/*
   * IPv6 library code, needed by static components when full IPv6 support is
   * not configured or static.  These functions are needed by GSO/GRO implementation.
   */
  #include <linux/export.h>

  #include <net/ip.h>

  #include <net/ipv6.h>
  #include <net/ip6_fib.h>

  #include <net/addrconf.h>

  #include <net/secure_seq.h>

  #include <linux/netfilter.h>

  static u32 __ipv6_select_ident(struct net *net, u32 hashrnd,

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

  {
  	u32 hash, id;
  
  	hash = __ipv6_addr_jhash(dst, hashrnd);
  	hash = __ipv6_addr_jhash(src, hash);

  	hash ^= net_hash_mix(net);

  
  	/* Treat id of 0 as unset and if we get 0 back from ip_idents_reserve,
  	 * set the hight order instead thus minimizing possible future
  	 * collisions.
  	 */
  	id = ip_idents_reserve(hash, 1);
  	if (unlikely(!id))
  		id = 1 << 31;
  
  	return id;
  }

  /* This function exists only for tap drivers that must support broken
   * clients requesting UFO without specifying an IPv6 fragment ID.
   *
   * This is similar to ipv6_select_ident() but we use an independent hash
   * seed to limit information leakage.
   *
   * The network header must be set before calling this.
   */

  __be32 ipv6_proxy_select_ident(struct net *net, struct sk_buff *skb)

  {
  	static u32 ip6_proxy_idents_hashrnd __read_mostly;
  	struct in6_addr buf[2];
  	struct in6_addr *addrs;

  	u32 id;

  
  	addrs = skb_header_pointer(skb,
  				   skb_network_offset(skb) +
  				   offsetof(struct ipv6hdr, saddr),
  				   sizeof(buf), buf);
  	if (!addrs)

  		return 0;

  
  	net_get_random_once(&ip6_proxy_idents_hashrnd,
  			    sizeof(ip6_proxy_idents_hashrnd));

  	id = __ipv6_select_ident(net, ip6_proxy_idents_hashrnd,

  				 &addrs[1], &addrs[0]);

  	return htonl(id);

  }
  EXPORT_SYMBOL_GPL(ipv6_proxy_select_ident);

  __be32 ipv6_select_ident(struct net *net,
  			 const struct in6_addr *daddr,
  			 const struct in6_addr *saddr)

  {
  	static u32 ip6_idents_hashrnd __read_mostly;
  	u32 id;
  
  	net_get_random_once(&ip6_idents_hashrnd, sizeof(ip6_idents_hashrnd));

  	id = __ipv6_select_ident(net, ip6_idents_hashrnd, daddr, saddr);

  	return htonl(id);

  }
  EXPORT_SYMBOL(ipv6_select_ident);

  int ip6_find_1stfragopt(struct sk_buff *skb, u8 **nexthdr)
  {

  	unsigned int offset = sizeof(struct ipv6hdr);

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

  	int found_rhdr = 0;
  	*nexthdr = &ipv6_hdr(skb)->nexthdr;

  	while (offset <= packet_len) {
  		struct ipv6_opt_hdr *exthdr;

  
  		switch (**nexthdr) {
  
  		case NEXTHDR_HOP:
  			break;
  		case NEXTHDR_ROUTING:
  			found_rhdr = 1;
  			break;
  		case NEXTHDR_DEST:
  #if IS_ENABLED(CONFIG_IPV6_MIP6)
  			if (ipv6_find_tlv(skb, offset, IPV6_TLV_HAO) >= 0)
  				break;
  #endif
  			if (found_rhdr)
  				return offset;
  			break;

  		default:

  			return offset;
  		}

  		if (offset + sizeof(struct ipv6_opt_hdr) > packet_len)
  			return -EINVAL;

  		exthdr = (struct ipv6_opt_hdr *)(skb_network_header(skb) +
  						 offset);

  		offset += ipv6_optlen(exthdr);
  		if (offset > IPV6_MAXPLEN)

  			return -EINVAL;

  		*nexthdr = &exthdr->nexthdr;

  	}

  	return -EINVAL;

  }
  EXPORT_SYMBOL(ip6_find_1stfragopt);

  
  #if IS_ENABLED(CONFIG_IPV6)
  int ip6_dst_hoplimit(struct dst_entry *dst)
  {
  	int hoplimit = dst_metric_raw(dst, RTAX_HOPLIMIT);
  	if (hoplimit == 0) {
  		struct net_device *dev = dst->dev;
  		struct inet6_dev *idev;
  
  		rcu_read_lock();
  		idev = __in6_dev_get(dev);
  		if (idev)
  			hoplimit = idev->cnf.hop_limit;
  		else
  			hoplimit = dev_net(dev)->ipv6.devconf_all->hop_limit;
  		rcu_read_unlock();
  	}
  	return hoplimit;
  }
  EXPORT_SYMBOL(ip6_dst_hoplimit);
  #endif

  int __ip6_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)

  {
  	int len;
  
  	len = skb->len - sizeof(struct ipv6hdr);
  	if (len > IPV6_MAXPLEN)
  		len = 0;
  	ipv6_hdr(skb)->payload_len = htons(len);

  	IP6CB(skb)->nhoff = offsetof(struct ipv6hdr, nexthdr);

  	/* if egress device is enslaved to an L3 master device pass the
  	 * skb to its handler for processing
  	 */
  	skb = l3mdev_ip6_out(sk, skb);
  	if (unlikely(!skb))
  		return 0;

  	skb->protocol = htons(ETH_P_IPV6);

  	return nf_hook(NFPROTO_IPV6, NF_INET_LOCAL_OUT,
  		       net, sk, skb, NULL, skb_dst(skb)->dev,

  		       dst_output);

  }
  EXPORT_SYMBOL_GPL(__ip6_local_out);

  int ip6_local_out(struct net *net, struct sock *sk, struct sk_buff *skb)

  {
  	int err;

  	err = __ip6_local_out(net, sk, skb);

  	if (likely(err == 1))

  		err = dst_output(net, sk, skb);

  
  	return err;
  }
  EXPORT_SYMBOL_GPL(ip6_local_out);