// SPDX-License-Identifier: GPL-2.0-or-later

  /*
   * IP Payload Compression Protocol (IPComp) for IPv6 - RFC3173
   *
   * Copyright (C)2003 USAGI/WIDE Project
   *
   * Author	Mitsuru KANDA  <mk@linux-ipv6.org>

   */

  /*

   * [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 int 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 0;

  	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 0;

  	if (type == NDISC_REDIRECT)

  		ip6_redirect(skb, net, skb->dev->ifindex, 0,
  			     sock_net_uid(net, NULL));

  	else

  		ip6_update_pmtu(skb, net, info, 0, 0, sock_net_uid(net, NULL));

  	xfrm_state_put(x);

  
  	return 0;

  }
  
  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));

  	t->if_id = x->if_id;

  	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 int ipcomp6_rcv_cb(struct sk_buff *skb, int err)
  {
  	return 0;
  }

  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 struct xfrm6_protocol ipcomp6_protocol = {

  	.handler	= xfrm6_rcv,

  	.input_handler	= xfrm_input,

  	.cb_handler	= ipcomp6_rcv_cb,

  	.err_handler	= ipcomp6_err,

  	.priority	= 0,

  };
  
  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 (xfrm6_protocol_register(&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 (xfrm6_protocol_deregister(&ipcomp6_protocol, IPPROTO_COMP) < 0)

  		pr_info("%s: can't remove protocol
  ", __func__);

  	xfrm_unregister_type(&ipcomp6_type, AF_INET6);

  }
  
  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);