IP4_REPLY_MARK
u32 mark = IP4_REPLY_MARK(net, skb->mark);
mark = IP4_REPLY_MARK(net, skb_in->mark);
IP4_REPLY_MARK(net, skb->mark) ?: sk->sk_mark,
nskb->mark = IP4_REPLY_MARK(net, oldskb->mark);
u32 mark = IP4_REPLY_MARK(net, skb->mark);
fl4.flowi4_mark = IP4_REPLY_MARK(sock_net(sk), skb->mark);