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>
diff --git a/include/net/sock.h b/include/net/sock.h
index a2502d2..0996fe4 100644
--- a/include/net/sock.h
+++ b/include/net/sock.h
@@ -2081,6 +2081,12 @@
 #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,