/*
   * Copyright (C)2003-2006 Helsinki University of Technology
   * Copyright (C)2003-2006 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:
   *	Noriaki TAKAMIYA @USAGI
   *	Masahide NAKAMURA @USAGI
   */

  #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt

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

  #include <linux/time.h>

  #include <linux/ipv6.h>

  #include <linux/icmpv6.h>
  #include <net/sock.h>

  #include <net/ipv6.h>

  #include <net/ip6_checksum.h>

  #include <net/rawv6.h>

  #include <net/xfrm.h>
  #include <net/mip6.h>

  static inline unsigned int calc_padlen(unsigned int len, unsigned int n)
  {
  	return (n - len + 16) & 0x7;
  }
  
  static inline void *mip6_padn(__u8 *data, __u8 padlen)
  {
  	if (!data)
  		return NULL;
  	if (padlen == 1) {

  		data[0] = IPV6_TLV_PAD1;

  	} else if (padlen > 1) {

  		data[0] = IPV6_TLV_PADN;

  		data[1] = padlen - 2;
  		if (padlen > 2)
  			memset(data+2, 0, data[1]);
  	}
  	return data + padlen;
  }

  static inline void mip6_param_prob(struct sk_buff *skb, u8 code, int pos)

  {

  	icmpv6_send(skb, ICMPV6_PARAMPROB, code, pos);

  }
  
  static int mip6_mh_len(int type)
  {
  	int len = 0;
  
  	switch (type) {
  	case IP6_MH_TYPE_BRR:
  		len = 0;
  		break;
  	case IP6_MH_TYPE_HOTI:
  	case IP6_MH_TYPE_COTI:
  	case IP6_MH_TYPE_BU:
  	case IP6_MH_TYPE_BACK:
  		len = 1;
  		break;
  	case IP6_MH_TYPE_HOT:
  	case IP6_MH_TYPE_COT:
  	case IP6_MH_TYPE_BERROR:
  		len = 2;
  		break;
  	}
  	return len;
  }

  static int mip6_mh_filter(struct sock *sk, struct sk_buff *skb)

  {

  	struct ip6_mh _hdr;
  	const struct ip6_mh *mh;

  	mh = skb_header_pointer(skb, skb_transport_offset(skb),
  				sizeof(_hdr), &_hdr);
  	if (!mh)

  		return -1;

  	if (((mh->ip6mh_hdrlen + 1) << 3) > skb->len)
  		return -1;

  
  	if (mh->ip6mh_hdrlen < mip6_mh_len(mh->ip6mh_type)) {

  		net_dbg_ratelimited("mip6: MH message too short: %d vs >=%d
  ",
  				    mh->ip6mh_hdrlen,
  				    mip6_mh_len(mh->ip6mh_type));

  		mip6_param_prob(skb, 0, offsetof(struct ip6_mh, ip6mh_hdrlen) +
  				skb_network_header_len(skb));

  		return -1;
  	}

  
  	if (mh->ip6mh_proto != IPPROTO_NONE) {

  		net_dbg_ratelimited("mip6: MH invalid payload proto = %d
  ",
  				    mh->ip6mh_proto);

  		mip6_param_prob(skb, 0, offsetof(struct ip6_mh, ip6mh_proto) +
  				skb_network_header_len(skb));

  		return -1;
  	}
  
  	return 0;
  }

  struct mip6_report_rate_limiter {
  	spinlock_t lock;

  	ktime_t stamp;

  	int iif;
  	struct in6_addr src;
  	struct in6_addr dst;
  };
  
  static struct mip6_report_rate_limiter mip6_report_rl = {

  	.lock = __SPIN_LOCK_UNLOCKED(mip6_report_rl.lock)

  };

  static int mip6_destopt_input(struct xfrm_state *x, struct sk_buff *skb)
  {

  	const struct ipv6hdr *iph = ipv6_hdr(skb);

  	struct ipv6_destopt_hdr *destopt = (struct ipv6_destopt_hdr *)skb->data;

  	int err = destopt->nexthdr;

  	spin_lock(&x->lock);

  	if (!ipv6_addr_equal(&iph->saddr, (struct in6_addr *)x->coaddr) &&
  	    !ipv6_addr_any((struct in6_addr *)x->coaddr))

  		err = -ENOENT;
  	spin_unlock(&x->lock);

  	return err;

  }
  
  /* Destination Option Header is inserted.
   * IP Header's src address is replaced with Home Address Option in
   * Destination Option Header.
   */
  static int mip6_destopt_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ipv6hdr *iph;
  	struct ipv6_destopt_hdr *dstopt;
  	struct ipv6_destopt_hao *hao;
  	u8 nexthdr;
  	int len;

  	skb_push(skb, -skb_network_offset(skb));

  	iph = ipv6_hdr(skb);

  	nexthdr = *skb_mac_header(skb);
  	*skb_mac_header(skb) = IPPROTO_DSTOPTS;

  	dstopt = (struct ipv6_destopt_hdr *)skb_transport_header(skb);

  	dstopt->nexthdr = nexthdr;
  
  	hao = mip6_padn((char *)(dstopt + 1),
  			calc_padlen(sizeof(*dstopt), 6));
  
  	hao->type = IPV6_TLV_HAO;

  	BUILD_BUG_ON(sizeof(*hao) != 18);

  	hao->length = sizeof(*hao) - 2;

  
  	len = ((char *)hao - (char *)dstopt) + sizeof(*hao);
  
  	memcpy(&hao->addr, &iph->saddr, sizeof(hao->addr));

  	spin_lock_bh(&x->lock);

  	memcpy(&iph->saddr, x->coaddr, sizeof(iph->saddr));

  	spin_unlock_bh(&x->lock);

  	WARN_ON(len != x->props.header_len);

  	dstopt->hdrlen = (x->props.header_len >> 3) - 1;
  
  	return 0;
  }

  static inline int mip6_report_rl_allow(ktime_t stamp,

  				       const struct in6_addr *dst,
  				       const struct in6_addr *src, int iif)

  {
  	int allow = 0;
  
  	spin_lock_bh(&mip6_report_rl.lock);

  	if (mip6_report_rl.stamp != stamp ||

  	    mip6_report_rl.iif != iif ||
  	    !ipv6_addr_equal(&mip6_report_rl.src, src) ||
  	    !ipv6_addr_equal(&mip6_report_rl.dst, dst)) {

  		mip6_report_rl.stamp = stamp;

  		mip6_report_rl.iif = iif;

  		mip6_report_rl.src = *src;
  		mip6_report_rl.dst = *dst;

  		allow = 1;
  	}
  	spin_unlock_bh(&mip6_report_rl.lock);
  	return allow;
  }

  static int mip6_destopt_reject(struct xfrm_state *x, struct sk_buff *skb,
  			       const struct flowi *fl)

  {

  	struct net *net = xs_net(x);

  	struct inet6_skb_parm *opt = (struct inet6_skb_parm *)skb->cb;

  	const struct flowi6 *fl6 = &fl->u.ip6;

  	struct ipv6_destopt_hao *hao = NULL;
  	struct xfrm_selector sel;
  	int offset;

  	ktime_t stamp;

  	int err = 0;

  	if (unlikely(fl6->flowi6_proto == IPPROTO_MH &&

  		     fl6->fl6_mh_type <= IP6_MH_TYPE_MAX))

  		goto out;

  	if (likely(opt->dsthao)) {
  		offset = ipv6_find_tlv(skb, opt->dsthao, IPV6_TLV_HAO);
  		if (likely(offset >= 0))

  			hao = (struct ipv6_destopt_hao *)
  					(skb_network_header(skb) + offset);

  	}

  	stamp = skb_get_ktime(skb);

  	if (!mip6_report_rl_allow(stamp, &ipv6_hdr(skb)->daddr,

  				  hao ? &hao->addr : &ipv6_hdr(skb)->saddr,

  				  opt->iif))
  		goto out;
  
  	memset(&sel, 0, sizeof(sel));

  	memcpy(&sel.daddr, (xfrm_address_t *)&ipv6_hdr(skb)->daddr,

  	       sizeof(sel.daddr));
  	sel.prefixlen_d = 128;

  	memcpy(&sel.saddr, (xfrm_address_t *)&ipv6_hdr(skb)->saddr,

  	       sizeof(sel.saddr));
  	sel.prefixlen_s = 128;
  	sel.family = AF_INET6;

  	sel.proto = fl6->flowi6_proto;
  	sel.dport = xfrm_flowi_dport(fl, &fl6->uli);

  	if (sel.dport)

  		sel.dport_mask = htons(~0);

  	sel.sport = xfrm_flowi_sport(fl, &fl6->uli);

  	if (sel.sport)

  		sel.sport_mask = htons(~0);

  	sel.ifindex = fl6->flowi6_oif;

  	err = km_report(net, IPPROTO_DSTOPTS, &sel,

  			(hao ? (xfrm_address_t *)&hao->addr : NULL));
  
   out:
  	return err;
  }

  static int mip6_destopt_offset(struct xfrm_state *x, struct sk_buff *skb,
  			       u8 **nexthdr)
  {
  	u16 offset = sizeof(struct ipv6hdr);

  	struct ipv6_opt_hdr *exthdr =
  				   (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);

  	const unsigned char *nh = skb_network_header(skb);

  	unsigned int packet_len = skb_tail_pointer(skb) -
  		skb_network_header(skb);

  	int found_rhdr = 0;

  	*nexthdr = &ipv6_hdr(skb)->nexthdr;

  
  	while (offset + 1 <= packet_len) {
  
  		switch (**nexthdr) {
  		case NEXTHDR_HOP:
  			break;
  		case NEXTHDR_ROUTING:
  			found_rhdr = 1;
  			break;
  		case NEXTHDR_DEST:
  			/*
  			 * HAO MUST NOT appear more than once.
  			 * XXX: It is better to try to find by the end of
  			 * XXX: packet if HAO exists.
  			 */
  			if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0) {

  				net_dbg_ratelimited("mip6: hao exists already, override
  ");

  				return offset;
  			}
  
  			if (found_rhdr)
  				return offset;
  
  			break;
  		default:
  			return offset;
  		}
  
  		offset += ipv6_optlen(exthdr);
  		*nexthdr = &exthdr->nexthdr;

  		exthdr = (struct ipv6_opt_hdr *)(nh + offset);

  	}
  
  	return offset;
  }
  
  static int mip6_destopt_init_state(struct xfrm_state *x)
  {
  	if (x->id.spi) {

  		pr_info("%s: spi is not 0: %u
  ", __func__, x->id.spi);

  		return -EINVAL;
  	}
  	if (x->props.mode != XFRM_MODE_ROUTEOPTIMIZATION) {

  		pr_info("%s: state's mode is not %u: %u
  ",
  			__func__, XFRM_MODE_ROUTEOPTIMIZATION, x->props.mode);

  		return -EINVAL;
  	}
  
  	x->props.header_len = sizeof(struct ipv6_destopt_hdr) +
  		calc_padlen(sizeof(struct ipv6_destopt_hdr), 6) +
  		sizeof(struct ipv6_destopt_hao);

  	WARN_ON(x->props.header_len != 24);

  
  	return 0;
  }
  
  /*
   * Do nothing about destroying since it has no specific operation for
   * destination options header unlike IPsec protocols.
   */
  static void mip6_destopt_destroy(struct xfrm_state *x)
  {
  }

  static const struct xfrm_type mip6_destopt_type = {

  	.description	= "MIP6DESTOPT",
  	.owner		= THIS_MODULE,

  	.proto		= IPPROTO_DSTOPTS,

  	.flags		= XFRM_TYPE_NON_FRAGMENT | XFRM_TYPE_LOCAL_COADDR,

  	.init_state	= mip6_destopt_init_state,
  	.destructor	= mip6_destopt_destroy,
  	.input		= mip6_destopt_input,
  	.output		= mip6_destopt_output,

  	.reject		= mip6_destopt_reject,

  	.hdr_offset	= mip6_destopt_offset,

  };

  static int mip6_rthdr_input(struct xfrm_state *x, struct sk_buff *skb)
  {

  	const struct ipv6hdr *iph = ipv6_hdr(skb);

  	struct rt2_hdr *rt2 = (struct rt2_hdr *)skb->data;

  	int err = rt2->rt_hdr.nexthdr;

  	spin_lock(&x->lock);

  	if (!ipv6_addr_equal(&iph->daddr, (struct in6_addr *)x->coaddr) &&

  	    !ipv6_addr_any((struct in6_addr *)x->coaddr))

  		err = -ENOENT;
  	spin_unlock(&x->lock);

  	return err;

  }
  
  /* Routing Header type 2 is inserted.
   * IP Header's dst address is replaced with Routing Header's Home Address.
   */
  static int mip6_rthdr_output(struct xfrm_state *x, struct sk_buff *skb)
  {
  	struct ipv6hdr *iph;
  	struct rt2_hdr *rt2;
  	u8 nexthdr;

  	skb_push(skb, -skb_network_offset(skb));

  	iph = ipv6_hdr(skb);

  	nexthdr = *skb_mac_header(skb);
  	*skb_mac_header(skb) = IPPROTO_ROUTING;

  	rt2 = (struct rt2_hdr *)skb_transport_header(skb);

  	rt2->rt_hdr.nexthdr = nexthdr;
  	rt2->rt_hdr.hdrlen = (x->props.header_len >> 3) - 1;
  	rt2->rt_hdr.type = IPV6_SRCRT_TYPE_2;
  	rt2->rt_hdr.segments_left = 1;
  	memset(&rt2->reserved, 0, sizeof(rt2->reserved));

  	WARN_ON(rt2->rt_hdr.hdrlen != 2);

  
  	memcpy(&rt2->addr, &iph->daddr, sizeof(rt2->addr));

  	spin_lock_bh(&x->lock);

  	memcpy(&iph->daddr, x->coaddr, sizeof(iph->daddr));

  	spin_unlock_bh(&x->lock);

  
  	return 0;
  }
  
  static int mip6_rthdr_offset(struct xfrm_state *x, struct sk_buff *skb,
  			     u8 **nexthdr)
  {
  	u16 offset = sizeof(struct ipv6hdr);

  	struct ipv6_opt_hdr *exthdr =
  				   (struct ipv6_opt_hdr *)(ipv6_hdr(skb) + 1);

  	const unsigned char *nh = skb_network_header(skb);

  	unsigned int packet_len = skb_tail_pointer(skb) -
  		skb_network_header(skb);

  	int found_rhdr = 0;

  	*nexthdr = &ipv6_hdr(skb)->nexthdr;

  
  	while (offset + 1 <= packet_len) {
  
  		switch (**nexthdr) {
  		case NEXTHDR_HOP:
  			break;
  		case NEXTHDR_ROUTING:
  			if (offset + 3 <= packet_len) {
  				struct ipv6_rt_hdr *rt;

  				rt = (struct ipv6_rt_hdr *)(nh + offset);

  				if (rt->type != 0)
  					return offset;
  			}
  			found_rhdr = 1;
  			break;
  		case NEXTHDR_DEST:
  			if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
  				return offset;
  
  			if (found_rhdr)
  				return offset;
  
  			break;
  		default:
  			return offset;
  		}
  
  		offset += ipv6_optlen(exthdr);
  		*nexthdr = &exthdr->nexthdr;

  		exthdr = (struct ipv6_opt_hdr *)(nh + offset);

  	}
  
  	return offset;
  }
  
  static int mip6_rthdr_init_state(struct xfrm_state *x)
  {
  	if (x->id.spi) {

  		pr_info("%s: spi is not 0: %u
  ", __func__, x->id.spi);

  		return -EINVAL;
  	}
  	if (x->props.mode != XFRM_MODE_ROUTEOPTIMIZATION) {

  		pr_info("%s: state's mode is not %u: %u
  ",
  			__func__, XFRM_MODE_ROUTEOPTIMIZATION, x->props.mode);

  		return -EINVAL;
  	}
  
  	x->props.header_len = sizeof(struct rt2_hdr);
  
  	return 0;
  }
  
  /*
   * Do nothing about destroying since it has no specific operation for routing
   * header type 2 unlike IPsec protocols.
   */
  static void mip6_rthdr_destroy(struct xfrm_state *x)
  {
  }

  static const struct xfrm_type mip6_rthdr_type = {

  	.description	= "MIP6RT",
  	.owner		= THIS_MODULE,

  	.proto		= IPPROTO_ROUTING,

  	.flags		= XFRM_TYPE_NON_FRAGMENT | XFRM_TYPE_REMOTE_COADDR,

  	.init_state	= mip6_rthdr_init_state,
  	.destructor	= mip6_rthdr_destroy,
  	.input		= mip6_rthdr_input,
  	.output		= mip6_rthdr_output,
  	.hdr_offset	= mip6_rthdr_offset,

  };

  static int __init mip6_init(void)

  {

  	pr_info("Mobile IPv6
  ");

  	if (xfrm_register_type(&mip6_destopt_type, AF_INET6) < 0) {

  		pr_info("%s: can't add xfrm type(destopt)
  ", __func__);

  		goto mip6_destopt_xfrm_fail;
  	}

  	if (xfrm_register_type(&mip6_rthdr_type, AF_INET6) < 0) {

  		pr_info("%s: can't add xfrm type(rthdr)
  ", __func__);

  		goto mip6_rthdr_xfrm_fail;
  	}

  	if (rawv6_mh_filter_register(mip6_mh_filter) < 0) {

  		pr_info("%s: can't add rawv6 mh filter
  ", __func__);

  		goto mip6_rawv6_mh_fail;
  	}

  	return 0;

   mip6_rawv6_mh_fail:
  	xfrm_unregister_type(&mip6_rthdr_type, AF_INET6);

   mip6_rthdr_xfrm_fail:

  	xfrm_unregister_type(&mip6_destopt_type, AF_INET6);
   mip6_destopt_xfrm_fail:

  	return -EAGAIN;
  }

  static void __exit mip6_fini(void)

  {

  	if (rawv6_mh_filter_unregister(mip6_mh_filter) < 0)

  		pr_info("%s: can't remove rawv6 mh filter
  ", __func__);

  	if (xfrm_unregister_type(&mip6_rthdr_type, AF_INET6) < 0)

  		pr_info("%s: can't remove xfrm type(rthdr)
  ", __func__);

  	if (xfrm_unregister_type(&mip6_destopt_type, AF_INET6) < 0)

  		pr_info("%s: can't remove xfrm type(destopt)
  ", __func__);

  }

  
  module_init(mip6_init);
  module_exit(mip6_fini);
  
  MODULE_LICENSE("GPL");

  MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_DSTOPTS);
  MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_ROUTING);