// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * Copyright (C)2003,2004 USAGI/WIDE Project
   *

   * Authors	Mitsuru KANDA  <mk@linux-ipv6.org>

   *		YOSHIFUJI Hideaki <yoshfuji@linux-ipv6.org>

   */

  #define pr_fmt(fmt) "IPv6: " fmt

  #include <linux/icmpv6.h>

  #include <linux/init.h>
  #include <linux/module.h>
  #include <linux/mutex.h>
  #include <linux/netdevice.h>
  #include <linux/skbuff.h>

  #include <linux/slab.h>

  #include <net/ipv6.h>

  #include <net/protocol.h>
  #include <net/xfrm.h>

  static struct xfrm6_tunnel __rcu *tunnel6_handlers __read_mostly;
  static struct xfrm6_tunnel __rcu *tunnel46_handlers __read_mostly;

  static struct xfrm6_tunnel __rcu *tunnelmpls6_handlers __read_mostly;

  static DEFINE_MUTEX(tunnel6_mutex);

  static inline int xfrm6_tunnel_mpls_supported(void)
  {
  	return IS_ENABLED(CONFIG_MPLS);
  }

  int xfrm6_tunnel_register(struct xfrm6_tunnel *handler, unsigned short family)

  {

  	struct xfrm6_tunnel __rcu **pprev;
  	struct xfrm6_tunnel *t;

  	int ret = -EEXIST;
  	int priority = handler->priority;
  
  	mutex_lock(&tunnel6_mutex);

  	switch (family) {
  	case AF_INET6:
  		pprev = &tunnel6_handlers;
  		break;
  	case AF_INET:
  		pprev = &tunnel46_handlers;
  		break;
  	case AF_MPLS:
  		pprev = &tunnelmpls6_handlers;
  		break;
  	default:
  		goto err;
  	}
  
  	for (; (t = rcu_dereference_protected(*pprev,

  			lockdep_is_held(&tunnel6_mutex))) != NULL;
  	     pprev = &t->next) {
  		if (t->priority > priority)

  			break;

  		if (t->priority == priority)

  			goto err;
  	}
  
  	handler->next = *pprev;

  	rcu_assign_pointer(*pprev, handler);

  
  	ret = 0;
  
  err:
  	mutex_unlock(&tunnel6_mutex);
  
  	return ret;
  }

  EXPORT_SYMBOL(xfrm6_tunnel_register);

  int xfrm6_tunnel_deregister(struct xfrm6_tunnel *handler, unsigned short family)

  {

  	struct xfrm6_tunnel __rcu **pprev;
  	struct xfrm6_tunnel *t;

  	int ret = -ENOENT;
  
  	mutex_lock(&tunnel6_mutex);

  	switch (family) {
  	case AF_INET6:
  		pprev = &tunnel6_handlers;
  		break;
  	case AF_INET:
  		pprev = &tunnel46_handlers;
  		break;
  	case AF_MPLS:
  		pprev = &tunnelmpls6_handlers;
  		break;
  	default:
  		goto err;
  	}
  
  	for (; (t = rcu_dereference_protected(*pprev,

  			lockdep_is_held(&tunnel6_mutex))) != NULL;
  	     pprev = &t->next) {
  		if (t == handler) {

  			*pprev = handler->next;
  			ret = 0;
  			break;
  		}
  	}

  err:

  	mutex_unlock(&tunnel6_mutex);
  
  	synchronize_net();
  
  	return ret;
  }

  EXPORT_SYMBOL(xfrm6_tunnel_deregister);

  #define for_each_tunnel_rcu(head, handler)		\
  	for (handler = rcu_dereference(head);		\
  	     handler != NULL;				\
  	     handler = rcu_dereference(handler->next))	\

  static int tunnelmpls6_rcv(struct sk_buff *skb)
  {
  	struct xfrm6_tunnel *handler;
  
  	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
  		goto drop;
  
  	for_each_tunnel_rcu(tunnelmpls6_handlers, handler)
  		if (!handler->handler(skb))
  			return 0;
  
  	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);
  
  drop:
  	kfree_skb(skb);
  	return 0;
  }

  static int tunnel6_rcv(struct sk_buff *skb)

  {

  	struct xfrm6_tunnel *handler;

  	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))
  		goto drop;

  	for_each_tunnel_rcu(tunnel6_handlers, handler)

  		if (!handler->handler(skb))
  			return 0;

  	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);

  
  drop:

  	kfree_skb(skb);
  	return 0;
  }

  #if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
  static int tunnel6_rcv_cb(struct sk_buff *skb, u8 proto, int err)
  {
  	struct xfrm6_tunnel __rcu *head;
  	struct xfrm6_tunnel *handler;
  	int ret;
  
  	head = (proto == IPPROTO_IPV6) ? tunnel6_handlers : tunnel46_handlers;
  
  	for_each_tunnel_rcu(head, handler) {
  		if (handler->cb_handler) {
  			ret = handler->cb_handler(skb, err);
  			if (ret <= 0)
  				return ret;
  		}
  	}
  
  	return 0;
  }
  
  static const struct xfrm_input_afinfo tunnel6_input_afinfo = {
  	.family		=	AF_INET6,
  	.is_ipip	=	true,
  	.callback	=	tunnel6_rcv_cb,
  };
  #endif

  static int tunnel46_rcv(struct sk_buff *skb)

  {

  	struct xfrm6_tunnel *handler;

  	if (!pskb_may_pull(skb, sizeof(struct iphdr)))

  		goto drop;

  	for_each_tunnel_rcu(tunnel46_handlers, handler)

  		if (!handler->handler(skb))
  			return 0;

  	icmpv6_send(skb, ICMPV6_DEST_UNREACH, ICMPV6_PORT_UNREACH, 0);

  
  drop:
  	kfree_skb(skb);
  	return 0;
  }

  static int tunnel6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

  			u8 type, u8 code, int offset, __be32 info)

  {
  	struct xfrm6_tunnel *handler;

  	for_each_tunnel_rcu(tunnel6_handlers, handler)

  		if (!handler->err_handler(skb, opt, type, code, offset, info))

  			return 0;
  
  	return -ENOENT;

  }

  static int tunnel46_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

  			 u8 type, u8 code, int offset, __be32 info)
  {
  	struct xfrm6_tunnel *handler;
  
  	for_each_tunnel_rcu(tunnel46_handlers, handler)
  		if (!handler->err_handler(skb, opt, type, code, offset, info))

  			return 0;
  
  	return -ENOENT;

  }

  static int tunnelmpls6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
  			   u8 type, u8 code, int offset, __be32 info)
  {
  	struct xfrm6_tunnel *handler;
  
  	for_each_tunnel_rcu(tunnelmpls6_handlers, handler)
  		if (!handler->err_handler(skb, opt, type, code, offset, info))
  			return 0;
  
  	return -ENOENT;
  }

  static const struct inet6_protocol tunnel6_protocol = {

  	.handler	= tunnel6_rcv,
  	.err_handler	= tunnel6_err,
  	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
  };

  static const struct inet6_protocol tunnel46_protocol = {

  	.handler	= tunnel46_rcv,

  	.err_handler	= tunnel46_err,

  	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
  };

  static const struct inet6_protocol tunnelmpls6_protocol = {
  	.handler	= tunnelmpls6_rcv,
  	.err_handler	= tunnelmpls6_err,
  	.flags          = INET6_PROTO_NOPOLICY|INET6_PROTO_FINAL,
  };

  static int __init tunnel6_init(void)
  {
  	if (inet6_add_protocol(&tunnel6_protocol, IPPROTO_IPV6)) {

  		pr_err("%s: can't add protocol
  ", __func__);

  		return -EAGAIN;
  	}

  	if (inet6_add_protocol(&tunnel46_protocol, IPPROTO_IPIP)) {

  		pr_err("%s: can't add protocol
  ", __func__);

  		inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6);
  		return -EAGAIN;
  	}

  	if (xfrm6_tunnel_mpls_supported() &&
  	    inet6_add_protocol(&tunnelmpls6_protocol, IPPROTO_MPLS)) {
  		pr_err("%s: can't add protocol
  ", __func__);
  		inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6);
  		inet6_del_protocol(&tunnel46_protocol, IPPROTO_IPIP);
  		return -EAGAIN;
  	}

  #if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
  	if (xfrm_input_register_afinfo(&tunnel6_input_afinfo)) {
  		pr_err("%s: can't add input afinfo
  ", __func__);
  		inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6);
  		inet6_del_protocol(&tunnel46_protocol, IPPROTO_IPIP);
  		if (xfrm6_tunnel_mpls_supported())
  			inet6_del_protocol(&tunnelmpls6_protocol, IPPROTO_MPLS);
  		return -EAGAIN;
  	}
  #endif

  	return 0;
  }
  
  static void __exit tunnel6_fini(void)
  {

  #if IS_ENABLED(CONFIG_INET6_XFRM_TUNNEL)
  	if (xfrm_input_unregister_afinfo(&tunnel6_input_afinfo))
  		pr_err("%s: can't remove input afinfo
  ", __func__);
  #endif

  	if (inet6_del_protocol(&tunnel46_protocol, IPPROTO_IPIP))

  		pr_err("%s: can't remove protocol
  ", __func__);

  	if (inet6_del_protocol(&tunnel6_protocol, IPPROTO_IPV6))

  		pr_err("%s: can't remove protocol
  ", __func__);

  	if (xfrm6_tunnel_mpls_supported() &&
  	    inet6_del_protocol(&tunnelmpls6_protocol, IPPROTO_MPLS))
  		pr_err("%s: can't remove protocol
  ", __func__);

  }
  
  module_init(tunnel6_init);
  module_exit(tunnel6_fini);
  MODULE_LICENSE("GPL");