bonding: remove packet cloning in recv_probe()

Cloning all packets in input path have a significant cost.

Use skb_header_pointer()/skb_copy_bits() instead of pskb_may_pull() so
that recv_probe handlers (bond_3ad_lacpdu_recv / bond_arp_rcv /
rlb_arp_recv ) dont touch input skb.

bond_handle_frame() can avoid the skb_clone()/dev_kfree_skb()

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: Jay Vosburgh <fubar@us.ibm.com>
Cc: Andy Gospodarek <andy@greyhouse.net>
Cc: Jiri Bohac <jbohac@suse.cz>
Cc: Nicolas de Pesloüan <nicolas.2p.debian@free.fr>
Cc: Maciej Żenczykowski <maze@google.com>
Signed-off-by: Jay Vosburgh <fubar@us.ibm.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/bonding/bond_alb.c

@@ -342,27 +342,17 @@ static void rlb_update_entry_from_arp(struct bonding *bond, struct arp_pkt *arp)
 	_unlock_rx_hashtbl_bh(bond);
 }
 
-static int rlb_arp_recv(struct sk_buff *skb, struct bonding *bond,
-			 struct slave *slave)
+static int rlb_arp_recv(const struct sk_buff *skb, struct bonding *bond,
+			struct slave *slave)
 {
-	struct arp_pkt *arp;
+	struct arp_pkt *arp, _arp;
 
 	if (skb->protocol != cpu_to_be16(ETH_P_ARP))
 		goto out;
 
-	arp = (struct arp_pkt *) skb->data;
-	if (!arp) {
-		pr_debug("Packet has no ARP data\n");
+	arp = skb_header_pointer(skb, 0, sizeof(_arp), &_arp);
+	if (!arp)
 		goto out;
-	}
-
-	if (!pskb_may_pull(skb, arp_hdr_len(bond->dev)))
-		goto out;
-
-	if (skb->len < sizeof(struct arp_pkt)) {
-		pr_debug("Packet is too small to be an ARP\n");
-		goto out;
-	}
 
 	if (arp->op_code == htons(ARPOP_REPLY)) {
 		/* update rx hash table for this ARP */