/*
   * xfrm4_policy.c
   *
   * Changes:
   *	Kazunori MIYAZAWA @USAGI
   * 	YOSHIFUJI Hideaki @USAGI
   *		Split up af-specific portion
   *
   */
  
  #include <linux/err.h>
  #include <linux/kernel.h>
  #include <linux/inetdevice.h>
  #include <linux/if_tunnel.h>
  #include <net/dst.h>
  #include <net/xfrm.h>
  #include <net/ip.h>
  
  static struct xfrm_policy_afinfo xfrm4_policy_afinfo;
  
  static struct dst_entry *__xfrm4_dst_lookup(struct net *net, struct flowi4 *fl4,
  					    int tos,
  					    const xfrm_address_t *saddr,
  					    const xfrm_address_t *daddr)
  {
  	struct rtable *rt;
  
  	memset(fl4, 0, sizeof(*fl4));
  	fl4->daddr = daddr->a4;
  	fl4->flowi4_tos = tos;
  	if (saddr)
  		fl4->saddr = saddr->a4;
  
  	rt = __ip_route_output_key(net, fl4);
  	if (!IS_ERR(rt))
  		return &rt->dst;
  
  	return ERR_CAST(rt);
  }
  
  static struct dst_entry *xfrm4_dst_lookup(struct net *net, int tos,
  					  const xfrm_address_t *saddr,
  					  const xfrm_address_t *daddr)
  {
  	struct flowi4 fl4;
  
  	return __xfrm4_dst_lookup(net, &fl4, tos, saddr, daddr);
  }
  
  static int xfrm4_get_saddr(struct net *net,
  			   xfrm_address_t *saddr, xfrm_address_t *daddr)
  {
  	struct dst_entry *dst;
  	struct flowi4 fl4;
  
  	dst = __xfrm4_dst_lookup(net, &fl4, 0, NULL, daddr);
  	if (IS_ERR(dst))
  		return -EHOSTUNREACH;
  
  	saddr->a4 = fl4.saddr;
  	dst_release(dst);
  	return 0;
  }
  
  static int xfrm4_get_tos(const struct flowi *fl)
  {
  	return IPTOS_RT_MASK & fl->u.ip4.flowi4_tos; /* Strip ECN bits */
  }
  
  static int xfrm4_init_path(struct xfrm_dst *path, struct dst_entry *dst,
  			   int nfheader_len)
  {
  	return 0;
  }
  
  static int xfrm4_fill_dst(struct xfrm_dst *xdst, struct net_device *dev,
  			  const struct flowi *fl)
  {
  	struct rtable *rt = (struct rtable *)xdst->route;
  	const struct flowi4 *fl4 = &fl->u.ip4;
  
  	xdst->u.rt.rt_iif = fl4->flowi4_iif;
  
  	xdst->u.dst.dev = dev;
  	dev_hold(dev);
  
  	/* Sheit... I remember I did this right. Apparently,
  	 * it was magically lost, so this code needs audit */
  	xdst->u.rt.rt_is_input = rt->rt_is_input;
  	xdst->u.rt.rt_flags = rt->rt_flags & (RTCF_BROADCAST | RTCF_MULTICAST |
  					      RTCF_LOCAL);
  	xdst->u.rt.rt_type = rt->rt_type;
  	xdst->u.rt.rt_gateway = rt->rt_gateway;
  	xdst->u.rt.rt_uses_gateway = rt->rt_uses_gateway;
  	xdst->u.rt.rt_pmtu = rt->rt_pmtu;
  	INIT_LIST_HEAD(&xdst->u.rt.rt_uncached);
  
  	return 0;
  }
  
  static void
  _decode_session4(struct sk_buff *skb, struct flowi *fl, int reverse)
  {
  	const struct iphdr *iph = ip_hdr(skb);
  	u8 *xprth = skb_network_header(skb) + iph->ihl * 4;
  	struct flowi4 *fl4 = &fl->u.ip4;
  	int oif = 0;
  
  	if (skb_dst(skb))
  		oif = skb_dst(skb)->dev->ifindex;
  
  	memset(fl4, 0, sizeof(struct flowi4));
  	fl4->flowi4_mark = skb->mark;
  	fl4->flowi4_oif = reverse ? skb->skb_iif : oif;
  
  	if (!ip_is_fragment(iph)) {
  		switch (iph->protocol) {
  		case IPPROTO_UDP:
  		case IPPROTO_UDPLITE:
  		case IPPROTO_TCP:
  		case IPPROTO_SCTP:
  		case IPPROTO_DCCP:
  			if (xprth + 4 < skb->data ||
  			    pskb_may_pull(skb, xprth + 4 - skb->data)) {
  				__be16 *ports = (__be16 *)xprth;
  
  				fl4->fl4_sport = ports[!!reverse];
  				fl4->fl4_dport = ports[!reverse];
  			}
  			break;
  
  		case IPPROTO_ICMP:
  			if (pskb_may_pull(skb, xprth + 2 - skb->data)) {
  				u8 *icmp = xprth;
  
  				fl4->fl4_icmp_type = icmp[0];
  				fl4->fl4_icmp_code = icmp[1];
  			}
  			break;
  
  		case IPPROTO_ESP:
  			if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
  				__be32 *ehdr = (__be32 *)xprth;
  
  				fl4->fl4_ipsec_spi = ehdr[0];
  			}
  			break;
  
  		case IPPROTO_AH:
  			if (pskb_may_pull(skb, xprth + 8 - skb->data)) {
  				__be32 *ah_hdr = (__be32 *)xprth;
  
  				fl4->fl4_ipsec_spi = ah_hdr[1];
  			}
  			break;
  
  		case IPPROTO_COMP:
  			if (pskb_may_pull(skb, xprth + 4 - skb->data)) {
  				__be16 *ipcomp_hdr = (__be16 *)xprth;
  
  				fl4->fl4_ipsec_spi = htonl(ntohs(ipcomp_hdr[1]));
  			}
  			break;
  
  		case IPPROTO_GRE:
  			if (pskb_may_pull(skb, xprth + 12 - skb->data)) {
  				__be16 *greflags = (__be16 *)xprth;
  				__be32 *gre_hdr = (__be32 *)xprth;
  
  				if (greflags[0] & GRE_KEY) {
  					if (greflags[0] & GRE_CSUM)
  						gre_hdr++;
  					fl4->fl4_gre_key = gre_hdr[1];
  				}
  			}
  			break;
  
  		default:
  			fl4->fl4_ipsec_spi = 0;
  			break;
  		}
  	}
  	fl4->flowi4_proto = iph->protocol;
  	fl4->daddr = reverse ? iph->saddr : iph->daddr;
  	fl4->saddr = reverse ? iph->daddr : iph->saddr;
  	fl4->flowi4_tos = iph->tos;
  }
  
  static inline int xfrm4_garbage_collect(struct dst_ops *ops)
  {
  	struct net *net = container_of(ops, struct net, xfrm.xfrm4_dst_ops);
  
  	xfrm4_policy_afinfo.garbage_collect(net);
  	return (dst_entries_get_slow(ops) > ops->gc_thresh * 2);
  }
  
  static void xfrm4_update_pmtu(struct dst_entry *dst, struct sock *sk,
  			      struct sk_buff *skb, u32 mtu)
  {
  	struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
  	struct dst_entry *path = xdst->route;
  
  	path->ops->update_pmtu(path, sk, skb, mtu);
  }
  
  static void xfrm4_redirect(struct dst_entry *dst, struct sock *sk,
  			   struct sk_buff *skb)
  {
  	struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
  	struct dst_entry *path = xdst->route;
  
  	path->ops->redirect(path, sk, skb);
  }
  
  static void xfrm4_dst_destroy(struct dst_entry *dst)
  {
  	struct xfrm_dst *xdst = (struct xfrm_dst *)dst;
  
  	dst_destroy_metrics_generic(dst);
  
  	xfrm_dst_destroy(xdst);
  }
  
  static void xfrm4_dst_ifdown(struct dst_entry *dst, struct net_device *dev,
  			     int unregister)
  {
  	if (!unregister)
  		return;
  
  	xfrm_dst_ifdown(dst, dev);
  }
  
  static struct dst_ops xfrm4_dst_ops = {
  	.family =		AF_INET,
  	.protocol =		cpu_to_be16(ETH_P_IP),
  	.gc =			xfrm4_garbage_collect,
  	.update_pmtu =		xfrm4_update_pmtu,
  	.redirect =		xfrm4_redirect,
  	.cow_metrics =		dst_cow_metrics_generic,
  	.destroy =		xfrm4_dst_destroy,
  	.ifdown =		xfrm4_dst_ifdown,
  	.local_out =		__ip_local_out,
  	.gc_thresh =		32768,
  };
  
  static struct xfrm_policy_afinfo xfrm4_policy_afinfo = {
  	.family = 		AF_INET,
  	.dst_ops =		&xfrm4_dst_ops,
  	.dst_lookup =		xfrm4_dst_lookup,
  	.get_saddr =		xfrm4_get_saddr,
  	.decode_session =	_decode_session4,
  	.get_tos =		xfrm4_get_tos,
  	.init_path =		xfrm4_init_path,
  	.fill_dst =		xfrm4_fill_dst,
  	.blackhole_route =	ipv4_blackhole_route,
  };
  
  #ifdef CONFIG_SYSCTL
  static struct ctl_table xfrm4_policy_table[] = {
  	{
  		.procname       = "xfrm4_gc_thresh",
  		.data           = &init_net.xfrm.xfrm4_dst_ops.gc_thresh,
  		.maxlen         = sizeof(int),
  		.mode           = 0644,
  		.proc_handler   = proc_dointvec,
  	},
  	{ }
  };
  
  static int __net_init xfrm4_net_init(struct net *net)
  {
  	struct ctl_table *table;
  	struct ctl_table_header *hdr;
  
  	table = xfrm4_policy_table;
  	if (!net_eq(net, &init_net)) {
  		table = kmemdup(table, sizeof(xfrm4_policy_table), GFP_KERNEL);
  		if (!table)
  			goto err_alloc;
  
  		table[0].data = &net->xfrm.xfrm4_dst_ops.gc_thresh;
  	}
  
  	hdr = register_net_sysctl(net, "net/ipv4", table);
  	if (!hdr)
  		goto err_reg;
  
  	net->ipv4.xfrm4_hdr = hdr;
  	return 0;
  
  err_reg:
  	if (!net_eq(net, &init_net))
  		kfree(table);
  err_alloc:
  	return -ENOMEM;
  }
  
  static void __net_exit xfrm4_net_exit(struct net *net)
  {
  	struct ctl_table *table;
  
  	if (net->ipv4.xfrm4_hdr == NULL)
  		return;
  
  	table = net->ipv4.xfrm4_hdr->ctl_table_arg;
  	unregister_net_sysctl_table(net->ipv4.xfrm4_hdr);
  	if (!net_eq(net, &init_net))
  		kfree(table);
  }
  
  static struct pernet_operations __net_initdata xfrm4_net_ops = {
  	.init	= xfrm4_net_init,
  	.exit	= xfrm4_net_exit,
  };
  #endif
  
  static void __init xfrm4_policy_init(void)
  {
  	xfrm_policy_register_afinfo(&xfrm4_policy_afinfo);
  }
  
  void __init xfrm4_init(void)
  {
  	dst_entries_init(&xfrm4_dst_ops);
  
  	xfrm4_state_init();
  	xfrm4_policy_init();
  #ifdef CONFIG_SYSCTL
  	register_pernet_subsys(&xfrm4_net_ops);
  #endif
  }