/*
   * IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173
   *
   * Copyright (C)2003 USAGI/WIDE Project
   *
   * Author	Mitsuru KANDA  <mk@linux-ipv6.org>
   *
   * 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/>.
   */
  /*
   * [Memo]
   *
   * Outbound:
   *  The compression of IP datagram MUST be done before AH/ESP processing,
   *  fragmentation, and the addition of Hop-by-Hop/Routing header.
   *
   * Inbound:
   *  The decompression of IP datagram MUST be done after the reassembly,
   *  AH/ESP processing.
   */
  
  #define pr_fmt(fmt) "IPv6: " fmt
  
  #include <linux/module.h>
  #include <net/ip.h>
  #include <net/xfrm.h>
  #include <net/ipcomp.h>
  #include <linux/crypto.h>
  #include <linux/err.h>
  #include <linux/pfkeyv2.h>
  #include <linux/random.h>
  #include <linux/percpu.h>
  #include <linux/smp.h>
  #include <linux/list.h>
  #include <linux/vmalloc.h>
  #include <linux/rtnetlink.h>
  #include <net/ip6_route.h>
  #include <net/icmp.h>
  #include <net/ipv6.h>
  #include <net/protocol.h>
  #include <linux/ipv6.h>
  #include <linux/icmpv6.h>
  #include <linux/mutex.h>
  
  static void ipcomp6_err(struct sk_buff *skb, struct inet6_skb_parm *opt,
  				u8 type, u8 code, int offset, __be32 info)
  {
  	struct net *net = dev_net(skb->dev);
  	__be32 spi;
  	const struct ipv6hdr *iph = (const struct ipv6hdr *)skb->data;
  	struct ip_comp_hdr *ipcomph =
  		(struct ip_comp_hdr *)(skb->data + offset);
  	struct xfrm_state *x;
  
  	if (type != ICMPV6_PKT_TOOBIG &&
  	    type != NDISC_REDIRECT)
  		return;
  
  	spi = htonl(ntohs(ipcomph->cpi));
  	x = xfrm_state_lookup(net, skb->mark, (const xfrm_address_t *)&iph->daddr,
  			      spi, IPPROTO_COMP, AF_INET6);
  	if (!x)
  		return;
  
  	if (type == NDISC_REDIRECT)
  		ip6_redirect(skb, net, skb->dev->ifindex, 0);
  	else
  		ip6_update_pmtu(skb, net, info, 0, 0);
  	xfrm_state_put(x);
  }
  
  static struct xfrm_state *ipcomp6_tunnel_create(struct xfrm_state *x)
  {
  	struct net *net = xs_net(x);
  	struct xfrm_state *t = NULL;
  
  	t = xfrm_state_alloc(net);
  	if (!t)
  		goto out;
  
  	t->id.proto = IPPROTO_IPV6;
  	t->id.spi = xfrm6_tunnel_alloc_spi(net, (xfrm_address_t *)&x->props.saddr);
  	if (!t->id.spi)
  		goto error;
  
  	memcpy(t->id.daddr.a6, x->id.daddr.a6, sizeof(struct in6_addr));
  	memcpy(&t->sel, &x->sel, sizeof(t->sel));
  	t->props.family = AF_INET6;
  	t->props.mode = x->props.mode;
  	memcpy(t->props.saddr.a6, x->props.saddr.a6, sizeof(struct in6_addr));
  	memcpy(&t->mark, &x->mark, sizeof(t->mark));
  
  	if (xfrm_init_state(t))
  		goto error;
  
  	atomic_set(&t->tunnel_users, 1);
  
  out:
  	return t;
  
  error:
  	t->km.state = XFRM_STATE_DEAD;
  	xfrm_state_put(t);
  	t = NULL;
  	goto out;
  }
  
  static int ipcomp6_tunnel_attach(struct xfrm_state *x)
  {
  	struct net *net = xs_net(x);
  	int err = 0;
  	struct xfrm_state *t = NULL;
  	__be32 spi;
  	u32 mark = x->mark.m & x->mark.v;
  
  	spi = xfrm6_tunnel_spi_lookup(net, (xfrm_address_t *)&x->props.saddr);
  	if (spi)
  		t = xfrm_state_lookup(net, mark, (xfrm_address_t *)&x->id.daddr,
  					      spi, IPPROTO_IPV6, AF_INET6);
  	if (!t) {
  		t = ipcomp6_tunnel_create(x);
  		if (!t) {
  			err = -EINVAL;
  			goto out;
  		}
  		xfrm_state_insert(t);
  		xfrm_state_hold(t);
  	}
  	x->tunnel = t;
  	atomic_inc(&t->tunnel_users);
  
  out:
  	return err;
  }
  
  static int ipcomp6_init_state(struct xfrm_state *x)
  {
  	int err = -EINVAL;
  
  	x->props.header_len = 0;
  	switch (x->props.mode) {
  	case XFRM_MODE_TRANSPORT:
  		break;
  	case XFRM_MODE_TUNNEL:
  		x->props.header_len += sizeof(struct ipv6hdr);
  		break;
  	default:
  		goto out;
  	}
  
  	err = ipcomp_init_state(x);
  	if (err)
  		goto out;
  
  	if (x->props.mode == XFRM_MODE_TUNNEL) {
  		err = ipcomp6_tunnel_attach(x);
  		if (err)
  			goto out;
  	}
  
  	err = 0;
  out:
  	return err;
  }
  
  static const struct xfrm_type ipcomp6_type =
  {
  	.description	= "IPCOMP6",
  	.owner		= THIS_MODULE,
  	.proto		= IPPROTO_COMP,
  	.init_state	= ipcomp6_init_state,
  	.destructor	= ipcomp_destroy,
  	.input		= ipcomp_input,
  	.output		= ipcomp_output,
  	.hdr_offset	= xfrm6_find_1stfragopt,
  };
  
  static const struct inet6_protocol ipcomp6_protocol =
  {
  	.handler	= xfrm6_rcv,
  	.err_handler	= ipcomp6_err,
  	.flags		= INET6_PROTO_NOPOLICY,
  };
  
  static int __init ipcomp6_init(void)
  {
  	if (xfrm_register_type(&ipcomp6_type, AF_INET6) < 0) {
  		pr_info("%s: can't add xfrm type
  ", __func__);
  		return -EAGAIN;
  	}
  	if (inet6_add_protocol(&ipcomp6_protocol, IPPROTO_COMP) < 0) {
  		pr_info("%s: can't add protocol
  ", __func__);
  		xfrm_unregister_type(&ipcomp6_type, AF_INET6);
  		return -EAGAIN;
  	}
  	return 0;
  }
  
  static void __exit ipcomp6_fini(void)
  {
  	if (inet6_del_protocol(&ipcomp6_protocol, IPPROTO_COMP) < 0)
  		pr_info("%s: can't remove protocol
  ", __func__);
  	if (xfrm_unregister_type(&ipcomp6_type, AF_INET6) < 0)
  		pr_info("%s: can't remove xfrm type
  ", __func__);
  }
  
  module_init(ipcomp6_init);
  module_exit(ipcomp6_fini);
  MODULE_LICENSE("GPL");
  MODULE_DESCRIPTION("IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173");
  MODULE_AUTHOR("Mitsuru KANDA <mk@linux-ipv6.org>");
  
  MODULE_ALIAS_XFRM_TYPE(AF_INET6, XFRM_PROTO_COMP);