net: add common accessor for setting dropcount on packets

As part of an effort to move skb->dropcount to skb->cb[], use
a common function in order to set dropcount in struct sk_buff.
Signed-off-by: Eyal Birger <eyal.birger@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -2081,6 +2081,12 @@ static inline int sock_intr_errno(long timeo)
 #define sock_skb_cb_check_size(size) \
 	BUILD_BUG_ON((size) > FIELD_SIZEOF(struct sk_buff, cb))
 
+static inline void
+sock_skb_set_dropcount(const struct sock *sk, struct sk_buff *skb)
+{
+	skb->dropcount = atomic_read(&sk->sk_drops);
+}
+
 void __sock_recv_timestamp(struct msghdr *msg, struct sock *sk,
 			   struct sk_buff *skb);
 void __sock_recv_wifi_status(struct msghdr *msg, struct sock *sk,

net/core/sock.c

@@ -466,7 +466,7 @@ int sock_queue_rcv_skb(struct sock *sk, struct sk_buff *skb)
 	skb_dst_force(skb);
 
 	spin_lock_irqsave(&list->lock, flags);
-	skb->dropcount = atomic_read(&sk->sk_drops);
+	sock_skb_set_dropcount(sk, skb);
 	__skb_queue_tail(list, skb);
 	spin_unlock_irqrestore(&list->lock, flags);
 

net/packet/af_packet.c

@@ -1845,7 +1845,7 @@ static int packet_rcv(struct sk_buff *skb, struct net_device *dev,
 
 	spin_lock(&sk->sk_receive_queue.lock);
 	po->stats.stats1.tp_packets++;
-	skb->dropcount = atomic_read(&sk->sk_drops);
+	sock_skb_set_dropcount(sk, skb);
 	__skb_queue_tail(&sk->sk_receive_queue, skb);
 	spin_unlock(&sk->sk_receive_queue.lock);
 	sk->sk_data_ready(sk);