text: /*
   * IPv6 specific functions of netfilter core
   *
   * Rusty Russell (C) 2000 -- This code is GPL.
   * Patrick McHardy (C) 2006-2012
   */
  #include <linux/kernel.h>
  #include <linux/init.h>
  #include <linux/ipv6.h>
  #include <linux/netfilter.h>
  #include <linux/netfilter_ipv6.h>
  #include <linux/export.h>
  #include <net/addrconf.h>
  #include <net/dst.h>
  #include <net/ipv6.h>
  #include <net/ip6_route.h>
  #include <net/xfrm.h>
  #include <net/ip6_checksum.h>
  #include <net/netfilter/nf_queue.h>
  
  int ip6_route_me_harder(struct net *net, struct sock *sk_partial, struct sk_buff *skb)
  {
  	const struct ipv6hdr *iph = ipv6_hdr(skb);
  	struct sock *sk = sk_to_full_sk(sk_partial);
  	unsigned int hh_len;
  	struct dst_entry *dst;
  	struct flowi6 fl6 = {
  		.flowi6_oif = sk && sk->sk_bound_dev_if ? sk->sk_bound_dev_if :
  			rt6_need_strict(&iph->daddr) ? skb_dst(skb)->dev->ifindex : 0,
  		.flowi6_mark = skb->mark,
  		.flowi6_uid = sock_net_uid(net, sk),
  		.daddr = iph->daddr,
  		.saddr = iph->saddr,
  	};
  	int err;
  
  	dst = ip6_route_output(net, sk, &fl6);
  	err = dst->error;
  	if (err) {
  		IP6_INC_STATS(net, ip6_dst_idev(dst), IPSTATS_MIB_OUTNOROUTES);
  		net_dbg_ratelimited("ip6_route_me_harder: No more route\n");
  		dst_release(dst);
  		return err;
  	}
  
  	/* Drop old route. */
  	skb_dst_drop(skb);
  
  	skb_dst_set(skb, dst);
  
  #ifdef CONFIG_XFRM
  	if (!(IP6CB(skb)->flags & IP6SKB_XFRM_TRANSFORMED) &&
  	    xfrm_decode_session(skb, flowi6_to_flowi(&fl6), AF_INET6) == 0) {
  		skb_dst_set(skb, NULL);
  		dst = xfrm_lookup(net, dst, flowi6_to_flowi(&fl6), sk, 0);
  		if (IS_ERR(dst))
  			return PTR_ERR(dst);
  		skb_dst_set(skb, dst);
  	}
  #endif
  
  	/* Change in oif may mean change in hh_len. */
  	hh_len = skb_dst(skb)->dev->hard_header_len;
  	if (skb_headroom(skb) < hh_len &&
  	    pskb_expand_head(skb, HH_DATA_ALIGN(hh_len - skb_headroom(skb)),
  			     0, GFP_ATOMIC))
  		return -ENOMEM;
  
  	return 0;
  }
  EXPORT_SYMBOL(ip6_route_me_harder);
  
  static int nf_ip6_reroute(struct sk_buff *skb,
  			  const struct nf_queue_entry *entry)
  {
  	struct ip6_rt_info *rt_info = nf_queue_entry_reroute(entry);
  
  	if (entry->state.hook == NF_INET_LOCAL_OUT) {
  		const struct ipv6hdr *iph = ipv6_hdr(skb);
  		if (!ipv6_addr_equal(&iph->daddr, &rt_info->daddr) ||
  		    !ipv6_addr_equal(&iph->saddr, &rt_info->saddr) ||
  		    skb->mark != rt_info->mark)
  			return ip6_route_me_harder(entry->state.net, entry->state.sk, skb);
  	}
  	return 0;
  }
  
  static int nf_ip6_route(struct net *net, struct dst_entry **dst,
  			struct flowi *fl, bool strict)
  {
  	static const struct ipv6_pinfo fake_pinfo;
  	static const struct inet_sock fake_sk = {
  		/* makes ip6_route_output set RT6_LOOKUP_F_IFACE: */
  		.sk.sk_bound_dev_if = 1,
  		.pinet6 = (struct ipv6_pinfo *) &fake_pinfo,
  	};
  	const void *sk = strict ? &fake_sk : NULL;
  	struct dst_entry *result;
  	int err;
  
  	result = ip6_route_output(net, sk, &fl->u.ip6);
  	err = result->error;
  	if (err)
  		dst_release(result);
  	else
  		*dst = result;
  	return err;
  }
  
  __sum16 nf_ip6_checksum(struct sk_buff *skb, unsigned int hook,
  			     unsigned int dataoff, u_int8_t protocol)
  {
  	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
  	__sum16 csum = 0;
  
  	switch (skb->ip_summed) {
  	case CHECKSUM_COMPLETE:
  		if (hook != NF_INET_PRE_ROUTING && hook != NF_INET_LOCAL_IN)
  			break;
  		if (!csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
  				     skb->len - dataoff, protocol,
  				     csum_sub(skb->csum,
  					      skb_checksum(skb, 0,
  							   dataoff, 0)))) {
  			skb->ip_summed = CHECKSUM_UNNECESSARY;
  			break;
  		}
  		/* fall through */
  	case CHECKSUM_NONE:
  		skb->csum = ~csum_unfold(
  				csum_ipv6_magic(&ip6h->saddr, &ip6h->daddr,
  					     skb->len - dataoff,
  					     protocol,
  					     csum_sub(0,
  						      skb_checksum(skb, 0,
  								   dataoff, 0))));
  		csum = __skb_checksum_complete(skb);
  	}
  	return csum;
  }
  EXPORT_SYMBOL(nf_ip6_checksum);
  
  static __sum16 nf_ip6_checksum_partial(struct sk_buff *skb, unsigned int hook,
  				       unsigned int dataoff, unsigned int len,
  				       u_int8_t protocol)
  {
  	const struct ipv6hdr *ip6h = ipv6_hdr(skb);
  	__wsum hsum;
  	__sum16 csum = 0;
  
  	switch (skb->ip_summed) {
  	case CHECKSUM_COMPLETE:
  		if (len == skb->len - dataoff)
  			return nf_ip6_checksum(skb, hook, dataoff, protocol);
  		/* fall through */
  	case CHECKSUM_NONE:
  		hsum = skb_checksum(skb, 0, dataoff, 0);
  		skb->csum = ~csum_unfold(csum_ipv6_magic(&ip6h->saddr,
  							 &ip6h->daddr,
  							 skb->len - dataoff,
  							 protocol,
  							 csum_sub(0, hsum)));
  		skb->ip_summed = CHECKSUM_NONE;
  		return __skb_checksum_complete_head(skb, dataoff + len);
  	}
  	return csum;
  };
  
  static const struct nf_ipv6_ops ipv6ops = {
  	.chk_addr		= ipv6_chk_addr,
  	.route_input    	= ip6_route_input,
  	.fragment		= ip6_fragment,
  	.checksum		= nf_ip6_checksum,
  	.checksum_partial	= nf_ip6_checksum_partial,
  	.route			= nf_ip6_route,
  	.reroute		= nf_ip6_reroute,
  };
  
  int __init ipv6_netfilter_init(void)
  {
  	RCU_INIT_POINTER(nf_ipv6_ops, &ipv6ops);
  	return 0;
  }
  
  /* This can be called from inet6_init() on errors, so it cannot
   * be marked __exit. -DaveM
   */
  void ipv6_netfilter_fini(void)
  {
  	RCU_INIT_POINTER(nf_ipv6_ops, NULL);
  }
  