// SPDX-License-Identifier: GPL-2.0

  #include <linux/export.h>
  #include <linux/icmpv6.h>
  #include <linux/mutex.h>
  #include <linux/netdevice.h>
  #include <linux/spinlock.h>
  
  #include <net/ipv6.h>
  
  #if IS_ENABLED(CONFIG_IPV6)

  #if !IS_BUILTIN(CONFIG_IPV6)

  static ip6_icmp_send_t __rcu *ip6_icmp_send;
  
  int inet6_register_icmp_sender(ip6_icmp_send_t *fn)
  {
  	return (cmpxchg((ip6_icmp_send_t **)&ip6_icmp_send, NULL, fn) == NULL) ?

  		0 : -EBUSY;

  }
  EXPORT_SYMBOL(inet6_register_icmp_sender);
  
  int inet6_unregister_icmp_sender(ip6_icmp_send_t *fn)
  {
  	int ret;
  
  	ret = (cmpxchg((ip6_icmp_send_t **)&ip6_icmp_send, fn, NULL) == fn) ?
  	      0 : -EINVAL;
  
  	synchronize_net();
  
  	return ret;
  }
  EXPORT_SYMBOL(inet6_unregister_icmp_sender);
  
  void icmpv6_send(struct sk_buff *skb, u8 type, u8 code, __u32 info)
  {
  	ip6_icmp_send_t *send;
  
  	rcu_read_lock();
  	send = rcu_dereference(ip6_icmp_send);

  	if (send)
  		send(skb, type, code, info, NULL);

  	rcu_read_unlock();
  }
  EXPORT_SYMBOL(icmpv6_send);

  #endif

  
  #if IS_ENABLED(CONFIG_NF_NAT)
  #include <net/netfilter/nf_conntrack.h>
  void icmpv6_ndo_send(struct sk_buff *skb_in, u8 type, u8 code, __u32 info)
  {
  	struct sk_buff *cloned_skb = NULL;
  	enum ip_conntrack_info ctinfo;
  	struct in6_addr orig_ip;
  	struct nf_conn *ct;
  
  	ct = nf_ct_get(skb_in, &ctinfo);
  	if (!ct || !(ct->status & IPS_SRC_NAT)) {
  		icmpv6_send(skb_in, type, code, info);
  		return;
  	}
  
  	if (skb_shared(skb_in))
  		skb_in = cloned_skb = skb_clone(skb_in, GFP_ATOMIC);
  
  	if (unlikely(!skb_in || skb_network_header(skb_in) < skb_in->head ||
  	    (skb_network_header(skb_in) + sizeof(struct ipv6hdr)) >
  	    skb_tail_pointer(skb_in) || skb_ensure_writable(skb_in,
  	    skb_network_offset(skb_in) + sizeof(struct ipv6hdr))))
  		goto out;
  
  	orig_ip = ipv6_hdr(skb_in)->saddr;
  	ipv6_hdr(skb_in)->saddr = ct->tuplehash[0].tuple.src.u3.in6;
  	icmpv6_send(skb_in, type, code, info);
  	ipv6_hdr(skb_in)->saddr = orig_ip;
  out:
  	consume_skb(cloned_skb);
  }
  EXPORT_SYMBOL(icmpv6_ndo_send);
  #endif

  #endif