diff mbox

[v5,9/9] batman-adv: Distributed ARP Table - use unicast_4addr_packet for DHT messages

Message ID 1328830902-11574-10-git-send-email-ordex@autistici.org (mailing list archive)
State Superseded, archived
Headers

Commit Message

Antonio Quartulli Feb. 9, 2012, 11:41 p.m. UTC 
  In order to enable an higher verbosity level of the DAT debug messages, the
unicast_4addr_packet is now used to carry ARP packets generated by the DAT
internal mechanism. This packet type will enable batman-adv to recognise each
DAT related message and to print its source (this will help to track possibly
bogus ARP entries)

Signed-off-by: Antonio Quartulli <ordex@autistici.org>
---
 distributed-arp-table.c |  129 +++++++++++++++++++++++++++++++---------------
 distributed-arp-table.h |   16 +++---
 soft-interface.c        |   15 +++--
 3 files changed, 105 insertions(+), 55 deletions(-)

Comments

Marek Lindner Feb. 11, 2012, 1:44 p.m. UTC | #1 
On Friday, February 10, 2012 07:41:42 Antonio Quartulli wrote:
> In order to enable an higher verbosity level of the DAT debug messages, the
> unicast_4addr_packet is now used to carry ARP packets generated by the DAT
> internal mechanism. This packet type will enable batman-adv to recognise
> each DAT related message and to print its source (this will help to track
> possibly bogus ARP entries)
> 
> Signed-off-by: Antonio Quartulli <ordex@autistici.org>
> ---
>  distributed-arp-table.c |  129
> +++++++++++++++++++++++++++++++--------------- distributed-arp-table.h |  
> 16 +++---
>  soft-interface.c        |   15 +++--
>  3 files changed, 105 insertions(+), 55 deletions(-)
> 
> diff --git a/distributed-arp-table.c b/distributed-arp-table.c
> index 48e97e0..239b5c4 100644
> --- a/distributed-arp-table.c
> +++ b/distributed-arp-table.c
> @@ -31,6 +31,7 @@
>  #include "originator.h"
>  #include "send.h"
>  #include "soft-interface.h"
> +#include "translation-table.h"
>  #include "types.h"
>  #include "translation-table.h"
>  #include "unicast.h"
> @@ -38,10 +39,44 @@
>  #ifdef CONFIG_BATMAN_ADV_DEBUG
> 
>  static inline void bat_dbg_arp(struct bat_priv *bat_priv,
> -			       struct sk_buff *skb, uint16_t type) {
> +			       struct sk_buff *skb, uint16_t type,
> +			       int hdr_size) {
> +	struct unicast_4addr_packet *unicast_4addr_packet;
> +
>  	bat_dbg(DBG_ARP, bat_priv, "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
> -		ARP_HW_SRC(skb), &ARP_IP_SRC(skb), ARP_HW_DST(skb),
> -		&ARP_IP_DST(skb));
> +		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_ARP, bat_priv, "encapsulated within a UNICAST "
> +			"packet\n");
> +		break;
> +	case BAT_UNICAST_4ADDR:
> +		bat_dbg(DBG_ARP, bat_priv, "encapsulated within a "
> +			"UNICAST_4ADDR packet (src: %pM)\n",
> +			unicast_4addr_packet->src);
> +		if (unicast_4addr_packet->subtype != BAT_P_DHT_PUT ||
> +		    unicast_4addr_packet->subtype != BAT_P_DHT_GET)
> +			bat_dbg(DBG_ARP, bat_priv, "It's a DAT message\n");

Isn't this check going to fail as soon as a new subtype was added ?


> +	unicast_4addr_packet = (struct unicast_4addr_packet *)skb->data;
> +
> +	if (dat_snoop_incoming_arp_request(bat_priv, skb, hdr_size))
> +		goto out;
> +
> +	if (dat_snoop_incoming_arp_reply(bat_priv, skb, hdr_size))
> +		goto out;
> +

The unicast_4addr_packet variable isn't used anywhere ...

Most of this patch simply adds a hdr_size variable to the functions added by 
earlier patches. Why not adding the unicast_4addr type at the beginning of the 
patch series ? You would not need this patch.

Cheers,
Marek
Antonio Quartulli Feb. 11, 2012, 1:57 p.m. UTC | #2 
On Sat, Feb 11, 2012 at 09:44:23PM +0800, Marek Lindner wrote:
> On Friday, February 10, 2012 07:41:42 Antonio Quartulli wrote:
> > In order to enable an higher verbosity level of the DAT debug messages, the
> > unicast_4addr_packet is now used to carry ARP packets generated by the DAT
> > internal mechanism. This packet type will enable batman-adv to recognise
> > each DAT related message and to print its source (this will help to track
> > possibly bogus ARP entries)
> > 
> > Signed-off-by: Antonio Quartulli <ordex@autistici.org>
> > ---
> >  distributed-arp-table.c |  129
> > +++++++++++++++++++++++++++++++--------------- distributed-arp-table.h |  
> > 16 +++---
> >  soft-interface.c        |   15 +++--
> >  3 files changed, 105 insertions(+), 55 deletions(-)
> > 
> > diff --git a/distributed-arp-table.c b/distributed-arp-table.c
> > index 48e97e0..239b5c4 100644
> > --- a/distributed-arp-table.c
> > +++ b/distributed-arp-table.c
> > @@ -31,6 +31,7 @@
> >  #include "originator.h"
> >  #include "send.h"
> >  #include "soft-interface.h"
> > +#include "translation-table.h"
> >  #include "types.h"
> >  #include "translation-table.h"
> >  #include "unicast.h"
> > @@ -38,10 +39,44 @@
> >  #ifdef CONFIG_BATMAN_ADV_DEBUG
> > 
> >  static inline void bat_dbg_arp(struct bat_priv *bat_priv,
> > -			       struct sk_buff *skb, uint16_t type) {
> > +			       struct sk_buff *skb, uint16_t type,
> > +			       int hdr_size) {
> > +	struct unicast_4addr_packet *unicast_4addr_packet;
> > +
> >  	bat_dbg(DBG_ARP, bat_priv, "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
> > -		ARP_HW_SRC(skb), &ARP_IP_SRC(skb), ARP_HW_DST(skb),
> > -		&ARP_IP_DST(skb));
> > +		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_ARP, bat_priv, "encapsulated within a UNICAST "
> > +			"packet\n");
> > +		break;
> > +	case BAT_UNICAST_4ADDR:
> > +		bat_dbg(DBG_ARP, bat_priv, "encapsulated within a "
> > +			"UNICAST_4ADDR packet (src: %pM)\n",
> > +			unicast_4addr_packet->src);
> > +		if (unicast_4addr_packet->subtype != BAT_P_DHT_PUT ||
> > +		    unicast_4addr_packet->subtype != BAT_P_DHT_GET)
> > +			bat_dbg(DBG_ARP, bat_priv, "It's a DAT message\n");
> 
> Isn't this check going to fail as soon as a new subtype was added ?
> 
> 
> > +	unicast_4addr_packet = (struct unicast_4addr_packet *)skb->data;
> > +
> > +	if (dat_snoop_incoming_arp_request(bat_priv, skb, hdr_size))
> > +		goto out;
> > +
> > +	if (dat_snoop_incoming_arp_reply(bat_priv, skb, hdr_size))
> > +		goto out;
> > +
> 
> The unicast_4addr_packet variable isn't used anywhere ...
> 
> Most of this patch simply adds a hdr_size variable to the functions added by 
> earlier patches. Why not adding the unicast_4addr type at the beginning of the 
> patch series ? You would not need this patch.

Thank you for your feedback.
Yes, you are right. Actually I didn't care about the "weight" of th patch: I
simply added the new type at the end and then applied the needed changes. But I
agree with you: moving the new type patch at the beginning is a good idea.

Cheers,

> 
> Cheers,
> Marek
diff mbox

Patch

diff --git a/distributed-arp-table.c b/distributed-arp-table.c
index 48e97e0..239b5c4 100644
--- a/distributed-arp-table.c
+++ b/distributed-arp-table.c
@@ -31,6 +31,7 @@ 
 #include "originator.h"
 #include "send.h"
 #include "soft-interface.h"
+#include "translation-table.h"
 #include "types.h"
 #include "translation-table.h"
 #include "unicast.h"
@@ -38,10 +39,44 @@ 
 #ifdef CONFIG_BATMAN_ADV_DEBUG
 
 static inline void bat_dbg_arp(struct bat_priv *bat_priv,
-			       struct sk_buff *skb, uint16_t type) {
+			       struct sk_buff *skb, uint16_t type,
+			       int hdr_size) {
+	struct unicast_4addr_packet *unicast_4addr_packet;
+
 	bat_dbg(DBG_ARP, bat_priv, "ARP MSG = [src: %pM-%pI4 dst: %pM-%pI4]\n",
-		ARP_HW_SRC(skb), &ARP_IP_SRC(skb), ARP_HW_DST(skb),
-		&ARP_IP_DST(skb));
+		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_ARP, bat_priv, "encapsulated within a UNICAST "
+			"packet\n");
+		break;
+	case BAT_UNICAST_4ADDR:
+		bat_dbg(DBG_ARP, bat_priv, "encapsulated within a "
+			"UNICAST_4ADDR packet (src: %pM)\n",
+			unicast_4addr_packet->src);
+		if (unicast_4addr_packet->subtype != BAT_P_DHT_PUT ||
+		    unicast_4addr_packet->subtype != BAT_P_DHT_GET)
+			bat_dbg(DBG_ARP, bat_priv, "It's a DAT message\n");
+		break;
+	case BAT_BCAST:
+		bat_dbg(DBG_ARP, bat_priv, "encapsulated within a BCAST packet "
+			"(src: %pM)\n",
+			((struct bcast_packet *)unicast_4addr_packet)->orig);
+		break;
+	default:
+		bat_dbg(DBG_ARP, bat_priv, "encapsulated within an unknown "
+			"packet type (0x%x)\n",
+			unicast_4addr_packet->u.header.packet_type);
+	}
 }
 
 #else
@@ -184,7 +219,8 @@  static bool dht_send_data(struct bat_priv *bat_priv, struct sk_buff *skb,
 			goto free_orig;
 
 		tmp_skb = pskb_copy(skb, GFP_ATOMIC);
-		if (prepare_unicast_packet(tmp_skb, cand[i].orig_node))
+		if (prepare_unicast_4addr_packet(bat_priv, tmp_skb,
+						 cand[i].orig_node))
 			send_skb_packet(tmp_skb, neigh_node->if_incoming,
 					neigh_node->addr);
 		else
@@ -228,24 +264,28 @@  out:
 
 /* 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)
+static uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb,
+			     int hdr_size)
 {
 	struct arphdr *arphdr;
 	struct ethhdr *ethhdr;
 	uint16_t type = 0;
 
-	if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
+	/* pull the ethernet header */
+	if (unlikely(!pskb_may_pull(skb, hdr_size + ETH_HLEN)))
 		goto out;
 
-	ethhdr = (struct ethhdr *)skb_mac_header(skb);
+	ethhdr = (struct ethhdr *)(skb->data + hdr_size);
 
 	if (ethhdr->h_proto != htons(ETH_P_ARP))
 		goto out;
 
-	if (unlikely(!pskb_may_pull(skb, ETH_HLEN + arp_hdr_len(skb->dev))))
+	/* 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 + sizeof(struct ethhdr));
+	arphdr = (struct arphdr *)(skb->data + hdr_size + ETH_HLEN);
 
 	/* Check whether the ARP packet carries a valid
 	 * IP information */
@@ -263,10 +303,10 @@  static uint16_t arp_get_type(struct bat_priv *bat_priv, struct sk_buff *skb)
 
 	/* Check for bad reply/request. If the ARP message is not sane, DAT
 	 * will simply ignore it */
-	if (ipv4_is_loopback(ARP_IP_SRC(skb)) ||
-	    ipv4_is_multicast(ARP_IP_SRC(skb)) ||
-	    ipv4_is_loopback(ARP_IP_DST(skb)) ||
-	    ipv4_is_multicast(ARP_IP_DST(skb)))
+	if (ipv4_is_loopback(ARP_IP_SRC(skb, hdr_size)) ||
+	    ipv4_is_multicast(ARP_IP_SRC(skb, hdr_size)) ||
+	    ipv4_is_loopback(ARP_IP_DST(skb, hdr_size)) ||
+	    ipv4_is_multicast(ARP_IP_DST(skb, hdr_size)))
 		goto out;
 
 	type = ntohs(arphdr->ar_op);
@@ -288,18 +328,18 @@  bool dat_snoop_outgoing_arp_request(struct bat_priv *bat_priv,
 	struct hard_iface *primary_if = NULL;
 	struct sk_buff *skb_new;
 
-	type = arp_get_type(bat_priv, skb);
+	type = arp_get_type(bat_priv, skb, 0);
 	/* If we get an ARP_REQUEST we have to send the unicast message to the
 	 * selected DHT candidates */
 	if (type != ARPOP_REQUEST)
 		goto out;
 
 	bat_dbg(DBG_ARP, bat_priv, "Parsing outgoing ARP REQUEST\n");
-	bat_dbg_arp(bat_priv, skb, type);
+	bat_dbg_arp(bat_priv, skb, type, 0);
 
-	ip_src = ARP_IP_SRC(skb);
-	hw_src = ARP_HW_SRC(skb);
-	ip_dst = ARP_IP_DST(skb);
+	ip_src = ARP_IP_SRC(skb, 0);
+	hw_src = ARP_HW_SRC(skb, 0);
+	ip_dst = ARP_IP_DST(skb, 0);
 
 	primary_if = primary_if_get_selected(bat_priv);
 	if (!primary_if)
@@ -341,7 +381,7 @@  out:
  * into the local table. If found, an ARP reply is sent immediately, otherwise
  * the caller has to deliver the ARP request to the upper layer */
 bool dat_snoop_incoming_arp_request(struct bat_priv *bat_priv,
-				    struct sk_buff *skb)
+				    struct sk_buff *skb, int hdr_size)
 {
 	uint16_t type;
 	uint32_t ip_src, ip_dst;
@@ -351,16 +391,16 @@  bool dat_snoop_incoming_arp_request(struct bat_priv *bat_priv,
 	struct neighbour *n = NULL;
 	bool ret = false;
 
-	type = arp_get_type(bat_priv, skb);
+	type = arp_get_type(bat_priv, skb, hdr_size);
 	if (type != ARPOP_REQUEST)
 		goto out;
 
-	hw_src = ARP_HW_SRC(skb);
-	ip_src = ARP_IP_SRC(skb);
-	ip_dst = ARP_IP_DST(skb);
+	hw_src = ARP_HW_SRC(skb, hdr_size);
+	ip_src = ARP_IP_SRC(skb, hdr_size);
+	ip_dst = ARP_IP_DST(skb, hdr_size);
 
 	bat_dbg(DBG_ARP, bat_priv, "Parsing incoming ARP REQUEST\n");
-	bat_dbg_arp(bat_priv, skb, type);
+	bat_dbg_arp(bat_priv, skb, type, hdr_size);
 
 	primary_if = primary_if_get_selected(bat_priv);
 	if (!primary_if)
@@ -380,7 +420,7 @@  bool dat_snoop_incoming_arp_request(struct bat_priv *bat_priv,
 	if (!skb_new)
 		goto out;
 
-	unicast_send_skb(skb_new, bat_priv);
+	unicast_4addr_send_skb(skb_new, bat_priv);
 
 	ret = true;
 out:
@@ -404,17 +444,17 @@  bool dat_snoop_outgoing_arp_reply(struct bat_priv *bat_priv,
 	uint8_t *hw_src, *hw_dst;
 	bool ret = false;
 
-	type = arp_get_type(bat_priv, skb);
+	type = arp_get_type(bat_priv, skb, 0);
 	if (type != ARPOP_REPLY)
 		goto out;
 
 	bat_dbg(DBG_ARP, bat_priv, "Parsing outgoing ARP REPLY\n");
-	bat_dbg_arp(bat_priv, skb, type);
+	bat_dbg_arp(bat_priv, skb, type, 0);
 
-	hw_src = ARP_HW_SRC(skb);
-	ip_src = ARP_IP_SRC(skb);
-	hw_dst = ARP_HW_DST(skb);
-	ip_dst = ARP_IP_DST(skb);
+	hw_src = ARP_HW_SRC(skb, 0);
+	ip_src = ARP_IP_SRC(skb, 0);
+	hw_dst = ARP_HW_DST(skb, 0);
+	ip_dst = ARP_IP_DST(skb, 0);
 
 	arp_neigh_update(bat_priv, ip_src, hw_src);
 	arp_neigh_update(bat_priv, ip_dst, hw_dst);
@@ -431,24 +471,24 @@  out:
 /* This function has to be invoked on an ARP reply coming into the soft
  * interface from the mesh network. The local table has to be updated */
 bool dat_snoop_incoming_arp_reply(struct bat_priv *bat_priv,
-				  struct sk_buff *skb)
+				  struct sk_buff *skb, int hdr_size)
 {
 	uint16_t type;
 	uint32_t ip_src, ip_dst;
 	uint8_t *hw_src, *hw_dst;
 	bool ret = false;
 
-	type = arp_get_type(bat_priv, skb);
+	type = arp_get_type(bat_priv, skb, hdr_size);
 	if (type != ARPOP_REPLY)
 		goto out;
 
 	bat_dbg(DBG_ARP, bat_priv, "Parsing incoming ARP REPLY\n");
-	bat_dbg_arp(bat_priv, skb, type);
+	bat_dbg_arp(bat_priv, skb, type, hdr_size);
 
-	hw_src = ARP_HW_SRC(skb);
-	ip_src = ARP_IP_SRC(skb);
-	hw_dst = ARP_HW_DST(skb);
-	ip_dst = ARP_IP_DST(skb);
+	hw_src = ARP_HW_SRC(skb, hdr_size);
+	ip_src = ARP_IP_SRC(skb, hdr_size);
+	hw_dst = ARP_HW_DST(skb, hdr_size);
+	ip_dst = ARP_IP_DST(skb, hdr_size);
 
 	/* Update our internal cache with both the IP addresses we fetched from
 	 * the ARP reply */
@@ -471,20 +511,25 @@  bool arp_drop_broadcast_packet(struct bat_priv *bat_priv,
 	/* If this packet is an ARP_REQUEST and we already have the information
 	 * that it is going to ask, we can drop the packet */
 	if (!forw_packet->num_packets &&
-			(arp_get_type(bat_priv, forw_packet->skb) ==
+			(arp_get_type(bat_priv, forw_packet->skb,
+				      sizeof(struct bcast_packet)) ==
 							ARPOP_REQUEST)) {
-		n = neigh_lookup(&arp_tbl, &ARP_IP_DST(forw_packet->skb),
+		n = neigh_lookup(&arp_tbl,
+				 &ARP_IP_DST(forw_packet->skb,
+					     sizeof(struct bcast_packet)),
 				 forw_packet->if_incoming->soft_iface);
 		/* check if we already know this neigh */
 		if (n && (n->nud_state & NUD_CONNECTED)) {
 			bat_dbg(DBG_ARP, bat_priv, "ARP Request for %pI4: "
 				"fallback prevented\n",
-				&ARP_IP_DST(forw_packet->skb));
+				&ARP_IP_DST(forw_packet->skb,
+					    sizeof(struct bcast_packet)));
 			return true;
 		}
 
 		bat_dbg(DBG_ARP, bat_priv, "ARP Request for %pI4: fallback\n",
-			&ARP_IP_DST(forw_packet->skb));
+			&ARP_IP_DST(forw_packet->skb,
+				    sizeof(struct bcast_packet)));
 	}
 	return false;
 }
diff --git a/distributed-arp-table.h b/distributed-arp-table.h
index 98fc2e1..a81b021 100644
--- a/distributed-arp-table.h
+++ b/distributed-arp-table.h
@@ -41,20 +41,22 @@  struct forw_packet;
 #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))
+#define ARP_HW_SRC(skb, hdr_size) ((uint8_t *)(skb->data + hdr_size) + \
+				sizeof(struct ethhdr) +	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))
 
 bool dat_snoop_outgoing_arp_request(struct bat_priv *bat_priv,
 				    struct sk_buff *skb);
 bool dat_snoop_incoming_arp_request(struct bat_priv *bat_priv,
-				    struct sk_buff *skb);
+				    struct sk_buff *skb, int hdr_size);
 bool dat_snoop_outgoing_arp_reply(struct bat_priv *bat_priv,
 				  struct sk_buff *skb);
 bool dat_snoop_incoming_arp_reply(struct bat_priv *bat_priv,
-				  struct sk_buff *skb);
+				  struct sk_buff *skb, int hdr_size);
 bool arp_drop_broadcast_packet(struct bat_priv *bat_priv,
 			       struct forw_packet *forw_packet);
 void arp_change_timeout(struct net_device *soft_iface, const char *name);
diff --git a/soft-interface.c b/soft-interface.c
index 4426e36..b21171b 100644
--- a/soft-interface.c
+++ b/soft-interface.c
@@ -258,6 +258,7 @@  void interface_rx(struct net_device *soft_iface,
 		  int hdr_size)
 {
 	struct bat_priv *bat_priv = netdev_priv(soft_iface);
+	struct unicast_4addr_packet *unicast_4addr_packet;
 	struct ethhdr *ethhdr;
 	struct vlan_ethhdr *vhdr;
 	short vid = -1;
@@ -266,6 +267,14 @@  void interface_rx(struct net_device *soft_iface,
 	if (!pskb_may_pull(skb, hdr_size))
 		goto dropped;
 
+	unicast_4addr_packet = (struct unicast_4addr_packet *)skb->data;
+
+	if (dat_snoop_incoming_arp_request(bat_priv, skb, hdr_size))
+		goto out;
+
+	if (dat_snoop_incoming_arp_reply(bat_priv, skb, hdr_size))
+		goto out;
+
 	skb_pull_rcsum(skb, hdr_size);
 	skb_reset_mac_header(skb);
 
@@ -284,12 +293,6 @@  void interface_rx(struct net_device *soft_iface,
 		goto dropped;
 	}
 
-	if (dat_snoop_incoming_arp_request(bat_priv, skb))
-		goto out;
-
-	if (dat_snoop_incoming_arp_reply(bat_priv, skb))
-		goto out;
-
 	/* skb->dev & skb->pkt_type are set here */
 	if (unlikely(!pskb_may_pull(skb, ETH_HLEN)))
 		goto dropped;