net: speedup sock_recv_ts_and_drops()

sock_recv_ts_and_drops() is fat and slow (~ 4% of cpu time on some
profiles)

We can test all socket flags at once to make fast path fast again.
Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/sock.h

@@ -1635,7 +1635,24 @@ sock_recv_timestamp(struct msghdr *msg, struct sock *sk, struct sk_buff *skb)
 		sk->sk_stamp = kt;
 }
 
-extern void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk, struct sk_buff *skb);
+extern void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
+				     struct sk_buff *skb);
+
+static inline void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
+					  struct sk_buff *skb)
+{
+#define FLAGS_TS_OR_DROPS ((1UL << SOCK_RXQ_OVFL)			| \
+			   (1UL << SOCK_RCVTSTAMP)			| \
+			   (1UL << SOCK_TIMESTAMPING_RX_SOFTWARE)	| \
+			   (1UL << SOCK_TIMESTAMPING_SOFTWARE)		| \
+			   (1UL << SOCK_TIMESTAMPING_RAW_HARDWARE) 	| \
+			   (1UL << SOCK_TIMESTAMPING_SYS_HARDWARE))
+
+	if (sk->sk_flags & FLAGS_TS_OR_DROPS)
+		__sock_recv_ts_and_drops(msg, sk, skb);
+	else
+		sk->sk_stamp = skb->tstamp;
+}
 
 /**
  * sock_tx_timestamp - checks whether the outgoing packet is to be time stamped

net/socket.c

@@ -655,13 +655,13 @@ inline void sock_recv_drops(struct msghdr *msg, struct sock *sk, struct sk_buff
 			sizeof(__u32), &skb->dropcount);
 }
 
-void sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
+void __sock_recv_ts_and_drops(struct msghdr *msg, struct sock *sk,
 	struct sk_buff *skb)
 {
 	sock_recv_timestamp(msg, sk, skb);
 	sock_recv_drops(msg, sk, skb);
 }
-EXPORT_SYMBOL_GPL(sock_recv_ts_and_drops);
+EXPORT_SYMBOL_GPL(__sock_recv_ts_and_drops);
 
 static inline int __sock_recvmsg_nosec(struct kiocb *iocb, struct socket *sock,
 				       struct msghdr *msg, size_t size, int flags)