/* xfrm4_tunnel.c: Generic IP tunnel transformer.
   *
   * Copyright (C) 2003 David S. Miller (davem@redhat.com)
   */
  
  #include <linux/skbuff.h>
  #include <linux/module.h>

  #include <linux/mutex.h>

  #include <net/xfrm.h>
  #include <net/ip.h>
  #include <net/protocol.h>
  
  static int ipip_output(struct xfrm_state *x, struct sk_buff *skb)
  {

  	skb_push(skb, -skb_network_offset(skb));

  	return 0;
  }

  static int ipip_xfrm_rcv(struct xfrm_state *x, struct sk_buff *skb)

  {

  	return ip_hdr(skb)->protocol;

  }

  static int ipip_init_state(struct xfrm_state *x)

  {

  	if (x->props.mode != XFRM_MODE_TUNNEL)

  		return -EINVAL;
  
  	if (x->encap)
  		return -EINVAL;
  
  	x->props.header_len = sizeof(struct iphdr);
  
  	return 0;
  }
  
  static void ipip_destroy(struct xfrm_state *x)
  {
  }

  static const struct xfrm_type ipip_type = {

  	.description	= "IPIP",
  	.owner		= THIS_MODULE,
  	.proto	     	= IPPROTO_IPIP,
  	.init_state	= ipip_init_state,
  	.destructor	= ipip_destroy,
  	.input		= ipip_xfrm_rcv,
  	.output		= ipip_output
  };

  static int xfrm_tunnel_rcv(struct sk_buff *skb)
  {

  	return xfrm4_rcv_spi(skb, IPPROTO_IPIP, ip_hdr(skb)->saddr);

  }

  static int xfrm_tunnel_err(struct sk_buff *skb, u32 info)
  {
  	return -ENOENT;
  }

  static struct xfrm_tunnel xfrm_tunnel_handler __read_mostly = {

  	.handler	=	xfrm_tunnel_rcv,

  	.err_handler	=	xfrm_tunnel_err,
  	.priority	=	2,

  };

  #if IS_ENABLED(CONFIG_IPV6)

  static struct xfrm_tunnel xfrm64_tunnel_handler __read_mostly = {

  	.handler	=	xfrm_tunnel_rcv,

  	.err_handler	=	xfrm_tunnel_err,
  	.priority	=	2,
  };
  #endif

  static int __init ipip_init(void)
  {
  	if (xfrm_register_type(&ipip_type, AF_INET) < 0) {
  		printk(KERN_INFO "ipip init: can't add xfrm type
  ");
  		return -EAGAIN;
  	}

  
  	if (xfrm4_tunnel_register(&xfrm_tunnel_handler, AF_INET)) {
  		printk(KERN_INFO "ipip init: can't add xfrm handler for AF_INET
  ");
  		xfrm_unregister_type(&ipip_type, AF_INET);
  		return -EAGAIN;
  	}

  #if IS_ENABLED(CONFIG_IPV6)

  	if (xfrm4_tunnel_register(&xfrm64_tunnel_handler, AF_INET6)) {
  		printk(KERN_INFO "ipip init: can't add xfrm handler for AF_INET6
  ");
  		xfrm4_tunnel_deregister(&xfrm_tunnel_handler, AF_INET);

  		xfrm_unregister_type(&ipip_type, AF_INET);
  		return -EAGAIN;
  	}

  #endif

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

  #if IS_ENABLED(CONFIG_IPV6)

  	if (xfrm4_tunnel_deregister(&xfrm64_tunnel_handler, AF_INET6))
  		printk(KERN_INFO "ipip close: can't remove xfrm handler for AF_INET6
  ");
  #endif
  	if (xfrm4_tunnel_deregister(&xfrm_tunnel_handler, AF_INET))
  		printk(KERN_INFO "ipip close: can't remove xfrm handler for AF_INET
  ");

  	if (xfrm_unregister_type(&ipip_type, AF_INET) < 0)
  		printk(KERN_INFO "ipip close: can't remove xfrm type
  ");
  }
  
  module_init(ipip_init);
  module_exit(ipip_fini);
  MODULE_LICENSE("GPL");

  MODULE_ALIAS_XFRM_TYPE(AF_INET, XFRM_PROTO_IPIP);