}
 
 /* RFC 5961 7 [ACK Throttling] */
-static void tcp_send_challenge_ack(struct sock *sk, const struct sk_buff *skb)
+static void tcp_send_challenge_ack(struct sock *sk)
 {
        /* unprotected vars, we dont care of overwrites */
        static u32 challenge_timestamp;
                /* RFC 5961 5.2 [Blind Data Injection Attack].[Mitigation] */
                if (before(ack, prior_snd_una - tp->max_window)) {
                        if (!(flag & FLAG_NO_CHALLENGE_ACK))
-                               tcp_send_challenge_ack(sk, skb);
+                               tcp_send_challenge_ack(sk);
                        return -1;
                }
                goto old_ack;
                        if (tp->syn_fastopen && !tp->data_segs_in &&
                            sk->sk_state == TCP_ESTABLISHED)
                                tcp_fastopen_active_disable(sk);
-                       tcp_send_challenge_ack(sk, skb);
+                       tcp_send_challenge_ack(sk);
                }
                goto discard;
        }
                if (syn_inerr)
                        TCP_INC_STATS(sock_net(sk), TCP_MIB_INERRS);
                NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPSYNCHALLENGE);
-               tcp_send_challenge_ack(sk, skb);
+               tcp_send_challenge_ack(sk);
                goto discard;
        }
 
        if (!acceptable) {
                if (sk->sk_state == TCP_SYN_RECV)
                        return 1;       /* send one RST */
-               tcp_send_challenge_ack(sk, skb);
+               tcp_send_challenge_ack(sk);
                goto discard;
        }
        switch (sk->sk_state) {