Comment 90 for bug 1711407

is it possibility that sk->sk_dst_cache is overwritten? like in __sk_dst_check,
when tcp timer tries to resend a packet, at the same time, tcp_close is called, and a reset packet will send, and ip_queue_xmit will be called concurrent；

cpu 1 cpu 2
tcp_close
   tcp_send_active_reset
      ip_queue_xmit
         __sk_dst_check {
            dst = __sk_dst_get(sk);
                                             tcp timer fire
                                             tcp_retransmit_timer
                                                   __tcp_retransmit_skb
                                                      ip_queue_xmit
                                                         sk_setup_caps
                                                            sk->sk_dst_cache is changed, like dst222

            RCU_INIT_POINTER(sk->sk_dst_cache, NULL);
                                                            dst222 is leaked
            dst_release(dst);