tcp: avoid two atomic ops for syncookies

inet_reqsk_alloc() is used to allocate a temporary request
in order to generate a SYNACK with a cookie. Then later,
syncookie validation also uses a temporary request.

These paths already took a reference on listener refcount,
we can avoid a couple of atomic operations.

Signed-off-by: Eric Dumazet <edumazet@google.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/net/ipv6/syncookies.c b/net/ipv6/syncookies.c
index 7606eba..f610b53 100644
--- a/net/ipv6/syncookies.c
+++ b/net/ipv6/syncookies.c
@@ -170,7 +170,7 @@
 		goto out;
 
 	ret = NULL;
-	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk);
+	req = inet_reqsk_alloc(&tcp6_request_sock_ops, sk, false);
 	if (!req)
 		goto out;