/*
 * Copyright (C)2003,2004 USAGI/WIDE Project
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, see <http://www.gnu.org/licenses/>.
 *
 * 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 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;
	atomic_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) {
		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;
	atomic_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) {
		atomic_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 (atomic_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	= 2,
};

static struct xfrm6_tunnel xfrm46_tunnel_handler __read_mostly = {
	.handler	= xfrm6_tunnel_rcv,
	.err_handler	= xfrm6_tunnel_err,
	.priority	= 2,
};

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)
{
}

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);