--- linux-2.6.22.14/net/packet/af_packet.c	2008-01-22 13:57:20.000000000 +0200
+++ linux/net/packet/af_packet.c	2008-01-15 10:57:26.000000000 +0200
@@ -457,6 +457,14 @@ static int packet_rcv(struct sk_buff *sk
 	sk = pt->af_packet_priv;
 	po = pkt_sk(sk);
 
+	if (sk->sk_type == SOCK_DGRAM) {
+		if (skb->protocol != htons(ETH_P_IP))
+			goto drop;
+		
+		/* NOTE: incoming PPP packets can have ethernet header */
+		skb_pull(skb, skb_network_offset(skb));
+	}
+
 	skb->dev = dev;
 
 	if (dev->hard_header) {
@@ -573,6 +581,14 @@ static int tpacket_rcv(struct sk_buff *s
 	sk = pt->af_packet_priv;
 	po = pkt_sk(sk);
 
+	if (sk->sk_type == SOCK_DGRAM) {
+		if (skb->protocol != htons(ETH_P_IP))
+			goto drop;
+		
+		/* NOTE: incoming PPP packets can have ethernet header */
+		skb_pull(skb, skb_network_offset(skb));
+	}
+
 	if (dev->hard_header) {
 		if (sk->sk_type != SOCK_DGRAM)
 			skb_push(skb, skb->data - skb_mac_header(skb));