/* tunnel4.c: Generic IP tunnel transformer.
   *
   * Copyright (C) 2003 David S. Miller (davem@redhat.com)
   */
  
  #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/icmp.h>
  #include <net/ip.h>

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

  static struct xfrm_tunnel __rcu *tunnel4_handlers __read_mostly;
  static struct xfrm_tunnel __rcu *tunnel64_handlers __read_mostly;

  static DEFINE_MUTEX(tunnel4_mutex);

  static inline struct xfrm_tunnel __rcu **fam_handlers(unsigned short family)

  {
  	return (family == AF_INET) ? &tunnel4_handlers : &tunnel64_handlers;
  }

  int xfrm4_tunnel_register(struct xfrm_tunnel *handler, unsigned short family)

  {

  	struct xfrm_tunnel __rcu **pprev;
  	struct xfrm_tunnel *t;

  	int ret = -EEXIST;
  	int priority = handler->priority;
  
  	mutex_lock(&tunnel4_mutex);

  	for (pprev = fam_handlers(family);
  	     (t = rcu_dereference_protected(*pprev,
  			lockdep_is_held(&tunnel4_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(&tunnel4_mutex);
  
  	return ret;
  }

  EXPORT_SYMBOL(xfrm4_tunnel_register);

  int xfrm4_tunnel_deregister(struct xfrm_tunnel *handler, unsigned short family)

  {

  	struct xfrm_tunnel __rcu **pprev;
  	struct xfrm_tunnel *t;

  	int ret = -ENOENT;
  
  	mutex_lock(&tunnel4_mutex);

  	for (pprev = fam_handlers(family);
  	     (t = rcu_dereference_protected(*pprev,
  			lockdep_is_held(&tunnel4_mutex))) != NULL;
  	     pprev = &t->next) {
  		if (t == handler) {

  			*pprev = handler->next;
  			ret = 0;
  			break;
  		}
  	}
  
  	mutex_unlock(&tunnel4_mutex);
  
  	synchronize_net();
  
  	return ret;
  }

  EXPORT_SYMBOL(xfrm4_tunnel_deregister);

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

  static int tunnel4_rcv(struct sk_buff *skb)
  {
  	struct xfrm_tunnel *handler;

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

  	for_each_tunnel_rcu(tunnel4_handlers, handler)

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

  	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
  
  drop:

  	kfree_skb(skb);
  	return 0;
  }

  #if IS_ENABLED(CONFIG_IPV6)

  static int tunnel64_rcv(struct sk_buff *skb)
  {
  	struct xfrm_tunnel *handler;

  	if (!pskb_may_pull(skb, sizeof(struct ipv6hdr)))

  		goto drop;

  	for_each_tunnel_rcu(tunnel64_handlers, handler)

  		if (!handler->handler(skb))
  			return 0;
  
  	icmp_send(skb, ICMP_DEST_UNREACH, ICMP_PORT_UNREACH, 0);
  
  drop:
  	kfree_skb(skb);
  	return 0;
  }
  #endif

  static void tunnel4_err(struct sk_buff *skb, u32 info)
  {
  	struct xfrm_tunnel *handler;

  	for_each_tunnel_rcu(tunnel4_handlers, handler)

  		if (!handler->err_handler(skb, info))
  			break;
  }

  #if IS_ENABLED(CONFIG_IPV6)

  static void tunnel64_err(struct sk_buff *skb, u32 info)
  {
  	struct xfrm_tunnel *handler;

  	for_each_tunnel_rcu(tunnel64_handlers, handler)

  		if (!handler->err_handler(skb, info))
  			break;
  }
  #endif

  static const struct net_protocol tunnel4_protocol = {

  	.handler	=	tunnel4_rcv,
  	.err_handler	=	tunnel4_err,
  	.no_policy	=	1,

  	.netns_ok	=	1,

  };

  #if IS_ENABLED(CONFIG_IPV6)

  static const struct net_protocol tunnel64_protocol = {

  	.handler	=	tunnel64_rcv,

  	.err_handler	=	tunnel64_err,

  	.no_policy	=	1,

  	.netns_ok	=	1,

  };
  #endif

  static int __init tunnel4_init(void)
  {
  	if (inet_add_protocol(&tunnel4_protocol, IPPROTO_IPIP)) {
  		printk(KERN_ERR "tunnel4 init: can't add protocol
  ");
  		return -EAGAIN;
  	}

  #if IS_ENABLED(CONFIG_IPV6)

  	if (inet_add_protocol(&tunnel64_protocol, IPPROTO_IPV6)) {
  		printk(KERN_ERR "tunnel64 init: can't add protocol
  ");
  		inet_del_protocol(&tunnel4_protocol, IPPROTO_IPIP);
  		return -EAGAIN;
  	}
  #endif

  	return 0;
  }
  
  static void __exit tunnel4_fini(void)
  {

  #if IS_ENABLED(CONFIG_IPV6)

  	if (inet_del_protocol(&tunnel64_protocol, IPPROTO_IPV6))
  		printk(KERN_ERR "tunnel64 close: can't remove protocol
  ");
  #endif

  	if (inet_del_protocol(&tunnel4_protocol, IPPROTO_IPIP))
  		printk(KERN_ERR "tunnel4 close: can't remove protocol
  ");
  }
  
  module_init(tunnel4_init);
  module_exit(tunnel4_fini);
  MODULE_LICENSE("GPL");