// 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>

   *
   * Based on net/ipv4/xfrm4_tunnel.c

   */

  #include <linux/module.h>
  #include <linux/xfrm.h>

  #include <linux/slab.h>

  #include <linux/rculist.h>

  #include <net/ip.h>
  #include <net/xfrm.h>
  #include <net/ipv6.h>

  #include <linux/ipv6.h>
  #include <linux/icmpv6.h>

  #include <linux/mutex.h>

  #include <net/netns/generic.h>
  
  #define XFRM6_TUNNEL_SPI_BYADDR_HSIZE 256
  #define XFRM6_TUNNEL_SPI_BYSPI_HSIZE 256
  
  #define XFRM6_TUNNEL_SPI_MIN	1
  #define XFRM6_TUNNEL_SPI_MAX	0xffffffff
  
  struct xfrm6_tunnel_net {
  	struct hlist_head spi_byaddr[XFRM6_TUNNEL_SPI_BYADDR_HSIZE];
  	struct hlist_head spi_byspi[XFRM6_TUNNEL_SPI_BYSPI_HSIZE];
  	u32 spi;
  };

  static unsigned int xfrm6_tunnel_net_id __read_mostly;

  static inline struct xfrm6_tunnel_net *xfrm6_tunnel_pernet(struct net *net)
  {
  	return net_generic(net, xfrm6_tunnel_net_id);
  }

  /*

   * xfrm_tunnel_spi things are for allocating unique id ("spi")

   * per xfrm_address_t.
   */
  struct xfrm6_tunnel_spi {

  	struct hlist_node	list_byaddr;
  	struct hlist_node	list_byspi;
  	xfrm_address_t		addr;
  	u32			spi;

  	refcount_t		refcnt;

  	struct rcu_head		rcu_head;

  };

  static DEFINE_SPINLOCK(xfrm6_tunnel_spi_lock);

  static struct kmem_cache *xfrm6_tunnel_spi_kmem __read_mostly;

  static inline unsigned int xfrm6_tunnel_spi_hash_byaddr(const xfrm_address_t *addr)

  {

  	unsigned int h;

  	h = ipv6_addr_hash((const struct in6_addr *)addr);

  	h ^= h >> 16;
  	h ^= h >> 8;
  	h &= XFRM6_TUNNEL_SPI_BYADDR_HSIZE - 1;

  	return h;
  }

  static inline unsigned int xfrm6_tunnel_spi_hash_byspi(u32 spi)

  {
  	return spi % XFRM6_TUNNEL_SPI_BYSPI_HSIZE;
  }

  static struct xfrm6_tunnel_spi *__xfrm6_tunnel_spi_lookup(struct net *net, const xfrm_address_t *saddr)

  {

  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);

  	struct xfrm6_tunnel_spi *x6spi;

  	hlist_for_each_entry_rcu(x6spi,

  			     &xfrm6_tn->spi_byaddr[xfrm6_tunnel_spi_hash_byaddr(saddr)],

  			     list_byaddr, lockdep_is_held(&xfrm6_tunnel_spi_lock)) {

  		if (xfrm6_addr_equal(&x6spi->addr, saddr))

  			return x6spi;

  	}

  	return NULL;
  }

  __be32 xfrm6_tunnel_spi_lookup(struct net *net, const xfrm_address_t *saddr)

  {
  	struct xfrm6_tunnel_spi *x6spi;
  	u32 spi;

  	rcu_read_lock_bh();

  	x6spi = __xfrm6_tunnel_spi_lookup(net, saddr);

  	spi = x6spi ? x6spi->spi : 0;

  	rcu_read_unlock_bh();

  	return htonl(spi);

  }

  EXPORT_SYMBOL(xfrm6_tunnel_spi_lookup);

  static int __xfrm6_tunnel_spi_check(struct net *net, u32 spi)

  {

  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);

  	struct xfrm6_tunnel_spi *x6spi;
  	int index = xfrm6_tunnel_spi_hash_byspi(spi);

  	hlist_for_each_entry(x6spi,

  			     &xfrm6_tn->spi_byspi[index],

  			     list_byspi) {
  		if (x6spi->spi == spi)
  			return -1;
  	}
  	return index;
  }

  static u32 __xfrm6_tunnel_alloc_spi(struct net *net, xfrm_address_t *saddr)

  {

  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);

  	u32 spi;
  	struct xfrm6_tunnel_spi *x6spi;

  	int index;

  	if (xfrm6_tn->spi < XFRM6_TUNNEL_SPI_MIN ||
  	    xfrm6_tn->spi >= XFRM6_TUNNEL_SPI_MAX)
  		xfrm6_tn->spi = XFRM6_TUNNEL_SPI_MIN;

  	else

  		xfrm6_tn->spi++;

  	for (spi = xfrm6_tn->spi; spi <= XFRM6_TUNNEL_SPI_MAX; spi++) {
  		index = __xfrm6_tunnel_spi_check(net, spi);

  		if (index >= 0)
  			goto alloc_spi;

  
  		if (spi == XFRM6_TUNNEL_SPI_MAX)
  			break;

  	}

  	for (spi = XFRM6_TUNNEL_SPI_MIN; spi < xfrm6_tn->spi; spi++) {
  		index = __xfrm6_tunnel_spi_check(net, spi);

  		if (index >= 0)
  			goto alloc_spi;

  	}
  	spi = 0;
  	goto out;
  alloc_spi:

  	xfrm6_tn->spi = spi;

  	x6spi = kmem_cache_alloc(xfrm6_tunnel_spi_kmem, GFP_ATOMIC);

  	if (!x6spi)

  		goto out;

  	memcpy(&x6spi->addr, saddr, sizeof(x6spi->addr));
  	x6spi->spi = spi;

  	refcount_set(&x6spi->refcnt, 1);

  	hlist_add_head_rcu(&x6spi->list_byspi, &xfrm6_tn->spi_byspi[index]);

  
  	index = xfrm6_tunnel_spi_hash_byaddr(saddr);

  	hlist_add_head_rcu(&x6spi->list_byaddr, &xfrm6_tn->spi_byaddr[index]);

  out:

  	return spi;
  }

  __be32 xfrm6_tunnel_alloc_spi(struct net *net, xfrm_address_t *saddr)

  {
  	struct xfrm6_tunnel_spi *x6spi;
  	u32 spi;

  	spin_lock_bh(&xfrm6_tunnel_spi_lock);

  	x6spi = __xfrm6_tunnel_spi_lookup(net, saddr);

  	if (x6spi) {

  		refcount_inc(&x6spi->refcnt);

  		spi = x6spi->spi;
  	} else

  		spi = __xfrm6_tunnel_alloc_spi(net, saddr);

  	spin_unlock_bh(&xfrm6_tunnel_spi_lock);

  	return htonl(spi);

  }

  EXPORT_SYMBOL(xfrm6_tunnel_alloc_spi);

  static void x6spi_destroy_rcu(struct rcu_head *head)
  {
  	kmem_cache_free(xfrm6_tunnel_spi_kmem,
  			container_of(head, struct xfrm6_tunnel_spi, rcu_head));
  }

  static void xfrm6_tunnel_free_spi(struct net *net, xfrm_address_t *saddr)

  {

  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);

  	struct xfrm6_tunnel_spi *x6spi;

  	struct hlist_node *n;

  	spin_lock_bh(&xfrm6_tunnel_spi_lock);

  	hlist_for_each_entry_safe(x6spi, n,

  				  &xfrm6_tn->spi_byaddr[xfrm6_tunnel_spi_hash_byaddr(saddr)],

  				  list_byaddr)
  	{

  		if (xfrm6_addr_equal(&x6spi->addr, saddr)) {

  			if (refcount_dec_and_test(&x6spi->refcnt)) {

  				hlist_del_rcu(&x6spi->list_byaddr);
  				hlist_del_rcu(&x6spi->list_byspi);
  				call_rcu(&x6spi->rcu_head, x6spi_destroy_rcu);

  				break;
  			}
  		}
  	}

  	spin_unlock_bh(&xfrm6_tunnel_spi_lock);

  }

  static int xfrm6_tunnel_output(struct xfrm_state *x, struct sk_buff *skb)
  {

  	skb_push(skb, -skb_network_offset(skb));

  	return 0;
  }

  static int xfrm6_tunnel_input(struct xfrm_state *x, struct sk_buff *skb)

  {

  	return skb_network_header(skb)[IP6CB(skb)->nhoff];

  }

  static int xfrm6_tunnel_rcv(struct sk_buff *skb)

  {

  	struct net *net = dev_net(skb->dev);

  	const struct ipv6hdr *iph = ipv6_hdr(skb);

  	__be32 spi;

  	spi = xfrm6_tunnel_spi_lookup(net, (const xfrm_address_t *)&iph->saddr);

  	return xfrm6_rcv_spi(skb, IPPROTO_IPV6, spi, NULL);

  }

  static int xfrm6_tunnel_err(struct sk_buff *skb, struct inet6_skb_parm *opt,

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

  {

  	/* xfrm6_tunnel native err handling */
  	switch (type) {

  	case ICMPV6_DEST_UNREACH:

  		switch (code) {

  		case ICMPV6_NOROUTE:

  		case ICMPV6_ADM_PROHIBITED:
  		case ICMPV6_NOT_NEIGHBOUR:
  		case ICMPV6_ADDR_UNREACH:
  		case ICMPV6_PORT_UNREACH:
  		default:

  			break;
  		}
  		break;
  	case ICMPV6_PKT_TOOBIG:

  		break;
  	case ICMPV6_TIME_EXCEED:
  		switch (code) {
  		case ICMPV6_EXC_HOPLIMIT:

  			break;
  		case ICMPV6_EXC_FRAGTIME:

  		default:

  			break;
  		}
  		break;
  	case ICMPV6_PARAMPROB:
  		switch (code) {
  		case ICMPV6_HDR_FIELD: break;
  		case ICMPV6_UNK_NEXTHDR: break;
  		case ICMPV6_UNK_OPTION: break;
  		}
  		break;
  	default:
  		break;
  	}

  
  	return 0;

  }

  static int xfrm6_tunnel_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 ipv6hdr);
  
  	return 0;
  }
  
  static void xfrm6_tunnel_destroy(struct xfrm_state *x)
  {

  	struct net *net = xs_net(x);
  
  	xfrm6_tunnel_free_spi(net, (xfrm_address_t *)&x->props.saddr);

  }

  static const struct xfrm_type xfrm6_tunnel_type = {

  	.description	= "IP6IP6",
  	.owner          = THIS_MODULE,
  	.proto		= IPPROTO_IPV6,
  	.init_state	= xfrm6_tunnel_init_state,
  	.destructor	= xfrm6_tunnel_destroy,
  	.input		= xfrm6_tunnel_input,
  	.output		= xfrm6_tunnel_output,
  };

  static struct xfrm6_tunnel xfrm6_tunnel_handler __read_mostly = {

  	.handler	= xfrm6_tunnel_rcv,

  	.err_handler	= xfrm6_tunnel_err,

  	.priority	= 3,

  };

  static struct xfrm6_tunnel xfrm46_tunnel_handler __read_mostly = {

  	.handler	= xfrm6_tunnel_rcv,
  	.err_handler	= xfrm6_tunnel_err,

  	.priority	= 3,

  };

  static int __net_init xfrm6_tunnel_net_init(struct net *net)
  {
  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);
  	unsigned int i;
  
  	for (i = 0; i < XFRM6_TUNNEL_SPI_BYADDR_HSIZE; i++)
  		INIT_HLIST_HEAD(&xfrm6_tn->spi_byaddr[i]);
  	for (i = 0; i < XFRM6_TUNNEL_SPI_BYSPI_HSIZE; i++)
  		INIT_HLIST_HEAD(&xfrm6_tn->spi_byspi[i]);
  	xfrm6_tn->spi = 0;
  
  	return 0;
  }
  
  static void __net_exit xfrm6_tunnel_net_exit(struct net *net)
  {

  	struct xfrm6_tunnel_net *xfrm6_tn = xfrm6_tunnel_pernet(net);
  	unsigned int i;

  	xfrm_flush_gc();

  	xfrm_state_flush(net, 0, false, true);

  	for (i = 0; i < XFRM6_TUNNEL_SPI_BYADDR_HSIZE; i++)
  		WARN_ON_ONCE(!hlist_empty(&xfrm6_tn->spi_byaddr[i]));
  
  	for (i = 0; i < XFRM6_TUNNEL_SPI_BYSPI_HSIZE; i++)
  		WARN_ON_ONCE(!hlist_empty(&xfrm6_tn->spi_byspi[i]));

  }
  
  static struct pernet_operations xfrm6_tunnel_net_ops = {
  	.init	= xfrm6_tunnel_net_init,
  	.exit	= xfrm6_tunnel_net_exit,
  	.id	= &xfrm6_tunnel_net_id,
  	.size	= sizeof(struct xfrm6_tunnel_net),
  };

  static int __init xfrm6_tunnel_init(void)
  {

  	int rv;

  	xfrm6_tunnel_spi_kmem = kmem_cache_create("xfrm6_tunnel_spi",
  						  sizeof(struct xfrm6_tunnel_spi),
  						  0, SLAB_HWCACHE_ALIGN,
  						  NULL);
  	if (!xfrm6_tunnel_spi_kmem)
  		return -ENOMEM;
  	rv = register_pernet_subsys(&xfrm6_tunnel_net_ops);
  	if (rv < 0)
  		goto out_pernet;

  	rv = xfrm_register_type(&xfrm6_tunnel_type, AF_INET6);
  	if (rv < 0)

  		goto out_type;

  	rv = xfrm6_tunnel_register(&xfrm6_tunnel_handler, AF_INET6);
  	if (rv < 0)

  		goto out_xfrm6;

  	rv = xfrm6_tunnel_register(&xfrm46_tunnel_handler, AF_INET);
  	if (rv < 0)

  		goto out_xfrm46;

  	return 0;

  out_xfrm46:

  	xfrm6_tunnel_deregister(&xfrm6_tunnel_handler, AF_INET6);

  out_xfrm6:

  	xfrm_unregister_type(&xfrm6_tunnel_type, AF_INET6);

  out_type:
  	unregister_pernet_subsys(&xfrm6_tunnel_net_ops);
  out_pernet:
  	kmem_cache_destroy(xfrm6_tunnel_spi_kmem);

  	return rv;

  }
  
  static void __exit xfrm6_tunnel_fini(void)
  {

  	xfrm6_tunnel_deregister(&xfrm46_tunnel_handler, AF_INET);
  	xfrm6_tunnel_deregister(&xfrm6_tunnel_handler, AF_INET6);

  	xfrm_unregister_type(&xfrm6_tunnel_type, AF_INET6);

  	unregister_pernet_subsys(&xfrm6_tunnel_net_ops);

  	/* Someone maybe has gotten the xfrm6_tunnel_spi.
  	 * So need to wait it.
  	 */
  	rcu_barrier();

  	kmem_cache_destroy(xfrm6_tunnel_spi_kmem);

  }
  
  module_init(xfrm6_tunnel_init);
  module_exit(xfrm6_tunnel_fini);
  MODULE_LICENSE("GPL");

  MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_IPV6);