
+ break;
+ default:
+ bat_dbg(DBG_DAT, bat_priv,
+ "* encapsulated within an unknown packet type (0x%x)\n",
+ unicast_4addr_packet->u.header.packet_type);
+ }
+}
+
+#else
+
+static void bat_dbg_arp(struct bat_priv *bat_priv, struct sk_buff *skb,
+ uint16_t type, int hdr_size, char *msg)
+{
+}
+
+#endif /* CONFIG_BATMAN_ADV_DEBUG */
+
static bool is_orig_node_eligible(struct dht_candidate *res, int select,
dat_addr_t tmp_max, dat_addr_t max,
dat_addr_t last_max,
@@ -205,3 +274,57 @@ 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,
+ int hdr_size)
+{
+ struct arphdr *arphdr;
+ struct ethhdr *ethhdr;
+ uint32_t ip_src, ip_dst;
+ uint16_t type = 0;
+
+ /* pull the ethernet header */
+ if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
+ goto out;
+
+ ethhdr = (struct ethhdr *)(skb->data + hdr_size);
+
+ if (ethhdr->h_proto != htons(ETH_P_ARP))
+ goto out;
+
+ /* pull the ARP payload */
+ if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN +
+ arp_hdr_len(skb->dev))))
+ goto out;
+
+ arphdr = (struct arphdr *)(skb->data + hdr_size + ETH_HLEN);
+
+ /* 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;
+
+ /* Check for bad reply/request. If the ARP message is not sane, DAT
+ * will simply ignore it */
+ ip_src = ARP_IP_SRC(skb, hdr_size);
+ ip_dst = ARP_IP_DST(skb, hdr_size);
+ if (ipv4_is_loopback(ip_src) || ipv4_is_multicast(ip_src) ||
+ ipv4_is_loopback(ip_dst) || ipv4_is_multicast(ip_dst))
+ goto out;
+
+ type = ntohs(arphdr->ar_op);
+out:
+ return type;
+}
diff --git a/net/batman-adv/distributed-arp-table.h b/net/batman-adv/distributed-arp-table.h
index 94ee0fd..cdd0484 100644
--- a/net/batman-adv/distributed-arp-table.h
+++ b/net/batman-adv/distributed-arp-table.h
@@ -25,8 +25,18 @@
#include "types.h"
#include "originator.h"

+#include <linux/if_arp.h>
+
#define DAT_ADDR_MAX biggest_unsigned_int(dat_addr_t)

+#define ARP_HW_SRC(skb, hdr_size) ((uint8_t *)(skb->data + hdr_size) + \
+ ETH_HLEN + sizeof(struct arphdr))
+#define ARP_IP_SRC(skb, hdr_size) (*(uint32_t *)(ARP_HW_SRC(skb, hdr_size) + \
+ ETH_ALEN))
+#define ARP_HW_DST(skb, hdr_size) (ARP_HW_SRC(skb, hdr_size) + ETH_ALEN + 4)
+#define ARP_IP_DST(skb, hdr_size) (*(uint32_t *)(ARP_HW_SRC(skb, hdr_size) + \
+ 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
*/
diff --git a/net/batman-adv/packet.h b/net/batman-adv/packet.h
index e9f5184..c4533c4 100644
--- a/net/batman-adv/packet.h
+++ b/net/batman-adv/packet.h
@@ -37,7 +37,10 @@ enum bat_packettype {
};

enum bat_subtype {
- BAT_P_DATA = 0x01
+ BAT_P_DATA = 0x01,
+ BAT_P_DAT_DHT_GET = 0x02,
+ BAT_P_DAT_DHT_PUT = 0x03,
+ BAT_P_DAT_CACHE_REPLY = 0x04
};

/* this file is included by batctl which needs these defines */
--
1.7.9.4