tcp: update the netstamp_needed counter when cloning sockets

This fixes a netstamp_needed accounting issue when the listen socket
has SO_TIMESTAMP set:

s = socket(AF_INET, SOCK_STREAM, 0);
setsockopt(s, SOL_SOCKET, SO_TIMESTAMP, 1); -> netstamp_needed = 1
bind(s, ...);
listen(s, ...);
s2 = accept(s, ...); -> netstamp_needed = 1
close(s2); -> netstamp_needed = 0
close(s); -> netstamp_needed = -1

Signed-off-by: Octavian Purdila <[e-mail]>
Signed-off-by: David S. Miller <[e-mail]>

net/core/sock.c

···
 
 		if (newsk->sk_prot->sockets_allocated)
 			percpu_counter_inc(newsk->sk_prot->sockets_allocated);
+
+		if (sock_flag(newsk, SOCK_TIMESTAMP) ||
+		    sock_flag(newsk, SOCK_TIMESTAMPING_RX_SOFTWARE))
+			net_enable_timestamp();
 	}
 out:
 	return newsk;